Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(15DEC98) This issue will continue a discussion of rowing. Next issue (about 1Jan99) will continue the topic.
I SHOULD HAVE TOLD YOU LONG AGO....If you like my type of boats and boating you must know about the paper magazine MESSING ABOUT IN BOATS. There are at least two web sites that lift articles from MAIB but you really need to get a subscription and see it all. The magazine comes out every two weeks and is for the great part written by its readers, like me. The magazine is essentially the work of one man, Bob Hicks, at 29 Burley St, Wenham, Ma, 01984-1943. Twenty four issues a year for only $24! You can't go wrong.
PETE AND KARL JAMES WAY OUT WEST
GEAR TO INCREASE POWER
(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 begun to 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.
We'll make some oars and a seat/ditty box for a conventional rowboat.
LIGHT ROWBOAT, 15' X 4', 70 POUNDS EMPTY
Someday I may get to put my full catalog on the net. For now I'll put one design in each issue.
This is a pretty new design. John Bell was the first to send a photo and report of a completed boat. Here is his initial report:
As I said in an earlier e-mail, I finally tested my Sportdory for the first time last week. It's still not quite finished yet, but it is close enough. At the moment she's not at what you'd call a high level of sparkle, outside is glass cloth and epoxy and inside is epoxy only. I'll be filling, sanding and painting over the winter to get her up to somewhere between "workboat" and "yacht" standards. Probably more towards "workboat" end of the spectrum, though!
I built this boat for two reasons. One, I wanted to do a taped seam boat just to see what that process is like (easy and fast, a little messy!). Two, I needed a way to get some exercise. I have so little free time now between family and career, that exercise needs to be simple and enjoyable. I enjoy nothing more than being on the water, and rowing and paddling are the simplest ways to meet all my objectives. Having a cartoppable boat helps, too. Sportdory fills this need very well.
She is built out of ordinary lumberyard BC yellow pine plywood (~$16 sheet) and a mixture of Douglas fir and spf for the dimensional bits. Lumber expense was minimal, obviously. I do have about $125 worth of glass and epoxy on her, plus about $135 in oars and hardware. I'll still need to buy some paint, but that will be a minimal expense. I'm not ready to use latex yet, but will instead use an oil-based exterior enamel. She'll be primed with "Kilz" which I already have on hand so won't count as an expense.
For the skeg, your plans say something to effect of "size it to keep you straight, modify after testing." It is drawn as a wedge maybe 3" deep and two feet long. I built mine about 4" deep and two feet long. Instead being feathered to a point on the front end as is with a wedge, mine is about 1" at the forward end, and bottom edge is set parallel (more or less) to the waterline. It is only attached temporarily since I was not sure if it was sized correctly. The boat might be an eensy bit faster if the skeg were smaller, but I'm not planning on changing it at the moment. Right now the boat goes straight with without my having to concentrate much. Maneuverability was never a goal of mine anyway.
How does she handle? She feels fast, that is she moves easily and quickly without too much pressure on the oars. At speed she makes very little wake so I suppose speed is limited more by skin friction than wave making. She's does not have a very smooth bottom at the moment (a lot of filling of the fiberglass weave is still needed), so it will be interesting to see if she goes better when finished. The trim fore and aft was perfect (for me anyway at 200#) with the designed rowing position. I haven't installed the second set of oar sockets, so she hasn't been tested with a passenger yet.
With a 24" beam on the bottom, she is tiddly but not alarmingly so. The water is a little cool to do any real stability testing. She does seem to stiffen a significantly as she heels. My rowing seat is about 2-3" too tall. Lowering it may make novices feel more confident.
There was a little breeze blowing on Saturday and I noted no effect on the handling of the boat. I'd like to get it into some more wind and waves to see how she takes it. Soon...
Cartopping is fairly easy, and it rides well without hurting the view out of the windshield. This is a far cry from a highly rockered white water canoe I used to own which looked like a 15' banana. You couldn't hardly see the road with that thing loaded up! Without a center thwart loading it single-handedly is tricky but doable. I'm going to build a clamp-on rowing and portaging thwart to make dry-land handling easier. She's a little heavy at about 80#. BC Pine ply and fiberglass sheathing are the main culprits there. You were right about the weight while on the water though -- you don't notice it.
Thanks for a great little boat! Hopefully we can be together somewhere where you can try her out and form your own opinion. Midwest Messabout in May perhaps?
Kennesaw, GA USA
770-592-2165 (h) -----------------------------------."
One might wonder about a comparison of Sportdory, Roar2 and QT. They are all about the same size and weight, a size and weight I've found ideal for the normal guy. They are small enough to be manhandled solo yet large enough to float two adults if needed. They are all light and well shaped for solo cartopping. Roar2 is probably the most involved to build and I would think the best all around of the three. Sportdory is simpler and lighter, probably at least as fast and as seaworthy, but most likely will feel a little more tippy and less secure (although it probably is as seaworthy). You shouldn't really try standing up in either of these two. QT will be the least able of the three as far as speed and seaworthy but may be the easiest and cheapest of the three and is stable enough to stand up in. So take your pick.
Here are the words about Sportdory in my catalog:
"Sportdory is an attempt to improve upon the Bolger/Payson dory I built about 15 years ago. This boat is slightly smaller than my old dory. In particular the bow is lower in hopes of cutting windage. the stern is mostly similar. The center cross section is about identical. This boat has slightly more rocker than the original Bolger dory.
The hull is quite simple and light, taped seam from three sheets of 1/4" plywood, totally open with no frames. The wales are doubled 3/4" x 1-1/2" pieces to avoid the wale flexing my first boat had. I've added an aft brace to stiffen it up and give the passenger a back rest.
Mine once covered 16 statue miles in four hours. In rough water you will feel the waves are about to come on board but they won't. But if you try to stand up in one it will throw you out with no prayer of reentry.
Sportdory plans are $20. The prototype was built by John Bell of Kennesaw, Georgia.
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. (If you order a catalog from an internet page you might state that in your letter so I can get an idea of how effective this medium is.) 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.
Usually when a design from the Catalog of Prototypes starts getting built and is close to launch I pull it from the catalog and replace it with another prototype. So that boat often goes into limbo until the builder finishes and sends a test report and a photo.
Here are the prototypes abuilding that I know of:
IMB: Click here to visit Tim Webber's page and see some photos of the Texas IMB under construction. Then poke around Tim's web page a bit. I heard this week from the Texas IMB builder who said, "I want to let you know that IMB is alive and looking good. She is now right side up and sitting on her cradle. Soon this boat and carrier will be mounted on the small trailer I have ready......"
Fatcat2: There is an old timer (80 years +) in Minnesota who has completed the hull of a Fatcat2. Fatcat2 is a simple 15' x 6' catboat, gaff rigged and multichined. I think the sail rig will be done this coming winter. Not only has he finished the Fatcat2 hull but he has started a....
Twister. The Twister hull is pretty well cut and fitted, ready to tape. Walt lives north of Green Bay, working in an unheated shed. He tells me there will be no more building until things warm up again next year in late Spring. If you live up there and would like to contact Walt, let me know.
Jonsboat: A builder in Florida has started a stretched version of Jonsboat (16' stretched to 19'). This boat was featured in the 15 April issue.
BACK ISSUES LISTED BY DATE
Mother of All Boat Links
Messing About In Boats
The Boatbuilding Community
Kilburn's Sturdee Dory
Bruce Builds Roar
Herb builds AF3 (archived copy)
JB Builds Sportdory
Hullforms Download (archived copy)
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