Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(15jul07) This issue will look a bit into the shape of hulls. The 1 August issue will rerun the all important "sail area math" essay.
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.
Bob Bean goes for a spin in his new Jonsboat.
REMEMBER THIS PHOTO???
This is Bob Williams' modified for sailing Shanteuse. Note that the stern has been swept upward on the bottom to match the sweep in the bow. But Shanteuse was designed to be a pure powerboat and thus had a straight wide stern, as shown here in the first prototype by Douglas Snelson:
So what's the diff??
PHIL BOLGER'S ADVISE ON POWERBOATS....
... is that a hull designed with a straight wide stern will run OK at slow speeds and OK at high speeds. A hull designed only for slow speed operation will be better than the power hull at slow speeds and hopeless at high speeds. Essentially it will not run at high speeds hardly at all due to control problems even if it has enough power to push it through. The high speed hull on the other hand will be at a speed disadvantage, with no control problems, at slow speeds but it can kick up its heels and fly at high speeds. So if you are thinking in terms of moving faster than a fast walking pace you almost have to go with the deep wide stern of the modern powerboat.
Why bother with the slow speed shape at all? Because craft like rowing, paddling and most sailing boats are working with very small amounts of power, say 1/10 th horsepower. They will never plane and need all the low speed advantage they can get.
Anyway, Bolger is almost always right. Let's look into the Shanteuse shape changes with Hullform to scope this out.
I made up a model of the original deep sterned Shanteuse with Hullform. Here is a tilted view:
I ran the speed/drag feature up to 8 knots and got this for the deep transom standard Shanteuse:
I'm not sure if the little hump just short of 5 knots is for real. When testing my AF4 I never could measure such small waves in the curve. Beyond 5 knots the drag increases an awful lot. I don't show drag beyond the "hump" but it falls to about 150 pounds and then starts its own steady climb.
It might be worth while to figure the power needed to clear that power hump. It is about at 6.5 knots which is about 650 ft/min. And drag then is about 280 pounds. That makes for 650 x 280 = 182000 pounds times ft/min. One horsepower is 33000 pounds times ft/min so this is 182000/33000=5.5 hp. But that is real hp pushing the prop forward and our AF4 tests showed again and again that only about 35% of your rated hp is pushing the boat, the rest is lost mostly in prop inefficiencies. So I would expect a Shanteuse at 1200# total weight to need at least 15 hp to clear the hump. It's a big boat and that is no surprise.
I modeled the Shanteuse as a shallow sterned boat with the bottom sweeping above the waterline exactly as it does at the bow. Here is the model:
And here is the drag curve for that boat at 1200# total weight:
I see no real difference - if anything the deep sterned boat has less drag! Confused? So am I. I would pass it off as bad theory but these Hullform things have proven to be correct to a certain extent almost all the time. It might be because of the shorter waterline of the swept up stern. And in this boat the "deep" powerboat transom is not really that deep. I guess Bolger warned us about this.
NEXT TIME: We'll refresh our sail area math.
SHANTEUSE, SHANTYBOAT, 16' X 6', 700 POUNDS EMPTY
Shanteuse is a slight enlargment of the mini shanty Harmonica. Shanteuse is 1' wider than Harmonica and has a 3' extension on the stern to allow a small back porch and a motor mount that is totally out of the living area.
Above is a Shanteuse built in Florida by Vince SantaMaria a couple of years back but he stretched his to 24' so I couldn't really call that one a Shanteuse. But here is one by Douglas Snelson in Tennessee that looks to be right to the plans so I will call this one the prototype. He sent a bunch of photos:
I've also made Shanteuse a little heftier. I'm thinking this one will weigh about 700 pounds empty where Harmonica comes in at around 400 pounds. I'm not sure if the extra beef is needed because Harmonica seemed totally adequate to me as far as strenght and stiffness go. But the extra size of Shanteuse is probably going to take it out of the compact car tow class. The plywood bill for Shanteuse looks like six sheets of 1/2" plywood and eight sheets of 1/4" plywood. I would not use fancy materials on a boat like this and am reminded of Phil Bolger's warning to never spend a lot of money building a design that was intended to look cheap. I see pine exterior plywood at my local lumberyard selling for $11 or a 3/8" sheet and this entire boat could be built of it. So the plywood bill would be less than $200 and I'm thinking the entire bill less than $500. The pine plywood looks quite good to me, its main drawback being that it doesn't lay very flat.
These boats can be very comfortable to camp in. The interior volume and shape are not unlike the typical pickup camper or the volume in a full sized van. It's not huge, it's cozy. The top has an open slot 28" wide from front to back on centerline. You can close it over with a simple tarp, leave it open in good weather, or rig up a full headroom tarp that covers the entire boat. I've shown lots of windows but the window treatment can be anything you like. You do need to see out. I would be tempted to cover the openings with screen and use clear vynal covers in the rain or cold. For hard windows I think the best material might be the Lucite storm window replacements sold at the lumberyard. Easily worked, strong, and not expensive.
As for operation, these are smooth water boats. So it is best to stay on small waters that never get too rough. On bigger waters you need to watch the weather very carefully. For power I would stick to 5 or 10 hp but I'm very much a chicken about these things. To plane a boat like this, remember the good old rule of a horse for each 50 pounds. So if you are running at 1000 pounds total you will need at least 20hp to do the job and then at full throttle. So I think you would want at least 30 hp to plane at 2/3 throttle. And this boat could easily be loaded to over 1000 pounds.
Update, 2007. Bob Williams brought a sailing version of Shanteuse to the 2007 Rend Lake meet. He worked the sail rig out totally on his own, they are not on the plans. He also swept the stern bottom up to improve low speed performance. Here are a few photos of his boat:
Plans for Shanteuse are $35.
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 I heard about through the grapevine.
HOLY COW! A Jukebox2 takes shape in Minnesota. Unheated shop means no work during the winter. Check out that building rig!
And the Vole in New York is Garth Batista's of www.breakawaybooks.com, printer of my book and Max's book and many other fine sports books. Boat is done, awaits water. Beautiful job!
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The Boatbuilding Community
Kilburn's Power Skiff
Bruce Builds Roar
Rich builds AF2
JB Builds AF4
JB Builds Sportdory
Hullforms Download (archived copy)
Plyboats Demo Download (archived copy)
Brokeboats (archived copy)
Brian builds Roar2 (archived copy)
Herb builds AF3 (archived copy)
Herb builds RB42 (archived copy)
Barry Builds Toto
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