Weighing in on the iron keel avourdupois discussion..
I have had the p-15 Keel out of Aillte twice, and weighed
it on our bathroom scale.... and it was 68Lbs. At the the
time we bought our P-15 we were told.."100 lbs of ballast,
70lbs in the iron centerboard, and 15lbs each in the two
concrete blocks glassed into the bilges on either side of
the centerboard trunk..., so Cap'n Judy's calculation
seems to be right on the mark!
Cheers, Bruce
Bruce Hood , P-15 "Aillte", Sail no. 1246
Chico,California
"Judith Franklin Blumhorst, DC" wrote:
> 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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