What glass for epoxy?

Joined
Jan 29, 2014
Messages
15
I'm ready to order my glass, but I keep reading conflicting ideas about what you can and can't use with epoxy. Everyone keeps saying you cannot use chopped strand mat because the epoxy doesn't break down the binder, or doesn't penetrate all the way or something like that. Yet every transom job I read about the person is using a 1708 and CSM sandwhich.

So, what is the best glass schedule for putting a transom back in place if you are using epoxy?
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: What glass for epoxy?

Read this. http://forums.iboats.com/boat-resto...l-do-i-need-fill-gap-hole-my-hull-640353.html Two of the most experience guys on the forum talk about the topic. Basically with epoxy you only need Cloth/Fabric and the epoxy resin to do the job. If you're doing a transom then 17-18 oz cloth, some cabosil to make some filler, and your epoxy and you should be good to go. Post up some pics and we'll be glad to help.

WelcomeAboard.jpg
 
Joined
Jan 29, 2014
Messages
15
Re: What glass for epoxy?

Thanks for the link, it touched on answering my question a little, but then the topic drifted. So would something like 1700 Biax be ideal for my application?
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: What glass for epoxy?

Yes, Bottom line is this. Epoxy is "Stand Alone" Resin and by itself is fairly strong. The Cloth used adds additional structural strength.
Polyester Resin by itself is very brittle and not very strong. It "Requires" CSM (Chopped Strand Mat) to "Bind" it into on homogenous unified resinous unit. And as with Epoxy the Cloth add additional structural strength. This link should help you with how to build a transom..."Fabricating Decks, Stringers, and Transoms"
 
Joined
Jan 29, 2014
Messages
15
Re: What glass for epoxy?

I've seen that post referred many times on here and it is great information. However, it is also a great example of the contradicting info I mentioned. He continually refers to using CSM and 1708 which has a CSM layer.
 

jbcurt00

Moderator
Staff member
Joined
Oct 25, 2011
Messages
24,829
Re: What glass for epoxy?

I've seen that post referred many times on here and it is great information. However, it is also a great example of the contradicting info I mentioned. He continually refers to using CSM and 1708 which has a CSM layer.
Depending on the job at hand, often the 3/4oz CSM stitched to the back of 1708 biax is insufficient, and 1.5oz CSM is used 1st.

The referenced stringer, transom & deck graphic has been updated to reflect that ^^^

I wouldn't consider it contradictory either, confusing perhaps if you aren't reading the details. If you use 1.5oz CSM before 1708 in EVERY instance, you aren't doing any harm anyway. Using a bit more labor to install it, a bit more money in CSM & resin, and a fairly minor amount of additional weight. Nothing problematic.

This info is based on using POLYESTER resin during the rebuild, not epoxy:
stringers-revised.jpg


Perhaps you have saved a previous copy, you maybe reading posts prior to 2/13 or because you've read it before you aren't reading the entire text of the revised graphic.

In the details, the CSM is used to cover the entire deck being glassed, the 1st layer is applied prior to installation. The 1708 is used for the tabbing:
DeckInstallation-1.jpg

The transom is covered w/ CSM prior to install, and once installed is covered w/ 2 layers of 1708 (no additional CSM) for outboard transoms. I/O transoms get 4 layers of 1708 after the initial pre-installation wrap w/ CSM:
TRANSOM3.jpg

Also note the mention that using CSM 1st is advised when layering over uneven, rough surfaces, like a fiberglass hull that's been ground.

You CAN use CSM w/ epoxy, it may not wet out clear, and it may use up more epoxy resin then you really needed to use to get the job done. At least 1 moderator uses CSM extensively w/ epoxy, w/ no problem.
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: What glass for epoxy?

The HE is ME!!!!

I tried to make it clear in the post that it is for POLYESTER and therefore consider it NOT contradictory. But...you bring out a good point and I've updated it to reflect the methods to be used for an Epoxy installation. Thanks for pointing that out!!!;)
 
Last edited:
Top