surfdabbler

I did a float test in the pool last night. Put everything in place, keel and rudder, and floated it in the pool, to find out how much weight I have to spare for the rest of the build. Oh no! According to the waterline given on the plans, the hull and keel alone is already overweight. Taking off the deck allowed the boat to float at it’s designed waterline, with a total boat weight of 1.3kg. Scaling from the original plans, the quoted floating weight is 1.46 kg, which is about what my boat is now, without any electronics or sails, or paint, or extras.

The keel and bulb alone are 1080 gms.
Hull is now 240 gms
Deck is now 150 gms
Electronics estimate – 150-200gms
Sails and mast estimate – 150 gms

Totals - keel at 1080 gms, and 700gms in the rest of the boat, for a total weight around 1.8kg.

So, it’s slightly overweight already, and even the quoted design weight was too much for the waterline.

I think at this stage, I’m going to pretty much ignore it. There’s not a lot I can do at the moment, short of rebuilding, and I’m not doing that. I may think about putting holes in the deck and using solarfilm, but realistically, that’s not going to help much, and will probably just look bad.

I just checked out wikipedia, and the keel weight on the real VO70 boats is around half the boat weight. Aha! This design was made with an overweight keel, to suit a non-canting design. So my canting keel should actually be around 700 gms – cool. Removing 400 gms from the keel will be more true to the weight distribution of the real VO70 boats, as well as reducing the servo size required to move the keel. This 400gms will be enough to bring the overall boat weight back down, to acheive the correct waterline weight. OK, I’m happy now, and I’m going to just keep going.

I just have to make another keel sometime, although I’m in no rush to do that right now. I’ll keep the original one too, so I have the option of running the heavier boat without canting keel. The keel just bolts into the slot, so it will be no problem to swap between them at any time later.

Meanwhile, it’s good to see the new Ericsson boats doing well in the race!

Finally, I know everyone likes a good photo, so here’s one of the float test. Sorry it’s so dark. I only do this at night time. You can’t see it very well, but the keel and rudder are in place, and it’s just duct-taped to stop it leaking. I gave it a push in the water, and I was amazed at how much resistance there is to any sideways movement, but how effortlessly it floats forward!