Re: Maximum efficient displacement hull speed - P19 hull speed

SolarFry@aol.com
Wed, 7 Oct 1998 17:24:31 EDT


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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In a message dated 98-10-07 12:28:47 EDT, you write:

<< Subj: RE: Maximum efficient displacement hull speed - P19 hull speed
Date: 98-10-07 12:28:47 EDT
From: eric@theftnet.net (Eric Johnson)
To: SolarFry@aol.com, (West Wight Potter Mail List)

> Basically, the
> Potter is limited by it's displacement to length ratio (DL).
> Being a light
> displacement vessel with an almost flat bottom should
> theoretically allow it
> to achieve and exceed high end of this range (1.6x WLL) for
> extended periods
> of time, while traditional heavy displacement wine glass hulls (Alberg
> Typhoon, Island Packet, Pacific Seacraft, etc.) would wallow in their
> troughs...

>
> With its biaxial glass, a displacement of 1300lbs and a waterline

>Dry< weight is in the neighborhood of 1300lbs. Displacement is another
thing altogether - I'm sure my boat, even when stripped down for racing,
displaces at least 2000lbs (ok, my crew and I are big!) I have to keep the
motor and battery attached since its usually after dark on my returns.

> length of
> 16'9" the P19 has a DL ratio of approximately 80 making it an Ultra light
> displacement sailboat (ULDB). The first ULDB, Windward Passage
> (DL=100) was
> built in 68'. Windward Passage beat every other sailboat of it's time for
> almost 15 years.
>
> If you take out the 1,200 lbs of extra "can't live without" gear
> we stick into
> our Potter19s,

like crew? :) Unless they go on a diet... In the drink with them... We don't
want no heavy sailors aboard while sailing in light winds only in heavy
winds... [ :^}>

>throw that Putt Putt in the drink, get rid of that huge
> battery, move the crew forward and put some nice racing sails
> (large spinnaker
> anyone?) and a masthead rig on, it should be a fast performer capable of
> exceeding that 1.6 for long and extended periods...

You have a better grasp around the theory than I do, and I appreciate your
comments. The modifications you describe would make the boat not be a P19 in
anything other than hull shape. In the real world, the empirical data
suggests 5.5 is achievable nearly indefinitely provided a fair wind and
large enough sails (its actually remarkably easy to achieve with the genoa
and a stiff breeze), but I don't think anyone here has held a higher speed
than that for any appreciable length of time. My GPS once reported I was
holding an average speed of 6 knots for about 10 minutes. The long time
period and averaging should be enough for GPS errors to cancel. This was an
add situation where a low spit of land upwind kept the water calm but the
wind stiff.

The difficulty of measuring speed with inexpensive units adds to the
confusion. I might break down and eventually buy one of those fancy
knotmeters that reads to the 100th of a knot.

I'd had a heck of a time getting enough weight forward to help, but I do
agree it does help quite a bit.

> Notwithstanding the safety record of ULDB's (Transpac, Around the
> world) we
> have hundreds of sailors that swear that heavy and slow a la
> "Island Packet"
> is better than light and fast a la "Windward Passage"...

Well, >better< is a subjective term and really requires knowledge of the
purpose for which the boat is intended. The light weight (and therefore easy
trailerability) makes the P19 better for me, but I'd definitely prefer a
heavier displacement boat for any long open ocean voyage, if for no other
reason than seakindliness.

> Since
> many of these
> "sailor's" do most of the writing, in sailing mags, they continue
> to expound
> their "heavy and slow" theories while ridiculing all the speed and safety
> records established by ULDB's. Their gospel remains that the only
> boat worth
> having is a heavy ponderous crab crusher limited to less that
> 1.34 x WL Length
> with a DL of 300 or more... To fit their ends they publicly claim
> no sailboat
> can exceed this limit. They have done this for so long and so loudly that
> almost everyone believes them... Woe to anyone that does not agree...

True. Ever seen a Melges 24 sail? Thats gotta be a ULDB, faster (especially
in acceleration) than anything I've ever seen. Its amazing to watch them
tack at high angles downwind; the increased apparent wind they generate
doing so makes up for the longer distance they travel. This is true for many
boats (though not potters AFAIK), but on the Melges it is taken to an
extreme.

> Now, Off the pulpit, back to the Stock Market and the soothsayers
> of doom at
> CNBC...


heh heh I'd rather discuss sailing! :) I'd love to hear what anyone else has
found to improve speed. I did finally get a genoa, but haven't raced it yet.
I will race across Puget Sound in the Rum Run on Nov. 7th, so I'll get a
chance to try it then.
>>

I fear I will never go for long ocean voyages... They are not what they are
cracked up to be... Further, Panama canal transit soured me on intercountry
travel... My sailing will remain local (USA) and no more than 2 days
offshore... The P19 will be the largest sailboat I will ever own... I believe
in fast and furious... It is more comfortable to get there in 5 hours than in
10 no matter how "seakindly" the hull is... You can go lots further...

I had a friend with a Cal 25 that would plane the damn thing on a broad reach
with 25 MPH of wind right next to my 17' Montauk Whaler doing approximately 18
- 22 MPH. He would leave a rooster tail behind him for quite a long stretch at
a time. Sometimes he would even pass me... In the harbor, she moved like a
powerboat... I could swear the damn thing had a 100HP engine in it... But,
close inspection revealed It was completely gutted inside, nothing but the
inner hull, no sink, no cushions, no motor, no fuel, no water, no cabin
lights, no batteries, no foam, no ropes, no anchor... Four life preservers, a
whistle and a crew of four die hard sailboat racers was the only thing aboard.
Maybe he had one of those 300lb thrust Minn Kota's? To this day I have a hard
time believing he did not have an engine hidden somewhere in there... although
I searched repeatedly and never found one...

Next time you race... leave the battery, motor, water, cushions, anchor, extra
everything, ashore... Sail or row it out there! Move the crew forward, don't
pinch and let her fly freely... Visualize and find the groove... Also, leave
the extra crew behind... an agile crew of 2 including captain is enough... She
will surprise you...

S F
BTW: My P19 has achieved GPS/Apelco knotmeter speed of 12 MPH* surfing a wave
into inlet in 15 MPH winds... My wife was up forward in the cabin... I sail
the open ocean...

*Got you there! Ha hahahahahah ha ha... LMHOROTF...

LMHOROTF = laughing my head off rolling on the floor...