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Old 25-05-2014, 04:27   #31
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Re: Cheeki Rafiki

My view of the world is that keels should not fall off, period! I'll add a caveat to that statement..if they do fall off they should take half the bottom of the boat with them. I don't care if its a prior grounding or a whale kissing you, keels should not fall off. The concept of accepting that ya it happens... a few this year and a couple next year but hey we build hundreds of them that don't.. If the airline industry operated that way no one would get on an aircraft. Keels can be designed in such a way that they don't fall off but it costs a few bucks and they would not go upwind quite as high or as fast as the current crop of racer cruisers.
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Old 25-05-2014, 06:37   #32
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Re: Cheeki Rafiki

Well the keel fix is simple. Drill a hole through the keel and thread a 3/4" line of Dyneema through it. Tie the ends off port and starboard or run it up as a backup stays to the mast. Probably only lose about a knot of boat speed but, you'll sleep better in the storm.
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Old 25-05-2014, 07:05   #33
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Re: Cheeki Rafiki

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Originally Posted by WindLove View Post
We're you sober when you came up with that plan?
What can I say I'm just an "idea" kind of guy.
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Old 25-05-2014, 07:31   #34
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Re: Cheeki Rafiki

Does anyone know if there are plans to recover / salvage the boat ? The last I know is that the USCG did not, as a policy recover lost boats, and it was to my knowledge, left floating upturned, as a potential hazard for other vessels.
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Old 25-05-2014, 07:55   #35
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Re: Cheeki Rafiki

Quote:
Originally Posted by mbianka View Post
Well the keel fix is simple. Drill a hole through the keel and thread a 3/4" line of Dyneema through it. Tie the ends off port and starboard or run it up as a backup stays to the mast. Probably only lose about a knot of boat speed but, you'll sleep better in the storm.

Brilliant! Keeps the mast attached too!

Unless you loose your keel and mast at the same time... And I am sure Beneteaus have been designed to jettison both at an unexpected time just after factory warrantee runs out. Bastards that company! They even put goo in the fuel tank, dog poop in the water tanks and the set the compass 37 degrees off! Bastards!



Mark
PS Would 3/4 inch Dyneema have a higher SWL than a SS keel bolt? Gotta be close.
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Old 25-05-2014, 08:23   #36
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Re: Cheeki Rafiki

I think Beneteau should take this opportunity to design the first 10 year/100000 nm unlimited warranty on a sailboat's drive train...sails/engine/keel/standing rigging/running rigging/winches./sarc off

Whatever happened to taking responsibility for the maintenance on your own boat?

We all know systems degrade with wear and should know performance limits of our boats. Our maintenance schedules take that into account...if the inspection or scheduled replacement of keel bolts is 'too hard' that is a way of saying you are accepting the risks of not doing it. Same with not lowering the rig to do maintenance and inspections from time to time.

That said...we don't know that sequential failure of the keel bolts of Cheeki were what caused her loss. The photos show corrosion but we don't know that they corroded to failure. We know she had leakage and we know she eventually lost her keel. We don't know that she didn't hit a partially submerged object with her keel.
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Old 25-05-2014, 08:37   #37
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Re: Cheeki Rafiki

Seriously, do you think a 10 yr old boat should need new keelbolts?Sounds like a design flaw to me,barring a collision with something hard(not waves).
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Old 25-05-2014, 08:48   #38
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Re: Cheeki Rafiki

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Originally Posted by MarkJ View Post
Brilliant! Keeps the mast attached too!

Unless you loose your keel and mast at the same time... And I am sure Beneteaus have been designed to jettison both at an unexpected time just after factory warrantee runs out. Bastards that company! They even put goo in the fuel tank, dog poop in the water tanks and the set the compass 37 degrees off! Bastards!



Mark
PS Would 3/4 inch Dyneema have a higher SWL than a SS keel bolt? Gotta be close.
3/4" Dyneema has RBS (breaking strength spliced) of 63,300 lbs. Think it could hold most keels up.

Another idea just came to me. Roller furlings on the keel securing Dyneema.
Two benefits:
1) Allow the boat to take advantage the underwater currents especially when the winds are light.

2) Use as a drogue in heavy seas. None of that trailing lines behind the boat business and would also provide anti surfing protection in steep seas.

Amazing, usually I only come up with ideas like this after a few beers in the cockpit. Now where is that Patent office information.
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Old 25-05-2014, 08:50   #39
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Re: Cheeki Rafiki

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Originally Posted by MarkJ View Post
Would 3/4 inch Dyneema have a higher SWL than a SS keel bolt? Gotta be close.



