Automatic Sail Size Calculator

[James]

Hey Windsurfers,

Check out the automatic sail-size calculator I put together.

http://www.vims.edu/general/sailpaddle/SailCalculator.xls

Just enter your weight and it will tell you what sail size to use for
any wind in kts, mph, and kmph. Obviously there are other factors to
consider, but I think this could help people in optimizing their sail
quivers.

-James

[address @someplace.com Zephyr]

"James" <d0ug...@hotmail.com> wrote in message
news:1176904839.0...@n76g2000hsh.googlegroups.com...

James,

that's a pretty cool little calculator that you put together,
I ran it for myself at 175 lbs and it matched almost exactly how I use my
current quiver.

certainly at those sail sizes and wind speed combinations, I expect to be
just planning.

Thanks!

[outdrsmn]

On Apr 18, 11:13 am, "Zephyr" <an address @ some place .com> wrote:
> "James" <d0ugl...@hotmail.com> wrote in message

I like it, I plugged in my numbers and it was quite accurate as far as
planning threshold.
Match this with a board volume calculator and fin size selector and
you have just eliminated
the gear selection curve for most novice and "advancing to the next
level" windsurfers.

C

[timwn...@gmail.com]

totally sweet, was right on the money for me. I usually ride an 84
ltr JP FSW. I don't know much about the extremes of the curve, not
sure how fun it would be to try and sail the JP with a 12m2 sail. ;)

-Tim

[wind.sh@dow]

On 18 Apr 2007 07:00:39 -0700, James <d0ug...@hotmail.com> wrote:

>Hey Windsurfers,
>
>Check out the automatic sail-size calculator I put together.
>
>http://www.vims.edu/general/sailpaddle/SailCalculator.xls

Wanted: 15 meter sail. :)

Thanks, James, this is way cool.

[wsurfn]

Very fun, not a bad little tool.

Like most curves, I imagine it is more likely to be a little off for
the very big and very small.

I am the very big at just under #240

<14 = 11.0
15-18=8.5
18-22=7.5
22-27=6.3
27-32=5.2
>32=4.5

[hydrogimp]

Great sail size calculator James. I weigh about 210 lb and it agrees
well with my sail size for sea level conditions. However, I live at
4,700 ft altitude (in Idaho) and find that I need about a 15% larger
sail than at sea level due to decreased air density. You could
account for the density effect in your calculator since the force on
the sail scales with density times velocity squared. So, for the same
wind speed, the sail size scales with sea level air density divided by
local air density. I derive a simple algorythm for this sail size
ratio as 1 + (3.33*10^-5)*Altitude (ft). This gives a ratio at 4,700
ft of 1.16 which corresponds with my experience. You probably don't
need to worry about this correction at altitudes below about 2,000 ft.
Unfortunately, your calculator indicates that I need a 32 m2 sail for
today's conditions, so I think that I will pass on sailing (it's also
snowing outside).

[James]

I added a board size calculator and a fin size calculator to the
spreadsheet.

http://www.vims.edu/general/sailpaddle/SailCalculator.xls

I haven't added an altitude correction yet, but that's not a bad
idea. Anyone is welcome to take the calculator and modify it /
exploit it for the good of windsurfing.

[Tom - Chicago]

James - that is darn good work - and almost spot-on for me.

Tom - Chicago

[cosmicharlie]

Although, I didn't try the calculator, I see these figures roughly
match what I have used at the same weight. However, I find that I can
hold on to a 5.0 up to 35 and go to a 4.4 over that. I own a 4.0, but
never have used it. The 8.4 of mine I use up to 22 or 23, but
anything more will be dangerously overpowered. From there I go to a
6.5 or 6.7. Nevertheless, I doubt if the calculator would help me,
even if I had the time to check the computer at the beach. Often I'll
rig down because it's definitely easier to gybe that way. Phil at
InlandSea says that he thinks most sailors on the cape rig too big a
sail. I'm not sure if I agree, but it's worth thinking about.