Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(1may06) This issue will continue the Raider design. The 15may issue will rerun the important bevel 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.
MESSABOUT NOTICE:THE REND LAKE MESSABOUT WILL TAKE PLACE ON JUNE 9, 10 AND 11 AT THE GUN CREEK RECREATION AREA AT REND LAKE IN SOUTHERN ILLINOIS. MORE DETAILS WILL FOLLOW BUT IT MIGHT BE PRUDENT TO MAKE CAMPING RESERVATIONS AT THE GUN CREEK (CORPS OF ENGINEERS) CAMPGROUND IF YOU INTEND TO ATTEND.
Errol Smith sailing his Trilars Down Under.
Raider Design 4TO RECAP...
We are trying for a row/sail boat that will be used by up to four adults with no baggage. The design is supposed to switch quickly between rowing and sailing and maybe be rowed with the sails up at times. The size of the crew demanded a long boat - 7.3 meters long - to give everyone room to stretch. We are using a V bottomed hull for speed since beaching and shallow water would not be a factor. A sketch of Raider looks like this:
And the Hullforms model looked like this:
Last Raider issue looked at the sail rig design. You may recall it was decided to hang the sail rig on a double bulkhead box. Otherwise the boat is pretty much all open and has to be to allow four oarsmen to operate.
I concentrated next on real hull structure and got this:
I would build the boat of 3/8" plywood (9 or 10 mm) with taped seams. The topsides and decks could be lighter but I found side and bottom panels nested nicely in the plywood panel layout so might as well use 3/8" everywhere. The bottom could be of heavier ply than 3/8" but I am quite certain the builder could never warp the heavier plywood to shape in the bow. In fact while I was making the cardboard model of Raider I found it very difficult to get the card to bend to the shape and changed the bow lines a little bit to get better results. Even then the builder of the real thing is going to have to go slowly with the bottom bow. We won't know for sure until someone tries to build her and even then some of you are better at torturing plywood than others. I recall only two complaints about bending/twisting plywood in my previous designs. When Pete James made Petesboat he found he could twist the 1/2" bow bottom to shape but could get no fasteners to hold it there. So he laminated that area from four layers of 1/4" ply instead of two layers of 1/2". And when Walter Raetz made the first Fatcat2 hull he found he could get the 3/4" bottom to shape only with the use of hydraulic jacks! So best again to laminate from two layers of 3/8" ply.
One thing I have done differently here from my other rowing boats is add a lot of frames. I put a frame under each seat location and normally I never do that and don't recommend it. Here is a photo of Ashley Cook's Vireo which shows the construction I prefer - there is nothing on the bottom from stem to stern:
(Vireo is very similar in shape to Raider but about half its size.) Adding frames takes away adjusting seating positions and that is a very important part of tuning up a rowing boat. But on Raider I felt they are required to stiffen the bottom which will have less curvature (which stiffens a plywood panel a lot) because the boat is so long. And the boat might be heavily loaded regulary. So to avoid flexing of the bottom I added the frames. There are other ways to do that but they also are troublesome. You could put longitudinal strakes on the outside bottom but that might add considerable drag. And you could try those longitudinal stiffening strakes on the inside. But to keep the inside open for the oarsmen we need at least 3 meters of length with no bulkheads. The prototype boat will tell us a lot on this design. Perhaps some of the frames can be eliminated and those seats simply cleated in place. If you are the type who likes to experiment you might build the hull with no frames and try it and see if they are really needed. On a boat that might be built and finished by a professional boat builder that sort of experimentation is probably not possible.
There are some bulkheads of course. The bow tip is closed off with one as is the stern and those two volumes should be watertight to provide emergency buoyancy in a swamping. (Raider has so much open volume that it is hard to say if it could be recovered from a swamping even with thay buoyancy.) And you can see the double bulkheads that form the box upon which we will hang the sailrig. The box separates the bow oarsmen from the rest and I suppose you might punish someone by making them row up there. No way around it, I think.
