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Vertical Fin snapped off

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Old 05-19-2012, 09:13 AM
  #1
FlyingGatsby
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Default Vertical Fin snapped off

I have an avistar and at the end of the season I rolled it over and crashed. Luckily it crashed in tall grass, and only the vetical fin on the tail broke off. It's a clean break, so it can be easily glued back on. My question is: Should I drill some holes into the fin, and put something like I dowel inside, to strengthin up the connection?
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Old 05-19-2012, 09:43 AM
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Default RE: Vertical Fin snapped off

It will work , but make sure you don't add to much weight it will change your center of gravity. I have found it easyer to repair the finn than the tail section. The more ridged you make something the more damage you get in a crash.
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Old 05-19-2012, 10:24 AM
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Default RE: Vertical Fin snapped off

should I just glue it back on with epoxy, or reinforce it?
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Old 05-19-2012, 10:46 AM
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Default RE: Vertical Fin snapped off

I have found that a good clean repair with Epoxy or wood glue will work better that all the reinforcing and build up you can do. Some people think the more glue you use the stronger it is but not true. I have also used Med. CA where you do not have to fill a gap. Just make sure you have it lined up when you glue it.
Larry K
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Old 05-19-2012, 05:07 PM
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Default RE: Vertical Fin snapped off


Quote:
ORIGINAL: FlyingGatsby

should I just glue it back on with epoxy, or reinforce it?
I've had to glue vertical stabs back on before on trainers, and I usually try to replace (or add) triangular stock between the fuse and the fin. Try to get right down to clean wood with rasps and sandpaper so the epoxy will soak in and bond. The triangle stock helps distribute the loads a lot better than even dowels. Make sure you cover and seal the joint with monokote as that area usually gets a lot of oil on it. Good luck and get back in the air soon!
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Old 05-20-2012, 02:58 AM
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Default RE: Vertical Fin snapped off

To add what Live Wire ad thailazer said, I'd like to 'accentuate the obvious' here. Please ensure that you use a clamp of some type.

I've seen too many glue joints fail because they were CA'd and then held in position for a moment with fingers, then left to cure on its own devices. On a joint like this, you need some pressure to ensure that there's a good bond between the two pieces.

On a fin, that's going to be difficult but it can be done. You could use a span of tape going from the tip of one stab, over the top of the rudder, to the tip of the other stab. Just don't be too agressive or the stab can be damaged too. Let this cure for a while. CA will stick almost instantly, that's true, but sometimes takes hours for a full cure depending on what you're using.

It should be a simple fix, and I had that problem with my LT-40 too, where it had just a butt joint. I reinforced it like thailazer suggested.

Just my $.02

Bob
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Old 05-20-2012, 08:21 AM
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Default RE: Vertical Fin snapped off

When you do your repair Get everything ready and do a dry run...Get your tri stock fitted and your fin in place and held by whatever method works for you..I like to use a couple of pieces of strip balsa and pin it to the stabilizer,one on each size making sure you have it square...I would use either epoxy or wood glue..I would pin the tri stock in place..You will need to clean up the glue that squirts out of your joints after assembly..Wood glue can be cleaned with a damp rag or paper towel and epoxy with alcohol on a rag or paper towel...Just be careful that you dont disturb the joint...Oh and firstmake sure you have removed the covering so that you are down to the bare wood if it is not that way already...If the wood is contaminated with glow fuel make sure to clean it of as best you can..Alcohol works not too bad for this...After you have finished your repair and recovered your plane make sure you rebalance becauce it will be a bit more tail heavy...You will need to move your battery forward or maybe add some weight to the nose...Good luck... PS It would be easier to help you with your repairs if you were to post a few pics...I dont really know how the fin fits or what the break looks like..I amjust guessing...Some fins help to hold the horizontal stabilizer on and it is very important that they remain funtional or you will lose your tail completly..
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Old 05-21-2012, 06:42 AM
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Default RE: Vertical Fin snapped off


