[Public-list] Epoxy Vs. Polyester resin

[Glenn Brooks]

I've heard three different comments about glass repair on old FG.  The 
first is that glass continually expires styrene from the resin/mat bond 
until the mass is chemically inert.  Sometimes takes 25-30 years to go 
inert.  Once inert, ie no styrene left in the FG resin, new resin will 
not adhere to the old because of lack of bonding agent ( styrene).  A 
year ago ( 2nd comment) a surveyor advised me to sand off a surface test 
patch and rub the exposed raw glass with FG solvent.  If the solvent 
created any stickiness in the glass, that meant styrene was still 
present and you could get a good chemical bond between old and new...  
All this made sense, except I've always  wondered if no styrene was left 
in the bond, what holds the boat together!    I didn't try the technique 
as I didn't buy the particular boat I was looking at.

Finally, along comes Dolce, and I discover rotted core in the aft deck 
and cockpit sole... So, decide to cut it our, fill and glass over... I 
asked a reputable, commercial FG dealer/repair shop the same question I 
asked the surveyor and you pose above.  He tells me the solvent story is 
nonsense and that glass over glass always works. Says the solvent story 
is an old wives tale and he had been selling FG and doing repairs as 
long as there have Norwegian Fisherman in Ballard--with FG boats--which 
he has as his shop has been a fixture in Ballard for around for 35 years 
or so... But that there are three levels of resin-- with low strength 
poly on one end, hi strength 'epoxy' resin on the other and a mid range 
formula in the middle.  His comment was go with the bonding strength you 
need and can afford for the application. Epoxy costs 2-3x that of polyester.

I went with Epoxy for hi strength deck repair( and reinforced 
deck/bulkheads joints etc) and poly for new battery boxes under the 
cockpit sole because of cheaper cost. I intend to take Dolce to Hawaii 
on the Single Handed Transpac and return and do not want picky little 
noises coming from behind the bulkheads when the North Pacific lands on 
top of the deck...  Epoxy is stronger and More is better,  I think.
Epoxy also seems to set up pretty fast during repairs and allows quicker 
re-application. 

So, I never tried the solvent thing, but probably will some time just to 
find out what the real story is... 

Does this help?? It's not really an answer.  But I suppose you couldn't 
loose much by testing a patch of your damaged rail with solvent to find 
out if it would get sticky and works!  Having done that much you could 
do an actual test patch with new glass over old , then beat it off with 
a hammer to see if it really adheres well.  If it doesn't come off, 
except in little impact fractures and pieces, then you would know for 
sure and not be out much!  

good luck

Glenn Brooks
Dolce


Patty J wrote:

>Katrina took my cap rail off and ripped some of my deck to hull joint.
>Does any one know what I should use to make my repairs...epoxy or
>polyester resin with the fiberglass.  I've already read Don Casey's book
>on the subject and I'm ready to start grinding but want to use the
>correct materials.  The only part that was ripped off is the deck part
>just under the cap rail and it looks to me like they used fiberglass
>mess and sheeting sandwiched together, so I suspect they used polyester
>resin, but not sure.
>
>Patty
>Timbuktu 461
>
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