The positioning of the seats with respect to the oarlocks is to be taken very seriously. It is a bit personal, of course, depending how large or small you might be. I drew all of the seats as low as possible with the idea you could always shim yourself up with a phonebook or something but if the seat is too high there is little you can do about that. On my Roar2 I find the best seat position is about 10 inches below the wale with the aft edge of the seat about 10 inches forward of the locks, but to each his own. I would advise the builder to not install any oarlocks until he can scope the boat out as it floats in the water with its crew.
We'll review making bulkhead bevels.
Dani Jay, Low Power Launch, 20' x 6', 500 POUNDS EMPTY
Dani Jay is the chosen name of the project I called Bobsboat in last year's essays. The idea behind it was to have an easily driven seaworthy launch that would take a bunch of adults around in a laid back style. It was not to be a planing boat so big horsepower and speed were not an issue.
I went with a multichine hull since it is efficient and good in rough water. Big benches on the cockpit sides as I have used in a lot of my designs. They are a full 10' long with a 2' wide walkway between - lots of room. (I have never met a boater who had so many friends that he would fill this boat.) The benches are also 2' wide at maximum and some of you would be able to sleep on them. I would expect the empty hull to weigh about 500 pounds and maybe 700 pounds for the boat with motor and gear. It will take about 2200 pounds to push the boat down so that its chines touch the water so that is about another 1500 pounds of people.
Dani Jay has its motor in a slot in the stern, almost an inboard well. I've drawn such a thing before but that boat was never built. I have stayed away from inboard wells mostly because Phil Bolger, who knows all, hates them so much after having used such boats. Well, I just don't know about that but i do know the Dani Jay man wanted the well very much. It puts the motor right at hand at the back of the cockpit. The well takes up a lot more room than you might expect and Dani Jay is in some respects a 16' boat with a couple of narrow 4' sponsons on her stern. I measured up a few of my own motors and saw the motor slot needs to be a full 2' wide to allow for a full turn and of course nothing can be behind it if you hope to raise it up in the usual way. Phil's argument is that also you have noise, smoke and water surge to deal with. Having the slot open in the stern will keep the water from "pumping up" inside the well. And the motor must be a long shaft to keep waves from surging up into the well and over the "transom' which in this case is an interior bulkhead slanted 15 degrees. I don't think noise will be an issue at all - the only motor to use with something like this is a 5 hp job, 4 stroke if you can afford it. That should push it at full speed at about half throttle. If you use a smaller motor you will be tempted to run it at full bore a lot, and if you use more you will be tempted to overspeed the boat a lot. But a hull like this will not be oversped. It will just dig a deeper hole in the water and make a bigger wake. Last summer I was lucky enough to get a long ride on Paul Effrit's very modified Selway boat which was set up like Dani Jay. As he motored along I lifted the hood and saw there was no evidence of water pumping up or surging inside his well which was also an open slot to the stern. The noise and smoke of his modern 4 stroke was nothing. And full throttle just gave us a huge wake. I am quite confident it will work well if the power is just right. It won't work well if the power is wrong.
Although sailing was not part of the original idea, it was clear that this shape of hull will sail quite well if it were a pure sailing boat. I gave it a simple and cheap and effective balanced lug right with my usual pivoting leeboard. How will the motor well affect sailing? It isn't going to help. You could build it as a sailer only and omit the well. The thing is that if I don't draw the sail rig I will forever be answering requests about sailing it. So there you are - the sail rig.
Taped seam construction from nine sheets of 3/8" plywood and three sheets of 1/2" plywood.
Prototype plans for Dani Jay are $30, until she is built and tested, when ordered directly from me.
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.
The out West Picara is I am told done to the point of using it as a powerboat:
The down South Picara is more or less complete now. Should have an updated photo soon.
This long and lean project is a 19' version of Toon2. Shown here on its first sail in very light winds. We will wait a bit longer to get a sailing report in stronger winds.
A Vector builder is keeping a website of the project at http://email@example.com/ and here is a photo of his boat on its first sail, just before the storm hit. I also have photos of a Vector completed by Pete Mohylsky in Florida. Hopefully a report soon:
Here is a Musicbox2 I heard about through the grapevine.
We have a Philsboat going together in California:
And here is another Philsboat in northern Illinois:
AN INDEX OF PAST ISSUES
BACK ISSUES LISTED BY DATE
Mother of All Boat Links
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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