has any one tried thinned polyester to treat wood?

[Snotter]

If durable wood species were used the rest of the discussion would be moot.

Most likely, the wood that will be encapsulated in fiberglass in a production boat factory is going to be plywood and pine, both of which will be heavily cooked in a wood kiln prior to purchase. This discussion is geared more towards fiberglass production than to one-off, high-quality, custom boat construction.

 

[Cruiser1]

My understanding is that epoxy will bond onto polyester OK but polyester will not bond onto epoxy. I have only done one fibreglass job on my boat so far when I waterproofed some 5-ply gussets I had made to block off the lazarette openings into the cabin area - I store my fuel in the lazarette.

These gussets are on the top the lazarette partition and therefore are not likely to see a lot of moisture, so I was not overly concerned. An upolsterer who was doing some work next door to me at the marina said don't bother with epoxy just use polyester for waterproofing as that is what he uses for all bunk rebuilding work prior to upulstering - mainly in power boats I would think. Obviously the bottom parts of these bunk structures could get fairly wet. He said to use 10% acteone but make sure to mix the polyester resin and the acetone thoughly before adding the catalyst.

In 20ml of resin I added 2ml of acteone, mixed it, and then added 12 drops of catalyst (MEKP). I stuck with the catalyst ratio my local marine suppliers had suggested of 1.5ml (60 drops) of catalyst per 100ml of resin. 40 drops equates to 1ml of catalyst. I have seen recommendations of anything from 40 - 70 drops per 100ml of resin - obviously depending on a range of issues. I used 3 coats on the timber and it came up really well (looked like it has been varnished but without the lustre). The last coat took about 3 days to finally go off but I think that was due to 12 month old resin (that was in temps of 30 deg C during the day and 20 degree C overnight).

Just thought I would write that one up for anyone interested.

 

[UseDaGreyMatter]

The advantages epoxy holds over polyester is well known, However there are many applications where you simply don't need the extra strength and cost.

You don't need a 1/2 inch stainless steel lag screw to hang a picture, a finishing nail is more than strong enough.

Yep. My point EXACTLY!!!!

Doing the happy dance.


Boom cha ga la ga boom!:dance:

Barb

 

[Ross]

I find that counting hardener drops is a problem cause I lose count when i have to take my shoes off so I use a hypodermic syringe of 10 or 12 cc size and 1 to 2 % hardener.

 

[kenn]

When I refinished our mahogany rudder, I used epoxy, thinned maybe 10% with acetone, for the 1st coat. The second coat was straight epoxy, and the top finish was 2 coats of Epiphanes 2-part clear finish. That's been waterproof for 5 years.

Caveat - we trailer-sail, though the rudder has been immersed for up to a week continuously at times.

I think both polyester and epoxy give good results for boat structural work. I will say that I think epoxy is a bit more forgiving for a newbie to work with, and a bit less dangerous/toxic.

 

[Ross]

Epoxy versus polyester as pertains to toxicity. They are both toxic but by different routes. Do a study concerning and they will both scare the bejebbers out of you.