Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(1May05) This issue will rerun the bulkhead bevel essay. The 15may issue will continue the drawing Bobsboat essays.
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.
THE 16TH MIDWEST HOMEBUILT BOAT MESSABOUT will take place at Rend Lake in Southern Illinois on the weekend of June 11 and 12. Remember that lots of folks come on Friday and leave early Sunday. Take I-57 to exit 77W and then follow the signs to the Gun Creek Recreation Area. Camping at this Corps of Engineers facility is $10/night and that includes the ramp fee. There is no schedule of events except a pot luck dinner in the campground on Saturday evening - we wing it. This year some of us have reserved the campsites on the water of the two middle camping loops so look for us there if we aren't at the boat ramp.
Ari and co. in his Mayfly14 on a nice day on Long Island Sound, aground on the sand.
I don't know if there are many topics that cause more confusion to boatbuilders than bevels at bulkheads and transoms. Some slant in and some slant out. Sometimes you can measure them right off the lines drawing but often you can't. To a certain extent the subject has become less important with taped seam construction, but many glue and nail boats are still being built and as you will see, I like to use nail and glue construction in the very early stages of building a taped seam boat because it allows a quick and solid alignment when that is most appreciated, as shown in this photo of Dale Dagger in Nicaragua with a Toto project. At this stage the hull has used conventional construction which required cutting bevels on some of the elements. Dale asked for clarification on one of them.
I did update the Toto drawing to include the full sized bevel drawings shown below. One is for the side edges of bulkhead 10 and the other is for the side edges of the transom.
When I figure out the dimensions of the plywood piece that forms the shape of the bulkhead or transom, I take its dimensions off my lines drawing as if the piece had no thickness.
But the real panels do have thickness. So I rig it such that one face of the panel lies on the plane where I took the panel dimensions and mark that face "Dimensions to Here". Now if the side or bottom panels are sweeping in or out from the dimensioned face, then the other face of the bulkhead or transom will need to be smaller or larger than the dimensioned face.
Let's take the case where the adjacent panels are sweeping outward from the dimensioned face. We'll call this one an "outy". The transom bevel on Toto is as outy. The dimensioned face of the Toto transom is on the plane of the end of the boat and the transom's forward face needs to be slightly larger than the dimensioned face to allow for the outward sweep of the side panels, which measures 10 degrees at that point. How much larger? The Toto transom is supposed to be 1/4" plywood with a 3/4" thick framing stick, for a total of 1" thick. So to allow for the 10 degree bevel each side needs to have 1" X tan10 = .176" extra material which is 3/16" to most of us. But when I build one of these outy's myself, I pay no attention to that extra thickness. See the figure below to see how I do it on my own boats.
I've found the best tool to cut straight bevels is a table saw. First I cut the side sticks on the table saw to the correct bevel. Then I cut the transom (or bulkhead) panel out of plywood to the dimensions with no bevel, just a square cut. Then I glue and nail the beveled sticks to the plywood piece such that a straight edge along the beveled stick will just kiss the "Dimensions to Here" edge. That's it. I haven't fussed with that "extra material needed" measurement at all. This gives a nice straight edge to the right dimensions and it doesn't really get involved with thicknesses - if you use thicker or thinner wood than specified it will still fit.
"But," you say,"there's a little triangular area on the edge of the plywood that isn't right." True. I fill that with glue when the panel is glued and nailed to the side. That triangle isn't very big. On this 10 degree bevel it would max at .045". No problem. To me the glue there is really a hope of sealing the grain on the edge of the plywood, not a strength issue since a lot of that ply edge will be end grain anyway and about useless for glue strenght.
Now let's talk about the inny. Bulkhead 10 on Toto is an inny. (I suspect the trouble Dale had was that he made this one an outy the first try.) The basic dimensions of bulkhead 10 were taken 10' aft of the bow tip of the boat. That is the actual front face of the bulkhead, the face marked "Dimensions to Here". At that point the sides are sweepin inward 7 degrees as they go aft. This bulkhead is also 1/4" plywood with 3/4" sticks for a total of 1" thick. So the aft face of the bulkhead needs to be 1 X tan7=.12" smaller on each side edge than the front side edges.
Innys are a little easier to picture. You could make all the edges square to the basic dimensions and then run them through a saw set to the proper bevel to shave off the extra material. I used to do them that way and still do on occasion. The problem I have is that I use a bandsaw for this which doesn't care to cut straight. And a large bulkhead is a beast to run through the saw all at once. You could try a saber saw or circular saw set to the proper bevel if you think you are good enough at it to keep the blade just kissing the edge marked "Dimensions to Here". I' not.
