wrote:
derbyrm wrote:

Some points made in the Yachting Monthly article:

1) using identical hulls (catamarans) and identical total sail area, they
raced the Bermuda rig head-to-head with each of the other rigs. The course
was laid out to provide all points of sail and was in sheltered water. The
crews were each attempting to get the best from their rigs, but were
cooperative rather than competitive. (No tacking to cover. Lots of room at
the mark.)

2) each rig had a small jib added to provide "slot effect" (except the
lateen)

3) the sprit and gaff rigs utilized vangs to prevent the twist that does
penalize performance

4) the triangle plan form is notoriously less efficient than the rectangle

I think the Bermuda is much over-rated. To say that it goes to windward
better is contrary to the tests described in the article and reinforces the
idea that efficiency means "wins races" rather than "gets where we want to
go best for the least cost and effort." The polar plots were quite
dramatically different and I speak neither Polish nor Finnish. Note that
the typical Bermuda racing rig involves Genoas with a large overlap, not
because this provides the best knots/square foot of sail, but because it is
"free" area under the rules.

Of course simpler rigs don't provide a market for all of the very pricey
"go-fast" gadgets. http://www.apsltd.com/Tree/d90000/e87451.asp (my
candidate for a "little shop of horrors")

Roger

http://home.insightbb.com/~derbyrm

"William R. Watt" wrote in message
...

"derbyrm" ) writes:

By coincidence, I just finished re-reading the Yachting Monthly article
on
"The Fastest Rig" (July 1984). According to their tests using identical
hulls and rigs with identical sail area, the sprit rig was the fastest on
all points of sail. To windward, it was 30% faster than the
Bermudian/Marconi. Only the lateen was poorer than the Bermuda rig which
survives (dominates) because of the racing rules. (And the lateen was as
good in light airs.)

Wind tunnel tests in the UK showed the lateen rig to be the least
efficient. It's efficiency depends a lot on the angle of the top spar.
Almost verticle is best. The tests showed the crab claw to be the most
powerful sail (actually works like a kite not an aerofoil) but it's
difficlut to manage in narrow waters and shifting winds. The bermuda sloop
rig (high aspect marconi version) was the most efficient overall due to
better sailing to windward. IFRC the sprit and gunter were about the same.
The experiments were done by a famous Poish Finn (an oxymoron?) sailor who
has gone on to study sails but I can't remember his name just now. He has
written research papers and popular books on sails.

One thing that greatly affects a sail's efficiency is the leading edge. A
mast sleeve helps because it minimizes turbulance at the leading edge.

A lot of times sails were chosen for other reasons, eg ease of handling
or cost.

BTW it's called "marconi" after early radio antenna towers built by the
inventor Marconi. The high aspect bermuda rigs had to be stayed like his
radio towers.


Can you describe the Sprit Rig, and can you effectively use a small jib
with it? We will start building in Jan, I like the simplicity and
appearance of the cedar strip, but actually like fiddling around while
sailing.
I like Rogers attitude about the rig, but wouldn't mind making a
change if it would mean a little better performance.


A lower effort of heeling centre would be one reason to use any low
rig in a canoe or kayak.

I wonder if a marconi mast could do better if tried with a more
square sail, with the top cut off of a main too large for the
backstay, a longer boom, and a batten spar car hoisted a little
below the tack of the sail. Attacked to the sail's peak and
trimmed close to car, it could affect the curvature of the sail at
it's top. The backstay could be disconnected and seized to the mast
base, freeing the leach of what could be a schooner sized sail. With
a vang at the bottom and a spar at the top, it may well be a
superior rig to the marconi sail, inside a backstay. Some boats will
balance well this way, especially if they have a history of too much
weather helm.

The sail itself will take the strain of the absent backstay, and a
jib flown low on a cutter stay could be accommodated. The spar might
cause the mast to curve one way or another, depending on how high
the sail is carried. When high, a foot or two above the spreaders,
it would fatten the sail, and when low and reefed at the foot, a
foot or two below the spreaders, would flatten it. A topping lift
attached to the sail tack would beef up the backstay function for
scaredy cats who might feel better with a backstay substitute. Two
could be made self adjusting if fed back to the boom as vangs and
preventers capable of ensuring the main never touches the lower
shrouds. They would be set and forget.

If this rig was found suitable in all conditions except racing, the
mast could then be shortened. You might find yourself passing boats
with smaller ior rating penalties.

If I had a big old tall main to butcher, I might try it.

The batten spar, or two smaller wishbone style battens for balanced
tacking sail shape, would hang between the sail peak and the car in
the sail track. It could be trimmed from the cockpit, even in line
with the halyard.

It would contribute to weight aloft, which might be balanced by
shortening the mast and even downsizing or eliminating the spreaders.

A longer boom could be accommodated with the marconi backstay
disconnected.