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Outdoor Free Flight Forum => Free Flight Scale => Topic started by: Don McLellan on March 13, 2017, 09:25:19 PM



Title: B-17 F
Post by: Don McLellan on March 13, 2017, 09:25:19 PM
Decided to take a swing at building a 26" span B-17 F.  Once again this will take some time because I'm making it up as I go along.

Using my craft cutter I cut out the fuse formers.  They are two laminations of approx .040" thick balsa, glued slightly cross grain.  First pic is of some of the formers. 

I initially cut the fuse longerons with the craft cutter.  Because it will only cut a max length of 12", I had to glue these together to get the length of the fuse.  Predictably I ended up some things in the wrong place so then cut a set of longerons by hand and was much happier.  Next pic shows the side longerons with some temp transverse 1/8 square glued to the longerons.  The side longerons are notched, as are the formers, so some wriggling was required to get things located and glued.


Title: Re: B-17 F
Post by: Don McLellan on March 13, 2017, 09:27:44 PM
This is where I am right now.  The fuse is sorta done, and am about to start on the wings, nacelles etc.


Title: Re: B-17 F
Post by: skyraider on March 13, 2017, 10:46:32 PM
Looking sharp there Don!  Excellent subject too.

Skyraider


Title: Re: B-17 F
Post by: Ray_K on March 13, 2017, 11:03:00 PM
3-13-2017

I love it Don, looking fantastic, a craft cutter seems the way to go instead of laser cutting, I have been looking at the scan and cut craft cutters and I may just have to get myself one, what brand would you recommend?
Is the B-17 going to be rubber powered? Can a craft cutter also write numbers on each former? Sorry but so many questions.

Cheers, Ray K.  :)


Title: Re: B-17 F
Post by: OZPAF on March 14, 2017, 12:43:50 AM
That's an interesting challenge Don. The B17 seems a good choice with it's large wing and tail areas.
Very nice so far.
John


Title: Re: B-17 F
Post by: Sky9pilot on March 14, 2017, 12:53:12 AM
Outstanding Don!!!
You gonna run the rubber through the fuselage and prop on the nose?
Tom


Title: Re: B-17 F
Post by: p40qmilj on March 14, 2017, 06:24:28 AM
 ;D don impressive  :o what's a craft cutter and how does it work? all i use is razor blades

jim ;D


Title: Re: B-17 F
Post by: Don McLellan on March 14, 2017, 12:47:11 PM
Thank you for the comments and interest.  Ray, Jim, I'm using a Silhouette Portrait, the same as Tony Ross.  It will cut (with multiple passes) wood up to .040" thick with the blade provided, and will cut thicker with after market blades.  As mentioned, one drawback is the max length that can be cut is 12".  The next model up, the Cameo, will cut 12" wide by 10 ft long.

Tom, my current thinking (or lack of) is to use four rubber powered props for my B-17.  I think I can get a motor length of 6" for the inboard props, and approx 5" for the outboard.  As per usual, a flight of 10 ft or 10 secs would be classed as a wild success.

D


Title: Re: B-17 F
Post by: tom arnold on March 14, 2017, 03:09:19 PM
Actually, Don, you may surprise yourself. A multi-engine in the small sizes can be made to fly quite well. Dave Haught at WESTFAC 5 flew a B-24 of about 25" span as well as a Lancaster. Both flew in the 40 second range to the amazement of us all. He did approach his build as if it would be an indoor model with regards to wood and structure----he mentioned he really had to get away from his "outdoor" thinking in the build. And it worked out well. You can see a couple of photos of his planes on the WESTFAC website:   www.westernfac.com
Go to the photo gallery, click on WESTFAC 5 and you'll see his planes in the top row and down towards the right hand corner. Sorry I cannot find the close-up photos I had taken.


Title: Re: B-17 F
Post by: Don McLellan on March 14, 2017, 05:22:03 PM
Hi Tom,

Thank you very much for the link.  Dave Haught's B-17 shown in issue 109 of INAV has been a great inspiration.  Plus I freely admit that I get all weak kneed every time I see a B-17. 

Interesting that the article says Dave built three B-17s at the same time in order to minimize/optimize the weight.  I plan to build one to begin with, with maybe a second if I have any kind of success (10 feet, 10 sec etc).  [Also haven't forgotten about my Me410; just still struggling mightily with the canopy].

Don


Title: Re: B-17 F
Post by: Ray_K on March 14, 2017, 05:46:40 PM
3-14-2017

Don, thanks for the info, I was planning on doing a rubber powered B-17 from the Joe Ott plan, 20" wing span and I was planning on running all 4 props on a pulley belt system with the main drive pulley in the fuselage so that I can run the rubber motor in the fuselage. Just a thought.  ;)

Cheers, Ray K.


Title: Re: B-17 F
Post by: tross on March 15, 2017, 10:20:34 AM
Hi Don,
It really looks the part already.
Mean. 8)
Actually, Don, you may surprise yourself.
I'm not buying it either Tom.
I was thinking you may need a bigger field Don. :o :o :o

Tony


Title: Re: B-17 F
Post by: strat-o on March 15, 2017, 11:29:32 AM
Ray's ideas on pulleys is intriguing.  They would give you plenty of flexibility in terms of direction of rotation of individual props.  If you were really masochistic you could even build an Avro Shackleton!


Title: Re: B-17 F
Post by: skyraider on March 15, 2017, 11:48:18 AM
[quote I was planning on running all 4 props on a pulley belt system with the main drive pulley in the fuselage so that I can run the rubber motor in the fuselage][/quote]

Years ago, Daniel Christopher of Chris-Prod Industries used this system on his multi-engine profile models. From what I see on
his plans is that this is a workable system and would work very well with Don's B-17. Might be worth exploring.

Skyraider


Title: Re: B-17 F
Post by: PB_guy on March 15, 2017, 12:24:51 PM
Interesting concept. I have thought about using some small gears and miniature chains that someone posted a while ago. It would avoid slippage problems. Of course, if it were available, small bevel gears and drive shafts would also work.
ian


Title: Re: B-17 F
Post by: ZK-AUD on March 15, 2017, 01:06:50 PM
Check out HJ Towners B-17G plan on outerzone - well worth a look to see how his diagonal rubber concept might apply.  I also like the idea of a thing flexi-drive system that might allow use of the fuselage for the rubber


Title: Re: B-17 F
Post by: Don McLellan on March 15, 2017, 04:32:01 PM
I looked for a long time at the Towner plan.  It's quite neat, but in the end decided on separate rubber motors for each prop. 

Some work on one wing and inboard nacelle.  Weight of wing and nacelle is 5 grms; fuse shown above is 7 grms.


Title: Re: B-17 F
Post by: Art356A on March 15, 2017, 05:12:38 PM
FWIW, the weight of a 40 tooth sprocket is 1.925gm, diameter 1.6. A 16 tooth is .683gm, .65d. A foot of chain is 1.847gms. There's a table of specs on the Servo City site, but they don't give weights. You can probably run a cross-chain to achieve opposite rotation using a scrap of celluloid at the "X" to keep the links apart, but I don't think torque is as critical a factor on a 4-motor model as a single.

Any thoughts about accessibility to the drive train on any of these configurations?

art.


Title: Re: B-17 F
Post by: Crabby on March 15, 2017, 06:01:37 PM
I like to think of it as 4 pistachios on a wing. Might be a good idea to think about motor sticks so you can wind outside the plane, then slide 'em in having a slot in the rear someplace deep. I don't think she will want for power. Are you going with countra-rotators? Great building again Don!


Title: Re: B-17 F
Post by: strat-o on March 15, 2017, 06:26:10 PM
Quote
Any thoughts about accessibility to the drive train on any of these configurations?

I had some thoughts on a bevel-gear style drive train where you house the drive train in a box spar.  The box spar would be flush with the lower surface of the wing.  You could then build the gear boxes into the box spar but also use the spar as part of the gear boxes. Then bottom of the spar is open (with cross pieces) and covered with tissue.  The top could be open with cross pieces as well.  Would work well with a B-17 because the wing has a fair amount of thickness.

