New Fiberglass Adhesion

[Jamepc]

Is there anything I should do to get new mat/resin to adhere to existing fiberglass (besides sanding). Should the existing resin be chemically softened? It needs to be a strong bond because it's for the 4x6 engine mount block.<br />Thanks,<br />James

 

[snapperbait]

Re: New Fiberglass Adhesion

Clean the area very well with acetone..

 

[JasonJ]

Re: New Fiberglass Adhesion

Acetone. It doesn't really soften it, but it does clean the dust and junk off very well. Also make sure you really rough the surface up. 60 or 40 grit is a good thing. I used the grinding wheel on my 4.5 inch angle grinder to make the surface very rough. I would probably use epoxy for what you are doing. Its an even better bond, you should never have to worry about it again.

 

[BillP]

Re: New Fiberglass Adhesion

Sanding and wiping clean is the minimum you should do and will work fine for most jobs. For the wipe down, use acetone or styrene. Styrene is superior over acetone except for the drying properties. It picks up where sanding doesn't by chemically bonding the old and new resin. Use it when sanding is difficult or the surface is rough and you can't hit all the nooks and crannies. Styrene is the correct thinning material for poly res too.

 

[crab bait]

Re: New Fiberglass Adhesion

like as what JASON said... i'd only use epoxy.. just clean&go.. alittle sand paper wouldn't hurt.. prep goes along-long way..<br /><br />fresh polyester doesn't really like old cured polyester.. but epoxy loves the stuff..

 

[ThomWV]

Re: New Fiberglass Adhesion

Certainly only use epoxy, not polyester. Get the slowest set hardner you can and if you like for the first coat you can add up to about 20% acetone to the resin which really thins it out and allows, alone with the slow set, time for very good penatration of the wood before set. Then follow up with cloth, mat, or a second coat of raw epoxy if you like. This is also a good way to simply treat wood that won't be finished but exposed. As an example here is a picture of a Rocket Launcher I made that we use sometimes when we take the chair out (I have a permanent mounting plate in the deck that accepts the standard mount so I can switch). This one is Black Walnut followed by Epoxy for a sealer and then simple lacquer for a top coat and UV protection.<br /><br />

<br /><br />Thom

 

[BillP]

Re: New Fiberglass Adhesion

Don't be freaked out on thinking you HAVE to use epoxy. Polyester resin will work fine if you prep and glass correctly. That's why I mentioned styrene...those who don't use it won't have the best results (not even close). <br /><br />Don't get me wrong. Epoxy IS the best way to go if money isn't an issue. It bonds better, is stronger (lbs per lbs) and definitely sticks better on places you can't prep well. It also requires fiberglass mat specially made for epoxy (epoxy will not disolve the fiber bonding material in regular fiberglass mat). Woven roven cloth will work with any resin.<br /><br />Be very careful about using the slowest cure hardner on vertical surfaces (such as stringers). The resin will/can drain down and leave a dry and brittle glass job. Epoxy is harder to work with in this respect because you cannot adjust hardner ratios to match the work finish time. Stringers are "captured" by the glass anyway and bonding the new glass to the hull is where it is the most critical. If you want to ensure penetration to the wood give it a thinned coat like already mentioned.

 

[Peter J Fraser]

Re: New Fiberglass Adhesion

If you go to <www.westsystem.com> you will pick up some good info on how to prepare surfaces for glassing / repairs. The stuff is easy to work with also as I am finishing some structural repairs to my boat using their recommendations.<br /><br />Good luck.<br /><br />Peter