Jim Michalak's Boat Designs

118 E Randall, Lebanon, IL 62254

A page of boat designs and essays.

(15September 2014) This issue will be about rowing. The 1 October issue will talk about guessing at hull weight while designing.



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....


...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.


...will take place at Lake Eufala on October 9 - 13. I plan to be there on the 10th and 11th and give a talk about Design Your Own Boat. There is a lot going on and you can read about it at SAIL OKLAHOMA .


...Check the website https://sites.google.com/site/lakemonroemidwestmessabout/home for maps, directions, and general messabout information. Feel free to email or telephone (812-378-4236) if you have any questions. Tell your small boat friends to join us on Lake Monroe, September 19, 20, and 21 for a great time just messing about in boats. See you soon, John & Susan McDaniel


The Josh Withe kids take his new Larsboat for a spin. Note the use of the aft storage tank as a rumble seat.



Contact info:


Jim Michalak
118 E Randall,
Lebanon, IL 62254

Send $1 for info on 20 boats.





(Before we get too involved in this I should mention that I have never tried any of the following techniques myself. This is just a paper study for me. If you think I've really blown the analysis, let me know with details and I'll rewrite with corrections.)

Increasing power will improve speed. Remember the formula for power is an arrangement of force, time and distance.

One way to increase power is to work out at the gym a lot and increase your muscle size such that you can pull with more force. Then slide the oars out a bit such that the extra force you can develop is converted into extra hull speed.

Another way to increase power is to quicken your stroke, pulling with the same force through the same distance. The increased oar handle speed is instantly converted to increased blade speed. You'd be rowing with lots of short quick strokes. This method works well with short boats that don't carry well between strokes.

You could also lengthen the stroke, keeping the force and stroke frequency the same. With any boat, especially a fixed seat boat with short oars, there are limits on the stroke length. If the oars start sweeping through large angles, efficiency will be lost.

Figure 1 shows the usual sliding seat arrangement. Here the rower sits on a seat that slides on rails, his feet are strapped into shoes which are fastened to the hull. In position A, the start of the stroke, the oarsman has his arms extended and his knees drawn up such that his hands are near his ankles. By extending his legs on the power stroke at the same time as he pulls on the oars, the rower greatly increases the length of his stroke compared to a fixed seat. The seat looks to be sliding about 2' during the stroke. In the diagram he has about 4-1/2' of oar handle stroke, about a 50% increase over a fixed seat. If the cadence of the stroke is the same as for a fixed seat, a 50% increase in horsepower would result. (He might also pull with a lot more force on the handles, but remember all the force he generates will transfer through his arms and hands. So I wouldn't expect a large increase in handle force in a long run.)

All the forces produced on the rower's hands are reacted through his feet alone and the human body is well built for that. None of the force reacts through butt friction.

Here are some arguments against the sliding seat.

For one thing the sliding of the seat may require a long space. (But the boat should be long anyway to take advantage of the extra power.)

The sliding seat can be a hazard in rough conditions. That may be a double hazard because you must strap your feet to the boat for the system to work.

The length of the oars must usually be increased because if you double the length of the stroke you will double the sweep of the blade. The angles the oar will sweep through will become excessive and inefficient if the oar is not lengthened. The lengthening of the oars will usually mean the addition of outriggers to help place the oar handles conveniently.

All these things may be worth the bother if you are the right person in the right boat. But maybe not. As shown in the figure I dreamed up for Roar2, a 50% increase of the power will increase boat speed about 15% . Instead of going 4 knots at full stretch with a fixed seat you might make 4-1/2 or 5 knots with a sliding seat. Normally I advise against it for a shorter boat. A longer narrow boat will probably be needed to take advantage of the sliding seat.

And increasing the speed potential of the boat will do no good if you don't pack the extra horsepower needed to push it to the higher speed. The rowing rig is just a transmission to match your power output to the needs of the boat.

There is another set up - the sliding rigger. In this boat the rower is seated on a fixed seat. The riggers that hold the oarlocks are not secured to the hull but instead are fastened to a sliding car which also contains the foot brace. The rower's feet are tied to the brace as with the sliding seat. But now his feet push the rowlocks aft as he pulls the handles forward. The overall power effect is the same as for the standard sliding seat. But the details are a bit different. For one thing the rower's weight doesn't shift around causing trim changes and hobby horsing. And all the force on the rower's hands reacts through his butt again. I've never seen one of these rigs in action. I read somewhere that when first tried in racing shells decades ago the sliding rigger boats easily beat conventional sliding seat boats and were soon written out of the rule books. Maybe so.

