polyester resin ?

[GracieBell1]

Re: polyester resin ?

The point is that a lot of people on here think that the science fator is all that matters. And for most it does not. They just want something that will work as good or better than what they got. Not something that is so exact and put back with only the best possible product. Just because it works on paper does not mean that it is very practical. That is a big problem with engineers and math/science people. I think that instead of hammering me you should look at it from a practical perspective not "sciency". Most are not looking for such finite results but practical uses. Also, 3M and NAPA fiberglass resin state on the can that they can be used as a sealer. http://www.hares.net/boat/waterproofing.htm

 

[ondarvr]

Re: polyester resin ?

I don't like to get into these discussions with very good intentioned people trying to pass on what they feel is a common sense approach, but most of what you just said makes little sense and is based on nothing more than you having done one boat.

3M and Napa have no clue as to what's in the cans of resin they sell, they buy it from someone else and and put their label on it, Thomson's Water Seal is the best product available according their own claims and its junk.


Since I've only been doing this for a little more than 40 years, and I only get to talk with polyester chemists and engineers on a daily basis, I may not have a clue as to what I'm talking about, but here goes.

Resin coated plywood is sort of water proof, at least it is right up until its not. Polyester resin can be very brittle and has little strength on its own and the wood offers little support or strength when no glass is used. What you end up with 90% of the time is cracked resin that peels off the wood. This was one of the big mistakes made by boat builders in the early days, it looked good for a few years (sometimes), but long term the failure rate was very high, just read the threads here on how poorly resin coated wood does in the real world.

There is no speculation on what thinning does to resin, just read the sticky at the top of the page on thinning epoxy, which is far stronger and much more water resistant than polyester.
The physical properties drop like a brick, if you notice the water resistance drops off quickly also. Plus preventing rot has nothing to do with penetration, it has to do with encapsulation.

Will you get away with using some of the non recommended methods, frequently yes, its sort of like driving drunk and crossing the center line. I know people that have driven drunk for many years and not been in a wreck or stopped for it. Does that mean its safe and recommended?

 

[westexasrepublic]

Re: polyester resin ?

Will you get away with using some of the non recommended methods, frequently yes, its sort of like driving drunk and crossing the center line. I know people that have driven drunk for many years and not been in a wreck or stopped for it. Does that mean its safe and recommended?

I THINK THIS THREAD JUST COMPARED USING POLY RESIN TO DRUNK DRIVING........

 

[ondarvr]

Re: polyester resin ?

Please understand I'm not comparing the seriousness of each, only the thought process behind thinking that because it was done a few times and the results "appeared" to be OK, doesn't mean its actually a good practice.

 

[westexasrepublic]

Re: polyester resin ?

but as long as we agree this thread is getting rediculous on the science of using polyester resin.

 

[drewpster]

Re: polyester resin ?

Using polyester resin to coat wood will help keep it from rotting as long as it never cracks or wicks water. (poly cracks and wicks water) Using epoxy to coat wood is better because it is less likely to crack. (assuming you coat it enough and use good epoxy)

But neither method has ever kept me from getting drunk.

 

[Greg Mrozinski]

Re: polyester resin ?

But neither method has ever kept me from getting drunk.

That's our boy! Nice!

 

[Yacht Dr.]

Re: polyester resin ?

There is one drawback to using epoxy to seal your wood ( transom or stringers lets say ) and that is that your gonna Have to use epoxy Thoughout the lam process.

Epoxy is way more expensive and at least for me not needed.

As far as "sealing" the wood .. simple EX middle of the road cheap grade ply .. IS Needed. However marine grade will be hard to thin coat and have it soak in ( Its basically allready sealed ) therefor just resin coating,reprepping then lams are fine.

The Reason why I suggest thinning and recoat after recoat IS valid. ( nobody asked me why though .. just that its wrong ).

That reason is to SEAL those VERY thirsty plys so that When you start to actually "Glass it up" you ( like Everyone who has not done this will experience ) will not ruin the whole lam/resin and hard work by having MAJOR air voids because the glass cant make a viable suction affect.

Now with that said.. The END result of your wood for glassing should be as sealed up as possible for ez working with resin/glass.

Seal those Edges VERY well ( unsealed edges for stringers WILL NOT HOLD the glass and your wrap will undoubtedly fail on the top and partial down the sides ( unless you staple )).

As this is going to be ( mebbe ) my final post on this thread .. I will just say there IS a reason for everything I do/suggest. It may not sound correct..and sometimes seems to go against the Science.. but the Science of acually using these materials in application may not follow logistics. But IT works very well and can save you time and money.

Peace out..

YD.

 

[ondarvr]

Re: polyester resin ?

Marine ply is not sealed and may be made from many different woods, this is where the differences in resin absorption come from. I will say that with all the options for plywood there probably is some brand or style that has a sealer on it, don't confuse sealed with treated though.

YD what you are trying to do when pre coating wood is have the wood suck up resin on its own prior to being glassed so it doesn't suck it from the glass when laminating. Thinning or non thinning achieves the same result as far sucking resin from the glass, and thinning it does nothing to prevent rot because thinned resins are less water resistant and may only penetrate a few thousandths more into the wood.

