Pre-made fiberglass board (such as from McMaster) question

[Rachel]

I'm thinking about using some pre-made fiberglass board in my bilge project. I won't know for sure if I'm actually going to use it until this weekend when I get another look at things, but I have a question about it I'd like to ask now.

If I go the route of sealing off the after edge of my ballast pig (see "Battle of the bilge" thread), I think I'll use a piece of the pre-made (McMaster-Carr) fiberglass as the "back wall," mushing it in place with some thickened epoxy (mostly just to hold things while I work) and then tabbing and filleting it to the sides of the bilge with something like biax tape.

I figure that will be easier than trying to build a vertical "wall" of biax-mat, and also, I could pre-sand the board before it goes into the depths of the bilge and is still easy to work on.

My question (yes, I'm finally getting to the point) is whether there is any point in using one of the "better" fiberglass boards, or if the plain old polyester (green board) is just as good. Since it's already cured, is there any advantage to using the board that's made with Vinylester resin over the one that's polyester? I don't want to skimp at all if there's any possibility I'll get a better bond with the non-green stuff.

One related question: I see that the typical green is made with polyester resin, and that the premium (brown?) is made with Vinylester, but does anyone know what the electrical grade (that's the red, right?) is made of? [edited to add: I was looking in the wrong place and now see that the red, electrical grade also uses polyester resin] I have easy access to the red or the green (though I could always order any other type).

On a related note, did I understand that one of the other types was better for tapping than the green? (I'll probably tap the backing plates for my seacocks.)

I was hefting a piece of the red board earlier - it's surprisingly heavy.

Rachel

[Ceasar Choppy]

I have used a fair bit of it, mostly for my mast step and backing plates for deck hardware. It is heavy because it is quite dense which is why I like it for high stress loads.

McMaster describes it as a polyester grade industrial laminate.

The strength characteristics can be found here. It is the GP03

http://www.mcmaster.com/addlcontent/loa ... e=PRODTECH

Sounds like for what you are using it for, it doesn't necessarily need to be bulletproof since you'll be using it more as a platform for the epoxy and biax anyway (do I understand that correctly)? But then again, you can always use more weight in the keel area... :)

[Rachel]

Perhaps my question was a bit long-winded. I mostly wanted to know if, since it's a previously cured product, there would be any advantage to getting one of the varieties that's made with a resin other than polyester. I know that epoxy and vinylester bond better than polyester when you're using them in "fresh" resin form, but wasn't sure in this application if it would make a difference.

I realize, of course, that the bilge glass I'm bonding to is cured polyester, but if buying the pre-made board that incorporates vinylester (or epoxy if there is such a board) gives it any better chance of adhering well, I'd probably go for it.

OTOH, if polyester is fine, does using the green (regular) or red (electrical grade, I believe) make any difference for this project, or for seacock backing plates (maybe the red is better for tapping?)

Dang, now that's almost as long as my first post. Let's hope it's a bit more clear.

R.

[Hirilondë]

Whatever board you choose you will be making a secondary/mechanical bond to it. There will be little difference which ever board you use in regards to how well you bond to it. Scuff it up well, most all FRPs and related panels are smooth and shiny.

[Tim]

You'll get the same bond quality regardless of which product you choose. The secondary bond the epoxy forms will be equally as strong with pre-manufactured G10, "red" electrical polyester board, "green" polyester board, or the vinylester board. Epoxy is only a glue in this application, and we already know that it bonds very effectively to polyester (among, of course, many other things).

FWIW, the vinylester board costs just about the same as G10, so I can't see any reason to ever consider the vinylester.

All of these boards are heavy, dense, and fiber-rich, and all are constructed to high manufacturing standards. I don't think you'd find any practical difference between them.

Each of these panel products is constructed with very specific applications in mind, which is why there are so many fine distinctions between them. Most would work effectively in the sorts of applications we're talking about.

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[Rachel]

Thanks all. It sounds as though I could use the green or red that I have on hand for my bilge project.

As for seacock backing plates, is there a consensus that G10 taps any better than the green or red product? (I see that Tynage said G10 taps well, but how about the others?)

Rachel

[Tim]

Thanks all. It sounds as though I could use the green or red that I have on hand for my bilge project.

Be sure to put the red to port, green to starboard.

[Rachel]

Be sure to put the red to port, green to starboard.

I knew I could count on you all for the important details.