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Discussion Starter · #1 · (Edited)
old/new - displacement/planing

I had an interesting discussion with Zanshin in the thread: "UK sailors missing after sailboat capsizes 1000 miles east of Cape Cod - Capecodonlin" about the vulnerability of modern racing (and cruising) boats to "to turn turtle and stay inverted for long". As Zanshin expressed himself very appropriately. At the beginning I ignored the fact that Cheeki Rafiki had lost her keel and I had made the supposition that she had capsized due to the strong wind and had stayed like that because of her width and shape. I had the idea that old boats (about prior of 1990) had a better capacity of self-righting and that this feature could be defective in modern planning boats.

Zanshin reassured me saying that all the "Modern production boats still have to prove that they are self-righting, otherwise they will not get certified." This on one hand settles the matter but on the other hand - thinking about what occurred to Cheeki Rafiki and other racing boats too - it remains open the question whether modern designs and light displacement boats are somehow too week to face really hard sea and wind conditions.

One hears now and then of recent models where not everything is strong enough and there are people who swear that old boats were much more seaworthy. Is that a myth or there is some truth in it?

I have to confess that if I had to change my boat (an old Contest) I'd not know what to buy among the modern production.

I'd like to hear ideas and opinions about this comparison between old/new and displacement vs planing boats.

Thanks,
D.
 

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grumpy old man
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I would start by saying be careful before you lump all "modern production boats" into one box in so far as structural strength is concerned. I like to look at each boat as an individual.
Halberg-Rassy's are modern production boats as are Beneteaus but they have almost nothing in common.
 

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Discussion Starter · #3 ·
Re: old/new - displacement/planing

You are absolutely right Bob,

I touched that point in my previous post in the other thread (before moving here). Cheeki Rafiki, the unfortunate boat which lost her keel in a storm in Atlantic, was a Beneteau. I never heard so far of a Swan (just to stay with racing boats) which lost her keel.

But my focus here was more on the shape or design of the more recent models: most of them, even the cruising ones are planing boats, with a very wide beam, and a flat hull. Actually they resemble very much a dinghy. Having sailed on dinghies quite a bit in my youth I know how difficult is to straighten them once capsized. I wonder whether these modern cruising/racing boats have that same behaviour...

So my question is how seaworthy are these modern designs?
 

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When it comes to the technical aspects of boats, my favorite reading and reference book is "Principles of YACHT DESIGN" by Larsson & Eiliasson. It contains a vast amount of information in text and formulas which go a long way in explaining why certain aspects of boats are built the way they are.
Each production boat is built for a certain market segment and this determines many of the factors. While there are RCD and similar directives specifying minimums it doesn't mean that it is wise to go offshore in a boat that just barely satisfies those minimums.

But the original discussion was the righting moment and an assertion that many modern production boat designs are stable when inverted. Perhaps Bob might add his comments on that.
 

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grumpy old man
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Here is what I think:
In any sea condition rough enough to contribute to a boat rolling over I can't imagine it staying inverted so long as the keel stayed attached. It doesn't take much of a heel angle to start the Rm from climbing again if the VCG is where it was intended to be. Perhaps min an extreme i.e. very wide and very light and very flat hull form this could happen but you are not going to find these proportions on typical production models. To stay stable in an inverted position the VCG and CB must stay in perfect alignment. Hard for this to happen with any sea running. Maybe someone can fish up a photo of a "normal" production boat inverted and stable with the keel still on. I don't think I can.
 

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I recently got a good close look at a Volvo 70 ("Monster Project") in Antigua at the dock and also while sailing and I can imagine that this hull might stay inverted, the keel is hydraulic and might cant enough to force the very wide and flat hull back over but I'm not sure that it will. Apart from that type of specialty racer I think that even full inverted the conditions that caused the inversion would also force the boat to return to whatever the AVS was and re-right the boat. It might take longer than for a "classic" hull form but it will come back.
 

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Armchair Horn Sailor
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I recently got a good close look at a Volvo 70 ("Monster Project") in Antigua at the dock and also while sailing and I can imagine that this hull might stay inverted, the keel is hydraulic and might cant enough to force the very wide and flat hull back over but I'm not sure that it will. Apart from that type of specialty racer I think that even full inverted the conditions that caused the inversion would also force the boat to return to whatever the AVS was and re-right the boat. It might take longer than for a "classic" hull form but it will come back.
I could be wrong but I thought the open class race boats had to prove they are self righting in FLAT water using their canting keel.....

Sent from my SM-N900V using Tapatalk
 

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I could be wrong but I thought the open class race boats had to prove they are self righting in FLAT water using their canting keel.....

Sent from my SM-N900V using Tapatalk
They do. They actually flip them over in a marina with a crane and test them that way. With the keels canting to 40 degrees it isn't that hard to flip these things back over. For most of the boats they are still pretty far from their maximum can't before the boats flip back over. It also only takes a minute or two to happen.

is a good example of the test being done. The boat is fully inverted at 2:16 and is back upright at 2:54.
 

