Garth Battista drifts his Mayfly14 around last year.
Contents:
Contact info:
Jim Michalak
118 E Randall,
Lebanon, IL 62254Send $1 for info on 20 boats.
Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(1mar02) This issue will will finish the series about assembling an "instant" boat. The 15mar02 issue will discuss cutting bevels.
ON LINE CATALOG OF MY PLANS...
... 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 prices there are $6 more than ordering directly from me by mail in order to pay Duckworks and credit charges. The on line catalog has more plans offered, about 65, than what I can put in my paper catalog and the descriptions can be more complete and can have color photos.
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Left:
Garth Battista drifts his Mayfly14 around last year.
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Making A Hull 4
THE SAILING BITS...
If you are making a sailing boat you have a bit of work left. It's interesting to note that professionals claim to spend about half of the labor hours in putting a finish to the boat. But if I've found the labor and often the cost of a sailing rig is also about half the total cost of the project.
THE MAST STEP...
Mast steps vary but on smaller designs I prefer to use the solid chunk method. Well, almost. The mast shouldn't bear directly against the bottom of the hull, especially if the boat has no stiffeners along the bottom centerline. Why? Because the mast of a sailboat is almost always in compression, pushing down at the step and sometimes with a very large force. Also masts often rotate during sailing. So here is how I prefer to do the job:
What you see here is that the step is laminated in two pieces. The bottom bearing piece is usually 3/4" thick and the top piece is 1-1/2" thick. The top piece has the hole for the mast heel. You can cut it out with a band saw or saber saw usually. Same with the thinner bottom piece. The bottom piece should have, I think, a small slot to drain away any water that pools in the mast hole of the top piece. Cutting that drain slot is very easily done before the piece is attached to the top piece. Glue and nail the bottom piece to the top piece.
Now to install the step. Usually it fits into the intersection of the bottom and a bulkhead. Those two elements almost always meet at an angle. The step should fit right into that angle. Measure the angle on you hull and trim the front face of the step to match it. Fasten the step very well into the hull with lots of glue and stout nails or screws into both the bulkhead and the bottom.
THE MAST PARTNER...
Mast partners vary even more than mast steps! Some are just planks bolted across the boat's wales with a hole through for the mast. Some are thick plywood plates bolted and glued to the fore deck. Most of mine are lumber pieces bolted to a bulkhead like this:
Almost all are 1-1/2" thick lumber. Sometimes the partner lumber has to be pretty wide to accept the mast hole or slot, but also to space the mast the proper distance from the bulkhead. That might seem trivial but it is quite important. The proper dimension here will ensure the proper rake to the mast, and that puts the sail in the right position fore and aft, and that gets the handling of the boat just right. So the rake of the mast is one of the sacred things about your boat plans. (On the other hand, if your boat doesn't handle right, you can tinker with the mast rake to try to fix that. Rake the mast more aft and you should increase your weather helm. Rake it forward will decrease weather helm.)
Usually a mast partner like this is made in two pieces because that is easier. The hole for the mast becomes a slot that can be cut with a saber saw instead of needing a large hole saw. All that is easy enough. The real problem is bolting it to the bulkhead because the bolts need to be long, usually longer than the common drill. Here is how I do it. Once the step is made I drill the holes for the bolts through the step while it is on the work bench. Then I put the step in position on the bulkhead and spot the holes on the bulkhead with the drill. Remove the step and complete drilling the bulkhead holes. Long bolts are required and I don't know if there is much harm in making the bolt holes 1/16" or so oversized so that precise fitting isn't required. Long bolts are required and tighten the nuts well so that there is lots of friction between partner and bulkhead. In my opinion, this mast partner assembly is no place for wood screws - use through bolts.
THE SPARS...
The mast is pretty straight forward. I would always laminate my mast from several pieces of wood. If the design calls out for a 2-1/4" diameter mast I would use three laminations of 3/4" wood. For a 3" diameter mast I would use two 1-1/2" laminations. The practice of laminating will give you a mast that is much less likely to warp. With common lumber laminating also tends to spread out knots and flaws such that you won't get a big bad spot that goes clear through the mast.
