Milling tapered cove&bead strips

[JimConlin]

Now & then you hear of people building a large strip planked boat and tapering the strips, most or all of 'em. I can see merit in that idea. Most boats are fatter in the middle.
I'm contemplating a fat little boat to be built in strip composite with roughly 1/4" thick strips. For the well-discussed reasons, I like the cove&bead approach in such boats, but my jig for milling strips doesn't tolerate much variation in width.
Anybody got any ideas about a jig that'll tolerate as much as 1/2" variation in the width of 1/4" strips?
There's a prize for the best idea.

Jim

[ 11-05-2004, 09:57 PM: Message edited by: JimConlin ]

[maa. melee]

Featherboards, at least 2, 90 degrees apart. one to hold the strip against the table and one to hold the strip against the fence. the featherboard holding the work against the fence should have a pivot so as to self-adjust to the tapers. a small strip of 1/2 inch or 1/4inch plywood sprung against this featherboard would provide the perfect amount of constant pressure. viola.

[ 11-05-2004, 10:17 PM: Message edited by: maa. melee ]

[MJC]

I made a jig for the router table that uses springs over sliding pins to push a 3/4" thick board with a 1/4" rabbet to hold the strips both down and flush to the cutter head. The springs are about 6" each side of the cutter head. There's a half circle cut out where the cutter head is for chip ejection. To keep this unit from lifting up, I had to "cap" it with another board fixed to the stationary board thru which the pins slide. I waxed everything with a silicone wax I had lying around.

The springs don't have to be real strong. I don't know how to describe the springs I have on the unit now. You want to be careful not to crush the cove. If I was building another such unit, I'd think about using a machine screw for the pin with a nut/washer to produce adjustable tension on the spring.

From my experiments with tapered "cheater" strips, I know that this entire unit adjusts smoothly to changing widths.

Sometimes starting the strips requires a third hand to hold the spring loaded unit open until the strip is moving thru the unit.

[Paul Scheuer]

What's your cutting method, Jim.

In model making, cutting the final tapered planking shape with a small plane, I've found it easier to fix the plane and feed the work past it, rather than trying to clamp the board. Actually, drawing the plank toward me worked better, as I seem to have more control.

The router ideas above are good. You might try a precision fence, with the outfeed part shaped to compliment your cut shape.

[Bill Perkins]

Jim , how are you going to cut the taper in the planks ? There's a method I read of in a Fine Woodworking publication that might work for you .It requires a big stationary planer , which I don't have unfortunately .

To plane the taper in the plank stock before the 1/4 in. strips are ripped from it ,the stock would be sent through the planer on a concave bed . The power of the springs on the planers rollers , and the rollers range of vertical travel ,determine how much taper you can work in .The rollers mash the board down into the concavity, you flip the piece over after each pass, and a smooth taper results .When I finally own a shop space I'm going to look for some big old iron , with this operation in mind .

I've experimented with my 10 1/2 in. portable planer (sigh ). I start with the stock centered in the machine and crank down till the blade just touches the wood and the board starts to move through. I keep cranking down very slowly as the wood passes through the machine .Multiple passes toward both ends of the stock produces a smooth job .

When I next strip plank a hull I want to try tapered strips too .It seems to me the wider stock this allows will be quicker to plank and better looking .The typical 3/4 in. wide plank is a little too busy visually for my taste when finished clear , although I like the strippers .

[ 11-06-2004, 11:12 AM: Message edited by: Bill Perkins ]

[imported_Steven Bauer]

Robb White had an article in 'Messing About In Boats' describing how to make two little planes, one convex, the other concave. He claims they are much faster to use than a router based system. Each strip really just needs a few swipes of the plane near the ends. Anyone else remember reading about this?

Steven

[JimConlin]

OK.
Here's the notion as far as it's developed.
I'll start with boat length planks of white cedar thicknessed to about 1". Then, I'll plane the ends gradually down to maybe 5/8". This diminishing thickness will be gauged to the girth of the boat. Then i'll slice off 1/4" strips. Because of the taper in the thickness of the planks, these will be tapered.

My current strip milling jig is clamped to the router table and has two pairs of springy guides which press the strip against the fence and against the table. The guides are made from tongue depressors and are screwed to arms which are attached to the fence. They accommodate the small variation of the non-tapered strips i've milled in the past. The whole business is self-contained and is quick to store and set up.

I'm just thinking that to accommodate nearly 1/2" of taper will probably need a new approach to holding the strip against the fence. Maybe something articulated with springs. The mechanism should be permanently attached to the fence.

Any ideas?

[ 11-07-2004, 12:21 AM: Message edited by: JimConlin ]