Frank Kahr's Robote.
Contents:
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Jim Michalak
118 E Randall,
Lebanon, IL 62254Send $1 for info on 20 boats.
Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(15Aug00) This issue continues a series about sailing for nonsailors, this time about sailing on reaches and runs. Next issue, 1Sep00, will show some leeboard ideas.
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Frank Kahr's Robote.
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SAILING FOR NONSAILORS 3
SAILING ON A "REACH"...Reaching is sailing across the wind, more or less, like this:.
Keep in mind that the wind the skipper feels will not quite be the same as the true wind. He and his boat will feel the apparent wind which is the vector combination of the true wind plus his boat's speed. So he will feel the wind more on the bow of the boat.
Reaching is I think usually the fastest and safest point of sail and you can spend a very happy day picking a goal that is across the wind from your launch and zip back and forth all day on reaches. Things that are really critical when sailing to windward, like sail twist and having the board down exactly right are usually less critical when reaching. Wind shifts that stop you dead while sailing to windward have no effect.
I think reaching is so fast because the the force provided by the sail can be better aligned with the boat's motion, with less of it lost as side force to be counteracted by the board with its drag. The board is still down, but it often can be lifted a bit, and even then the "pounds per square foot" loading will be reduced compared to sailing to windward. You still need to tend to the sail and watch your wake to guess at the ideal combination.
I consider reaching to be safe because you can pretty well start and stop at any time by playing the sheet.
As always there are things to watch out for. One is that your boat will usually be aligned with the waves and they might cause a deep roll. That used to be a problem with my Jinni which had a fairly long boom. It would happen regularly at Carlyle Lake that we would get a 10 knot wind across 10 miles of lake raising big lollypop waves at the lee end of the lake. When reaching that wind was about enough to capsize the boat and I'd ease the sail out. But in the rolling boat that boom would swing out and threaten to drag into the water with each roll and that also could capsize the boat. Usually you can switch to a close reach or broad reach to meet the waves at a different angle to avoid the problem.
Another problem is that if you get caught reaching in a big gust the boat may capsize even if the sail is let out. The flapping sail can have enough drag to send you over. My Jinni capsized twice in the years I used it and once was in that way. I think the thing to do is maintain some steerage speed and point more into the wind. Your boat will have more stability than when laying across the wind, and you should be able to carefully play the mainsheet to keep the sail depowered and yet keep the boat moving enough for steerage.
RUNNING DOWNWIND...
Running downwind is usually not the fastest point of sail for raw speed - remember that your forward speed here will subtract from the speed of the wind. But it is often the fastest way to get from A to B because your speed will be so steady and unaffected by anything you do. Sail trim and high tech rigs have the least effect running downwind. The sow's ear can pass the silk purse sometimes sailing downwind.
But there are things to watch out for.
One is that when running downwind your apparent wind is reduced by your boat's forward speed and you can get a false idea of wind and wave conditions. Even when I'm sailing a long stretch downwind I make a point of swinging around into the wind every now and then to see what the return trip might be like.
Long ago I had a Snark Mach 2, a low board like boat, and took off downwind in a good breeze on a fabulous run. Eventually I stopped to turn to windward and the next wave washed right over the boat, as did every wave after it. It was a long wet trip back. When you are sailing downwind you not only feel a reduced wind, but you are usually encountering the flat backside of the waves getting a false idea of the sea state. Often it's not so much the wind that gets you, it's the waves.
What can happen is that the skipper takes off on a breezy downwind frolic only to find that his boat can't beat back against the waves stirred up by the stiff wind. Once I saw a fellow launch at Carlyle on a day I felt too breezy for sailing the Mach2. I sat there wondering why I'm such a chicken about such things. An hour later he was towed back by a power boat. He cast off his tow line about five feet from the dock and dove down inside the boat for his oars only to find he couldn't row against that wind. He got blown downwind well away from the dock and had to be rescued again!
But even running downwind in big waves is risky. That is how I capsized the Jinni the other time. You come flying down the steep backside of a wave, the bow digs in a bit and slows down. But the stern keeps charging ahead and tries to pass the bow! The boat turns sideways in the wave and rolls deep to leeward. An unballasted boat like Jinni will often keep going right over. You've "broached".
So keep an eye out.
Here are three boats running downwind:
Boats A and B are doing fine but boat C is "sailing by the lee" which means his sail is boomed out to the wrong side. Sometimes you don't know this is happening to you because you don't know the wind's true direction well enough. Often when sailing by the lee your boat will feel odd at the tiller. But you can see that if the wind shifts a bit or the boat turns the wrong way, the wind will come directly aft of the sail and the sail may "jibe" like this:
Jibing is considered to be dangerous for several reasons. If you jibe in strong winds it can be almost explosive. A large boom can kill you if it hits you in the head during the jibe. The shock of the boom coming to a quick stop can rip out blocks and cleats or snap a sheet. If the jibe happens by surprize and catches you sitting on the wrong side of the boat, you might capsize.
You can jibe safely, at least in mild winds, by using some care. Do it very deliberately and slowly and with the sheet in hand. As you turn the boat pull in on the sheet until the sail jibes and then use your grip to ease the shock of the jibe. I think most sailing races have their courses set out so there is usually a jibe required.
But when sailing alone you may need never jibe. This works:
Boat 1 wants to change heading to port (left looking forward) but that would mean a jibe when the wind passes aft of the sail. So instead he swings to starboard (right looking forward) through about 270 degrees, pulling the sail's sheet in as he goes, tacking through the wind and over to the other side. He ends up in position 2 without ever jibing. This works quite well, I do it all the time myself.
