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.
Rick
On 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: Rick Willoughby <rickwill@bigpond.net.au>
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a new topic | • | Messages in this topic (3) |
SPONSORED LINKS
.