The idea is you could remove tissue for access to the drive-train if needed.  The lower part of the nacelles could also be made removable to facilitate access to the gear boxes.

Marlin


Title: Re: B-17 F
Post by: tom arnold on March 15, 2017, 06:57:32 PM
Since we are destroying poor Don's thread here, I must tell you about my attempts at gears and such. I got a bug up my tail to build an XB-35 complete with 4 rubber powered props thrashing and thrusting many years ago. It was about 48" span and had props about 6" diameter. I planned on running the rubber motor the span of the wings at the thick part--about the 33% chord area---and turning the torque through a series of bevel gears all the way around corners and out to the props. I plotted and planned and found exactly the bevel gears I envisioned from the model train community. They were these really slick and smooth running small little devices that went into electric train engines to transfer torque around a 90 degree corner to the engine drive wheels. They were made of a bullet proof Delrin type of plastic and each cost a small king's ransom. But, boy, would a flying XB-35 knock the socks off the peanut gallery at the flying field!

I had to get 8 of them to turn all the corners and spent weeks and weeks building up the frame work, setting the gears in place, attaching shafts (nothing fit), figuring out how to wind the 2 motors and change the 2 motors, figuring out tiny free wheelers on pusher props, and so on. Everything was new and the first time around. Finally, the big day came and the huge framework was on my bench and needing nothing but to be covered in tissue.

Time for a test run---THE Test Run. I had no idea about the size of motor to use but trying to twirl the first shaft with my fingers strangely needed more power than I would have thought to get the props even gently spinning. I wisely decided to load a motor in I knew was too powerful but gently make my way up in winds until I started getting a "flyable" blast of air from my 4 mighty peanut size propellers. The first couple of windings were wimpy and not much happened. Increasing winds and power just was not hacking it. Finally, in desperation, I cranked in the winds. With great hope and more than a little sinking feeling, I pulled the pin release. The long high-pitched scream that came out my shop is still talked about in that neighborhood today. Animals froze at the sound and then howled in concert with it. I could not stop that demon cry as the whole framework vibrated in my hands and threatened to explode in hideous finale to the unearthly sound. Finally after long, long, hours (it seemed) it shuddered and stopped. The neighborhood dogs went quiet one by one and I sat there in shock for a while.

It turned out that the needed torque to turn the props was far more than my bevel gears could take and all 8 of them stripped simultaneously to scream to the skies that "it ain't working". When the torque disappeared, the gears all popped back into mesh and looked back at me innocently like  nothing happened. Dragging my sorry butt to the next club meeting, I related my woes to Walt Mooney and he said that was the best thing that could have ever happened to me. When I asked why, he said because you now know beyond a shadow of a doubt that it is a dead end and you quit working on it and went on to some new success. He explained that a bevel gear only transfers about 85-90% of the power put in so that meant even if they had all hung together, I would get less than half of the torque of my motor ever coming out at the props. It was destined to be a great big dog from the beginning.

With that, I decided to stick with direct drives forever.  


Title: Re: B-17 F
Post by: tross on March 15, 2017, 07:53:29 PM
I had a sneak peek at the drawing previously, and it's amazing.
Can't wait too see it come to life Don.

Tony

PS...love hearing those side stories Tom.....


Title: Re: B-17 F
Post by: PB_guy on March 15, 2017, 08:23:57 PM
Yes, Tony. Impressive story. Thanks for the reality check. I did know about the 10 to 15% loss per gearing level. I still like the idea of transferring power in a single plane through belts or chains, knowing that the rubber power will have to be increased, probably by a power of 2, or even 4 in the end to overcome friction losses.
ian


Title: Re: B-17 F
Post by: tom arnold on March 15, 2017, 10:35:29 PM
After all that above horror story, Walt did say that pulleys and belts were MUCH more efficient. There maybe hope yet for us gadgeteers!


Title: Re: B-17 F
Post by: OZPAF on March 16, 2017, 12:55:34 AM
What a great story Tom. Pity it didn't make it to the flying field though. What a sight it would have been with all the dogs in the neighbourhood following it howling away :) An airborne Pied piper :D
John


Title: Re: B-17 F
Post by: Bredehoft on March 16, 2017, 06:47:51 AM
Back in 1966, there was an article by Dennis Norman on how he built and flew a DeHavilland Mosquito.  It was smallish and the secret was a belt drive.  It is worth a read if you are interested in belt drives.  Here is a link to an online copy of the article and plan.

https://volarlibremente.wordpress.com/2011/01/05/mosquito-iv/ (https://volarlibremente.wordpress.com/2011/01/05/mosquito-iv/)

--george


Title: Re: B-17 F
Post by: Don McLellan on March 16, 2017, 04:12:08 PM
Great story Tom!!  Love to hear stuff like that.

Crabby, I plan to have two CW and two CCW props, and will wind them from the wing TE.  I'm a little worried about the props smacking into each other, so most likely will glue the nose buttons to the front of the nacelles.

Added the second nacelle to the wing and couldn't resist pinning everything together.


Title: Re: B-17 F
Post by: Sky9pilot on March 16, 2017, 09:13:06 PM
I love the B-17 Don...coming along nicely. 
Tom...great story and didn't someone build the Northrup flying wing XB-35 or the YB-49?  I'd love to see one of these flying.
Sky9pilot


Title: Re: B-17 F
Post by: tom arnold on March 16, 2017, 10:50:12 PM
Yes, it was a much younger (weren't we all) Vance Gilbert and he powered it with a single big prop at the tail end of that center pod at the back. The motor ran the length of the root rib to the nose. It flew fantastic---really cool turning and dipping in the air--- and he had a construction article in Max Fax, the newsletter of the Maxecuters. I saw it fly a couple of times and in talking to him, he said the only hard part was the launching with no fuselage to grab.


Title: Re: B-17 F
Post by: Ray_K on March 17, 2017, 09:51:08 PM
3-17-2017

Wow, I seemed to have started something with the idea of using a pulley and belt drive system, the system has merit, I had built a Wright flyer using a pulley and belt system as a test and it worked quite well, for the B-17 it would be easy, the pulleys for the props would go directly behind the props not in the engine nacelles, and a double pulley would be within the fuselage to drive the props, only an access hatch would be required to get to the pulley within the fuselage to change belts if needed. FYI.

Cheers, Ray K. 


Title: Re: B-17 F
Post by: ZK-AUD on March 18, 2017, 12:37:11 AM
I'm starting to like this train of thought - what if the main drive double pulley in side the fuselage was actually a tube (with the grooved or notched section glued around it) rotating in a cradle which allowed the rubber to go the full length of the fuselage and through the tube.  After winding the nose plug would be attached and engage in the front of the tube.  The scale nose would be detachable to allow access for this.


Title: Re: B-17 F
Post by: strat-o on March 18, 2017, 10:44:56 AM
 I see what you are saying.  You actually wouldn't need a full length tube, just have it run from nose to mid-wing chord.  That should reduce complexity somewhat and reduce weight near the tail.


Title: Re: B-17 F
Post by: rgroener on March 21, 2017, 05:35:24 AM
Don, so cool!
That's a terrific project!

Roman


Title: Re: B-17 F
Post by: Prosper on March 21, 2017, 07:42:08 AM
Very nice, Don! I kind of hope you stick with the independent motors. All this central-drive stuff is very interesting but it seems to me that even if you made all the rotating stuff like a Swiss watch, the power losses would be huge and the weight gain considerable. I'd love to see you (or anyone) bung all that stuff into a 26" span model and see it fly like it meant it, but I'm a bit doobious. The Mosquito article George links to seemed worth a look but it states that the model can fly up to 40yds in a straight line. I'm not saying I could spit that far, but. . .we-ell. . .

I made a breadboard pulley setup - single pulley for a single prop - for a Supermarine Sea Otter idea I had. That showed real promise but the factors making it so seemed to me unique or almost unique to the Sea Otter.

Anyway, I'm enjoying the build and the discussion!

Stephen.


