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Indoor Free Flight Forum => Bostonian => Topic started by: Yak 52 on January 08, 2012, 06:13:56 AM



Title: Another Boston Cub
Post by: Yak 52 on January 08, 2012, 06:13:56 AM
This is my build of Scigs30's Boston Cub design. It's a really cute little bostonian.

I started by laminating the outlines for the tail surfaces and wing tips - my first attempt at this method. It was done around a form cut from 1/8 balsa sheet. The strips were cut and soaked in warm water for an hour or two. Then laminated with thinned PVA (Speedbond). After an hour or two I released the lamination from the form then taped it back on to dry thoroughly overnight. There was very little springback.

I found that PVA sticks quite well to Sellotape  ::) but brown 'Parcel Tape' is awesome - the laminations just fell off when released.

The outlines were then pinned down on the plan and the other structure was added.


Jon


Title: Re: Another Boston Cub
Post by: Dave Andreski on January 08, 2012, 09:21:32 AM
Jon,
Those laminations look very nice.
Dave Andreski


Title: Re: Another Boston Cub
Post by: crashcaley on January 08, 2012, 09:46:26 AM
Jon, Very nice work.  Caley


Title: Re: Another Boston Cub
Post by: Yak 52 on January 10, 2012, 06:31:41 AM
Thanks Dave, Caley... it's a start anyway.  :)


Title: Re: Another Boston Cub
Post by: OZPAF on January 10, 2012, 07:36:19 AM
Your laminated shapes came out well Jon. I was also impressed by the glued joints on the finished tail and fin.

John


Title: Re: Another Boston Cub
Post by: Yak 52 on January 12, 2012, 08:08:26 AM
Thanks John, I do try to pay attention to the dry fit before I glue. I've also started to thin the PVA a bit and apply it with a small brush. That helps, as well as having the right clamping pressure applied.


I've now built the wing.

I first sanded the laminated tips flat, sticking them down on some masking tape on my bench. This holds the piece nicely and avoids breaking it. Getting it off again can be tricky! (You can always cut it off with a knife then remove the tape) The outer profile was sanded after the wing construction when it was better supported.

The tips were then pinned down on the plan and the LE and TE shaped for a close fit. Then the ribs were trimmed to fit. The LE is quite hard balsa. The panels were built as two seperate entities, spars and all, glued up but only joined by the trailing edge. This was cracked and the correct dihedral set. The centre pieces were then added.

Sanding the LE and TE is always a bit of a heart stopper for me. I find it makes it much easier and reduces the stresses on the structure if it is stuck down to the desk. Also the ribs are covered with a patch of tape to prevent damage. This means you can concentrate on the shape and worry less about unintentional 'cross sanding'.

The finished wing weighs 2.3g at this point. I also compared the Cub tail plane to my Cloudster dimer build and weight for size, the laminated structure is quite a bit lighter.


Jon


Title: Re: Another Boston Cub
Post by: abyssdncr on January 12, 2012, 09:46:04 AM
Jon,

That's looking great!  I really like your method of using tape to aid in the sanding process.  I was doing LE & TE last night on one of my builds and that would have definitely helped!
 
8)


Title: Re: Another Boston Cub
Post by: Yak 52 on January 12, 2012, 05:34:39 PM
Cheers Brian, I was just trying out an idea but it worked pretty well. By sticking it down, all the loads are directly on the piece of wood you are sanding and there is no real flex in the structure, like when you hold it by the rest of the wing. That means very little stress on the glue joints.

The tape is single-sided wide masking tape - its just taped down the 'wrong way up' with smaller pieces.


Jon


Title: Re: Another Boston Cub
Post by: OZPAF on January 13, 2012, 06:41:57 PM
I like the use of the masking tape to hold the wing down and protect the ribs, as well, Jon. It would have helped considerably on some recent Hanger Rat LE's.
I imagine you are using a small sanding block for the LE and TE's. I found that a paddle pop (ICE?) stick with some 80grit was great as very little pressure was needed and the finish sanding could be done with a emery tape nail file, but it was still a pain to hold them still.
John


Title: Re: Another Boston Cub
Post by: Pit on January 14, 2012, 09:20:55 AM
I found a double-sided tape used by interior house painters to secure plastic tarps.  It's fairly low-tack, but I haven't tried it yet for holding parts for sanding (SHOULD work OK)


Title: Re: Another Boston Cub
Post by: Tmat on January 14, 2012, 09:44:57 AM
I've been using Scotch brand Wallsaver removable Poster Tape to hold balsa down to my board whilst sanding.
http://www.officedepot.com/a/products/508218/Scotch-Wallsaver-Removable-Poster-Tape-34/

Works a treat!
Ordinary double sided carpet tape works well if you remove some of the tack first.

Tmat


Title: Re: Another Boston Cub
Post by: Yak 52 on January 14, 2012, 10:22:03 AM
Thanks guys, I normally have some double-sided tape about the place but I'd run out. The reversed masking tape is low-tech and low tack ;D  but cheap as chips too! It works as long as the reversed piece of tape is stretched out properly to imobilize it... double sided is better of course.

