Opus fuz repair carbon or kevlar

[GeoffN]

Hi, I caught a wing tip on my last landing while flying my Opus 2m. Tbe wing is secured to the fuselage with a screw at the back of the wing and a tongue at the front of the wing ( see photo). The tongue has ripped out through the side of the fuselage.

I think the best way to repair it would be to grind the gel coat off around the fuz where the tongue sits .Place the wing wrapped in cling film in position and then wrap the fuz with either carbon tow or kevlare thead. But carbon or kevlar? od is there a better method? 

[Brett82]

Hi Geoff

I wont pretend to know the best way of repairing it but just thought I would point out that carbon and Kevlar are two very different materials with very different properties and uses.

Kevlar gives very little rigidity/stiffness but it gives enormous impact resistance. Its normally used with another fabric that offers the rigidity/stiffness, such as when used on kayaks. Kevlar is sandwiched between layers of fibreglass which gives  it some stiffness and the Kevlar gives it massive impact resistance against rocks. 

Carbon will give the stiffness you require so if it was me I would use a mixture of both but some may say it would be overkill. Just keep the carbon away from any aerials. 

Brett

[oipigface]

Hi Geoff,

        Before saying anything about the details, I’d like to ask a question: is the original structure glass fibre? That looks like a piece of (never been wetted) glass cloth hanging out there. If it is GF you could mend it with GF. If I understand the way the tongue works, there is quite a lot of area for it to bear on in normal flight, and there doesn’t seen to be much point in making the repair super strong (aka heavy).

       The reason I ask is because polyester resin is often used in conjunction with GF, and the epoxy resin usually used with CF and Kevlar may not be compatible with it. Your repair may easily detach from the original structure in the event of another unfortunate incident.

       Cheers

       John

         

        

[SilentPilot]

That dry Glass makes me wonder if it is an intentional "weak link" in the wing mounting chain.

Does the tongue look ok? No point doing a strong repair of the fuselage if the tongue is cracked!

 

Tony 

 

[GeoffN]

The fuz is all carbon fibre apart crom 4 inches of the nose. The tongue is ok . I think the dry glass may be from a previous repair.

There is a lot of stress on that part of the fuz so I'm going to wrap carbon and kevlar thread all the way around the fuselage at the tongue insertion point with the wing in position .Its the only way I can see of providing sufficient strength . Then slide heat shrink tube over it to squeeze out the excess resin.

Tow and thread on order.

[Phil.Taylor]

Yep - wrap it with carbon tows - stronger than Kevlar.

A little trick - start the carbon tow with a bit of cyano to fix it in place - then when set - wrap, and wrap - and epoxy - and wrap...

Phil.

[GeoffN]

Thanks good idea,  I've got in a mess before with wetted carbon sliding around .