Do I re hydrate hull before new caulking and paint?

Hi my wooden boat has been out in the Australian weather for a couple of months and the most recent warm spell has caused her timbers to shrink. I have sanded her back and repaired any damaged sections so am up to recaulking and painting stage. My question is do I need to re swell the timbers first or afterwards? And if I rehydrate them first won’t the timber be too wet for painting? I am planning on using sprinkling system and burlap to reswell the timbers but open to better suggestions except for floating her in a sling as we don’t have those facilities.

 

By caulking do you mean driving cotton with an iron and mallet, or some kind of putty only?

 

Cotton or oakum driven with iron and mallet and then sikaflex over the top

 

"Acorn to Arabella" steamed the hull prior to painting, but still found all the paint split as the planks swelled after some time in the water

 

That’s a shame! I’m not sure I’d be able set something like that up where I am as it’s out of doors.

 

Which product from Sikaflex are you using? The planks will swell and shrink with changes of moisture. Depending on the species the percentage of change will be different. For example, cedar will change dimensions a lot more than mahogany. It is the nature of planked hulls. Traditional paints had less gloss but were more flexible. What are you planning on painting with?

 

Followed his whole building process.
The oak planking he used is/was quite prone to dimensional change from wet/dry cycles.

 

I’m not sure as to the exact sikaflex product yet, can you recommend one over the other? The hull is mahogany and the paint I have for the topside is international brand but can’t remember what kind I purchased as it was a while ago. I’ll have a look when I get home and update this.

 

Are you talking about acorn to Arabela?

 

Sure you can. He was only in an open shed. Its just a bunch of plastic with a steam box.

 

I prefer polysulfides to polyurethanes. They are soft and can be sanded.

 

Yes, quite a project, not for the faint of heart.

 

I think the wind factor would probably cause a bit of strife, also we’re coming into fire a season here so not sure I could generate enough steam electrically but it’s definitely worth considering and trying to problem solve.

 

Steaming an entire boat after planking sounds like a fundamentally flawed idea to me. There had better not be anything inside that can't tolerate being filled with hot condensation. Aside from a labor intensive way to stress relieve the bent planking... No, I just can't see it. Glycol would be more effective and easier to control. Very slow to evaporate and toxic to fungi. Heat also kills fungi, but... too many buts.

Ethylene glycol swells wood the same way water does. It is very slow to evaporate, will diffuse throughout the wood and will hold some moisture, so the swelling is fairly permanent. Wet it down 2-3 times by spraying with a glycol and water solution, letting it dry between coats. Borates are optional and will help preserve the wood. Glycol will swell the wood and will not evaporate. The wood will be more stable and rot resistant. Used automobile antifreeze is the least expensive option and works well enough. Can the glycol leach out through the paint? Yes, eventually. It is not a perfect long term solution, but if it buys you 10 years, it isn't exactly a waste of time. A precise recipe can be found. This is not rocket science, winging it works too. Any excess water evaporate eventually, leaving the glycol behind. It will sort itself out.

In anticipation of, and in recognition of the caveat that glycol may adversely affect adhesion; West systems ran a test and found that there was a point where too much glycol and borax was apparently detrimental to adhesion. The reason was unclear and they didn't use multiple samples or repeat the test. The reason that the highest level of applied preservative caused poor adhesion was either that there was excess borax powder present on the wood surface, that the wood was so saturated with glycol and water, (wood is weakened when saturated), the surface was too wet for the epoxy to wet properly, or some combination of all three. They found that too much of a good thing isn't. How much is too much? Very hard to say, but you have to work at overdoing it. Maybe give it a rinse with clean water to make sure the surface is clean.

Toxicity? Don't leave open containers around. It really does take a lot of glycol to do any harm. Read the SDS, then argue. It is somewhat sweet, so a small child or animal might ingest a lot. It has happened. Act responsibly and you can avoid problems. You would have to eat a lot of treated wood to feel any effects. It is perfectly safe to handle. Ethylene glycol is also biodegradable when diluted at least 10:1 with water, so rinsing down any overspray with water will render it harmless to the environment. I had to know this for a job. The facts never got in the way of the emotions, so I also had to find a viable alternative to a perfectly reasonable solution. Never argue with the ref. The winning argument from the engine manufacturer was "We think it might work, but it will cost you half a million dollars to run the test or void the warranty."

 

Huh? Did you actually go an watch the video, and see how they just put plastic up to the gunnels?