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Author Topic: Repairing clear finished carbon SIC sup  (Read 907 times)

Ananda

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Repairing clear finished carbon SIC sup
« on: August 03, 2020, 07:13:26 PM »
Hey Friends,

I'm looking for advice here on repairing my 14' SIC Bullet. It's a custom board that was made as the prototype for the original V2 later produced in Taiwan. It has a number of dings taped up, but got a bigger one recently that deserves a more robust repair. I've done fiberglass repairs before and painted over them. On this board though the finish is clear, see attached photos. I'm seeking to source carbon fiber mat from Gorge Performance. I'd like to maintain the same or similar clear finish if not too difficult.

My questions:
1) What is the appropriate clear epoxy to use?
2) What is the appropriate finish to apply over the epoxied carbon?
3) Does the board being "clear" suffer from UV degradation? The ding in the photo was from a minor fall in the water and my knee hit the rail (pretty light) and caused that. No scrape or bruise on my knee. Seemed to me as if the board had become more fragile possibly due to years of wear and tear from use I suppose.

Thanks for any help or advice.


 

TallDude

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Re: Repairing clear finished carbon SIC sup
« Reply #1 on: August 03, 2020, 09:32:52 PM »
Pretty easy repair. Make a stencil of the SIC decal so you can paint the area you sand out, back on. White is an easy match for the decal. It looks like 3K plain weave CF. Pretty standard and you only need a tiny bit. You can use a small piece of EPS foam to build it flush with the surface or use Gorilla Glue and spray some water on it to get it to expand more. The Gorilla Glue is probably easier.
Sand the hot coat down about 1" all around the hole edge first.
Then fill the hole with foaming glue. Let it dry and sand it flush with the surface. Try to maintain the curve of the board rail.
Mask off your patch area so the excess epoxy doesn't run all over your board.
Then paint the foam black with just some water base craft paint. You will see a little bit of white through the CF if you don't paint it.
Cut your piece of CF with oval shaped ends along with a couple of pieces of 4 or 6oz E-glass to lay on top of the CF. The E-glass pieces should be a little larger than the CF so they lap over the edge of the CF.
Mix up some 2-part epoxy  (Resin Research UV or equal) and apply it with a small (1" or 1 1/2") throw away brush below and above the CF patch piece. Make sure the CF is fully wetted out.
Let cure 24hrs, then sand smooth. Once you start to see a little grey in sanding, stop.  That means your sanding into the CF and you don't want to do that too much. Use masking tape, drag the sticky side over your sanded patch to remove all sanding fragments.
Now coat it with the same epoxy one more time. Just brush it on and let it cure 24 hrs.
Remove the masking around your patch and do a final sand to smooth it out. It's more sanding than you think. Be gentil.
Now use you stencil and repaint the sand part of the decal. Probably semi-gloss white in a spray can.
Finish it off with some clear coat acrylic gloss from a spray can over the whole general area to blend.

Here's an old repair that is kinda similar. I didn't paint the foam black so you can see the white foam through the CF.
https://www.standupzone.com/forum/index.php/topic,21819.0.html
« Last Edit: August 03, 2020, 09:39:44 PM by TallDude »
It's not overhead to me!
8'8" L-41 ST and a whole pile of boards I rarely use.

PonoBill

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Re: Repairing clear finished carbon SIC sup
« Reply #2 on: August 04, 2020, 06:59:01 AM »
What talldude said. And in answer to your last question, both time and UV damage clear carbon somewhat, not as badly as it damages kevlar where it actually destroys the fibers, but the epoxy resin will become brittle. Painted boards degrade less, though all boards lose strength and flexibility over time.

Clear finished boards can be made with an epoxy that has clear UV block mixed in. It's not 100% block--few things are, UV penetrates fairly well--but it's better than plain epoxy which doesn't block much UV at all. There's no way to tell if your board was done with that other than a pervasive yellow cast to the epoxy in extreme cases which your board does not appear to have. I just repaired some cracks in my old Chinese hollow F16 that I traded to Joel Yang. It's an old board that was fairly brittle to start with.
« Last Edit: August 04, 2020, 07:16:40 AM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Ananda

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Re: Repairing clear finished carbon SIC sup
« Reply #3 on: August 04, 2020, 04:57:33 PM »
Thanks guys. This is perfect!

tarquin

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Re: Repairing clear finished carbon SIC sup
« Reply #4 on: August 19, 2020, 02:05:16 PM »
So a prototype board? Not painted. Who knows what the construction is. Which is why it dinged easily.
 1 epoxy is epoxy. They are all compatible. It depends how much you want to spend.
 2 good question not one many ask or think about. A 2 part polyurethane marine varnish is great for coating and adds UV protection. If you have a clear coated carbon board you have to consider Mantince!
 3 Yes massively. Both epoxy and carbon break down with UV. That's why the  brushed carbon look started.

PonoBill

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Re: Repairing clear finished carbon SIC sup
« Reply #5 on: August 19, 2020, 07:37:20 PM »
epoxy, yes, carbon fiber, no. Lots of studies on this. That's a difference that doesn't really matter much, if the epoxy breaks down the matrix becomes weak even if the CF is unaffected. But CF itself is one of those things that will be around when cockroaches rule the earth.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

 


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