Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(15Jul00) This issue starts a series about sailing for nonsailors. Next issue, 1Aug00, will continue the topic.
Craig O'Donnel has a great web site for small boats at Cheap Pages . He's adding to it all the time. Right now he has posted there the complete copy of ALONE IN THE CARIBBEAN, by Frederic Fenger, a classic tale published in 1917 about cruising the Caribbean Islands in a 17' sailing sea canoe.
SAILING FOR NONSAILORS 1
BACKGROUND...
I don't claim to be a great sailor or even a good sailor. There are some good texts out there about the subject. Alas, many texts get you into details so deep you won't see the forest for the trees, or assume you have fancy equipment. So I'm going to try handing out the basics, the minimum you need to know.
This one is for those of you who are going to build a sailboat and have never sailed and don't live in areas where you can expect to get any instruction. There are lots of you out there. Take heart. Here is a full description of my sailing lessons:
Around 1980 I decided to start boating and bought one third interest in an old Hobie 16 with John and his son Greg. John and I had never sailed but Greg, about 20 years old at the time, had a job where he could sail during the day and work at night. One day he took John and me out for our first lesson. He rigged the boat by himself and sailed it with John and me as passengers to a bank about 1/4 mile from the dock, got off, told us he was late for work and left us there! That was it! We had to reinvent sailing to get back to the dock and I guess we did.
If you can get a lesson or two from another guy with a similar homemade boat you will learn a lot. A messabout is a great place to start. I don't really know what to tell you about clubs that race or call themselves yacht clubs. Most of them there won't understand the reason for your homemade boat. Most of them know a lot more than I about sailing but you may get trapped into a racing or drinking scene.
THE VERY BASICS...
Here is a diagram (from overhead looking down) of the wind blowing on a sail:
The sail here is at an angle of about 20 degrees to the wind and the sail bellys out a bit. The amount it bellys out is called the "draft" of the sail and the draft is typically about 10% of the width of the sail, so a sail 10' wide might belly out 1'.
The wind produces a force on the sail which is shown here as the "net force".
It is possible to show a force, in this case the net force, as the sum of two components. Things like forces have both magnitude and direction and are called "vectors". One of the neat things about vectors is that you can think of them as the sum of other vectors. In this case the net force is shown as the sum of two other forces. One of those forces I'm calling the Drag and it is in line with the direction of the wind. The other force component of the net force is I'm calling the Lift and it is perpendicular to the direction of the wind.
In the case shown the sail is acting as an airfoil and from what I've sketched in it looks like the ratio of the Lift to Drag is about 3 to 1. That might be typical of a low tech sail. (Really high tech airfoils, such as the wings of a sailplane can, I think, achieve a Lift to Drag ratio of 50 or 100 to 1. Occasionally a high tech sail boat is made with a sail like an airplane wing to tap into that potential but they can be too fragile and complex for general use.)
NEXT ADD A HULL...
Here is the very same sail and wind with a hull added underneath:
The net force is also exactly the same magnitude and direction as in the first diagram. But in this diagram I've shown the net force resolved into two forces that are aligned with the boat hull, not the wind. One of those forces is a side force on the hull, and the other is a forward force on the hull.
What you see here is the situation of a boat "sailing to windward" or "close hauled" or "beating to windward". It can't go straight into the wind. In fact it usually can't sail closer than about 45 degrees to the wind. If you tried that the force vector pulling the boat ahead would disappear, you would get all side load, or a big side load and maybe a force pushing the boat aft!
Even as it is the side force on the close hauled hull is a lot bigger than the forward force. A keel or daggerboard or centerboard or leeboard is needed to keep the hull from being pushed sideways. There is no getting around that and the design of such features is very important. The side forces caused by the sail and reacted by the boat's keel don't line up, of course. The sail is way up there and the keel in way down there. The result is that the boat will try to tip over. It usually can't tip over all the way because as the boat tips the buoyancy of the side being forced down into the water increases. The total buoyancy of the hull (which equals the boat's weight) no longer aligns with the boat's center of gravity, the resulting torque caused by the new alignment will balance out the torque caused by the sail/keel situation. See the diagram below. (The same effect can be got by shifting the center of gravity of the boat usually by sitting the crew to the windward side of the hull.)
That small forward force acellerates the hull until it reaches a speed where the drag on the hull is the same as the forward force. More about that later.
NEXT WE "REACH"...
Next the skipper swings the boat about 45 degrees away from the wind such that the hull is at right angles to the wind. In this diagram the sail and wind and net force are exactly as before:
This is called "reaching". If the skipper were sailing a bit closer to the wind it would be a "close reach" and if he were heading a bit more downwind it would be a "broad reach".
Notice that now we have a lot more forward force and a lot less side force. Reaching is usually about the fastest way of sailing. It is often one of the safest, too. You can stop quickly at any time by releasing the sheet to the sail and letting it swing out to stop the forward force.
