Full Displacement Hull of a Nordhavn
Planing Hull of a Sport Fisher
A Semi Displacement Hull of our Tollycraft
When Pam and I were negotiating about the boat we were buying one of the negotiating points had to do with whether or not the boat would be able to go fast if we needed. So now we understand more about what makes this happen. Sure more horsepower means faster, but if the boat does not have the right hull, then a gazillion horsepower would not make the boat go any faster.
My end of our negotiation was to have a full displacement hull like the Nordhavn, which means we would never go much faster than hull speed. Hull speed is proportional to the square root of the length of the boat at the waterline. The longer the boat, the faster the hull speed. This is the most efficient way to move large masses from point A to point B. Every boat whether planing, full displacement or semi displacement has a hull speed. Think of it as the speed that the boat can go without continually trying to climb its own bow wake.
However if you want the boat to go faster than hull speed the hull has to be designed to make that happen. That and more horsepower is required to keep the boat in the proper state relative to the water to ride “on top” of the water.
Our boat is semi displacement which means it can be put on plane, but it is not as fast nor as efficient as the planing hull. However it is more efficient than the planing hull when going at hull speed, or so I have been told. Sometime when I have the money it would be interesting to have two boats built similar except for the hull and do some tests.
Now you know everything I know about this and that’s all I’ve got to say about that.
Today Bye George got a fresh coat of bottom paint and the hull above the waterline was buffed to remove any blemishes. The bimini top was removed to have it restitched and tightened. This was a remnant from the storm at Pensacola last year. The fresh water pump was completed and the freshwater lines were tested. We will find out the results tomorrow. We are supposed to have her back in the water tomorrow afternoon. I can’t wait to have her in the water again. Pam still wants someone to do cleaning and waxing of the boat for her before we start our journey, and things have to be done on the inside and down in the engine room.
Bye George 