Hi everyone, I'm currently working on my Björn Thomasson Sea Racer, trying to break the 12Kg barrier.

That's 26.4lbs for some of us. Big Q: Is that a bare hull weight or is it fully outfitted (seat, rudder, footbraces, deck lines, etc.)?

In general the bulkheads add very little weight. A single 3mm cedar bulkhead with 3oz glass on each side yields a bulkhead that weighs little over an ounce (say 150g). The hatches can be big weight hogs. If you want a very light build for racing, forget the bulkheads and hatches and use light float bags in the ends (if your racing rules kayaks with no hatches). Heck you can take off most of the deck rigging while you're at it. The finish you decide on can be a factor also. You can easily add 0.5 - 1 kg in just varnish and/or paint.

The bare weight of Tim's Wahoo was 28 lbs (12.7 kg), 31 outfitted sans hatches or bulkheads. The deck is finished with just UV epoxy. The hull has two thin coats of silicone/epoxy paint. Lisa's fully outfitted Wahoo came in at 35 lbs with a similar layup but was also painted. So figure 4 lbs (2 kg) of added weight for hatches, bulkheads, deck rigging, paint, etc.

The Wahoo has a lot more surface area than the Sea Racer, though. For comparison, Scott's SR also came in at 28/31 lbs and that was with three bulkheads, hatches, full deck lines and custom paint. Get rid of the custom paint, bulkheads, hatches and add some other diet exercises and the bare weight of a Sea Racer could be around 24 pounds/27 outfitted.

Some things to think about...

BTW: Is there a minimum weight for your race class or is this just a building exercise to see how low in weight you can make a kayak?