My sanding block for this was largish - about 10" by 1" - I used around 400 grit but have been known to use 80 for larger bits. The LE/TE is only 1/8" by 1/16" so I wasn't intending to remove much material.


By the way, Scigs original build thread for this design is here at: http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=5018.0 (http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=5018.0) It's a lovely little model!

Jon


Title: Re: Another Boston Cub
Post by: scigs30 on January 15, 2012, 06:39:16 PM
Jon, Your build is looking great, she is a great flyer.


Title: Re: Another Boston Cub
Post by: Yak 52 on January 27, 2012, 06:55:20 PM
Thanks Scigs! I'm having fun with it  ;D

I've slowed down a bit as I've started drawing up a new Bostonian plan. Just a little more progress over the last few days... I've built up the fuselage sides. I did wet the top longerons slightly and there was no issue with spring back when the sides were released.

I've opened up the tail plane slot to allow me to trim with shims if neccesary.
This is not a lightweight by any means, but I'm aiming for the 14g target.

Apologies for the poor quality pics  :-\

Jon


Title: Re: Another Boston Cub
Post by: crashcaley on January 27, 2012, 07:30:08 PM
Jon, The pics look good to me.  And you do very nice work.  Caley


Title: Re: Another Boston Cub
Post by: Yak 52 on February 03, 2012, 08:52:56 AM
Thanks Caley  :)

The fuselage is coming together bit by bit. I've made a slight modification by adding a full nose former. As usual I've ended up with a bit of banana in the forward end - but I'll just call it "intentional built in side thrust"  :-\

I haven't gone to town on the weight with this model - the sticks are quite firm. I'm aiming for the 14g rule but we shall see...


Title: Re: Another Boston Cub
Post by: OZPAF on February 03, 2012, 09:56:00 PM
Very neat Jon. You mean it wasn't intentional built in side thrust ;D
John


Title: Re: Another Boston Cub
Post by: Yak 52 on February 04, 2012, 06:59:51 PM
Thanks John  ;D At least it goes the right way this time!


Title: Re: Another Boston Cub
Post by: Yak 52 on February 09, 2012, 08:10:43 AM
I've now added the cowl, chin and nose blocks. It's almost complete, just wheels and the UC fairing to do.

I found that there was a bit of a 'stress riser' where the cowl block joined the fuselage (I broke it!) I think this is because a very thick rigid part joins straight to a thin part and when there is stress (my sanding  ::)) or an impact, it will break at the join. I've added a couple of gussets to spread the load.

The weight so far is 8.5g. I haven't been using particularly light wood so I'm not suprised. I've also started building in noseweight - the nose block is quite dense wood. Scigs reported needing noseweight for his prototype build.

I think the nose is a bit bulbous (my sanding not the plan) but hey, it's semi-scale... At least this one has a long tail moment!


Jon


Title: Re: Another Boston Cub
Post by: tross on February 09, 2012, 09:07:44 AM
Jon,
You're doing a great job on this one. I really like it.
The nose looks good also.
Is that snow I see? Burrr!

Tony


Title: Re: Another Boston Cub
Post by: OZPAF on February 09, 2012, 06:07:12 PM
You have the perfect soft test flying area there Jon ;D except for the fact that its wet.
Loads of character and I like that nice tail moment.
John


Title: Re: Another Boston Cub
Post by: Yak 52 on February 09, 2012, 06:46:02 PM
Thanks John, Tony. Yeah, ironically we are now having the coldest weather of the winter so far. Some have it a lot worse though...

Loads of character and I like that nice tail moment.

I agree! Kudos due to Scigs for that  ;)


Title: Re: Another Boston Cub
Post by: Yak 52 on February 20, 2012, 05:51:39 AM
Started covering the Cub... The tail surfaces were quite straight forward but covering the bulbous nose block has been a pain. I'm on attempt five or six now, using dope with wet tissue. Attempt 5 was almost acceptable but not quite there yet... I was getting double thickness wrinkles around the edges.


Title: Re: Another Boston Cub
Post by: Yak 52 on February 22, 2012, 04:54:24 PM
I've finally given up on the nose block  :-\ What I have is reasonable but I still have a few wrinkles.

The UC wire was attached today, using... you guessed it a special jig  ;D Basically it just ensures that the model is level, the wing tips are level and the axles are level.

I've also added a diagonal brace to the forward fuselage. It just seemed that in an impact with the wall (rather likely  ::)) that the lower longeron would be the place it would 'go'. So the brace is an attempt to spread that load. It does help a lot, but I seem to have ended up chasing stresses around the model, adding weight and just moving the weaknesses somewhere else. C'est la vie...  :-\


Title: Re: Another Boston Cub
Post by: FreeFlightModeller on February 22, 2012, 05:35:53 PM
That has really made me smile Jon .... how you have highlighted your wrinkles  :)
Your build standard is very high .... combine this with your 'self checking criticism' and I know that we are going to see some great models coming from your direction.
I think the nose block looks a hard prospect to cover in one piece without wrinkles.