You can't stop a boat that is running downwind without turning it back into the wind.
They say the clam tongers used to run downwind in the old days by releasing the sheet and letting the sail streamline forward of the boat. They may have gotten away with that in very mild weather, but don't try it at home. When the sail swings forward the sheet will no longer have leverage to pull it back! I think Edgar Allen Poe once wrote a short novel where he and his buddies went out in a catboat in a storm and had to ease the boat by cutting the sheet and letting the sail streamline forward. Before the story ended they had to draw straws to see who would die so the others could survive by eating his body! But Poe brings up a good point - a boat can be overpowered when running downwind, especially if it has a small shallow rudder and a long boom like the catboats Poe might have seen in his area. The rudder might not be able to hold the boat on course downwind and the boat will spin around on its own to face the wind. Often in that case you can still "tack" downwind by sailing on broad reaches. My original WeeVee was like that until I put on my usual deep kickup rudder. Then it behaved.
Somewhat related to the rudder subject is what to do with the board (leeboard, daggerboard, or centerboard) while running. You can try to raise it, or let it float up on its own in some cases since there will be little or no side force on it. But almost any boat will handle better with the board down somewhat.
And boats with small bows and big sails can "pitchpole" end over end. I don't think that will happen with any of my boats but catamarans are famous for pitchpoling.
Hope I haven't scared you off. Sail in mild winds and have fun and be safe. Think twice before venturing out in white caps.
NEXT TIME...
I'll discuss some leeboard issues.
Contents
ROBOTE
ROBOTE, LIGHT ROWBOAT, 14' X 45", 60 POUNDS EMPTY
Robote was designed for Frank Kahr of Rhode Island strictly as a rowing boat, very light and simple and fast and seaworthy. Frank had started a few years back with my WeeVee design shown here:
What surprised both Frank and me was that both of our WeeVee's would row at 4 mph, blinding speed for a 7-1/2' boat! WeeVee has a deep V center, 42" wide and 9" deep with a lot of rocker and no twisting to the bottom panels. It's actually pretty seaworhty too but is tippy if you are not seated. It's not for everyone.
I followed WeeVee with the less extreme 12' Vireo shown here:
Vireo has a 6" V on a 42" beam so is more stable. And it has a pointy bow. The bottom planks in Vireo twist in the bow to make a wave cutting deeper V. Frank built the boat shown and rowed some long stretches with it. But he thought I was on the wrong track. WeeVee's deeper V and untwisted panels were the way to go, he said. How about a 14' boat with the same cross section and untwisted panels but with a long pointy bow? Here are the lines we agreed on:
Frank built the boat, which he called Robote, from three sheets of Okoume plywood with taped seams. It went together easily as longer boats with gentle curves often do. He said it weighs about 60 pounds, light enough that he can carry it on one shoulder for a short way. Here is Frank first time out with Robote:
Frank entered himself and Robote in the Blackburn Challenge, where one has to row about 20 miles around Cape Anne in Massachusetts, most of it on the open ocean. But it wasn't meant to be and he wrote:
"Wind was SE 15+, rising, with 2-3' chop off the ocean. I rowed about 10 miles, then ran for cover in Pigeon Cove. The alternative was several more miles of windward slog followed by more miles of crosswind. It would have been too much for me."
"The boat was dry, in good control always. It will cope with conditions in which you have no business being out."
If I had seen that forecast I would have left my boat on the cartop. I haven't yet seen any photos of this year's race, but the results of 1999 and 2000 races are posted at www.blackburnchallenge.com. Last year 2 entries scratched and this year 35 scratched! But that brings up a very good point. Good rowboats with experienced hands can handle those conditions for a while but you shouldn't set off into them if you can avoid it. You can get "blown away", especially if anything goes wrong, such as losing an oar or rowlock. And the same is true for any sort of power or sail boat - a small failure in moderate conditions can bring on a disaster. My own rule of thumb is to not venture out too far in whitecaps.
Another subject came up between us, the fact that almost any good conventional rowing boat that has no extremes will row about 4-1/2 mph and no faster, at least not in a long row. My Roar2, Sportdory, RB42 and now Robote all go about that speed. Frank adds:
"I agree with your observations about good plywood rowboats. While robote is not a real speedster, it is very pleasant and responds to greater effort with greater speed. Beaching is no problem; in calm water just lean over so one side of the V is horizontal. The boat grew on me during my 2 weeks on Cape Cod and is now beached at a town landing, to be used weekends the rest of the summer. One of my adventures involved a sudden storm with 2' chop crashing on the beach at South Monomoy when I needed to launch to return home; this wasn't pretty, but I got away on the second try.
Plans for Robote, Vireo or WeeVee are $20 each.
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 hull has been glassed, painted and turned and is now ready for interior work. The water ballast tanks are complete, one coating with glass/epoxy and the other just with epoxy for a scientific test. The builder's past experience with a boat this size is that if the sun doesn't hit the plywood you don't need the glass fabric to keep the ply from checking. But if it does, as with the decks, epoxy coating alone won't keep the ply from checking.
Jon Jr has been completed by Joe Leinweber and Dan Ellis and tested to a certain degree. Click here to read about the test and the surprize ending! ("The waters are only safe until next time!")
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.
Slam Dink: Slam has been completed and sailed as you see here. The kids did a great job! Waiting for a test report.
AN INDEX OF PAST ISSUES
Herb builds AF3 (archived copy)
Hullforms Download (archived copy)
Plyboats Demo Download (archived copy)