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Bombay Explorer 44
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Wow I did not know they could do that self righting thing.

Two questions spring to mind.

If perchance the rig was still on would it still self right?

Is the cant to one side automatic when upside down or does some lucky soul get dive under to press the button.
 

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What I have noticed over the past few years is that it is not at all unusual for keels to fall off nowadays.

Prior to Drum losing its keel in the 80's I had never heard of it happening other than in severe grounding/beaching. Even in Drum's case it was due to bad casting practice - they didn't "J" the bolts and the huge mass of lead simply slid off the bolts - it didn't fail due to being under-engineered like they seem to do now.

The massive S/S floors that the Maestro put in Francis Lee should do the trick for a long, bulbed, razor blade keel like that :D but most boats seem to have little more backing than older style keels with their much greater mating surface.

It happens so frequently now that you'd think the message would have gotten through.
 

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What I have noticed over the past few years is that it is not at all unusual for keels to fall off nowadays.

Prior to Drum losing its keel in the 80's I had never heard of it happening other than in severe grounding/beaching. Even in Drum's case it was due to bad casting practice - they didn't "J" the bolts and the huge mass of lead simply slid off the bolts - it didn't fail due to being under-engineered like they seem to do now.

The massive S/S floors that the Maestro put in Francis Lee should do the trick for a long, bulbed, razor blade keel like that :D but most boats seem to have little more backing than older style keels with their much greater mating surface.

It happens so frequently now that you'd think the message would have gotten through.
Ya years ago you never heard of keels falling off, simply because you never heard of boats again. They just sailed off into the sunset and were never heard from again.

The concept that yacht designers today are making boats that are less safe than those build fifty years ago is ludicrous. The difference is that today we have EPIRBS, long range radios, sat phones and the internet, so when it does happen everyone knows about it.
 

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Here is what I think:
In any sea condition rough enough to contribute to a boat rolling over I can't imagine it staying inverted so long as the keel stayed attached.
,,,
Which apparently was not the case and the keel was lost along with ...
 

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No, I don't think it is; the original question was certainly not and we shouldn't let this topic degrade, either. The topic is not whether keels fall off more these days and whether this is due to bad engineering or better reporting.

But perhaps the topic is closed, as the consensus is that design on modern production hulls, with their large amounts of volume and flat, wide sections still includes the design requirement to self-right in the case of a knockdown or roll - even though they look like they would be stable inverted.
 

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One of None
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the "test" vid is without the standing rigging and mast/s I may not an expert but a test without the rigging seems like it was just being done for the spectators.
 

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grumpy old man
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At 90 degrees the angle of the can't i.e. to port or starboard should not change the VCG. But that's only at 90 degs. I think it would be best to have the keel on centerline. That would give you the "lowest" VCG. I don't much much faith in stability tests done in a yacht basin in flat water. What this test tells you is: with no rig in this boat, no crew, no wind and no waves the boat will right itself from a 90 degree heel angle. To me this does not replicate real world conditions where a boat would be knocked down. But, I suppose it's better than nothing.
 

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Maybe someone can fish up a photo of a "normal" production boat inverted and stable with the keel still on. I don't think I can.
Bob, this isn't really a normal production boat. It is Wingnuts from the Chicago Mac race disaster. It was inverted in a strong thunderstorm. The wings on the hull probably helped to flip it. Then after the storm passed, the sea state was not high enough to flip it back. (the thing on the keel bulb is a light the CG put on so other ships don't run it down)

 

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Bob,

The starting conditions for the test are two crew on board, the keel pinned at centerline, and the mast removed.

The assumption is that in a full roll the mast would likely be lost anyway. To successfully complete the test the single crew member has to manually cant the keel over, and right the boat (I think in under a minute).

While it would be a more valuable test to do so with the rig in place, the chance of loosing a million dollar rig is just to high.

Since these tests have been done no IMOCA has had a problem self righting so long as the keel remains attached. But they do have a habit of loosing their keels. But these things are far from the type of ballast you would find on even a production racing boat (as I type this I feel like I am trying to teach grandma to suck eggs). They are using engineering tolerances of 1.5-2 times the expected load, which would be criminal on any boat other than extreme machines.
 

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Bob, this isn't really a normal production boat. It is Wingnuts from the Chicago Mac race disaster. It was inverted in a strong thunderstorm. The wings on the hull probably helped to flip it. Then after the storm passed, the sea state was not high enough to flip it back. (the thing on the keel bulb is a light the CG put on so other ships don't run it down)
I don't think I would call a Kiwi 35 a 'normal' production boat. I raced on one, and while a lot of fun, is a pretty weird design, and so tippy you have to board from the bow since if you step on the wing the boat rolls.
 
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