Title: Re: B-17 F
Post by: Rich Moore on March 21, 2017, 03:13:49 PM
I have yet to see a model fly well on indirect drive. I'm sure it has been done, but I haven't seen it. I've played with it myself, but not with any real success. (It is fun though, if you like that sort of thing). I have, however, seen many multies (with tiny nacelles) fly really well with direct drive...


Title: Re: B-17 F
Post by: strat-o on March 21, 2017, 03:24:08 PM
I believe that a successful indirect drive is feasible.  I built a Gollywock once and it flew with 20g+ of rubber.  It's launch was so fast that it was almost like watching a power model.  With the right combinations and engineering it is possible to create a high-performance indirect drive.


Title: Re: B-17 F
Post by: billdennis747 on March 21, 2017, 04:01:17 PM
I always pictured indirect drive models being designed - maybe even built - during the blackout in WW2 England, as intellectual exercises. I've never seen one actually moving.


Title: Re: B-17 F
Post by: glidermaster on March 21, 2017, 07:41:08 PM
Wasn't the late Doug McHard successful with a twin of some description that used the Rupert Moore transmission system?

JB


Title: Re: B-17 F
Post by: Ray_K on March 21, 2017, 09:05:19 PM
3-21-2017

If I am not mistaken wasn't the Moore drive a series of wires that transferred power at 90 degree angles ?

Cheers, Ray K.


Title: Re: B-17 F
Post by: Ray_K on March 21, 2017, 09:10:03 PM
3-21-2017

Something like this, this was in my R6 helicopter.

Cheers, Ray K.


Title: Re: B-17 F
Post by: billdennis747 on March 22, 2017, 03:40:28 AM
Yes, it was just like that. Over the last 60 years there may have been a couple of examples of models with the Moore drive, but they weren't flying shots. The combination of weight + mechanical losses + poor rubber would surely have been insurmountable. I don't remember Doug McHard doing one but if anyone would have got it to work, he could. A few years ago he did an article on one of the vintage kits that interested him - Skyleada Vickers Viking? - but I can't remember how it was driven. We have seen so many successful direct drive twins (including the Viking)
Just before the late Mike Hetherington died, we saw his Moore(?) Bristol Blenheim (?) ready for covering. He was enthusiastic about the prospects; we were less-so.


Title: Re: B-17 F
Post by: ffscale on March 22, 2017, 06:04:47 AM
The Viking that Doug built was the Astral design, which had the rear motor hook in the fuselage just behind the wing trailing edge.  The motors angled out to the nacelles through the wing centre section.  The prop shafts had a wound spring on the back of them with a hook on the end to get the drive round the corner - possible because the angle is only around 45 degrees or so.  Doug wrote it up for Aeromodeller - I have a pdf of part two of the article (which deals with building and flying the thing) if anybody is interested.  It certainly comes across as a challenging project!

Mike S.


Title: Re: B-17 F
Post by: Pete Fardell on March 22, 2017, 09:27:08 AM
This one worked well by all accounts, although it was a light foamy...

A bit from Terry Adams, its designer, here:
https://www.rcgroups.com/forums/showthread.php?295267-Shaft-Drive-rubber-power-Bristol-Freighter



Title: Re: B-17 F
Post by: FFScott on March 22, 2017, 01:25:47 PM
Did he ever build the PBY he mentioned in the postings?


Title: Re: B-17 F
Post by: vintagemike on March 22, 2017, 02:23:13 PM
Doug also built the Short Scion, a C Rupert Moore design in the late 80,s, I seem to remember it flying at Old Warden, apparently there was plenty of power available through the Moore drive, but it was prone to lock up as turns ran out. 


Title: Re: B-17 F
Post by: Pete Fardell on March 22, 2017, 04:09:12 PM
Did he ever build the PBY he mentioned in the postings?
I don't know- I never saw the actual model and don't know the chap. I just remembered seeing it in Aeromodeller.


Title: Re: B-17 F
Post by: Ray_K on March 22, 2017, 05:48:11 PM
3-22-2017

My Moore drive worked ok but was a bit clunky.

Sorry Don for getting off track on your post, where are you at on the B-17? Looking forward to seeing more.

Cheers, Ray K.


Title: Re: B-17 F
Post by: Don McLellan on March 27, 2017, 05:08:02 PM
Decided to redo the wings with slightly larger diameter nacelles.  Also wing ribs 2 and 4 now have the nacelle upper member included as part of the rib.


Title: Re: B-17 F
Post by: Ray_K on March 27, 2017, 06:56:34 PM
3-27-2017

Don, she sure is looking good  :), what's the wing span?

Cheers, Ray K.


Title: Re: B-17 F
Post by: ZK-AUD on March 27, 2017, 08:44:24 PM
Don that's looking great.  Just an errant thought I had - if the main spar was split at the engine nacelle positions and joined with say 2mm x 0.5mm carbon flat section top and bottom at those points you could run the rubber through the spar and further back into the wing.  Access for the rear pegs from under the wing...



Title: Re: B-17 F
Post by: Don McLellan on March 27, 2017, 11:04:17 PM
Thanks Ray.  The span is 26".

I plan to run the rubber motors to the wing trailing edge very much like Dave Haught did with his B-17s.  The hook in the pic is not for this model, but shows the idea.  I may have to open up the main wing spar a little at the bottom to clear the rubber, but won't know until I've given the props a run.


Title: Re: B-17 F
Post by: Sky9pilot on March 28, 2017, 03:10:43 AM
Looking good Don.  I think that'll work out well for you!
Tom


Title: Re: B-17 F
Post by: Don McLellan on April 01, 2017, 01:54:03 PM
Thanks Tom.  My friend with the 3D printer did a couple Paul Bradley design 3 bladed props for me.  These are 3.25" dia and may be a little small.  I'll give them a run in the next day or so.


Title: Re: B-17 F
Post by: OZPAF on April 01, 2017, 07:58:58 PM
Neat Don.
John


Title: Re: B-17 F
Post by: Sky9pilot on April 01, 2017, 08:06:00 PM
I like the props Don...nice to have that kind of a friend.  Gonna be a nice plane!
Tom


Title: Re: B-17 F
Post by: Don McLellan on April 04, 2017, 04:45:19 PM
Did some test runs with the props, well, to destruction.  Have decided to put the model on the shelf for the summer, and maybe dream up a new wing.  There is enough room for a 3.75" dia 3 blade plus I want to revisit a couple of things.


Title: Re: B-17 F
Post by: Crabby on April 04, 2017, 04:59:44 PM
Don, I will be the crazy one and ask about that prop.


Title: Re: B-17 F
Post by: Don McLellan on April 04, 2017, 09:02:31 PM
Hi Crabby,

I broke the prop getting ready for a fifth test run.  I was holding the prop I had just wound, trying to release a piece of wire holding the second (wound) prop.  Somehow the wire ended up in the then running  first prop, breaking the blade.  My bad, and having three arms/hands would have helped.  Interestingly, there was some vibration as the rubber motors ran down, but suspect if shedding the blade had occurred while flying, the model would have flown, probably badly but still would have flown.  (Very small dia props:  3.25").


Title: Re: B-17 F
Post by: Sky9pilot on April 04, 2017, 10:49:04 PM
Bummer about the prop Don...a break for a while is sometimes a good thing to let inspiration take over as you consider fixes!
Tom


Title: Re: B-17 F
Post by: Don McLellan on April 08, 2017, 03:35:45 PM
Thanks Tom.  This is a test run on about 250 winds per motor.  One of the rear hooks has to be tightened up a little.

https://www.youtube.com/watch?v=ipH8YqTNZG8


Title: Re: B-17 F
Post by: Sky9pilot on April 08, 2017, 08:20:57 PM
Looks like you should have plenty of power when you're ready to continue with this build Don.  I like it!
TomX


Title: Re: B-17 F
Post by: OZPAF on April 09, 2017, 03:13:21 AM
Very neat Don. I hope you continue with this build.

