Lateen Potter

Gordon (hlg@pacbell.net)
Thu, 11 Mar 1999 01:18:15 -0800


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Steve Barnes wrote:

>Lars S. Mulford wrote:
>>
>> Secondly, when Barry Foy finally set up "Always" correctly in regard to mast
>> position and secure mounts, she really performed startlingly well. I know
>> that folks like Harry and others have tried to figure out why this is, but I
>> never did figure it out. All I know is that except on extreme points of
>> sail, "Always" would outperform standard rigged P15s. Now granted, the
>> standard rigs point a bit higher (as Harry has noted too) but the difference
>> is less than you'd think.
>
>I think I know why from reading "Sails" by Derek Harvey, a great book,
>by the way, with very readable clear explanations of the 10 most common
>sailing rigs, and lots more, too.
>
>As you point higher, turbulence will start in at luff edge of the sail
>and creep farther back along the sail, as you point higher and higher,
>until the turbulence spreads so far back along the foot length of the
>sail that the sail completely "luffs." As you point lower, turbulence
>will start in at the leach of the sail and gradually work it's way
>forward, the more you fall off, until the sail stalls. The key is the
>length of the foot. The longer the foot, the farther back the luffing
>can creep, or the farther forward the stalling can creep, without being
>completely stalled.

Okay.
>
>A P-14 with a 8' foot has a short amount of creeping distance compared
>to a 13' lateen foot. So even though not drawing optimally, the lateen
>sail can still be drawing adequately through a larger window of angle of
>attack. An optimally trimmed sloop rig with jib and main will
>theoretically be faster, but in practice is usually not, because it is
>much harder to keep the jib, main, and jib and main together, optimally
>trimmed.
>That window of acceptable angle of attack for the jib/main is very
>narrow and precise, and is usually not maintained for more than a few
>minutes at a time due to constant changes of wind velocity, swells,
>etc. And when you make one sail adjustment on a sloop rig, it usually
>means everything else is now off, and needs adjusting, also. With every
>adjustment it takes a few minutes to achieve a smooth flow of wind over
>the sails again. Good racers don't adjust constantly, just frequently.
>
>Is this all perfectly clear?
>
>To put it briefly, the lateen sail stays in adequate trim more of the
>time, more easily, with fewer adjustments, maintaining good air flow,
>than does the sloop rig. So I guess the casual lateen skipper will beat
>the casual sloop skipper, but watch out for those Judy's, Jerry's,
>Larry's, etc., those "technical sailors."

That agrees with my experience. It's a significant advantage to have only
one sail to adjust when tacking and correcting for wind shifts. I've been
able to stay ahead of casually sailed P15s and P19s when tacking up a
channel, but the experienced sloop sailor who has done some racing or
otherwise practiced getting the most from his boat will usually have the
edge. I'm self-taught and never did get the hang of adjusting the main and
jib at the same time I'm trying to find the optimum heading on the new
tack. Sometimes I used a boom on my jib (which doesn't overlap the mast),
and that allowed me to tack with just the tiller as I can do with the
lateen.

Another possible advantage of the lateen is the relative absence of twist
in the sail. The two spars of the lateen rig are connected at the tack, and
both spars are held against the mast, one by the halyard and the other by
the gooseneck. This geometry ensures the two spars are always in the same
plane (disregarding any flexing of the spars). With a gaff main or a
pseudo-gaff like the P15, the gaff (or long batten) is always further out
than the boom.

One would expect a lateen rig to be more efficient on its "good" tack than
its "bad" tack, the "bad" tack being when the sailcloth is lying against
the mast (the port tack on my boat, the starboard tack on Steve's). I
hadn't really observed that to be true until Dave and I were beating our
way back up the Bay last Saturday. I think Dave gained the most when
Manatee was on the bad tack. I can pull the main in further on the good
tack, which means I need to readjust the mainsheet at each tack for best
performance, but that is much less trouble than readjusting a jib each time.

Downwind, it's difficult to keep both sails of a sloop working, even with
the jib winged out with a whisker pole. On the lateen the full sail area is
always working. Also, with no stays, you can let the boom out a full 90
degrees or beyond.

>Of course the ability to put up more sail in light air, and less sail in
>heavy air, will make a difference, also.

But not as much difference as I had expected. With the low center of effort
and flexible spars I can comfortably carry on with the unreefed lateen when
the wind rises to the level where I would have reefed my gunter rig. That
is especially significant when you consider that my gunter rig had less
sail area (72 sq ft) than my Sunfish lateen rig (nominal 75 sq ft, but
measures 80 sq ft). I find a vang necessary when the wind comes up to
prevent the boom from lifting and the sail billowing and becoming difficult
to manage. I use a "Sunfish vang, which is just a line that pulls the
gooseneck down. I also have an outhaul adjustment to help flatten the sail
when necessary.

So far I haven't found my lateen Potter to be significantly slower in light
air either, but I haven't seen much light air in this area since I changed
to the lateen rig. I think both Steve and Lars felt the need for more
canvas when the wind was light. I can raise my mast to get the sail up
higher in light air but haven't tested that feature to see if it makes much
difference. I've only used the lowest of the three mast height settings.

Harry Gordon
P14 #234, Manatee
Mountain View, CA