core replacement, epoxy test panels

[Restoration man]

I’m quite inexperienced at fiberglassing Ive done little bits in the past that’s gone fine, I’ve been reading on here for ages and watching YouTube etc , but I’m now replacing core in the front Deck doing job from inside,I’ve already ripped the core out so please don’t tell me to do it from the outside as it’s to late now , I have bought west system epoxy and the eu/ metric version of 1708 that’s called 600 x300 it’s stiched and sold as epoxy compatible, originally the inside skin looks to be just made of just csm very varied in thickness between 2 and 5 mm average seems to be about 3mm so I’ve done some test panels, 3 layers1708 seem to be about right, I’ve gone with 1708 as ive heard it builds thickness without having to put to many layers on , I’ve made up 4 test panels with 1/2/3/4 layers so I could get idea of thickness, I’ve found it very hard to fully wet the mat to make it opaque it really needed one hell of lot rolling with fin roller , on the test panel with 2 layers I couldn’t no matter how hard I tried make the fibers disappear , I’ve bought brand new epoxy to do the job but for these test panels I didn’t want to waste my new stuff so I used some epoxy I had opened about a year about year ago, not sure if that’s caused the problem? Anyway if you lot wouldn’t mind looking at my test panels and let me know what you think ,

 

[tpenfield]

Not bad . . . some wetted out better than others. The key to using stitched cloth, particularly the 600x300 (1708) cloths, is to wet out the underside of the cloth before laying it up to the core piece, as well as saturating the core piece with a healthy amount of resin.

As you roll out the cloth, the resin will be forced out from underneath and push all of the air out of the cloth.

By contrast, if you try to soak the resin from the outside into the cloth, the resin will trap air in the cloth and it will take a whole lot of working in order to get the air out.

 

[todhunter]

Totally agree with Ted. For 1708 layups o always flipped it over (mat side up) on a sheet of plastic and fully wet it out from that side. Then liberally roll on resin to where the glass will go. Then peel up your wetted out 1708 from the plastic, transfer to the work area, and start rolling it out with a resin-wetted nap roller from the center out to the edges. 1708 is thirsty and takes a lot of resin. Trying to force the resin down through the biaxial side is very frustrating and takes a lot of work.

Your pics don't look too bad...#2 could have used more resin.

 

[Restoration man]

Thanks for the reply’s ,I will def wet the back of the mat next time , one more thing ,I’ve seen in the west system literature it says to put a thin layer of epoxy thickened with cabosil down first before putting the first layer of glass on , is this a good idea ?

 

[kcassells]

I’m quite inexperienced at fiberglassing Ive done little bits in the past that’s gone fine, I’ve been reading on here for ages and watching YouTube etc , but I’m now replacing core in the front Deck doing job from inside,I’ve already ripped the core out so please don’t tell me to do it from the outside as it’s to late now , I have bought west system epoxy and the eu/ metric version of 1708 that’s called 600 x300 it’s stiched and sold as epoxy compatible, originally the inside skin looks to be just made of just csm very varied in thickness between 2 and 5 mm average seems to be about 3mm so I’ve done some test panels, 3 layers1708 seem to be about right, I’ve gone with 1708 as ive heard it builds thickness without having to put to many layers on , I’ve made up 4 test panels with 1/2/3/4 layers so I could get idea of thickness, I’ve found it very hard to fully wet the mat to make it opaque it really needed one hell of lot rolling with fin roller , on the test panel with 2 layers I couldn’t no matter how hard I tried make the fibers disappear , I’ve bought brand new epoxy to do the job but for these test panels I didn’t want to waste my new stuff so I used some epoxy I had opened about a year about year ago, not sure if that’s caused the problem? Anyway if you lot wouldn’t mind looking at my test panels and let me know what you think ,

The glass should be 1700 no csm on the back for starters if its epoxy 1708 if poly. which is it?
In any event looks good.

 

[Restoration man]

Hi I was using epoxy and 1708 didn’t think it was a problem ? , the 1708 I’ve bought it’s sold as being ok with epoxy as it’s got stiched on csm with no binder , I’ve seen hundreds of videos with people using this ??