John


Title: Re: B-17 F
Post by: Prosper on April 09, 2017, 05:16:22 AM
Quote from: OZPAF
I hope you continue with this build.
Me too, but I agree that the shelf can be a useful resort, as Sky9 says :D. I wonder if those prop blades have enough area, I must say. BTW I've found that even single-engine, 3-blade types can fly with a blade missing - tho' admittedly that's with balsa blades that are most likely much lighter than plastic ones. They shudder their way to the ground in a fairly orderly manner.

Stephen.


Title: Re: B-17 F
Post by: Ray_K on April 09, 2017, 10:51:23 PM
4-9-2017

That's pretty cool Don, I'm liking it a lot.  :D

Cheers, Ray K.


Title: Re: B-17 F
Post by: Don McLellan on August 29, 2017, 05:27:57 PM
Built the rudder for my B-17 which took as long to build as a wing.  The interior parts of the rudder interlock together. 

Pinned together what I've done so far.


Title: Re: B-17 F
Post by: Crabby on August 29, 2017, 06:17:30 PM
Great work Don. I have always admired your courageous enthusiasm for whacky contraptions such as this. Anyway, it makes for great entertainment! You are my hero for doing the nutty stuff I only dream about, after a night out with Jim Beam and Jack Daniels ha ha ha ha


Title: Re: B-17 F
Post by: Don McLellan on August 29, 2017, 10:14:35 PM
Thanks Crabby.  Don't usually spend a lot of time with Jim Beam or Jack Daniels, but Kokannee, well, it's 'the beer out here'...............


Title: Re: B-17 F
Post by: Crabby on August 29, 2017, 10:27:20 PM
Well those two are bad influences, I steer very clear myself. I guess you found that 3D printed props are a bit fragile? Can they be made from a different material? Are there choices depending on the usage?


Title: Re: B-17 F
Post by: p40qmilj on August 30, 2017, 03:24:57 AM
 ;D what is span, weight?  love those clothespegs as vices

jim ;D


Title: Re: B-17 F
Post by: dputt7 on August 30, 2017, 03:32:20 AM
  Beautiful as usual Don, that mock up should encourage you.


Title: Re: B-17 F
Post by: Don McLellan on August 30, 2017, 10:40:22 AM
Thanks Dave, Jim. 

Crabby, the fellow who prints the props for me has used several different materials over the last couple of years.  (He also prints 1/32 slot car bodies and some of these were rather fragile as well).  The props for my B-17 are the latest material he is using, but as you mentioned, still a little fragile.  I hope to get one or two flights in before I have to switch to conventional plastic two bladers.

Jim, the weight so far is 23 grms (excluding cloths pins) and the span is 26".  The wing area is something like 90 sq ins, so shooting for a weight of around 45 grms.  My wife picked up the cloths pins at Michaels (I think) and they are a huge help when assembling parts.  Art356A also made stringer clamps with the cloths pins by adding a short length of wire and adding balsa 'arms'.  His pics attached.


Title: Re: B-17 F
Post by: Crabby on August 30, 2017, 11:43:28 AM
Don, how do you go about figuring out your diagonal ribs in the wing?


Title: Re: B-17 F
Post by: Don McLellan on August 30, 2017, 12:08:57 PM
Hi Crabby,

I draw the wing, then guess...........haha............  Actually I draw the wing in at least two views, then lay out each of the wing ribs and diagonals.  I made the diagonals a little longer because I had to sand the ends at an angle.  

Not sure if the attached is my 'latest' sketch of the wing, but it give you an idea.  The ribs and other bits are on 3" x 12" 'sheets' for my craft cutter.  And have to say, I would never add lightening holes to ribs or formers unless I made them with a craft cutter.  The craft cutter does reasonably neat holes so the balsa doesn't get crushed.  Also, the balsa I've used for my B-17 is mostly .045" thick (sold as 1/32).  Turns out my craft cutter will cut material that is close to .045" thick.


Title: Re: B-17 F
Post by: DavidJP on August 30, 2017, 12:42:03 PM
Very inspiring and hugely interesting - thanks. 

I have always wanted to build the Harold Towner one which was kitted by Astral which I rember seeing in shops as a youngster.  Far above my pocket money expectations.  I know the plan is available on Outerzone but I am not sure I would have  the stamina but at least I would not have to cope with the egg box timber today.

So anxiously waiting on you finishing this effort.  Well done.


Title: Re: B-17 F
Post by: Don McLellan on August 30, 2017, 01:34:26 PM
Thanks David.  Hope to have all the wood work done in the next while.


Title: Re: B-17 F
Post by: Sky9pilot on August 30, 2017, 04:01:28 PM
WoW Don!
You've done it again!  Another outstanding model.  I've loved the B-17 for years.  Guess I'll have to put it on the "To Do" list.
Tom


Title: Re: B-17 F
Post by: Don McLellan on August 30, 2017, 04:35:06 PM
Thanks Tom.  Still have to tonne to do on it.  And my printer has all but given up the ghost, so getting the tissue organized will be some time down the road.


Title: Re: B-17 F
Post by: kittyfritters on August 30, 2017, 04:35:14 PM
I have to admire your persistence and ingenuity, especially since you are doing this in such a relatively small scale. (1:48)

Howard


Title: Re: B-17 F
Post by: Don McLellan on August 30, 2017, 06:25:09 PM
Thanks Howard.  Agree that it is quite small but I think approaching the upper limit. span wise, for my craft cutter with the blades provided.  As mentioned earlier, I consider a flight of 10 ft or 10 seconds to be a success.


Title: Re: B-17 F
Post by: Crabby on August 30, 2017, 06:57:47 PM
Don, here's an idea that I know you have entertained...by now... great to go for 4 engined success... but 10 ft? 10 sec? I am all for it. BUT just for "SHTS" and giggles why not set up a prop up front and a motor peg out back, You could braid the rubber and damn near have a P-30. You will get a hell of a lot more than 10 sec for sure! Plus you can always put the glass back on the nose and push the four motors any time you want to.. just have that other option open is all I am asking!


Title: Re: B-17 F
Post by: Don McLellan on August 30, 2017, 07:46:37 PM
Hi Crabby,

Yes, have considered a single prop and agree it could be plan B.  However....................I gotta use up my stash of printed (left and right handed) 3 1/4" dia three bladers first.  (I've got 5 left hand and 5 right hand).


Title: Re: B-17 F
Post by: Crabby on August 30, 2017, 07:56:23 PM
Remember Lemuel? Maurice Taudevin's son? He shelved a perfectly good going Lancaster if you remember... it was a few years ago. I think it was over the props... that was if I am right a sticking point. I wonder if these 3D props would pull him out of the closet and back on the board.


Title: Re: B-17 F
Post by: Don McLellan on August 31, 2017, 10:51:05 AM
Hi Crabby,

Yes, I remember Matt (still friends on FB) and his Lanc.  I was hugely disappointed when he walked away from it.  The workmanship was excellent and I remember the vid of the glide, which also was excellent.  However, I can't remember the reason he stopped working on it.


Title: Re: B-17 F
Post by: Crabby on August 31, 2017, 11:34:40 AM
Matt (thanks) was having a bad time finding marketed left hand props, which seemed weird cause you can make em. Whatever. Maybe he got into another groove. I got off FB, sick of seeing Trumps face all the time. Maybe ask Matt to get off the couch and fly the Lanc. I even offered to do his camo tissue pro-bono. In the mean time, great looking craftsmanship with the Flying Fort! My cousin was a tail gunner on one stationed in Italy. I read his book he had some harrowing experiences!


Title: Re: B-17 F
Post by: kittyfritters on August 31, 2017, 09:55:52 PM
Hi Crabby,

Yes, have considered a single prop and agree it could be plan B.  However....................I gotta use up my stash of printed (left and right handed) 3 1/4" dia three bladers first.  (I've got 5 left hand and 5 right hand).

