What makes a sail boat overpowered? how much sail is too much per foot of
length? How about wings in the future of sailing?

"The Carrolls" wrote:

What makes a sail boat overpowered? how much sail is too much per foot
of length?

The length is not the most relevant factor.
Sailarea/displacement is better but still not good.
Stability at 15 degrees would be a good illustration of a boats
ability to carry sails, but still not anything near exact.

Another thing that matters is the rig type and shape. A low and long
schooner rig can have more area than a tall slooprig. The aspect ratio of
the rig would be a factor.

Dellenbaugh coefficient or angel takes most of this into consideration and
is a fairly good expression of the boats ability to stand on its legs. It
illustrates the heeling angle at approximately 8 m/s.

In metric The Dellenbaugh angel =

279 x SA x h
---------------
D x GM

279 x (Sailarea (triangular) x Heeling arm) / (Displacement x Metacentric
height)

(In foot, use 57.3 instead of 279)
You can sometimes see a version of this equation expanded with a factor for
pressure pr sq. foot, but since this is normally set to 1, in most cases it
is simply left out of the equation.

But The Dellenbaugh angel still has its limitations.

Some boats are build to sail with a maximal heel of 10 degrees, some with a
heel of 30 degrees. Some will be out of control at 20 degrees some are well
behaved even at 40 degrees of heel.

Marchaj and others have written about this. One place I remember is the
appendix 1 of "Seaworthiness - The Forgotten Factor", but you can surely
find better references.

Personally I'd say that a boat is overpowered when it doesn't handle well
anymore - my girlfriend would say the boat is overpowered when it is
unpleasant to sail.


How about wings in the future of sailing?

If you mean winged masts, one main problem is that they can't be taken down
when you dock or moore the boat. How would you feel leaving your boat in the
marina with the sail still up? I don't remember the story exactly, but Steve
Killing described (in "Yacht Design Explained") some extraordinary measures
that were taken to avoid the damage of the winged mast catamaran Stars and
Stripes (Americas Cup defender), when the boat was not sailing.

So, I don't imagine that the winged mast will become wide spread in the
following years, but it might find a few niches like maybe some racing cats
either small enough to have the mast easily removed after a sail or
exclusive enough to be lifted out of the water and stored in a "hangar",

Peter S/Y Anicula

"The Carrolls" wrote:

What makes a sail boat overpowered? how much sail is too much per foot
of length?

The length is not the most relevant factor.
Sailarea/displacement is better but still not good.
Stability at 15 degrees would be a good illustration of a boats
ability to carry sails, but still not anything near exact.

Another thing that matters is the rig type and shape. A low and long
schooner rig can have more area than a tall slooprig. The aspect ratio of
the rig would be a factor.

Dellenbaugh coefficient or angel takes most of this into consideration and
is a fairly good expression of the boats ability to stand on its legs. It
illustrates the heeling angle at approximately 8 m/s.

In metric The Dellenbaugh angel =

279 x SA x h
---------------
D x GM

279 x (Sailarea (triangular) x Heeling arm) / (Displacement x Metacentric
height)

(In foot, use 57.3 instead of 279)
You can sometimes see a version of this equation expanded with a factor for
pressure pr sq. foot, but since this is normally set to 1, in most cases it
is simply left out of the equation.

But The Dellenbaugh angel still has its limitations.

Some boats are build to sail with a maximal heel of 10 degrees, some with a
heel of 30 degrees. Some will be out of control at 20 degrees some are well
behaved even at 40 degrees of heel.

Marchaj and others have written about this. One place I remember is the
appendix 1 of "Seaworthiness - The Forgotten Factor", but you can surely
find better references.

Personally I'd say that a boat is overpowered when it doesn't handle well
anymore - my girlfriend would say the boat is overpowered when it is
unpleasant to sail.


How about wings in the future of sailing?

If you mean winged masts, one main problem is that they can't be taken down
when you dock or moore the boat. How would you feel leaving your boat in the
marina with the sail still up? I don't remember the story exactly, but Steve
Killing described (in "Yacht Design Explained") some extraordinary measures
that were taken to avoid the damage of the winged mast catamaran Stars and
Stripes (Americas Cup defender), when the boat was not sailing.

So, I don't imagine that the winged mast will become wide spread in the
following years, but it might find a few niches like maybe some racing cats
either small enough to have the mast easily removed after a sail or
exclusive enough to be lifted out of the water and stored in a "hangar",

Peter S/Y Anicula

The Carrolls wrote:

What makes a sail boat overpowered?

Having too much sail area for it's righting moment.

how much sail is too much per foot of
length?

That's not a good way of determining the need for power from the sails. LOA
or LWL do not really determine the capacity or the stability of a given boat.
Length is linear, the overall size is cubic.

For example, imagine two 30' sailboats. One is a heavily ballasted full keel
boat with a 3.5/1 Beam to Length ratio and relatively firm bilges. It could
carry several hundred square feet of sail in normal weather. The other is a
voyager canoe... L/B is about 6:1 no ballast, lightly enough built that a
tall mast & tight rigging is going to distort the hull. It will only need a
hundred square feet of sail to go as fast as the other boat, possibly less.

Usually the relative horsepower of sailboats is indicated by the Sail
Area/Displacement ratio but that can still be somewhat misleadng.

How about wings in the future of sailing?

Wings are awesome but they have some disadvantages. It's hard to trim them
because you can't see the lee side telltale, it's complex to make them twist,
they are heavy and bulky to stow, they can't be reefed, etc etc.

Back in 1987 Dennis Connor did not believe that a wing sail would be faster
than a soft sail on his 60' America's Cup cat. They built the two cats and
one had a Rutan designed hook-top wing that was designed to allow limited &
controllable twist, and also have a spinnaker set from it for off the wind.
The wing sail cat was about 15% faster IIRC even though it's surface area was
smaller than the sail area of the soft sail cat.

Fresh Breezes- Doug King

So all cats are overpowered?
"DSK" wrote in message
...
The Carrolls wrote:

What makes a sail boat overpowered?

Having too much sail area for it's righting moment.

how much sail is too much per foot of
length?

That's not a good way of determining the need for power from the sails.
LOA
or LWL do not really determine the capacity or the stability of a given
boat.
Length is linear, the overall size is cubic.

For example, imagine two 30' sailboats. One is a heavily ballasted full
keel
boat with a 3.5/1 Beam to Length ratio and relatively firm bilges. It
could
carry several hundred square feet of sail in normal weather. The other is
a
voyager canoe... L/B is about 6:1 no ballast, lightly enough built that a
tall mast & tight rigging is going to distort the hull. It will only need
a
hundred square feet of sail to go as fast as the other boat, possibly
less.

Usually the relative horsepower of sailboats is indicated by the Sail
Area/Displacement ratio but that can still be somewhat misleadng.

How about wings in the future of sailing?

Wings are awesome but they have some disadvantages. It's hard to trim them
because you can't see the lee side telltale, it's complex to make them
twist,
they are heavy and bulky to stow, they can't be reefed, etc etc.

Back in 1987 Dennis Connor did not believe that a wing sail would be
faster
than a soft sail on his 60' America's Cup cat. They built the two cats and
one had a Rutan designed hook-top wing that was designed to allow limited
&
controllable twist, and also have a spinnaker set from it for off the
wind.
The wing sail cat was about 15% faster IIRC even though it's surface area
was
smaller than the sail area of the soft sail cat.

Fresh Breezes- Doug King

The Carrolls wrote:

So all cats are overpowered?

Did I say that??

DSK