Stress cracks(?) in glass formed during constrution?

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Alex's picture
Joined: 03/25/2004

Am in the middle of building a board and noticed what look like stress cracks in the glass layer on the bottom. I used s glass on the bottom. The board has been on the shaping rack and not been subjected to any stress other than sanding which was necessary due to premature kick. Would too hot a resin mix cause this? Only the tail area seems affected so I plan to add a patch over the bottom of the tail which will re inforce my fin boxes and keep the skin sealed.

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TSaunders's picture
Joined: 03/19/2004

Are the cracks on the rail or actually on the bottom? If they are just on the rails it could be you are seeing the sanding marks or fiberglass threads. If they are on the bottom it could still be sanding marks. With the batch kicking off too early there is the possibility of having cracks but you would have had to kick it off pretty hot. Where it cracked did it yellow? Another sign of too much heat. Sorry about asking more questions then giving answers but without seeing the board it is hard to make a call.

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Alex's picture
Joined: 03/25/2004

Thanks for the response. The cracks are actually on the bottom back near the fin area. They show the optical distortion similar to a thread but appear to be cracks. No yellowing showing and I don't think I had a super hot resin batch, just one that went off a little bit before I was ready. Apparently this is not something that happens frequently.

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austins's picture
Joined: 03/19/2004

id be willing to bet its from when you sanded the laps. sometimes ill get them from my angle grinder scratching the bottom lamination. Austin S.

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KirkPutnam's picture
Joined: 03/18/2004

Alex do these stress cracks only show up when the board has a layer of dust on the bottom?

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Alex's picture
Joined: 03/25/2004

No, no dust effect. They run in one direction, are in a group close together and from one angle look like cracks and from the opposite angle look like weave lines in the cloth. I thought maybe this was something that happens but can be avoided by not doing something that I did.

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PatrickShannon's picture
Joined: 03/19/2004

Alex,

If you still have the roll of cloth from which the cloth was cut, check the area where the damaged material would have been on the roll. Sometimes a flaw in the cloth will occur at a regular point on the roll. Perhaps when the cloth was being prepared a spot was repeatedly missed or damaged. Sometimes these spots only show clearly after the cloth has been wetout. Have only had this happen a couple of times but might be worth checking out. Good luck.

Patrick

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platty's picture
Joined: 03/18/2004

Alex, You said you used S glass. With S glass you will see the weave much the same way as you do with Volane glass. Has the tail area got more resin on it because of the quick gell? If it does this could be what you are seeing.platty.

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