Jim Michalak's Boat Designs
1024 Merrill St, Lebanon, IL 62254
A page of boat designs and essays.
(15 December 2018) We will look more at electric power. The 1 January issue will review our sail area math.
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.
REND LAKE 2019...
...will take place on June 7 and 8, always on the weekend before Father's Day weekend. I promised to remind all of us to try to get the good campsites on the North Sandusky loop. They are sites 24 through 30 and especially 26 through 29 if possible, this at the North Sandusky campground at Rend Lake. Let's give it a try. This is not really organized but if you nail one down, let me know. I will be trying too. UPDATE: AS OF DEC 6 WE HAVE ALREADY NAILED SITES 26 THROUGH 28. IF YOU DON'T GET A SITE NOW, DON'T FORGET THAT SEVERAL TENTS ARE ALLOWED AT EACH SITE AND YOU CAN DOUBLE OR TRIPLE UP ON A SITE. THERE WILL BE ROOM FOR ALL.
The Captain directs and Gene Berry obeys on his PaddlePlank.
1024 Merrill St,
Lebanon, IL 62254
Send $1 for info on 20 boats.
Electric Boats 2
FIRST A BIT OF REVIEW...
Lead and acid batteries are still the best bet for common electric boats since they are cheaper, more available, and lighter (believe it or not) than other suitable batteries. The battery used to start an auto or boat engine is a poor choice for an electric boat power source since they are designed to give a short big jolt of power, not a long even current like a deep cycle trolling motor battery. Deep cycle batteries are usually rated in "amp-hours" by how many amps of current it can deliver over a 20 hour period. Thus a "100 amp-hour" battery can deliver 5 amps per hour for 20 hours for a total of 100 amp hours. But small trolling motors usually draw about 20 amps per hour (at 12 volts). The higher current draw greatly reduces the total amout of current the battery will deliver. Here is a typical curve for a typical 100 amp-hour battery:
So the 20 amp motor will drain the battery in about 3.2 hours, about 70 amp hours total. Also it is best to not drain a battery below 70% of its total to prevent harming it in a way which will prevent future chargings. So the battery here might be limited to .7 x 3.2 hours = 2.2 hours.
Another recommended limit on the battery operation would be to keep current draw per hour within 20% of the total. So in this case the 20 amp motor is about the max to use with this battery.
Finally, a rough guess at trolling motor horse power is apply the conversion of 1 hp equals 750 watts. A 12 volt motor using 20 amps is using 240 watts, or 240/750 = .32 hp.
In Douglas Little's book ELECTRIC BOATS he presents some power measurements from typical trolling motors. Remember that his "horse power ratings" are based on current measured TO the motor and not the acual measured output of the motor. Here is a chart I made from some of his tests:
Finally, here is a new chart of approximate boat performance, speed vs hp, that is in Little's book. This sort of chart takes no account of "fast" and "slow" hull shapes so is only a very general starting point for figuring performance.
...NEXT, I GOT THIS LETTER...
...after posting the last issue. It was from Clyde Osterhout:
"I know from reading your past articles on the subject that you aren't a really big fan of electric boats. I can't really argue with much that you have said, but my personal experience with the RANGE of electric boats is quite different from your own. For the past 12 years, I have been using several trolling motors with my 17' Grumman Eagle canoe. Most of the time, I have been cruising on mainly flat waters with mild to moderate (1-3 mph) currents. These include the St. Lawrence River, in the 1000 Islands area, the Pocomoke River system in MD, the Susquehanna river, near Three Mile Island, and various lakes and ponds around the Mid-Atlantic region. Maybe 2500 miles or so under power in all. Here are a few observations:
1.With a canoe, at full power, I get about 6-8 miles out of a charge. At 3/4 power, I get about 8-10 miles. I never had enough patience to see how far I could go on anything less. I have discovered that I can go considerably farther with the canoe than the manufacturers estimate I should be able to go. That's because their estimates are based on much heavier boat, with a great deal more resistance to forward motion. I doubt that a converted row boat would be as successful as my canoe. I conclude therefore that an electric boat ought to be narrow, long, and as light as possible. Anything "extra" will reduce range.
