Re: Bubbles in S-Glass layup

["Robert Harper" <rharper@xxxxxxxxxxxx>]

The amount of strength reduction is relative to the size of the bubbles.  
The larger the bubbles the weaker the layup. If you have very small  
bubbles and very thick resin, then the weakness should not be too bad.

Tips:
1. Work with small batches of epoxy. If it is over 60F, I would stay in  
the 6 to 8 pump range. If it is cooler, you may go as many as 12.

2. Work fast and alert. Make sure that you have hours of uninterrupted  
time to work. Don't have a couple beers while you are doing a layup  
either. Once you start, don't stop until you are done. Pour the resin out,  
spread it out with the squeegee in a somewhat thick layer. Then go back  
over the newly applied epoxy and press hard with the squeegee to force the  
epoxy through the glass. Start at the inside of the area and work out to  
the egdes.

3. After you have that batch done, start the next and work from where you  
left off to the next area. Overlap the new epoxy a little. If you can, use  
an new cup each time so that you don't contaminate the new batch with  
epoxy that is starting to go off. It will make the new batch start to go  
off faster.

4. Before you start the third section, go back to the first and squeegee  
very hard to force the bubbles out and remove the excess epoxy. If you  
have to, poke holes with a toothpick or a pin to let the large bubles out.  
If you leave excess epoxy on the glass, you can have a few things happen.  
It may end up a slight bit heavier than need be, the glass could "float"  
off the wood reducing the bond to the hull, and more air bubbls can form  
because of the thicker resin trapping them. The excess will also tend to  
run and make the job of fairing it back out a bear.

From here on alternate between putting on a section and removing the  
excess from the section two steps prior.

After all of the glass is down and the excess is removed, check the layup  
every half hour or so to pop the bubbles until no more bubbles appear.  
Remember that the time spent to do this step right will pay back ten fold  
later on.

I never have had a second hand but if you can get someone to help you by  
mixing when you are about to need a new cup, this will make the job go  
much faster and be much easier. You also have another pair of eyes to help  
look for those nasty bubbles. The first side is the least likely to have a  
lot of bubbles because a lot of the "blowout" will pass through the wood.  
The second side finishes the encasing of the wood and there is only one  
way for the "blowout" to go. Back under the glass or composite. Your will  
find yourself spending much more time killing bubbles and you may not get  
a beer break for some time. This is why some people like to use vacume  
bags but they do not work on convex surfaces very well.

On Tue, 26 Jul 2005 16:41:13 -0600, Steve Nichols <nic173@xxxxxxxxxxxxxx>  
wrote:

> I made my first major mistake during construction last night. Holy .....
> that s-glass is hard to wet out. This was my first go with s-glass on the
> inside of the transom and I was maybe a little casual as I had no  
> problems
> with the hybrid when doing the bulkheads. I think I applied too much  
> resin
> at once as I couldnât get rid of all the bubbles with the squeegee before
> the resin had gone off slightly which made it impossible to do.
> Do I need to ditch this piece and start again? The bubbles wonât be  
> visible
> as it is the inside of the transom but have I compromised the strength  
> too
> much doing this?
> Any tips to prevent a repeat performance?
>
> Cheers
>
> Steve



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