Often a skipper sailing on a reach will find his boat acellerating so much that he needs to pull the sail in tighter. Remember that the sail does not feel the wind that one feels when standing still (the "true wind"). Instead it feels that true wind plus the wind caused by the motion of the boat, the total of those two being the "apparent wind". For example if the true wind were 10 knots from the north and the boat speeds up to 4 knots to the east, the sail feels an apparent wind which is the vector sum of those two. In that case the apparent wind would be 10.8 knots from a direction of 22 degrees east of north. Really fast sailing machines, iceboats in particular, generate a lot of their own wind.
NEXT WE "RUN"...
Here the skipper has steered off the wind another 45 degrees. This might be called a broad reach but it is beginning to be a sail downwind, a "run":
There is still a small side force but the main push is forward. The hull speed will start to subtract from the true wind speed so the apparent wind will decrease below the true wind speed.
If you need to stop quickly in this situation, you may not be able to do it. You must swing the boat back into the wind.
NEXT TIME...
I'll show some finer points about sailing to windward.
IMB
IMB, SAIL BEACHBOAT, 13-1/2' X 5-1/2', 350 POUNDS EMPTY
I haven't really gotten a test report of this boat yet but the photo above taken on its first sail shows to me that it must be pretty close to "right". The prototype was built by Jerry Scott of Cleveland, Texas. (This boat was originally drawn for a design competition sponsored by International Marine Publishing a while back and was called the International Marine Beacher, or IMB. I didn't win anything (again).)
IMB features a "Birdwatcher" cabin. Birdwatcher cabins are full length with panoramic watertight windows and a center walkway slot in the roof. Everyone rides inside including the skipper.
Around 1984 Phil Bolger showed me a cartoon of his 24' Birdwatcher and I didn't know what to think of it. He presented it in a 1986 issue of the old Small Boat Journal. Ron Mueller built the prototype and convinced me that this cabin really works. I built the second Birdwatcher and here is what I found:
These boats can be self righting without ballast because the crew weight works as ballast. They sit down low on the floor looking out through the windows (although I found standing in normal winds was quite acceptable). In addition, the high cabin sides provide lots of buoyancy up high to ensure a good range of stability. IMB, which is small and has no ballast, will probably self right from 60 or 70 degrees of heel, but the larger ones such as the water ballasted Scram will self right from a full 90 degrees knockdown. Others like the original Birdwatcher and my Jewelbox have 1" thick bottoms which give enough weight down low that they self right from a "windows in the water" knockdown.
These boats can be operated totally from within the cabin, like an automobile. No one need ever go on deck. For boating with children I can see no equal.
These are cool boats. The tinted Plexiglass windows cut the sun's power. The crew can always sit in the shade of the deck. Downdraft from the sail cascades through the walkway slot.
IMB has an 8' long cabin on a wide multichine hull, sort of an enlarged Piccup Pram hull.
IMB takes two sheets of 1/2" plywood, 8 sheets of 1/4" plywood and one sheet of 3/16" dark tinted Plexiglass. Taped seam construction using no jigs or lofting. Sail is 104 square foot balanced lug with pivoting leeboard.
Plans for IMB are $30.
Prototype News
Some of you may know that in addition to the one buck catalog which now contains 20 "done" boats, I offer another catalog of 20 unbuilt prototypes. The buck catalog has on its last page a list and brief description of the boats currently in the Catalog of Prototypes. That catalog also contains some articles that I wrote for Messing About In Boats and Boatbuilder magazines. The Catalog of Prototypes costs $3. The both together amount to 50 pages for $4, an offer you may have seen in Woodenboat ads. Payment must be in US funds. The banks here won't accept anything else. (I've got a little stash of foreign currency that I can admire but not spend.) I'm way too small for credit cards.
Here are the prototypes abuilding that I know of:
Caprice: A brave and experienced builder in Texas is making the 25' Caprice water ballasted sailboat. A big project. Here the bottom is being painted. I'm told the boat is now ready to turn over.
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We also have the start of a Jon Jr, a 12' x 3' personal sized jonboat, down in Texas. Here is the latest photo with the bottom going on.
Mayfly12: A Mayfly12 is going together up in Minnesota. It is now completed and has been sailed. Waiting for final photos. Here is a construction photo from last summer.
Robote: Robote is supposed to be a fast somewhat extreme rowing boat based on my old WeeVee design, thus it has a deep V bottom but is stretched out to 14' long with a very pointy bow. It was drawn as a custom job but if it works out I'll put it in the catalog. The boat is now complete and launched but waiting for final photos and test results. Here is a preliminary photo on its first row with builder Frank Kahr at the oars:
Slam Dink: Here are a couple of kids working on the prototype Slam Dink. I'm told bending the chine logs into position was quite a chore requiring several tries - not unusual for a short fat boat.
Herb builds AF3 (archived copy)
Hullforms Download (archived copy)
Plyboats Demo Download (archived copy)
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