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 Post subject: Dry spots
PostPosted: Sun Jun 19, 2005 7:39 am 
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Joined: Sat Jun 18, 2005 12:14 pm
Posts: 8
I vaccum bagged my first board a few days ago (yeah baby yeah) & when I removed the peel ply there are one or two small "dry spots"

- How do I prevent this in the future? (My bag pulls between -0.6 & -0.9)
- How do I fix it now?

Thanks in advance.

Kerry


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 Post subject:
PostPosted: Thu Jun 23, 2005 4:21 pm 
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Joined: Wed Nov 20, 2002 1:00 am
Posts: 927
Location: rhode island
hi.
what units are on the vacuum gage?
I'm assumng you mean .6-.9 atmospheres or bars

was the glass completely wet out before sticking it in the bag?
do you check the bag for any leaks?
(how long can it hold vacuum if you turn off the pump?)

did you use a breather, and did the vacuum seem to pull the bag uniformly around the board?


the vacuum doesn't actually move the epoxy much.
it just squeezes the excess through the peel ply.
so if there are any dry spots before the bagging, there's a good chance it will still be there when the resin kicks.

.9 bar is a little on the high side.
too much vacuum can make the laminate a little dry,
excess vacuum can draw some air out of the core or solvents out of the resin.
these may be caught in the resin.

leaks in the bag suck in air that has to go somewhere.
mostly it travels around the board, but not necessarily.

as far as the fix goes:
there is probably enough cured resin, that you can no longer completely
wet out the dry spot.
I would sand through the area in question and laminate a small
overlapping patch of glass.

if the spots are less than 1"diameter,
the repair is more for cosmetics than structural need.
but you never know.

no worries,
-bill


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 Post subject:
PostPosted: Sat Jun 25, 2005 7:15 am 
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Posts: 8
OK questions first...

Yes - Bars...
Yes it was completely wet out
Yes there was one leak... I dont seem to have a dry spot where the leak was.
I have managed to get my bag system down to about 3 cycles every ten minutes.
I used peel ply only... and no it didnt pull completely uniformally (I think have a solution for this). To improve circulation in the bag I was thinking of taping a thin bathroom towell to the deck i'm not laminating. (I'm doing a two step laminting process in a plastic tube)

The biggest dry spot is right on the tail!!! About the size of a box of cigarettes.... @#%$. I used tacs on the other side of the board to attach the peel ply to the board and one of them pushed through (the board is 6mm a the tips) So this was the cause. Do i really need to sand all the fibre away and use a patch?? Wont the bond and material be too weak?

There were one or two other small dry spots (surface only) which I covered with a hot coat.

Thanks for he advice

Kerry


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 Post subject:
PostPosted: Sun Jun 26, 2005 1:09 am 
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Joined: Wed Nov 20, 2002 1:00 am
Posts: 927
Location: rhode island
hi keri,
regarding the fix:
It's not likely the dry spot will ever be structural, because you can
no longer wet out the entire laminate.

so you really have nothing to lose by sanding back to something clean
and sound.

if the patch overlaps the original lam. by approx. 1" all around
it should be able to carry sufficient loads.
but, since the dry spot is in the tip. there probably isn't much stress there
anyway.
so just about anything should work, as long as its water tight.

-bill


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 Post subject:
PostPosted: Sun Jun 26, 2005 6:25 am 
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Joined: Sat Jun 18, 2005 12:14 pm
Posts: 8
Thanks for he advice Bill, I'll give it a go :thumb:


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 Post subject:
PostPosted: Mon Dec 19, 2005 7:09 pm 
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Joined: Mon Dec 05, 2005 4:44 pm
Posts: 158
To stop dry spots roller out the peel ply when wet before applying the breather. You should not have to staple anything .http://www.racingfinish.co.uk


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 Post subject:
PostPosted: Mon Dec 19, 2005 8:29 pm 
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Joined: Tue Nov 05, 2002 1:00 am
Posts: 8737
dry spots £10 says you have concave on the base.....


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