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Old Aug 27, 2014, 08:18 AM
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United States, AL, Daphne
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Fiberglass Fuse Repair

If you have a sailplane fuselage that's broken completely in half just in front of the leading edge, what cloth would you use for a repair? Fiberglass, carbon cloth or Kevlar? I have varying weights of all three but not sure which one to use. I'll be putting the cloth on the inside to minimize the ugliness.

Thanks
Trey
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Old Aug 27, 2014, 08:41 AM
stop making sense
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It seems to me that you have a luxury problem, what is the fuselage made of?
Ah.. fiberglass, says in the title, I guess you could pick and choose what you like.
I would use the same material as the surrounding area of the fuselage, fibers at +-45* to the break.

tk
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Old Aug 27, 2014, 03:31 PM
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Bellingen NSW Australia
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A lot depends upon what you have in stock.
Some Uni-Carbon strips or carbon tow flattened and placed for and aft across the break would be good as well as the 45/45 oriented glass fabric as mentioned above.
Make the carbon as long as you can conveniently gain access to. I have even used this externally where cosmetic considerations were not important. It can be wet sanded and primed/ painted after in this case.
Be sure to de-grease with alcohol or acetone and sand with course paper before apply epoxy and re-inforcement.
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Old Aug 27, 2014, 04:16 PM
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Thanks guys! I've got some 2 oz. glass so I guess I'll put two layers of that with uni carbon tow underneath.

Trey
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Old Aug 29, 2014, 05:04 AM
dare to thermal
Mannheim, Germany
Joined May 2004
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You should use the same material for the repair as itīs used for the fuselage. If itīs made of glass use glass, if itīs made of kevlar use kevlar... Donīt use carbon ifīnot used in the entire fuselage. The keyword is scarfing:
http://temp.epoxyworks.com/wp-conten...14/07/Fig1.jpg
http://temp.epoxyworks.com/?tag=comm...erglass-repair

btw: 2oz glass is pretty thin. typically fuselages are mage of 3 layer of 5oz glass. ...
good luck
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Old Aug 29, 2014, 05:33 AM
Entropy is happening!
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Bellingen NSW Australia
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Quote:
Originally Posted by Bernd Brunner View Post
....................... Donīt use carbon ifīnot used in the entire fuselage. ...................
Why not?

And as for the scarfing bit, in a perfect world maybe yes. However, it is often very hard to get inside small model fuselages to repair them. Good repairs can be made without any join taper; ask me how I know!

edit:
In fact, a common fuselage repair is done by first gluing the jaggered broken halves of a break together with CA. Then reinforcing the join (inside and out if required), using epoxy, glass and/or carbon. Kevlar can be used if it is close to a 2.4 ghz receiver. No scarfing! I've done just this myself after receiving instructions and the plane has been flown hard each season for years since the repair.
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Old Aug 29, 2014, 07:52 AM
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I would do the scarf but the thickness won't allow much. It's a 2-Meter model and the thickness of the fuse isn't much more than 1/16". 3/32" if that. If I cut out the servo tray I can get 4-5" either side of the break with some cloth. I figured the carbon tow might stiffen things up a little.

Thanks for the ideas.

Trey
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Old Aug 30, 2014, 05:14 AM
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Originally Posted by Trey4U View Post
I would do the scarf but the thickness won't allow much.
If you think about it, it sure seems difficult to scarf a thin laminate, but I have done this to the outer nose cone on a Fosa, and it's pretty thin fiberglass and there is no space for extra layers on the inside.
I broke (and repaired) the nosecone three times, all three times at different places so the repairs was obviously successful.
I made the total repair about an inch or perhaps an inch and a half wide, over the crack. It was not visible on the outside when done and painted.

I first mounted together the break with thin CA, then I sanded on the outside with a sanding drum tool, so that the wall thickness gradually faded to almost zero thickness at the break. I used several layers of thin fiberglass weave at different orientations.
Then I sanded back to the original outside shape with a sanding block. The result is no material build up on the inside or outside, you have simply replaced old material with new material.
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Old Aug 30, 2014, 01:51 PM
Balsa breaks better
Thermaler's Avatar
Buchanan Mi
Joined Apr 2005
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Quote:
Originally Posted by Trey4U View Post
.... If I cut out the servo tray......
Thanks for the ideas.

Trey

After making the repair make a new servo tray that goes past the break if possible.
Broke my Falcon 880 twice in the same place before figuring this out. It is a carbon/glass repair that has taken a lot of abuse since the last repair in 1998.


Joe
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Old Aug 30, 2014, 11:08 PM
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Quote:
Originally Posted by Bernd Brunner View Post
............. Donīt use carbon ifīnot used in the entire fuselage...............
Quote:
Originally Posted by Jim.Thompson View Post
Why not?
It creates stiffness difference (and thus a stress riser) in the structure. In the repairs of full-size man carrying planes the aim is to replicate the original structure - nothing less, but also nothing more, same type of cloths, same fiber orientation, scarfing by peeling the cloths off layer by layer, etc.

But since we are talking about models, none of this is critical or even a matter of concern.
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Old Aug 30, 2014, 11:50 PM
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Bellingen NSW Australia
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Originally Posted by jkettu View Post
................, none of this is critical or even a matter of concern.
I would agree with that.
Witness any number of repair threads on these forums plus my own experience - a bit too extensive in that regard for comfort!
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