shortening the draft on a long fin keel...
 

Hi,
My husband is planning to shorten the draft on our fin keel Carter33'
1972. It draws like 6' now and he plans to take off a foot. Once doing
this, he wants to add a bulb or wings to the sides of the fin to add
the weight back onto it.
If anyone knows of any good sources on the web of others being
successful with this kind of project, please email the links to


Thanks
Karolina

shortening the draft on a long fin keel...
 

On 18 Dec 2006 06:03:16 -0800, "KVL" wrote:

If anyone knows of any good sources on the web of others being
successful with this kind of project, please email the links to

Lots of people have tried home made wings on their keel but I have
not heard of a single success story however, and most have been
removed.

You will probably end up destroying both the value and sailing
performance of the boat.

Why not sell it and get something designed as a shallow draft boat?

shortening the draft on a long fin keel...
 

Karolina,
I can appreciate the requirement. However, you had better do it right or you
will lose all the value in your boat. Please consider a Sheel keel. They are
the answer to your requirement. Properly constructed, with the correct
ballast load schedule and you will have a winner with a 4 foot draft. They
really work exceedingly well. Before doing this contract a qualified naval
architect. It will save untold grief in the end.
Steve

"KVL" wrote in message
ups.com...
Hi,
My husband is planning to shorten the draft on our fin keel Carter33'
1972. It draws like 6' now and he plans to take off a foot. Once doing
this, he wants to add a bulb or wings to the sides of the fin to add
the weight back onto it.
If anyone knows of any good sources on the web of others being
successful with this kind of project, please email the links to


Thanks
Karolina

shortening the draft on a long fin keel...
 

The Carter33' is a very beautiful boat, but when we aquired her (for
almost nothing) she was land sinking and had water & mold in her for at
least 3 years- after being abandoned. We had to redesign the entire
interior, so it's very customized - not much original structure is left
in the interior. The hull and the deck were in superior condition, but
the cabin top was soaked under the fiberglass to the balsa wood core.
We had to completely make a new cabin top core from the inside of the
cabin. My husband is a mechanical engineer- and quite handy with
rebuilding and designing almost anything. So I have no doubts, he would
do a superior job with the shorteneing of the keel . We plan to keep
this boat for many years and many of the places we like to sail too and
anchor (at our convenience-not waiting for high tides) are tight at mid
to lower tides - where we live.
It would still be great to get some more ideas of tohers who have
attempted this kind of project and were actually successful. They're
out there somewhere. Some people have knack of accomplishing things
they get told "can't be done right.
I will look into all the suggestions.

Much Thanks!
Karolina

Steve Lusardi wrote:
Karolina,
I can appreciate the requirement. However, you had better do it right or you
will lose all the value in your boat. Please consider a Sheel keel. They are
the answer to your requirement. Properly constructed, with the correct
ballast load schedule and you will have a winner with a 4 foot draft. They
really work exceedingly well. Before doing this contract a qualified naval
architect. It will save untold grief in the end.
Steve

shortening the draft on a long fin keel...
 

On Mon, 18 Dec 2006 11:41:05 -0800, KVL wrote:

The Carter33' is a very beautiful boat, but when we aquired her (for
almost nothing) she was land sinking and had water & mold in her for at
least 3 years- after being abandoned. We had to redesign the entire
interior, so it's very customized - not much original structure is left
in the interior. The hull and the deck were in superior condition, but
the cabin top was soaked under the fiberglass to the balsa wood core. We
had to completely make a new cabin top core from the inside of the
cabin. My husband is a mechanical engineer- and quite handy with
rebuilding and designing almost anything. So I have no doubts, he would
do a superior job with the shorteneing of the keel . We plan to keep
this boat for many years and many of the places we like to sail too and
anchor (at our convenience-not waiting for high tides) are tight at mid
to lower tides - where we live.
It would still be great to get some more ideas of tohers who have
attempted this kind of project and were actually successful. They're out
there somewhere. Some people have knack of accomplishing things they get
told "can't be done right.
I will look into all the suggestions.

You have a big advantage with respect to cost if your husband can do the
actual work. So use the savings to hire a good naval architect or
marine engineer to do the design work. Even an otherwise competent
engineer could screw this up without the proper training and experience.
Your husband would probably enjoy working with one of these guys anyway.
That experience alone may be worth the cost.

Naval architect and marine engineer Eric Sponberg has a similar project
featured on his website: http://www.sponbergyachtdesign.com/Magic.htm It
might be best to work with someone nearby, and/or someone familiar with
your boat.

Matt O.

shortening the draft on a long fin keel...
 

It's one thing to redo a deck, interior or even entire electrical and
plumbing systems. Anyone with decent mechanical skills can tackle this.

