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February 1, 2004
Crabclaw Cat Update
By Fred Shell
This is an up date on the Crabclaw Cat design which I have been working on for the last three years or so. I am writing on my laptop computer aboard my boat Crabby, selfsteering at about 4 knots in a light breeze on Lake Champlain.
The design has finally evolved to the point where I can consider it complete and, more amazing, it is even a moderate commercial success. Deb (my wife) and I recently returned to Vermont from a trip to San Diego to deliver a finished Crab. A kit was sent to Thailand this winter. The boat was built on the beach there and is currently being sailed off the beach around the area of Phuket. My prototype will be moving to Maine this summer and I will be replacing it with a totally current model which will be ready to sail by the end of July.
The design has been changed in two major ways. First, the crab mizzen has been replaced with a leg o mutton, and second, the hull shapes are now hard chine with narrow flat bottoms instead of simple V. The crab main is a wonderful sail, very easy to set up and handle while producing lots of power with little heeling moment. I like to use the mizzen as an air rudder to promote responsive tacking and reliable self-steering. The crab sail likes to just keep going straight and so doesn't make a very good control sail. The leg o mutton, with its self vanging properties, makes an ideal mizzen.
The slightly more complicated flat bottom hulls have replaced the "simple" V because they improve performance and, as it turns out, are easier to build from the kit. They go together in a more controlled step by step process that reliably produces a sound and true boat. Okay, I'm back out on the boat, about two weeks later. I left this morning at about 9:15 for a circumnavigation of North Hero Island, a total distance of about 35 miles with some open waters (about four miles across), some narrow channels and a couple of low bridges. One bridge with a clearance of 18' required dipping the yard, which takes less than a minute. The weather forecast was for mostly cloudy, chance of showers. Well, I did get some rain but, of course, stayed dry in the cabin. There was a nice sailing breeze for the first half but it has been dead calm since and looks to be for the remaining three miles or so.
Now that I broke down and bought a gas outboard these longer day trips are very relaxed, knowing that I will be able to get home. The motor is a 4hp Yamaha 4-stroke. I am sitting in the cockpit with the cabin rear windows closed and the noise is not enough to interfere with normal conversation. It is set at about 1/3 throttle and we are making 6mph. The top speed is 7-8 mph. I still have an electric mounted also and find that it gets a lot of use for quick maneuvering and when quiet running is called for. As much as I hate to admit it, the low rumble of the 4-stroke does have its appeal.
With a chance to build the new one I have been looking for things to change and improve. That's why I had to go sailing today, construction has started and any changes need to be decided on soon. I guess it's going to stay the same.
It's 3:00 in the afternoon and a breeze has come up for the perfect ending to this little voyage. The motor is off and Crabby is self steering and heading right for home. I expect to have the new boat finished just in time for a six-day trip on the coastal waters of Maine with my son in early August. It has been over 25 years since my last salt water sailing, and I am really excited about the prospect of seeing some of the Maine coast and trying out the latest Crabclaw Cat.
If you have any questions or would like more information on the Crabc1aw Cat or any of the other Shell Boats, feel free to call me, Fred Shelf, at (802) 524 9645.
About Knots
by Sam ChapinDid you think I had anything to say about the square knot? It is our most popular, except maybe the overhand. It is an uneven knot tied with two half knots, one right over left and then left over right That makes it look symmetrical. The attributes are that it is easy to tie, holds fast, and is easy to untie. If it is not pulled too tight or gotten really wet, one good pull on one of the loose ends will capsize the knot into a cow hitch on the end pulled (now straight). The cow hitch slips off easily. It is good for tying bundles and packages and reef in sails. That's why the other name is the "reef knot." The ease of untieing leads to it not being a good knot just to join two lines together. If it catches on the edge of something it can come apart. A sheet bend is a better knot for tying two lines together.
If you are worried about not being able to untie the square knot, it can be tied "slippery;" that is, with a loop pulled through one side so it is like a half bow. The thief's knot looks like a square knot, but it is not, and can't be tied by adding half knots. You must form a loop with one side and then weave the other end around it so that the end comes out on the side that it would not if it were a square knot. The story is that on the old square rigged sailing ships, the cook would tie up a bag of cookies with the thief's knot, and then if a seaman opened the bag to steal a cookie he would certainly tie it up again with a reef knot. The cook would know then without needing to count cookies. I don't really believe that because any good seaman would recognize the knot when he tried to untie it and could easily tie it up odd again.
If you tie a granny knot (which is symmetrical, as left over right and then left over right) and it is rather loose, you can pull sharply on one free end and find that you have a clove hitch tied on a straight piece of line. The granny knot will slip and, if it is tight, it is the devil to untie. Notice that part about the slipping.
Doctor C.W. Mayo of the Mayo Clinic devised a knot to tie off the cystic duct. The cystic duct is deep in the bottom of the hole he did gall bladder surgery through. Doctor Charlie would tie a granny knot in the ligature around the duct up where they could manage it and put his finger on the tied knot and slide it and tighten it around the duct. Then he would add a half knot that would make a square knot out of the last two half knots so that it wouldn't slip back. Doctor Charlie visited me once when I was about 14 years old and sick. He was in town for a medical society meeting and my doctor uncle brought him by to see his sick nephew. Dr. Charlie sat at my bedside, examined my wound, nodded his head and said, "Wilber, I think you are going to save this boy. Just keep giving him that new wonder drug, sulfanilamide." I think the consultation was free. I never heard of a bill. Neither of us mentioned the granny knot.
The other knot that surgeons use to tie off big bundles, when they don't have a finger to hold on the first half knot to keep it tight, is the surgeon's knot. It is a square knot except the first half has an extra twist so there are three passovers in the first half knot. That gives enough friction so the knot tends to hold itself until the second half knot is pulled down.
The bow knot used to tie our shoes and the bow on our hat is a square knot with the ends not completely pulled through. A good knot to tie up a bag of stuff or the drawstring of your swimming shorts is the bow knot modified. Tie the bow knot and then put an overhand knot in each end of the ends. Pull the bows so they enlarge and ends with the overhands tied in them are drawn up to the knot. Now gravity and centrifugal force will keep the knot tight. When you want to untie it reach in, get a hold on each of the ends with the overhands, and pull in opposite direction to undo the bow. Leave the overhands in for the next time that you tie the knot.
Have I mentioned macrame yet? I am told that it is Arabic for "square knot." You should probably ask an Arab about that but most of macrame is square knots, granny knots, half knots, and half hitches. And lace and knitting I won't mention.
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