Hull keel joint and how long should epoxy keel treatment last?

benw

benw

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Have just visited boat since laying up. She is in a cradle mast up.
Have had the keel off during refit and keel was blasted back to bare and epoxy treatment applied. The hull keel joint renewed when the keel went back on as well as new keel bolts and backing plates. I am aware that this joint is made crafted out of sealant and that there will be some flex particularly in heavy seas etc. Very pleased with new immaculate joint, anti fouled and launched Dec 2012.
We came out at the beginning of November and have been in a cradle on the hard. It is apparent that there was no sign of the hairline cracking that we now have that is along the outer edge of the joint ie thinnest skimmed joint. I have a couple of observations:
The hull keel joint is now fairly evident when it wasn't initially when placed in cradle. Is this to be expected as the weight of the boat rests in the cradle? The wind age is causing some movement of boat naturally but would expect this naturally.
I had hoped to not see evidence of keel rust coming through this soon after being fully treated but the lead ballast and keel joint is evident on the aft end with a small rust blister.
Should I expect this after one full year afloat ie Dec to Nov?
Should I be more concerned re the hull keel joint hairline cracking?
We are a Sigma 38 fin keel.
Thanks in advance for any observations.
 
benw said:
Have just visited boat since laying up. She is in a cradle mast up.
Have had the keel off during refit and keel was blasted back to bare and epoxy treatment applied. The hull keel joint renewed when the keel went back on as well as new keel bolts and backing plates. I am aware that this joint is made crafted out of sealant and that there will be some flex particularly in heavy seas etc. Very pleased with new immaculate joint, anti fouled and launched Dec 2012.
We came out at the beginning of November and have been in a cradle on the hard. It is apparent that there was no sign of the hairline cracking that we now have that is along the outer edge of the joint ie thinnest skimmed joint. I have a couple of observations:
The hull keel joint is now fairly evident when it wasn't initially when placed in cradle. Is this to be expected as the weight of the boat rests in the cradle? The wind age is causing some movement of boat naturally but would expect this naturally.
I had hoped to not see evidence of keel rust coming through this soon after being fully treated but the lead ballast and keel joint is evident on the aft end with a small rust blister.
Should I expect this after one full year afloat ie Dec to Nov?
Should I be more concerned re the hull keel joint hairline cracking?
We are a Sigma 38 fin keel.
Thanks in advance for any observations.
Click to expand...


We had our lead keel off 14 yrs ago also by the same yard. there is no movement on JB`s keel / hull.
Do you need to "nip-up" any keel bolts, i must say we did`nt.
i have highlighted what you have written. do you have a lead keel, if so where / why is there rust ????
 
sailorman said:
We had our lead keel off 14 yrs ago also by the same yard. there is no movement on JB`s keel / hull.
Do you need to "nip-up" any keel bolts, i must say we did`nt.
i have highlighted what you have written. do you have a lead keel, if so where / why is there rust ????
Click to expand...

Thanks, I have posted a few photos on our blog
Http://orcanasigma38.wordpress.com
I must admit I was hoping not to have to think about this for a while given the extensive works completed by Foxs. Wondering if I should inform them of my findings? Or am I being naive?
 
ours is affixed to a keel stub that also gives a shallow bilge too.
It is movement that has cracked filler or epoxy,i would talk to Ralph on Monday. send him an email with the photos.
what is the rust, have you a lead keel


This was this year when we hauled out
The joint is clearly visible & not recessed like yours
IMG_08671_zps2da040aa.jpg
 
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sailorman said:
i have highlighted what you have written. do you have a lead keel, if so where / why is there rust ????
Click to expand...

It's a cast iron and lead keel. Cast iron at the top, lead at the bottom. The rust will be on the cast iron part, in this case on the aft end of the cast iron/lead join line. It read pretty clearly to me.
 
benw said:
Thanks, I have posted a few photos on our blog
Http://orcanasigma38.wordpress.com
I must admit I was hoping not to have to think about this for a while given the extensive works completed by Foxs. Wondering if I should inform them of my findings? Or am I being naive?
Click to expand...
Thanks will do, I think our keel joint is possible subject to more flex possible as the filler joint is quite thick as opposed to your joint which is to the hull stub. I will send the photos to Ralph, I tried the phone but the answer machine cut in. I presume they are not open until after next weekend?
Regards Ben
 
benw said:
Thanks, I have posted a few photos on our blog
Http://orcanasigma38.wordpress.com
I must admit I was hoping not to have to think about this for a while given the extensive works completed by Foxs. Wondering if I should inform them of my findings? Or am I being naive?
Click to expand...


