Help with fibreglass work

Wondering if anyone can help.
I am building a new engine box over the top of an indoard motor. Making it out of fibreglass and as I am new to fibreglassing i want to know if I have to use marine ply under the fibreglass or will any ply or timber do the job , as the finished product is not under the waterline.
Also is there any trick to making it stick to the timber or just glass over it and then flow coat over the top.
Any help would be great.

jimbo1's picture

Posts: 333

Date Joined: 22/12/06

I beleive

Thu, 2007-06-07 13:22

From what I am aware if your going to all this effort use marine ply, as even not below waterline will still get wet or soak up moisture eventually if exposed.

I think you can just glass straight to the wood, use a roller or brush and put down a coat of resin followed by glass matting and repeat process followed by your flowcoat.

No expert but thats what i would assume.

Try a google search you might come up with better info.


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Posts: 13

Date Joined: 06/12/06

Have done some work with a

Thu, 2007-06-07 15:58

Have done some work with a well known WA boat builder (fitting out electrics and mechanical gear), they did not use marine ply on there floors etc just gave it a good coat of resin top and bottom to seal it

Posts: 236

Date Joined: 04/06/07

Fibreglass work

Thu, 2007-06-07 16:12

You can glass straight to wood, make sure you have it very wet
on the first layer or you might have a problem with it sticking.
Make sure you dont have it too dry between layers or will laminate
and fall off. Round all the corners of the timber as mat dosen't
like going around sharp corners, use a angle grinder or belt sander etc, you can fill any holes bad edges etc with car bog before
laying up glass. Depending on how strong you want it depends on
layers and type of chop strand mat you use, a lower weight mat for the first layer will go around corners easier followed by 450 chop
strand, finish with flowcoat not gelcoat as gelcoat tends to go sticky
as flowcoat has wax added.


bruiser's picture

Posts: 148

Date Joined: 09/08/05

Great information

Thu, 2007-06-07 16:31

Tnks Jason. Always wondered how to do it properly. Reckon I'll still get very sticky fingers at some stage of the process however.

Posts: 483

Date Joined: 09/11/06

Thank everyone

Thu, 2007-06-07 19:04

Great help guys. I will give it a go and hopefully end up with a good job.
Just one more question - if flowcoat has wax can you put more than one caot of flowcoat ontop of each other?

Any day fishing is a great day !!

Posts: 236

Date Joined: 04/06/07

It's been a few years since

Thu, 2007-06-07 20:16

It's been a few years since I've done any fibreglassing, I think
you can put waxed on top of waxed but if in doubt put unwaxed
on for your first coat and finish with waxed flowcoat, best to
ask your supplier? I found when laying your mat the first few
layers are most important as to get rid of air pockects, get
yourself some small metal rollers which have a bolt thread
like roller on them and roll out the trapped air. Add a little
more catylst in these cold conditions too, most good suppliers
should be helpful, resin and matting is pretty pricey now best
not to buy in to smaller quatities, could be why glass boats
these days are getting on the thin side????