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Cardboard construction for planes

possible alternatives to balsa

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kc13/10/2020 16:53:41
6956 forum posts
175 photos

Balsa is in short supply at the moment and price is likely to increase according to the suppliers.

One possible alternative is to use cardboard construction. An article in RCME Feb 98 by J.R.Newberry said he had a patent on using cardboard for model aircraft construction. Seems incredible that a patent could be granted though. Could that be the forum member Jim Newberry who designed a few RCME plans recently?

The article showed how to use to make wings and the exact grade of card ( made by Thames Board Mills) to use. Thickness of card was 800 microns, weight 300 grams/sq metre, surface was suitable for painting.

Various firms in the past made planes from card - Stanley Aviation had a kit called Matilda and later Paper Aviation made the Regal Eagle and Easy Peasy kits with card covering balsa ribs and spars.

So has anyone had any experience building with card and knowledge of suppliers of suitable material in small quantity? Is it practical now?

Alan Gorham_13/10/2020 17:16:09
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J R Newberry was John Newberry and I think he worked for Iggesund Paper so was familiar with paper and card products.

I think I remember that he built some large (LMA style) models using his card techniques and that Dr Jeremy Shaw also used the technique to build his large Canadair CL-215 amphibious waterbomber.

Those of us who are LMA members can access archive copies of all the LMA Journals and I think there are some articles in there from about 1991?

Radio Modeller featured a plan by a chap called Roger Stanton who used to write the nostalgia column in the BMFA News up until a few years ago when he sadly passed away. The model was called Intruder and resembled the Peter Russell Striker a bit. It was made out of yer everyday corrugated cardboard. I built a half-sized version intended for a 21 two stroke and while the technique worked well for me and was cheap, it was probably too heavy for such a small model. Would no doubt have been fine at the intended plan size!

**LINK**

Nigel R13/10/2020 17:17:00
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Several cardboard ugly box type sport designs on outerzone:

Cardboard 500:

**LINK**

Cardboard Stik:

**LINK**

The Stik uses 0.010" cardboard skin for a fairly normal foam veneer wing. Lots of corregated card edged with balsa for other bits including fuselage sides.

The 500 has an odd wing section, but is built around a spruce spar with card ribs - otherwise quite similar.

 

Edited By Nigel R on 13/10/2020 17:26:16

Simon Chaddock13/10/2020 17:25:30
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5860 forum posts
3107 photos

c

It is certainly possible but it does require some understanding of how to use the cardboard to make best use of its strengths.

As an exercise I made a built up wing out of a particular cereal pack cardboard as a direct comparison to a Depron foam one. 

Cereal wing 1

Even thin cardboard is heavy to be used just as a covering material so much better for it to be used as a stressed skin, unfortunately its compressive strength is only a small fraction of its tensile capabilities so under compression a carboard skin has to be well supported.

The wing is made up of inner and outboard panels set by the size of the cereal box.

The ribs are cut from 5 mm insulation foam. The additional support at the root is to handle the compression from the wing retaining bands. 

Depron card 3

There is no spar as such just a foam web at the point of maximum thickness. All the bending tension and compression loads are taken by the carboard skin.

The outer panel has a barn door aileron built in exactly the same way.

Depron card 2

Each panel is joined by an external carboard strip covering the joint.

Joinstrip

A basic Clark Y wing section.

WingSection

The finished 1200 mm (40" wing  on my 'hack' pusher fuselage.

14mar19

Flies ok too.

It is a bit heavier (about 25 g) than the foam balsa wing but not enough to significantly effect its performance.

 

  

 

Edited By Simon Chaddock on 13/10/2020 18:07:56

Nigel R13/10/2020 17:26:50
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4435 forum posts
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by, say, a nice lump of white foam? smiley

I suspect card skin would make a decent foam wing. I would guess a pair of spruce spars sunk in to the foam would help the skin resist any folding type loads.

Edited By Nigel R on 13/10/2020 17:28:04

GrahamC13/10/2020 17:34:38
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1247 forum posts
202 photos

I've built a couple of models out of cardboard and both flew. It was an experiment really to see if it could be done. Neither lasted very long, but that's at least in part due to the fact that because they were experiments I didn't make any effort to cover them in a way which would offer them some protection.

I think that one of the problems with card is that it doesn't tend to wear very well. That said, one page which is worth a look is this one: **LINK** There are some quite remarkable models on the pages that follow.

All my building with cardboard has been with repurposed card, but large sheets of virgin corrugated card are available on eBay.