Quote:
ORIGINAL: bikerbc

When you do your repair Get everything ready and do a dry run...Get your tri stock fitted and your fin in place and held by whatever method works for you..I like to use a couple of pieces of strip balsa and pin it to the stabilizer,one on each size making sure you have it square...I would use either epoxy or wood glue..I would pin the tri stock in place..You will need to clean up the glue that squirts out of your joints after assembly..Wood glue can be cleaned with a damp rag or paper towel and epoxy with alcohol on a rag or paper towel...Just be careful that you dont disturb the joint...Oh and firstmake sure you have removed the covering so that you are down to the bare wood if it is not that way already...If the wood is contaminated with glow fuel make sure to clean it of as best you can..Alcohol works not too bad for this...After you have finished your repair and recovered your plane make sure you rebalance becauce it will be a bit more tail heavy...You will need to move your battery forward or maybe add some weight to the nose...Good luck... PS It would be easier to help you with your repairs if you were to post a few pics...I dont really know how the fin fits or what the break looks like..I amjust guessing...Some fins help to hold the horizontal stabilizer on and it is very important that they remain funtional or you will lose your tail completly..
Here a pictures of the break. The vertical stabilizer helps hold in the horizontal one, but it broke right above the piece that holds the horizontal one.

http://s902.photobucket.com/albums/a...t=DSCF5994.jpg
http://s902.photobucket.com/albums/a...t=DSCF5997.jpg


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Old 05-21-2012, 04:34 PM
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Default RE: Vertical Fin snapped off

Thanks for the photos. That wood grain seems to have been cut in the wrong direction. It should have been vertical.

I recommend that you go back to posts 4, 5, and 6. Get some triangle stock and make a nice, tight, close fitting joint. You won't need a lot of glue or heavy wood. Run it the entire length of the broken joint. You can repair this and only add grams to the tail. Make sure to fuel proof it and if you like, finish it off with some monokote or just leave it as it is. The key will be that tight fitting joint and clamping.

Let us know how this comes out,

Bob
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Old 05-21-2012, 05:29 PM
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Default RE: Vertical Fin snapped off

Nothing wrong with the way the balsa is running at the broken section. The vertical fin on the avistar is stick construction not a solid sheet. Repaired a Tower Trainer with 1/4" tri-angle section to support the vertical fin on either side. Simple repair.

Jim
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Old 05-21-2012, 06:51 PM
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Default RE: Vertical Fin snapped off

Heres how I fixed mine on my Avistar.

I did sheet it with 1/16 Light Ply because I wanted to hide the CG weights inside while it was open.
The whole mess is epoxied. Not like it didnt need the tail weight anyway.
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Old 05-30-2012, 05:36 AM
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Default RE: Vertical Fin snapped off

Thanks For the pics..It is much clearer now..The fin has nothing to do with the horizontal stab so that makes it easier..Strip the covering back about an inch or so..You dont need to remove it just tape it back out of your way for now...Fit the fin back in the spot where it came from and see if you can get a good fit by wiggeling it in..You may need to remove a few little pieces that are bent and stopping it from a good fit..When you get a good fit take two long strips of about 1/4 by 1/4 balsa and go from the top of your fin to the outer edge of your horizontal stabilizer and pin the fin on square.. Now cut two pieces of 1/4" or 3/8" tri stock and fit them along each side of the fin..When you are satisfied all is looking good pull it apart and apply the glue..I would use 30 min epoxy but wood glue would probably do a pretty good job too..Clean the excess glue the comes out of the joint ..Wood glue with a rag dapened with water..Epoxy with a rag dampened with alcohol.. Check to make sure that it is still strait and square...After it has set sand it smooth and shape it a tiny bit then iron your covering back on..If you have any balsarite it mite be a good idea to put a coat of that on to help the covering to restick..If not and you are having trouble jut cut it off and use a new piece but when you cut it off dont score the wood undeneath or the finn will spap off again...If you want to strengthen the finn you can put perminant wires on sort of like the two 1/4 inch balsa strips you used two hold the fin while the glue dried..This really helps a lot...Just ask if you need more help...Good luck...Let us know how you are making out...
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Old 06-01-2012, 11:46 PM
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Default RE: Vertical Fin snapped off

Wow, I am learning a lot just by reading up on the earlier posts. First off, whilst balsa is a light wood and great for models, I am wondering about whether it is good material for a remote control plane that has to bear a lot of upthrust and stiff wind resistance. Maybe I'm wrong.
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