Mac,
Can't argue with a bathroom scale, although some folks would like to :)
I just went and measured my 1985 keel . It's 53" x 21.5 x 7/8", or,
converted to cubic meters, 0.1634 cubic meters. Elemental iron is 7874
kg/m^3, which would mean my keel weighs about 275 pounds, if made of
elemental iron.
Looks like it's nowhere near the advertised 370 pounds, unless there's some
lead in there... hmmm, how much lead would I have to add to get to 370
pounds... get out my calculator here....
Hey wait a minute, lead weighs 11340 kg/m^3. Iron has a density that 69% of
lead.....
.0163 M^3 of lead weighs 185 kg, or 407 pounds. 69% of 400 pounds = 275
pounds.....
If 275 pound iron P19 keels were made of lead they're weigh 400 pounds or
so...
If 69 pound iron P15 keels were made of lead, they'd weigh 100 pounds.
but they've always been made of iron.
Mystery solved. Some airhead calculated the weight of the keels (or whatever
you want to call the things if you're gotta splitting hairs) as though they
were made of lead.
The old brochure from the 80's not only has the sail areas wrong, it also
has the keel weights wrong. And (I'm quite sure) the total displacement
listed wrong too.
Judy B
-----Original Message-----
From: Mac Davis [mailto:mcmd@innet.com]
Sent: Thursday, May 11, 2000 1:36 PM
To: Potter Email List
Subject: [WWP] Re: P19 keel weight (was Have the "keel" galvanized?)
Hi Judy:
Your reference to a 390# keel tripped a trigger. We had this discussion a
couple of years ago, and the concensus was that there was no way the
standard P19 sheet steel keel (48 x 21 x 3/4 before milling) could meet its
advertised weight. Since Kelpie's keel is removed at the moment, I hauled
my trusty Sunbeam bathroom scale down to the garage and used it to weigh the
keel. My keel weighs 255 pounds (± 3 as I moved it around on the scale.)
Since this scale has been verified accurate at 202 lbs by a doctor's beam
balance, I am confident that it was an accurate test.
Mac Davis
Kelpie, WWP19#804
Aripeka, FL
<snip> What I did with my 390#
> "lifting keel" on the P19 -- get the boatyard to drop it and let two of
> their guys put it on a saw horse for me. I cleaned up the nicks, smoothed
> the bottom where I ground it up on the "ramp" and re-epoxied. Then I put
a
> coat of Micron CSC anti-fouling on it. I let the strong guys put it back
in
> the boat for me and installed a new steel cable while I was at it.
<snip>
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