Heavy fiberglass mat - Page 2

gw204f · #11 07-10-2012, 10:55 AM

Don't use just the mat for closing your transom and making your bracket. It will take tons of time and resin to get the proper thickness and even then it won't be as strong as if you used 1708 or 1808.

You could use it, but I would also get some wide rolls of roven and alternate layers.

RidgeRunner · #12 07-10-2012, 01:29 PM

The CSM looks heavy. At least 1.5oz which is what the old school builders used to use (ie. lay one layer of CSM and then a layer of 24oz Woven roving into that.) CSM wasn't designed to be used by itself, the resin to glass ratio will be too high. Woven roving isn't as good as the non woven 1708 fabric due to the crimp http://www.vectorply.com/ri-101.html But not to worry, the CSM works great as a water proofer and can be used for the floor, hatches, and the like and the roving will be OK for reinforcement. Look at it another way, all V-20's were constructed using CSM and woven roving for the hull and stringers. The liners were done with a chopper gun and reinforced as necessary with roving.

RidgeRunner · #13 07-10-2012, 01:34 PM

Quote:

Originally Posted by gw204f

Don't use just the mat for closing your transom and making your bracket. It will take tons of time and resin to get the proper thickness and even then it won't be as strong as if you used 1708 or 1808.

You could use it, but I would also get some wide rolls of roven and alternate layers.

Yep, Or buy the 17oz. stitched fabric in wide rolls without the CSM and alternate that with the CSM you have, you would essentially have 1724 a little resin rich but still very robust.

jasoncooperpcola · #14 07-10-2012, 05:01 PM

Ok, thanks for the info everybody. Anybody need any csm?

So i will still need some 1708 for the bracket. But, with my bracket design it should be more than sufficient WITHOUT glass and resin. The glass and resin is just for a little more strength. I have already had an engineeer look at my drawings and i am already on overkill.

Is the csm any good for making an electronics box, and glassing a couple fishboxes?

Oh before i forget, does anybody need any csm?

tartuffe · #15 07-11-2012, 08:18 PM

By all means, use the csm in addition to the biax. If you plan to use polyester, you need the csm for waterproofing anyway. I would wet out my csm and then immediately lay a layer of 17 oz biax on top, roll it out, then repeat laying the csm then biax going in another direction. CSM is great for building thickness. Thats not a real heavy mat like I was imagining. Just make your design with nice big radii to make glassing easier.

jasoncooperpcola · #16 07-12-2012, 01:47 PM

I just realized my mistake. I said i needed 1708 and all i need is 17oz biax to go with my csm.

gw204f · #17 07-12-2012, 02:07 PM

On exposed surfaces, make sure your layup consists of one or more layers of CSM just under your finish coat of gelcoat/paint/etc. The CSM helps to prevent print-through of heavier cloth/biax and if you are laminating from the inside out, you will be doing your final sanding/grinding on the mat instead of on the long fibers of the cloth/biax.

jasoncooperpcola · #18 07-12-2012, 02:58 PM

I am understanding it now. Well a little bit. My main concern on the bracket build is how to attach my stringer extensions to the existing stringers. Right where i plan to put the extensions is a step in the hull. I thought it would be to my advantage but now am getting worried about it. I will take pics when i get home. Whatever width the stringers are apart is how wide my bracket will be plus a total of six layers of 3/4 ply (3 on each side) for a total of 4.5" plus the outside stringer width. Its gonna be a massive bracket.