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Future balsa supplies in UK

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Matt Carlton26/10/2020 13:53:13
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I seem to remember seeing some old plans using a mixture of poplar, bamboo and obeche. Ribs were rather intricate built up articles. I believe this was during/just after WW2 when balsa wasn't available.

With Obeche strip available from SLEC in anything from 1/16" square up to 1/2" square, it should be possible, or even sensible, to consider similar woods.

What would be interesting would be a way to create equivalent sizes. So, for example, what size Obeche strip would be needed to replace a 1/4" square balsa longeron?

Graham Davies 326/10/2020 14:09:34
151 forum posts
54 photos
Posted by Nigel R on 26/10/2020 13:46:25:

Graham, interesting project, following along, hope you don't mind a couple of comments as I have played with foamboard a bit,

that board is about the same weight as a 3/32 piece of wood, using a complete top and bottom skin you end up with the equivalent of a solid wing of 3/16 balsa... how would that work out in weight terms for the whole model?

Hi Nigel,

Feel free to comment! It's what these forums are all about.

My feeling is it will be a little heavy. However, there is very little structure to the wing so it does save in other areas if compared to traditional construction. I really only have a spar and wing skins. I was thinking of a jedelsky structure, but wanted a sports aerobatic section.

I have some ideas to lose weight. I may try cutting out sections where strength isn't needed and covering with doculam, or even plain paper.

As i stands, this prototype will have very little balsa or ply. Just the motor mount and a lightly wing joiner as it stands. I reckon it will weigh around 16-20Oz, so 12-15Oz/ sq ft. Should fly OK, but not with the performance of the depron 3D thingies. More sports plane than 'physics defier'...

Graham

Nigel R26/10/2020 15:46:33
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I wonder if it would help to remove the paper on the inside of the skin? You could definitely go to a D box with regular ribs (foamboard, obviously!) and foamboard caps.

For reference, I have made a few "single sheet" foamboard hacks, they have been delta / circular / square flying wing types and have used most of a whole A1 sheet, they have all wound up flying at about 14oz including 3S1000 lipo. None have had a fuselage to speak of and the wings were all from a single flat piece of board. The main problem with a single flat sheet is that it warps something rotten when exposed to the merest sniff of damp. Going again, I would try and use some carbon tow or a couple of 3/16 balsa spars to keep the warping in check.

Graham Davies 326/10/2020 16:01:53
151 forum posts
54 photos

Removing the inner skin was my original plan Nigel. Have you seen the flighttest videos on Youtube? These guys have whole ranges of foam board kits (and a huge amount of fun doing it!). They had some tutorials for doing basic things like making curved panels. Some of the feedback comments seemed to relate to different board, and how it behaves. It seems in the US that Dollar Tree board works well for this.

My foam board however, doesn't! Getting the paper off was all but impossible, so I thought again. I made cuts in the inside and could then get the stuff to curve. I was also fearful of warping, and hopefully this will balance out. I have to say, the wings as they are with upper and lower skins and a pit of 3mm spars are impressively stiff. I will fit a balsa leading edge tonight as I want a rounded leading edge, and that should be it. Each wing is around 65g, so not too bad.

I'm going to see how this turns out, bit weight and performance and then make a second prototype. I will think about construction techniques for that one in the light of any lessons learned.

It is worth a bit of background of the performance I'm looking for from this model. On the back of a fabulous afternoon at our club for our annual "spot crashing" competition (Climb to height, power off and land closest to a flag; average of 4 attempts with one discard), I was thinking how we could extend the competition. The idea of single model appeals as this with extensive hangars have an otherwise advantage. Problem is, not everyone is a builder and we would end up with 2 entrants. If I can make a model that will fly like a sports model, bounce like a ping pong ball and be cheap and quick enough to build to give half a dozen away, there may be legs in my idea. So, the model needs to be quite tough to survive all the activities; loaded enough in case the day is a bit blustery, cheap enough to promote stupid behaviour (always to be encouraged) and hopefully good enough to get a few more people to knock something ridiculous up!

Graham

ken anderson.26/10/2020 17:06:25
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8791 forum posts
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I've ordered some balsa from Slec…….they only had "hard" balsa available....

ken anderson...ne...1..hard dept.

RICHARD WILLS26/10/2020 17:11:30
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655 forum posts
97 photos

Chaps , Ive done quite a bit of Foam board bashing , in fact my first Warbirds back in 95 had foam board fuselages.

