Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(1May04) This issue will repeat the all important bulkhead bevels essay. The 15May issue will show how to set up a rowing boat.
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 15TH MIDWEST HOMEBUILT BOAT MESSABOUT will take place at Rend Lake in Southern Illinois on the weekend of June 12 and 13. 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.
Richard Evans' new Power QT takes to the water.
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.
RIVER RUNNER, FLOAT BOAT, 15-1/2' X 45" X 100 POUNDS
This was a custom project for a man who wanted a Lowe Paddlejon boat but found they were quite rare, essentially a custom order. The idea of a boat like this is to float mild rivers with a guide in the stern directing with a paddle and a passenger or two up front fishing. You might recall the design I did last year called Ozarkian which is very similar, maybe the father or grandfather of the Lowe design. (I suspect southern Missouri is sort of jonboat heaven, the source of most of them both in spirit and in material. I recall driving the interstate down to Springfield, Mo. about ten years ago and near Lebanon, Mo I passed what seemed to be miles of aluminum jonboats and pontoon boats stored in fields along the highway. Even little children there must know how to weld aluminum.)
He sent me some photos of a paddlejon he had seen recently and a sales brochure. I tried to copy the lines, thinking all the time that these boats are a lot more subtle than you might think. At the time I had no real Lowe around to study but the brochure left me with the impression that the paddlejon was perhaps a regular small power jon made long and double ended with swept up lines both fore and aft to allow easier paddling. But it is not quite a true double ender in that the stern transom is raked for the usual 15 degree motor mount. As far as power goes, a boat like this won't plane nicely at all, trying to stand on its stern at the least excuse, so I say 3 hp max and as I recall the Lowe boat was limited to maybe 5hp.
Getting back to the lines, I had the feeling that these are made from a constant width piece of aluminum, say 32" wide on the bottom and 16" wide for each side for a total panel width of about 64". Stiffening wales are already pressed into the panel. The flat wide panels are folded with a brake such that the proper flare of the sides is established. The end chines are notched and the end bottoms drawn up and the end sides are drawn in to close the notches which are then welded shut. But the chines for the main portion of the hull are not welded at all, just bent. There seems to be another trick in that the top of the sides bends inward a lot sooner than does the bottom of the sides, resulting in a rolling flare that gives the boat a somewhat elegant shape (I think). So you might think a manufactured jonboat is a dumb and brutish thing, but I'm quite certain most of them are actually pretty clever.
Anyway, River Runner is a plywood version needing five sheets of 1/4" plywood. The idea of the light ply is to keep the boat light enough to manhandle into a truck or onto a car roof but it will take a diligent builder to keep it light. I suspect the aluminum original would be no heavier. Simple nail and glue construction.
River Runner plans are $15 when ordered direct by mail from me until a prototype 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 Texas Ladybug is getting details (Toto in background):
Out West the Picara picks up where it left off before the winter:
The Deep South Skat is getting its brightwork:
Another Picara, this one with a 1' stretch in the middle, going together in Arkansas. Sailmaking done and its on to glassing the hull.
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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