Jim Michalak's Boat Designs
1024 Merrill St, Lebanon, IL 62254
A page of boat designs and essays.
(15 August 2019) We take a look at rowing. The 1 September issue will continue the topic.
THE BOOK IS OUT!
BOATBUILDING FOR BEGINNERS (AND BEYOND)
is out now, written by me and edited by Garth Battista of Breakaway Books. You might find it at your bookstore. If not check it out at the.... ON LINE CATALOG OF MY PLANS......which can now be found at Duckworks Magazine. You order with a shopping cart set up and pay with credit cards or by Paypal. Then Duckworks sends me an email about the order and then I send the plans right from me to you.
ROWING1
If you've ever cycled, you've rowed. In a lot of ways the two activities are similar. The gear can be very simple and cheap or very complex and expensive. The effort can be very relaxed and enjoyable, or very high strung and demanding. Also, the weather makes all the difference in the world in either sport as to the what can be accomplished.
This essay will explore mostly the simple, cheap, relaxed and enjoyable side of the sport.
FIXED SEAT ROWING
Figure 1 shows a fixed seat rower. His rear is attached to the boat by friction to the seat. His feet should be braced against solid foot braces. The handles of the oars are usually about chest high, or slightly below, when he pulls. The oar handles may overlap each other during some portions of the pull, although it's more comfortable for the casual rower if they don't.
The oars are held to the boat by common pivoting oarlocks. They are somewhat free to slide in and out of the locks such that the distance from lock to handle can be adjusted.
The blades of the oars are dipped into the water with each power stroke and lifted clear with each return stroke.
That's about it.
Here is what the oars do: In effect they are levers that gear up the speed of the rower's hands.
Most people in a good (but not racing) row boat will pull at 25 to 30 strokes per minute. Let's say it's 30 strokes per minute (2 seconds per stroke) to make the figuring easy. And let's say that stroke consists of 1 second of power and 1 second of recovery. If the rower pulls the oar handles through 3 feet with each pull, as shown in Figure 1, then the oar handles are moving 3 feet per second, which is 2 miles per hour.
(One might argue that hull speed and blade speed aren't the same because there is some slippage of the blade in the water. Certainly this exists when you try to start any boat from rest, especially a large heavy boat. But once up to speed in good conditions good rowing boats don't exhibit much slippage. I've noticed that an oar blade produces a small vortex on the water's surface when the power stroke is first delivered, and another small vortex, twisting the opposite way, when the power stroke is stopped, usually when the blade is lifted for recovery. In calm water the vortices are very clear and stay that way for a while. You can row along and see a string of them on each side of the boat. I base my observation that there is little blade slippage on the fact that the starting and stopping vortices of each paddle dip are usually only inches apart once the boat is up to speed, while the paddle dips themselves are spread well apart. Pete Culler said that a good rowing boat will carry or glide about the length of its hull in between strokes. I agree. So a good 16 footer will glide about 16 feet between strokes while its blade vortices might be within 6" of each other. Blade slippage would be 2 or 3%.)
How fast will the boat go? Here the problem is how to match the power delivered by the rower to the power required to push the hull through the elements. (The elements for the time being will be assumed to be just the drag of calm water. That is to say it is a windless and waveless day.)
What is the power of a typical rower? I don't really know. I'm sure there is a very wide range of abilities. I recall that one might expect a long distance recreational cyclist to put out about 1/10th horsepower for hours at a time. Bike racers apparently can pedal 1/2 horsepower for a good while. And I think I saw in Scientific American a long time ago where a multi-time Tour de France winner pushed a dynamometer at a full horse power for an hour!
It's interesting to guess at the load on the oar handles while pulling them at 3 feet per second. A horsepower is defined as moving 550 pounds through 1 foot in a second, (established back in the old, old days when horses were used to lift seepage water out of mines) so 1/10th horsepower would be 55 pounds through 1 foot in a second, or 18.3 pounds at 3 feet per second. But the rower, unlike the cyclist, is actually pulling only half the time, on the average, since half of his time is spent in a powerless return stroke. So his boat might think he is putting out 1/20 hp on the average.