Why left hand props?  I fly multi rubber and all I need are right hand props.  The multiple parallel thrust lines cancel each other out.  You only need opposite rotating props if you want to do aerobatics on the rolling plain a la P-38, or if you are modeling a P-38 or a DeHavilland Hornet or some other airplane that actually had opposite rotating props.  The trick with multi-motor rubber powered airplanes is getting them to turn at all.  This is especially troublesome if you are flying indoors.  I generally have to use drag tabs and rudder tabs to accomplish this.  I have learned not to mess with the thrust line adjustments to much since with more than one motor a very little thrust line adjustment goes a very long way.

https://www.youtube.com/watch?v=WUWZMqzIsI4 (https://www.youtube.com/watch?v=WUWZMqzIsI4)

A-frame pushers had opposite rotating props just to make sure they wouldn't turn since the contests were for distance as well as duration.  With my "Old School" A-frame pusher I solved the indoor problem by using two different pitched props.

https://www.youtube.com/watch?v=3DVdn34B5IU (https://www.youtube.com/watch?v=3DVdn34B5IU)

I love multi motored rubber models...except for all the winding. ;)

Howard


Title: Re: B-17 F
Post by: Don McLellan on August 31, 2017, 11:04:28 PM
Hi Crabby,

Had a note back from Matt and he basically said that he ran out of (building) gas.  However I did offer some three blade printed props just in case his interest is once again stoked.  And am hoping that he didn't do the 'Viking funeral thing' with his Lanc.

Howard:  I am far from an expert on multi propellered (sp?) rubber powered models. but in my very limited experience I would go for left and right turning props over same direction props.  I've found them to be very slightly less directionally challenged than props turning in the same direction.  Again, very limited experience so am swinging in the dark on this one:  I've only built a couple of twins, but have big plans........ 

Curious, anybody else out there have strong feeling one way or the other regarding prop direction for multi propellered models?


Title: Re: B-17 F
Post by: MKelly on August 31, 2017, 11:13:26 PM
Been wondering about the prop direction question myself - I'm well into a Diels Tigercat build and would be most interested in hearing thoughts on same vs contra rotation for multi-engine rubber models.

Mike


Title: Re: B-17 F
Post by: strat-o on August 31, 2017, 11:59:12 PM
The Tigercat had non-contra props. I think most scale modelers go with whatever the prototype had.  Bob who built a Tupolev Tu-2 on this site about a year ago elected to go with contra props even though the original did not use them.  I didn't ask why though.

Some might say that with standard turning props that torque under power will cause the plane to bank to the left.  Of course they are right but i would counter that adding a little down thrust to the right prop and a little up thrust to the left and that problem is solved.   

Marlin


Title: Re: B-17 F
Post by: Crabby on September 01, 2017, 05:38:48 AM
It's great to hear discussion going both ways. My Dad built several multis (P-38, Capronis, etc) and he claimed they were easier to trim if they swang the same direction. I am doing a Dick Howarrd Chieftain (currently stalled on the bench). It's set up to swing from wing tips over the tops. I hear equally strong arguments either way.


Title: Re: B-17 F
Post by: Work In Progress on September 01, 2017, 06:28:30 AM
  I am far from an expert on multi propellered (sp?) rubber powered models. but in my very limited experience I would go for left and right turning props over same direction props.  I've found them to be very slightly less directionally challenged than props turning in the same direction.  Again, very limited experience so am swinging in the dark on this one:  I've only built a couple of twins, but have big plans........ 

Curious, anybody else out there have strong feeling one way or the other regarding prop direction for multi propellered models?

Hi, Don,
I'm not an expert on this at all, but for the sake of conversation, I think for outdoor rubber scale I can't see much reason to use anything other the conventional prop rotation on a multi, if only for the easy of using commercial props (of which there are a lot to make on a four engined type!)

For indoor rubber scale though, I can see more of a case for handed props on multi engined types. Reason being that in a small indoor hall one of the main trimming challenges is to get the beast to fly effectively the same circle at all stages of flight, both climbing and ascending, so that it doesn't bang into the walls.  That feels as if removing a source of varying asymmetric torque and slipstream forces would simplify matters.


Title: Re: B-17 F
Post by: ironmike on September 01, 2017, 01:08:37 PM
Having done a number of twins since the early 90s I opt for contra
rotating outbd over the top. I did a test swapping out these props to inbd over the top
and found that outbd over the top config required less down thrust. All of my
current stuff swing outbd over the top props. Left hand turning left,
Rt hand turning right. However R hand props on a twin are fine but require some
subtle adjustments. Go for it just build and fly. Take trimming to the next level.
If you have June 1982 flying models you will note B-25 flying with inbd over the top
rotation. That baby needed a lot of down.


Title: Re: B-17 F
Post by: Crabby on September 02, 2017, 12:46:01 PM
Good am Don... now that I think of it the diagonal ribs are only structural and don't necessarily need to follow the contours of the proper ribs... Thanks for poking Matt the other day, and relieved that Dave Andreski is OK. Looking forward to your proper balsa surgeries here. One thing I have been seeing, some guys are doing the glass in solid balsa
and then doing a convincing paint job. I almost like it. See the front end of Tom Arnold's B-26. It's not for everyone but I do like to explore the "out of the box " environment.


Title: Re: B-17 F
Post by: cavelamb on September 02, 2017, 10:42:46 PM
Check out HJ Towners B-17G plan on outerzone - well worth a look to see how his diagonal rubber concept might apply.  I also like the idea of a thing flexi-drive system that might allow use of the fuselage for the rubber

Hmmm.  Bevel gears, and a rubber motor run span-wise?

Contra-rotating props?



Title: Re: B-17 F
Post by: Don McLellan on September 02, 2017, 10:54:28 PM
Like Mike, the few twins I've built have been left/right props and over the top out.  And I've always done the laminated prop blade thing, blades made from two lams of 1/32 balsa, the lams glued at a slight angle to each other.  The blade shape is cylindrical.  Pic shows two 1/32 lams on a soda bottle.

Crabby:  I race slot cars with a world class body painter and will ask him for advice on painting all the small windows on a B-17.  Actually may just give him the covered fuse with some pics................he owes me.  


Title: Re: B-17 F
Post by: FFScott on September 03, 2017, 08:19:55 AM
It would be very encouraging and really useful to see a tutorial on window (and canopy) painting.  Someone, please?


Title: Re: B-17 F
Post by: Warhawk on September 03, 2017, 09:28:51 AM
There are several videos on YouTube showing how Tom Nallen does it:

https://www.youtube.com/watch?v=bQcPZXtFVVw (https://www.youtube.com/watch?v=bQcPZXtFVVw) 

Justin


Title: Re: B-17 F
Post by: Crabby on September 03, 2017, 10:12:45 AM
Just to clarify,, we are talking about solid balsa canopies, not acetate. Sorry Don, back to your program! ;D


Title: Re: B-17 F
Post by: cavelamb on September 05, 2017, 06:44:11 PM
Just to clarify,, we are talking about solid balsa canopies, not acetate. Sorry Don, back to your program! ;D

I did that on my 707 prototype.
The best idea I came up with was to draw them in CAD, and paste onto the balsa.
But, admittedly, the windshield was pretty small.


Title: Re: B-17 F
Post by: steveair2 on September 10, 2017, 10:55:37 PM
Very nice model Don.  I found this picture the other day.





Title: Re: B-17 F
Post by: Don McLellan on September 11, 2017, 12:28:29 AM
Hi Steve,

Have looked at that pic for some time, but think I'll try a four motor run first. 

A very quick pin together, and still have to do the tail gunner assembly.  Should note that the (nine / three) prop overlap is something like .25", so not nearly as bad as shown in the pic. 


Title: Re: B-17 F
Post by: Don McLellan on September 26, 2017, 06:25:29 PM
Test run today with all four props:

https://www.youtube.com/watch?v=zAFy2pC-6lI

This is on about 250 winds and one loop of 3/32" rubber per motor, approx 1.5x hook to peg.  Should mention that the airplane sound was from outside and unintentional. 


Title: Re: B-17 F
Post by: Crabby on September 26, 2017, 06:39:37 PM
Wow I am convinced! Left side running a little long is this going to be an issue?


Title: Re: B-17 F
Post by: FFScott on September 26, 2017, 09:50:37 PM
Wow!  If you could play that aircraft engine sound every time you launch it.....


