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Author Topic: B-17 F  (Read 8784 times)
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Sky9pilot
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« Reply #75 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
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Don McLellan
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« Reply #76 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.
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kittyfritters
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« Reply #77 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
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Don McLellan
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« Reply #78 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.
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Crabby
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« Reply #79 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!
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Don McLellan
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« Reply #80 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).
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Crabby
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« Reply #81 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.
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Don McLellan
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« Reply #82 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.
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Crabby
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« Reply #83 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!
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kittyfritters
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« Reply #84 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

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

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

Howard
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Don McLellan
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« Reply #85 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?
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« Reply #86 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
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« Reply #87 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
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Crabby
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« Reply #88 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.
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« Reply #89 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.
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ironmike
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« Reply #90 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.
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Crabby
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« Reply #91 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.
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« Reply #92 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?

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Don McLellan
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« Reply #93 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.  
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« Reply #94 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?
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« Reply #95 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 

Justin
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Crabby
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« Reply #96 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! Grin
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« Reply #97 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! Grin

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.
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« Reply #98 on: September 10, 2017, 10:55:37 PM »

Very nice model Don.  I found this picture the other day.



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Don McLellan
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« Reply #99 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. 
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