CPES substitute

[maa. melee]

I plan on building a quick and dirty dinghy from 1/2" ACX and was wondering what I can seal it with besides epoxy. It doesnt have to last long, a few years at most. Is there anything I can pick up from the hardware store that will fit the bill?

PS (I hope I didn't open the can of worms with this one)

[ 03-08-2005, 03:45 PM: Message edited by: maa. melee ]

[Stiletto]

Forget the can of worms, they dry too lumpy. ;) A good paint job is probably your best bet if you dont want to use epoxy. Redlead if you can get it and then the topcoat of your choice.

[Keith Wilson]

A few years? Well, ACX fir will eventually check no matter what you do, unless you cover it with fiberglass . It it were my boat, I'd prime it with Zissner 1-2-3 and then a couple of coats of the best Latex porch and floor paint I could find. Put on another coat every year or two, and don't let water stand in the boat. Not yacht quality, but it'll do.

[ 03-08-2005, 04:25 PM: Message edited by: Keith Wilson ]

[maa. melee]

Thanks both of you for the swift responses. What does zinsser have that say a 'watersealer' doesnt? maybe I should rephrase my question as follows: What is the best product my hardware store carries to keep my boat usable for a few years?

I must have seen the word 'cuprinol' a million times as I searched the forum. Would that work and would I find it at a Lowe's or Home Depot?'

[ 03-08-2005, 05:00 PM: Message edited by: maa. melee ]

[Keith Wilson]

Cuprinol underneath all might keep rot at bay a little longer. It's a wood presertative; you can get it at most paint stores, but I don't know about Home Despot. Zissner 1-2-3 is just a decent water-base primer that helps the paint stick; I've had good luck with it on Q&D boat work and house projects.

[ 03-08-2005, 05:28 PM: Message edited by: Keith Wilson ]

[Bruce Hooke]

First off, a dingy made of 1/2" plywood is going to be mighty heavy. Unless you are planning to haul granite boulders around in this dinghy or bounce it off rocks from 10' in the air :D , I'd think you would do fine with 3/8" plywood, and 1/4" plywood is fairly common for dinghys. Of course I am assuming this is really a dinghy we are talking about and not an 18' skiff with a good size motor on the back!

I built a flat bottom punt with 1x12 boards for the sides and a 1/4" ACX fir bottom and successfully used it to move around the roughly ~400 pound parts of a sculpture.

Second, my experience with fir plywood is that you basically have two rational choices as far as coatings go:

1. Just use good ol' paint (latex or oil) and know that the plywood will check and water will get into the plywood. Over time this may well cause rot if the boat is kept in the water. For a dry-stored boat checking is pretty much a purely aesthetic issue (it should be noted that the combination of checking and internal voids can cause minor leaking, especially in 1/4" plywood, but not enough to be a problem in my experience).

2. Coat all surfaces of the plywood with fiberglass. Epoxy alone will not do the job, you need glass cloth too. For a cheaper alternative polyester resin should work. This treatment will keep the plywood from checking.

I suppose the option of apply some sort of poison to the wood and then painting should be noted too. I do not have any experience with this approach so I cannot comment on how effective it is. I would be somewhat concerned about the poison leaching out over time. There was a Wood Technology column about this in WoodenBoat a while back. Still, if you are going the paint only route anyway some sort of poison might be a cheap addition.

[maa. melee]

I'm glad you chose to comment, Bob. Yours and everyone's opinions are very appreciated. The checking problem doesn't really bother me. Even plywood sitting in my garage checks. For a 'temporary' boat like this I'm willing to sacrifice my boat's spot in a beauty contest for cost of materials. I am worried about those voids in the veneers where water can soak right through into the boat. The endgrain will be hidden with custom battens. I'll have her on a trailer or worst case, pulled up on the beach for a night. Basically I want a dry interior and an outer verneer that will resist rot if only for a few summers. Will a deep penetrating waterseal like Thompson's (the word 'waterseal' should be taken with a big grain of salt for this product smile.gif ) followed by a tough coat of oil based enamel work out?

[maa. melee]

Anyone think enamel over thompson's a bad idea?

quoting from their site: 'Thompson's® Water Seal® waterproofers protect your surfaces from the elements and provide the highest level of waterproofing protection available.'

Someone wanna back that one up? :D

(Sorry for my above post, I meant to acknowledge Bruce for commenting. Mistakenly wrote Bob.)

[ 03-08-2005, 11:13 PM: Message edited by: maa. melee ]

[Ron Williamson]

I have never heard anything good about Thompson's.
R

[Ken Hutchins]

I would seal/prime with a couple of coats of thinned 30% of oil based varnish and then put on a few coats of oil based paint.
Cuprinol as stated above is a preservative and like a lot of such stuff needs to dry for an extended time before painting over it. Cuprinol is now owned by and available at Sherwin Williams if you want it.

[Keith Wilson]

Paint, of almost any type, would be a lot better that Thompson's. You could paint a bit of unthickened epoxy on the plywood edges; it soaks in nicely, seals better than paint alone, and doesn't take much time or money. It might give you a couple more years, as that's usually where rot starts.

[paul oman]

I believe Thompsons water seal is a wax (and maybe some silicon) in a strong solvent. We tell folks with a thompsons water sealed garage, basement etc. that want to use our epoxies to paint their floors to forget it. Use thompsons water seal on your floors and forget about every being able to paint them with anything!

With your dinghy - I would take whatever epoxy you have on hand and cut it about 30% with a strong solvent and brush on a coat or two. It will be so watery that for a dinghy it shouldn't take more than 20 minutes or so to do the job. Probably will not stop the checking etc. but will slow it down and also keep the paint you put on lasting longer.

regards
paul oman
progressive epoxy polymers

[maa. melee]

Thanks alot for your comments. I'll see if I can't find any cuprinol, else I'll probably use some good primer under a few coats of oil enamel.