epoxy penetration/thinning a question

[John N]

Recently(but I can't seem to find it) there was a thread on various ways and theorys on thinning epoxy for better penetration.
No doubt I'm displaying my ignorance, but it ocurred to me today while I was brushing another coat of the sticky stuff on my Wee Seal hull that we all know how well it binds to wood ( Its not likely going anywhere ever) so with a coat of good paint over it nothing short of an actual fracture could possibly allow moisture to even aproach the wood. In which case penetration would not seem to be an issue.
The first coat seem to penetrate quite well anyway actually.
Thanks for any clarification or opinions on this,
John

[imported_Conrad]

http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=007375

[NormMessinger]

The recent discussion was here. (http://media5.hypernet.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic&f=1&t=007375&p=)

I agree with you the adhesion of raw epoxy. Gougeon tests published in Epoxyworks found that WEST epoxy diluted was less waterproof than raw. In my experience raw epxoy will penetrate the first ply of plywood, SuperPly specifically, made from unknow tropical hardwood.

On the other hand, if a quart of CPES costs less and covers more than a quart of WEST, say, CPES is a proven tie coat for what ever finish. They say.

Lots of opinions, little objective rigorous documented tests. Flip a coin, chose your authority and have at it. It'll all work out pretty good.

Um, well yes. In my not so humble opinion.

[garland reese]

It sounds as though you've already coated your boat with epoxy, in which case you've already gotten as much pentration as you will get. There are a number of products that can be used to thin the stuff........acetone being one. There are some varying thoughts on how much thinning can be done without degrading the qualities too severely. Warming the epoxy to thin it and help it penetrate is another method.

There have been some folks who've done some test panels and have written about their results, but it has been too long since I've read them, and I did not save the references.Robb White seems to get an unusually good level of penetration by first heating the boat to something like 120 degrees or so (maybe more????), and then turning the heat off and immediately applying all the epoxy that the boat will take up, taking advantage of the cooling temperatures of the wood and the tendency for the wood to draw in the epoxy as it cools.

If you are applying over plywood, the expoxy won't go past the first glue line ( I don't think).You could use Smith's CPES, which is nearly like water and penetrates quite well, and gives a nice base to apply coatings.

I don't think Iain is a big advocate of the use of epoxy as a sealant over the entirity of marine grade ply, but it is essential to seal the raw edges of your ply.

Moisture can and most likely, sooner or later, will get to the wood to some degree. It happens in fiberglass boats too.

Gougeon reccommends a net of three coats for sealing wood. Bear in mind you'll be sanding off a good bit during the fairing process, maybe as much as a coat or two..........

There's my unscientific opinions..........

Good luck. Wee Seal is a great design. A "short list" member for me.

[John N]

Thanks for pointing me to that thread. I had forgotten that it had started as a question of how to protect plywood that was suspect or had voids so penetration was a real issue.
I'm using meranti which at the time I bought it, I thought was good quality and void free but some of the things I have read here would seem to suggest that isn't always true so I guess it's a good idea to seal it inside and out.
John

[John N]

Garland, thanks for the info. I was wondering how many coats I would/should apply.
And yes in Iains book he just says he's never tried it himself but would be concerned that it would not penetrate. I had to smile when you mentioned heating the wood; half of the hull is in direct burning sun and the other in shade. ( what can I say, it was the boat or a garage, I couldn't afford both) and the side in the sun had no runs or defects at all and seemed to sink into the wood more. The shady side had/has all kinds of runs and problems.
John

[Bob Smalser]

Gunsmiths use a heat gun to bring unthickened, 4:1 epoxy to 115 degrees, at which it penetrates into cracked stocks better than anything I've seen....including the new cyanoacrylate glues.

That's what I do on boat repairs, too.

[ 06-29-2003, 08:52 AM: Message edited by: Bob Smalser ]

[paul oman]

hello everyone!

We sell a 20% VOC penetrating epoxy and are always recommending folks make their own using a thin 100% solids epoxy and their favorite solvent. You bring up a good point - wood is not that porous in the short term - i.e. the time it takes for solvents to evaporate or epoxy to set. Wood does resist 'water saturation' for a good long while and even if we assume that water, (the Universal Solvent) does not penetrate as well as other solvents, it still becomes clear that in many cases (such as 'fresh - healthy - new wood) penetration - at least with the grain - will be slight.

I would think that the 'heat gun' approach and a thin 100% solids epoxy to start with, is probably the best way to go.

paul
www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)

[Tomcat]

"No doubt I'm displaying my ignorance, but it ocurred to me today while I was brushing another coat of the sticky stuff on my Wee Seal hull that we all know how well it binds to wood ( Its not likely going anywhere ever) so with a coat of good paint over it nothing short of an actual fracture could possibly allow moisture to even aproach the wood. In which case penetration would not seem to be an issue. "

As to this point, one can only wish it were so. It is fairly straightforward for the wood to crack, and for water to penetrate. Better made plywood boats are usualy glassed over every exposed inch. One of my concerns about the lap ply thing is that I have difficulty imagining how the hulls could stay sealed, based on what I have seen pop apart, though based on their popularity it must work out well enough. I am currently repairing a ply boat that had some water damage. One thing about it is that any 1088 ply, which I asume is the base of most lap boats, stoud up even where other ply delaminated.

As with most wooden structures, you can go all the way with epoxy glass, or just paint it with latex and let it breath. The inbetween always seems to fail in my climate.