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Fixing Avistar Horizontal Stab

Old 05-22-2008, 11:55 AM
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ScienceisCool
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Default Fixing Avistar Horizontal Stab

I haven't been flying for a while and accidentally broke my plane's horizontal stabilizer when I stepped on it in a drunken stupor. I can order the new tail kit from a local hobby shop and I'm just wondering what the best way to fix it would be? Right now I'm thinking of sawing off the old one, hollowing out where it passes through the fuselage and epoxying the new one in. Any other ideas? Can't wait to get back out flying!
Old 05-22-2008, 12:03 PM
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Default RE: Fixing Avistar Horizontal Stab

How badly is it damaged? Is it a built up framework structure, or a flat sheet of wood? It's possible that it might be repairable. Can you take picture of the damage and post it here??

Ken
Old 05-22-2008, 01:00 PM
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Default RE: Fixing Avistar Horizontal Stab

I stepped in the center of the right side of the stabilizer so about halfway down it is turned up about 20 degrees. It crunched pretty good at the time. I can take a pic of it but probably not until tomorrow as I'm going to the Astros game tonight. I don't think it's that bad but I have no experience building except for this one ARF so I'm a bit scared of trying to repair it myself.
Old 05-22-2008, 01:04 PM
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yetti831
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Default RE: Fixing Avistar Horizontal Stab

It sounds like it's repairable. I've been using my trainer as a sort of dare devil plane, and i cracked my horizontal stab the way you described. I simply used some six minute epoxy to glue it together. Just use some packing tape on the torn covering. You'd be suprised how much abuse a plane can take and still fly.
Old 05-22-2008, 01:05 PM
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Default RE: Fixing Avistar Horizontal Stab

I don't even think the covering tore, just crunched the balsa underneath.
Old 05-22-2008, 01:50 PM
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Nathan King
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Default RE: Fixing Avistar Horizontal Stab

ORIGINAL: ScienceisCool

I don't even think the covering tore, just crunched the balsa underneath.
That's very repairable. The Avistar has a built up horizontal stabilizer. Remove the covering 1/2" past either side of the break and take a picture. I'd bet you could totally repair it in two consecutive evenings. Balsa, being very soft, is an extremely easy wood to work with and requires very little experience to get a good repair. It's forgiving!
Old 05-22-2008, 01:58 PM
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Default RE: Fixing Avistar Horizontal Stab


ORIGINAL: Nathan King

ORIGINAL: ScienceisCool

I don't even think the covering tore, just crunched the balsa underneath.
That's very repairable. The Avistar has a built up horizontal stabilizer. Remove the covering 1/2" past either side of the break and take a picture. I'd bet you could totally repair it in two consecutive evenings. Balsa, being very soft, is an extremely easy wood to work with and requires very little experience to get a good repair. It's forgiving!
And in this case the repair is probably going to be a lot easier than removing and replacing the horizontal stabilizer.

Ken
Old 05-22-2008, 03:02 PM
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Default RE: Fixing Avistar Horizontal Stab

Hey Science - Long time no see.

Yep, fix the existing stab. Not all that hard or expensive.
Old 05-22-2008, 03:21 PM
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Default RE: Fixing Avistar Horizontal Stab

Hey Bruce, yeah, been some time since I've been out so I've got the itch. Already told the wife to inform the bank.

I'll get some pics in the next day or so when I have a bit of time.
Old 05-26-2008, 07:17 PM
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Default RE: Fixing Avistar Horizontal Stab

Ok, here are the pics of the broken stabilizer. While moving the plane around I realized the vertical stabilizer is broken at the bottom too. It looks like I could probably smear some CA glue or epoxy in there and have that done pretty easy. What should I do about the horizontal stab?

Thanks!
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Old 05-26-2008, 07:23 PM
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Default RE: Fixing Avistar Horizontal Stab

The damage is minor. Exactly as you said about the vertical stab, bend the stab back and place some glue between the cracked sections. Get some straight pieces of balsa and clamp the stab to it to make sure it's flat and straight. Recover with monokote and some trim sheets.

I agree with Ken, fixing it is easier than replacing it.

Make it straight and correct. The avistar's a nice flying plane.

Jim
Old 05-27-2008, 08:43 AM
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Default RE: Fixing Avistar Horizontal Stab

You should add some tri-angle stock at the base of the vert fin for support. Both sides of course.
Old 05-27-2008, 09:42 AM
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Default RE: Fixing Avistar Horizontal Stab

How big for the tri-angle stock at the base of the vert? I'm not an experienced builder so bear with me. Also, what do I do about the Horizontal Stab?
Old 05-27-2008, 10:01 AM
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Default RE: Fixing Avistar Horizontal Stab

3/8 or 1/2 inch triangle would probably be fine. If the stab is still tight in the fuse it won't need bracing. For the broken area of stab see if you can relocate the pieces in a straight order and a little CA should hold. Think about putting doubles on anything that functions like a spar though. The entire elevator may need replacing. Just cut old CA hinges (if used) and re-slot for new ones near the old ones. Do NOT reuse old locations.
Old 05-27-2008, 05:57 PM
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Default RE: Fixing Avistar Horizontal Stab

Not to interfere with all the good advice going on here vis-a-vis the repair and all, but the Avistar's horizontal stab and vert are bolted in place.... unless you glued them, you can get replacement pieces and bolt them back into place....


