I was thinking that with a ballestron rig, you eliminate the point of
sail factor, because you trim your sheets for an apparent wind
direction and then just rotate the mast to keep the sails at that
angle to the wind.
Anyway, is the end result of all this that one can have a large, light
air headsail without killing the balance?
Deferring to the expert,
- Gardner
On Thu, Apr 23, 2009 at 10:55 AM, Rob Denney <harryproa@gmail.
>
>
> G'day,
>
> No, it's not. The geometric centre of the sail is what is
> traditionally used, but it is an approximation, not the centre of
> effort. The coe moves around a fair bit depending on the point of
> sail, mast size and shape, sail shape and wind strength (especially
> with unstayed rigs, big roaches and jibs on unstayed masts). For
> getting started after sheeting on a big roached (probably oversheeted
> as the sheeting is set for higher apparent when the boat is moving)
> mainsail on an easy rig it can be 75% or more aft. If the mast is
> big diameter, with the topping lift strapped on hard to make the jib
> work well and the top of the main flag, coe can move ahead of the
> mast.
>
> regards,
> Rob
>
> On Thu, Apr 23, 2009 at 9:48 PM, Gardner Pomper <gardner@networknow.
> wrote:
>>
>>
>> I can calculate the center of gravity of a triangle, just by adding
>> the x coordinates and dividing by 3; then do the same with the y
>> coordinates. Is that they same as the center of effort?
>>
>> - Gardner
>>
>> On Thu, Apr 23, 2009 at 9:45 AM, barrie lyall <protocomposite@
>> wrote:
>>>
>>>
>>> Re Cof E, Simple one, if I remember correctly or correct me if i am
>>> wrong.
>>> Make a paper scaled pattern of the sail and find the centre balance point
>>> with a pin.
>>>
>>> --- On Thu, 4/23/09, Mike Crawford <jmichael@gwi.
>>>
>>> From: Mike Crawford <jmichael@gwi.
>>> Subject: Re: [harryproa] SA/D and Bruce number calculator
>>> To: harryproa@yahoogrou
>>> Date: Thursday, April 23, 2009, 9:17 PM
>>>
>>> <<Have you happened to run across any info on how to calculate the center
>>> of
>>> effort of a sail?>>
>>>
>>> (off-group) Nope. I don't think I'll bother going that far. I'll give
>>> Rob the specs I want and let him and the engineer help with the details.
>>>
>>> - Mike
>>>
>>>
>>> Gardner Pomper wrote:
>>>
>>> Hi,
>>>
>>> Thanks! That's cool!
>>>
>>> Have you happened to run across any info on how to calculate the
>>> center of effort of a sail? I have also been thinking about sailplans
>>> and am trying to figure how much headsail I can have before putting
>>> the COE too far forward for the ballestron rig to weathercock.
>>>
>>> - Gardner
>>>
>>>
>>>
>>
>
>
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