its the angle of heel in a 16 mph wind (one pound per sq ft wind force).
the formula is ...

57.3 x SA x h x l
-----------------
D x GM

I know SA = sail area (sq ft)
D = displacement (pounds)

I don't know what h, l, and GM are.
Anybody know?

I think "h" is the height of the centre of effort of the sail. a note says
"from designed sail plan center to LWL plus 40% draft" it doesn't say if
the centerboard is up or down. I think it would be in feet.

"l" is "lpsf" in one location. I think that might be "lateral plane in sq ft"
but not sure. Waterline plane?

Not a clue what GM might be. Some kind of moment?

Thanks.
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In metric The Dellenbaugh angel =

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

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

It should illustrate the heeling angle at approximately 8 m/s.

I don't know what the Dellenbaugh coefficient it, but sounds as if it is
identical to the Dellenbaugh angle.

GM is metacentric height. Distance from G (gravitational center) to M
(metacenter).
h is heeling arm.
l is one ?


Peter S/Y Anicula



"William R. Watt" skrev i en meddelelse
...
its the angle of heel in a 16 mph wind (one pound per sq ft wind force).
the formula is ...

57.3 x SA x h x l
-----------------
D x GM

I know SA = sail area (sq ft)
D = displacement (pounds)

I don't know what h, l, and GM are.
Anybody know?

I think "h" is the height of the centre of effort of the sail. a note says
"from designed sail plan center to LWL plus 40% draft" it doesn't say if
the centerboard is up or down. I think it would be in feet.

"l" is "lpsf" in one location. I think that might be "lateral plane in sq
ft"
but not sure. Waterline plane?

Not a clue what GM might be. Some kind of moment?

Thanks.

"Aniculapeter" ) writes:

thanks for the additional info.
I can get the value for GM now.

l is one ?

mulitplying by unity doesn't make sense.
it does not change anything.


57.3 x SA x h x l
-----------------
D x GM

I know SA = sail area (sq ft)
D = displacement (pounds)

I don't know what h, l, and GM are.
Anybody know?

I think "h" is the height of the centre of effort of the sail. a note says
"from designed sail plan center to LWL plus 40% draft" it doesn't say if
the centerboard is up or down. I think it would be in feet.

"l" is "lpsf" in one location. I think that might be "lateral plane in sq
ft"
but not sure. Waterline plane?

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

I suspect the "one" refers to your original note of the equation being for
one lb per sf wind force (correlating to 16 mph wind speed). The formula
would still work for different wind forces.

One comment - the resulting angle is an approximation that is good for only
small angles of heel. The 57.3 and GM are related in that if you plot GM at
57.3 degrees (one radian) on a GZ curve (righting arm curve) and scribe a
line back to the origin, this line reflects the slope of the GZ curve at
small angles of heel. There is also a cosine factor which gets introduced to
both the sail area and heeling arm (h), so the applied heeling moment is
reduced as the boat heels. Fortunately, in all but a few rare cases, the
angle you get with the simplified formula will suggest a heeling angle
higher than you'd actually get on the boat.

Regards,

Don

Donald M. MacPherson
VP Technical Director
HydroComp, Inc.
http://www.hydrocompinc.com
tel (603)868-3344
fax (603)868-3366



"William R. Watt" wrote in message
...
"Aniculapeter" ) writes:

thanks for the additional info.
I can get the value for GM now.

l is one ?

mulitplying by unity doesn't make sense.
it does not change anything.


57.3 x SA x h x l
-----------------
D x GM

I know SA = sail area (sq ft)
D = displacement (pounds)

I don't know what h, l, and GM are.
Anybody know?

I think "h" is the height of the centre of effort of the sail. a note
says
"from designed sail plan center to LWL plus 40% draft" it doesn't say
if
the centerboard is up or down. I think it would be in feet.

"l" is "lpsf" in one location. I think that might be "lateral plane in
sq
ft"
but not sure. Waterline plane?

--
--------------------------------------------------------------------------
----
William R Watt National Capital FreeNet Ottawa's free community
network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

Don says:

Fortunately, in all but a few rare cases, the
angle you get with the simplified formula will suggest a heeling angle
higher than you'd actually get on the boat.


The thing to remember with Dellenbaugh angles is that they are for COMPARISON
purposes only. Any bearing on reality is, as Don pointed out, purely
coincidental. ;-)

Steve
Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/pr...cbweb/home.htm

You were right. It is "1", not "l". It was showing that the
comparison graph in the book uses a sail pressure of 1 lb/sq ft,
or about 16 mph of wind.

I found a pretty good explination of the Dellenbaugh angle at
www.kastenmarine.com/sail_area_ratios.pfd. Its defined there as...

57.3 X sail area X heeling arm X wind pressure
----------------------------------------------
displacement X GM

where GM is the distance between the boat's centre of gravity and
its metacentre. I guess that would be a vertical distance.

it also say's its covered in Skene's Elements so I've requested a
copy from the public library.

the comparison graph I'm looking at has the displacement and GM
"corrected for half load condition", and also uses a specific way
of calculating the heeling arm. I don't know how to compute
heeling arm. I can get the (free BluePeter) computer program to
calculate a metacenter for a half load. I hope to find out how to
calculate the heeling moment in Skene's so I compare the sail plan
on the design I'm playing with to the graph. all very interesting.

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