Rig Power Factor

[johnarmitage]

I want to run an experiment related to the practice of rig configurations as an indicator of windspeed and power in a session. It will be really easy for you to help, plus fun and interesting.

Here goes:

On the forum, the way we all report the conditions is by our sail and board size, in Sq. meters and liters. The lower the value of both, the better, as an indicator of more wind power. Of course, these figures do not take into account the weight (and in my theory, height) of the sailor. As I am 6'5", 205lbs, I need to add ~ one meter and ten liters to what other sailors report as comfortable, to calibrate to my sailing experience. My rig is always 1-1.5 m larger than anyone else on the water. Now, I do prefer to sail a bit overpowered, but we'd all agree that body mass is a factor in rig selection.

Here is my idea, The Rig Power Calculation:

1. Multiply your sail size by the board flotation. (e.g. 5.0 x 92 = 478)
2. Multiply your body weight by your height (e.g. 6.4 x 205lb = 1312)
3. Divide the first number by the second (e.g. 478 / 1312 = .3643292....)
4. Round answer to two numbers and drop the decimal point. (e.g 36)

The smaller the number, the more power is needed. You could argue that height is irrelevant, and that would make a simpler calc, but I think it is relevant because the height acts as a weight multiplier due to added leverage.

Here is how my quiver scores, large to small, with my typical windspeed range for the rig, and the percentage of time in a season that I use that rig.

1. 7.3m x 120L / 1312 = 67, 19-22 kts, 23%
2. 6.2 x 120 / 1312 = 57, 20-23, 3 %
3. 6.2 x 92 / 1312 = 44, 22-26, 42%
4. 5.5 x 92 / 1312 = 39, 25-30, 23%
5. 5.0 x 92 / 1312 = 36, 30-35, 10%
6. 4.2 x 92 / 1312 = 30, 35-42, 2%

I would say I've averaged about 25 sailable days a year, I typically seek out high-wind days and spots and rig for the lulls. I prefer speed and power to doing tricks. (I just hate to slog, and my large board has an older, narrow hull...but these are nuances. I think heavier sailors start slower but have more high end)

My request is this: Can you respond your RPC numbers (Rig Power Calc) for your quivers? It would be interesting. If it makes sense, when we describe conditions on the forum, we can then use our RPC numbers (if we remember them :-p)

I can compile and share the results here.

[beallmd]

I think I speak for most of us when I say you have overwhelmed us. And I am often accused of being too scientific, told to get a life etc. What I always find interesting, in a qualitative way, is how little return one gets by using bigger and bigger sails after, say, a 6.5. I don't know if this can be calculated.

[isobars]

There's WAY too much personal preference involved to get scientific about it. I've seen a bunch of similar-sized sailors side by side enjoying sails ranging from 3.7 to 6.5 on boards from 65 to 100 liters. Our biggest guy, @ 240#, is usually on the smallest sail because he can loop it more easily; our oldest geezer, @ 155#, is usually on a half meter larger sail. Just a few weeks ago five of us had a fantastic evening session together, each of us dialed in perfectly as we tore some great Gorge swell new ones for 2-3 hours. We came in only because we couldn't see anything any more, great big grins on our faces in shared ecstasy. We were each a bit surprised at the range of "perfect sail sizes" we were using: 4.2 @ 140#, 4.4 @ 135#, 4.7 @ 155#, 5.2 @ 240#, and 6.2 @ 190#, all on 80 +/- 8 liters.

Wanna know what the wind speeds were? Just ask: 4.2, 4.4, 4.7, 5.2, and 6.2.

Stick that into your equations and run 'em!

Mike \m/

[vikingsail]

(Warning tangent alert ) The problem is, that even when we sail in locations with windmeters, they are usually not accurate for one reason or other. Use of formulas is great to answer off season questions about quiver setup but once you get to the beach you need to be able to look at the whitecaps, use your past experience and judgement and then make a decision on what gear to use. Plus you need to factor in fin type and area. (thats enough to make everyone's head spin). For example at Soundside Avon NC the wind outside is always at least 5 mph then the windmeter mounted on the chair. At Great Sacandaga Res. there is a meter 1/2 mile from the beach which reads high. It says we should be planing but one look at the water and the sailors confirms we're slogging. Sailing on rivers you have to add/subtract the current. ETC.
I understand you want to build your confidence in your rigging decisions. But the best way to do that is to sail and experience your local conditions. Based on the sizes you listed you have a well spaced Quiver to begin with and a good idea of the wind ranges. now you need to watch the caps on the water and see what it's blowing.