Jim Michalak's Boat Designs

1024 Merrill St, Lebanon, IL 62254


A page of boat designs and essays.

(1 June 2017) This issue will start a series about rowing. The 15 June issue should feature the 2017 Rend Lake messabout.

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.

MESSABOUT NOTICE:

THE REND LAKE MESSABOUT WILL TAKE PLACE ON JUNE 9 and 10 AT THE RINGNECK LOOP OF THE NORTH SANDUSKY CAMP GROUND AT REND LAKE IN SOUTHERN ILLINOIS. USUALLY THE SANDUSKY CAMP GROUNDS MIGHT BE FULL FOR THAT WEEKEND. BUT SOME OF OUR BOATERS HAVE RESERVED SOME OF THE SITES THERE SO YOU (AND I) MIGHT PASS THAT WAY FIRST SINCE SEVERAL TENTERS CAN SHARE A CAMPSITE. IF NOT, THEN I WOULD TRY THE WAYNE FITZGERRELL STATE CAMPGROUND WHICH IS ON THE MAIN CAUSEWAY LEADING TO SANDUSKY. THEIR WEBSITE SAYS IT IS STRICTLY FIRST COME FIRST SERVE, NO RESERVATIONS ALLOWED. IT IS A VERY QUICK DRIVE FROM THERE TO SANDUSKY. HOPE TO SEE YOU THERE!

Left:

Jake Peters' new Toto gets a test flight up in Minnisota.


Contents:

 

Contact info:

jim@jimsboats.com

Jim Michalak
1024 Merrill St,
Lebanon, IL 62254

Send $1 for info on 20 boats.

 

 

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.

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Mayfly14

MAYFLY14, ROW/SAIL SKIFF, 14' X 4', 150 POUNDS EMPTY

Mayfly14 is a straight forward flat bottomed plywood skiff for sailing and rowing. She's easy to build because her planks have no twists. That means that the chine log and wale bevels are constant for all practical purposes and can be presawn before assembly. The construction is of the simplest nail and glue variety with no building jigs or lofting required - an "instant" boat. The prototype was built by Garth Battista and kids in Halcottsville, NY.

I think this boat is about the right size for a lot of folks, although I might argue that it is too heavy to cartop with comfort and once you decide to trailer a boat you might as well go to a sixteen footer. Mayfly14 will take two adults easily and yet still be a wonderful solo boat.

The sail rig is a balanced lug which is easy to build and stow. I recommend that my customers sew their own sails either from common polytarp (as Garth did in the boat shown above) or real Dacron sailcloth. The plans show instructions for sewing in real sailcloth. You need a sewing machine that sews zigzag stitches and cheap home machines are usually good at that. I don't claim to be the world's best sailmaker but it is not majic. I can do it and so can you. The clothes you are wearing are ten times more complex than a small sail. There are a few rules to follow and I give an essay on that with each set of sailboat plans. In fact I suggest you sew your sails before you build your hull. Both sail and hull require about the same work space. Sew the sail first, roll it up, stuff it in a closet, and now your workspace is ready for your hull. Getting the sail done can get you over a big mental hurdle.

Garth's friend Ari made this Mayfly14 shown in shallow water at Long Island Sound:

Here is another by Don and Tom Burton in Illinois:

And another by John Dominique in Louisiana...

Mayfly14 needs three sheets of 1/4" plywood and two sheets of 1/2" plywood.

Mayfly14 plans are $30. But, the Mayfly14 plans are shown complete in reduced size in my book available from Duckworksmagazine.com along with Garth's blow-by-blow assembly photos plus a huge amount of other stuff.

Contents


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:

The first Jukebox3 is on the (cold) water. The mast is a bit too short - always make your mast too long. A bit more testing will be nice...

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.

Contents


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

15jun16, Rend Lake 2016, Mixer

1jul16, Ballast Calculations 1, Dorado

15jul16, Ballast Calculations 2, Robbsboat

1aug16, Ballast Calculations 3, AF4

15aug16, Taped Seams, Cormorant

1sep16, Butt Joints, Vireo

15sep16, Old Outboards, Philsboat

1oct16, D'Arcy Ballast, Larsboat

15oct16, D'Arcy Ballast 2, Jonsboat

1nov16, D'Arcy Ballast 3, Piccup Pram

1dec16, Sail Area Math, Ladybug

15dec16, D'Arcy Thoughts, Sportdory

1jan17, AF3 Capsize, Normsboat

15jan17, The Weather, Robote

1feb17, Aspect Ratio, Jewelbox Jr

15feb17, Aspect Ratio 2, IMB

1mar17, Normsboat Capsize, AF4Breve

15mar17, Underwater Board Shape, Harmonica

1apr17, Capsize Lesson, RiverRunner

15apr17, Measuring Leeway, Mayfly16

1may17, Scarfing Lumber, Blobster

15may17, Rigging Lugsails, QT Skiff

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SOME LINKS

Mother of All Boat Links

Cheap Pages

Duckworks Magazine

The Boatbuilding Community

Kilburn's Power Skiff

Bruce Builds Roar

Dave Carnell

Rich builds AF2

JB Builds AF4

JB Builds Sportdory

Hullform Download

Puddle Duck Website

Brian builds Roar2

Herb builds AF3

Herb builds RB42

Barry Builds Toto



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