 

[kcassells]

1700 no csm
1708 csm
csm is broken down by poly not poxy. I don't make up the chemicals. It'll
work but now you are wasting costly epoxy and the cost of 1708 being more than 1700.
I did the same mistake.
https://support.jamestowndistributors.com/hc/en-us/articles/360013707113-Can-epoxy-resin-be-used-to-wet-out-chopped-strand-mat-#:~:text=You can use epoxy to wet out CSM,,the cured epoxy to create a strong laminate.

 

[Lectro88]

So far you have been given top, sound advise.
I must admit, I have NOT used any of the new hybrid cloths such as 1700 or 1708.
I have played with Epoxy and CSM and it's "ok" not the best... not a fail.. just like I said ok. but it takes working and giving it time to sit and soak in.
Most of what I use is woven roven, or just plain cloth.
The one thing I don't think anybody brought out is.... Well TodH brought up plastic, peeling it off.
your test panels were done on wood,.. wood is thirsty too, and probably helped suck away from the back side. in other words starving what you really needed to feed.

For instance, I'm coating 4x8 sheets of plywood. it takes about 30-36 ounces to satisfy 1 side to where it stops absorbing and has that full resin look or gloss with no dry spots. it also depends on how hot it is and if the sun is baking on it to make it flow and draw in.
now once I have let it dry or cure and sand it, to coat that same ply smearing a final glass/glossy finish. and I'm using a 6" squeege, it only takes 3-4 ounces... Big difference.(not using squeeze, how much difference in epoxy consumption after primed.

 

[Restoration man]

1700 no csm
1708 csm
csm is broken down by poly not poxy. I don't make up the chemicals. It'll
work but now you are wasting costly epoxy and the cost of 1708 being more than 1700.
I did the same mistake.
https://support.jamestowndistributors.com/hc/en-us/articles/360013707113-Can-epoxy-resin-be-used-to-wet-out-chopped-strand-mat-#:~:text=You can use epoxy to wet out CSM,,the cured epoxy to create a strong

https://support.jamestowndistributors.com/hc/en-us/articles/360013707113-Can-epoxy-resin-be-used-to-wet-out-chopped-strand-mat-#:~:text=You can use epoxy to wet out CSM,,the cured epoxy to create a strong laminate

My csm is stiched to the mat so it ha

1700 no csm
1708 csm
csm is broken down by poly not poxy. I don't make up the chemicals. It'll
work but now you are wasting costly epoxy and the cost of 1708 being more than 1700.
I did the same mistake.
https://support.jamestowndistributors.com/hc/en-us/articles/360013707113-Can-epoxy-resin-be-used-to-wet-out-chopped-strand-mat-#:~:text=You can use epoxy to wet out CSM,,the cured epoxy to create a strong laminate.

Thanks for taking the time to reply to me , I’m getting very confused over this ,
Feel free to correct me if I’m wrong , as far as I’ve been led to believe the csm on the back of 1708 is stiched on and therefore has no binder to worry about dissolving?
That article is just talking about regular csm not 1708 (combi mat), I’m aware of the problems of using regular csm with binder in it but I thought 1708 was immune to this problem because it has no binder in and it’s the stitching that holds it together not the binder ? , not sure if the stuff we have in Europe is different to the USA ?

 

[todhunter]

Feel free to correct me if I’m wrong , as far as I’ve been led to believe the csm on the back of 1708 is stiched on and therefore has no binder to worry about dissolving?

That's my understanding too - that the mat used on 1708 does not have binder in it. But I exclusively used polyester resin on my restoration (no epoxy), so I can't confirm first-hand that it will work. Have you tried picking up the phone and calling US Composites or another glass supplier? I can say for sure that US Composites' tech line is very helpful, and I bet they'll put you on the right path.

 

[kcassells]

This how it was told to me a long time ago.

1708 Fiberglass

Which side goes down the shiny slick side or the rough glass side. I am putting this on the inside bottom of my boat and then the flooring will cover it up. Thank you for any help. Tex51

forums.iboats.com

 

[Restoration man]

Thanks for the reply’s I’ve made the decision based on what I’ve read from the comments on here to buy some normal biax 1700 no csm on the back, I will save the other stuff for another job I might do in the future , this job has been a lot of work so far and I don’t want to mess it up just for the sake of a few yards of material it’s not worth the worry , I hope it will wet out better than the 1708 as I had problems wetting that out on the small test patches , let alone on the 1 meter square I’ve goto repair
Thanks again to everyone who commented all your reply’s have been very helpful