2SD

A 12' (3.6 m) two sheet dory

Having done the 3SD I just had to try the 2SD, too ;-)

In this case the plywood utilization turns out to be 90.1 %. Just sawdust and narrow splinters are left over.

At 12 ft (3.6 m) overall length the 2SD may be quite a strange dory. It is definitely too small to be safe for any real work. And it is quite big for a beach toy.
But it just had to be drawn ;-)

Now compared with the 1884 Portsmouth U.S. Navy shipyard dory presented by John Gardner in his "Dory Book" 2SD does have a strong sheer :-)

• The green lines are those of the 2SD profile.
• The blue lines are those of the 2SD profile scaled up to match the overall length of the 1884 Navy dory (18' 10").
• The red lines are those of the 1884 U.S. Navy dory.

But so what? With those sky scraping bow and stern the 2SD definitely makes a difference ;-)

Cutting the plywood

The pieces for the 2SD are cut out of two sheets of plywood like this.

• The green pieces present the right, starboard side of the boat, the inner face up. Piece number 1 is the bow piece, number 2 is the middle piece, and number 3 is the stern.
• The red pieces present the left, port side of the boat.
• The yellow pieces make the bottom.
• And the transom is laminated out of the four grey pieces. Two layers, two bits per layer.

Note: The sides are assembled "one side of the plywood out, one side in". In case Your plywood has one good and one bad side, You can have the inside of the boat all good, or the outside of the boat all good, depending on Your taste. I'd probably have the good side in, because that's the side I'd be looking at most of the time. The fish may look at the bad side.

The side pieces and the bottom pieces have to be joined using glass fiber tape butt seams.

Measurements for the left boat side, inner side up. This would correspond to the red pieces of the above picture, the pieces connected. The plywood seam lines are indicated with blue vertical lines on the drawing.

Measurements for the boat bottom.

Measurements for the transom.

Measurements for frames.

The angle of the stem is 81 degrees at the sheer, tapering to 59 degrees at the bottom.

Resistance curves at 120 kg / 250 lbs total displacement

Rt (violet curve) = total resistance
Rv (red curve) = viscous resistance (friction)
Rw (blue curve) = wave forming resistance
Rh (pale blue curve) = resistance created by transom stern
Full speed scale = 4.0 m/s = 14.4 km/h = 9.0 mph = 7.8 knots

Building sequence

The building sequence is roughly like this:

• Cut the sides, bottom and transom out of plywood.
• Cut a stem out of suitable wood.
• Do the butts or scraphs, and laminate the transom.
• Mark the frame position lines A, B and C on the inside of the sides and bottom.
• Connect the sides to the stem at the bow.
• Build the frames A, B ja C out of plank.
• Glue and screw the middle frame B between the sides in such a way, that the line B on both boat sides coincides with the middle of the frame.
• Connect the stern ends of the sides to the transom.
• Insert frames A and C between the sides.

At this point do not attach frames A and C permanently. This is just a temporary arrangement to measure the angle of the sides at the frames to make a good fit.
Position the frames A and C in such a way, that the front frame A is just behind the line A (red in the drawing), rear frame C is just ahead of line C (red in the drawing).

• Measure the distance between the frame and the side (blue arrows).
• Transfer the measurement over to the other side of the frame (green arows).
• Remove frames A and C.
• Cut off the marked (orange) part of the frames.

Attach the chamfered frames permanently.
The front frame A in front of line A (red), the rear frame C behind line C (red).

• Attach the bottom.
• Attach risers inside the frames, for seats to rest on.
• Attach seats and oarlocks.
• Paint her.
• Use her.

Suggested seating arrangements

The 2SD is primarily suitable for just one person. The location for the rowing seat is just in front of the middle frame B.

Two more seats can be installed, at frames A and C. There's probably no sense in this, but You will do so anyway, so what can I do ;-?

A suitable oar length for both suggested oarlock positions would be in the range 7' 11" (2.4 m) to 8' 4" (2.5 m) for the middle seat. And in the range 7' 5" (2.2 m) to 7' 10" (2.4 m) for the front seat. It is to be expected, however, that rowing from the front seat is going to be somewhat cumbersome, due to the side height at the seat position.