Will your UC jig be a Leg-O-liner?  ::)


Title: Re: Another Boston Cub
Post by: Yak 52 on February 24, 2012, 10:25:42 AM
Thanks Russ  ;D.

I've made some simple wheels, just two laminations of 3/32", nothing fancy. The hubs are thin brass tube which was chucked into my drill for turning. The yellow detail is tissue pritt-stuck (?) to white paper and glued on to the painted wheels.

Not very scale but not too heavy at a third of a gram each.


Title: Re: Another Boston Cub
Post by: crashcaley on February 24, 2012, 12:45:43 PM
Nice work Jon.  Wrinkles, what wrinkles; you've not seen wrinkles until you've seen my models.   ;D  Still do not get how you experts get tissue wrapped around compound curvies.  That is definitely a nicely covered nose block.  Caley


Title: Re: Another Boston Cub
Post by: Yak 52 on February 24, 2012, 04:02:31 PM
Thanks Caley, I certainly wouldn't put myself in that catagory  :-[ The compound curves are just covered with wet tissue and stuck with dope. The wrinkles can be carefully smoothed out, any that are left when it's dry, I sand a bit to flatten them and remove some of the double thickness (deeper colour). It looks pretty rough... but then when you dope it again the colour magically reappears  :) Took me about 6 tries to get it acceptable  :o

I've now done the little tail wheel. It's the same as the main gear but as the compass cutter's minimum radius is too big, I used a hole punch to cut the yellow circles.


Title: Re: Another Boston Cub
Post by: OZPAF on February 24, 2012, 06:48:36 PM
I looked and I looked :) at the highlighted areas on the noseblock and couldn't notice anything Jon. I'm afraid I agree with Caley. As a jaded old RC glider flyer  I doubt whether I could produce tissue covering of that quality under the threat of torture :D.
You must be looking forward to seeing that fly.
John


Title: Re: Another Boston Cub
Post by: Yak 52 on February 24, 2012, 06:54:08 PM
Thanks John, says more about the quality of my camera than my covering I'm afraid  :D

It's coming together... I hope to get it to an indoor competiton in a week or two so the pressure is on, especially with the BD5 too. Fuselage was covered tonight... I'll post some pics tomorrow when the light is better.


Jon


Title: Re: Another Boston Cub
Post by: Yak 52 on February 25, 2012, 06:31:31 AM
Well here's the fuselage covered... Quite pleased with the tail wheel. I nearly forgot to fit it before covering!  :-[


Title: Re: Another Boston Cub
Post by: OZPAF on February 25, 2012, 05:25:58 PM
Very nice Jon. Will that be doped?
John


Title: Re: Another Boston Cub
Post by: Yak 52 on February 25, 2012, 05:54:55 PM
Yes that's the plan, just a thin coat. I will probably be flying it outside too.

Jon


Title: Re: Another Boston Cub
Post by: Yak 52 on February 27, 2012, 11:57:48 AM
The wing is now covered too... not far to go now. The weight is up to 12 grams so I'd imagine I've missed the 14g target when you consider the prop and windscreen weight  >:(


Title: Re: Another Boston Cub
Post by: Mr Blue Sky on February 27, 2012, 03:34:50 PM
Hello Jon,
Yes, the covering is good. What tissue are you using, it looks a very nice, dense yellow?
Don't worry about the odd wrinkle, I have quite a few and I'm told it adds character.

Tony.


Title: Re: Another Boston Cub
Post by: Yak 52 on February 27, 2012, 06:39:44 PM
Hi Tony, it's just yellow esaki, bought from my local (proper) model shop. It will probably lose a bit of opacity when it is doped.

Jon


Title: Re: Another Boston Cub
Post by: DLphotog on March 04, 2012, 12:31:09 PM
Hi Jon,
Your work is very impressive to me. The bones pictured in your early posts look very clean. Which is how I wish my bones looked,maybe someday. I have not really tried the lamination technique on any of my builds, and I'm so impressed with how nice your stab and tail look that I think it's time I explored this method. I'm wondering if you, or anyone else reading this could direct me toward some detailed info/tutorials on this building technique? 

I am currently building (just started) the Walt Mooney Boston Beaver and would like very much to try out some new building techniques. Any and all help,suggestions or advice is appreciated and welcome.
Please keep posting pics of the your Cub. It's beautiful work.

DL.


Title: Re: Another Boston Cub
Post by: Yak 52 on March 04, 2012, 01:00:08 PM
Thanks DL.

I'm actually having a few problems with warps in the fuselage. I'm not sure if it's because of my covering sequence or the light structure around the cabin...


The laminating is really quite easy - there are lots of ways to do it but my sequence is:

1) Cut the form. I use a spare copy or print of the plan, glue stick it to 3/32 sheet balsa and cut around the inner edge of the tailplane etc. Then mask up the edge with packing tape. This form is then pinned to my building board. (Some people use foam for this.)

2) Prepare the wood. This time it was strips of 1/16 x 1/32". They are soaked in the sink or bath  ;D for a few hours in warm water.

