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07-09-2013, 13:00
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#46
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Registered User
Join Date: Oct 2012
Location: Currently Tasmania after Pacific crossing
Boat: Catalina 42
Posts: 255
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Re: Keel Damage
On a cold dark night, far out to sea in 30 knots of wind, an issue like that keel...even patched would keep my mind and stomach churning!
Someone mentioned x-ray... that would seem the best cost effective least intrusive suggestion to see exactly whats going on inside that cast iron keel.
Thankyou for my lead keel Catalina!
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07-09-2013, 13:00
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#47
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Marine Service Provider
Join Date: Nov 2008
Location: Port Credit, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 7,060
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Re: Keel Damage
Quote:
Originally Posted by Jim Cate
G'Day BP,
In order for the differential in coefficients of expansion to cause the cracking there would have to be some significant changes in temperature. When the keel and lower hull are immersed in water which remains at a fairly constant temperature, I can't believe in this being the cause of cracking.
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Being in Canada cold temperatures are a bit of an issue particularly when boats are stored over the winter on the hard. Swimming in the deeper Great Lakes it is quite common to haver warm water around your upper body while your toes are turning blue. Alos when sailing from shallow water to deeper water where thera can easily be a 15 degree difference, the FRP and lead will change at distinctly different rates.
__________________
If you're not laughing, you're not doin' it right.
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07-09-2013, 13:03
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#48
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Moderator
Join Date: Jul 2009
Location: Sxm , Spain
Boat: CSY 44 Tall rig Sold!
Posts: 4,367
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Re: Keel Damage
Cracks are fairly common in bolted keels at the joint area, C&c are famous for keel smile, nothing can stop a small crack at the fairing , the keel work hard and flex at some extent, but most cracks are just cosmetic, and someone sugested glass the area to avoid see the crack next time, but be aware, because i see people doing that in serious cracks and big gaps making the isue worst, probably checking the torque at the keel bolts and the joint for leaks is the procedure, and a small crack is not a big deal.....serious gaps and long cracks are another history...
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07-09-2013, 13:09
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#49
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Moderator
Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 18,423
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Re: Keel Damage
Quote:
Originally Posted by boatpoker
Being in Canada cold temperatures are a bit of an issue particularly when boats are stored over the winter on the hard. Swimming in the deeper Great Lakes it is quite common to haver warm water around your upper body while your toes are turning blue. Alos when sailing from shallow water to deeper water where thera can easily be a 15 degree difference, the FRP and lead will change at distinctly different rates.
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Are you suggesting the photos show a failed joint between the GRP hull and the cast iron keel? because I beg to differ. From what I can see in this photo, I think this is a multiple cracks in the cast iron from possibly having hit something big and hard.
Would I buy the boat, sure but less the cost of fitting a new keel.
http://www.cruisersforum.com/forums/...7&d=1375549451
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07-09-2013, 13:51
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#50
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Armchair Bucketeer
Join Date: Oct 2006
Posts: 10,012
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Re: Keel Damage
Quote:
Originally Posted by boatpoker
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I don't dispute your experience - but my point still stands for OP......even if "Normal" does not mean you have to (or should) buy that deficiency.
BTW I call it a deficiency because if it was not then would be highlighted in the sales brochure as a plus point: " after a few years the keel will start to detach - to aid performance" .
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07-09-2013, 14:20
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#51
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Moderator
Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 18,423
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Re: Keel Damage
Quote:
Originally Posted by neilpride
Cracks are fairly common in bolted keels at the joint area,
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Not true, the sentence should read "cracks are sometimes seen between a bolted keel and the hull at the joint area", but not in the cast iron keel.
Quote:
Originally Posted by neilpride
C&c are famous for keel smile, nothing can stop a small crack at the fairing
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Okay
Quote:
Originally Posted by neilpride
the keel work hard and flex at some extent, but most cracks are just cosmetic,
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What? how does a piece of cast iron several inches thick flex? cast iron doesn't work harden.
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07-09-2013, 14:55
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#52
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Moderator
Join Date: Jul 2009
Location: Sxm , Spain
Boat: CSY 44 Tall rig Sold!
Posts: 4,367
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Re: Keel Damage
Quote:
Originally Posted by Pete7
Not true, the sentence should read "cracks are sometimes seen between a bolted keel and the hull at the joint area", but not in the cast iron keel.
Okay
What? how does a piece of cast iron several inches thick flex? cast iron doesn't work harden.
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Look, maybe you dont get the point or i dont explain very well, cracks are fairly common in fin keels with bolts, no matter if is lead or iron, and the cracks appear at the fwd or aft trailing edges where the metal joint the hull, FG stub or simple bolted keel flat to the hull like some builders do, and in most cases is cosmetic when fillers are used to hide the joint , fillers or primers and antifouling together, and yes belive or not Keels work when the boat heel or if is pounding in a seaway, iron or lead, the fairing actually just need a minimal inflexion to crack, or could be a mix between hull and keel , the keel is rigid , yes , the hull not, so just figurate,, cracks are notorious when the boats get older , haulouts, groundings, just the simple fact of sailing, etc. but yes if you prefer the term of flexing joint im ok with that to , Cheers...
