Help! How to repair a cracked foil wing?

[plummet]

Lots of good options suggested.

Key will be to ensure the moisture is out of the core before doing any repair. If you can't vac bag the moisture out leave it for a week or 2 in a warm place.

Here's a quick and easy fix.

Mount the wing vertical.
Wedge the crack apart a several spots with small pins.
Use epoxy (I use west system) heated up. It Becomes very runny when hot.
Poor in the gap.
Pull out the pins
Wipe of excess
Fold some plastic bag over the wing tip and clamp it.
Wait to dry,
Blend smooth.

Job done.

[OzBungy]

That's almost exactly what I did last night to repair a little split in the tip, except I used toothpicks.

I heated the foil with a heat gun then injected the resin with a syringe and wrapped it with packing tape.

[vakiter]

deathbed? how so ? any fatalities on this wing from this common problem, or is it just a weight problem?

[TomW]

deathbed? how so ? any fatalities on this wing from this common problem, or is it just a weight problem?

Sorry for that. I often refer to my repair jobs as patients. I meant the foil wing was done for, dead, if i had not fixed it with this invasive surgery.

[vakiter]

yeah i got that, i was continuing your pun. ! but why is it dead with the crack? why is it not ridable with crack and water logged?

[jakemoore]

I would do the same as SWO. The only thing I would add is get the wing nice and warm first and then do the repair in a cool room. This way as the cavity within the wing cools it will suck resin into the crack. If you do it the other way round it will probably blow bubbles at you.

How warm? I just don't want to set off the epoxy early.

[OzBungy]

...

Thanks! Sounds quite complicated, it could become a new hobbie. Would you share some photos/videos of the process you dealt with while fixing your gear? I'm curious...

I am just finishing off a repair to the split tip of my foil.

I actually split it about 3 years ago and repaired it with epoxy paste. It held up fine. During lockdown I decided to repair some fresh dings, remove the epoxy paste patches and reconstruct the tip and wrap it in carbon.

The process was as follows:
- Sand out all the loose bits of carbon and epoxy paste patches
- Rebuild that section with epoxy resin and chopped carbon fibre.
- Laminate a strip of carbon around the tip that binds the top and bottom edges
- The carbon wouldn't wrap around the tight corner at the trailing edge and I was too slack to do relief cuts so I simply wrapped the tip with a little piece of carbon.
- I vacuum bagged the whole thing with a vacuum cleaner storage bag. That worked very well.
- I sewed a peel ply sleeve that tightly fit the tip and held all the carbon together. Another thing that worked surprisingly well.

I just have to do a coat of epoxy and microballoons to fair out any lumps and bumps, then paint it white. So far it has come up very well.

The vacuum bagged bits were done to full cure overnight. The peel ply leaves a surface perfectly textured to take subsequent epoxy coats. I smoothed out the edge of the carbon and a couple of little wrinkles with 50 grit paper.

I did a coat of epoxy to fill out the surface of the carbon. I am waiting for it to set to form "green" epoxy. I will apply the microballoon coat and that will chemically bond with the green epoxy.

I used some super precise drug dealer scales to weigh out the resin and hardener. Most batches were about 2-3 grams. I used little silicone mixing cups that could be cleaned and reused. It made the whole exercise very mess free.

Original Split

Carbon wrapped around the tip overlapping top and bottom. The scratches are where I sanded a small wrinkle with 50 grit paper.

Oops! Missed a bit.

Peel ply sewn to fit the tip.

Vacuum Storage Bag. The white stuff is some scrap cloth to use as a breather layer.

[Herman]

I would do the same as SWO. The only thing I would add is get the wing nice and warm first and then do the repair in a cool room. This way as the cavity within the wing cools it will suck resin into the crack. If you do it the other way round it will probably blow bubbles at you.

How warm? I just don't want to set off the epoxy early.

I would be happy with a 4C temp difference between where it was being stored and where worked on just so that it does not blow bubbles which can cause voids which would allow water ingress. If memory serves the relevant gas law is :
[P1xV1]/T1 = [P2xV2]/T2. Where T is absolute temperature

[gigibianchi]

Thanks for everybody who replied!

[revhed]

LF impulse. it is a manufacturing defect

Yes have seen many L F wing delams, simply not made well!
R H