[Public-List] hull speed

[Gordon Laco]

And then there's surfing...

TOUCH WOOD, (my Folkboat under restoration) touched 11.2 once surfing on a
wave when broad reaching under spinnaker.  We were out in the open in
Georgian Bay on a day when the wind had been blowing solidly from the NW for
several days... Judging wave heights is difficult but I think they were over
12'.  We caught one particular wave and were able to surf down it twice just
like a surfer.  Down we went the first time, as we neared the bottom we bore
up a little to a reach and climbed it.  Nearing the top, we bore away again
onto a broad reach and down we went.  That's when she touched 11.2 knots.  I
shouted to my friend Boyd that I thought we'd pull the stick out of her but
it was worth it.  We lost the wave on the third try.

We got home to Midland and found we'd averaged just over 8knts on the
passage.  That in a 25' heavy(ish) displacement full keeled wooden yacht
with a LWL something like 19'!  Best of all we didn't break or strain
anything.  The best SURPRISE has ever done on the same run was touch 9 once;
but she hasn't been so lucky with the wind and waves (yet).

Gord #426 SURPRISE


On 15/11/11 7:22 AM, "Mike Lehman" <sail_505 at hotmail.com> wrote:

> Scary times huh George? But consider this...when over-powered by sails , you
> are healing over 20, 30, 40 perhaps more degrees. This increases your LWL
> and reduces your wetted surface. In fact, when the boat is laying on her
> side she starts to take on the properties of a planning hull, which is why
> she is able to achieve the speeds under sail. I wouldn't recommend reaching
> with a spinnaker in 35 knots, it's too....
> 
> -----Original Message-----
> From: George Dinwiddie
> Sent: Monday, November 14, 2011 8:46 PM
> To: Alberg 30 Public List -- open to all
> Subject: Re: [Public-List] hull speed
> 
> Jeffrey,
> 
> On 11/14/11 6:45 PM, Jeffrey wrote:
>> Gordon,
>> 
>> With respect, I don't think it is possible to power an A30 hull to 7-8
>> knots. Hull Speed is somewhere around 6.2 knots. My 20hp can power the
>> boat
>> to just over 6 knots at max rpm, but the noise and fuel consumption is
>> wicked. I've hit 7 knots and more for very brief periods of time under
>> sail
>> when hit with a gust, but never under power. These speeds clocked with
>> GPS.
> 
> Oh, you can go faster than hull speed.  It's just that the power
> required to do so goes up quite fast as the boat starts climbing it's
> own bow wave.
> 
> I've been on an A30 going in excess of 10 knots (sometimes pegging 12 by
> the knotmeter), but they get pretty squirrelly with that much of the
> boat out of the water.  This was night-racing on Kittwake in 40+ knots
> going wing-and-wing with a reefed main and the #2 genoa poled out on the
> spinnaker pole.  It tore the spinnaker pole track off the front of the
> mast and the tiller head twisted off the rudderpost twice.
> 
> And ask Mike Lehman about the 10 knot spinnaker deathroll.
> 
>   - George



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