OOLILISSIMA

Barry, thanks very much once again.

I actually had heaps of Correx that I begged from estate agents when I was a surveyor, but it seemed I was never going to get time to do any modelling, so I let it go a couple of years ago. Of course, I now regret it. Having said that, I do like the idea of making this essentially a paper model.

In fact, the Auster J/1 Autocrat and Mk 5 both have the NACA 23012 aerofoil which, as I expect you know, is slightly harder than Clark Y to build on account of its curved bottom.

I have developed a different method for constructing the cardboard wing. It is essentially similar to a traditional built-up balsa wing. The strength and lightness are very surprising to people who have grown up thinking that cardboard is weak and heavy. That's quite odd if you think about it: for it has to be strong to protect the goods and be stackable, and it has to be light for handling and transportation.

I glue (approx. 50:50 PVA: water) together layers of corrugated cardboard, totalling about 7.5mm thick. From the resulting sheets, I cut out the rib sections using a jigsaw, which cuts accurately and with the edges of the ribs nice and square to the sides.

The rib flanges I make with Depron wrapped in 80gsm paper stuck on with PVA. I build D-tubes/box sections between the leading edge and front spar and between the aft spar and aileron spar similarly; i.e. with Depron faced both sides with the same paper (of course, sticking the paper on the outer face of the curve stuck after fixing the Depron!) I stick continuations of the rib caps onto the D tube to give the impression of continuous ribs to the correct position (this is precisely as you suggested earlier except that I will not be using balsa). The nose section I make from builder's polyisocyanurate insulation foam (your foamboard?), which is very strong and light - and hard, once the paper covering in in place. Interestingly we seem to have come up independently with practically the same idea here, if I understand correctly your point about sticking card on both sides of a foam component.

I build the ribs in sections, each of which is embedded into the layered corrugated cardboard spars, by sticking on pieces of the outer layers of the web to fit between the ribs. Plywood - from orange boxes - is used to reinforce webs and ribs where necessary; e.g. at strut fixings or servo mountings.

Just to clear up what may be a misunderstanding, the cotton scrim is stuck on the back of the paper covering. It reinforces the paper, and doesn't on its own create the linen effect that I mentioned. That effect is from the surface of the paper itself, with just a light impression of the scrim's pattern showing through.

For rib tapes, the same paper as for the covering, but without the scrim, is ideal . Also, tearing the paper against the edge of a hacksaw blade creates an accurate 1/3 scale pinked-edged over-tape. I may have misunderstood what you are suggesting, but card tapes would be too thick and prominent, even at this very large scale.

I share your liking for cardboard for, among others, the reason that you state; i.e. it doesn't shatter. I also note your points about fixing metal to cardboard. Did you also know that PVA itself fixes very well to abraded aluminium surfaces? My parasol struts will be based on this discovery: the corrugated cardboard will be scored so that it can be wrapped around and stuck to the aluminium tubes, then wrapped in the same 80gsm paper as for the covering (again without the scrim). The cardboard stiffens the metal struts considerably. So much for "weak" cardboard.

While I am further on with my design than you may have gathered, and am already committed to most of my methods, it is good to hear of other ideas. They help me check my own thinking, and they also provide alternatives in case things go wrong.

I will post some photographs ASAP, so that, hopefully, what I have written will become a little clearer.