This article was originally written and published in the International J/24 Magazine in 2003. During the writing of that article an option occurred to me that I included in the article as an option. Since then, it has become clear to me that the option is really the best way to do the job, so it is the only way presented here.
Background – Some years back, J-Boats Italy introduced a new hull liner that effectively sealed in the v-berth area and the lazarettes to reduce the accessible interior space in the boat which in turn, reduced the tax that is assessed in Italy based on the internal volume of a boat. Additional benefits of this liner were added buoyancy and some cost savings. When US Watercraft took over production of J/24’s in the US, they added this feature for a cleaner look inside as well as the buoyancy and cost savings
To convert older TPI boats to take advantage of the buoyancy benefits gained here only takes the addition of three panels, a little fiberglass work, three inspection ports and lots of sealant. The conversion as described here, adds about 325 kg. (715 lb.) of buoyancy.
Getting Started Some boats have three bunk boards in the v-berth, while others have just two covering essentially the same area. If you have the two board system, you will have to cut off the two boards where they cross the half bulkhead, and fill in the area forward of the half bulkhead with a new piece of plywood. Remove the bunk boards and the two pieces of plywood that make up the permanent part of the v-berth. These two pieces are screwed into wood flanges attached to the bulkheads and into a fiberglass flange built out from the hull. Examine all wood in this area for rot and delamination. Replace pieces as necessary
Rough sand the hull and bulkhead flanges with 80 grit where the permanent v-berth boards contact it. Rough sand about two inches above the line around the hull and main bulkhead where it is contacted by the permanent v-berth boards to provide good adhesion for the fiberglass and resin that will secure them to the hull and bulkhead. Rough sand the edges of the permanent v-berth boards and about two inches in from the edges to remove paint and other finishes that might negatively effect resin adhesion. Caulk any holes in bulkheads through which wires run
In the “mini – v” area all the way forward, mark a level line around the hull, approximately 13mm (half an inch) below the top of the forward most bulkhead. Rough sand this area as above to receive a closure board sealed to the hull and forward bulkhead. Epoxy some small wooden cleats around the hull and bulkhead, below the line, to support a plywood panel. Make a pattern of pieces of cardboard taped together to rest on top of the cleats, closing off the space below. Use the pattern to cut a panel out of quarter inch (6mm) plywood to fit the space as tightly as possible
Inspection Ports – Install a 150mm or 200mm (6” or 8”) sealed inspection port in each of the sections of the permanent v-berth boards as well as one in the small bunk board that covers the area between the half bulkheads. This board will be permanently installed and sealed to the original two permanent v-berth boards. Locate the inspection ports to provide the best access to the spaces below them in order that you will be able to sponge out any condensation that may accumulate and access any fittings or bolts mounted through the bulkheads (like the nuts for your corrector weights). Make sure these inspection ports are properly bedded with sealant
Reassemble V-berth –To reassemble the v-berth so that it provides buoyancy, you will need a significant amount of caulk or sealant. I used DAP Kwick Seal, an inexpensive, quick setting sealant available from many building supply sources. Spread the sealant on all of the flanges and bulkhead edges that will contact the permanent v-berth boards. Screw the permanent v-berth boards into place as they were before. Do the same with the small board that used to be a removable bunk board between the half bulkheads. Use sealant to seal the gap between this board and the two other permanent v-berth boards. There will be a fairly wide gap between the boards you have just installed and the hull, and a lesser gap between these boards and the bulkheads that border the v-berth space. Fill all of these gaps with sealant. Where the gaps are under 8mm (3/8”) wide, fill the space level with the top of the permanent v-berth boards. Where the gaps are wider, fill them to approximately 2mm below the top of the v-berth boards and level with a filled polyester resin (Bondo, etc.). Use two layers of light weight woven fiberglass strips approximately 75mm (3”) wide to finish off the project around all of the edges that contact the hull or bulkheads. Also seal the joint between the original two permanent v-berth boards and the small board between the half bulkheads with two layers of fiberglass. You have now completely sealed in the section between the half bulkheads. Use the same process to seal in the “mini-v”, up front. Make sure the forward hatch is open, and you may even want to use a fan in the hatch or companionway to force fresh air through the cabin area. If you begin to feel any ill effects from any of the sealant or fiberglass resin products, get out of the boat and into fresh air immediately.
The Side Tanks –To finish the other two sections under the v-berth, we must add a longitudinal panel between the inside edge of the permanent v-berth boards and the inside bottom of the hull. This should be done with either 6mm (1/4”) plywood with exterior glue or G-10 epoxy fiberglass board 3mm (1/8”) thick available from industrial outlets and catalogs like McMaster-Carr. The G-10 most nearly duplicates the current fiberglass liners and is impervious to moisture. To locate where the panel will contact the inside bottom of the hull, use an adjustable square resting on top of the permanent v-berth boards and projecting downward onto the inside bottom of the hull. Adjust the length until the blade almost touches the inside bottom of the hull and make at least five marks fore and aft on each side. Rough sand at least two inches on either side of the marks for good adhesion and remark the line if necessary. Glue down a 13mm (1/2”) wide strip of the panel material (G-10 or plywood) along the line to the outside of the line (under the permanent v-berth boards). This is your stopper strip against which to press your panel. Now make a cardboard template of your panel, and be very accurate. Use a very straight edge at the top and cut the template a bit small. Then use smaller pieces of cardboard or stiff paper to make up the difference by taping them to the main template. When done, trace this onto your panel. You may want to make the panel 10mm – 15mm short on each end to make it easier to get it into place. The difference can be made up with fiberglass when you glass it into place. Cut out the panel and drill it so you can screw it to the edge of the permanent v-berth board. Run a bead of caulk along the edge of the v-berth board and where the panel will contact the hull and the stopper strip. Screw the panel to the v-berth board, and use two layers of 75mm wide, light weight fiberglass to secure the panel to the hull on the bottom and the bulkheads fore and aft. Repeat for the other side of the boat
Finish it off –Caulk up any holes or openings in your floatation tanks and sand the fiberglass smooth. Rough up the G-10 with 150 grit sandpaper and paint the whole thing to match the rest of the interior. Call you measurer to get reweighed. My boat, Magpie, weighed 5 kg more than the last time it was weighed. Rather that go through the hassle of removing a corresponding amount of correctors, I simply eliminated 5 kg from my optional equipment inventory
I hope you will never need the buoyancy. Good luck and smooth sailing.
US Technical Committee