3) The first strip is gently moulded around the form and held with pins (actually with little balsa blocks with pins through them to avoid marking the wood.

4) I then run a bead of thinned PVA (white glue) around the first strip while it's still damp. Mould the second strip around the first removing and replacing the pins as neccesary. It's just a case of getting it tight, pinning it against the form and then moving on. Applying more glue as neccesary as you go. (In fact for longer parts it's best to just glue as you go anyway.)

5) I release the component from the form after the glue has 'grabbed' (10 mins?) to make sure it isn't stuck to the form - but then hold it to the form with masking tape until it is thoroughly dry.

To finish up the part I stuck it down to some double sided tape to hold it while gently sanding. The tape had to be cut to remove it though.

The laminated part is then pinned to the plan as per normal for adding the rest of the structure. I've found it's sensible to make the laminated parts over size in both thickness and depth because they sand away very quickly and you end up with less wood than you might want.

Hope that'll get you started...


Jon


Title: Re: Another Boston Cub
Post by: DLphotog on March 04, 2012, 02:12:24 PM
Thanks for the detailed info Jon. I'm going to go build a rudder and stab right now using this technique.

DL.


Title: Re: Another Boston Cub
Post by: Mr Blue Sky on March 04, 2012, 03:13:20 PM
Hello Jon,
I'm sorry I have taken so long to get back to you. Thanks or the tissue info (Feb 27th). I see you are having a little trouble with fuselage warps, this is something which always worries me, I have avoided some designs which I feel would distort badly. Like you I tend to use Esaki but it has a very fierce shrinkage. I have tried pre-shrinking with varying results, my method is to attach a sheet of tissue to a frame and soak it. The shrinkage is usually quite good but it can shrink a little more, sometimes too much for a light structure. I am trying to figure a way that allows the tissue to be removed from the frame then re-attached to the frame and shrunk again, maybe up to three times, and I would like to do this without wasting too much tissue. One thing I have noticed is that the shrinkage seems to be greatest during the summer, must be something to do with the heat or maybe the dry atmosphere. One final thing, how do you stop the laminations sticking to the former, my method is to use the PTFE tape that plumbers use. It stretches and can be wrapped around the edges of a former quite easily and PVA does not stick to it. One final, final thing, do you go to the Impington Sunday events? Next one is this coming Sunday 11th.

Bye for now,

Tony.


Title: Re: Another Boston Cub
Post by: Yak 52 on March 04, 2012, 04:08:22 PM
Nice one DL - keep us updated...

Tony, I've up till now never bothered with pre-shrinkung esaki and not had any problems... I wish I had now though! I have been gradually dampening it to see if it goes back (stuck it in the bathroom  ;D) and I've seen some improvement. It was probably just too humid when I first covered it, although I did a few bits and pieces at the same time and they were ok. I may replace one of the panels but like as not I'll just put up with it.

I use brown parcel/packing tape on the form - nothing will stick to it not even CA. I used to use sellotape but it's not as good.

I was planning to come to Impington this time but now I'm not sure if I can get there...  :-\ If I can I the Cub should be done in time but the BD5 is still 'in build'.


Jon


Title: Re: Another Boston Cub
Post by: scigs30 on March 04, 2012, 11:36:09 PM
Your Cub looks great, good job. I always pre shrink the tissue when building small birds like this, or I just use Domestic tissue.  For the tail surfaces, I shrink and dope the tissue on the picture frame, then cut it our and apply it to the tail surfaces.  Also I use real stiff/hard 1/16 balsa and I have never had a fuselage warp.


Title: Re: Another Boston Cub
Post by: Yak 52 on March 05, 2012, 06:37:28 AM
Thanks Scigs. I should have pre shrunk it... I am gradually migrating to lighter wood for my builds and I should have considered the effects!


Title: Re: Another Boston Cub
Post by: Sky9pilot on March 06, 2012, 12:08:36 AM
Jon...
Cub looks great...all the guys advice sounds good....I usually pin the structure down on the board again over plastic wrap and lifted off the wrap for air to circulate underneath using pieces of scrap stringer material and spritz it with isopropal alcohol and let it dry pinned down.  So far that has worked for me...worked with the peanut Vagabond I did a while back....

I am just amazed at your ability to cover with no really visible wrinkles...super job.

Tom


Title: Re: Another Boston Cub
Post by: Yak 52 on March 07, 2012, 06:12:00 AM
Thanks Tom, I've not tried the alcohol trick yet. I was playing around by wetting certain panels to see which was pulling it out.

I managed to get it aligned by using a couple of strips of tape to pull it back into shape. The flat top of the fuselage (wing mount) wanted to go trapeziodal and the glazed part of the cabin had a slope to the left.

I've added some gussets which has helped a lot - not perfect but better....


Title: Re: Another Boston Cub
Post by: Sky9pilot on March 09, 2012, 02:43:34 PM
Looks like the gussets have really helped...good luck with this.  Hope you can get it stabilized soon.

