--- In

junkrig@yahoogroups.com, "Victor Winterthun"

<victor.winterthun@c...> wrote:

> Hi

> The usual way to compare sailarea is as follows:

> SA/volume^2/3 = max 13 (Motorsailer) If depl. is 18000lbs. will

it give 558 sq.ft.

> 19 Genrous

area " " " " 815 " "

> I have to admit that my own boat have 21, but I have to reef at

7m/s.

>

> The weight of 1 cu. ft of sea water is 64lbs.

> 18000lbs/64 = 281.25 cu.ft. = Volume of displasement.

> SA/281.25^0.667 = 16 ): SA = 687 sq.ft.

>

> Victor

Hi Victor

the trouble wth formulas containing two-thirds powers is that they

give me a headache (!) and I have to resort to using a calculator, so

much prefer to use 100 sq.ft. per ton as a rough-and-ready

yardstick.

Re: formulas - I actually prefer the formula that Tom Colvin uses,

i.e. Sail Area (in sq.ft.) divided by displacement (in 2240 lb long

tons) to the two-thirds power. Using this formulae, his Gazelle -

which at 18000 lbs is the same displacement as Ted Stone's hull - has

a SA/displacement figure of 212 when flying 854 sq.ft of sail (not

including jib). That's 107 sq.ft per ton using my yardstick.

Using this formulae, the Wylo 35 at 15400 lbs and 714 sq.ft.

mentioned earlier gives an SA/Disp figure of 198 [or 104 sq.ft per

ton], and Badger at 10,400 lbs and 600 sq.ft. gives a SA/Disp figure

of 216 (or 129 sq.ft per ton).

Clearly the lighter the boat, the more my yardstick is in error, as

can be seen with Pilmer (Kingfisher 20) at 2700 lbs and 227 sq.ft.,

giving a SA/Disp figure of 200, but a whacking 189 using this

yardstick.

So it appears that the 100 sq.ft per ton yardstick only has validity

for boats in the 6-9 ton class. (which just happens to be my area of

interest !)

However, I'd still respectfully suggest that Ted Stone's boat should

be flying at least 800 sq.ft. - the reason being that - if I

understand the dilemma accurately - it is not just a question of sail

area (which can always be adjusted later), but whether to fly two

masts or one. Retro-fitting from one mast to two could be an

expensive option, especially if the hull is at an advanced stage of

fitting-out.

Just my 2-penn'orth on this one. Going back to sleep now.

With best wishes

Colin