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Building Tips and technical articles. => Building techniques => Topic started by: Dave Sabon on April 12, 2017, 10:06:29 AM
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One area of my building that doesn't seem to get better with each build is getting the cowl and fuse mating perfect. Not sure how to fix this so could some of you jump in with your suggestions. Also, could you comment on "fixing" the mating on a finished model. If I figure this out, I'd like to go back to my older models and fix this issue. Finally, are there any videos available that you could recommend on this subject. BTW, I've tried using Bondo or other relatively hard filler material to get the mating perfect but I haven't figured that technique out either. Maybe that's my solution if I had a system that worked.
Thanks in Advance,
Dave Sabon
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One of the major issues here is that a lightly built, doped cowling will shrink and contort for the life of the model. I try to stabilize this by covering the cowl in carbon vail inside and out applied with dope. Once cured it will be pretty stable. Then you can make the final cowl to fuselage mating using Superfil with clear packing tape as a separator until the epoxy sets up. On larger cowls I may use two or three layers inside.
Dave
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Well I feel it's the basic's .. make sure your parts are cut to match and when sanding make sure your sanding square and not angled. I find hardening the edges and mating sections with old thin c/a helps keep things lined up and from getting dented. The main thing is practice, practice and more practice..eventually you get the nack of it. Sometimes I use 1/64" ply on mating surfaces to get a straight clean line.
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Thanks for the suggestions guys. I'll give the super-fil and clear packing tape a try. When I've tried to use Bondo etc. I used wax paper as the separator with a less than stellar finished product. Since the packing tape will stay where I put it, it will probably result in a better finished product as it were. Additionally, I'll use the 1/64 ply mating surface a try.
Thanks Again,
Dave Sabon
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If possible mod the design so the cowl split line is straight, much easier to get the fuse/cowl interface perfect if its straight vs having a kick. Build cowl from split line up starting with a full 1/32 ply base providing for mounting screws from bottom so nothing is seen on the sides. Take care of the fit and mounting first..
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Once I get the initial fit done and the method of holding it on done, I usually finish the cowl. Glass or CF and epoxy. Clean it and polish it up then put release agent on it and use SuperFil or similar on the fuse and bolt the cowl on. Make sure all the gaps are filled. Then, if I did a good job of getting release agent in there, I pop it apart and it's a perfect fit.
Works mostly.
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1. Take a block of wood. 2. Assume there is a cowl in there somewhere. 3. Start carving until you find it.
Glad I could help.
Keith
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Hi Dave,
I wrap the fuse mating surfaces tightly with Glad Cling Wrap. remove all wrinkles etc. I then apply Super-Fil to cowl and bolt in place letting the Super-Fil squish out the sides. Set aside and let cure. Once cured sand off the excess and your ready for primer.
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This cowling, for my Stuka Tank Buster, was actually framed.
Probably would have been easier to make with blocks, but I didn't have any blocks at that time. Now I stock 1" balsa just in case.
CB