Help with fiberglassing tips...?

[Drobie]

I'm laying glass cloth on a foam form. I haven't work much with fiberglass and wonder if anyone has some basic tips on using the stuff.

I have West Marine resin and 2 oz and am building a retrieval boat from plans I got from RCBM.

A photo is attached of one of the hulls I have to cover. The instructions say to apply the cloth on the bottom, overlapping the sides, then do the top etc.

Trying to keep air bubbles out of some of the contours I have to cover is what's difficult. There's a 1/4" wide keel that extends below the hull bottom so the cloth has to go up the side over and down the keel and across the hull.

I did one side and will probably end up sanding to eternity. One problem is I started to close to dusk and while I was working, the light diminished. Live and learn.

Anyway, tips beginning with the basics would be much appreciated.

[Climate]

One big thing is to not get carried away with the amount of resin you use. If you still see some of the weave of the cloth, you are ok. Do not try and get a perfectly mirror surface in one application of cloth and resin. Adding more resin will cause the cloth to "float" and this can lead to bubbles, pinholes, and the cloth not bonding well to a curve. You should have just enough resin to make the cloth disappear, but still have the texture of the cloth showing.
Use an old credit card to squeegee the excess resin to a dry area if needed.
If the cloth pulls away from a curve, it is too thick. Go to a thinner cloth and add a few layers if strenght is required.

Mix the West system EXACTLY as it states on the can. It is quite particular in its quantities and if mixed wrong will not be as strong as it could have been if mixed properly.
Resin exotherms quickly if it is in a deep mixing pot. A larger shallow pot is the best.
If you are using a faster curing resin, use a shallow pot to mix your resin, and have a glove on if you are holding the pot. The heat from your hand can actually make the resin kick off faster.

Just like painting, or anything else, practice is what makes you better.

[Jr Branham]

Doug,
Make sure when mixing your epoxy you mix the ratios in exact amounts...don't guess. Epoxy is more critical than polyester.
Protect yourself from the resins, wear gloves.
Thinner layers of epoxy cure slower than thicker layers. The resin in your cup will KICK faster than the layer on your hull. You can pour it out of the cup onto hull and buy yourself more time to work with.

Do you have to use only one piece to cover??? Can it be covered in two separate pieces? Two pieces of cloth can be made to look like one when the resin is applied. If you HAVE to use one piece you can mix some resin with a filler and apply to the keel to prevent air pockets from forming.

Good luck and enjoy
Jr. B

[Jr Branham]

Doug,
Also pre-cut all your cloth for the job before mixing resin (I hate this part too!!). Measure when everything is still dry. You might also have to cut some RELEIFS in your cloth in certain areas so cloth won't bunch up.
Jr. B

[Drobie]

Thanks, guys. The first hull cured overnight. Not a bad job but much room for improvement.

I think one of the mistakes I might have made is in trying to apply too big a piece of cloth. The hull is 36 x 7" and that's a lot of area to keep bubbles out of, especially since it also contains a lot of angles and corners (including that friggin' 1/4" wide keel that hangs down a 1/4".

Do you ever do the edges is one step and the flat areas in another? It means I would have to mix and cure 4 or 5 times, but if the finished product comes out better I have the patience.

Also, do you resin the whole piece of cloth you are working on at the time, or do leave a little on the edge dry and trim it off after the section has cured?

I have the West systems pumps, so the mix should be correct.

Do not try and get a perfectly mirror surface in one application of cloth and resin.

How do you actually get to the "mirrored" finish. Building up successive layers of cloth and resin? How many? The instructions on this project say do a 2 oz. layer and then a .5 oz layer for finishing.

Also, what about the spots that came out with too much resin? Do you just sand the heck out of them before putting the next layer of cloth on, or should I apply the second layer and then sand?

[George Pfeifer]

If weight is not a concern and you want a really nice finish, put on 7-8 layers of resin. And then prepare to do a lot of sanding. This is the way we do the Dumas Chris Craft hulls in order to get that "deep" finish.
An orbital palm sander helps a lot. Work your way through 100 grit paper to 2000 grit then polish it. The finish is great.
Here's another tip: Before you start cutting the cloth, and trying to work with it, steal your wife's hair spray, and give the cloth a good coat. Stiffens it a little and keeps it from fraying. Much easier to work with.
Also I typically do one surface at a time for the initial coat, butting the pieces up to each other at corners and edges. This will leave the corners a little thicker, but a wood rasp will take the excess off in no time.
Also, do not stir the resin when mixing it, this will introduce air bubbles that will ultimately show up as tiny white dots. Use 2 mixing pots and pour the resin back and forth several times to mix it, that will prevent air bubbles.
With West Systems you can put sucessive coats on in 4 hour increments without having to sand in between coats. If you wait much longer than that you will need to sand the surface before adding successive coats. Failure to do that will ultimatley result in delamination of the layers.
George

[Climate]

To get a perfect finish requires a bit of practice but it is not hard.
You will never get a mirror finish from an outside lay up. You need a mold. Even then the finished product will only be as good as the original.
You have the right idea with going to successive thinner layers of cloth. Keeping the resin a consistent thickness is the biggest factor.
Spread the resin so that the weave of the cloth just shows. It should look like a very small waffle pattern. If you do this right, very little sanding is needed. This is where most people make the mistakes. They try to add a ton of resin to get the surface smooth and then spend hours sanding all the excess resin away. Excess resin does not add more strength, it adds more weight. The cloth is what makes the strength. The resin holds the cloth together and fills all the little holes.
If you do it right, sanding these little "waffles" away is easy going and will give you a smooth paintable surface.