PDA

View Full Version : Inner hull paint



DarnOld
02-16-2007, 12:19 AM
First of many "how to" threads I suspect.:) Couldn't find a thread that answered this so thought I would start one.

I am in the middle of replacing the fresh water tank in my (new to me) 36' 1965 Shepherd. To do that out comes the dinette, exposing wood that hasn't seen the light of day for 42 years. Still piles of dry and wet sawdust from construction here and there! Now that I have it apart I see there is no rot anywhere under the tank or behind all the woodwork (yeah!!! - this was a spot we were worried about as fresh water was leaking in just above this point). However the original inner hull paint is flaking and has been recently completely waterlogged with fresh water so it is at risk to rot pretty quickly in spots. Now that I have all of this out I figure it is a good time to replace the paint. The boat is on the hard and mostly covered so it is drying out.

What paint should I use? Should I let the wood below the waterline completely dry before painting? Wire brush out any exposed wood? I plan to have it out for maintenance for a couple months so it is likely to get quite dry. The hull is carvel double planked mahogany. I have absolutely no idea what the original paint is.

Most of this is hidden so esthetics are irrelevant for this part of the job just want to repaint to protect the wood. Some is below the water line, some above.

Some is exposed and has been painted a couple of times and is still in very good condition, no bubbles or soft spots. It looks like some kind of marine enamel not sure what so I would expect to simply paint over with a good grade of marine enamel.

The Bigfella
02-16-2007, 12:53 AM
I repainted the engine room of Grantala whilst on the water - above and below the waterline.

I used a good oil-based enamel - after giving the existing paint a good sanding. No problems - and I would have done that about 4 years back.

Make sure you use a fan to get plenty of air past you while you are in there doing that.

Ian

David Roberts
02-16-2007, 10:11 AM
Bilgekote. I don't use an undercoat with this stuff.
http://www.yachtpaint.com/Images/15_6207.pdf
But . . . why paint? Like the pdf says, it prevents oil, gas, sludge soaking into the planking. But if you don't have oil, gas, sludge, why paint? What does the paint do? Protect is kind of a funny word. What paint does is it protects wood from UV damage and it slows moisture transfer across the paint film. Slows. And it slows going both ways, so it also prevents wet wood from drying. So in the case of your deck leak, it would have slowed the moisture content increase in the planks being dripped upon. But if the drip had gone on long enough, they would have gotten wet anyway, and then, if the paint had been in good condition, been slow to dry when you fixed the leak.

Another thing to think about is: does fresh water really rot a boat faster? I think the opposite is true, because salt is hygroscopic, thus salt water wetted wood stays wetter longer. I never saw a boat moored in a river or lake that deteriorated faster than a boat moored in salt water. 'Course I haven't seen everything. In fact, river moorage is prized around here because of the lower rate of fouling and lack of worms. I think this myth comes from the fact that wood will rot at a certain moisture content and in the presence of oxygen. That particular MC plus oxygen is most easily reached by having a deck leak. So the wood is wet, but not totally saturated.

Anyway, paint it if you like the look. Mostly get all the old, loose stuff off and give everything a good sanding. Leave any paint where you can feather the edges nicely. Then clean it all up good.

DarnOld
02-16-2007, 11:43 AM
Thanks all, things to think about.

pipefitter
02-16-2007, 08:27 PM
If it isn't seen and there is to be a tank there that could leak again or even sweat,why not paint it with red lead?

Steveh
02-19-2007, 03:15 AM
I’m having Ngatira restored, (what I call sister ship to Waione. Most forumites should know this boat). When I purchased her she was 96 years old. Like all new boat owners I dived in and scraped and repainted every surface. In the bilges, under the settee and most hard to get to places I discovered wood in excellent condition and covered with red lead paint.

This was visibly the only coat of paint applied in almost 100 years.

I am presently repainting the interior hull with red lead again. Should be good for another 100 years.

Charles Burgess
02-20-2007, 10:18 PM
Red lead has my vote!

brockway
02-20-2007, 11:12 PM
Who makes a red lead paint and where do you buy it? You probally dont want to put it wear you would rub agaist it with your body does that make sense? for example wood bench seats?