The Sailing Rig

The mast will be two piece fiberglass, with each half 5’6″ long. This allows it to fit through the pilothouse hatch to be stowed inside. The mast is stepped on the deck and supported by a compression strut to the bow and a shroud to each side. One piece or both pieces of the  mast can be used depending on conditions. In the sketch above the front view shows both mast sections and the full sail, while the side view shows one mast section and the top sail.

The sail rolls around the boom for reefing. The sail is a gaff sail with a very light gaff – more like a batten. The portion of the sail above the gaff will be attached to the mast with sliding collars. The lower portion will not be attached to the mast, but the luff will be reinforced so it can be tensioned. This will allow the lower portion to be reefed around the boom or raised from inside the pilothouse as there will be no need to deal with collars, sail slugs or a bolt rope. The portion of the sail above the gaff will be the storm sail and will rarely be rolled onto the boom. When the top sail is rolled onto the boom, it will unclip from the sliding collars as it rolls onto the boom. It will need to be manually clipped back in to the sliding collars when it is raised. The top sail is about 7 square feet. The total sail area is 34 square feet. Continue reading

Design Discussion Continued

The plan is to build the boat using 1″ thick EPS (expanded polystyrene) foam with fiberglass and epoxy on the inside and outside. The advantages are: EPS is easy to work with, the hull will have good impact resistance, the EPS will provide flotation, and it is lightweight. The disadvantage is I am having difficulty finding high density EPS. I’ve previously used EPS with a density of 4lbs. per cubic ft., but the suppliers I used are no longer in business. I’ve searched all over the SF Bay Area and the highest density EPS I can find is 2lbs. per cubic ft. For reference, Douglas fir is about 33 lbs. per cubic ft., and steel is about 490lbs. per cubic ft.

The problem with the low density EPS is it’s more difficult to shape, doesn’t allow as fine a finish, and doesn’t have good impact resistance. The fiberglass will delaminate from the EPS where there is high stress, and this will weaken the boat. So I really need to find high density EPS, and that is what is holding me up right now. Continue reading

Sailing Canoe Design Discussion

Here is some of the numerical data regarding my sailing canoe design: design displacement = 500lbs.; LOA = 146″; LWL = 134″; Beam = 32″; BWL = 32″; Center of buoyancy = 78″ from bow; Center of lateral area (hull only) = 75″ from bow; Lateral area = 3.32 sq. ft.; Prismatic coefficient = 0.56; Hull speed = 4.5 knots; Sail area = 36 sq. ft.

After studying the designs of other sailing canoes, kayaks, and small boats I’ve decided to build my sailing canoe with a flat bottom. The advantages are that it is easier to build, has good initial stability, and the sharp chine, or rail, will prevent side slip without the need for a keel or centerboard. The usual objections to a flat bottom are more wetted surface area, less strength than curved sections, and a rougher ride in choppy conditions. However, in this application I believe these objections are somewhat mitigated. With a flat bottom there is more usable interior space, so the boat can be shorter, reducing the wetted surface area (I want the boat to be short anyway so it will fit in the back of my pickup). Sure, a shorter boat has a lower ultimate hull speed, but this boat is for cruising around, getting some exercise, and having fun – it’s not a race boat. The bottom is only flat in regards to the longitudinal axis. There is significant rocker, so the bottom is curved along its length, adding strength. And because the hull is narrow, the bottom is buried six inches  in the water which will help produce a smoother ride. In addition, this is a low speed vessel so it will not be skimming across the surface of the water like a speedboat. Continue reading

My Sailing Canoe Design

SK1232 Sailing Canoe Sketch

I have been refining my sailing canoe design and this is my latest revision. I began by doing some concept sketches. This gave me an idea of the approximate size and proportions of the hull. I then used Carlson Design’s free Hulls software to optimize the hull shape. I went through probably two dozen hulls, each with minor variations in length, beam, rocker, and other variables.

I don’t have much boat design experience so I found the book ‘How to Design a Boat’ by John Teale to be very helpful. Between the book, Google, Wikipedia, and a few other resources I was able to figure out what the prismatic coefficient is, where to place the sail center of effort, and, most important, if the boat would float. Continue reading

I’m Designing a Sailing Canoe

The last few days I have been working on a few changes to my sailing canoe design. Since I am starting this blog several months after I started working on the sailing canoe, I’ll be doing some flashback sequences to get the two in sync.

I’ve sailed since I was eight years old, and it is something I really enjoy. The last couple of years I have also started kayaking. It is good exercise and paddling around in a small boat is great fun. I kayak on San Francisco Bay, and last summer I started paddling from AT&T Park out to the Golden Gate Bridge and back  once or twice a week. If you live in the Bay Area or are here for a visit I highly recommend this route. You can rent kayaks at South Beach Harbor (in front of AT&T Park). Anyway, on the return to AT&T Park in the afternoon the wind is always howling in from the Golden Gate, and I am always a little tired of paddling. So I started thinking it would be great to have a kite or sail on my kayak so I could paddle out and sail back. Continue reading