s/v Kaimu Wharram Catamaran

Vessel Name: Kaimu
Vessel Make/Model: Wharram Custom
Hailing Port: Norwalk, CT
Crew: Andy and the Kaimu Crew
About: Sailors in the Baltimore, Annapolis, DC area.
08 July 2024 | Somers Cove Marina, Crisfield, MD
25 June 2024 | Somers Cove, Crisfield, MD
12 June 2024 | Somers Cove, Crisfield, MD
03 June 2024 | Somers Cove, Crisfield, MD
25 May 2024 | Somers Cove, Crisfield, MD
21 May 2024 | Somers Cove, Crisfield, MD
12 May 2024 | Somers Cove, Crisfield, MD
09 May 2024 | Somers Cove, Crisfield, MD
01 May 2024 | St. Marys, GA
23 April 2024 | St Marys, GA
17 April 2024 | St Marys, GA
07 April 2024 | St. Marys, GA
02 April 2024 | St. Marys, GA
21 March 2024 | St. Marys, GA
01 March 2024 | St. Marys, GA
23 February 2024 | St. Marys, GA
15 February 2024 | St. Marys, GA
11 February 2024 | St. Marys, GA
06 February 2024 | St. Marys, GA
26 January 2024 | St. Marys, GA
Recent Blog Posts
08 July 2024 | Somers Cove Marina, Crisfield, MD


I was out of cheese and ham. This meant a grocery trip and then of course, visit the American Legion. Cuddily said she would be there after baking fresh fish that she got from her neighbor fisherman.

25 June 2024 | Somers Cove, Crisfield, MD

June is Too Soon

It is Juneteenth, election day for the City of Crisfield, twenty four hundred voters. Up for election are two city council seats for three candidates. The mayor wants to keep her current city council team.

12 June 2024 | Somers Cove, Crisfield, MD

Raindrops and Rainbows

You can take the Mediterranean diet too far, especially with the wine consumption. The noodles are OK if you are burning up the calories, but otherwise they will put on the pounds. So you are left with antipasto, not much else, salad? Chicken Parm? Yes, the chicken parm is probably in itself pretty [...]

03 June 2024 | Somers Cove, Crisfield, MD

Prejudicial Treatment

The excitement of a new baby in the family had me receiving phone calls from all over. The common denominator is that we talked about the weather and food. That makes me hungry and start planning to cook. Cuddily suggested we go to Sysco in Pocomoke to see what wine selection they had there and also [...]

25 May 2024 | Somers Cove, Crisfield, MD

Cap'n Granpa

The Memorial Day weekend was coming up and it is a big deal in Crisfield as well as most of the rest of the Chesapeake. It is the traditional beginning of the summer season. All the boats are launched or commissioned, lots of activity in the marina, motors started up for the first time in a long time, [...]

21 May 2024 | Somers Cove, Crisfield, MD

Cap'n Overboard

The awful jobs get done last. The Atomic Four was waiting for me to pull off the cylinder head, but there was an emergency job, sort of, the mainsail cover was torn and exposing the sail to U/V, very bad.

The Wharram Windvane

24 November 2013 | Bodkin Inlet/Chesapeake Bay
Capn Andy/more onset of winter
The Wharram designers have come up with their own self steering windvane, designed by Hanneke Boon. They sell a comprehensive set of plans for the device which includes adaptations to each of their boat designs.
I once had two image files, one of the windvane, and another of the sketch plan of how it was built. After searching all my thumbdrives and computers, I could not find the files. I did however find the actual printouts of the files, so I've scanned them and include them in these two postings.
Using this basic information and that contained in Peter Forthmann's book on self steering would be enough to build a windvane self steerer for a Wharram catamaran. The Wharram vane was used on their 63 foot catamaran on a circumnavigation, so it must have worked OK. It was coupled with a trim tab on one of the rudders. The ratios of trim tab area to rudder area are in Forthmann's book as well as other technical data.
The picture is of the Wharram windvane in operation. The windvane itself is a piece of plywood held in place by a bungee cord to a frame shaped like the letter H. The frame can tip back and forth on an axis angled 20 degrees from horizontal, angled away from the wind. One leg of the H has a counterweight which is adjustable to make the windvane balanced just slightly in favor of the weight, i.e., the vane will tend to revert to a vertical position. The frame also has an anchor point for the control lines, which pass over a large sheave on the axis. The size of the sheave is given as 100mm in the drawing (next time).
The axis is mounted in a pair of vertical supports, maybe 1x4 inch section, and they are mounted on a round plate. The plate can turn around a vertical pipe, about one foot long and about 2 inches in diameter. This pipe is glued into another plate, fixed, which is the base of the whole aparatus. A simple clamp of a wood block with a screw is used to clamp the round plate to the base.
The control lines pass down the vertical pipe to a pair of sheaves that are fixed in the bottom of the pipe side by side. The pathway of the control lines is restricted by molded epoxy filler so that they can't jump the sheaves. The lines can then control a trim tab shaft.
In comparison with the Sailomat unit we are working on, this Wharram unit represents only the windvane and not the servo oar or auxiliary rudder. The trim tab scheme uses the main rudders and the only problem is how to fit the trim tabs and run the control lines.
Most units now use a servo pendulum to provide the power to move the rudder. It is probably easier to make a trim tab and linkage than a servo pendulum. Perhaps a servo pendulum could be simplified to a servo oar attached to the tiller crossarm with the control lines to a yoke on the servo oar to turn it so that it then swings from side to side in the water. If the top of the servo oar shaft extends above the crossarm and it is secured laterally to the hulls, then when the servo oar moves from side to side, the tillers would move from side to side. The ratios of wind vane angle to pendulum angle, and pendulum angle to tiller ange, are in Forthmann's book.

About & Links

SailBlogs Groups