Veneered foam vs traditional built up construction

[Doctor Chinnery]

kc - looking at the various Uglies on the Net I can see your point about the potential weakness at the back end of the fuzz - the plane that inspired my interest in trying to produce a viable veneered foam airframe is an old one I spotted on the Outerzone, the Basic 60 (OZ6946). The Basic 60 definitely follows the principle of: If it looks right it'll fly right, and it does just does look "Right". The Basic 60 also has that bit more "meat" at the back end of the fuzz which should provide just a little more strength where it's needed. (Of course a little carbon or Kevlar between the veneer and the foam would also be an option.)

[Geoff Copping]

I have an Art Hobby Odyssey glider which is produced in eastern europe and has quite a large aspect ratio so it is a very thin section at the tips which would definitely be difficult to replicate as a built up version.

Also, the wing is laminated with Black Poplar. Just three coats of sanding sealer and there's no need to glass it. A very strong efficient wing that suffers homesickness when not in the sky.

I know Black Poplar is light and strong because I also have a rifle that has a stock made from it.

[Nigel R]

Posted by Doctor Chinnery on 13/10/2020 08:53:21:

kc - looking at the various Uglies on the Net I can see your point about the potential weakness at the back end of the fuzz - the plane that inspired my interest in trying to produce a viable veneered foam airframe is an old one I spotted on the Outerzone, the Basic 60 (OZ6946). The Basic 60 definitely follows the principle of: If it looks right it'll fly right, and it does just does look "Right". The Basic 60 also has that bit more "meat" at the back end of the fuzz which should provide just a little more strength where it's needed. (Of course a little carbon or Kevlar between the veneer and the foam would also be an option.)

DC, I believe some of the fancy pattern models use a foam composite as the fuselage skin. They do have quite large fuselages though.

Basic 60 looks a good design. Lots of potential to customise things, I see a nice low wing version on the outerzone page.

[Ron Gray]

The purpose of my original post was to illicit views on the use of VF in model building, and looking at the responses I see very little negative ones, which is encouraging. So leading on from this my next question is this:

You are in the market for a new 'plane kit but you can only get one with VF main components, wings, fuselage pieces etc. Does this put you off buying the kit?

[Nigel R]

I've been doing a little searching for raw veneer.

Lots available - but I cannot see anywhere that beats the Balsa Cabin price per square foot, and most shops seem to need a big 8'x2' sheet to get the price per area down to the same as BC's obechi.

 

"You are in the market for a new 'plane kit but you can only get one with VF main components, wings, fuselage pieces etc. Does this put you off buying the kit?"

Not in the slightest.

 

Edited By Nigel R on 13/10/2020 09:58:29

[Ace]

Ron, in one word - No.

Veneering I would have thought lends its self well to anything parallel or tapered so should be fine for sport aircraft. However anything scale with a compound curve might prove difficult/impossible.

Use to cut 1/12th combat models from blue foam (I miss it) which meant straight fuz segments joined so a bit threepenny piece, although you could round the joints to a certain extent to give a more pleasing shape. Unfortunately that would not be an option with veneering.

[ron evans]

Posted by Doctor Chinnery on 13/10/2020 08:53:21:

kc - looking at the various Uglies on the Net I can see your point about the potential weakness at the back end of the fuzz - the plane that inspired my interest in trying to produce a viable veneered foam airframe is an old one I spotted on the Outerzone, the Basic 60 (OZ6946). The Basic 60 definitely follows the principle of: If it looks right it'll fly right, and it does just does look "Right". The Basic 60 also has that bit more "meat" at the back end of the fuzz which should provide just a little more strength where it's needed. (Of course a little carbon or Kevlar between the veneer and the foam would also be an option.)

Hi Doctor C, if you wanted to stick with a stick, it would be a simple matter of making the tail post wider, and a little deeper. Not only stronger, but gives more gluing area for the tailplane.

I had a notion to make a foam version of my" plank on a box" and this is what I did. Project is on the back burner at the moment.

Ron

[Matt Carlton]

Am I put off buying a kit if it is veneered foam?

No. Not at all.

I think there would actually be a healthy market for such kits. We used to have a lot of so called "ARC" kits which I miss. Maybe short kits, leaving the modeller to sort their own hardware, covering etc.

A sport model like a stick or a "Kwik fly" type, or a classic pattern "Saphir/Joker". Supplied as a set of f/v wings, fuselage, tailplane, fin, rudder. Could be reasonably inexpensive, and give a lot of scope for individuality.

Cheers

[Bob Cotsford]

Posted by Ron Gray on 13/10/2020 09:22:51:

The purpose of my original post was to illicit views on the use of VF in model building, and looking at the responses I see very little negative ones, which is encouraging. So leading on from this my next question is this:

You are in the market for a new 'plane kit but you can only get one with VF main components, wings, fuselage pieces etc. Does this put you off buying the kit?

