I want to get back out to Tofino for more sea experience, and we decided that it would be wise to install a keel on the prototype boat to see how much it helps smoothen out the rough ride in the chop.
The first step was to determine how much weight is required on the end of the keel. My calculations showed about 100 lbs is required to offset my weight while climbing in through the top hatch, and I needed to verify this with an actual test in a pool.
I met John Mackay, Ben Eadie, my dad Rudi and Pat Lor at the YWCA on Thursday afternoon. It was a job getting WiTHiN through the SINGLE DOOR to the pool! I can’t believe we actually got it through that door. All of our measurements showed that it would be impossible, so we thought we would try it anyways. Unbelievably, we jammed it through that door!
Getting the bolt-on keel onto WiTHiN was super easy. Once she was in the pool, I just closed up the top hatch, and windows, rocked WiTHiN onto her side and used the pool deck to slide the keel onto the stub post already mounted on WiTHiN. I will use this same technique to mount the keel from the side of the dock when we get her out to the ocean again.
All of my weight is balanced over the side and
this is where WiTHiN stops her roll with 90 pounds on the keel.
Now I will remove the temporary weight plate tube from the keel and weld on a 3″ diameter x 24″ long stainless steel tube filled with about 90 pounds of lead shot. Then I’ll fair the keel strut and the ballast bulb, and it’s back out to Tofino!
Puff the Magic Dragon on March 8, 2008
Hi Greg!
I would not rely on just the weight of the keel as this could set up a rhythmic pendulum effect.
I would consider having two stabilising fins at the turn of the bilge. At a speed of < 9 knots their drag would be minimal, if of an appropriate NACA profile. However, they would serve as dampers to nullify the inevitable rolling created in a hull with such a high length / beam ratio and virtually semi-circular sections.
Carry on the good work!
Wally Vella-Zarb (Malta, Europe)
Puff the Magic Dragon on March 8, 2008
Hi Greg!
I would not rely on just the weight of the keel as this could set up a rhythmic pendulum effect.
I would consider having two stabilising fins at the turn of the bilge. At a speed of < 9 knots their drag would be minimal, if of an appropriate NACA profile. However, they would serve as dampers to nullify the inevitable rolling created in a hull with such a high length / beam ratio and virtually semi-circular sections.
Carry on the good work!
Wally Vella-Zarb (Malta, Europe)
Bruce on March 9, 2008
Hi Greg:
I like the idea of hardening the bilges to increase form stability of the hull – as in a typical vee hull kayak, but don't see the point of bilge keels. A suitably shaped fin keel between the hull and ballast bulb will provide much more roll resistance, preventing pendulum oscillation. The keel needs to be an airfoil shape anyway, to minimize drag, so this is a freebee.
Bruce Bolster (Petersfield, Manitoba)
David Tangye on March 29, 2008
I completely agree with Bruce. You will not get any 'pendulum' effect. The fin profile will see to that.