What type of cloth for transom and stringers?

[lime4x4]

I'm going to tab the transom wood and stringers with biaxle tape. What type of cloth should i use for covering the transom wood and stringers? Biaxle cloth with or without mat or is just regular 10oz e-glass cloth alright? I'll probably get it from us composites since i'm going to try some of there epoxy resin.

 

[drewpster]

Re: What type of cloth for transom and stringers?

Chopped strand mat is generally used as a covering for areas that are exposed and are to be finished. The CSM will cover the weave of the roving underneath it and is more watertite than roving alone. You can go with an all CSM layup but CSM soaks a ton of resin. If you use roving under the CSM it will provide bulk and thickness and will save resin.
I think it depends on how thick you want the fiberglass layer to be. You can get biaxial/ mat combinations that have CSM woven to the roving layer. But CSM is still generally used as the top layer for finishing. If you sand the weave of the roving to make it smooth for finishing you defeat the strength of the roving by sanding in to the weave. If you gelcoat over an exposed roving layer the weave will print through the surface making it rough. Even a very thick layer of gelcoat can show the print or get too thick and crack.

 

[andgott]

Re: What type of cloth for transom and stringers?

But he is using epoxy - CSM is out-

i'm going to try some of there epoxy resin.

U.S. Composites has Biax that'll work fine- Most seem to use 1708- It's nice and heavy, so it builds fast. You can use lighter 1208 if you need more conformability. Both of them soak up some serious resin, too- So get plenty

-Andrew

 

[lime4x4]

Re: What type of cloth for transom and stringers?

according to us composites i would use less resin if u used biaxle 1708 with 8oz mat attached

 

[drewpster]

Re: What type of cloth for transom and stringers?

It is my understanding that the jury is out on the use of CSM with epoxy. I have heard that you should not use CSM with epoxy because the binder in CSM is not compatiable. I have also heard that modern CSM is made with a binder that IS compatiable. Which is right?
Of course you should go with what the manufacturer recommends, I dont make the stuff, I just use it.

BTW- The Mat used for 1708 and 1208 is standard CSM. Right?

 

[lime4x4]

Re: What type of cloth for transom and stringers?

this from us composites website about CSM

Fiberglass Mat
Chopped strand mat is very economical and offers good stiffness. However, for greater strength and a lower weight product biaxials and woven cloth fabrics are generally used.All the following mats are compatible for use with polyester resins and vinyl ester resin.

biaxle cloth with mat

Biaxial fabrics are compatible for use with polyester resins, epoxy resins and vinyl ester resin.

It's all confusing...lol

 

[Bob_VT]

Re: What type of cloth for transom and stringers?

What the heck it's New Year's Day so I will toss this in just to add to the confusion

http://www.westsystem.com/ss/chopped-strand-mat-epoxy/

 

[andgott]

Re: What type of cloth for transom and stringers?

This is a confusing subject- I've tried to research it, and I find lots of conflicting information. Part of the problem is a lot of the info out there seems to be more opinion based!

I have also heard that SOME of the binders may be compatible with epoxies- But most of the manufacturers and dealers won't give a definite thumbs up to it...

The U.S. Composites website says that the mat they sell is compatible with Polyester and Vinylester, but does not say epoxy. They USED to sell another CSM, that was stitched together rather than glued, but they don't make that any more.

Note that they never come right out and say that it isn't compatible with epoxy, though on their other products, they come right out and say that it is compatible with etsers and epoxy.

BTW- The Mat used for 1708 and 1208 is standard CSM. Right?

It depends- In some cases, yes- But not always. the Biax that U.S. Composites sells is stitched together.

I suspect that most CSM's are OK with epoxy (refer to the West Systems article linked above), but I don't like to take the chance if I can't get someone to say it's OK. Until then, I'll just use materials that I KNOW are compatible.

-Andrew

 

[ondarvr]

Re: What type of cloth for transom and stringers?

The West System article tells it like it is, the more important part is that using CSM with epoxy is sort of a waste of money and epoxy.

Epoxy doesn't need CSM for any reason, unlike polyester there is little or no benefit in using it. CSM will soak up a great deal of epoxy and won't add near the strength that a woven or stitched fabric will, so you may double or triple the amount of epoxy used and end up with less strength. This adds cost and weight, so while there may be a couple situations where you "could" use CSM, there really isn't a need for it.

 

[lime4x4]

Re: What type of cloth for transom and stringers?

I will be using biaxle and woven cloth. How do i determine what oz to use? I don't want to go to light

 

[toocanshan]

Re: What type of cloth for transom and stringers?

this may not be sponsored by the perfectionists, but i used woven roven that i bought off e-bay a while back (25 lbs. for like 15-20 $), and i went to the Lowe's and got FIBERGLASS RESIN out of the paint section and when i applied the resin to the cloth, it became hard and sealed what i wanted it to. i don't know if the resin was polyester, epoxy or some other stuff but i do know that it worked for my boat. i plan on using the remainder on my new boat for the floor and the transom. i just think that sometimes you should just let well enough alone!! it's like saying what paint should i use to paint my wall?? it all depends on how much you want to spend and how great you want your wall to be.. TOOCAN

 

[andgott]

Re: What type of cloth for transom and stringers?

The 1708 Biaxial will give you good strength and a quick buildup. You can use a lighter (1208) if you think that it needs to be more flexible.

9 or 10 oz cloth is a pretty good 'general use' cloth.

 

[redfury]

Re: What type of cloth for transom and stringers?

For the transom and stringers, I'd think that you'd want to go with 12oz at a minimum. It'll conform to corners a little easier than 17oz will, and it will also depend on how you decide to lay the fabric. I had considered laying the glass I had purchased ( 1708 biax tape 10 " wide with polyester resin as my choice ) at a 45 degree angle up and over my stringers, essentially causing the fabric to create an "X" on the top of the stringers. This would have made for a lot of pieces to lay up in succession, almost looking like the armor on the batmobile from the first movie. I figured it was too much work and would defeat having a bunch of long fibers running the length of the boat, so I opted to run individual 10 inch strips on either side of the stringer and then I capped it off.

As far as finishing epoxy, you'd just want to use a fine veil fiberglass as your last layer if you were going to gel coat it/paint it to get rid of print through as the pattern won't be as rugged as what you get out of 17oz fabrics. Of course, you could also make a fairing compound out of epoxy like others here have done...just don't let it get too hard before you start sanding it smooth

 

[lime4x4]

Re: What type of cloth for transom and stringers?

Well it's all in the engine bay. So it really doesn't have to be fancy. I was going to paint it with bilgekote 2 coats. I also that us composites also has CSM that is epoxy compatible but they don't have any stock. But they claim that there 50" wide CSM mat works great with epoxy.

Owens Corning has discontinued this item. We are continuing to look for other sources. We have found our brand of 1-1/2oz x 50" (cat# FG-10550) regular chopped strand mat wets out with epoxy very well and could be considered a substitute.

Resin requirements for 1.5 oz mat.


50" - Needs approx. 36oz resin per yard

 

[ondarvr]

Re: What type of cloth for transom and stringers?

There is no need for CSM with epoxy, if you use it you're wasting money and adding weight.

Why is it you think you need it?

 

[lime4x4]

Re: What type of cloth for transom and stringers?

I'm not using CSM. I decided to go with 1708 biaxle cloth for everything. I was just pointing out they some companies have a CSM that is for use with epoxy. I was thinking about using a little bit of CSM just for the top of my stringers where the motor mounts get bolted. The factory fiberglass was 5/16" thick there.