Title: Re: B-17 F
Post by: Don McLellan on September 26, 2017, 10:03:54 PM
Thanks Crabby, Scott.  There are a couple small airports not that far away, and YVR is just to the south west so there are always airplanes in the air around us.

I did manage to break one of the three bladers on a test run just prior to recording (now have two broken props).  Note the broken blade and the chip out of the tip of a second blade, so suspect double contact.  I plan to glue the nose blocks in place and wind from the rear, but won't glue until I get a feel for how much down thrust is required.  Also note the bead added to the inboard props to step them forward from the outboard props.


Title: Re: B-17 F
Post by: p40qmilj on September 26, 2017, 11:22:01 PM
 ;D  how did u do those 3 bladers?
jim ;D


Title: Re: B-17 F
Post by: Don McLellan on September 27, 2017, 12:45:27 AM
Hi Jim,

I know this guy, who knows this guy, who.........................haha.............

The props were designed by Paul Bradely who sent me the print files.  I have a friend who has a 3D printer who makes props for me.  Unfortunately, the resin used by my friend is not that robust for the thin sections required for small diameter props, hence the blade breakage.  And he can only do small diameter props.

Don



Title: Re: B-17 F
Post by: p40qmilj on September 27, 2017, 06:23:29 PM
 ;D right Paul Bradley made me some three bladers too 7 inch dia.  i have them on a p40 and a wildcat. they work great.

jim ;D


Title: Re: B-17 F
Post by: Don McLellan on April 10, 2019, 12:38:45 AM
Hi All,

This is a test.  Have just started to work on my B-17 again, but my Photoshop has kicked the bucket.  Wondering if this attachment showing the nose glass buck will work.


Title: Re: B-17 F
Post by: dputt7 on April 10, 2019, 01:15:12 AM
   Looks pretty good to me!


Title: Re: B-17 F
Post by: OZPAF on April 10, 2019, 09:18:45 PM
Me too Don. Good to see you back on this.

John


Title: Re: B-17 F
Post by: Don McLellan on April 10, 2019, 11:11:32 PM
Thanks Dave, John.  I got side tracked with some other things and lost track of time.  Anyway, the plan is to finish the model and fly it this summer.  Just doing the bucks for some of the glass.  The lump in the back ground will eventually become the ball turret. 


Title: Re: B-17 F
Post by: dputt7 on April 11, 2019, 12:11:35 AM
  Don't you just love all the bits you have to make to build these models, I've just been doing the same thing for my Avia and had out one of 2 boxes of Plugs (Bucks) left over from previous models. This is the smaller of my 2 boxes  ;D
    Great to see this type of modelling, watching with interest.


Title: Re: B-17 F
Post by: Sky9pilot on April 12, 2019, 12:24:56 PM
Looking good Don...glad to see you're back to modeling the B-17...I love the looks so far!  Your plugs look great!
Tom


Title: Re: B-17 F
Post by: Crabby on April 12, 2019, 12:42:33 PM
Don the ball turret, whats the diameter work out to? And are you gonna have it rotate?


Title: Re: B-17 F
Post by: Don McLellan on April 12, 2019, 02:25:02 PM
Agree Dave, I too have a bag of plugs from previous models.  Thanks Tom.  As mentioned I didn't realize how long I had left it on the shelf.

Hi Crabby:  the ball turret is approx .875" flat to flat, and approx .96" dia.  I'm almost certain I won't make it able to rotate, mostly because it may take the brunt of the load when the model returns to terra firma.  Also, the diameters are a guess, scaled from a not so detailed drawing.  If I have to redo a plug or two because they are the wrong size, no big deal.  Hope to try vac forming the 'glass' tonight.


Title: Re: B-17 F
Post by: DavidJP on April 14, 2019, 06:43:29 AM
Hmmm..... you might find that getting the "glass" off the buck will be a bt of a b****r as it might wrap itself under the buck. ;) :D :D 

Never mind careful treatment will prevail.  Oh and is there a trace of woodworm in some of the timber??


Title: Re: B-17 F
Post by: Don McLellan on April 15, 2019, 12:22:56 PM
Hi David,

Did manage to remove the 'glass' from the bucks without too much trouble.  (That's code for pass the larger hammer).  The lower ball turret is more or less fitted and have taped the nose glass in place.  The upper turret I made is too big so will have to make a smaller version.


Title: Re: B-17 F
Post by: OZPAF on April 15, 2019, 07:28:33 PM
Neat Don. The glazing makes a big difference.

John


Title: Re: B-17 F
Post by: Don McLellan on April 15, 2019, 10:56:15 PM
Thanks John.  Agree, the nose glass does sorta finish the 'look'.  Have re-done the upper turret buck and will do another this coming Friday.  (Slot car friend has a vac form that works; we race on Friday nights).


Title: Re: B-17 F
Post by: steveneill on April 16, 2019, 12:54:11 AM
Don this is amazing. Great work.


Title: Re: B-17 F
Post by: Prosper on April 16, 2019, 04:54:53 AM
Good to see this off the shelf, Don. Good stuff.

Stephen.


Title: Re: B-17 F
Post by: Crabby on April 16, 2019, 07:03:01 AM
Good am Don, so far I am glad you have had little or no trouble getting the acetate off the “buck” (?) but I have had a few troubles, and I was able to get it off pretty 1-2-3 with a little blast (or three) of compressed air. This is advice for those who can take it or leave it! ::) Glad you are back on the Fortress! I still have a multi half done glaring at me!


Title: Re: B-17 F
Post by: DavidJP on April 16, 2019, 08:39:55 AM
I have to say it is looking remarkably nice!  Are you going to produce it as a kit?  Would be nice. I think Astral did one (before you were borne) but it was rather larger and the wood was awful.  Have you decided on a colour scheme - like the picture?  There were some very good ones and you skills with printing and cutting tissue will make it pretty easy.

I wish I could work out why these small models are so aesthetically pleasing, apart from being practical.  Your 17 is a prime example.


Title: Re: B-17 F
Post by: Don McLellan on April 16, 2019, 01:45:29 PM
Thank you for the kind comments.

David, I was originally going to build the Memphis Bell (B-17f) or one of the other f models where there is some reasonable documentation.  But in searching around I found that there was a B-17f piloted by Captain Hascall C McClellan (very similar last name).  Unfortunately the airplane and crew were lost on a mission over Wilhelmshafen on 22 March 1943:   https://b17flyingfortress.de/en/b17/42-29659-liberty-belle/  So am building 42-29659.  Because it was lost after a week of it's arrival, I haven't been able to find any pictures of the airplane, so will be guessing at a lot of the detail.  I've had the tissue 'worked out' for a long time and will do some test prints soon.  And David, no plans to do a kit.

Crabby, thank you for the compressed air tip. 


Title: Re: B-17 F
Post by: Don McLellan on April 23, 2019, 11:08:20 PM
A wise man on this board once said building a rubber powered model airplane is 90% building the structure and 90% figuring out the details.  Right now I think I'm half way between.

Not a lot of work on my B-17 lately other than rearranging a few things.  I did provide the opening for the upper turret and redid a few sticks here and there aft of the turret.  (First pic).  I still have more to rearrange before covering. 

Also, have been undecided how to do the windows in the nose area.  Initially thought I would print the windows on tissue but the current thinking is it wouldn't look right because of the clear glass at the nose.  Have decided to 'frame' the windows with balsa sheet (second pic).  I will have to do a little sanding and a lot of bending and fiddling in order to fit the window sheets to the nose of the fuse.  Note that the window sheets were cut using my craft cutter and I did a few spares, just in case.  Then there is only the other 90% to go.


Title: Re: B-17 F
Post by: C VEICH on April 24, 2019, 01:48:19 AM
A wise man on this board once said building a rubber powered model airplane is 90% building the structure and 90% figuring out the details.


I am still a relative beginner at FF but in the RC scale fraternity we say that once a model is all framed up and ready for finish work to begin that it is "90% done with 90% left to go".  So I think I can relate to your sentiment!


Title: Re: B-17 F
Post by: dputt7 on April 24, 2019, 03:27:26 AM
Don, how would you go if you just covered the cabin area in clear Mylar and then with you superior tissue skills recover with the windows cut out.