So I've gone to making the inny bulkhead the same way as I make an outy. First I prebevel the framing sticks with a table saw. Then I cut the plywood panel to shape with no bevel, just a square cut. Then I glue and nail the sticks to the sides of the panel. If the bevel is severe I do try to line up the face of the bevel stick with the "Dimensions to Here" edge of the plywood. Then I will have a small triangle of plywood protruding from the beveled face. I can trim that off later. In the case of a small bevel, I don't do that. I just line up the stick with the back edge of the panel. When I assemble it to the sides there will be a little triangle to fill with glue again. And the panel will be slightly wider than what the lines call for. In the case of Toto's bulkhead 10 the error would be .25" X tan7 = .03". Nothing to worry about.
NEXT TIME: We set up a new rowing boat.
SOW'S EAR, CUDDY POWERBOAT, 15,5' X 6', 600 POUNDS EMPTY
Sow's Ear is somewhere between a shantyboat like my Shanteuse and a cuddy power skiff like AF4. It has a lot more room in the cabin than does AF4 but a lot less than Shanteuse. And it has an open cockpit that will seat two or three adults in comfort unlike Shanteuse. Sow's Ear should be a bit more seaworthy than Shanteuse but keep in mind that no light and small flat bottomed boat is going to be seaworthy to any real degree. And it looks a bit more like a boat than does Shanteuse. As for looks, it follows closely on the heels of Bolger's Micro where the looks are the result of high volume and ease of building. Sow's ear will be a lot easier to build than Micro because powerboats have a lot fewer parts than do sailboats (assuming you are not going to build your own motor).
And using a powerboat is a lot easier than using a sailboat, assuming you have a motor that is reliable. I think the irony of most modern sailboats is that no one will use one without a reliable motor, so they are really motor sailers. There is no question that a good motor makes the whole sailing operation in boats too large to manhandle a lot easier while you still have the option of smooth and quiet sailing. The cost involved is that the sail rig of any boat usually doubles the labor and materials needed and the setup time at the waterfront of the trailer sailer is often an hour instead of five minutes. So you see the advantages of a straight powerboat. I tried hard to make this one very easy to use, especially for a typical family. It will float in about 3" of water so launching and beaching is a breeze. The bow has a step through transom and you will need to step up 20" to get aboard and into the cabin, easy enough for a child or anyone with both hands full of gear. The main cabin room is 6.5' long and 6' wide and will sleep two adults. Atop the cabin is a slot top full length which you can cover with simple fabric. Behind that room is a storage/utiltiy area where you can store all of your gear and clothes, cook and keep a portable toilet. Aft of that is the cockpit, 5' long and 6' wide, large enough for lounging in a beach chair or keeping a short stack of those plastic lawn chairs. The sides are deep and secure for children. And in the stern is a full width self draining motor well. To steer the boat you will need to sit on a tall chair or stand to see over the cabin. Remote motor controls will be best but a long tiller extension to the motor will work well too. That is what I use with my AF4.
The Coast Guard would advise no more than 25 hp on Sow's Ear, based on length, width, and the fact that it has a hard chine. It would take that much power to plane the boat at 2/3 throttle with some adults aboard, weight being all important. But this boat won't do well in big open waters that can get rough. It will do very well with say 5 hp in protected smaller waters where planing and distance covered are not important.
Construction is simple nail and glue. Sow's Ear needs seven sheets of 1/4" plywood and four sheets of 1/2" plywood. That is more than the longer AF4 but this boat has a lot more interior volume.
I think one Sowsear was finished a few years ago but I never got photos or a test report so I still list it as a prototype. Here is a photo of a model started by David Arnold (I think):
Sow's Ear plans are $25 until one is built and tested.
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 AF4G is done and launched. Writeup after testing:
Garth has the big Cormorant to the point where his kids have taken it over and he can't get it back.
The out West Picara has its roof and some major sail rig bits done:
The down South Picara is getting its innards done.
This long and lean project is a 19' version of Toon2. I don't have the drawings done yet. The builder is working from preliminary drawings and is about to pass me up. MDO plywood looks like cardboard now but it isn't.
We have an experienced builder building a Mayfly16:
This is a slightly modified Veep14. I'm told the sheer is raised a bit and the stern given a bit of flare but the bottom is per the plans. Waiting for a test:
And here is the beginning of a Vector. The builder is keeping a website of the project at http://email@example.com/
And a Polepunt is nearing completion in Poland, of course:
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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