Cable trailing edges
 

Hello, I'm currently trying to put together a design for a 1/5th scratch-build project, a Fokker DIII biplane.
This one had bevelled trailing edges typical of many early designs and I'd like to try using a close-to-original cable construction.
I've never done this and was wondering about a few aspects, e.g. what material to use as a cable, how to attach the cable to the ribs and how to cover it such that the covering stays put and doesn't stick to itself from both sides. Or can you simply get away with just using covering?

Any ideas, experiences or photos would be a huge help! Also please consider this an open thread, it will be a long time before I can return to building, feel free to post pics and any details on whatever model you've used these techniques on.

RE: Cable trailing edges
 

I'm hoping to do that with my scratch Fokker DVII, but haven't got that far yet. The Proctor plans talk of fastening the wire to the trailing edge of the ribs with narrow, thin pieces of aluminum that wrap from bottom to top, and capture the cable against the trailing edge of the rib. They also talk of covering the wing with a continuous piece of material; fasten at the lower leading edge, wrap around the trailing edge, then fasten at the upper leading; then shrink to satisfaction on the cable.

Les

RE: Cable trailing edges
 

The smithsonian Albatross book goes into detail of the trailing edges, but to model it is much harder. The scalloped look comes from the shrink of the covering against the wire, and when the Smithsonian restored their Va they only put in about half the tension because they were worried about long life. I think the tension was to be something like 75 ft lbs. I dont think you will get a natural look with shrinking with even spacing. If you need wire, music wire bent to your shape; you probably know Mick Reeves uses this. I plan to build a Fokker D7 1/6 soon and the plans show thin ply( I think 1/32) shaped edge inset into the trailing edge of the ribs.

RE: Cable trailing edges
 

It's the same method used on the Kitfox kits.

RE: Cable trailing edges
 

Good to see you back, Trev! I'd really like to do a model like this as well. But I don't think that the iron-on fabrics will provide enough tension to get a scale-looking scallop effect. I've seen people used a stiffer sort of wire trailing edge for a straight edge. So on our models it might be necessary to "pre-scallop" the wire.

The other problem might be that our model ribs might not be able to take the straight of the tension needed to scallop a wire. It'll obviously take some experimentation.

RE: Cable trailing edges
 

Thanks for all the comments! Must admit I am tempted to try out the strategy Les mentioned and then using the continuous piece of covering to shrink the TE 'to satisfaction'.
It seems straitforward but I suspect that extensive trials with test-assemblies might be necessary to produce a good result without ruining the wing due to varying tensions between ribs. I'd imagine (as was also mentioned) that even spacing might be an issue with ribs being pulled in one or other direction and that getting the scallops at identical depth could be difficult.
The pre-formed wire solution also is appealing, the TE spacing would be rigid and secure with constant-depth scallops. One difficulty here might be to bend a continuous piece of music wire to such a shape and ensure that all scallops are 'in plane' (perhaps with a kind of jig??).

Don, didn't the Alb CIII that you're preparing to build have this kind of TE??

With regard to my project, its in the very early stages and due to time constraints I don't expect I'll get around to any building until sometime next year. I'm using the Fokker DI-IV windsock datafile 3-views to draft up some crude Corel Draw plans of the DIII aileron version. The DI and DII versions actually had wing-warping, what a dauting prospect to design that into a biplane!

On the off-chance that anyone has modeled any of these A/C or is intending to, I'd love to hear of it.

RE: Cable trailing edges
 

After I posted last night I found myself wondering if thin solder might not make a neat material to make a pre-formed TE from. It would be easy enough to make up a wooden tool to put the curve in the solder.

RE: Cable trailing edges
 

Yes, indeed! But I'm going back and forth between using Chris' excellent thin ply + balsa TE technique (as stock on the kit) and the pre-bent wire/solder idea. I may try out the wire idea on a mock wing segment.

RE: Cable trailing edges
 

I don't know how to put the quote in the box, but anyway:

"With regard to my project, its in the very early stages and due to time constraints I don't expect I'll get around to any building until sometime next year. I'm using the Fokker DI-IV windsock datafile 3-views to draft up some crude Corel Draw plans of the DIII aileron version. The DI and DII versions actually had wing-warping, what a dauting prospect to design that into a biplane!"

Bummer Trev. I was planning on you doing the experimentation, then telling me how:-)))))))))))))))))))

Les

RE: Cable trailing edges
 

Les I'd really like to oblige you and get started on some mock ribs and wing sections, I'm convinced that it can't be that hard to simulate or reproduce a cable TE. Unfortunately its hard to do when the modeler and his workshop are in different countries (ireland vs. germany), considering it will be months before I go back it's hard not to get impatient.

Don, could you please elaborate a little on that thin ply and balsa TE method? I'm not absolutely dead-set on using e.g. wire, any other nice technique will be a welcome inspiration. The solder solution you mentioned also sounds interesting, is that silver solder or the standard stuff?? I'd say the latter is probably too soft to maintain its shape.

RE: Cable trailing edges
 

Trev: At the rate I'm going, you may well get there before I.

Les

RE: Cable trailing edges
 

The TE is made up out of a lamination of 1/64" ply underneath 3/32" (or so) balsa. Then when the edge is sanded down, the tip of the TE is only as thick as the ply. This results in a scale thickness for the TE. The disadvantage is that, if the upperwing fabric is semi-transparent, you'll be able to see the "width" of the TE would be visible.

I was thinking of standard soft solder. It would indeed be "soft" and therefore easy to form. But I think that once solartex were shrunk around it, it would hold its shape just fine.

When I get back to Japan, I can try out a couple of techniques on my "practice wing." I'll try both the solder idea and the cable idea.