Tom


Title: Re: Another Boston Cub
Post by: Yak 52 on March 09, 2012, 05:06:28 PM
Thanks Tom - it seems to be holding better...


Title: Re: Another Boston Cub
Post by: rgroener on March 13, 2012, 03:07:11 AM
Jon, glad you found a way to straighten the fuselage. It happens to my planes a lot more than I like.... But mostly it's not as bad as it looks like. It's not possible (for me) to build 100% straight anyway and in many cases the different warps nearly compensate each other at the end. So if the warps are not to big and dont affect the sensitive parameters such as stab incident to much, I try to fly the "warped" plane. In many cases the plane flew great and I am sure I would have worsen the problem with fighting against the warps... We build in warps such as washout... and trimming sometimes includes some intended warping to...  ::)

Dont get me wrong, I really try to build straight and I use the known techniques to reduce the warping. I just want to say that I have accepted (to a certain level) that the material is "living" a bit. At least for a certain time. After some weeks / month, the material seems to have found a "stable" form.  In many cases I was not successful to fight the warps. I was able to reduce them to a certain amount, but mostly they came back after some time.....

Best regards Roman


Title: Re: Another Boston Cub
Post by: Yak 52 on March 13, 2012, 06:22:14 AM
I just want to say that I have accepted (to a certain level) that the material is "living" a bit. At least for a certain time. After some weeks / month, the material seems to have found a "stable" form....

Thanks for the encouragement Roman. I don't mind the odd warp normally either but this was affecting the wing saddle, making it twist, so I was worried a bit about the effect on flying. I've done what I can and having left if for a while it seems to have settled down...

Cheers!
Jon


Title: Re: Another Boston Cub
Post by: Yak 52 on April 04, 2012, 06:55:42 AM
Well I've started a push to get this finished. I'd left it a while because of the warp problems - the fixes have mostly worked, not perfectly, but it has at least stabilized. I've been doing the trims and details like the UC fairings. Just assembly, prop fitting and the windscreen to do now. I'm in two minds whether to attach the wing first of the screen first. Either way will mean clamping issues for the other part  :-\

I'm also waiting for new ink cartridges for my first colour printer :) so hopefully I will be able to print the Cub decal for the fin.


Title: Re: Another Boston Cub
Post by: Sky9pilot on April 04, 2012, 12:51:40 PM
Really nice work Jon...look forward to see her all finished.

Tom


Title: Re: Another Boston Cub
Post by: OZPAF on April 04, 2012, 07:51:27 PM
Agree with Tom, Jon - very neat effort. It's becoming your trade mark. This will be a nice little flyer.
John


Title: Re: Another Boston Cub
Post by: Yak 52 on April 13, 2012, 08:00:44 AM
Thanks Tom and John  :)

Well she's more or less done.

I decided to make a little bit of an engine (inspired by Tim on SFA) It seemed a worthy way of adding a bit of noseweight. The final weight is 16.6g, just a shade over Scigs' prototype.

I was recently given a colour printer and the ink arrived just in time to do the Cub logo on the fin. I used thinners to stick it down but perhaps I should've used a gluestick.

The windscreen was quite tricky to do. I originally tried to do it all in one sheet but ended up doing the screen separately, then gluing on the wing, then doing the side windows last. I've discovered the joys of low-tack masking tape for keeping the screens clean while I glue them, makes a much nicer job of it.

Thanks again Scigs for a really sweet little design!  8)

We have no more indoor flying here for a while so I'll probably end up trimming it outside....


Jon


Title: Re: Another Boston Cub
Post by: Sky9pilot on April 13, 2012, 10:11:28 AM
Outstanding Jon....

The engine really adds to the looks...very nice indeed....
I haven't gotten to the skill level of your windscreen and window installation...very clean and sharp installation....what kind of low stick tape do you use????  Name and source please....

Great Cub ;D 8)

Tom


Title: Re: Another Boston Cub
Post by: Yak 52 on April 13, 2012, 10:31:57 AM
Thanks Tom. I do hate doing canopies and screens - the pressure is on and you can really mess up a model. I use Pacer Formula 560 canopy glue which cleans up well with water. I managed to remove it from the model both of the times I messed up! Third attempt was ok though....

....what kind of low stick tape do you use????  Name and source please....

I've got some of this stuff: http://www.pondskippercrafts.co.uk/Stix-2-Low-Tack-Stencil-Tape/prod_959.html (http://www.pondskippercrafts.co.uk/Stix-2-Low-Tack-Stencil-Tape/prod_959.html) Although I'm sure you'd get similar over your side of the pond. It's useless for actually holding components but perfect for covering cellophane or acetate and then peeling off cleanly. I used it on the screen inside and out and also on the adjacent tissue. Normal masking tape sticks ok over the top of it for holding the screen in place.

I've also been using it to mask up when sticking on wings and tails with PVA. My method is to mask up close to the glue line beforehand, then stick it, wait for 10 minutes for it to grab, remove the tape and soak/wipe off the excess with a wet/damp paint brush.

