JEM Watercraft

Hey Matt, I was wondering if you or anyone over at duckworks has ever fooled around with the idea of designing a kayak sail. If not, do you know of a resource where I can find designs for a sail like this:


Any assistance would be appreciated.

Stephen

http://www.boat-links.com/Tyvek/

I'll let Hoz know you're question. He's an experienced sail maker.

Thats a form of batwing sail. Pretty simple and they are cut"flat" with no aerodynamic shaping. You can deduce measurements by comparing the mast height to the kayak, then extrapolate the boom and battens.


I used to have a lot of links but lost them when my computer crashed. Here are a few I found with google search:

http://www.friend.ly.net/~dadadata/_Rus ... Sails.html
http://www.laurieford.net/fitstorm.htm
http://www.laurieford.net/sails.htm
http://www.laurieford.net/rudders.htm
http://www.vision.net.au/~jennings/sail/sail.html

Here is how I made one of the canoe and pirogue.

http://www.unclejohns.com/boat/sail/sail.pdf

Chuck.

I like that. That would be easy to do on my Stalker.

Mine is a modified form of the Bat wing and it works really well for sailing down wind , you can sail with the wind or at a quarter off of you but not against the wind.
Sure beats paddling over open areas of water , might say it saves the paddler a lot of work , plus if you fish then troll a plug while you ease along under wind power.

Stored in the boat........


Ready for some easy going........


The two lines coming back control the angle of the sail , I sit on them to hold them where I want them , Then use your paddle on the opposite side from the sail as a rudder. If the sail is on the left the paddle is on the right and reversed if the sail is on the right.

Chuck

Hi Chuck, a couple of observations.

A canoe under sail should exhibit "weather helm". Meaning it wants to turn into the wind. The opposite condition, "lee helm" is dangerous as the boat turns away from the wind and can actually sail away from you in a capsize. This can be adjusted by balancing the rig and load to the boat.

From your pictures it looks like the sail is too far forward and the leeboard is too far back. A leeboard should be directly under the center of effort (CE) of the sail, which on your sail should be at least a foot further forward.

The CE should be placed just over the center of lateral resistance (CLR) of the boat plus10% lead to account for heeling.

There are formulas to determine where the CE and CLR are.. You can find them on the net. Michalaks website has some good examples.

One tip is you state you hold your paddle on the opposite side of the sail to steer. In a properly balanced sailing canoe it is opposite (same side as sail) because the boat wants to roundup into the wind.

Once you get your sailing rig properly balanced to your canoe, and if you have enough leeboard in the water, you should be able to sail within 110 degress to the wind, in other words tack upwind!

Great info there. Thanks.

hoz

Thanks for the information. As you might of have guessed by now , I'm no sailor , paddler ...YES...sailor ...No.
It was something I rigged up for a down wind run when in open water and it sure beats paddling over those wide areas.

Chuck.

hoz,

In that most of the boats (but not all,) discussed on this Forum have very symmetrical hulls, I'd think that the CLR should be at 50% of the waterline length. When that isn't the case, the easy way to determine the CLR is to make a cardboard cutout of the underwater profile and see where it will balance on a ruler. (Not a neat, scientific formula, but it works!)

That's why I've been thinking that it might be better to place the mast much further back than the one in Chuck's picture. (Sorry Chuck!)

If the lee-board was placed pretty much at the center (half the hull length,) the mast placement would then depend upon the sail's Center of Effort.

To find that, the CE, all you need to do is to draw a line perpendicular to each side of the sail, starting at the center of each side, and where they call cross would be the Center of Effort.

If those lines don't cross at a single point, then they will form a small shape, and the center of that shape will be your CE.

Place the mast so that newly-found point is just ahead (10% of the waterline length) of the middle of the boat, and it should balance nicely.

Now that you've got me thinking about all this, I guess I'm going to have to work something up for my Southwind build. . .

Mike S.
Spring Hill, FL