If you want to use a very low viscosity resin for pre-coating the wood, the best product would an infusion resin. These resins don't have the thixitropes (silica) added that increase the viscosity so it can be used in hand lamination and not drain out.

Thinning resin is like making putty (peanut butter) and then adding acetone to thin it back down so you can laminate with it.

 

[twkjr 1250]

Re: polyester resin ?

i did it wrong , my sandwich is seperated in the center. so here i go again. feel like i'am digging a hole and someone saying just one more shovel full . this time i think i'll try pl ing the two pieces together. encapsulate with mat ,resin it to transom ,cover with 1708 . the problem i had was lack of knowledge , i was told to late to put hardener before thinning. however , since ply is multiple layers with glue inbetween does'nt make sense to soak . solid wood yes i would go for it. i have 1 question does pl adhere to poly well or better to clean ply.

 

[ondarvr]

Re: polyester resin ?

Sorry to hear that.


Clean the surface, it should involve sanding to remove any gummy surface. Acetone will inhibit the cure and frequently leaves a soft gummy residue that few things will stick to, actually even if something does stick to it the resin itself can be weak enough to fail again. So scuff it up enough to expose some wood fiber.

After sanding the PL should stick fairly well.

 

[twkjr 1250]

Re: polyester resin ?

thanks ondarvr , will try that . well back on the grinder again.

 

[GracieBell1]

Re: polyester resin ?

Ondarvr,
I HIGHLY respect your knowledge as I do not have any experience like that. Thank you for taking the time to explain it to me. I am now vervous that I used this idea and have already PL glues my transome to the innner skin. I have put three coats of the poly thinned with acetone. There is no film over the wood, it all went into the grain. You can still see and feel the wood grain. My concern now is will this hurt the sticking of my glass and poly tabbing and covering of the transom and stringers? I have used this on the stringers as well but have not installed them yet. Again there is no brittle poly covering the surface it all went into the grain. I also glued the wood to the inner skin with PL Premium and it seemed to stick very good. But will it hurt my glass and poly that will be used for tabbing and encasulating. You also hit the nail on the head with manufactures because Four Winns said this was a good practice and that PL is best to glue it to the skin, not mat ang glass. I have spent a lot of time on this boat and now am worried I will have to dig out the new wood transom... thank again Stefan

 

[GracieBell1]

Re: polyester resin ?

Drewpster, Great comment!!! I love it.

 

[ondarvr]

Re: polyester resin ?

Don't stress out over it, whatever you do will probably be better than what was done when the boat was built. As long as the surface is clean and hard, just scuff it a bit and the bond will be good.

Even poorly built new boats tend to last 20 years or so, by doing it yourself and paying attention to details yours will last much longer.

The key to making it last is making sure the wood stays dry, so make sure all wood is covered by glass and that every screw hole is sealed up tight.

I just did some work on my 19' center console, I moved the console so there would be more usable room for how I fish. This boat was advertised as being built with products, methods and wood that won't rot and from what I could tell they did a very good job on all but one aspect of it. The center console and seat/cooler combination are made with a flange at the bottom which sits on the deck and is glassed over, this is a great way to do it. The problem was they used screws about every 6" through the flange and into the deck to hold it in place before being glassed over, none of these screws were sealed with anything at all. From the inside of the console and seat these screws are wide open to water and the plywood under the F/G skin on the floor was discolored from the water contact, no rot yet though. Had they bedded the components in some kind of adhesive or caulk no water would be able to find any wood, but by skipping one simple step they significantly reduced the useful lifespan of the boat.

Sorry for rambling, just make sure no water can get to the wood and it will be fine.

 

[GracieBell1]

Re: polyester resin ?

Ondarvr, I have read probably all of your posts on Bond-o and other posts. So your info is gold. I have a similar problem. Four Winns did not bed the stringers they are floating. I made a scarf cut about two feet long and am replacing about 12-14' of both stringers. The water would get trapped in this area and was starting to rot the stringer from the bottom up. Also the bulkheads were rotting them as well. Four Winns only used a thin layer of mat to cover the stringers from the motor well forward, not even thick tabbing. And from the the moort well back to transome the used mat about 1/4" or less in thickness and did not even cover the backs of the stringers. Should I float the new sections and I only have Woven and mat to owrk with?

 

[GracieBell1]

Re: polyester resin ?

Some pics. Thanks Stefan

 

[GracieBell1]

Re: polyester resin ?

few more

 

[twkjr 1250]

Re: polyester resin ?

ondar seperated the two ply's had a good poly mix. Problem was when i screwed them together the srews did not pull them enough . i think i got it now . going to let it sit a coulpe of days since i' am to busy working .

 

[ondarvr]

Re: polyester resin ?

At this point you're probably thinking even without any experience you could do a better job...and you're right.

You can bed them in PL and try to at least put as much glass over them as there was to start with, but 2 mat is a minimum and 2 mat and a roving would be better.