If you want an historically accurate batwing rig, here are the ---

Spar Diameters

--- otherwise read the Notes below.

Sail Area
in sq ft

-A-
Boom & Yard
Diameter

-B-
Lower Batten
Diameter

-C-
Upper Batten
Diameter

36 & 47

Luff:

3/4"

Mid:

7/8"

Leech:

1/2"

3/4" or t f j

3/4"

1/2"

3/4"

3/4"

1/2"

70

Luff:

3/4"

Mid:

1-1/8"

Leech:

1/2"

3/4" or tfj

7/8"

1/2"

same as 36

87

Luff:

7/8"

Mid:

1-1/4"

Leech:

3/4"

7/8" or tfj

7/8"

3/4"

3/4"

7/8"

5/8"

103

Luff:

7/8"

Mid:

1-3/8"

Leech:

3/4"

same as 87 same as 87

Extra Reefing Batten (Dotted)

87 & 103 --

Luff:

3/4"

Mid:

7/8"

Leech:

1/2"

--

Dimension (D), Mast Diameter, is the same for all rigs:
2" at heel and 1-3/8" at head. If you use mast tubing on your boat, cut the heel to fit its inside diameter as appropriate. 1/8" more or less won't matter. A rectangular or square 'box' to fit mast heel is also OK.

t f j: "to fit jaws" or other mast fitting. See (not available yet).
Otherwise, work from the spar's "mid" dimension.

Notes:

If you're a revisionist, square- or rectangular-section spars are OK. Round over the edges. On a rig this small any extra wind resistance won't matter.
- White Cedar "baluster" and Western Red Cedar "pickets" are commonly available from home centers in 8- or 10-foot lengths. They are nominally 2x2, which measures out to just over 1-5/8" square. The corners are already rounded for you.
- Otherwise, use fir 2x4 cut to size (fir 2x4s are lightweight) or laminate spars from other stock.
- Bamboo of the proper diameter is ideal for the Yard and the Upper Batten because of its light weight. Actually, all spars can be bamboo and your rig will be historically accurate for someone's batwing from the 1880s.
If you make a rectangular mast from trimmed 2x3 or 2x4, mount it with the wide dimension running across the boat - athwartships.
If you have trouble keeping the boom out when running before the wind in light air, the best remedy is to rake the mast forward just a little bit. It can be permanently raked, or adjustable with a couple of chocking blocks.
About Ferrules:
The luff end of the boom and yard (to go into mast fittings).
The tip of the mast.
The luff end of the extra Reefing Batten in the largest two sails (mast fitting).
The original spars had protective metal ferrules.

About Rigging

COD 5/13/97