dumb fiberglass question?

[marquette]

i'm just getting ready to start to fiberglass the replacement plywood panels for my casting deck. do i prime the panels first or put the resin and cloth directly on the bare wood? secondly when i read to coat the panels first with resin then lay the cloth and then resin the cloth down does that mean to coat the panels and let the resin harden then apply the cloth and resin as a second coat or coat with resin apply cloth and re-resin all in 1 step? given the 11-15 minute working time of the resin doing it all in 1 step seems like a lot to do before the resin starts to gel. i know the beauty of fiberglass is that you can always grind your mistakes off and do it again but i would like to avoid that process as much as possible. i have no illusions that there will not be a certain amount grinding, sanding and repairing before i am done.

 

[gcboat]

Re: dumb fiberglass question?

No primer - . Rough up your lumber with some 80# paper first. Working like a mad man apply your resin, drape the cloth, add more resin as needed, roll it out with a mat roller to remove the bubbles. I always like to precut the material first, saves on waste.
Now this is using polyester? If you go the epoxy route the mat would be an option but it is always a good thing to use, especially on a load bearing surface.
Ondarvr is our resident glass expert. He'll have some better tips for you, but again I'd steer clear of the primer. Oh yea, wear throw away clothes and have a lot of acetone handy. Two people make the job a lot easier.

 

[ondarvr]

Re: dumb fiberglass question?

It's always better to put at least one coat of resin on the wood and then let it at least start to get hard before doing the glass work, otherwise resin can be sucked out of the glass and into the wood leaving dry areas. You still need to apply resin to the surface before laying the glass down though.

 

[marquette]

Re: dumb fiberglass question?

hi
does it make a difference strength wise if i let the first coat get too hard before i lay the glass and 2nd coat of resin? i'm going to be using polester resin. is there a way to slow down the drying time if i need to get the glass layer on before the 1st layer drys/harden?

 

[oops!]

Re: dumb fiberglass question?

you can use a little less mekp. (catylist)
but keep it in the 1.5 range......

(the catylist is mixed at 1.5 to 2.5 percent)....2.5 is hotter....(cures faster),
1.5 slower)

coat the wood with resin get the edges good, then wait till it is allmost hard....it will go from tackey to lightly stickey....then hit it with another coat of resin and add the glass..........rule of thumb when glassing.....saturate the glass....no more...no less....

 

[marquette]

Re: dumb fiberglass question?

hi
do i need to sand the fiberglassed panel before priming or just clean with acetone? i assume fiberglass is like any other surface that a good primer helps the paint stick better.

 

[oops!]

Re: dumb fiberglass question?

i would give a light scuffing, ive painted right over glass (no scuffing) the bond was crazy strong......but you see everything

 

[marquette]

Re: dumb fiberglass question?

hi
i started the fiberglassing this weekend and all the tips really helped. mostly all is going well except going around the edges. i am using 1/2 in thick panels. my plan was to glass flush to the edge on the bottom of the panel and then when i glassed the top wrap the glass around the edge about 1-2 inches to get a good water tight seal on the edge of the panel. i could not get the glass to stay tight against the edge. i would work it tight against the edge and then the top and bottom surfaces and then it would just pop off the edge. at first i tried wrapping the main piece of cloth from the top of the panel. after that didn't work i ground the edge off. wipped it down real good with acetone and tried using a 3-4 in wide strip going down the edge. same result. finally i put about 3 coats of resin on the edge smoothing it down between coats and the fiberglassing the top and bottom surfaces even to the edge with no wrap around. it looks great but i am a little leary about how waterproof the edges will be in the long term. does anybody know how to get the glass to stay tight to the edge?

 

[Mark42]

Re: dumb fiberglass question?

I read folks here use a staple gun to hold down those pesky edges.

 

[ondarvr]

Re: dumb fiberglass question?

Glass doesn't like to bend around a sharp edge or tight radius, so all of the wood needs to rounded off before glassing. It can be stapled, but you typically need to use a lot of them to hold it tight.

 

[KnottyBuoyz]

Re: dumb fiberglass question?

I've had pretty good luck with 3M Super 77 spray adhesive for tight radius curves. There's also "Raptor Nails" plastic staples that work well especially when working on vertical or inverted surfaces. The benefit of the plastic is they can stay in the laminate and will never rust should water get in. I always pre-coat ply to prevent the wood from drawing the resin away from the layup. The other alternative is to vacuum bag the part which will give you void free extremely tight radius's (sp) (It's radii isn'it? )

 

[ondarvr]

Re: dumb fiberglass question?

The 3M glue does work, you just need to be careful and not use too much or it will interfere with the bond and weaken the laminate.