The white foam we get hold of can be stripped of one side and curved . Firstly , look at it under a good light and you will see it has a grain . You must have the grain length wise through the curve (like balsa ) .

Peel off the glossy layer , then get a wet flannel and circulate it . That will make little "snow balls " that pick up more paper till you get one side clean . It is time consuming but weirdly fun . Keep the clean side on a towel to save marking it .

Finally draw the foam side over a desk edge many time to create a curve .

Mark Turner 1227/10/2020 09:27:45
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21 forum posts
4 photos

I’ve used hobby craft foam to make some flitetest models. The first one a tiny trainer which is used to learn to fly delaminated when it got damp, so now i cut the parts out, the. Put them in a warm bath and that allows the paper to float off. Then glue together with hot melt or uhu poor. After that I cover with hobbycraft film, some do have light ply reinforcement, and I make the power pods completely from ply with side and down thrust. Works fine for me.

Nigel R27/10/2020 09:46:33
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4278 forum posts
711 photos

Bet you have to be a bit careful with the covering iron!Also I did not find hot melt glue lasted very well in high stress areas (firewalls, etc). I would imagine your use of ply around the motor mounts area would fix that.

I find foamboard glues up reasonably well with cyano, although the superthin stuff is best avoided on edge joints, as the heat when it cures can melt the foam. It's fine on the paper surface. And thicker CA seems ok. I would guess Copydex type contact adhesive should work quite well, too.

Worth noting also that Hobbycraft board is, I think, a bit heavier than the Flitetest board.

Mark Turner 1227/10/2020 11:19:42
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21 forum posts
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Yes, if you get too hot with the covering iron you get some orange peel, but I did manage to stretch film nicely round the wing tips, it works surprisingly well. The other glue that works well is gorilla yellow glue,the one that foams up.

Graham Davies 327/10/2020 12:02:09
151 forum posts
54 photos

Some interesting points Mark.

Have you tried removing the card from one side only? I think it adds a lot of strength (and weight!) so is good for wings. I hadn't thought about delimitation when it gets wet.

I may buy some of the really thin laminating film. I know Ron Grey has had a lot of success with this, and it may provide a lightweight covering to 'seal' foam board models. It may be possible to cover after painting the board; that would be neat.

Regarding glue, I have been using the foaming Gorilla glue, and am quite impressed. Apart from getting you right messy, it's easy to work and sets pretty hard. My Rans-a-like is having it's wings set at the moment, so will soon be able to do a weigh in.

One other thing; the package my foam board arrived in had a sheet of plain foam either side. This is a nice bonus. I'm going to use that to make a turtle deck. I guess that's pretty much what you are ending up with Mark?

Graham

Graham Davies 328/10/2020 09:02:23
151 forum posts
54 photos

Project "Cheap as Chips" moves on a bit.

I now have a (nearly) complete aeroplane. Just needs the top decks fitting and some sort of canopy, and the control surfaces linking up (someone used my kebab sticks for, well, kebabs. How VERY dare they...). I will squirt a bit of colour onto it, just because there doesn't appear to be a gap in the weather any time soon...

So, all up weight is 17 Oz with 500mAh packs. Likely to be a bit marginal on power and duration so have some 1000mAh packs in standby for a 2Oz weight penalty. It balances with the batteries on the C of G, which is nice. Loading with the small pack is 9 Oz/ sq ft, but power is not likely to make the 3D boys happy.

There is a tiny amount of conventional modelling material: leading edges are 1/8x1/4 strips, wing joining brace is 1/8" liteply, motor mount and 2 reinforcing plates for this are also 1/8" liteply. I used 7 A3 sheets of 3mm foam board to produce a 33" span model.

Total airframe cost is around £6. With the ultra cheap 9g servos (these have done a lot of hours in several models without any issue at all), a 30A ESC and a turnigy D2830, 500mAh battery and a flysky FASST receiver, the total airborne cost is £55. Not bad...

I shall report on it's performance when we get a gap in the weather. Meantime, Mark and Nigel will show us how to do this all properly!

Graham

foamboard rans 28102020.jpg

Nigel R28/10/2020 09:43:25
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4278 forum posts
711 photos

Ha! I'm not particularly accomplished at foamboard airframes.

My efforts.