A
Old 05-27-2008, 06:14 PM
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Default RE: Fixing Avistar Horizontal Stab


ORIGINAL: a65l

Not to interfere with all the good advice going on here vis-a-vis the repair and all, but the Avistar's horizontal stab and vert are bolted in place.... unless you glued them, you can get replacement pieces and bolt them back into place....


A
Well, maybe. The ARF manual calls for epoxying the stabilizers in place and the RTF manual stipulates a bolt-on assembly. Can't tell from the pics which he has but I can detect a bead of something along the stab/fuselage joint I believe.
Old 05-27-2008, 10:06 PM
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Default RE: Fixing Avistar Horizontal Stab

This is the ARF model where the tail parts are epoxied in place.

Any suggestions on how to brace the spars for the horizontal part? I can just put a flat peice on top and bottom but it would stick up from the rest of it, like a bump.
Old 05-27-2008, 11:29 PM
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Default RE: Fixing Avistar Horizontal Stab

Scienceiscool,
Looking at your pictures I don't think the repair is going to be all that difficult. Since the wood never separated from itself at the break you can probably just glue it all back together. While keeping the two pieces together straighten out the horizontal stab and the elevator. Once you have it straight push the two halves together as tightly as you can. Now you need to get it straight while gluing it, clamp a straight piece of wood to the top, or bottom, of the horizontal stab while you apply glue. Place the wood away from the area you are gluing. With the stab straight wick thin CA into the breaks and let it set. Continue this on all the break areas. Once it's set you should be fine. Recover the stab and it will be plenty strong enough to fly. Heck, I've had worse hangar rash (damaged caused in the shop or hangar) that I've fixed in the same manner as what I just described.

Ken
Old 05-28-2008, 08:28 AM
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Default RE: Fixing Avistar Horizontal Stab

If you use a doubler, place it on the front/rear surfaces and NOT on the top/bottom.
Old 05-28-2008, 09:19 AM
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Default RE: Fixing Avistar Horizontal Stab

ORIGINAL: bruce88123

If you use a doubler, place it on the front/rear surfaces and NOT on the top/bottom.
Doublers can be useful in the right situation, but I try not to use them as they add quite a bit of weight. You can either do as Ken suggested or cut out the damaged spots at a sharp angle and replace. Using a heavily angled cut will eliminate the need for a doubler since there is more surface area to glue to. Yes, it's strong. I did this with my Joker (old pattern aircraft) wing and can still do snaps on downlines, outside loops, figure 'M''s, etc without it breaking. Do yourself a favor and use wood glue.
Old 05-28-2008, 09:29 AM
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Default RE: Fixing Avistar Horizontal Stab


ORIGINAL: Nathan King

ORIGINAL: bruce88123

If you use a doubler, place it on the front/rear surfaces and NOT on the top/bottom.
Doublers can be useful in the right situation, but I try not to use them as they add quite a bit of weight. You can either do as Ken suggested or cut out the damaged spots at a sharp angle and replace. Using a heavily angled cut will eliminate the need for a doubler since there is more surface area to glue to. Yes, it's strong. I did this with my Joker (old pattern aircraft) wing and can still do snaps on downlines, outside loops, figure 'M''s, etc without it breaking. Do yourself a favor and use wood glue.
This is called a "scarf joint" and it is indeed quite strong. It does require precise cutting and partial replacement. I was trying to avoid these 2 requirements. The angle of the cut IS required to be at a very acute degree for best results.
Old 05-28-2008, 09:30 AM
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Default RE: Fixing Avistar Horizontal Stab

http://en.wikipedia.org/wiki/Scarf_joint
Old 05-28-2008, 10:07 AM
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Default RE: Fixing Avistar Horizontal Stab

Bingo! I was thinking of the name, but couldn't remember it for the life of me. You saved me an entire day of wondering what the heck it was. Thanks!
Old 05-28-2008, 11:22 AM
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Default RE: Fixing Avistar Horizontal Stab

I don't think I have the right tools to make a scarf joint so I'm going to try bending it back into place and using thin CA to hold it. I just have to run by the hobby shop and get some straight peices for bracing and some clamps. Then have to convince the wife to let me buy some monokote and an iron. Is there any other way to recover it without resorting to that?
Old 05-28-2008, 11:44 AM
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Default RE: Fixing Avistar Horizontal Stab

No. Do it right with some monokote. You can use a full size iron in a pinch, but the covering irons are only $20. You could be back up in the air for under $40.

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