Figure 3 shows the system Ron Rantilla developed. Ron started with a standard canoe in which you paddle facing forward, (an advantage of paddling as opposed to rowing). To avoid having to transfer the paddle from side to side for directional control (an advantage of rowing and double paddling over single paddling) he mounted two paddles on a pillar in the center of the boat. The paddles attached to the pillar with a springy thingy that carried a lot of the paddle weight while allowing flexibility to paddle. Thus he was able to work each paddle with each hand. Ron lengthened the paddles into oars and thus he was able to row facing forward, (his "oars" were pivoted in the center of the boat in this case, not at any oarlocks, and his hands were outside the pivot). Forward facing push rowing has been used for a long time in certain areas and seems to be an inefficient way of using the human anatomy. Even fancy articulated oars that allow you to pull row while facing forward have never achieved the efficiency of regular pull rowing. But Ron's system does allow forward facing pull rowing without the mechanical losses of an articulated system. Then Ron found he could run lines from foot pedals though pulleys to the oar looms and get his leg power into the equation. Then he found, that by attaching the leg lines just right and adjusting the center pillar springy thingy just right, he could make the oars dip just the proper amount under power and feather the proper amount on retrieval. No hands required in the proper conditions!!

I haven't seen Ron's system in action but there are certainly several advantages. None of the stroke power need be transmitted through the arms and hands - they can just be used to guide the oars if needed. You face forward. You sit in one position. You're feet aren't strapped to the boat.

Clearly there is some complexity of gear involved, but it's all pretty reliable and understandable and efficient. I guess the reaction forces on your body go out through the butt again. I would think a conventional sliding seat boat could boast more "power" because the rowers arm and back movements can add to the length of the stroke.

Ron wrote about his invention and experiences in MESSING ABOUT IN BOATS several times. He's not a racer but has raced the system with some success against sliding seat ocean racers. Like the sliding rigger experience, some of the conventional sliding seat racing organizations won't let him compete.



Philsboat is essentially an IMB with the nose extended to a pointy bow. The width and multichine configuration are the same as IMB's. The cabin is 3" deeper because Phil is at least 3" taller than most of us. In a boat with a Birdwatcher cabin like this one added depth to the cabin makes it safer in that the righting forces in a knockdown are greater. That would be true of any boat if the center of gravity did not move with the cabin roof but with the normal cruiser adding depth to the cabin also means raising the crew deck up so the folks can see over the raised cabin. And that means the CG is elevated too, and then all bets are off concerning self righting. But with a boat like Philsboat eveyone rides down low inside looking out through the windows.

Here is a photo of Bob Williams' IMB:

In addition to the pointy bow and added headroom I added what I hope is a serious motor mount. Probably 3hp will drive it as fast as it will ever go and that at part throttle. But the motor well gets to looking pretty large even for such a small motor. For one thing it must be deep to put a short shaft motor on a deep stern like this so I ran it straight down to the boat's bottom. Working on the motor down it its well will be about impossible and you might need to keep an eye on your knuckles when you pull the starting rope. And the well must be surprisingly wide to allow the motor to swivel in steering although the usual case here will be to keep the motor locked straight ahead and steer with the tiller. The wide well pushed the rudder off center and you need a crooked tiller or rudder linkage to make it all work. I opted for a simple but crooked tiller.

I also added low seats like those I saw added to the two IMB's that came to the Lake Conroe Messabout. Pretty much the same as what I have in Scram Pram where the seats do double duty as water ballast tanks. Philsboat seats could easily be converted into water ballast tanks also but the IMB capsize tests imply the ballast isn't needed.

The sail rig uses a balanced lug, 113 square feet and the same as that of a Bolger Windsprint.

Philsboat uses taped seam construction. Five sheets of 1/4" plywood, five sheets of 3/8" and three sheets of 1/2" plywood.

Actually the size and material list for Philsboat are about the same as that of Scram Pram. So which boat would be better? Take Philsboat if you are a pointy bow guy. It should be better in really rough water. On the other hand Scram is wider and roomier. It has a flat step through bow that will splash and spit in rough water but makes beaching a very nice experience.