Title: Re: B-17 F
Post by: Don McLellan on April 24, 2019, 12:25:38 PM
That is a great idea Dave!  Certainly will give it some thought.


Title: Re: B-17 F
Post by: Don McLellan on May 01, 2019, 12:40:07 AM
Decided to go with the balsa sheet for the nose.


Title: Re: B-17 F
Post by: steveneill on May 01, 2019, 01:35:08 AM
So good. Really fine work Don.


Title: Re: B-17 F
Post by: Sky9pilot on May 01, 2019, 01:32:23 PM
Outstanding job Don...I love the looks!!!
Tom


Title: Re: B-17 F
Post by: Crabby on May 01, 2019, 04:03:06 PM
Don, how would you go if you just covered the cabin area in clear Mylar and then with you superior tissue skills recover with the windows cut out.

Don, this is a great idea, matter of fact I used mylar in the passenger windows on my Piper Navajo. Just apply with permanent glue stick and use your wife's blow-dryer to shrink it.


Title: Re: B-17 F
Post by: Don McLellan on May 01, 2019, 10:21:11 PM
Thanks Steve, Tom.  And agree Crabby mylar probably is the best way to go, but...............  Still fooling around with fillets and other small things, then will probably try printing some tissue.  Also, it looks like I will have to make some balsa 3 blade props.  The printed 3 blade props I have are almost falling apart.  The blades are quite thin, and the material used for the print does not like any amount of sunlight; it becomes quite brittle.


Title: Re: B-17 F
Post by: steveneill on May 01, 2019, 10:44:21 PM
Don it would seem it's time to make your own if they are for flight. Or buy Superior Props blanks.


Title: Re: B-17 F
Post by: Don McLellan on May 02, 2019, 12:31:22 AM
Hi Steve,

Yes, agree.  Did cut out some blades and other things with my craft cutter this evening.  The blades are on the right of the pic, and the misc other parts for the props are on the left.  Hoping everything fits!  If so, will post a pic.


Title: Re: B-17 F
Post by: steveneill on May 02, 2019, 12:33:17 AM
Very good Don. That's the stuff.


Title: Re: B-17 F
Post by: OZPAF on May 03, 2019, 09:29:19 PM
Your craft cutter certainly saved some work Don! That's looking interesting.

John


Title: Re: B-17 F
Post by: Don McLellan on May 04, 2019, 02:54:21 PM
Hi John,

Yes, the craft cutter is a lot of fun to fool around with.  It can make very delicate cuts while I watch.

Don


Title: Re: B-17 F
Post by: PaulBrad on May 04, 2019, 04:47:59 PM
Don - If you decide to cut window openings in the fuselage tissue and apply it over clear Mylar, your craft cutter can be a big help. I have been using my craft cutter to cut tissue and it works really well. The key for me in getting the tissue to cut without tearing is to sandwich it between two pieces of printer paper. A challenge would be getting the tissue inside that paper sandwich positioned accurately for cutting the windows. My personal approach for doing that has been to cut the windows before printing the tissue. I find I can position a piece of tissue attached to its backing sheet very accurately in my printer once I lay down an outline print. The tissue is positioned over the outline so something like the window cut outs are positioned properly. The tissue attached to its backing sheet is then loaded into the printer using the same registration mark as was used to print the outlines. I have been very satisfied with the results when the tissue gets printed.

Paul Bradley


Title: Re: B-17 F
Post by: steveneill on May 04, 2019, 05:15:30 PM
Don if I may ask what craft cutter model do you have. I have been thinking about getting one. Thanks.


Title: Re: B-17 F
Post by: OZPAF on May 04, 2019, 07:27:20 PM
That's clever Paul.

John


Title: Re: B-17 F
Post by: Don McLellan on May 05, 2019, 01:55:58 AM
Hi Paul,

First of all, thank you very much for the three bladed prop print files.  I had my slot car friend print them for my B-17 and they turned out perfectly, both left and right handed props.  Unfortunately, the material we used ages with time, so the props may have become a little brittle.

I hadn't thought of cutting tissue with my craft cutter!  Talk about pushing/exploring the envelope!  However, for me, my craft cutter and printer don't talk to each other, so not sure I can get things to align.  I do have some text and graphics around the front cabin windows on my B-17 tissue files, so suspect getting the craft cutter to accurately cut the tissue windows without cutting the graphics may be a stretch for me.  But will look into it.

Hi Steve,

I'm using a Silhouette Portrait (low end) craft cutter and have to say it has been quite an experience.  I LIKE IT!  If you can create a DXF file (or other acceptable file for the cutter) it is only a few key strokes away from making parts.  Just stock up on balsa, then design away.  Delicate cuts you probably wouldn't try with a knife, say 1/16" dia holes, come out perfectly, time after time after time.  (At least for me they do).  Note that with this craft cutter, the maximum depth of cut is .040" and the max length for the Portrait is 12".

Don




Title: Re: B-17 F
Post by: PaulBrad on May 05, 2019, 02:19:30 PM
Hi Paul,

..However, for me, my craft cutter and printer don't talk to each other, so not sure I can get things to align.  I do have some text and graphics around the front cabin windows on my B-17 tissue files, so suspect getting the craft cutter to accurately cut the tissue windows without cutting the graphics may be a stretch for me.  But will look into it...

Don- You really do not need to have the craft cutter and printer talk to each other. That is the reason I cut the tissue before printing. I don't need to worry about cutting the printed tissue in the exact location. By doing the cutting first and then printing, you can get really good registration. The key for me is to print the outlines of the graphics that will be printed on the backing sheet. The cut tissue can then be accurately placed on the backing sheet. By then registering the backing sheet in the printer using the same location reference marks as were used to print the backing sheet outlines, you can get a very accurate placement of the printed graphics on the cut tissue.

Paul Bradley


Title: Re: B-17 F
Post by: Don McLellan on May 07, 2019, 12:06:16 AM
Hi Paul,

Ok, will give it a try.  One issue I can see is my printer is old (actually very old and mostly worn out), and does not grab the paper to be printed with any accuracy.  Not sure if this is an issue. 

Have been fooling around with small three bladed props and I think settled on a design.  Each prop will have 16 pieces of balsa and 6 pieces of aluminum and plastic rod (uncut in the attached pic).  Plus, need the round nose 'cone' at the front of the prop and some aluminum tube through the prop for the hook wire etc.  Prop dia is approx 3.4" and will be left and right handed, over the top out.

Don



Title: Re: B-17 F
Post by: Don McLellan on May 19, 2019, 08:54:48 PM
Still trying to build some decent propellers, then decided to try printing some tissue to relieve the frustration.  The nose art is so small, it almost is invisible. 


Title: Re: B-17 F
Post by: Don McLellan on May 20, 2019, 07:42:50 PM
Just for fun, I did glue the tissue to one side of the fuse to check fit and orientation of graphics.  I wasn't too worried about wrinkles because the tissue will be removed and some new/revised printed.


Title: Re: B-17 F
Post by: OZPAF on May 20, 2019, 08:01:18 PM
Impressive Don - how else would you handle such tiny graphics?

John


Title: Re: B-17 F
Post by: Don McLellan on May 20, 2019, 11:21:41 PM
Hi John,

I'm tossing around printing a decal of the nose art, on clear decal paper, and placing it over the tissue.  If there isn't too much 'stretch' in the tissue it may add to the colour.  Maybe.  Also, as mentioned, this airplane was lost on it's first mission, and I haven't been able to find any pics etc, so, everything I've done is 'pie in the sky'.

As far as printed tissue goes, I want to move all the graphics up slightly, maybe 1/2" or so.  Right now the trailing edge of the wing root is grey rather than green, so did miss that, as well as a few other things.

D


Title: Re: B-17 F
Post by: PaulBrad on May 21, 2019, 11:35:55 PM
It sure is going to look nice when the final tissue is on the model. If the nose art had a less complicated outline, it might be possible to cut a piece of white decal paper to the outline shape. That could be applied to the tissue and allowed to dry. The image printed on clear decal paper could then be applied over the white background. I have used that approach on several models with good results. The small size and lettering over hang on your nose art would likely render that approach as not doable. Even for your craft cutter.

