"Thom Stewart" wrote in message ...
Now let's talk about "Spitfires" sail plan.
Can you figure why they have what they have and why? That should be an
interesting reply.


What they have is sails not suited to the task at hand which task is breaking speed
records. To go faster they need higher aspect ratio sails with a more rounded top to
reduce drag caused by the tip vortex those flat-topped sails create.

CN

Capt. Neal® wrote in message
...
What they have is sails not suited to the task at hand which task is
breaking speed
records. To go faster they need higher aspect ratio sails with a more
rounded top to
reduce drag caused by the tip vortex those flat-topped sails create.

CN

How do you explain why a glider (no engine, slow speed)
has wings with much higher aspect ratio than a jet fighter...?

A jet fighter uses massive horsepower to stay in the air. It only needs short, stubby wings
because it operates at very high speeds.

A sailboat operates at far lower speeds and so does the glider. The question you
asked merely confirms the fact that the catamaran should have sails shaped more
like those of a glider than those of a jet fighter.

CN


"Edgar" wrote in message ...

Capt. Neal® wrote in message
...
What they have is sails not suited to the task at hand which task is
breaking speed
records. To go faster they need higher aspect ratio sails with a more
rounded top to
reduce drag caused by the tip vortex those flat-topped sails create.

CN

How do you explain why a glider (no engine, slow speed)
has wings with much higher aspect ratio than a jet fighter...?

Capt. Neal® wrote in message
...
A jet fighter uses massive horsepower to stay in the air. It only needs
short, stubby wings
because it operates at very high speeds.

A sailboat operates at far lower speeds and so does the glider. The
question you
asked merely confirms the fact that the catamaran should have sails shaped
more
like those of a glider than those of a jet fighter.

CN


"Edgar" wrote in message
...
How do you explain why a glider (no engine, slow speed)
has wings with much higher aspect ratio than a jet fighter...?

This is where you are wrong. The contraption we are talking about is not a
catamaran but a hydrofoil. The only thing it is any good for is a blast
along a broad reach foilborne. If you tried to sail the thing close to the
wind it would lose so much speed it would drop off its foils and just wallow
about waiting for the helmsman to bear away and get up some speed again.
Hence it is pointless to give it high aspect sails which would increase
efficiency to windward in a normal catamaran.
All it requires is brute force from the sails on a broad reach and minimum
heeling moment. Hence they went for a lot of sail on a low aspect ratio
rig.

Crapton,

You're blowing smoke. Spitfire doesn't give a damn about slow speed
sailing. It is interested in the very upper end of sailing speed.

That is the reason for the choice of "Low Aspect" sails. Larger sail
area with less heeling moment. Burying a Foil to heeling would kill
speed faster than "Air Vortex"
They increased SAIL AREA without increasing Heeling Force by adding a
SECOND SAIL without increasing HEELING FORCE.

Two sails: Increasing driving force of the wind without increasing the
Winds leverage for heeling. This increase of the second sail, off to the
side rather than a Ketch Rig, made the Multi Hull necessary. This had
the advantage of adding Hydrofoils at a wider angle. Increasing speed is
made possible by sailing flat, using LOW ASPECT SAILS without the need
to carry a Heavy Weighted Keel to overcome the Heeling Force created by
a TALL MAST carrying HIGH ASPECT SAIL (Sail with a larger curve)

That, my friend, ends my attempt to ENLIGHTEN you. Open your mind and
learn

Lesson over, filleting complete.

Ole Thom

You're all wrong! The Spitfire has a high aspect rig. Here's another
pictu

http://wingsail.neuralfuzz.com/wingsaildesigns.htm

By having two sails the center of effort is kept low, but the efficiency
of the sails stays high.

Thom Stewart wrote:
Crapton,

You're blowing smoke. Spitfire doesn't give a damn about slow speed
sailing. It is interested in the very upper end of sailing speed.

That is the reason for the choice of "Low Aspect" sails. Larger sail
area with less heeling moment. Burying a Foil to heeling would kill
speed faster than "Air Vortex"
They increased SAIL AREA without increasing Heeling Force by adding a
SECOND SAIL without increasing HEELING FORCE.

Two sails: Increasing driving force of the wind without increasing the
Winds leverage for heeling. This increase of the second sail, off to the
side rather than a Ketch Rig, made the Multi Hull necessary. This had
the advantage of adding Hydrofoils at a wider angle. Increasing speed is
made possible by sailing flat, using LOW ASPECT SAILS without the need
to carry a Heavy Weighted Keel to overcome the Heeling Force created by
a TALL MAST carrying HIGH ASPECT SAIL (Sail with a larger curve)

That, my friend, ends my attempt to ENLIGHTEN you. Open your mind and
learn

Lesson over, filleting complete.

Ole Thom

They need to be *higher* aspect ratio than that.

CN


"Jeff Morris" wrote in message ...
You're all wrong! The Spitfire has a high aspect rig. Here's another
pictu

http://wingsail.neuralfuzz.com/wingsaildesigns.htm

By having two sails the center of effort is kept low, but the efficiency
of the sails stays high.

Thom Stewart wrote:
Crapton,

You're blowing smoke. Spitfire doesn't give a damn about slow speed
sailing. It is interested in the very upper end of sailing speed.

That is the reason for the choice of "Low Aspect" sails. Larger sail
area with less heeling moment. Burying a Foil to heeling would kill
speed faster than "Air Vortex"
They increased SAIL AREA without increasing Heeling Force by adding a
SECOND SAIL without increasing HEELING FORCE.

Two sails: Increasing driving force of the wind without increasing the
Winds leverage for heeling. This increase of the second sail, off to the
side rather than a Ketch Rig, made the Multi Hull necessary. This had
the advantage of adding Hydrofoils at a wider angle. Increasing speed is
made possible by sailing flat, using LOW ASPECT SAILS without the need
to carry a Heavy Weighted Keel to overcome the Heeling Force created by
a TALL MAST carrying HIGH ASPECT SAIL (Sail with a larger curve)

That, my friend, ends my attempt to ENLIGHTEN you. Open your mind and
learn

Lesson over, filleting complete.

Ole Thom

Jeff,

I stand corrected on the sails. What is the Aspect Ratio number? I
thought it would be a rather "Low" number for the speeds she was
attaining.

Ole Thom

Thom Stewart wrote:
Jeff,

I stand corrected on the sails. What is the Aspect Ratio number? I
thought it would be a rather "Low" number for the speeds she was
attaining.

Ole Thom

I haven't found the specs for the boat, but the line drawings show the
aspect ration to be over 3 to 1. Plus, with the square top, the
effective ratio is much higher. Think of it as simply removing the top
quarter of a sail - the part that generates little lift but contributes
heeling moment. Add to that the fact that the sails are actually wing
sails, with two layers of cloth over a rotating mast, and internal
battens adjusting curvature ... I'm sure they have just the lift to drag
ratio the designers want for the boat. Its hard to argue with 45 knots.

Crapt. Neal® wrote:
... To go faster they need higher aspect ratio sails with a more rounded
top to
reduce drag caused by the tip vortex those flat-topped sails create.


So, a foil with a rounded or pointy tip doesn't cause a tip vortex?

Where's Jax when you need him?

DSK