Update, 2007. Chris Feller completed his Philsboat, probably the first prototype completed, and brought it to the 2007 Rend Lake Messabout. Very well made and to plans except he used the 91 sq ft lugsail he had on hand for his AF3, with some mast rake changes he calculated with his "sail area math". Sailed correctly rigtht off the drawing board, so to speak. We had a chance to use it for a few really nice days. In a good sailing breeze, say 10 to 15 knots with occasional whitecaps, our gps bobbed between 5.5 and 6mph for two hours of reaching as we crossed back and forth on the big lake. When I used the Philsboat I thought it was probably just as easy to enter from a beach as the blunt bowed Scram. The front deck is about 2' high so you can sit on it and swing you legs around onto the deck and then into the cabin.

Chris is a big boy but there was plenty of room inside for the two of us and more. Rumor has it that at the campsite the night before Chris slept in the Philsboat on the trailer with an airconditioner in the front hatch plugged into the campsite power. So the boat is plenty big in the way most people would use it.

The stern layout has the motor in a small well to one side and the rudder offset to the other side to give the motor room to swing. There is no linkage to the tiller, the tiller is simply "unstraight" so that is falls on centerline at the skipper's hand. Seems to work well and is quite simple. Chris uses a 2hp Honda which has a fairly large cowling for its size and must be rotated 180 degrees to grab reverse. He said the motor well size is a bit too small for that. Karl James had the same problem with his Jewelbox a long time ago and simply cut away the side of the hull in top of the motor well region - after all it is just there for looks. Chris said he tried the boat under power and found it went 6 mph max, just like under sail. No surprize to me. My Birdwatcher also maxes out at 6mph under 3hp and under 5.5 hp. This sort of hull will only go so fast. Add more power and you just dig a deeper hole and make a bigger wake - you won't go faster. But sometimes more power is nice on a windy day.

(As an update, Chris has brought his Philsboat to several more Rend Lake meets. In 2008 the meet was very windy and Philsboat got a full windows wet knockdown with Chris and Tom Hamernik on board. She self righted with no issues and they kept right on sailing, but Chris confessed he has 100 pounds of lead shot under the seats. Also he is using a 3hp vintage Johnson which he says is quieter and smoother than the Honda.)

You might recall from the Prototypes section recently that there was another Philsboat being built in California. That one last I heard was about to be launched. Has more changes from blueprint than Chris's boat but still is pretty true to form. Seems to be known as Bumble and made by Rex Meach.

And in New Zealand Rob Kellock has been sailing his with a junk rig. He has been knocked down a couple of times and self righted as planned:

Plans for Philsboat are $45.



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.

I think David Hahn's Out West Picara is the winner of the Picara race. Shown here on its first sail except there was no wind. Hopefully more later. (Not sure if a polytarp sail is suitable for a boat this heavy.

Here is a Musicbox2 out West.

This is Ted Arkey's Jukebox2 down in Sydney. Shown with the "ketchooner" rig, featuring his own polytarp sails, that is shown on the plans. Should have a sailing report soon.

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:

And the first D'arcy Bryn is to the point the builder can sit and relax in it and imagine boating. You can follow the builder's progress at http://moffitt1.wordpress.com/ ....






1oct13, Modifying Boats 1, Larsboat

15oct13, Modifying Boats 2, Jonsboat

1nov13, Modifying Boats 3, Piccup Pram

15nov13, Sail Area Math, Caprice

1dec13, Stretched Stability, Ladybug

15dec13, Trailering, Sportdory

1jan14, Cartopping, OliveOyl

15jan14, Width/Stability, HC Skiff

1feb14, Hiking, Shanteuse

15feb14, Dory Stability, IMB

1mar14, Scram Capsize, Scrampram

15mar14, Bulkhead Bevels, Frolic2

1apr14, Capsize Lessons, RiverRunner

15apr14, AF3 Capsize, Sneakerbox

1may14, Paper Capsize, Blobster

15may14, Prismatic Coefficient, Roar2

1Jun14, Roar2 Repair, Piragua

15jun14, Rend Lake 2014, Toto

1jul14, Mast Tabernacles, Musicbox3

15jul14, Sandell Tabernacle, Mikesboat

1aug14, Taped Seams, Cormorant

15aug14, Plywood Butt Joints, Paulsboat

1sep14, Rowing 1, Vireo


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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