Same with the yard and boom. If the design calls for a 1-1/2" square piece, then one laminated from two 3/4" pieces should be superior, although I must admit that using a single piece would be usually an acceptable temptation. On smaller boats, say less than 70 square feet of sail, I have used hand rail moldings, round and about 1-1/2" in diameter, as yards, and closet poles, round and about 1" in diameter, as yards. Don't use PVC pipe no matter how tempting. PVC is heavy and flexible compared to wood and really a poor choice. Aluminum tube makes very light and stiff spars. But I think wood is best for several reasons. One is that is it is traditional. Two is that it is cheap. Three is that it is quiet (compared to aluminum). Four is most important and that is that wood is bouyant! A small boat with a lug rig made of wood will not want to turn turtle when capsized because the yard and mast will act as outrigger floats when they hit the water.
You might try hollow masts and spars. I've made a few and in larger sizes hollow can be easier because you can work with 3/4" thick lumber with a normal saw. If you were to make your mast solid from say 3" thick lumber you will need a band saw or some special arrangement to trim it to shape since a normal circular saw won't cut that thick. On the other hand, in smaller spars you really won't save a whole lot of weight by making the spar hollow and I don't think heroic efforts will pay off here.
THE LEEBOARD...
The leeboard - always best to laminate it from thinner plywood to avoid warpage. So if the leeboard is to finish at 3/4" thick you should make it from two layers of 3/8" plywood or three layers of 1/4" plywood. What I like to do is to make one lamination exactly the right size and the others a bit oversized. Then apply lots of glue between the layers, place the layers on top of each other on a flat surface and tap light nails through the stack so that the layers can't slide around on each other. Then place something like concrete blocks on the stack of layers to appy pressure. Then walk away until the glue has set hard.
Trim the glued up leeboard blank to final shape. Then streamline the front and aft edges that will flow through the water. Don't just round the edges with a router bit. It doesn't have to be carved to a full airfoil shape but I would suggest something like this:
Here is how I do it. Clamp the trimmed blank to the workbench. Start the shaping on one edge with the coarsest rasp you can buy. As you carve through laminations you will find a nice line forms at each glue joint. Use these as indicators to keep your shaping true down the length of the edge. You will actually find it is fairly easy to do. When you get it roughly where you want it, smooth it all down with a belt sander. I don't own a power hand plane but would try it if I had one. I haven't found normal hand planes or drawknives to be very useful in shaping plywood - the rasp is my favorite tool here. Another useful tool might be a small disk sander with very coarse (20 grit!) paper in a drill.
As mentioned earlier about rudders, if your leeboard vibrates in use, streamline it some more.
My plans will show the position of the leeboard pivot hole but it might be prudent to hold off drilling it right now. Wait until the rest of the hull assembly is done so you can double check the proper operation of the leeboard.
THE LEEBOARD GUARDS...
This is the only tricky thing about leeboards but I think it is still a lot simpler than any centerboard or daggerboard case.
Here is the situation. The leeboard will be attached to one side of the hull, always at or very near to the widest beam of the hull. The leeboard pivots on a bolt that attaches to the lower leeboard guard. It will always be mounted such that it is parallel with the centerline of the boat. Usually it will be mounted vertically when the hull is lever, but not always - sometimes the leeboard is mounted parallel to the flared side of a hull. Is that bad? Most likely you would never notice the effect of the non-vertical leeboard.
So the first step in installing the leeboard is to locate the leeboard pivot point on the hull. The sail rig drawing will show where the pivot is supposed to be, both up from the bottom, and fore and aft on the hull. Level up you hull and mark where the pivot point should be. Then mark where the lower leeboard guard should fall on the hull. Like this:
Now to make a piece of wood to fit there. Usually on a smaller boat the lower leeboard guard is made from a piece of 1-1/2" thick lumber. Start with a piece that is a lot wider than the final width. We will trim off the outer face to be parallel with the hull centerline later. The biggest challenge will be to cut the inside face of the guard so that it will fit tightly to the side and yet account for the flare of the hull's side and mount perpendicular to the leeboard.
Here is how I have done that. First I place the oversized lumber guard piece right above its final location, right against the wale and scribe the shape of the side there right onto the guard piece. So I'm using the wale shape in that area as a guide to the guard shape. Then I set a saw (a bandsaw works fine but so will a saber saw with a good blade) at an angle equal to the flare of the side. Then I saw to the scribed line at that angle. It should fit! Screw it into position temporarily.
