Light Air Relationships

[Bob Herrick]

During a recent sail in 5 to 10 knot winds and calm seas, when our 22 stalled while tacking, we got into a discussion about the relationships between wetted surface, displacement, sail area and hull length with respect to light air performance.

Given that the CDs are full keel boats with a lot of wetted surface, the variables would seem to be displacement, sail area and hull length.

On the one hand, it was argued that a Typhoon might perform better in light air than our 22 because the displacement is about 1,000 pounds less. It also has less sail area, however. On the other hand, a CD27 is nearly four times the displacement but has much more sail area and a longer hull.

So the central issue was wether light air performance is relative among CDs or whether the larger boats with greater sail area and longer hulls will always out-perform the smaller boats.

This is really a dumb question but it was one of those discussions that muddled the thinking of folks who otherwise thought they had at least a few minimal clues about the mechanics of sailing.

Would someone care to clarify?

Thanks,

Bob Herrick



bherrick@krausonline.com

[len]

bob

am i glad you asked! - saturday in quincy bay sea lion made 6.1 knots (by knotmeter) when the true wind was less than 10 knots - she was on a beam reach with the mainsail and cruising spinnaker - glorious sailing - and they say cape dorys are slow, hah!

len



md.frel@nwh.org

[michael phillips]

Well, KAYLA, my CD28, is 5,000# heavier than Brigitta, my prior CD25, and the "extra" 140 sq ft of sail area does NOT make up the difference in very light air (2~5kts). However, when its 15~25 and gusting higher, I'm quite tickled to have that extra 2.5 tons!

And, contrary to some folks' belief, I have also found that inducing a little heel in very light air helps tremendously for Typhoons, CD25s and this CD28, YMMV...

-michael
s/v KAYLA
CD28 #318
Bluewater Bay FL



michael@bbsc.com

[Paul D.]

Bob,

I have owned a Typhoon and now a CD 33 and I believe the boats will move fine in light air with GOOD SAILS! A well trimmed, non-blown out main and properly sized genoa or drifter will push these guys nicely. I have passed MC scows in my Typhoon, largely due to the momentum generated by the displacement, but I had new sails and was trying hard.

I also agree with the previous post stating that inducing some heel goes a long way to increasing speed. Waves will slow us down no matter what. I am struggling with my roller furler genoa (20 Years old but in good shape) and it's weight as I know it does not compare to a good, hanked-on lighter genny. So that is my opinion, if you focus on good sails and weight distribution, it is a fun thing! My 33 yesterday was going 2.5-3.5 Knots and finished a tack in less than 5 knots of wind and flat seas, all 13,300 lbs of her. I was so proud, but I know I could boost that with new sails.

Paul Danicic
CD 33 Christine Lynn #77
Grand Marais, MN



menogyn@YMCAmpls.org

[Dan Moore]

Following up on the two previous comments about heel in light air - well said! and so very true. I had the opportunity to race a Tartan 30 (before CD days) and once had the misfortune to wind up at the dregs end of the start. Air was near calm for the whole race. With crew to l'wrd and forward of the mast, we passed every competitor in the race, all classes! and won!!!
Good sails, common sense, and sail the big ones like a dingy; the formula works.
dkm.TY 583
Bullocks Cove, RI



Dmoore@wheelerschool.org