If you don't clean up you end up with a visible line. You can see on the pics of the Raven below: the fuselage/wing join was before I learnt to clean up - the glueline is visible although I scraped away at it with a blade. The second one shows the cleaned up fuselage/tailplane join. Removing the excess while it was soft makes it near invisible...


Jon


Title: Re: Another Boston Cub
Post by: Dave Andreski on April 13, 2012, 10:44:30 AM
Jon,
Great job on your Boston CUB!
I've never built a CUB. Maybe one of these days...
Dave Andreski


Title: Re: Another Boston Cub
Post by: Sky9pilot on April 13, 2012, 01:36:05 PM
Thanks Jon for the insights and clarification...looks great....now to get started on the Widgeon for the Frog Sr. cookup...hopefully the weather will let up so I can trim and fly the Bostang and the New Standard D-25...

Tom


Title: Re: Another Boston Cub
Post by: Yak 52 on April 14, 2012, 05:58:00 AM
Here's a few more details of the engine. It is just three bits of balsa each side, the tapered engine block painted with Humbrol matt black and the valve covers from 1/16 sheet painted silver. It's not very scale (and I didn't sand it all that well ;D) but it's enough to give an impression I hope.


Jon


Title: Re: Another Boston Cub
Post by: Sky9pilot on April 14, 2012, 07:29:51 PM
Jon....

Sets the nose off beautifully...Well Done 8)

Tom


Title: Re: Another Boston Cub
Post by: OZPAF on April 15, 2012, 02:41:39 AM
Very nice Jon.
John


Title: Re: Another Boston Cub
Post by: Yak 52 on October 19, 2012, 05:17:04 PM
I finally got to fly the Cub today at our first indoor meeting of the winter.

She flew very well on 1/8th, with a trim tab giving left rudder and 'crossed' aileron to keep the inside wing up. I didn't time her but I'd say around 30 seconds with 4 or 5 circuits and a couple of nice landings. The model climbed steadily for the first few circuits and got a little high so a longer motor should be about right and give more turns. The thrustlines were ok with just the tiniest opening out of the turn on the last circuit.

I 'blew' a motor as the knot slipped  :( minimal damage fortunately but does anyone have any tips on how to prevent this? I just used a double overhand before lubricating it.


Jon


Title: Re: Another Boston Cub
Post by: Tmat on October 19, 2012, 05:48:02 PM
Ahh knots......
Here's a few ideas.
There was a knot thread on SFA a while back where we talked about this. John Barker had some suggestions as did others.

http://www.smallflyingartsforum.com/YaBB.pl?num=1220717685/12#12

I did a lot of pull tests to destruction and found that the type of knots was not very important.
I used a simple stopper knot on the ends of each strand lubricated with saliva. Then I found that a simple overhand knot tied with a small amount of lube (you pull the knot slowly up against the stoppers first) worked as well as any of the "fancy" knots.
Not damaging the rubber is the real secret.

Lately I'm using a simpler knot.
Here is a Youtube video of my flying buddy showing how it's done: https://www.youtube.com/watch?v=tbriKYmW2Fk&list=UUq8wTztrrtPfl5-ar04mjaA&index=2&feature=plcp

The key is that the knot is pulled so that any damage to the rubber is done on the "back" side away from the rubber that is wound. No lube is required to make this knot.

Good luck!

Tony


Title: Re: Another Boston Cub
Post by: atesus on October 19, 2012, 06:18:27 PM
After tying the knot I apply a droplet of medium CA on the outer side of the knot. Thin CA tends to wick towards the business side of the knot, I found medium CA works best. I know some people glue the "ears" together, I apply the glue directly on the knot.

Best,

--Ates



Title: Re: Another Boston Cub
Post by: Andrew Darby on October 19, 2012, 06:31:58 PM
I do the same as atesus re the CA I just use saliva to lube the knot, pulling on he ears so that the damage (if any) is on the non business side.  Just make sure that you don't get the CA on the business side, it makes the rubber instantly brittle (guess how I know!)

Andrew


Title: Re: Another Boston Cub
Post by: lincoln on October 20, 2012, 01:51:11 AM
Ok, this is a terrible drawing of a very secure knot. Can ONLY be tied with lube. Once you get the hang of it, it's very quick to tie.


Title: Re: Another Boston Cub
Post by: Yak 52 on October 20, 2012, 06:10:36 AM
Thanks for the suggestions, I'll have a try with those.

I hadn't managed to make up motors before the session and I was in a hurry. I'd had a few motors break from nicks etc so was trying to avoid damage on the knot and obviously didn't tighten it enough  :-\ It still got to over 1100 turns before it slipped, after quite a few successful flights on less turns. I like the idea of putting the damage on the 'outside' Tony, in your video is the intial knot a reef knot?


Jon


Title: Re: Another Boston Cub
Post by: BEAR on October 21, 2012, 05:23:02 AM
I saw this little Cub in the flesh at this indoor meeting, what a loverly job of building and covering and the flights in the hall were most impressive  the model used almost the whole width of the hall and flying speed was spot on  8) 8)
Was so impressed that I give up lol  ;D


Title: Re: Another Boston Cub
Post by: Yak 52 on October 21, 2012, 05:43:03 AM
Cheers Kev!  :) Kudos is really due to Scigs for a sweet design ...