Next we need to locate the outer face of the lower guard such that the leeboard will be parallel to the hull centerline and be vertical. The leeboard will bear on the wale. Place a level on the wale right at the leeboard pivot location like this:
Now place a long straight edge on the guard piece such that it its edge falls on the mark determined above and parallel to the hull centerline, like this:
Mark that line. That is where the outer face of the guard needs to be for the proper leeboard placement. Remove the leeboard and cut the face on that line. Trim the leeboard to its final shape. Drill the pivot hole. Glue and screw the lower leebord guard into position.
Now you can try mounting the leeboard to see if the pivot hole location is right.
Now to make the upper leeboard guard. Usually the best way to make this guard is to laminate it from several layers of thinner plywood. The upper guard will be glued and bolted to the wale. If the wale has a lot of sheer (curvature when viewed from the side) then the upper guard is sometimes best laminated clamped right on the wale so that it will start its life curved in the same way as the wale. As with the lower guard, start with a blank that is well oversized.
Once the blank for the upper guard has been glued up, place it on the wale and scribe the inner edge to fit against the hull. Trim that edge to shape and clamp the blank into position. Almost always on my designs the upper leeboard guard is attached to the underside of the wale. Locate the slot for the leeboard and mark the final shape of the guard. Remove it and cut it to shape.
When you cut the slot, make it a bit too wide. You don't want the leeboard to get stuck in the slot, and remember that the wooden parts will swell when wet.
Trial fit it with clamps, perhaps with the leeboard and its pivot bolt in place to check the workings. When you are satisfied, drill bolt holes to mount it while it is still clamped in place. Remove the clamps and apply lots of thick glue to the wale joint and bolt it in place. Take no chances with the strength of this joint.
THAT'S IT. Paint it and you are done!
NEXT TIME...
We'll show how I cut bevels.
Contents
Jewelbox Junior
SAILBOAT, 15' X 5', 400 POUNDS EMPTY
JEWELBOX JUNIOR
This is Jewelbox Junior, a 15' version of the original 19' Jewelbox built a while back by Karl James in Texas. That Jewelbox went all over the US and parts of Canada and I understand was sold a few years ago to someone in Florida and replaced by a larger sharpie that Karl had designed. Here is a photo of the original Jewelbox.
JB Jr is also narrower than the original boat, the bottom now planked with just two sheets of 1/2" plywood. Perhaps a good comparison of the two boats would be that Jewelbox needs 16 sheets of plywood and JB Jr needs 9. In particular I hope that JB Jr could be towed behind a small car. Two protoypes of JB Jr were completed last fall. One by Vern Stevens in Idaho and the other by Erwin Roux in Pennsylvania. Vern had a chance to take this photo before winter hit:
And Erwin sent quite a few great photos taken on a beautiful autumn day.
Here you see that JB Jr has that Birdwatcher cabin. The idea behind the Birdwatcher cabin, invented by Phil Bolger in his Birdwatcher design, is that the crew sits low inside the cabin looking out through watertight windows.
The crew weight thus acts like ballast. The boat becomes more stable with extra crew where a normal raised deck boat becomes less stable. I did some paper studies of the self-righting abilities of Junior. With it lighter bottom planking, Junior is bound to be less in that department than Jewelbox, which Karl says has righted from having its windows submerged. By my studies Junior should self right from up to 65 degrees of roll. Beyond that and she would roll another 15 degrees and become stable on her side. She won't flood due to her Birdwatcher cabin. If you couldn't rock the boat back upright you would have to exit, right the boat from the water by stepping on the leeboard, and climb back in. And you would need a reliable step to do that in any high sided boat. These are just paper studies. I would expect my IMB design to behave the same way. Larger heavier designs, like Jewelbox and Scram, should self-right from a full knockdown. More weight on the bottom, especially another layer of plywood there, would be a good investment if you could tow the extra weight.
I've shown Junior with a sharpie sprit rig, although you could substitute a lug sail as Stevens did.
JB Jr plans are $35. Simple nail and glue construction with no jigs or lofting.
Prototype News
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.
Here are the prototypes abuilding that I know of:
Electron: The California Electron is coming along. Right now a four cycle 2 hp outboard has been purchased so the original electric idea may wait a while.
Mayfly: The prototype of the original 14' Mayfly is finished in New York state. Here it is on its first sail (Long Island Sound).
A Campjon is ready for paint in exotic Queensland, Australia. Another is underway in New York with an enlarged cuddy.
AN INDEX OF PAST ISSUES
Herb builds AF3 (archived copy)
Hullforms Download (archived copy)
Plyboats Demo Download (archived copy)
Brokeboats (archived copy)