I am repairing a ding in my carbon foil. I've done lots of minor repairs but I think this one would benefit from wrapping a bit of cloth around the leading edge to do a proper refurbishment. That would allow me to remove the various filled patches from previous repairs.
I don't have any vacuum gear but I'm thinking it might be a good thing to cover the wrap with peel ply and clamp it to simulate the pressure of bagging and reduce any excess resin. It's more of a nicety than an essential part of the repair.
Do any of the experienced carbon and epoxy repairers on the forum have any opinions on this?
Select to expand quoteGorgo said..
I am repairing a ding in my carbon foil. I've done lots of minor repairs but I think this one would benefit from wrapping a bit of cloth around the leading edge to do a proper refurbishment. That would allow me to remove the various filled patches from previous repairs.
I don't have any vacuum gear but I'm thinking it might be a good thing to cover the wrap with peel ply and clamp it to simulate the pressure of bagging and reduce any excess resin. It's more of a nicety than an essential part of the repair.
Do any of the experienced carbon and epoxy repairers on the forum have any opinions on this?
Good thinking. I'd be surprised if it didn't work. The idea of clamping with peel ply would be almost identical to bagging it, letting the excess bleed out. 
Peel ply, breather such as paper towel, cloth etc. wrap real tight with packing tape, it's stretchy so applies a lot of pressure. This is how I do most rail repairs.
Peel ply is just 100% polyester fabric, readily available from any fabric place.
Thanks for that. I ground out the broken bits and old repairs and just finished rebuilding the shape with epoxy and chopped carbon.
I'll try laminating in the next day or so. Got to love lockdowns as a spur to tackle projects you've been putting off. :-)
make sure your packaging tape or sticky tape is sticky side OUT so it comes off easier
Not even the peel ply .... budget version = laminate normally then put a dry layer of 4oz glass cloth on. Wrap hard with electrical tape with about a 1/3 width overlap.
That pressure from a stretchy tape will ensure the resin gets through to the surface but not such that it needs to escape.
Advantage is glass over top will give it a little better abrasion resistance too.
Select to expand quoteMark _australia said..
Not even the peel ply .... budget version = laminate normally then put a dry layer of 4oz glass cloth on. Wrap hard with electrical tape with about a 1/3 width overlap.
That pressure from a stretchy tape will ensure the resin gets through to the surface but not such that it needs to escape.
Advantage is glass over top will give it a little better abrasion resistance too.
Thanks for that. I read that as the glass absorbs the excess resin and is left on the surface as a protective layer. I'll do a couple of experiments on that.
The chopped carbon and epoxy has cured and come up really nicely. My foil has a fairly thick layer of carbon around the edges. Once the damaged bit is cleaned off the underlying structure is looks sound. I suspect I could simply sand and paint the chopped carbon and go foiling on it.
I have to say I love love love my J Shapes foil. I use it almost every day and it has just short of 600 hours on it. Bashing it in to the sand has no apparent effect. Flat landing jumps gives off some alarming noises but no apparent damage. Full speed into a rock, not so good. :-(
I've been working on my foil during the lockdown and I'm approaching the end of the process.
I ended up wrapping the tip of my foil in carbon, and using a cheap vacuum storage bag to hold it all during cure. I did some tests and it held vacuum for 24 hours. I don't think it would be much good for doing a whole board with porous foam, but it was just fine for a hard object like a foil. The results look great.
I wanted to wrap the tip because most foils seem to have a separate top and bottom layer. Damage to the foil generally shows some cracking and splitting around the edge. I am hoping wrapping the tip in carbon with hold it together and be a lot stronger (and hopefully not end transferring the damage somewhere else).
The vacuum bagging community talk about very high pressure vacuum for doing stuff. The videos I watched and the instructions for my West resin talk about not having too strong a vacuum to avoid dry joints.
The Youtube videos talked about letting the resin partially cure before applying the carbon so it would stick, and then wetting it out from the top. I was concerned that those videos were talking about cosmetic carbon skinning and not something structural. The instructions for my West resin didn't mention that so I went for a normal wet out process. It worked fine.
I sewed a sleeve of peel ply that closely fit the tip of the foil. It absorbed the excess resin and held everything in position while putting it in the vacuum bag. When peeled off the surface was nicely textured with no bumps or wrinkles. I used some scrap quilt batting to absorb the excess resin.
