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Old 05-02-2013
Brent Swain Brent Swain is offline
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Re: Bob Perry's take on Wolfenzee's dream boat

Quote:
Originally Posted by bobperry View Post
Gosh, "positive stability to over 170 degrees" that's impressive but I've never seen it one one of my conservative designs. Of course you have no righting moment at 180 degrees. That's what this is all about. Any upright boat right,side up or inverted has no stability. You have to heel one way or the other to get a RA. If the VCG and the CB are lined up there is no "arm" ( Righting Arm)And I don't do any stability calculations based "on a midship section" I use the whole boat. I do not use deck structure. The Queen's Birthday study showed that pilot houses did not help. Theoretically they should but they didn't Go figure. I have never used deck structure so in order to continue the apples to apples comparison of my designs I will not use deck structures. If there is foam in the mast do I use that too? No.

I am in total agreement with Brent about the weight of cruising gear. The typical cruiser does not want to saw the handle off his toothbrush to save weight. He wants tankage, spare parts, tools, watermakers, gen sets, copious amounts of ground tackle including lots of chain and a full sized guitar. This stuff takes volume if it is to be stowed and leave enough room for humans to live in the left over volume. This is not theory. To do this with any style and grace takes a boat with some displacement. No,,,it won't be a rocket and go planing off into the sunset. But you know what? Most cruisers don't have the skills or the eneregy to push a boat to planing speeds for days on end. They are comfortabvle and safe, SAFE, pushing the boat to hull speed and relaxing. Why design for a level of performance that is beyond your sailing ability or inclination to maintain. Better to design for good all round performance with a good safety factor for your structure and your stability while providing a comfortable ride and a comfortable home.

If you want to reach for the upper limits of performance you can decide for yourself what you want to leave behind. But when you arrive exhausted at the next destination and anchor next to a big, GUNBOAT catamaran you may have to rethink your idea of exactly what is fast. Because compared to that GUNBOAT the POGO is a PIGO. To go truly fast you need more than one hull. Now do we want to get into that argument?
No, pilothouses dont help if you have the standard outdated sliding hatches which wont keep the water out, and they quuickly fill with water. With the more modern totaly airtight one piece door, the type which I and the round the world racers use, all that buoyancy up high is a huge factor in ultimate stability, and any calculations which dont take that into account are inheritantly ,grossly inacurate. As any accountant will tell you, start doing the math, and get one factor wrong, and everything from that point on is wrong.
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Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
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