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07-09-2013, 15:24
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#53
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Registered User
Join Date: Oct 2012
Location: Currently Tasmania after Pacific crossing
Boat: Catalina 42
Posts: 255
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Re: Keel Damage
Quote:
Originally Posted by neilpride
Look, maybe you dont get the point or i dont explain very well, cracks are fairly common in fin keels with bolts, no matter if is lead or iron, and the cracks appear at the fwd or aft trailing edges where the metal joint the hull, FG stub or simple bolted keel flat to the hull like some builders do, and in most cases is cosmetic when fillers are used to hide the joint , fillers or primers and antifouling together, and yes belive or not Keels work when the boat heel or if is pounding in a seaway, iron or lead, the fairing actually just need a minimal inflexion to crack, or could be a mix between hull and keel , the keel is rigid , yes , the hull not, so just figurate,, cracks are notorious when the boats get older , haulouts, groundings, just the simple fact of sailing, etc. but yes if you prefer the term of flexing joint im ok with that to , Cheers...
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Neil, I think you may be missing the point a little here....If you care to look again at the OP's photo of the damaged keel, the crack appears to be NOT in a straight line as per a keel/stub connection crack would appear.
This crack zigzags in many directions and clearly looks to me to be a fault within the metal keel....and not a joint movement crack!
Just my retired metalworker observation!
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07-09-2013, 15:41
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#54
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Registered User
Join Date: Sep 2011
Location: Good question
Boat: Rafiki 37
Posts: 14,138
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Quote:
Originally Posted by boatpoker
Being in Canada cold temperatures are a bit of an issue particularly when boats are stored over the winter on the hard. Swimming in the deeper Great Lakes it is quite common to haver warm water around your upper body while your toes are turning blue. Alos when sailing from shallow water to deeper water where thera can easily be a 15 degree difference, the FRP and lead will change at distinctly different rates.
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I'm no where near an expert, but I can confirm that hairline cracks are common on boats with bolted keels that I see up here on Lake Superior. I've always assumed it was due to the slight flexing, but perhaps temperature also plays a role. In any case, it's definitely not uncommon, and in my limited experience (and the expansive experience of my fellow sailors up here) almost always cosmetic.
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07-09-2013, 15:45
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#55
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Registered User
Join Date: Sep 2011
Location: Good question
Boat: Rafiki 37
Posts: 14,138
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Quote:
Originally Posted by Amnesia II
Neil, I think you may be missing the point a little here....If you care to look again at the OP's photo of the damaged keel, the crack appears to be NOT in a straight line as per a keel/stub connection crack would appear.
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I also agree, the pics are not cosmetic hairline fractures. These are not examples of keel bolt flexing. These look to be substantive damage. Impact? Rusting iron keel?
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07-09-2013, 16:20
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#56
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Moderator
Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,151
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Re: Keel Damage
Quote:
Originally Posted by boatpoker
Being in Canada cold temperatures are a bit of an issue particularly when boats are stored over the winter on the hard. Swimming in the deeper Great Lakes it is quite common to haver warm water around your upper body while your toes are turning blue. Alos when sailing from shallow water to deeper water where thera can easily be a 15 degree difference, the FRP and lead will change at distinctly different rates.
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Well, BP, lets look at the numbers: For a typical fin keel
As stated above, the respective coefficients for GRP and Pb are 15.1 and 14
times 10 to the minus 6 inches per inch per degree F. Thus for your 15 degree temperature differential, we get (15.1-14) *10^-6 * 15 per inch of keel root length. For, say, a keel with a 6 foot root, this works out to
1.1*10^-6*15*72= 1188*10^-6 inches = a bit over one one-thousandth of an inch. I doubt if that differential would cause cracking. Even if you throw in storage on the hard in winter, with temperatures one hundred degrees below the summer norm we only get about 7 thousandth of an inch, spread out over the 72 inch length. I'm not competent to really judge whether that is too much, but my seat of the pants guess is that is not.
For boats in more reasonable climates where they stay in the water full time the temperature range, of course, is far less, yet we see this sort of keel root cracking from time to time. It seems to me that we must look for a different cause.
BTW, the coefficients quoted are from Coefficients of Linear Thermal Expansion
should you wish to check on them.
Cheers,
Jim
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
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07-09-2013, 22:17
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#57
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Moderator
Join Date: Jul 2009
Location: Sxm , Spain
Boat: CSY 44 Tall rig Sold!
Posts: 4,367
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Re: Keel Damage
Quote:
Originally Posted by Amnesia II
Neil, I think you may be missing the point a little here....If you care to look again at the OP's photo of the damaged keel, the crack appears to be NOT in a straight line as per a keel/stub connection crack would appear.
This crack zigzags in many directions and clearly looks to me to be a fault within the metal keel....and not a joint movement crack!
Just my retired metalworker observation!
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Yes i know , im just trying to explain why sometimes we get that tiny cracks at the joint , nothing related to the OP pictures, the Op keel in my opinion need a sandblasting and see if there is still clean metal somewhere.. we do a similar job here with a bene 50 last year , iron keel complety rusted, sandblasting, we found a lot of piting and deep damaged, primed, epoxy fairing, more primer, and done... even we sandblast the torpedo bulb at the bottom with the boat lifted with the crane. Cheers..
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