Hi, Glenn, and thanks for your input (crossposted to RBB). I've left the
original thread attached to bring the RBBs up to speed.

Since you're building one, and have done extensive research on all aspects
of your boat, I'm interested to know what you'll do about a keel for RUTU
(apologies if it's been covered already some time in the past - I don't get
over to 'building' very often).

I'm also interested in your opinion, if you have one, of Mars Metals'
approaches to afterfits, and, if you've had any exposure to the
modifications I'm speaking of. Anecdotal experience suggests that it's a
neutral effect, or, worse, frequently, a negative effect. Of course,
perhaps the add-ons already identified were homegrown, and Mars Metals'
approach is engineered, which, of course, would make a tremendous
difference.

Thanks.

L8R

Skip

--
"Twenty years from now you will be more disappointed by the things you
didn't do than by the ones you did do. So throw off the bowlines. Sail away
from the safe harbor. Catch the trade winds in your sails. Explore. Dream.
Discover." - Mark Twain
"Glenn Ashmore" wrote in message
news:OAjEb.6979$JD6.5687@lakeread04...
The Scheel keel was developed back in the '60s but you don't see them as
often anymore. I know pacific Seacraft and a few other builders still
offer a Scheel option. The flaired camber at the botom adds weight down
low which imcreases righting moment for the same amount of draft.
Theoretically it also increases lift but increasing lift down low sounds
counter-productive to me. The outward flair and wide slow convex bottom
also disrupts the formation of the tip vortex to a limited degree.

The advent of bulbs and wings reduced the attractiveness of Scheel
keels. Besides adding more weight down low while maintaining the
thinner camber and shorter cord, bulbs also act as an end plate reducing
the tip vortex better than the Scheel and therefore total drag.

Skip Gundlach wrote:

So, we're looking at boats, and Henry Scheel comes to light. He's
patented
a keel that several manufacturers are paying royalties to use, and what
I
read suggest that rigorous tank testing holds out the superiority to
straight keels, so, presumably, it must be worth *something*...

However, just a Henry Scheel design does not a Scheel keel include. Too
bad...

For those not familiar, it's got some of the attributes of a wing and
some
of a bulb, but primarily greatly increases holding power and reduces
vortex
drag over that of a standard keel, particularly beneficial to a shoal
draft
need, without the anchor-digging-in attributes of a wing.

So, the boats I'm looking at don't have this keel. I've read of those
cutting off the bottom of a straight keel and adding a bulb, or
equivalent,
to achieve a shoal draft with the same equivalent weight. They've done
this
perhaps by somehow attaching at the bottom, or, as one site I
discovered,
bolting two lead halves to the remaining keel, forming sort of a bulb
wing.

Now to the question. Have any of you done, or know someone who has, an
addition of such a bulb/wing to an *existing* - not shortened - keel?
The
benefits I'd see are better holding, and more ballast, as low as
possible,
against a minimal overall increase in weight (projected is from 30000 to
maybe 32/33000 pounds displacement, with that increase also applying to
the
current 8400# ballast, light by my thought).

I'm more interested in experience stories, if there are any, or
engineering
reasons for or against, as opposed to 'I think it would...' information.

Thanks.

L8R

Skip (and Lydia)



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

My keel is an 8,750 pound bulb/fin. It is sort of a compromise. One of
my criteria was good up wind and light air performance. When John Fox
started work on my design he had been building flat out racing boats so
the first proposal had a 9' draft wing. We compromised with a 7' draft
beavertail bulb. Beavertails count mightily against you in most
handicapping systems but that was not a concern for me.

As I said, the advantage of the bulb besides reducing draft for the same
RM is the end plate effect and the beavertail is supposed to split up
the remaining vortex.

I talked to Mars about casting it for me but their price was a little
over $1.40/pound plus some extra charges for waste disposal and
transportation if I provided the plugs and bolt frame. That was 5 years
ago. Being me, I set about collecting wheel weights and cast the bulb
myself a couple of years ago. I have finally built up the nerve again
and will be casting the fin just after Christmas. I figure to have
about 40 cents/pound in the finished keel. OTOH, the backyard may end
up with a Superfund designation some day. :-)

Mars does sell a bolt on winglet set for shortening keels but it takes
some design work to figure out the weight and location so that your RM
does not change much. There has to be a careful balance of added weight
and higher center of gravity. Also if the keel has a large dihedral
shortening the keel will shift the lateral center of force forward which
might make the boat a bit squirrley and hard to trim out. I would call
Mars and see what they say. They have already done the engineering and
have patterns for many different hulls. No matter what they say, ask
for references for boats similar to the one you are contemplating
modifying and check with the owner for actual results.

Keel design is a balancing act between stability, performance and
comfort. Production boat designers spend a lot of time and money trying
to arrive at a happy compromise that is best for the market the boat is
intended to compete in. Ssmall changes below the waterline can make big
changes in the way the boat sails. Some can be good but more can be bad.

Personally I would not consider a complete re-keeling of any boat. It
would be outrageously expensive and you run the risk of changing the
sailing characteristics of the boat in unpredictable ways.

Skip Gundlach wrote:

Hi, Glenn, and thanks for your input (crossposted to RBB). I've left the
original thread attached to bring the RBBs up to speed.

Since you're building one, and have done extensive research on all aspects
of your boat, I'm interested to know what you'll do about a keel for RUTU
(apologies if it's been covered already some time in the past - I don't get
over to 'building' very often).

I'm also interested in your opinion, if you have one, of Mars Metals'
approaches to afterfits, and, if you've had any exposure to the
modifications I'm speaking of. Anecdotal experience suggests that it's a
neutral effect, or, worse, frequently, a negative effect. Of course,
perhaps the add-ons already identified were homegrown, and Mars Metals'
approach is engineered, which, of course, would make a tremendous
difference.

Thanks.

L8R

Skip


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Hi Skip,

My employer, (Lyman Morse Boatbuilding Co.), has added scheel type keels to a
couple of the Sequin 44 sloops we built in the 80's. Mars Metal provided the
keels and Jim Taylor yacht design did the engineering. It's been a successful
retrofit, the first boat we did won it's class in last years Newport Bermuda.
The owner says the boat is more weatherly and can carry more sail as well.
Mars Metals makes a very nice keel. We use them exclusively.

Jared Crane
Thomaston Maine

I'm also interested in your opinion, if you have one, of Mars Metals'
approaches to afterfits

Mars Metals makes decent keels, no doubt about it. But they are a casting
facility, not yacht designers.

Run any of your idea past a yacht designer / naval architect to see if:

- the internal structure can take it
- the modification will improve performance
etc.

I think it would be a very hard to make a better keel with add on bulbs and
*improve* performance. More likely to just make things a bit worse. On
some boats you may be hard pressed to tell the difference


--
Evan Gatehouse

you'll have to rewrite my email address to get to me
ceilydh AT 3web dot net
(fools the spammers)