Sunday, January 9, 2011

Building The Matinicus Double Ender- Part 6

The lug yawl sail plan is finalized .

Its hard to believe that almost a year has passed since the last post. Once spring comes around, there is so much work to do at the club in preparation for the sailing season, and then the season itself (which this year continued on until nearly Thanksgiving). Six months go by without any progress on the peapod! And so I look forward to the holidays as a time to re-connect with boat building.I had always intended to rig this boat as a lug yawl, and finally got around to drawing up the sail plan. I also decided to substitute a dagger board for the pivoting centerboard. The dagger board is lighter, simpler, and takes up less space than a centerboard, and when rowing, a plug can be dropped in the slot to eliminate speed robbing turbulence in the trunk. This conversion is not as simple as it might seem, as any changes to rig or underbody can affect the balance of the boat, producing a heavier than normal weather helm, or a possibly dangerous lee helm. The thwart layout and rowing positions determine, to some extent, the position of the dagger trunk, as thwart and trunk are mutually supportive structurally. Once the balance point of the hull is arrived at (by balancing a scaled cutout of the underbody on an awl and marking the point), the rig is drawn and its geometric center is found. I played around with mast placement, rake, sail shape, etc. and made many back and forth adjustments with the sails and the dagger board until I arrived at what I hope will be a well balanced boat.

So its on to the interior! I built the dagger trunk first, and made it a good four inches longer fore and aft than the board itself, still hedging my bets as regards the balance until the sailing trials. I'll fill in the excess slot once I determine the exact position of the board. The trunk is so simple! Just two posts, which extend through the plank keel, two sides, and two bed logs cut to the slight curve of the inside bottom.
The completed trunk, upside down. The posts will extend through the keel.
Slot pattern for a long top-bearing router bit.
 I made a router jig to cut the slot from inside the boat, and I left the ends of the slot plumb even though the posts are raked to avoid chiseling the angles through 1-1/2" of keel. A wedge will be epoxied in (one from inside, one from outside) to close up the gap. Very simple.

A wedge will be epoxied in to fill the gap.

I blue-taped the parts of the slot that must remain clean, and then glued and clamped the trunk into the boat, being careful to keep it plumb athwartship.

The area of the slot to remain clean is masked off.

The trunk is clamped to the boat through the slot.

The frames are next, and I chose to use a futtock style frame of spanish cedar, glued up in halves with short pieces to optimize grain direction. I settled on 5 frames, built to span sheer to sheer and set perpendicular to the centerline like a bulkhead, and joggled to fit the laps.

The first layer of the spanish cedar frame-halves.

Layer two spans the previous butt-joints.
 I'll confess right up front that the bevels eluded me. It would have been much simpler to set the frames square to the planking, but I wanted a continuous frame, dory style, and so paid the price. My method of finding the frame shapes is quite simple, and avoids spiling. I cut a scrap of thin (1/8") ply close to the inside shape, but ignoring the laps. I then hot-glued a few small blocks in the hull, and tack welded the rough pattern to the blocks with more hot glue.

A thin ply pattern is hot-glued to small blocks exactly in the frames intended location.
 I next ripped up strips of the same thin ply, cut them to length, and hot-glued them to the pattern board at each plank. This is very fast, and extremely accurate. As long as the pattern is set exactly where you want the frame to land, then the frame will fit every time.

Straight-edged strips fit snugly to the planks.

The shape is traced onto the glued-up frame blank, and sawn out.
 I use the same pattern for both sides of the hull, but I do try it out on the other side and make notes of any slight discrepancies. Now for those tricky bevels. I cut the frames square, tight on one edge, but leaving a gap at the other.

The frame fits tight on one edge, bust is open in way of the bevels.
 I ripped up a pile of variously beveled strips on the bandsaw, and used this stock to add the bevels to the frame, rather than cutting the bevels away. I release-taped the hull under each frame half, and glued these bevels to the frame halves right in the boat.

Beveled wedges are glued in.
 When the glue cured, I removed the frames and cleaned everything up, before installing the frames permanently in the boat. The end result is structurally identical to a sawn bevel, even if the method is somewhat unorthodox. I will admit to being a trifle sheepish about it, but I'm quite satisfied with the end result. The frame halves are connected together across the bottom with a final piece, then the inside curve is sawn to shape and beveled in one piece before installing in the boat. Don't forget to cut the limbers!!

Before the frames are glued in, the hull is taped off for easy clean up.
The frame spans are too large to adequately support a 3/8" thick floor board, so I fitted short floors (timbers) between each frame. I went ahead and made patterns for all the floorboards while I was at it. The floors were glued in just like the frames.

Floor board patterns were made at the same time as the timbers.
A finished floor timber, ready to install (note the limbers).
Floor timbers are glued into the boat. This completes the framing!
I installed the sheer clamps (inwales) after the frames, notching the frame heads before they went in the boat.

The inwales (sheer clamps) are scarfed to length.
 I scarfed up a plank of spanish cedar to length, ripped out the pair, and fitted them to the boat. I did this by myself, and it is a bit tricky with epoxy all over a 16 foot long noodle which gets surprisingly stiff and contrary when forced into a deep compound bend. But it worked out well. The notched frame heads really help hold the timber in place.

Inwales are clamped to the sheer. It takes a lot of clamps!
 There are no breasthooks in this boat. She will be half decked, with an oval coaming. I like to fit a longitudinal beam (like a deck king plank) let into the deck beams and going all the way to the stems, taking the place of a breasthook, and strengthening the centerline. This longitudinal beam can also double as a mast partner like on my crab skiff Cricket.

Different boat! This shows the deck framing I like to use on Cricket.
We'll end here for now. I'm working on the final deck and furniture plan now, and fitting the seat risers. By next time, the interior should be shaping up well. Stay tuned...