2. The motors seem to propel my canoe at about 3.25 mph at the highest setting. That's true of an 18 lbs of thrust motor, as well as a 30 lbs motor. The 30 lbs motor has a great deal more "kick", and works much better in the wind, but the top speed does not seem to be much different. This must be due to the props, as you have already observed. I just obtained an older 30 lbs trolling motor with a small, 3 bladed prop that seems to push my canoe MUCH faster, maybe as much as 5 MPH. I haven't had a chance to do any real testing yet, but it is obvious that prop design is very important for electric powered boats.
3. Electric boats aren't fast. That much is painfully obvious! But the trolling motor powered canoe can maintain a higher average speed than one that is paddled by average paddlers. It works better in windy conditions, and is great for going against a stiff current. It is also quiet, even quieter than paddling. And if one has kids (as I do), it helps to have a free hand or two to deal with them as they squirm around. Finally, many lakes here in PA won't allow anything BUT electric motors, making the choice of what kind of power to use an easy one. So one can find some truly practical reasons for using a motor.
4. DO NOT USE an electric motor in salt water unless it is specifically designed for salt water use. It does ugly things to an electric motor.
What I would love to find would be a "cruising canoe", a long (16-18 foot), narrow (36-40 inches, max), light (less than 120 lbs) boat with a minimal cabin (for changing, napping, or bathroom purposes, not really for camping) kind of thing that would be good for bird watching, swimming, and good clean quiet family fun. Any chance? Hey, a guy can dream, can't he?
Yes, I use 120 amp deep cycle trolling motors. They make a huge difference. Car batteries, as you have pointed out, simply don't work. And not all deep cycle batteries are the same. Sears Die Hards, for instance, consistently put out more "umph" than Walmart batteries of the same amperage. Never could figure out why. They all seem to last about the same length of time, though.
In the end, electric boats aren't about getting anywhere. They are about enjoying the ride itself. Thanks for putting up with my endless observations! Clyde"
LIGHT ROWBOAT, 15' X 4', 70 POUNDS EMPTY
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.
The prototype was built by John Bell of Kennesaw, Georgia. Here is a photo of John's Sportdory under construction. You can see the sides and bottom, precut to shapes shown on the plans, wrapped around temporary forms and "stitched" together with nylon wire ties in this case. I'm quite certain that with this design one must leave the forms in place until all the structural elements like the wales and cross bracing have been permanently installed. If they are removed before then, the assembly will change shape and you won't get the same boat. In particular I think the nose will droop to no one's benefit.
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 the best all around of the three. Sportdory is simpler and lighter, at least as fast and as seaworthy, but most likely will feel a little more tippy and less secure. 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 seaworthiness but may be the easiest and cheapest of the three and is stable enough to stand up in. So take your pick.
Sportdory plans are $20.
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
1jan18, Trailering, Normsboat
15jan18, AF3 Capsize Test, Robote
1feb18, Bulkhead Bevels, Toto
15feb18, Sail Rig Spars, IMB
1mar18, Sail Rig Trim 1, AF4Breve
15mar18, Sail Rig Trim 2, Harmonica
1apr18, Two Totos, River Runner
15apr18, Capsize Lessons, Mayfly16
1may18, Scarfing Lumber, Blobster
15may18, Rigging Sharpie Sprit Sails, Laguna
1jun18, Rigging Lug Sails, QT Skiff
15jun18, RendLake 2018, Mixer
1jul18, Horse Power, Vireo14
15jul18, Motors per the Coast Guard, Vamp
1aug18, Propeller Pitch, Oracle
15aug18, Propeller Slip, Cormorant
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
Mother of All Boat Links
The Boatbuilding Community
Kilburn's Power Skiff
JB Builds AF4
JB Builds Sportdory
Puddle Duck Website
Brian builds Roar2
Herb builds AF3
Herb builds RB42
Barry Builds Toto
Table of Contents