Nutball, from a single flat bit of board, coloured in with marker pens and a toy story alien printed out and stuck on the fin.

20190112_104749.jpg

Pizza box flyer. Pretty much the same as the nutball, but square, and with elevons and rudder. Pretty good for practicing 3d harrier type high alpha flight at an altitude of around one or two feet. The low cost goes a long way toward being willing to try silly stuff and not worry about breaking something expensive, or something that took a long time to make (3 hours total). About 120W.

20190303_165245.jpg

And a Dekan Delta.

200W rocket.

20190117_120402.jpg

Any amount of damp is the undoing of these.

I did try varnishing them to prevent delamination, which did work to an extent, but the rather large and unfortunate side effect of that was to simply make the foamboard warped in a slightly different way. Still, you get what you pay for (i.e. almost nothing, in this case).

That said, with film covering, the board seems to last very well.

Graham Davies 328/10/2020 10:13:59
151 forum posts
54 photos

Those models are great Nigel. I agree about using 'disposable' models to try new things. That's really the point of this little project.

I've certainly learned a lot already, and that's part of the fun

Graham

Mark Turner 1228/10/2020 13:04:37
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21 forum posts
4 photos

Yes, I just use the foam without the paper, also reduces the weight. I’ve also found it’s easier to get a nice wing profile without scoring, only the le needs scoring and then I arrange a number of spars to get the right wing profile, the last one had a nice Clark y. I sand the TE to get a nice shape, although if I make ailerons I tend to sand a v shape and then bond 1.5mm balsa either side with gorilla glue to get a nice stiff control surface.

Mark Turner 1228/10/2020 13:16:41
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21 forum posts
4 photos

80c33bd9-66ad-4f2e-9f5a-b69356ea3001.jpegHere is my modified flitetest simple scout. Covered with hobby king film. All hobbycraft foam board with the paper removed. I do have 1/8 lite ply doublers on the inside of the fuselage and wing seat. Turtle deck is planked foam board although balsa sanded would look better. Wing is all foam board with Clark y section and balsa covered foam board ailerons. Flys really nicely.

Edited By Mark Turner 12 on 28/10/2020 13:17:29

Graham Davies 328/10/2020 15:02:43
151 forum posts
54 photos

Nice Mark.

Looks like you've used a similar idea to me; use spars to get the airfoil profile. I guess using more spars compensates for the lower strength of removing the wing paper skins.

Looks great though. I'm going to experiment with laminating film covering. I like the idea of decorating the outer paper skin (I will remove the inner) and then covering with ultra thin, clear film, This should prevent water issues and make the model pretty durable. Going to wait to see how this one flies first; I might need some other tweaks!

Nigel R28/10/2020 15:18:32
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4278 forum posts
711 photos

Another idea to throw in the mix for wings, my 3d foamie had a wing consisting of a standard bead foam core, skinned with depron. The LE was formed from depron. Couple of carbon rods out to about 2/3 span for spars. Slightly flexible but light and plenty strong for a 1lb ish model.

Lima Hotel Foxtrot28/10/2020 22:16:31
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408 forum posts
Posted by RICHARD WILLS on 26/10/2020 17:11:30:

Peel off the glossy layer , then get a wet flannel and circulate it . That will make little "snow balls " that pick up more paper till you get one side clean . It is time consuming but weirdly fun . Keep the clean side on a towel to save marking it .

My word, that seems like a lot of hard work! I've just been holding the board over a kettle, letting the steam loosen the glue, and then just peeling the paper off.

On another note; the WestFoam stuff I have been using from Hobbycraft weighs roughly 6g for 100 sq cm. Removing one side of paper removes 2g! It's pretty dense, but can take a knock quite well.

On a different note... Has this thread not gone off track by quite a long way...?

David Ovenden28/10/2020 22:38:02
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424 forum posts
56 photos

Yes, looking at the recent posts I would say its time to start a new thread about "alternatives to balsa" or "building with foam board"

Geoff S28/10/2020 23:21:26
3902 forum posts
57 photos

One of the reasons I went for both the CNC cut parts and additional wood pack for Peter Miller's Rans Chaos was because it looked like buying the wood for myself would be difficult and using wood I already had would deplete my stock (realtively modest as it is) and make repairs or mods more difficult.

I haven't tried recently, but are 'proper' (ie balsa/ply) kits in short supply too?

Geoff

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