Coastal Rowing Boat Design

[Oarsman]

We are currently in the process of designing a Coastal Rowing Boat to compete in racing regattas. There are some broad specifications that we must adhere to i.e. the boat be a max lingth of 34ft with a beam of a minimum of 66 inches. What we need to decide on is the hull shape! Can anyone point us in the right direction in order to achieve optimum speed and minimise drag when rowing? There are numerous shapes of hull currently competing in our regattas ie round bottom, flat bottom etc. What we really need to know is are there any general rules we should adhere to in order to minimize drag

[Tad]

Flatwater or open ocean, or a mix?

Openwater means a little more freeboard and more concern with pitching. Flatwater means the transom can be really small, no pitching concerns.

To minimize form and surface drag you want the longest possible waterline and the narrowest waterline beam. Sections should be circular for minimum wetted surface. Absolute minimum freeboard to minimize weight, use fabric spray covers forward and aft. If the rules allow the max beam to be at the sheer, vee the topsides to the waterline and then make a circle. Sort of a (really) round bottom dory. Rake the stem only slightly, waterline should be very fine forward and come to a point aft. Flare the transom above the waterline to damp out pitching, but keep it small (perhaps 1/3 max beam?) to minimize weight.

Optimum length will depend on the HP available, but longer will always be better in a sea. Look at the weight/power ratios of the fastest boats in these races and stick close to that. IE 150 pound boats (bare hull and rig) with two rowers is 75 pounds/person.

All the best, Tad

[marshmat]

If you're computer literate, I suggest Leo L.'s Michlet CFD program http://www.cyberiad.net/michlet.htm as a good tool for this. For thin mono- and multihulls, it is very good at calculating both viscous and wave drag. The GODZILLA algorithm built into Michlet is great for minimizing drag. There's a lot of documentation included with it that you should read as you experiment. It pairs with the popular FreeShip ( http://www.freeship.org ) hull modeller. I should note that Michlet works on plain-text files that take a bit of getting used to, it doesn't have a fancy graphical interface like Fluent or other $$$ software.

[nordvindcrew]

If you are not determined to do your own design, there are several sources for Sicilly Island Gigs. They are raced extensivey in Great Britian and there are many here in the North East. with a good crew they are un- Godly fast. a local boat with a crew from Cornwall knocked off a race of 4 miles in 29 minutes, if my memory is correct

[skyl4rk]

Keep rocker down to a minimum.