On 1 Nov 2003 13:28:49 GMT, (William R.
Watt) wrote something
.......and in reply I say!:

Bill....if I may address you as such...

You ask for power formulae for a _sail_...then argue?

Terry Spragg ) writes:

It's all in the sail trim, lad.

************************************************** ****************************************
Until I do the other one,this one means nothing
Nick White --- HEAD:Hertz Music

remove ns from my header address to reply via email

!!
")
_/ )
( )
_//- \__/

Old Nick ) writes:
On 1 Nov 2003 13:28:49 GMT, (William R.
Watt) wrote something
......and in reply I say!:

Bill....if I may address you as such...

You ask for power formulae for a _sail_...then argue?

clarify. some responses did not address the question.
you can go back and re-read the original question if you like.

--
------------------------------------------------------------------------------
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 scaned diagrams of a possible sprit sail and put them on my website. So
far I just use the wetted surface and displacment to determine the sail
area. I still have more calculations to do for it. There's a sail cutting
diagram too. To use as much of the sail material and to keep the centre of
effort low I did not follow the recommended proportions in John Leather's
"Spritsails and Lugsails". I drew a sail more like older less efficient
sprit sails. BTW if you chose the length of the foot and leach then you
can use Leather's proportions to find the head and luff independent of the
mast length, although he relates them all to mast length. Maybe I'll
describe that in the design text later.

the diagrams are at www.ncf.ca/~ag384/Solo15.htm. I won't link it to my
home page until its finished which could be quite a while yet. Its still
very rough. I'm spending as much time trying to figure out how to use the
computer as I am trying to work out the design of the boat.




--
------------------------------------------------------------------------------
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

On 2 Nov 2003 16:09:57 GMT, (William R.
Watt) wrote something
.......and in reply I say!:

Old Nick ) writes:
On 1 Nov 2003 13:28:49 GMT, (William R.
Watt) wrote something
......and in reply I say!:

Bill....if I may address you as such...

You ask for power formulae for a _sail_...then argue?

clarify.

A sail cannot be quantified. Too many variables.

some responses did not address the question.


hmmm... they may not have _answered_ it....

you can go back and re-read the original question if you like.


No need. AFAICS, the reason there is such a spread is that conditions
apply.
************************************************** ****************************************
Until I do the other one,this one means nothing
Nick White --- HEAD:Hertz Music

remove ns from my header address to reply via email

!!
")
_/ )
( )
_//- \__/

thank you all for the informative discussion.

Henry Miller ("Sailing Yacht Design" (1965) also disagrees with me,
writing "As the driving medium, the size of the sail plan obviously should
bear some relationship to the resistance of the hull. Unfortunately there
is no direct means of evaluating the driving force that can be produced by
a given size sail plan under specific wind conditions." That seems odd to
me. Surely a somewhat idealized model can be described mathematically and
boundary values computed. I'm having a samilar problem comparing heeling
force of the sail to righting moment of the hull and crew to see how much
sail to carry. The books discuss the Dellenbaugh the angle I was asking about
in an earlier thread and another method both of which depend on
measurements taken from the dynamics of the completed hull or model. I must
declare I'm disappointed. I think I'll keep working on these analytically
to see if I can get any useful numbers.

I appreciate the need to compare with data from exsisting boats to check
any calculations. I realize its the practice among yacht designers to use
comparisons where they can't calculate numbers analytically. I've got lots
of data on specific day sailers and light crusiers to use, and some
scatterplot summaries of data on daysailers and light cruisers, all from
books at the public library. The design I'm playing with appears to be
reasonable by comparison. As I work on the design I have to answer a lot
of questions which refine my ideas about how the boat will be used and
under what conditions. Its interesting to try and come up with a roomy
ultralight cruiser with sufficient power and response to work the shifty
winds on inland lakes and rivers like the waters we have on the Rideau
system, hopefully without resorting to auxilliary power.

--
------------------------------------------------------------------------------
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