Not in the least. My Warbirds La7 is largely veneered foam and was an excellent build.

Some years ago I picked up a Marvic Models Wolfgang Matte Joker which used veneered foam wings, tail and fin.  that was another quick build model that flew beautifully.  Back in the '70s there was a range of UK based .40 size VF scale models of which I had the Typhoon, that was another excellent model both to build and fly.  The Skyways models were another range that used plenty of VF and built up into good models.

Edited By Bob Cotsford on 13/10/2020 11:20:15

[Former Member]

[This posting has been removed]

[ron evans]

Although I don't buy many kits, a f/v construction wouldn't put me off.

As Matt says, in the past many cottage industries produced kits using f/v, and at reasonable price.

In the late seventies I had an aerobatic slope soarer from a kit which was all f/v. The fuz had an oval section and put up with all the rough & tumble of slope soaring. Finally met its end in a midair with a Dutchman who was on a hang gliding holiday, who also flew models. ( flying Dutchman ?) The foam blew all over mountain, but I did salvage the wings.

Ron

[Alan Gorham_]

Posted by Doc Marten on 13/10/2020 11:26:18:

Posted by Alan Gorham_ on 12/10/2020 17:10:58:

Posted by Matt Carlton on 12/10/2020 15:13:02:

Nigel;

SLEC obechi veneer sheets

One word of caution if I may. There seem to be a few different timbers which get called "Obechi", particularly from suppliers outside of the modelling hobby!

Cheers

Matt

Sorry but that is not "veneer". It is sheet wood in similar sheet thicknesses and sizes to Balsa. Proper Obechi veneer is less than 1/32" thick and comes in a much larger sheet size.

I have noticed that some UK kit manufacturers are no longer using Obechi to veneer wings and seem to be using a harder and darker kind of wood (Sapele or such I think). Whether this is due to reasons of cost or supply I don't know, but I do recall last time I bought some Obecehi veneer I had to buy two large sheets of 1/8" ply to protect it for packaging purposes, so it's not the most practical material to buy mail order...

1/32" is as close to 0.8mm to not matter which SLEC offer as an option and is suitable to cover foam, it's limited width is not a problem as Matt has pointed out. Sapele sounds like a good alternative, it's often used to face internal doors.

Edited By Doc Marten on 13/10/2020 11:28:04

I'm fairly certain that the Obechi veneer used to cover foam wings is thinner than 0.8mm. Some of the wings and floats that I have cut from foam and veneered had the veneer wrapped around the leading edge of the wing or around the turtle deck of the float. I wouldn't fancy my luck trying that with edge joined 4" wide sheets of 0.8mm Obechi.

[kc]

I have to say that veneered foam wings don't seem a very cost effective way to make wings nowadays. Veneer seems very dear and seems likely to cost 16 pounds for a 52 inch size wing which would be more than the cost of a built up balsa wing probably. ( foam wings also need balsa LE and TE also wing tips normally) This possibly accounts for the lack of kits using veneered foam wings.

There is a method of partially veneering foam wings used on Avicraft designs some years ago - the LE D box is veneered and veneer capstrips go to the TE veneer strip. Centre section is fully veneered. Obviously uses less veneer & could even use offcuts of venner if obtainable.

Covering with brown paper & PVA seems cheaper. Might use a spruce spar or carbon fibre to strengthen if needed. One old RM or RCME design about 60 inch span used a shaped hardwood LE made from DIY moulding as both shaped LE and reinforcement instead of a spar. Worth considering and a browse around B&Q etc stocks might be worthwhile to find suitable shape.

Another possible alternative is wings covered in cardboard. An article in RCME years ago said a Mr Newberry had a patent on using cardboard for model aircraft! Seems incredible that a patent could be granted though.  Could that be related to the forum member Jim Newberry who designed a few RCME plans recently?   Anyway the article showed how to use and the exact grade of card ( made by Thames Board Mills) to use. I think the article was in RCME Feb98 but I havent found my copy -yet.  Worth considering.    Paper Aviation made the Regal Eagle and Easy Peasy with card covering balsa ribs and spars. Could use foam ribs and spruce spars I suppose.

Edited By kc on 13/10/2020 13:24:43

Edited By kc on 13/10/2020 13:30:38

[Former Member]

[This posting has been removed]

[kc]

I know balsa is short now. Even if the price doubles or trebles it might still be cheaper than  veneered foam wings

When i costed it last year a Peter Miller  balsa wing design of about 50 inches cost about 28 pounds for balsa and that included fuselage, tailplane as well as the wing.   It looks as if the wing alone would cost nearly that for foam, veneer and Copydex. And thats if you cut and veneer the wing successfuly first time!

 

Edited By kc on 13/10/2020 13:41:31

[Former Member]

[This posting has been removed]

[MattyB]

Another veneer alternative is fibreglass laid up on sheets of polished plate glass, then glued in place as if it were wood. Messy though, and doesn't give you that mirror finish that a vac bag and mylars would.

