tokolosh

Hobie 33 Keel questions

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I’m hoping someone can help with a couple of questions regarding the Hobie 33 retractable keel and single point lifting.

 

  1. I want to be able to lift my Hobie 33 using a single point lift system as described in the owners manual. My boat did not include this lifting rod. I can find no specifications for the lifting rod. I assume it must be a 5/8” rod to connect to the replaced 5/8” bolt on the aft keel plate using a coupler. When I showed this to a couple of metal fab shops, they doubted it could safely lift the approx. 4500 lbs. Is the rod high tensile stainless or similar. Is the coupler a custom or standard off the shelf item?

 

  1. The other thing is that I removed the aft keel plate thinking that I’d replace the 5/8” stainless bolts that are likely original 1980’s stock. Having done this, I discovered that there is only solid fibreglass that the bolts go through and no metal reinforcing. Which means that the single point lifting system relies on a single 5/8” bolt attached to only fibreglass in the keel to lift the whole boat!!? This feels scary or am I missing something here?

 

Does anyone have details of the keel construction, an un-needed single point lifting system or any additional wisdom?

Keel bolt coupling.jpg

Edited by tokolosh
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The Hobie designers very likely figured it out as safe. Have Hobie 33 owners been experiencing failures....doubt it.

A 5/8” bolt in continuous hard service, like a truck frame or bridge, will indeed have a fairly low working load limit. However on this sort of part, which is readily inspected, not subject to continuous vibration, corrosion, etc. it will be plenty strong. I would have it made from some higher grade steel, not farmer or Home Depot shit. Likewise the threaded parts. More to prevent cracking than high ultimate strength.

No issue with the fiberglass. That looks like plenty. Again, the designers and long history must be given some weight.

Is the rod somehow constrained from bending stress? Does it go thru a hole in the deck or something. Bending stress at the threads would be bad.

I prefer nylon hoist pendants. They store better. Don’t corrode. Bend eithout complaint. And greatly reduce shock loads.

The COG of a boat is rarely over a keel bolt. There is likely more to the lifting system?

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Thanks El, I hear what you say about the designers figuring it out at the design stage, and it obviously has been done.

 The rod is constrained at the coachroof level just aft ot the sliding companionway hatch. (see attached), so no bending stress. I was leaning towards using a rope pennant (Dyneema?) if I can attach it securely to an adequate coupler. The pivot point is correct over this attachment according to the manual and the (rare) picture I have seen of Hobies hanging by the single point.

It was when I cleaned out the bolt hole in the top of the keel and only found fibreglass that I decided to pause and reach out for advice from the forum. Any Hobie 33 owners out there with experience/comments?

H33 lifting procedure.jpg

H33 Lifting profile.jpg

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The hoist in our marina had a brutal start/stop snap. I liked my 3/4” nylon lifting strop that had a few inches of stretch. Though it went to a welded eye on the keel backing plate. I had a (comparable) 11:Metre...raced against Hobie 33s. Had to run lines aft from the eye to hold the bow down and the rig away from the hoist winch. The whole bridle clipped on in seconds. Took a while to perfect but worked great. But your pictured system looks fine, too. Hope some 33 owners chime in.

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The metal shop is smoking crack.

A36 steel has a minimum yield strength of 36000 PSI. Your 5/8 rod is 0.30in2.  0.3 x 36000 is 11000 pounds. So you have a safety factor of 2.5 with common steel.

You can get high strength steels in many grades with yield strengths up to 80000 PSI, which gives you a safety factor of 5.5. Choose the safety factor you want and pick the steel that give you that result.

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17 minutes ago, Moonduster said:

The metal shop is smoking crack.

A36 steel has a minimum yield strength of 36000 PSI. Your 5/8 rod is 0.30in2.  0.3 x 36000 is 11000 pounds. So you have a safety factor of 2.5 with common steel.

You can get high strength steels in many grades with yield strengths up to 80000 PSI, which gives you a safety factor of 5.5. Choose the safety factor you want and pick the steel that give you that result.

No need to get anything of higher strength than the stud though, right.

