More paints and poisons

[White Swan]

Sometimes I wish wooden boat building was as easy as shaping and assembling pieces of wood. Sigh...

The past boats I've built have been small daysailer types so I've just painted the bottom with topside paint. No worries. I am currently building a fantail launch however (20'x5'x1'9") and it is going to be in the water for the season - fresh water however. My naive inclination was to just do the same, however the experts at Pettit and Interlux disagree. I should be buying different paint for above and below the waterline, different primer, different seam compound,... etc.

So here's the question. Is there some semblance of truth out there? Is all this necessary? (or is this just fueling the fires of controversy?). Is there anything wrong with just priming using a thinned version of the paint as I do with varnish? Would this work below the waterline? If not, what is a good bottom primer? Do I need 'bottom paint' or can I get away with topside paint in total submersion? Is there any hard (i.e. non ablative) white bottom paint out there? Do I really need two different seam compounds!? Is there a good flexible seam compound out there that could fill both roles? Once this is all worked out can I get the products in Canada? What happened to the days of yor when you just slapped a bit of paint on and went boating? Sigh.

Can you tell I've been at this a bit too long today? Hope someone out there can offer some insite, or at least an opinion or two.

Thanks
J

[Ed Harrow]

I have opinions, but Whitehorse! Yukon Territories! My father was there in the early 40's. Took the narrow-guage line out of Skagway then, IIRC, boat (wood-burning paddlewheeler) back via the Yukon River.

I think it was Whitehorse where they "filmed" the great arrest scene. Dad and his cohort were dragged (it was quite an event) from the cab of their truck, hand-cuffed and leg-ironed (the mounties were not about to let these desperados get away.) For humor, of course, the first attempts were several mounties pulling the two out the opposite doors. Along the way, and not be design, the key to the cuffs was lost... Dog to the rescue. I haven't seen those films in years, they are all falling apart... :(

Their actual employer was the US Government, not the film industry. smile.gif

[imported_Dutch]

interlux makes a nice epoxy based barrier coat-grey in color i think its the 2000-2001. if it was my boat thats what id use and depending on how much growth of sea life is in your area should determine the botom paint you use. i use a lot of intrlux micron csc. runs about $300+ a gallon now, but you get what you pay for in bottom paints. you dont want to use a cheap one which will be coming off in big flakes a few weeks after you haul her out

[Bruce Hooke]

The short answer to at least part of your question is that unless you want to pull the boat out of the water every couple of weeks to clean the bottom you will get a lot of growth on the bottom if you don't use bottom paint. At least that is certainly what would happen in more temperate climates and I think it's likely that the same thing will happen up there.

As to primers, one advantage of using a "proper" primer is that primer is generally cheaper than paint so you can build up a smooth base for the paint using the cheaper primer and then go to paint.

P.S. I would be careful about using an epoxy based paint on a planked hull. It seems like these are designed more for stable surfaces like epoxy or glass rather than for surfaces that shrink and expand like wood...

[ 02-16-2005, 12:25 AM: Message edited by: Bruce Hooke ]

[Don Z.]

Ummm... a couple of points.

First point: Where is the Chemist when you really need him?

Second point: When it comes to bottom paint, there are a few things going on. I just learned this, so bear with me.

My experience is actually on the Great Lakes, and it sounds to me like you're asking about fresh water use... but that's not really where things get interesting.

To split hairs, let's be a little more precise in our language. There is a difference between "bottom paint", which is a paint meant to be used below the true water line, and "antifouling paint", which is used to, well... keep things from growing on your bottom.

Now, as I understand it (and I did just learn this, and the Chemist isn't here to keep me straight), bottom paint is designed to limit water intrusion, or at the very least, let as much out as it let in. Those paints that Interlux describes as "not for use below the true water line" (check it out, the label actually says that!) do not do this well.

So, having said that, you can see that you do need "bottom paint".

Which brings us to the antifouling question. Yes, you need that too... but you need one designed for the creepy crawlies found in your area. True, most will have some effect, but your best bet is to ask what other people in the area are using. Also, those paint companies, while they do have their own best interests at heart, they can protect those interests best by selling something that works. Call their customer support lines. They do want to help.

Oh, and as far as the primer goes... it sounds like snake oil, but it does make a difference. The paint is designed to stick to the primer. The primer is designed to stick to the wood, to be thick enough to allow for some fairing, and to do other things at the chemical level that people who understand chemistry can explain better than I can. It does work. Really!

[Bruce Hooke]

Don makes a good point. What I meant by "bottom paint" was anti-fouling paint...

[imported_Dutch]

It seems like these are designed more for stable surfaces like epoxy or glass rather than for surfaces that shrink and expand like wood... can you point me to where you got this information?

[White Swan]

I agree, where is the Chemist when you need him. Good point about bottom paint vs anti-fouling paint. I don't want antifouling paint. We used to have a 'glass boat and we just scrub the hull once a season and that did the job.

I agree wiht your comment on topside paints. That's exactly what both Interlux and Pettit rep's said. However, some of the small boats I've build sit in the water most of the summer and don't seem to have a problem with the paint I've used over the whole hull (Easypoxy), but maybe more time will tell...

Some of the epoxy based paints say they are for metal of fibreglass, by which I had assumed they wanted a more stable base than wood. But that is reading a bit between the lines.

I probably asked too many thoughts all at once, but does anybody have any comment on the seam compound questions?

J

[Ron Williamson]

Topside and deck seam compounds are more UV resistant than those for below the waterline.
R