But something that will affect how the boat actually SAILS when it's
navigating out of the shallows is not just a simple mechanical task. As
others have suggested, it's worth seeking out an actual naval architect
and/or someone that's actually DONE THIS to THAT MODEL boat.

It'll do you no good to have all that work go to waste only to discover how
poorly it sails once it's back in the water.

shortening the draft on a long fin keel...
 

Bill Kearney wrote:

But something that will affect how the boat actually SAILS when it's
navigating out of the shallows is not just a simple mechanical task.
As others have suggested, it's worth seeking out an actual naval
architect and/or someone that's actually DONE THIS to THAT MODEL boat.

As a naval architect, I would say just go ahead and do it. When you look at
the incredible variety of keel sizes and shapes, you'll realize that it is
actually hard to come up with something that flat out won't work. If you
were racing and obsessing about gaining or losing an eighth of a knot in
identical conditions, it would be one thing. The chance that you won't like
the way the boat sails if you do a modification like this half way
intelligently is finite, but small.

The Sponberg solution linked in the other post is elegant. If the OP's
husband did all the other stuff and can avoid poisoning or burning himself
with the lead, he should be able to do this successfully with not much more
guidance than that and some volume calculations he should be able to manage
with a quick look at a geometry or naval architect text book.

If he just cut the keel off and carried more gear and stores or put the
weight in the bilge, the boat would not be as powerful or fast to windward
but quite possibly not by an amount that he would notice without careful
comparison. There have been many boats offered in two versions with keel
configurations that vary by this amount. I wouldn't recommend this as the
course to take but just to point out that this is hardly as critical an
issue as some responders are maintainng.

Still, it's a big, messy, and dangerous job. I'd focus on that instead of
the results.

--
Roger Long

shortening the draft on a long fin keel...
 

Thanks for your support. We're not too concerned with gaining speed,
and as it is now, this model boat isn't that terrific with the way it
sails. Of course we were used a Philip Rhodes - full keel, (that we
still own, but are selling) but we like the interior space of the
Carter for pleasure trips - weekends on the bay and such. This why we'd
like to have shorter draft on it - to access some of the places we
liked going with our Rhodes - which the draft is 4'9".
My husband likes a challenging project... he's a go getter!

Karolina

Roger Long wrote:
As a naval architect, I would say just go ahead and do it. When you look at
the incredible variety of keel sizes and shapes, you'll realize that it is
actually hard to come up with something that flat out won't work. If you
were racing and obsessing about gaining or losing an eighth of a knot in
identical conditions, it would be one thing. The chance that you won't like
the way the boat sails if you do a modification like this half way
intelligently is finite, but small. ETC
--
Roger Long

shortening the draft on a long fin keel...
 

On Tue, 19 Dec 2006 14:21:17 GMT, "Roger Long"
wrote:

Still, it's a big, messy, and dangerous job. I'd focus on that instead of
the results.

That's very true and an important point. I know people who have tried
similar mods and been very disappointed.

The whole wing keel concept was really applicable only to the old
style 12 meter Americas Cup boats because of a design quirk in the
rating rule. As others have pointed out, the best bet for a cruising
boat is something called a scheel keel, or possibly a bulb.

http://www.cs.brown.edu/people/jfh/p...AQ/node16.html

shortening the draft on a long fin keel...
 

Wayne.B wrote:
On Tue, 19 Dec 2006 14:21:17 GMT, "Roger Long"
wrote:

Still, it's a big, messy, and dangerous job. I'd focus on that instead of
the results.

That's very true and an important point. I know people who have tried
similar mods and been very disappointed.

The whole wing keel concept was really applicable only to the old
style 12 meter Americas Cup boats because of a design quirk in the
rating rule.

This is nonsense. It may be true that the particular design used in
the 12's wouldn't be appropriate for a cruiser, but the basic concept
is valid and quite useful. Simply put, the water that flows under the
tip of the keel reduces the effectiveness of the bottom foot or so of
the keel. The wing keel prevents this flow and keeps the last foot of
the keel effective. This permits reducing the draft by roughly a foot
in many cases. In addition, the ballasted wings are essentially a
bulb. It should be noted that the primary purpose is to reduce draft;
the deep keel will normally be more effective overall.

The quirk in the 12 meter rule was a draft limit of about 8.8 feet
(16% of WL plus .5 meter) so the wing allowed Lexcen to get better
upwind performance out of that draft. The story gets a bit more
complicated, but that's the most important part.

As others have pointed out, the best bet for a cruising
boat is something called a scheel keel, or possibly a bulb.

The Scheel Keel is certainly a neat design - it has the same design
goals as listed above for the wing keel, but it has less drag (or is
it more lift?).



http://www.cs.brown.edu/people/jfh/p...AQ/node16.html

This is a pretty simplistic view of the topic.