Re: Stus-List Keel movement in C&C 24

Fri, 24 Apr 2020 18:20:43 -0700

If you lubricate the threads, reduce the torque by 10%.  The torque values on the list (which I generated decades ago) are based on dry threads.  They calculate a little high on the nebulous yield strengths of stainless steels.  Be careful going on the high side. 

Neil Schiller
1983 C&C 35-3, #028, "Grace"
Whitehall, Michigan
WLYC
(1970 Redwing 35, C&C 35-1, Hull #7, "Corsair" when the tables were generated) 

On 4/24/2020 1:23 PM, Russ & Melody via CnC-List wrote:


Hi Chris & Josh,


I am not in agreement that keel bolts can only be tightened while the 
boat is ashore.



While that is a convenient activity during the annual haulout period 
that Eastern boats get, it is not entirely practical for us on the 
West Coast or the lads down south. We might only haul every two or 
three years.



The technical sheet in the link shows the theoretical load on a 1" 
bolt (torque to 350 ft-lbs spec) is ~12,000 lbs. This is more than the 
weight of the keel such that it does not matter whether the keel is 
supported on the ground or hanging in the water, the joint is held 
firmly together by one keelbolt. The rest are not required to do 
anything at this time.

https://www.hobson.com.au/files/technical/utd-gd-torque-tension.pdf


I suggest that the proper procedure for tightening keelboats be 
observed whether the boat is in water or in the yard.


For a 1" keelboat to 350 ft-lbs torque:

    start with centre nut and take it to 250 ft-lbs, repeat for other

    nuts alternating for and aft sequence 
    remove centre nut and lubricate, retorque to 300 ft-lbs, repeat as
    for other nuts as above 
    retorque centre nut to 350 ft-lbs, repeat as for other nuts as above 

Then you can a have a beer Chris and reflect on how fortunate you are 
to be sailing B.C South Coast. Anything 100 miles to the east of you 
is beyond Hope.

   :)     <VBG>

Cheers, Russ
East side o'  Vancouver Island


At 08:15 AM 4/24/2020, you wrote:

Chris,


The prevailing wisdom of this list suggests that the keel bolts only 
be torqued while the boat is resting on its keel, generally about 60% 
of it's weight depending on the design.  In this way you are not 
turning the nuts against the weight of the keel or even trying to 
compress the bedding material.  IMO, it is likely that you will find 
more movement in the nuts when you retorque on dry land.



I am not familiar with the design of your particular boat but some 
boats have keel bolts which are entirely inaccessible with the mast 
in place.  Make sure there isn't one (or two) hiding somewhere.


Josh MuckleyÂ
S/V Sea HawkÂ
1989 C&C 37+
Solomons, MD


On Thu, Apr 23, 2020, 20:59 Chris Bennett via CnC-List 
<cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote:


    Status update: I ended up torquing the keel bolts. They were not
    incredibly loose but all of them needed tightening, two by a turn
    or more and the other two by less than a turn. I will know if
    this removed the keel movement when the boat is next hauled out,
    although I am also thinking of diving on her to see if I can
    detect any wiggle that way (I live in BC and the water is pretty
    cold but manageable for a few minutes with a wet suit - I hope!).
    I believe that a very small looseness in a narrow keel root would
    result in a fairly noticeable movement at the tip of a 3 foot
    keel - even 1/8 inch of movement over 2 inches width would
    translate into a couple of inches at the tip, if I have that
    right. So hopefully this was the issue!

    I took Drifter for a sail today after rebuilding the mast step
    and did not notice any flexing or movement in the floors or hull
    (made pencil marks on the floors and adjacent hull skin and
    checked on different tacks).  I also checked the tabbing under
    the settees on one side and found it intact, so suspect that the
    surveyor may have jumped to conclusions when he said the hull had
    been compromised and that was what was causing the keel movement.
    Â
    Â Thanks again to everyone for their suggestions.

    ChrisÂ

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