That does not look bad to me.
The bit of rust at the back probably stems from a chip in the epoxy, perhaps from flotsam or craning strops.
Or maybe there is a porous bit in the casting?
Or just a pinhole in the epoxy?
I think 90+% of boats have worse than this.
Sand it back, phosphoric acid then epoxy it.
 
A flexible sealant such as Sikaflex should have been used to provided a flexible seal. The photos seem to show a non flexible joint?

On mine I cut out a groove about 6 mm wide and 20 to 30 mm deep with a grinder. Epoxy coated the steel then filled the gap with sikaflex. Has been good for 3 years now.
 
HunterWanderer said:
A flexible sealant such as Sikaflex should have been used to provided a flexible seal. The photos seem to show a non flexible joint?

On mine I cut out a groove about 6 mm wide and 20 to 30 mm deep with a grinder. Epoxy coated the steel then filled the gap with sikaflex. Has been good for 3 years now.
Click to expand...
The keel has a flange set within a recess, if you look carefully.Quite different to what you have done
Mine (#4) doesnt & sits flush with the keel stub with a narrow joint
 
Looks to me like the antifouling cracking over the flexible sealant at the joint. As the antifouling dries out it will become more brittle than when afloat. With the boat in a cradle the joint will now also be under compression rather than tension so a lot of force change. Probably inevitable and nothing to worry about.
The rust bubbling through looks like the sort of thing we all hope to avoid when cast iron is blasted but often does. I expect pin holes in the casting trapped salt and moisture despite the best endeavours of the boatyard. Simplest thing is to grind out the affected area and coat with a good layer of zinc rich paint. I wouldn't use a rust converter or epoxy, then antifoul and hope it lasts a few years. The zinc will have a big impact on preventing blistering or undercut into the epoxy.
 
HunterWanderer said:
A flexible sealant such as Sikaflex should have been used to provided a flexible seal. The photos seem to show a non flexible joint?

On mine I cut out a groove about 6 mm wide and 20 to 30 mm deep with a grinder. Epoxy coated the steel then filled the gap with sikaflex. Has been good for 3 years now.
Click to expand...
+1
sailorman said:
The keel has a flange set within a recess, if you look carefully.Quite different to what you have done
Mine (#4) doesnt & sits flush with the keel stub with a narrow joint
Click to expand...
Then you should not tolerate any movement.IMHO
 
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The compressive force of the bolts holding the keel to the hull is vast by comparison with anything the sealant/adhesive can provide. Provided the bolts are fully tightened, and assuming adequate construction of the boat in this area, then water will not penetrate as far as the bolts. However, some hulls can flex very slightly under heeling loads and when the keel is hanging from it, rather than supporting it on the hard. A small amount of cracking and rust close to the join is almost inevitable and harmless. Applying sealant with the boat on the hard is close to a waste of time unless the sealant has high strength and flexibility. Doing the same thing with the boat hanging in the slings might perhaps be better.
 
vyv_cox said:
The compressive force of the bolts holding the keel to the hull is vast by comparison with anything the sealant/adhesive can provide. Provided the bolts are fully tightened, and assuming adequate construction of the boat in this area, then water will not penetrate as far as the bolts. However, some hulls can flex very slightly under heeling loads and when the keel is hanging from it, rather than supporting it on the hard. A small amount of cracking and rust close to the join is almost inevitable and harmless. Applying sealant with the boat on the hard is close to a waste of time unless the sealant has high strength and flexibility. Doing the same thing with the boat hanging in the slings might perhaps be better.
Click to expand...
Agreed, some hulls can flex significantly differently when floating/lifted in slings and when sitting on keel ashore. Not just lightweight modern boats, but many ultra-respectable and extremely seaworthy 1970s/80s fin and skeg cruiser-racers.
 
I have had some reassurance from the Sigma 38 association, it seems that this is to be expected and is rectifiable. I plan to make contact with the yard and get their take on it as we spent a fair amount for us on the work completed. I had hoped for a couple pf seasons without having to treat rust given the complete overhaul of the keel ie removal, epoxied new bolts and rebedded.
May be i was being a little naive!
Looking around at other yachts laid up, it seems some fair similarly and typically those that connect close to the hull as opposed to those connecting to a stub. Of course long kelers are spared most of this issue.
I am getting used to a new boat so appreciate the thoughts and comments.
 
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