[Public-List] Blown out sails OK for crusing
Don Campbell
dk.campbell at sympatico.ca
Sun Jan 9 08:33:44 PST 2011
All I can say is amen! The biggest problem for the converted is to
convince those who like "good" old sails to get that new sail in the
first place in order to actually feel the difference and become a
convert to enjoying some power to drive their boat and therefore enjoy
some fun while sailing.
The one thing you must remember regarding a transfer from a racing
sail to a cruising sail (at least in my sail inventory) is the slight
degree of loss of shape (competitiveness) to effect the transfer.
It takes very little loss of shape to take the edge off a good
sail, when the difference of a few boat lengths over a race makes the
difference between winning and losing. When this loss of power happens,
a change of sail (to new) is necessary. This often depends upon those
against whom you compete and how often they get new sails too.
If you want to look at the math of this, it gets to be very small
numbers. For example in a mid wind range race, with an average speed of
5.0000 knots over a 5.0 mile race, that race will have a time duration
of 1 hour. Let us assume two boats are in the race with good crews and
no one makes a mistake throughout the race so both boats are able to run
at a constant average speed for the hour. (This rarely happens, but for
the math it is easier.) Say the second boat finished in the 1 hour. If
the first boat finished ahead by exactly one Alberg 30 boat length, then
its distance travelled in the same time would be 30 feet more than the
second place boat. Since s = d / T, where d is distance, s is speed,
and T is time, then the difference in speed of the two boats is s1-s2 =
(d1/T1) - (d2/T2) = (d1-d2)/T, since both boats are timed in 1 hour or
3600 seconds. Distance 2 is the full racecourse so 5.0 miles or 5.0 x
6076.1 feet. Distance 1 is 30 feet more than distance 2. Thus the
difference in speed is (30410.5 - 30380.5 ) / 3600 = 0.0083 feet per
second or about 1/10 of an inch difference in average speed per second.
This amounts to us being able to say that this difference is valid per
second per boat length as well. Therefore if you are getting 10 boat
lengths behind at the finish, (which many would say was a comfortable
win for the winner and a definite loss for the second boat), then you
are a huge 1 inch per second different in speed! Most cruisers would say
that is negligible, - but there is no gold for the racers in the second
boat who are 10 lengths behind per hour! However, over the time period
of a day cruising for 8 hours, that small difference amounts to almost
4/10 of a mile.
Just a brief comment about Michaels' two sails: Excessive luffing
of a 110 for only a minute in a bit of a blow will finish that sail's
shape, regardless of how new it is, because it will lengthen the leech
from the whipping action and make that sail untrimable. The 150 is far
less likely to undergo excessive luffing because it is never flown in
those big breezes. Chronological age is not the only criteria for
ending the useful life of a sail.
Don #528
1294590824.0
More information about the Public-List
mailing list