Well, we're not out to win the Tour de France. To a certain extent with a rowing boat, the issue of power delivered becomes moot. The nature of hull drag for boats that don't plane assures that they all go about the same speed. Figure 2 shows what I think the power requirements might be for a boat like my Roar2 in normal one man rowing trim. (These power figures are all guesses.) You can see that power required rises sharply at a hull speed of about 4.5 mph. With a steady 1/20 hp of our rec rower she wants to go 3.5 mph. With 1/10 continous hp, say a maximum power for a short burst of arm power, or an easy continuous power for a small electric trolling motor, she wants to go 4.3 mph. The Tour de France winner might go 7 mph if his arms were as strong as his legs. A tenfold increase in power gives only about a twofold increase in speed.
The point is that large increases in power give only small increases in speed once "hull speed" is neared. So for recreational use it's wise to think in terms of easy steady power that you can maintain for hours, if needed. The big power can be held back for use in hard conditions like pushing into a wind, through a current, or past some rough water.
So let's say the skipper is pulling the boat through the water at 4mph. But his hands are only moving 2 mph! The oar makes the difference in speed easily possible.
If the oar were 84" long (7 feet), and 56" of that were outside the lock, and 28" were outside the lock, then a 2 to 1 ratio will be achieved.
Figure of 3 shows the "freebody" diagrams (the balance of forces) of the oar and the rower and the boat. With the configuration shown the 18 pound load as a 9 pound load on each handle is balanced by a 4.5 pound load on each blade. So the process of gearing up the speed by a factor of 2 has also reduced the balance load on the blade of the oar by a factor of 2.
The forces on the rower's body are also shown in Figure 3. His 18 pounds of force in his hands must be reacted to the boat some way. If he has no feet bracing at all, then the force goes out of his body as friction where he sits. It can hurt a bit after a while! The usual solution is to brace the feet solidly. A handy bulkhead or hull frame might do. Custom cleats for the feet to push against attached to the hull are also common.
If the rower now turns downwind he may find his 1/10th half time horse will push the boat at 5 mph. To get that without changing his stroke he can slide the oars out so that he has 24" inboard and 60" outboards. As shown in Figure 4 he will now have 3.6 pounds of force at the blade of the oar. Less force is required there now since the wind is helping to push the boat along.
Now let's imagine the rower encounters a headwind that slows the boat to 3 mph. How does he match his 1/10 th intermitant horsepower to the new speed? If the rower slides the oars in so that 32" is inboard of the locks and 52" is outboard, his 2mph, 9 pound application at each handle will be geared up to 3.2mph at the blades. As shown in Figure 4 the blade will balance now with 5.5 pounds of force at the blade. That's an increase over the first condition and it's that extra blade force that will help push through the headwind.
One can see from the above discussion that rowlocks that are pinned to the oars in one position don't allow this change of gears, so to speak. (They may have other advantages. More on that later.) By moving the oars in and out over an 8" range we have "regeared" the boat speed to vary over 50% without changing the handle force or speed.
And one can see that the total length of the oar might not really enter into the discussion, only the location of the pivot point effects the gearing of the oar. But the length of the oar does have effects. The longer the oar the less of an angle it will sweep through and the more efficient it becomes. Also the oar must be long enough so that the handles fall conveniently at the hands. But an overly long oar can be a problem, too. An overlap of the handles that many might find very awkward will develop. And the long oars may simply be a bother in confined rowing areas.
Cormorant
CORMORANT, CABIN SAILBOAT, 32' X 8', 2500 POUNDS EMPTY
Cormorant is the largest boat I've ever designed. I always warn folks to think twice and three times before building a big boat because you can buy a good used glass boat for less, maybe a lot less. But a homebuilt boat can have features that aren't available in a production boat and so it is with Cormorant. This one is really a 20% enlargement of Caprice.
Straight enlargements rarely work perfectly and so it was with Cormarant from Caprice. (Don't forget that Caprice was an enlargement of Frolic2, etc., etc., right on down to my Toto canoe.) In this case I narrowed it from a straight enlargement to keep the width within simple towing limits since this large boat is supposed to live on its trailer most of the time. The layout is quite similar. The idea is that the adults sleep in the center cabin and the kids sleep in the forward room.