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No need to get anything of higher strength than the stud though, right.

Generally no, but then it may not be possible to figure out exactly what the keel bolts are.The keel bolts are probably (hopefully?) stainless. 316 has a yield strength of 42000PSI. Other alloys vary quite a bit.
I'd also go a bit higher on the safety factor of the lifting bar because it's likely to be abused over its life and may well be subjected to bending when lifting. 
 

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Thanks all for the replies. Yes, the total weight is 4000-4500 with gear etc. With the load capabilities of the 5/8" steel rod/bolt being laid to rest, I am left with the nagging concern of the strength of the fibreglass layup of the rudder where the lifting rod attaches. Thanks for the link to the Hobie 33 Facebook page. I'm waiting for approval to join and will look for further info there. 

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3 hours ago, tokolosh said:

Thanks all for the replies. Yes, the total weight is 4000-4500 with gear etc. With the load capabilities of the 5/8" steel rod/bolt being laid to rest, I am left with the nagging concern of the strength of the fibreglass layup of the rudder where the lifting rod attaches. Thanks for the link to the Hobie 33 Facebook page. I'm waiting for approval to join and will look for further info there. 

Are you worried about some particular flaw in your boat, or that Hobie got it wrong with respect to the design and that is about to show up for the first time now with yours? Hobie 33's have been around and sailed hard for a long time, and they always struck me as particularly well constructed boats. I trusted ours as I single-handed it from Newport to Bermuda a number of times, and never worried about the boat letting me down. Having said that, I never actually lifted ours by the steel rod as I didn't need to and didn't have all the pieces, but would have done so without worrying about the boat. I would have worried about me doing something wrong, not getting the balance right, the crane operator making a mistake, general conditions and fatigue/damage in the lifting rod, but not the boat's construction. Just my 2 cents.

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4 hours ago, Mark Morwood said:

Are you worried about some particular flaw in your boat, or that Hobie got it wrong with respect to the design and that is about to show up for the first time now with yours? Hobie 33's have been around and sailed hard for a long time, and they always struck me as particularly well constructed boats. I trusted ours as I single-handed it from Newport to Bermuda a number of times, and never worried about the boat letting me down. Having said that, I never actually lifted ours by the steel rod as I didn't need to and didn't have all the pieces, but would have done so without worrying about the boat. I would have worried about me doing something wrong, not getting the balance right, the crane operator making a mistake, general conditions and fatigue/damage in the lifting rod, but not the boat's construction. Just my 2 cents.

Thanks Mark. I too have been impressed with the overall build quality and strength of the Hobie. I have sailed mine to Hawaii from the west coast. For that trip I built a rudder with a solid one piece shaft, as the two piece rudder shaft is notorious for failure. I have only used slings/travel-lift before, but wanted to be able to take advantage of the single point lifting, hence my looking into it. I suspect that few Hobies ever did use this method. as I said before, it was only after removing the bolt from the forward keel bracket that I began to question just how strong this section of the keel was, as it has to withstand the entire weight of the boat including the keel. The bracket that lifts just the keel (50% of total weight) appears to be bolted to metal in the keel. And there are documented cases of this failing and causing the keel to drop. There is no particular known flaw with my own boat.

I guess what I'm looking for is information that reassures me a bit more. Thanks for your input.

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These boats are about 35 years old now so regardless of how well they were designed and built, that's a lot of time to deteriorate and sustain any abuse from different owners.

The retractable keels on the Hobies have a gasket at the bottom that is most likely worn by now, allowing water into the trunk. Some of these keel bolts have been sitting in water for very long periods of time (years in some cases). I would not trust these bolts to be of any source for a single point lift.

 

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Here I am getting all nervous lifting my 2400lb boat off of two 1/2” keel bolts...

Is that a stainless plate acting as a backplate for the aft keel bolts?

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Will, yes that is a heavy stainless plate.

Irrational, Yes I hear your concerns. I am looking at using slings and spreader bars for a gantry crane lift now. 

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Can that plate be removed and modified to have a lifting eye welded to it? I’m no engineer but it would then be lifting off of two keel bolts instead of one, right?

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