[Andy Meade]

I've used that method Matty - large sheet of glass and created 2' x 4' skins. 2 layers of 50gsm glass, epoxy, then peel ply smoothed on. Comes out great, peel ply side epoxied then straight onto the foam, needs a slight sanding and good for paint.

[Ron Gray]

For an individual I can see that the cost of VF may be somewhat higher than a 'trad' balsa construction but I would think from a manufacturer's perspective it would be cheaper.

[Nigel R]

Posted by kc on 13/10/2020 13:37:48:

When i costed it last year a Peter Miller balsa wing design of about 50 inches cost about 28 pounds for balsa and that included fuselage, tailplane as well as the wing. It looks as if the wing alone would cost nearly that for foam, veneer and Copydex. And thats if you cut and veneer the wing successfuly first time!

BC's veneer is 19" x 50", and £6 a sheet. If we're talking an average 5:1 wing with strip ailerons, and some block (or balsa core tip) of a couple of inches, I think you'd get the entire wing from one sheet of veneer.

Individual sheets of 3" thick bead foam are £25 at Wickes. I think you'd get quite a few sets of wings from an 8' x 4' sheet. For a 50" type, you'd need, I guess, about a 1' x 4' slab for each panel, so that's at least four sets from one sheet, i.e. about £6 of foam per model.

PU foaming type glue seems to be favoured nowadays, from what I understand. I have no idea how much you would need for a pair of wings though.

But I think it still looks quite good on price.

[Alan Gorham_]

I still prefer to use a latex type contact glue for holding veneer onto foam. Obviously Copydex is readily available in small quantities but Ball Styccobond is the same stuff but in 5L bottles which is more economical if you are doing lots of foam veneer building.

[Nigel R]

Oh, I guess you'd need a sheet of 1/4" for LE/TE (£1.93) and some 3/8" for strip ailerons (£2.76) and maybe some block for the tips (sheet of 1/2" at £2.88). About £20 of material. Which is not bad, I think.

 

Conversely, I am knocking up a quick build fun fly type model. I'm trying to minimise cost by incorporating as much foamboard as possible. The wing is a bog standard D box of 4' span, with some flat plate tips from foamboard, and big flat foamboard ailerons. Foamboard also used for ribs, tips, webs (never again, it is too squashy to be any use here, wood in the future).

I'll spare the calculation detail, but, £15 of material all in. Slightly less than veneered foam of comparable size.

If I'd gone with all balsa, ribs and webs and built up ailerons, not massively more expensive, £20, I worked out, which is about the same cost as a foam wing of similar span. However, if the warnings are to be believed (i.e. the 150% increase) - that could be £50 in the near future...

Edited By Nigel R on 13/10/2020 15:34:49

[Nigel R]

Posted by Alan Gorham_ on 13/10/2020 15:22:18:

I still prefer to use a latex type contact glue for holding veneer onto foam. Obviously Copydex is readily available in small quantities but Ball Styccobond is the same stuff but in 5L bottles which is more economical if you are doing lots of foam veneer building.

Thanks Alan

What's your take on how thick a block of foam would be needed, could you get away with a 2" thick slab for our hypothetical 50" model?

BTW is thixofix any good?

Also, I understand most of the issue with weight is too much glue, so with contact adhesive how do you apply the stuff? credit card squeegee type approach?

Edited By Nigel R on 13/10/2020 15:37:50

[Alan Gorham_]

Nigel, personally I buy white foam in 100mm thick sheets. That gives me the greatest flexibility in dealing with thick airfoil sections and also in making floats for waterplanes.

If I was making a pair of wing panels that were 1.5" thick max. then I would want to cut a chunk of foam thick enough to cut the profile of each panel from and allowing for the waste, but I would cut the plan view of both panels in one go. That way there are less individual cuts and both panels are guaranteed to be the same shape in plan.

Using thinner foam as you suggest means cutting two individual panels to shape in plan view.

I lightly dilute the Glue and add a couple of drops of food colouring to it so I can see where the glue has been applied to the foam and the veneer. I just apply it with a 2" foam brush and aim for the thinnest, even coat I can get. I only make foam wings and floats for sports models so the ultimate weight saving isn't important to me.

Edited By Alan Gorham_ on 13/10/2020 15:48:17

[ron evans]

Posted by Alan Gorham_ on 13/10/2020 15:22:18:

I still prefer to use a latex type contact glue for holding veneer onto foam. Obviously Copydex is readily available in small quantities but Ball Styccobond is the same stuff but in 5L bottles which is more economical if you are doing lots of foam veneer building.

My "plank on box" (pic on first page) uses a white foam core with balsa D box, capstrips and t/e, stuck on with double sided tape, and a little white glue around the edges.

The same method could be used to attach veneer, either partially or fully sheeted.

Many moons ago adhesive backed Fablon was used to cover foam wings. Very popular in America.