Like Caprice, Cormorant has water ballast, over 1000 pounds of it. Total floating weight with family is going to be up to 4500 pounds. You don't tow a boat this large behind a compact car but I think towing this sort of weight is common today, all done with expensive large trucks I'm afraid.
The sail rig looks pretty modest with a 207 sq foot main. I'll bet it is enought since this shape is easily driven. I don't think you can go any larger and still hope to handle it without extra crew and gear.Tthe lug sail shown is similar in size to Bolger sharpies and they seem to get by OK. Experience will show if it is too big/too little.
Constuction is taped seam, with no jigs or lofting. Unlike smaller designs this one does not come with a plywood panel layout drawing. Over the years I've learned two things about the ply layout page. First is that almost no one uses it. Second is that with a larger boat the work of finding and drawing and fitting all the pieces to the boat on scale plywood sheets overwhelms all the other work. So part of the deal with doing the design was that there would be no plywood layout drawing. However this is still a true "instant boat" in that all of the parts that define the boat are drawn in detail and you can scale them up on plywood, cut it out and fasten together with no need for lofting or a building form.
Garth Battista, who is a book publisher at Breakaway Books where he publishes sporting books including my Boatbuilding For Beginners (And Beyond), is a true boat nut and has worked himself up from dinghies and canoes to the big Cormorant. He took it initially on a quick shakedown run on a lake near his home and shortly later to Long Island Sound for a week with his family. Here are his comments:
"We had an amazing time living aboard Cormorant (christened "Sea Fever") in Provincetown harbor for 5 days. The tide there was rising and falling about 12 feet a day with the full moon. We'd be high and dry up on the beach for breakfast, swimming off the boat at lunchtime, walking the flats again by dinner. It was a blissful time for me and my wife and two girls. We moved around, took little sails here and there across the harbor (West End to Long Point, then to the lighthouse, then to the East End, etc.) anchoring here and there, usually just running it aground as the tide allowed and staying for a while. Many shells were collected, and tidal pools investigated. Of all the harbors I've ever seen, it is the most alive. It's a couple of miles across and fresh sea water flushes the whole place twice a day. The number of snails, clams, crabs, fish of all sizes, mussels, eelgrass, etc. was just mind-boggling. On high tides I'd go spearfishing (many attempts, no luck) where at low tide I'd been walking around.
We rigged a 8' x 15' white tarp with tent poles running crosswise as a canopy over our cockpit and hatch, supported along the mast folded down in the tabernacle, so we could escape the mid-day sun. Most days were hot and humid and mild, with only gentle winds. We rode out a nighttime thunderstorm with no trouble, just stayed up and watched the lightning. We attended a few wedding-related events, just walking ashore for one party, and for the wedding itself we returned late at night and rowed our dinghy out to the boat, our sleepy children just awake enough to get themselves aboard.
For our last two days we gave up the shallow-water life and sailed from P-town down to Wellfleet, about 7 miles, surfing along on gentle 3-foot waves with a following wind. We beached the boat at Great Island, walked the beach, had a picnic dinner, swam and played, spent the night, and left the next morning at 6 a.m. to beat the falling tide. Our weather radio mysteriously quit working that morning, so all we had was the prior day's forecast of 10-15 knot winds from the SW.
The wind had shifted into the west during the night, so we had to beat out of the harbor, and once we turned north to return to Provincetown, huge rollers were coming in off the bay, more or less directly into our port side, lifting us, rolling us, occasionally breaking and spraying water into the boat. We stayed well offshore to avoid the breakers in by the beach -- but with the falling tide it seemed that we needed to be nearly a mile out. It went from exhilarating to worrisome to mildly terrifying as we neared P-town and the wind kept picking up, past 20 knots to 25 and higher in gusts, and the waves just kept growing. The swells were in the 8-10 foot range, with a high percentage of them breaking at their tops, whitecaps everywhere.
