Paying seams
With short notice I managed to book launching for coming Friday. Just a few days left for final touches but this spring is storming already with dry wind and sunny weather. A few seams of Meritaten’s hull have already opened, one should not wait too long for launch.
I temporary seal opened seams with Stockholm tar (sold as Farm 80). Just a smudge above the seam, not really pushing the paste between planks. The aim is to slow down water which would otherwise storm through hair-wide openings between planks. All this to buy time for wood to swell and tighten the hull. On mahogany hull swelling takes around one day. Without sealing cracks it would be very dramatic launch, with bilge pump taking the hit for a few hours.
There are many ways of preparing wooden hull for launching: smearing seams with butter, gluing paper tape or “dusting” the hull by opening a bag full of wood dust under the boat, in water. Wood dust will get sucked between planks and seal openings. In the old times people even used ant stack for that. The only drawback of this last method, apart from being dramatic and killing poor ants is that particles get stuck between planks. When wood swells they will be compressed between planks and eventually damage adjacent surfaces. This will lead to even greater leakage next spring and eventually the hull will never get tight - with damaged seams leaking water even after wood swells.
Butter method is better as butter is soft and will be squeezed out of the seam, with remaining fat being absorbed by wood. Paper tape works fine, too - just that the boat will have paper spaghetti attached to the hull for a few days after launching. Tar method is the easiest - just smear it above seam openings, to hinder water flow. Wood swells and closes the seam and tar just remains outside as a thin bulge, easy to scrape after the boat is recovered for winter storage.
Meritaten’s hull was originally glued with Cascofen. Very good glue at its time but after 60 years it disintegrated into powder, leaving the hull as pure traditional, plank on frame construction.
I’m considering re-gluing it, at least below water line, with epoxy. The bottom is in need of scraping anyway so if I do it next winter I may as well attempt re-gluing the hull. That will result in reduced launching-drama and result in much stronger hull, as it originally was. But it is a major job, very time critical - it is important to do it when wood’s moisture content is correct so that gluing is done in hull’s “nominal” state.
I finished paying seams when it became dark. Varnish is now fully cured and the job turned out very well.
Tomorrow I’ll bottom paint the hull and start the engine. Batteries will get top-up recharge and we will be ready for launch!