I believe the SS keel bolts in this case are M28. So, taking a standard material factor of 1.15, and a 0.2% offset yield for the AISI316 as 355MPa.

Then the permissible yield strength (not ultimate tensile strength) of a single M28 bolt would be:

(PI/4)*(28^2)*(355/1.15) = 189555N... 19322Kg

However, we cannot compare yield strengths directly as Dyneema doesn't have one (too stretchy) so we cam compare Ultimate tensile strengths (break point).

A typical AISI316 stainless would have a UTS of 550MPa. The best Dyneema is up in 2800MPa.

The breaking load require for the M28 would be:

(PI/4)*(28^2)*550=338493N (34500Kg)

The breaking load of the 3/4" dyneema would be:

(PI*4)/((0.75*25.4)^2)*2800=712916N (72560Kg)

It looks like Dyneema has it, but remember that this is comparing one dyneema line to only one keel bolt. Obviously there's more than one keel bolt.

Another thing not considered here is that the yield strength of the cast iron in the keel is only around 130MPa as opposed to the 355Mpa of the SS. It's more likely that the threads in the keel.would shear before the SS bolts.

This calculation is also straight tensile and doesn't account for moments, shear etc on the keel bolts nor directionality of the dyneema line.

Just thought somebody might be interested!
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Old 25-05-2014, 09:14   #40
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Re: Cheeki Rafiki

I am of the school that a keel shouldn't fall off the boat, regardless the possible impact with whales, containers, etc. It should be designed to handle whatever stress the lever arm calculated amount might be.

If an exceedingly narrow fin is necessary, why not extend the keel up into the hull where it could widen and perhaps be bolted to a carrier just below the sole? Or maybe broaden the attachment point to the underside of the hull which could be faired into the hull itself, with keel bolts widely spaced athwartships, still accessible in the bilge?

I think that must be numerous ways to attach a narrow foil that has more structural integrity than the current method be used bu Beneteau and many other builders. My sense is that they are taking the least costly approach to this issue, and then expecting the keel attachment to be a maintenance issue for the owner. Really?
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Old 25-05-2014, 09:18   #41
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Re: Cheeki Rafiki

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My sense is that they are taking the least costly approach to this issue, and then expecting the keel attachment to be a maintenance issue for the owner. Really?
Then don't buy their boat. Lots of reasons to buy a boat and to not buy a boat but if one is concerned about the keel being under-designed or too maintenance-intensive seems these should be high on the list.
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Old 25-05-2014, 09:19   #42
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Re: Cheeki Rafiki

Nothing better than cold science to kill a thread full of nonsense. Nice job.

Sent from my XT1030 using Cruisers Sailing Forum mobile app
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Old 25-05-2014, 09:31   #43
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Re: Cheeki Rafiki

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Then don't buy their boat. Lots of reasons to buy a boat and to not buy a boat but if one is concerned about the keel being under-designed or too maintenance-intensive seems these should be high on the list.


+1.. My Bene's coming up to 15years old. She was out of the water last week for a bottom job and the caulked joint between the hull and keel showed no signs of seepage. The internal boltheads and washers are immaculate. I still plan on replacing the keelbolts (one at a time) while in the water in the next couple of years. On any fin keel, you can't be 100% sure what lingers below without looking, and the only way to really look is to disassemble.

If including keelbolt replacement in the long term preventative maintenance schedule is something that seems sensible, then its something I'm willing to do.

I could have spent an additional $300k on a similar sized vessel and still feel the need to replace the bolts after 15years!
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Old 25-05-2014, 09:41   #44
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Re: Cheeki Rafiki

Quote:
Originally Posted by mbianka View Post
3/4" Dyneema has RBS (breaking strength spliced) of 63,300 lbs. Think it could hold most keels up.

Another idea just came to me. Roller furlings on the keel securing Dyneema.
Two benefits:
1) Allow the boat to take advantage the underwater currents especially when the winds are light.

2) Use as a drogue in heavy seas. None of that trailing lines behind the boat business and would also provide anti surfing protection in steep seas.

Amazing, usually I only come up with ideas like this after a few beers in the cockpit. Now where is that Patent office information.
Do you have a good idea about dealing with the dyneema fouling the prop.
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Old 25-05-2014, 09:53   #45
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Re: Cheeki Rafiki

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Do you have a good idea about dealing with the dyneema fouling the prop.


What if the prop was dyneema too?
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