Great explanation.
What is the correct torque to apply?
Thx.
David
C&C30MK2 Impulse
On September 22, 2017 11:23:45 AM Rick Brass via CnC-List
<cnc-list@cnc-list.com> wrote:
Lisle;
As others have said, you appear to be looking at the C&C Smile. That is a
crack in the bottom paint or fairing compound covering the joint where the
top of the lead keel meets the bottom of the fiberglass keel stub. As these
things go, yours appears to be pretty minor. On older boats with a swept
back keel, I’ve seen gaps at the leading edge of the joint of a quarter
inch or so.
The probable cause is that the tension on the keel bolts is too low. When
the boat was built, a sealing compound was put between the top of the keel
and the bottom of the hull, and the bolts were torqued tight. As the boat
heels when sailing, the keel flexes slightly to the side, and the bolts
tend to lose torque over time. That leads to the crack – the C&C Smile – in
the hard paint or fairing compound covering the joint. On older boats with
the swept back keel, the crack can be accentuated if the boat is blocked at
the back of the keel, or with too much of the boat’s weight supported to
far back. Some of the listers have indicated damage to the keel stub from
hard groundings, but I don’t see any real evidence of that in your photos.
The condition can be cosmetic, or a real problem. Probably cosmetic in well
over 90% of the time. You can tell if it is a real problem if you put the
boat in the water and water leaks into the bilge from the joint.
The solution is to torque the bolts properly, and retorque them
periodically. My 38 had a fairly large smile when I bought her in 2003. The
bolts got retorqued when I had some keel work done in 2004. Again in about
2009, when we also opened up a small groove along the smile, put 5200
sealer in the groove, faired the joint, and applied a layer of glass cloth
from the leading edge of the joint to about 2 feet back to address the
cosmetic issues. No smile when the bottom was painted in 2013. A slight
crack was evident last winter when I painted the bottom, and a little water
seeped out of the 5200 sealer – so I retorqued the bolts again (it had been
8 years after all) and applied another layer of glass before the bottom paint.
If you find you have a water leak – which I suspect is not likely given the
appearance of the smile, the fix is to drop the keel, apply 5200 as a new
layer of sealer, and torque the bolts properly. That stops the leak, but
won’t stop the smile (5200, after all, is flexible and that is what causes
the smile). Fairing and a fiberglass band over the joint will eliminate the
cosmetic issues so long as you retorque the bolts every few years into the
future.
As others have said, get a good survey. You are already paying a relatively
high price for late 80s boat, and I really doubt that putting another
$5000 or more into rebidding the keel would be a desirable activity.
Bruce;
The reason that torqueing the bolts while on the hard is preferable to
doing it in the water might be that, when in the water, a goodly portion of
the effort is directed at supporting the weight of the keel instead of
applying force to the seal. On the hard, with the weight of the boat
holding the keel tightly to the stub, you would tend to get a tighter seal
and more tension on the bolts, which should slow down the inevitable
loosening of the bolts as the keel moves around while sailing – and thus
require less frequent torqueing or reduce the development of the next smile.
Rick Brass
Washington, NC
From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Bruce
Whitmore via CnC-List
Sent: Friday, September 22, 2017 11:54 AM
To: cnc-list@cnc-list.com
Cc: Bruce Whitmore <bwhitm...@sbcglobal.net>
Subject: Re: Stus-List question about a C&C 30 mkii keel
Hi Josh,
Quick question which I've wrestled with in my mind - Why torque the keel
bolts on the hard? Since the keel will spend most of its time hanging from
the bottom of the boat in the water, isn't it better to torque the bolts in
the specific situation where the stresses will be applied?
Thanks for the insights,
Bruce Whitmore
(847) 404-5092 (mobile)
bwhitm...@sbcglobal.net <mailto:bwhitm...@sbcglobal.net>
----------
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