Poor fibreglass adhesion to plywood

kell 9

Cadet
Joined
Mar 11, 2011
Messages
20
I am building my transom and I got 2 peace’s of 3/4 marine grade plywood I am using fibertec polyester laminating resin and 1708 I can’t seem to get a really good bond I am pre soaking it it’s clean ect and I can usually pry it up and peel it off . Is this something to do with marine plywood ? It’s like it’s not absorbing the resin well it wants to sit on top when pre soaking almost right away it seems
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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47,099
Marine plywood and not treated, correct?

How old is the resin?
 

kcassells

Fleet Admiral
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Oct 16, 2012
Messages
8,553
Meaning did you wet it out and let it dry then lay glass?
Or
neighbors cat pissed on it
 

kcassells

Fleet Admiral
Joined
Oct 16, 2012
Messages
8,553
I thought I pre soaked it well
Enough maybe I need leave it on there thicker ?

you need to wet it out prior to glassing. Soaks into the wood. Let it dry.
Come back wet out again and lay glass.
If not wet out the 1st time to dry then wood and glass soaks up resin but creates a horrible bond.
 

stresspoint

Master Chief Petty Officer
Joined
Sep 19, 2022
Messages
871
this is the reason i use structural ply,
marine ply takes too much work to get the resins to adhere properly .

OP , you need to sand with 36 - 40 orbital sanding disc prior to laying up , "" do not wipe with acetone or thinner prior to lay up "" , dust down with ""dry"" compressed air then lay up..
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
26,942
Gee, mix in a bit less hardener and let the resin soak into the plywood for longer. I replaced my transom on a nice warm day and mixed maybe 3/4 of the hardener usually called for. It took hours to harden, but it soaked into the plywood very well.
 
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