Tom Gaskin 113/10/2020 17:36:22
50 forum posts
5 photos

There is a twin made from corrugated cardboard called fun-tu, an RCM plan from the US. You can find it on Outer Zone.

Tom

Mike T13/10/2020 17:46:27
610 forum posts
41 photos

FYI:

A Cardboard RC plane

Frank Skilbeck13/10/2020 17:56:05
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4936 forum posts
114 photos

I built a Stanley Apprentice trainer model many years ago, was powered by an OS40 FS. It flew quite well and was reasonably robust. The wing used a folded cardboard trailing edge, back from the main spar, with a foam leading edge.

kc13/10/2020 18:18:45
6956 forum posts
175 photos

This is one way to use card on wings

cardwing2.jpg

kc13/10/2020 18:19:37
6956 forum posts
175 photos

The Stanley wing used foam as well

cardwing.jpg

kc13/10/2020 18:25:42
6956 forum posts
175 photos

I like working with balsa wood so much I don't really want to use alternatives. I like the ' Razor Blade Carpentry ' aspect - indoor carpentry where if you make a mistake the wood can always be used for other smaller parts.

However if balsa supplies dry up I would use mainly liteply for fuselages, spruce for spars and possibly card to cover foam ribs.   Tailplane and fin could be foam covered in brown paper, maybe with a leading edge made from a bit of litply to stiffen and give a ding proof edge.

Edited By kc on 13/10/2020 18:32:25

John Wagg13/10/2020 18:50:57
171 forum posts
24 photos

I used corrugated cardboard for the ribs on my 362 Deltas many years ago. All other parts were balsa etc as per plan. I cut the cardboard so that the corrugations were vertical.

Robin Colbourne13/10/2020 20:38:00
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784 forum posts
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kc, You were not alone in thoughts of cardboard modelling today, I was batting various ideas around, particularly regarding a larger trainer-type model. having read up on the Paper Aviation Ezee PZee trainer earlier.

It would be good to see what can be done with the cardboard that is all around us as used packaging, rather than splashing out on new stuff and large amounts for delivery of relatively small quantities.

I'm a great believer in playing to the strengths of each material we use, rather than trying to build an entire airframe from one type, even where it clearly isn't suitable. If the intention is to produce a low cost airframe, then the whole project from start to finish needs to be considered. There's no point in building an airframe from low cost materials if it still needs to be covered in expensive iron-on film or fabric.

Mark Kettle 113/10/2020 22:11:53
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2574 forum posts
1591 photos

I've made a glider with cardboard, called 'Hill Billy', it was 40" wing span weight 30oz

20160415_134628.jpg

Hill Billy 40 span  weight 30oz

Picture Album here link - example below

20160510_184306.jpg

image002.jpg

It flew surprisingly well.

Mark Kettle 114/10/2020 22:08:59
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2574 forum posts
1591 photos

KC, you asked if it's practical? It's cheaper and it can be done, however watch out for water or should I say rain. When I was flying something else I left Hill Billy out beside the car when I got back it was a bit soggy. Mined you, after it had dried out, I checked it over for any 'warps' etc and it was OK and flew again no problem.

Below, Hill Billy over the sea.

Hill Billy over the sea

i12fly14/10/2020 23:19:47
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684 forum posts
23 photos

From GrahamC's link above, some pages in, I see that Maurice Ashby (David's father) did a free plan 'Cardsharp' in May 2000. At 30.5" span and 18.5 oz/ft2 for an OS15 it shows it it is comparable performance -wise to balsa.

David Ashby - Moderator15/10/2020 08:20:40
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Yes he did. The build article is here.

It flew well and we know of several that were built. He made a bigger one, pictured, but preferred the smaller model. 

bigsharp.jpg

Edited By David Ashby - Moderator on 15/10/2020 08:36:15

Peter Miller15/10/2020 08:56:03
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11782 forum posts
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I think that Correx plastic sheet is far more practical than card. It certainly lasts a lot longer being almost indestructable.

My original "Blue Movie" could never be damaged and I believe still resides in someones loft.

Another one was built in Canada and is still in the owners hands.

Anoyone else seen a "Blue Movie"?

PLans still available from Sarik Hobbies

Edited By Peter Miller on 15/10/2020 08:59:01

Mark Kettle 116/10/2020 09:10:42
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2574 forum posts
1591 photos

Yes I'd agree with Peter, if your going to stray from traditional balsa for a build I would choose Correx, it has no problem in the rain and a extended life, I still have serviceable tail planes, elevons and fins on models built 15 yrs ago.

Edited By Mark Kettle 1 on 16/10/2020 09:13:01

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