But bless this boat! With its 1000 lbs. of water ballast, and the leeboard mostly up, we were able to bob and roll and slide over nearly all the swells. The worst of them were very steep and threw us sideways, maybe tilting us to 40 or 45 degrees briefly. We had two reefs in the main and the mizzen rolled down to about half-size, and still we blasted along on this nasty rollercoaster of a beam reach. It was the sort of trip that would be scary fun if it was just you and a buddy, but it's awful when you have your loved ones aboard, and you wonder who might get thrown overboard, and how you'd managed a rescue in the rough conditions.
Anyway -- the white knuckles got to relax as we finally made it past the P-town breakwater, and with great relief ran her aground out on the flats. The gale (or near-gale) continued to blow all day, kicking up 3 and 4-foot waves even in the protected areas of the harbor. The only boats we saw going out were an 80-foot schooner and a big whale-watch boat. A lobsterman we talked to later said he'd stayed in as it was too rough to check his traps.
We had a hell of a time taking the boat out and getting her on her trailer for the trip home -- but all worked out in the end, with the assistance of some very kind strangers; and I'm left with the memories of incredibly happy days. -- And an incredible boat.
All best, Garth
P.S. Jim -- I should also mention that on Sunday afternoon as we turned the corner from our run down to Wellfleet to the close reach upwind toward the inner harbor, the boat just drove perfectly. It seemed we made 40 degrees off the wind. That maybe wishful thinking, but it was an angle far better than I'd imagined a lugsail could manage. It was a joy to sail, in all conditions. My hat is off to you.
P.P.S. The number of people who came over to admire the boat and exclaim at its uniqueness, its coolness, its obvious functionality -- well, they were beyond count. "
One more thing, Garth sent me this photo of himself working hard on his new sports book:
Plans for Cormorant are $60 when ordered directly from me.
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.
We have a Picara finished by Ken Giles, past Mayfly16 master, and into its trials. The hull was built by Vincent Lavender in Massachusetts. There have been other Picaras finished in the past but I never got a sailing report for them...
And the Vole in New York is Garth Battista's of www.breakawaybooks.com, printer of my book and Max's old outboard book and many other fine sports books. Beautiful job! Garth is using a small lug rig for sail, not the sharpie sprit sail shown on the plans, so I will continue to carry the design as a prototype boat. But he has used it extensively on his Bahamas trip towed behind his Cormorant. Sort of like having a compact car towed behind an RV.
And a Deansbox seen in Texas:
Another prototype Twister is well along:
A brave soul has started a Robbsboat. He has a builder's blog at http://tomsrobbsboat.blogspot.com. (OOPS! He found a mistake in the side bevels of bulkhead5, says 20 degrees but should be 10 degrees.) This boat has been sailed and is being tested. He has found the sail area a bit much for his area and is putting in serious reef points.
AN INDEX OF PAST ISSUES
THE WAY BACK ISSUES RETURN!
MANY THANKS TO CANADIAN READER GAETAN JETTE WHO NOT ONLY SAVED THEM FROM THE 1997 BEGINNING BUT ALSO PUT TOGETHER AN EXCELLENT INDEX PAGE TO SORT THEM OUT....
THE WAY BACK ISSUES
1sep18, Measuring Prop Thrust, OliveOyl
15sep18, Taped Seams, Philsboat
1oct18, Plywood Butt Joints, Larsboat
15oct18, Small Boat Rudders, Jonsboat
1nov18, Sink Weights, Shanteuse
15nov18, Piccup Spinoffs, Piccup Pram
1dec18, Electric Boats 1, Ladybug
15dec18, Electric Boats 2, Sportdory
1jan19, Sail Area Math, Normsboat
15jan19, AF3Capsize, Robote
1feb19, Bulkhead Bevels, Toto
15feb19, Leeboard Issues, IMB
1mar19, Hollow Spars, AF4 Breve
15mar19, Underwater Board Shape, Harmonica
1apr19, Polytarp Sails 1, River Runner
15apr19, Polytarp Sails 2, Mayfly16
1may19, Sail Shaping, Blobster
15may19, Sail Shaping 2, Laguna
1jun19, Capsize Lessons, QT Skiff
15jun19, Rend Lake 2019, Mixer
1jul19, Scarfing Lumber, Vireo14
Table of Contents
