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Building Tips and technical articles. => Building techniques => Topic started by: Dave Nyce on January 15, 2015, 12:59:12 PM
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I am assembling a kit plane with built-up wing and fuselage (Enterprise-E). When assembling the wing and horizontal stabilizer/elevator assembly to the fuselage, I made sure they were exactly parallel. But now after further work and a couple of weeks, I find that they are no longer parallel (one tip of horizontal stabilizer about 1/2 inch out of being parallel with the wing). The plane does not yet have final sanding, finishing, or any covering. I know how to fix the level of the horizontal tail on a profile fuselage, but are there any good ways to fix it on a built-up fuselage? I was thinking of twisting the fuselage so the tail is a little past parallel with the wing, and then mist the fuselage with cyanoacrylate. Any other ideas?
Thanks
Dave
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Full fuselages like that are box structures, which are very rigid torsionally. If you put the tail on before the top and/or bottom sheet was on, and didn't hold everything in alignment when you did put the sheet on, then that's where you messed up.
If you could send pictures of what you have it will help us help you. In my opinion, though, you need to undo the box by taking off at least the top or bottom sheeting, then put it all back together with things in proper alignment.
If you really can't stand the thought of that, then cut the horizontal stabilizer out and put it back in straight. Your fuselage may still be a bit tweaked, but at least your tail won't be.
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That is a good way, before put the stab and the fuselage together, to build into the stab one so-called "T-rib", made of 5-ply 2 mm (1/12" or 1/16") thick plywood. You can make this "T-rib" very precisely to 90°. (naturally, it must have a hole in the vertical part for the pushrod).
After gluing the wing, you need to glue first the stab, between the fuselage sides, precisely adjust it to parallel, horizontally and vertically. The rear 1-2 fuselage ribs go in after this step.
Now for you it is better to disassemble the stab, instead to try to turn the fuselage: it won't be never precise and stable, I think...
Itvan
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If you could send pictures of what you have it will help us help you. In my opinion, though, you need to undo the box by taking off at least the top or bottom sheeting, then put it all back together with things in proper alignment.
Dave,
I also had a twisted fuselage with this stunt ship I'm building.
I never had a twist before in a fuse, but it happened.
I did exactly what Tim suggested. I removed the top and bottom balsa. I also had to slice each former vertically, three I believe plus the end piece.
I squared everything up and used CA as I always do. I did the formers first. A bit of block sanding for the fuselage side edges to true them up, then I refit the balsa tops and bottoms.
Looks better than new because new was twisted. n~
My stab and rudder wasn't in place.
Good luck.
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A rather easy way is to shim it. Picture in your mind the direction you want the stab tip to go. If the bottom sheeting in glued on, take your razor saw and cut a diagonal cut in the bottom about half way back from the wing. The cut should angle towards the front going from the side with high side of the stab. Just cut through the sheeting. Now take a sliver of hard 1/16" balsa about 1/4" wide and shove it into the cut. You may have to help it out with a little twisting of the fuselage to open up the cut. Get the shin in completely and site down the stab to the wing. You should see an improvement. If you need to go more, trim off the excess of the first shim and tack glue it in place. Then move about an inch in either direction for another cut and shim. When that shim is installed and it is too much, just remove the shim and sand it thinner. Once you have it to your liking, flow a drop or two of thin CA into the cuts and sand off the excess. Foam wings that are sheeted with balsa can have twists removed with the same type of cutting and shimming.
I was shown this method of straightening a twist in a fuselage back in my R/C sailplane days. Those built up wood fuselages back then were much tougher and stiffer and this method worked well. It can be done at anytime during the construction, and really even correcting a finished model that has had a twist work it's way in.
Another thought is to just make a cut below the stab parallel to it on both sides. You can shim the cut on the low side of the stab the same way. Make the cut in the fuse wider on each side for more movement. No real need to cut a fuselage completely apart.
Type at you later,
Dan McEntee
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Is the model made with a water based glue?
(I am sure that you can join the dots if it is.)
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I find that they are no longer parallel (one tip of horizontal stabilizer about 1/2 inch out of being parallel with the wing
Dave
Looking at the plane from the top or from the rear ?
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from experience ,u need to get rid of the twist in the fuse ,remove top and bottom blocks split the former's as needed and re glue and then re install the blocks
i left a twist in my Big Job fuse and used the top block to hold it straight ,it was a soft block and with in about 10 flights it split the top block.
i replaced the top block and it has been working ever since
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I had this problem with a recent plane I built. Had to basically loosen the stab in the fuse (cut all the way around it) and reposition it.
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This is one of the reasons that I learned not to glue the stab in till the fuselage top and bottoms are installed and the plane basically covered with silkspan or CF and a feww coats of dope put on. This way the fuselage is now solid, then glue the stab in relation to the wing.
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Thanks. Got the empennage true to the wing by using the shim method suggested. Ready for finishing. See photos. Planning to paint fuselage banner red, and cover wing with Monokote in same color. Then want to add a vinyl graphic only on wing. Does anyone know a vinyl graphic supplier? Not looking for complex graphics covering most of the plane as seen on most RC planes.
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Here are the photos:
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Finished painting and covering the Enterprise-E, please see photos.
Dave
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I added the final colors to the Enterprise-E
Dave
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You do not have to do any disassembly or cutting at all, even after the model is finished.
While the fuselage is torsionally very rigid, it can be twisted, even after the plane is totally finished.
After all the paint dried on my Argus, the stabilizer was off by about 1/2 inch.
I made a simple fixture and realigned the stabilizer. Took about an hour to make the fixture from simple stuff in the shop.
Anyone can do it.
I wrote an article on the entire procedure, published in the Volume 2, Number 2, April 2008 issue of Control Line World.
If anyone is interested, I will post the article.
Bob Z.
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You do not have to do any disassembly or cutting at all, even after the model is finished.
While the fuselage is torsionally very rigid, it can be twisted, even after the plane is totally finished.
After all the paint dried on my Argus, the stabilizer was off by about 1/2 inch.
I made a simple fixture and realigned the stabilizer. Took about an hour to make the fixture from simple stuff in the shop.
Anyone can do it.
I wrote an article on the entire procedure, published in the Volume 2, Number 2, April 2008 issue of Control Line World.
If anyone is interested, I will post the article.
Bob Z.
I certainly would be, Robert.
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Hi, Bill - here is the article.
Bob Z.
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I routinely remove wing warps with the hot towel method. (wet, then into the microwave for 4-5 min.). I can see this same idea would take the twist out of a fuselage. If I even end up with a twisted fuselage, I'll use the hot towel before cutting up my plane.
Floyd