I sprayed the carbon with a little 3M Super 77 spray adhesive. That stopped the carbon shredding. I moulded the carbon to the shape of the tip and the adhesive held it nicely in place. It was easy to remove the carbon so I could wet out the surface of the foil before reapplying the carbon and wetting it out and pressing it down with a plastic squeegee.
I bought some super precise scales from ebay, and a couple of tiny silicone mixing cups and stirrers. I could accurately mix tiny batches of resin and apply it precisely (smallest batch is 1.8 grams which is enough to cover the tip of the foil). The silicone stuff is easy to clean and reuse. The whole process is very mess free.
I didn't try laminating the tip with fibreglass. I didn't want the tip to end up too thick. The whole foil is carbon so it seemed appropriate to do it all in carbon. I have some old glass and carbon fins I can use to experiment in laminating layers around sharp corners.
Very much liking this carbon and epoxy work with a little vacuum and peel ply.
Wife and I were wind foiling yesterday and I managed to hit a rock twice, while my wife scraped over one and caused a wee scratch. Using NP Glide foils S and M sizes, we're relative beginners (long-time windsurfers), but loving it. Hers doesn't seep water, but mine does (in two places) so I thought I'd try a proper repair. I repaired my SUP using glass and micro-balloons and West Marine epoxy and it come up OK). Would one of those winter-clothes vaccuum bags (that you use a vaccuum cleaner to suck the air out) work do you think?
Also, what thickness (or weight) of carbon fibre sheet is reccomended, looking to get some from a model shop but there's sheet from 0.2mm thickness up to 2mm. Is it better to have lots of thinner layers or just a couple fat ones?
cheers
k.
See above and kiteforum.com/viewtopic.php?f=196&t=2407240&p=1108901#p1108901
I wouldn't bother going the full carbon repair unless there is a reason to do it. I did it as a learning exercise and something to do in lockdown. My foil had 500 hours on it and a few patch ups. It's such a good foil I wanted to refurbish it. It's fun and easy, if you do it right, and pretty expensive. There's a lot of bits and pieces to buy. They're not individually expensive but it adds up.
I did some practice runs on an old surfboard. It's now got a carbon nose. :-) I learned quite a bit doing that.
jk do you really need carbon? I'd suggest not unless you are replacing a large area of the skin. If its a chip or crack, 4oz glass.
Likewise with vacuum. You don't need it for small repair
(BTW a model shop won't be selling carbon cloth? They will be selling pre-laminated sheet? No good - carbon in your foil is used the same as fibreglass so you'd need a cloth like 200gsm twill weave most likely. But like a I said, doubtful its needed.)
Pics?
Cheers guys I have glass, just wasn't sure if this thing needed carbon fibre. The pics probably look like nothing happened (although I definitely whacked into something which felt hard) and I did try to poke them with a pin but it wasn't going through. I put some Araldite Epoxy mix in the holes but after I did that I still got water droplets leaking out the two holes marked. Worries they'll suck up / have water forced in hence reason inquiring about a wee glass patch.
any hints on this would be appreciated, don't really want to take it back to the foam as to build it up again would be difficult. My SUP job was on a flat surface.
I'd just fill. Araldite is not designed for continuous immersion and when filler is added to it likely too thick to get into those little holes.
I'd sand back to the base composite over a larger area to remove all paint(but not sand into the laminate) and look for cracks as you hit it hard.
If nil seen then just fill with your west and q cell
You can check for leaks by chilling the foil down (leave it out on a cold night, immerse it in ice water), then heat it in the sun or a warm room or heating duct.
Smear soapy water on the area and check for bubbles.
You should be able to see any cracks using a magnifier, or take a close up photo and zoom in on it. If you can see a crack it's probably a leak.
Realistically you need to sand or grind until there's no visible cracks, or groove the cracks to make a shape to hold the thickened epoxy. Just smearing on some epoxy and hoping is a bit optimistic.
Thanks guys,
I've got this as a Project for the weekend, I agree with you Gorgo on the epoxy, optimistic is an understatement (it was a mistake and I regret it). I'm going to sand it back until I've taken back all the visible damage and made a decent surface for the epoxy to bond to; along with lay down some mat. A friend got hold of some 0.2mm carbon mat (not sheet) for me, but time wise I might need to just use some fibreglass as I think Mark suggested.
cheers
k.