Title: Re: Another Boston Cub
Post by: Yak 52 on October 30, 2012, 02:22:05 PM
Had a few nice flights with the Cub at Impington on Sunday. Didn't really time any flights as I ran out of time while still trimming. As I started to rack up the turns I found it needed more 'out' thrust (right) and more 'in' rudder (left) to stop the circle opening out. I started with 1/8th rubber about 16" but found it too powerful so moved on to a longer motor of 20.5", this was definitely better but still too powerful and I hit the ceiling and rafters on a couple of flights. Moving down to 7/64 proved too weak to get a good climb, so I ended up with the long 1/8th again but backing off the winds to lose some of the initial the torque burst. This seemed to be working.

Only got to flights on video, one hitting the wall and another taking out another model. Fortunately the pilot didn't seem to shaken up and carried on  ;D

https://www.youtube.com/watch?v=XjS2whTo6p4 (https://www.youtube.com/watch?v=XjS2whTo6p4)

https://www.youtube.com/watch?v=8-pSlyEbt6M (https://www.youtube.com/watch?v=8-pSlyEbt6M)




Jon


Title: Re: Another Boston Cub
Post by: atesus on October 30, 2012, 05:14:57 PM
The Cub is flying very well indeed. It was funny that it still wanted to go back to flying after the midair ;D. Congrats!


Title: Re: Another Boston Cub
Post by: OZPAF on October 30, 2012, 08:00:12 PM
It looks great flying at that nice slow speed Jon.

John


Title: Re: Another Boston Cub
Post by: Yak 52 on July 06, 2013, 08:52:44 AM
Just a little update: mainly to say a big thank you to Scigs for designing such a sweet little model. It's a great flier and has a lovely docile character. I'd recommend it to anyone  :) Mine is pretty beaten up now but it just keeps on going.

I flew it outside for the first time yesterday in perfect conditions, no wind and light thermals. I was using a shortish 3/16 motor which gave a crazy spiral climb to around 150 plus feet but then allowing the noseblock to fall out as a d/t. In spite of intentionally not trying too hard,  the model did a few decent flights including one of 2:10. Great fun  ;D


Title: Re: Another Boston Cub
Post by: scigs30 on July 06, 2013, 06:55:46 PM
I am glad you like, she is a lot of fun and I lost mine in a thermal.


Title: Re: Another Boston Cub
Post by: Yak 52 on July 07, 2013, 07:55:47 AM
I'm not surprised!  8)


Title: Re: Another Boston Cub
Post by: Yak 52 on August 13, 2013, 01:43:44 PM
My Boston Cub has given me a lot of fun but I thought it was time to send her back to Piper for an upgrade. The riggers inform me they will be finished in time for the Flying Aces...

Weight of the wood is 2.5g per float.


Title: Re: Another Boston Cub
Post by: OZPAF on August 14, 2013, 07:52:54 PM
Ahh the Alaskan version Jon ;D Do you have any scale puddles nearby :D
Good fun.

John


Title: Re: Another Boston Cub
Post by: rgroener on August 15, 2013, 01:09:57 AM
Jon, very nice!
I plan to build a float plane for a long time. Good to see that you build one.
Do you plan to ROW it?

Roman


Title: Re: Another Boston Cub
Post by: Yak 52 on August 15, 2013, 04:21:48 AM
Thanks guys, yes that's the plan. There is a duration ROW class at the Flying Aces in a couple of weeks. Flying this model on a 3/16 motor got me thinking it may have enough oomph for floats. It's a bit of an experiment but I will be able to convert it back to a land plane quite easily.


http://www.peterboroughmfc.co.uk/zfrontpagepics/2011-36-Mick-FA2/WP03.htm
http://www.peterboroughmfc.co.uk/zfrontpagepics/2011-35-Mick-FA1/WP08.htm


Title: Re: Another Boston Cub
Post by: Yak 52 on August 25, 2013, 09:01:19 AM
Floats are now finished.

The spreader bars are 2mm carbon. The original UC wire forms the front strut, slotting into small pieces of aluminium tube. The rear struts pop into the fuselage where I've added a piece of balsa reinforced with 1/64 ply. The different holes allow adjustment of the float angle for ROW.


Title: Re: Another Boston Cub
Post by: Yak 52 on August 25, 2013, 09:07:54 AM
Covering is silver tissue with a couple of coats of thinned yacht varnish for waterproofing. The weight of the floats and extra struts is just under 10g giving an all up weight of 27.5g. This is just under my upper target weight. A bit heavy but they are pretty tough :-\ The wire flexes slightly in an 'arrival' but the carbon spreaders are very stiff. There is a clear acetate water rudder just visible on the float transom.

The model has been flown from a hand launch and goes well on 14" of 3/16 rubber, climbing for about the first 20 seconds and getting nice and high. Will have to wait and see if she has enough gusto to get off the pond at the Aces....


