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Sailing Skin-on-Frames
By:Paul G. Jacobson
Date: 3/20/2011, 4:52 am
In Response To: Re: Skin-on-Frame: Not a kayak, redux (Tim Abbott)

: Beautiful, Dave
: I'm planning on doing one like this too, soon:)
: I wonder - what do you think of the stresses a sail rig would put
: on a SOF sailboat like this?
: Can a skin boat handle it? Would you beef up anything because of
: the sail? What and where? -without adding too much extra weight.
: I live right on Lake Erie, and my boat would see some choppy
: seas on occasion - I wonder how SOF will handle it...
: Tim

According to legend, St. Brendan sailed a skin boat from Ireland to the new world sometime around the year 800. The style of boat is called a curragh, (hope I spelled it right) and it was skinned with cowhides. The idea has been around for a while! The most famous crossing of the Atlantic in a skin covered kayak was Dr. Lindeman's trip in the early 1950's in a Klepper. I believe he sailed part of the time. Kleppers are routinely sailed with factory-made sailing kits (mast, sail, leeboards) a very common accessory.

The skin is not an issue. What all sailed boats have to deal with is how the force of the wind is transmitted through the frame of the boat in order to propel the boat. The keel on some designs needs to resist side forces to keep the boat from moving sideways, instead of going forward, when the wind comes from the side. On many sailboats you will see a deep keel, or a moveable centerboard. On canoes and kayaks you'll see more often see leeboards mounted to the gunwales. Does about the same job, but in a different manner. If you are using a device which puts added stress on the gunwales, you would want to have stronger gunwales. At the same time you are not so worried about the strength of the keelson, that piece inside the boat which runs along the bottom and to which an exterior keel might be attached. No exterior keel, no worries about attaching one.

With most designs, the keelson and gunwales handle all the stresses. They are tied together at the ends, and connected through the length of the boat by thwarts, decking, ribs or frames. The forces on the SOF frame would be concentrated on the mast-rigging mountings to the gunwale and the mast step on the bottom of the boat. For the most part, as long as you don't poke the mast through the bottom of the boat, your concern will be about the strength of the gunwales. You should be able to upsize the gunwale cross section, fittings and ropes to the size of your sail. If you have a small sail you may be able to stick the mast through a wide thwart and not need any ropes at all. The bigger the sail the more power you are dealing with, and the larger the parts which handle that power will need to be. Of course when you decide you want a lot of power, then you are really saying you want a bigger boat.

That leads us to the "2 foot syndrome" where boaters suffer, and their usual complaint is that they would be happuer if their boat was just 2 feet longer. The only cure is an injection of cash and the purchase of a larger boat. Unfortunately the illness can strike again at any time. People who build their own boats do not have any immunity to this disease.

Hope this helps

PGJ

Messages In This Thread

Skin-on-Frame: Not a kayak, redux *PIC*
Dave Gentry -- 3/17/2011, 7:05 pm
Re: Skin-on-Frame: Not a kayak, redux
Paul Montgomery -- 3/18/2011, 12:22 am
Re: Skin-on-Frame: Not a kayak, redux
Paul G. Jacobson -- 3/18/2011, 3:03 am
Re: Skin-on-Frame: Not a kayak, redux
Dave Gentry -- 3/18/2011, 6:23 pm
What a beautiful boat! *NM*
Jay Babina -- 3/18/2011, 8:32 am
Re: Skin-on-Frame: Not a kayak, redux
Tim Abbott -- 3/19/2011, 11:31 pm
Re: Skin-on-Frame: Not a kayak, redux
Bill Hamm -- 3/20/2011, 12:24 am
Sailing Skin-on-Frames
Paul G. Jacobson -- 3/20/2011, 4:52 am
Shenandoah Whitehall *PIC*
Dave Gentry -- 3/20/2011, 12:16 pm
Re: Shenandoah Whitehall
Clayton Plunkett -- 3/20/2011, 10:00 pm
Re: Shenandoah Whitehall
Bill Hamm -- 3/21/2011, 12:40 am