Keel Bolts - a bad idea

[fireball]

Number of Keel bolts is PROBABLY DOWN to say three of four ...

Ok - so we are doing armchair engineering here ... can you tell us which it is ... 3 or 4 ... and what size the bolts are ? If they're M5's I'd get off the boat now ... if they're sized properly then it isn't nescersarily an issue.

 

[Tranona]

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If keel bolts fail, this instantly puts the lives of crews in danger. The method of attaching the keel to the hull can be improved easily, as I have described above, and I am sure there are other options. There's no excuse.

Whilst that may be the case - the small number of keels falling off - all on racing boats - have not been failures of bolts. The failures have either been in the composite structure of the keel itself or the supporting framework within the hull. Designers are aware of the loads and the standards for production yacht construction are generally speaking are very conservative. Designs need to meet the standards to comply with the RCD (altough not on racing yachts).

I expect the boat your son is racing on has a framework inside the hull that takes the keel and rig loadings and the actual hull moulding is only there to provide the boat shape and keep the water out!

BTW if you are really interested in the subject, do a bit of research and you will find there is an ISO or American Bureau of Shipping standard which lays down design parameters for keel structures.

 

[Quandary]

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If you have a long keel with plenty of keel bolts - no problem. That's fine, but my son sails on a 40 footer where the length of the keel is about 750mm, the height is about 2 metres, it is very thin, and has a ballast weight at the bottom. Not untypical for a modern recing yacht. This means that the number of keel bolts is probably down to say three or four - increasing the tension in the bolts and the likelihood of failure.

If keel bolts fail, this instantly puts the lives of crews in danger. The method of attaching the keel to the hull can be improved easily, as I have described above, and I am sure there are other options. There's no excuse.

If your son is sailing on a boat with the keel you describe it would have turned over by now.
I suggest you ask him to look at the keel bolts the next time he goes aboard before putting on his lifejacket, he perhaps could take a photo for you. Many thousands of high performance boats have deep slim profile lead keels with large bulbs at the bottom, most extend forward and aft at the attachment to increase the contact area. Even mine is like that. But the makers know it must be effectively engineered. I suspect the greatest potential risk is below the bolts where the unstiffened soft lead alloy fin is at its shortest and narrowest. Boats with these keels have sailed for years as racers and cruisers without mishap. Cutting edge stuff is usually intensively engineered while the run of the mill is more at risk of complacency.
I like your solution,(except for the loss of headroom),but from your point of view its just a pity there is not a problem!

 

[snowleopard]

I have drawn up a sample keel, which I hope you can see.

Sorry, I think you've missed the point. Either of your arrangements will work fine as long as the bolts are correctly sized BUT the bit that's most likely to give is the bit you have disregarded in your analysis i.e. the hull. What really counts is how closely the hull meets the keel, how thick its laminations are and how well the load is spread over the surrounding structure. As you have drawn it, the keel would flap around like grandma's washing in a breeze.