Title: Re: Another Boston Cub
Post by: IndoorFlyer on August 25, 2013, 02:25:06 PM
Went back and reread the entire thread on this build.  What an immaculate little Cub!  Those floats look great, too.  Noticed that you swapped out the prop', curious if you had flown it with that setup in the wheeled configuration?


Title: Re: Another Boston Cub
Post by: Yak 52 on August 25, 2013, 04:26:02 PM
Noticed that you swapped out the prop', curious if you had flown it with that setup in the wheeled configuration?

Thanks IF. If I recall correctly it has always flown with the blue prop - I may have just used silver for the photos. The blue one is from a Wingleader kit (distributed by West Wings) and has a bigger blade area than the 6" peck.

The videos in post #68 are with the blue prop as is this one from a while back:
http://www.youtube.com/watch?v=_6qRS5navG0
Excuse the waffle...


Title: Re: Another Boston Cub
Post by: atesus on August 25, 2013, 04:47:04 PM
Just too cute! I hadn't seen the video before, flies beautifully.

--Ates


Title: Re: Another Boston Cub
Post by: Dave Andreski on August 25, 2013, 06:28:01 PM
Jon,
Very nice job on the floats!
Dave


Title: Re: Another Boston Cub
Post by: OZPAF on August 25, 2013, 09:06:04 PM
Very neat Jon - floats and Cubs seem to complement each other. Can you adjust the angle of the floats relative to the fuselage? i've noticed that most of the rubber powered floatplanes seem to use a a short run and almost jump off the water.
Your moe scale approach may be a challenge to get of teh water - but what the heck - what fun anyway ;D
John.


Title: Re: Another Boston Cub
Post by: rgroener on August 26, 2013, 01:49:29 AM
Jon, very cool!
They look great. Keep us informed about flight trimming. I want to see this plane Row ;)

Roman


Title: Re: Another Boston Cub
Post by: Yak 52 on August 26, 2013, 05:05:51 AM
Thanks chaps.

Can you adjust the angle of the floats relative to the fuselage? i've noticed that most of the rubber powered floatplanes seem to use a a short run and almost jump off the water.
Your more scale approach may be a challenge to get of the water....

John, the rear strut attachment has a series of holes so you can adjust the angle (pics in post #78).

The floats look scale but I've tried to follow the formula outlined in Millard Wells' article:
http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=510&mode=search
And Bill Noonan's Good Tern.

The step is forward of the CG so the model sits back on the rear float. The only real difference is that mine have transoms instead of canoe sterns. I figured the canoe stern gave less buoyancy to allow a quicker rotation in ROW so I skinny-ed up the rear of the float and increased the deadrise angle to reduce buoyancy at the stern.

The pond at the Aces is quite tiny but rubber models need to get away quick because you are using the intial power burst. If you get past that and you're still on the water I suppose you'll just get a loooong taxi  ::) My hand launch trimming was promising but I was avoiding max turns. On the day I'll get the blast tube out and see if I can get that last bit of real torque.

The Cub has floated ok in the bath but we'll see....


Title: Re: Another Boston Cub
Post by: OZPAF on August 26, 2013, 07:03:28 PM
Whoops missed that Jon. I suppose an impromptu pond wouldn't be too hard to organise for tests.
Its an interesting challenge.
John


Title: Re: Another Boston Cub
Post by: Yak 52 on September 02, 2013, 06:33:47 AM
Sadly there was no pond this year at the Flying Aces as the venue cancelled the bowser at the last minute  :( The ROW event was run as duration from a hand launch instead. It was a bit blowy but a cracking day out.

Managed one video (cheers Phil) of the Cub:
http://www.youtube.com/watch?v=J1avrL75VVI



Title: Re: Another Boston Cub
Post by: Pete Fardell on September 02, 2013, 06:38:40 AM
Excellent- can't wait to see it off water. Looks like it's got plenty of oomph.


Title: Re: Another Boston Cub
Post by: Super64 on September 02, 2013, 09:14:03 AM
Wow Jon!  :o

My heart skipped a beat when she dove for the ground.

Whew! nice recovery

Well Done. :D

-  8)


Title: Re: Another Boston Cub
Post by: THB on September 02, 2013, 09:33:29 AM
Wow - got a lot of height in the wind. Nice flight.


Title: Re: Another Boston Cub
Post by: Yak 52 on September 02, 2013, 11:48:37 AM
Thanks guys.

My heart skipped a beat when she dove for the ground.

Joe, yeah the torque roll is pretty fierce and in theory the motor will take still more turns  :o (This was 1000 on 14" of 3/16) I did try adding right thrust at a previous session but it seemed to hurt the later climb. I need to try it on water, then if there's any excess power I'll try a longer motor.


Title: Re: Another Boston Cub
Post by: OZPAF on September 04, 2013, 07:29:23 PM
It needs guns as well Jon ;D What a great flight following the ground strafing run. The floats must be helping with their extra side area and they certainl didn't seem to affect its duration all that much. Did you miss those trees?
John