Friday, June 27, 2008

Beam and Shroud Lashing Cleats

With both hulls turned back upside down, my goal now is to finish everything from the sheer down so that I can paint the bottoms with anti-fouling and prime and first-coat the topsides with paint. The reasoning behind this is that all the details that are easier to do upside down will be completed, eliminating the need to invert the hulls again, so that once I turn them right side up, I can focus on the cabin interiors and deck structures.

The beam and shroud lashing cleats, or pads, are part of those details that are easier to complete with the hulls upside down. The reason for this is that it is essential to completely seal the undersides of the lashing surfaces created behind the cleats. This is a common source of rot in the smaller Tiki designs.

Below are all the lashing cleats - a total of 12 for the beams, inboard and outboard sides, and 4 for the shroud lanyards. I had planned to install chainplates instead of these lanyard pads for the shrouds, as is shown on the Tiki 30 plans and as the previous owner of my Tiki 21 had done. In the end I decided to stick with the simpler and practically free way of attaching the shrouds that is shown on the plans. Four chainplates of adequate size and strength plus the four shackles required to attach them would have been close to $300. That cash can best be spent elsewhere on the boat. Wharram's methods of eliminating such expensive hardware are brilliant.

Yesterday I installed all the beam and shroud cleats, gluing them well with epoxy and using temporary screws to hold them until the epoxy cures. The screws will be removed and replaced with 1/4" stainless carriage bolts after the cleats are faired and ready to paint. The thru-bolts pass through the extra layer of plywood backing already glued on the inside of the hull at each lashing point. They will be secured with large fender washers and self-locking nuts.

Here is a close-up of one of the lashing cleats, taken this morning after an initial coating of epoxy. Each plywood pad is made of 18mm ply and all corners are rounded and the edges are radiused to 3/8" so there are no hard edges exposed. The next step is to round over the bottom edges of the teak sheer doublers on either side of each pad. Small fillets of epoxy with wood flour and silica will be made on each side where the pad meets the doublers and sheer stringer, and a small fillet will be carefully made and smoothed on the inside edge of the pad. This is why it is easier to complete this job with the hull upside down. All surfaces in contact with the lashing lines must be as smooth as possible, as well as completely sealed from water intrusion. Sheer doublers made from solid teak will help greatly in preventing rot in this vulnerable area.

When all these lashing areas are completely faired, sanded smooth, and sealed with epoxy and primer, I'm going to thoroughly wash the hull exteriors and apply the bottom paint below the waterline. The first coat of topside paint can also be applied up to the bottom edge of the sheer stringer. The stringer itself will remain bare until after the decks and cabin sides go on, as I plan to wrap the fiberglass sheathing from the deck surfaces around the stringer to give a double layer of protection to the sheer and reinforce the deck to hull joint.

No comments: