Yes and no. The boat will probably steer ok, but the rig balance may
be stuffed. All the ideas suggested so far are worth a try. I like
the higher mast as there is more air up there, especially in under 6
knots when the wind is laminar. Issues with weight and windage when
reefed, which is why I am looking at telescoping, although with an
unstayed mast, i am not entirely convinced it is worth the effort
unless there are bridges, trailers etc involved.
I also like a screecher off an extension of the jib boom, sheeted to a
track off the side of the main boom. May have to rig a brace to the
front of the jib boom to trim it, but in light air, not a big deal.
Tried this with a spinnaker once, worked ok, but there was not a lot
of breeze. The main problem with light air sails is that you put
them up in 5 knots of breeze, the boat accelerates to 5+ and they see
near enough 10 knots apparent. Things start to get seriously loaded.
Get a puff to 10 knots and they either break or have to be very heavy.
regards,
Rob
On Thu, Apr 23, 2009 at 11:01 PM, Gardner Pomper <gardner@networknow.
>
>
> 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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