[Alberg30] Positive Stability Range

[Dave Terrell]

My 40 year geometry suggest the following

The fore triangle is a right triangle. This allows one to calculate the unknown side using the pythagorean theorm. A squared + b squarded = c squared. If A is 10.5 (J) and B is 36 (I), C is 37. 5. If I remember the discussion from last year correctly we determined that the real forstay length was in the range of 36' 8" or 36' 10" depending on the fitting one has at the deck level

.05 % of the hypothetical forestay length squared gives 70.3 square feet for the storm sail

.05 % of the real forestay length squared gives 67.7 square feet for the storm sail - assuming a forestay length of 36' 10"
I converted the 10 inches to decimals. 

My figures are a bit higher than Cole's figures but I am not sure why - probably because one does not really use all the acutal length of the forestay in a real sail and so one should not use the whole length of the forestay  for calculation purposes. I any case it's fun to actually use HS math sometimes even if I missed something here.



>>> GreekSailor at worldnet.att.net 03/05/03 02:17PM >>>
The forestay length is the "I" measurement of the sail plan which is 36'.

Kasia #383

-----Original Message-----
From: public-list-bounces at alberg30.org 
[mailto:public-list-bounces at alberg30.org]On Behalf Of Alfredo
Sent: Wednesday, March 05, 2003 7:59 AM
To: public-list at alberg30.org 
Subject: Re: [Alberg30] Positive Stability Range



 Thanks everyone.
I'm reading about storm sails(Coles' Heavy weather Sailing). It suggest the
Trysail to be no more than a third of the area of the main. In our case 73
sq feet. And the Storm Jib about 5% of forestay lenght sqared. Any idea
about the forestay lenght?
Thanks again.
Alfredo
 George Dinwiddie <gdinwiddie at alberg30.org> wrote: Alfredo wrote:
> Greetings,
>
> Does anyone happen to know the positive stability range of the Alberg
> 30?

Back in 1994, Jack Hornor estimated the positive stability range to a
bit under 120 degrees. Judging from the graph he gave out, I'd say
about 118 degrees.

> Also, I know the total working canvas area of our boats. But, what's
> the area of just the main?

The sailplan (http://www.alberg30.org/boat/A30sailplan.jpg) shows a
figure of 221 sq. ft. for the main. The fore triangle is 189 sq. ft.

- George


--
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Hope your road is a long one. George Dinwiddie
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from 'Ithaka' by C.P. Cavafy
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