fiberglass not bonding to wood

[mahend]

fiberglass experts i need help i built my new transom from exterior grade 3/4 inch plywood laminated togethor with pl adhesive and last yesterday glassed 1 side with csm and waxed poly resin , i did coat the wood first than csm and did a good wet out. it looked and felt great. when i took sander to the edge to get a couple of bumps ground down before i flipped it over to do other side i noticed the glass was seperating from the wood so i grabbed hold and peeled the whole thing off.....what did i do wrong? was it the waxed resin or should i have used acetone on the wood prior to glassing?

 

[oops!]

Re: fiberglass not bonding to wood

hi....sorry this took so long to get to ......

there could be a couple of reasons.....

did you dry the plywood first? even ext grade right from the store is not dry enough to glass.

the second thing....is you said you coated the the wood first?....did you wait between coating to let the resin weep into the wood? was the wood tacky when you added the glass? or was it wet on wet.

sanding the wood before glassing is a good thing.....and acetone on plywood will not do anything but suck some of the moisture out of it. we use acetone to clean areas that need glassing....but on a porous surface like wood....it wont clean at all.

 

[Woodonglass]

Re: fiberglass not bonding to wood

When you say you coated the wood first do you mean you coated it and Immediately applied the CSM or did you let it dry and then coat it again and laid the CSM??

 

[mahend]

Re: fiberglass not bonding to wood

i sanded the wood with 100 grit cleaned with shopvac and rag than coated with resin and immediately covered with csm and than wet that out, like i stated it was resin with wax from fleet farm, should i be using a better poly resin unwaxed or should i have let it soak into the wood first, i did let the ply dry in garage for 3 weeks before using but maybe still 2 wet

 

[produceguy]

Re: fiberglass not bonding to wood

What kind of ply did you buy?
Maybe you picked up some old resin.

 

[Yacht Dr.]

Re: fiberglass not bonding to wood

I think its the wax plus the application ..

I NEVER use waxed ANYthing until the final application of glass or coatings ( I personally do not buy waxed anything .. I will add the wax myself if needed ).

If you put Waxed resin to precoat your wood..and it cured before you could get the mat on there then there is your problem.

If you didnt miss your window of resin/glass .. then its an issue with your wood. Thats one thing about using EG grade ply without proper resin coating prep prior to glass apps... It can fail on your initial bond coat.

Got pics ?

YD.

 

[BWT]

Re: fiberglass not bonding to wood

First thing that came to mind, was the ply green treated?

 

[oops!]

Re: fiberglass not bonding to wood

When you say you coated the wood first do you mean you coated it and Immediately applied the CSM or did you let it dry and then coat it again and laid the CSM??

yup....thats where i was goin

If you put Waxed resin to precoat your wood..and it cured before you could get the mat on there then there is your problem.

If you didnt miss your window of resin/glass .. then its an issue with your wood. Thats one thing about using EG grade ply without proper resin coating prep prior to glass apps... It can fail on your initial bond coat.

Got pics ?

YD.

this is the only reason for the failed bond.

First thing that came to mind, was the ply green treated?

yea.....if its pt ply....it really needs to be dryed for a long time before it can be used......

the op stated after that he basically did a wet out and then glassed it.....so that means it has to be the wood.......unless the wet out was bad with huge micro bubbles of air, it has to be the wood.
even with a bad wet out....you still should have good enough of a bond with csm that it will cause some of the wood to fail at the bond line.

 

[Friscoboater]

Re: fiberglass not bonding to wood

I had that problem once. I was not using enough resin. The CSM soaked it all up and there was not enough left over to bond to the wood. What YD Wood and oops are saying is all correct. What I did was coat the wood with resin fist and mix it slow (means it takes longer to cure) so it soaks in. Then I put the CSM down and I never had that problem again.

 

[ondarvr]

Re: fiberglass not bonding to wood

You can't really use waxed resin to pre-coat the wood correctly.

You said you put resin down and then put CSM on top of it right away, this doesn't work all that well. Pre-coating means you apply the resin and let it soak in, it needs to at least start to cure before you apply more resin and CSM. If you don't wait then the resin either doesn't have time to soak in, or can be sucked out of the wood by the glass, neither is good.

You can't let waxed resin cure or the next coat won't bond all that well, so it's never used in this way.

 

[mahend]

Re: fiberglass not bonding to wood

ok i think the waxed resin is my problem as well as not letting it cure before glassing i will be ordering some unwaxed from us composites what do i want 404 or 435 ? and thanks again for all your help

 

[oops!]

Re: fiberglass not bonding to wood

im not sure of the stock numbers......just get un waxed polyester resin.....the cheap stuff !

the quote by ondarvr ....comes straight from the manufacturers of resin and gellcoat....follow these instructions.

You can't really use waxed resin to pre-coat the wood correctly.

You said you put resin down and then put CSM on top of it right away, this doesn't work all that well. Pre-coating means you apply the resin and let it soak in, it needs to at least start to cure before you apply more resin and CSM. If you don't wait then the resin either doesn't have time to soak in, or can be sucked out of the wood by the glass, neither is good.

You can't let waxed resin cure or the next coat won't bond all that well, so it's never used in this way.

i will expand on this for your ease of use.

sand the top resin from the failed bond off.. just the top stuff.....dont go too anal here.

wet out the wood using a 1.5 mekp catylization rate... brush or roll the resin on to the wood. then brush it in several different directions.
let the resin sit till it gets tacky....(just starting to cure or get hard) then add the scm and glass over it as per normal. make sure you use your resin roller to get rid of any air....the resin to glass mix you are looking for is 50-50....so not too much resin..

 

[Yacht Dr.]

Re: fiberglass not bonding to wood

ok i think the waxed resin is my problem as well as not letting it cure before glassing i will be ordering some unwaxed from us composites what do i want 404 or 435 ? and thanks again for all your help

You want the 435 lam resin .. the 404 is "tooling resin" ( 404 is for mold making where Heat transfer is an issue from the part to the mold .. hurting the mold itself )

Dont buy that cheap crap..

As far as Coating/ "Prepping" your wood with resin .. and how many coats .. depends on the wood you have ( many threads about marine VS. EX ply ). You have to apply the resin until the wood stops drinking it. If you try to lam some mat on wood that has not been properly prepped then you might encounter Issues with the Bond coat.

Got Pics please .. again ..

YD.

 

[mahend]

Re: fiberglass not bonding to wood

thanks yacht dr i will use your advise and please be patient i will get pictures of my 1971 crestliner muskie 17 soon, i work road construction so not much free time and only sat night and sunday to work on the tri-hull. she needs alot of work but thanks to all those on iboats i think i can handle it.

 

[Yacht Dr.]

Re: fiberglass not bonding to wood

i think i can handle it.

We know you can m8 .. ..

YD.