- do you normally add kevlar or other "tougher" reinforcement to the laminate schedule for the bottoms?
Most hull damage will be hitting something, which is taken by the solid foam bows. Kevlar on the hull bottom will not make a lot of difference if you dry out on sharp rocks. The rock that will go through the standard laminate will probably also go through the kevlar one.
Because of the shallow draft, no rocker, no forebeam and flat bottom it is easy to place something under the hull for drying out on rocks. A tyre, fender or piece of 4 x 2 with 2 strings attached can be pushed under the bow, walked aft and tied in position. 2 for the lee hull, one for the windward.
- any issues with blocking on the hard with the wide flat panels on the bottom? I assume you want to make sure the load is taken on the edges where the sides meet the bottom?
Definitely. Or under a bulkhead. The edges are heavily reinforced so easily capapble of taking the weight.
- any issues with lifting? Thinking about the bigger HarryProa's, I assume it is almost always a crane with spreaders and straps? Would it be worth building some lifting eyes in where the beams attach to the hulls?
Could do, but easier to put the straps around the beams or under the hulls on a bulkhead.
- I'm guessing if you needed thru-hulls, you would want to surround them with bulkheads/panels that were at least as high as the water level to contain any water in case of leaks or maintenance challenges
Good idea. The space would only need to be big enough to fit your hand and a screwdriver into..
- Bilge pumps would still be needed in case of a catastrophe but would not be hidden under floorboards
True. But they would be easy to get to to clean and a long enough hose or cable or convenient plugs it could reach anywhere in the hull.
- I assume there is not reason you can't finish the interior floor with a laminate or some other surface to make it look more "homely"
No problem. In most cases, this can be included in the infusion.
The difference depends on the flare of the sides. A flare of 28 degrees gives the lowest wetted surface for a three panel section. That flare results in a 5% increase in wetted surface over a semi-circular section. A 2 to 1 rectangular section has 12% more wetted surface than the semi-circular and a square is 19% higher.
The wetted surface area is only part of the equation. Wave making is related to the maximum waterline beam to the power 2. A section with high flare has more BWL than a section with no flare so it will lose more energy to wave making. Overall the lowest drag shape for any given design speed and displacement will have variable flare so the ends flare significantly while the mid sections have much less flare to reduce the maximum BWL.A three panel section hull optimised for minimum drag for a given speed and displacement is inevitably shorter than a round section hull and that results in a weight saving. The weight saving reduces the design displacement and accordingly lowers the wetted surface. As it turns out a three panel hull will have lower wetted surface than a round section hull if they are designed for the same load carrying conditions.The above all relates to calm water. Once the hull is in waves the equation changes again and hull length is the main factor in limiting pitching and that has a large bearing on added drag from any pitching motion.RickOn 10 Oct 2018, at 3:38 pm, ryanonthebeach@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:good topic Mark.. I would like to add one question:
What is the overall difference in wetted surface between square and round? And how much does that impact performance in lights airs
Posted by: Rob Denney <harryproa@gmail.com>
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