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Topic: Ok to leave freshly cut fiberglass unfinished? (Read 890 times) previous topic - next topic

Ok to leave freshly cut fiberglass unfinished?

We recently had Hydralift install a platform lift on the back of our 03 U320 38' tag.  This install required Hydralift to cut into the fiberglass of the rear engine door.  We knew this info in advance.  Unfortunately, they didn't have anything on hand to trim the fiberglass neatly so it's currently duct taped up.  Our plan was to go to Nacogdoches at the end of spring and have Xtreme finish the job.  My concern is water intrusion into the layers of fiberglass in the short term.  Is that a concern?  Thanks!
2003 U320 38' tag
2003 Green Jeep Wrangler

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #1 –
My concern is that the untreated ends of the fiberglass material may wick in water, leading to delamination.  Realizing that that fiberglass material is blended with epoxy (which should prevent wicking, I would think), I would still treat the open ends with a coating of epoxy to ensure sealing it.  Xtreme can grind that away if needed.
Dave Threlkeld
Researching before full-time RV retirement
Detroit Diesel fan

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #2 –
Just fiberglass or is it sandwiched (something, even an air gap between layers of fiberglass)? 

Any pictures?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #3 –
Quote from: OldJD –
My concern is that the untreated ends of the fiberglass material may wick in water, leading to lamination.  Realizing that that fiberglass material is blended with epoxy (which should prevent wicking, I would think), I would still treat the open ends with a coating of epoxy to ensure sealing it.  Xtreme can grind that away if needed.
Fiberglas will absorb lots of water, especially if polyester resin is used. Vinyl ester resins rather than polyester make it more waterproof. Best to use epoxy resin to seal the ends but only if it's not chopped strand mat. Chopped strand mat has starch that holds the layers together. Vinyl ester or polyester resins melt the binder but epoxy resin will not. So, don't use epoxy resin on chopped strand mat. Water absorbsion is a big reason for delamination. The glass fibers are themselves waterproof but resin fills all the spaces.

If you ever wonder what your FG is so easily damaged? It's because FT used a lot of chopped strand mat rather than FG cloth. If layer after layer of Fiberglas cloth is laid down, coated with epoxy resin and then the excess is squeegeed off, the result is ultra strong and will withstand lots of impact abuse. This is known as a high fiberglass to resin ratio. Laying one layer after another is a very time consuming job. Long hours and low wages was the big reason Formosa (China) made such great hulls on their boats. Chopper gun boats gave the American boat building business a bad name back in the 1960's.

Here is a site with an explanation and photos of what the differences between mat, cloth and chopped strand mat are: Chopped Strand Mat - Fiberglass Warehouse After viewing the site, it's easy to tell what you have.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #4 –
Quote from: wolfe10 –
Just fiberglass or is it sandwiched (something, even an air gap between layers of fiberglass)? 

Any pictures?

Some parts are just fiberglass and some are sandwiched in between some hard foam.

I took a pic, but can't see a way to attach it to this post without hosting it on an external website.... I'm being prompted to enter a URL.
2003 U320 38' tag
2003 Green Jeep Wrangler

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #5 –
Quote from: Pierce & Gaylie Stewart –
Fiberglas will absorb lots of water, especially if polyester resin is used. Vinyl ester resins rather than polyester make it more waterproof. Best to use epoxy resin to seal the ends but only if it's not chopped strand mat. Chopped strand mat has starch that holds the layers together. Vinyl ester or polyester resins melt the binder but epoxy resin will not. So, don't use epoxy resin on chopped strand mat. Water absorbsion is a big reason for delamination. The glass fibers are themselves waterproof but resin fills all the spaces.

If you ever wonder what your FG is so easily damaged? It's because FT used a lot of chopped strand mat rather than FG cloth. If layer after layer of Fiberglas cloth is laid down, coated with epoxy resin and then the excess is squeegeed off, the result is ultra strong and will withstand lots of impact abuse. This is known as a high fiberglass to resin ratio. Laying one layer after another is a very time consuming job. Long hours and low wages was the big reason Formosa (China) made such great hulls on their boats. Chopper gun boats gave the American boat building business a bad name back in the 1960's.

Here is a site with an explanation and photos of what the differences between mat, cloth and chopped strand mat are: Chopped Strand Mat - Fiberglass Warehouse After viewing the site, it's easy to tell what you have.

Pierce


Thanks for that detailed and informative post. Unfortunately I can't tell from that web site which one I have.  When I get a moment I'll do some more research and see if I can make sense of it. 
2003 U320 38' tag
2003 Green Jeep Wrangler

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #6 –
It won't hurt to get some epoxy, maybe 30 minute type for some working time.  Clean off the duct tape residue. Mix up a batch and cover the cut edge, don't worry about getting it on the factory finish.  Let it cure up.  When it firms up but before it gets hard put on another layer.  When you get to Xtreme they will grind it all off anyway.  All you want to do now is seal it up and stabilize the cut edge. Don't use caulk or especially silicone.  It will just make repairs harder.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #7 –
Yeah I agree wouldn't be a bad idea to seal it up with some epoxy. there's some really good epoxies and caulk tubes that you can buy that mix as you squeeze it out, and that was seal it up just fine.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #8 –
If you are eventually taking it to Extreme to be repaired. Why don't you call them and ask what to use? It might cost you less down there if you use the right stuff here. Jmo 8)
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #9 –
Quote from: stump –
If you are eventually taking it to Extreme to be repaired. Why don't you call them and ask what to use? It might cost you less down there if you use the right stuff here. Jmo 8)

Yes, I had that same thought after I posted up this question.  I tried to call them, but our cell reception was flaky and they couldn't hear me well enough.  So I tried using skype, but by then they were gone for the day.  Yesterday was a travel day and now after sleeping on it, I'm rethinking my options.

Currently I'm waiting to hear back from a local boat shop to see how much they will charge to fix it.

The list of repairs keeps adding up and I'd rather just get this taken care of now.  We're not going to be in Texas for 2-4 months.
2003 U320 38' tag
2003 Green Jeep Wrangler

Re: Ok to leave freshly cut fiberglass unfinished?

Reply #10 –
A local fiberglass repair shop has given me an estimate of $200 to fix it.  No rain in the forecast till then, so hopefully all goes well.
2003 U320 38' tag
2003 Green Jeep Wrangler