Paul Bradley


Title: Re: B-17 F
Post by: Don McLellan on May 22, 2019, 09:23:02 PM
Hi Paul,

I think a good idea, but as you point out, the lettering extending past the central art will be quite difficult to cut, then place a clear decal over.  I'm going to play around with making the nose art very slightly larger, which will maybe enhance the resolution of the detail. 

Don


Title: Re: B-17 F
Post by: DavidJP on May 23, 2019, 05:08:11 AM
Or build a bigger model anyway?  May save the issue with the props.  :D and some others to boot.


Title: Re: B-17 F
Post by: Don McLellan on June 04, 2019, 01:06:06 AM
Haven't forgotten about this model, just trying to figure out how to do the nose windows.  I think (know) I'll cut them out with my craft cutter and glue them to the underside of the 1/32 balsa.  I know they should be flush, but ................

First pic shows the windows cut from a plastic sheet; the windows have to fit around the interior balsa stringers hence the irregular perimeters.  The second pic shows the forward most window installed.  I still have to 'tune up' the cut file a little, and find some better, thinner, plastic sheet.


Title: Re: B-17 F
Post by: steveneill on June 04, 2019, 12:13:47 PM
Excellent planning Don. This  model is a real gem.


Title: Re: B-17 F
Post by: Don McLellan on June 04, 2019, 12:39:25 PM
Thanks Steve.  It's been a fun build so far.  Currently wondering if I should cover the nose, but leave the bottom two stringer widths open to allow installation of the windows, or install the windows, then cut the window openings after the tissue is installed.


Title: Re: B-17 F
Post by: steveneill on June 04, 2019, 12:42:36 PM
That's a good question. I'm not sure what I'd do. Maybe cover the nose then add. Maybe.


Title: Re: B-17 F
Post by: PB_guy on June 04, 2019, 04:57:16 PM
What you should ask yourself is 'How am I going to get that window back when it falls into the fuselage?' Because it will - Murphy's Law.

Great work on this model, by the way.
ian


Title: Re: B-17 F
Post by: Don McLellan on June 06, 2019, 11:48:31 PM
Hi Ian,

Had a good chuckle when I read your post because every single time I did a window test installation from the inside, the 'glass' fell inside the fuse and most of the time it was very difficult to find.  There would be no way to find the fallen windows if I had covered the fuse first.  So, have decided to try gluing some window material over the outside balsa (done), apply the printed tissue over, then carefully cut the window openings in the tissue.  The pic shows the nose with the 'glass' glued over the balsa, and one of my many test pieces with the tissue 'hacked' away.  I was quite brutal with the tissue removal in the test piece just to test the integrity of the 'glass'.

Will try installing the printed fuse tissue in the next few days and report back.


Title: Re: B-17 F
Post by: DavidJP on June 07, 2019, 03:31:27 AM
Not bad at all - but do make sure you clean the windows thoroughly - something presumed a speck of dirt can become a FW190!

I suppose it is not possible to cut the windows out before applying the tissue - only your expertise on printing on tissue and applying same is not so dusty?  But what are you using for glazing?


Title: Re: B-17 F
Post by: Yak 52 on June 07, 2019, 04:20:50 AM
Hello Don,

Been following your build with interest - I love how you manage to convey so much with simple structures in your models  8)

Just a thought - the windows look quite small and maybe don't need to be stiff material? Could you cover the whole nose section in thin mylar and then heat shrink it? And then apply tissue over the top with cut-outs where required? (I haven't thought this through particularly so I don't doubt you're ahead of me, but I thought I'd throw it out there :) )


Jon


Title: Re: B-17 F
Post by: PaulBrad on June 07, 2019, 11:17:37 PM
Don - I have had good luck laying tissue over clear plastic windows and then carefully cutting the tissue. My process involves an application of rubber cement to the clear plastic before the tissue is applied. I then shrink the tissue and apply the number of coats of dope I planned to use. Once the dope is set I then carefully cut away the tissue. The rubber cement protects the plastic from the dope. Doping the tissue before the windows are cut out makes it easier to get clean edges. Once cut, tease up a corner/edge and then peel the tissue off the window. The rubber cement will come off very cleanly. If there is any residue, it is easy to rub off.

Paul Bradley


Title: Re: B-17 F
Post by: OZPAF on June 08, 2019, 03:16:51 AM
That's a neat trick Paul. Jon's suggestion sounds neat as well as long as the tissue was cut carefully.

John


Title: Re: B-17 F
Post by: Crabby on June 08, 2019, 05:10:28 AM
Brilliant idea Paul. If I may add one simple thing. How bad would it be to not round the corners and just go square...OR do the corners with a (tiny but) sharp needle file first, then cut the sides tops and bottoms straight away (with a broken off double edge razor)? Just a thought or two. Working small requires a small mind!  ;D ;D ;D ::)


Title: Re: B-17 F
Post by: Crabby on June 09, 2019, 12:49:33 PM
Good am Don, I was re-reading my Chieftain thread this am and though about the tiny windows in the nose of your B-17....fred mentioned a heat shrink lam film called doculam...1.2mil thick and puncture resistant. If you are gonna cut the tissue after you mount it to the plastic, this might be a good thin and tough option. Its available at Staples or Amazon and its cheap.


Title: Re: B-17 F
Post by: Don McLellan on June 09, 2019, 02:32:09 PM
Hi Crabby,

Thank you for the info, but have already glued some clear plastic in place and have just started the recovering.  I plan to cut the tissue around the windows, then decide if I should proceed.  I've made the nose art about 25% larger in the second tissue printing.


Title: Re: B-17 F
Post by: Crabby on June 09, 2019, 05:10:34 PM
That B-17 has no worries in your hands! Its looking great. BTW I got the Lucky Bobs flux in the other day...I am now soldering like a true fluxman thanks for the tip! Go Blues!


Title: Re: B-17 F
Post by: Don McLellan on June 09, 2019, 07:57:26 PM
Hi Crabby,

Lucky Bob's is the flux of choice with my slot car friends, and agree, GO BLUES.

D


Title: Re: B-17 F
Post by: DavidJP on June 10, 2019, 12:48:38 PM
This is an example of how much home technology has improved our lot!  I only wish I could do it.  Not even necessarily as good was that!  Just a bit.   


Title: Re: B-17 F
Post by: Don McLellan on June 28, 2019, 02:55:08 PM
Have got most of the green tissue done on the fuse.  Just have to finish the underside then onto the wings and tail.


Title: Re: B-17 F
Post by: Sky9pilot on July 02, 2019, 04:51:59 PM
Don...up to your usual high quality.  The nose art looks great.  this is really progress great!
Tom


Title: Re: B-17 F
Post by: gjvwezel on July 03, 2019, 07:58:54 AM
Who that's looking very nice


Title: Re: B-17 F
Post by: Don McLellan on July 03, 2019, 10:36:18 AM
Thanks Tom, gjvwezel.  Hope to start covering the wings in the next week or so.


Title: Re: B-17 F
Post by: OZPAF on July 03, 2019, 08:34:27 PM
Neat Don - worth all the effort to get a result like that.

John


Title: Re: B-17 F
Post by: Don McLellan on July 23, 2019, 02:08:45 AM
Grandson's baseball has been getting in the way of model building, again, but have managed to cover the undersides of the wings, and have printed some tissue for the outer nacelles.


Title: Re: B-17 F
Post by: OZPAF on August 01, 2019, 05:07:32 AM
The wing looks great Don.

John


Title: Re: B-17 F
Post by: steveneill on August 01, 2019, 09:24:42 AM
Really nice!


Title: Re: B-17 F
Post by: Balsabug on August 02, 2019, 03:01:16 PM
Oh my good Don. I leave for a couple of years and come back to find you building B-17’s. And quite beautiful I might add. But then I already expected no less!!!! Great looking build! I am going to go back and catch up on this one!! Keep the reports coming!!!

Bug