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Old 13-12-2015, 04:01   #406
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Re: Oyster Problems?

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Originally Posted by jmaja View Post
If you compare current Swan models and Oyster models, 825 seems to be very heavy and some other Oyster are much lighter.

Oyster 825: LWL 21.97 m, beam 6.31 m, draft 3.42 m, displacement 56 tonnes
Swan 80: LWL 22.19 m, beam 6.08, draft 4.0, displacement 36 tonnes

Oyster is almost 60% heavier.

Oyster 625: LWL 17.24 m, beam 5.44 m, draft 2.8 m, displacement 33.5 tonnes.

Swan 66: LWL 17.19 m, beam 5.39 m, draft 3.0 m, displacement 30 tonnes

Oyster is only 12% heavier.

Oyster 545: LWL 14.1 m, beam 4.75 m, draft 2.4 m, displacement 21.3 tonnes

Swan 54: LWL 14.4 m, beam 4.75 m, draft 2.44 m, displacement 22 tonnes

Oyster is 3% lighter.

So it seems that for Swans DLR decreases much more rapidly with inceasing size than for Oysters. Partly that is due to increased used of carbon (no carbon in 54, some in 66, a lot in 80).

If you see lightness as the cause of problem, then there are other Oyster models that should have the same or worse problem.
That is an interesting point even if, as you point out, we cannot compare the swan 80 in what regards building techniques and materials with the others swans. The 80 is a carbon boat the others are not and regarding Oyster all recent boats were made the same way using the same materials.
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Old 13-12-2015, 06:00   #407
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Re: Oyster Problems?

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Originally Posted by Muckle Flugga View Post
I would like to add a note concerning the debate regarding grounding. Grounding is not the only source of impulse to a yacht keel that can be considered to be structurally significant in weak designs. Collisions with submerged objects are at least as significant if not more so and signally occur without the slightest warning, seamanship being completely out of the equation as a factor. Further, they commonly occur far offshore where a vessel must perforce sail on hundreds or thousands of miles to ensure the safety and survival of the crew. A great deal of air has been expended elswehere on the subject of containers. I am somewhat sanguine about the true prevalence of this risk, however in such an encounter the forces would be comparable to hitting solid rock at hull speed. Whatever the true risk of container strike, whale strikes are indeed common, and the forces imparted by the tail of a startled and panic diving whale can far exceed a hull speed collision with rock. Collision with semisubmerged logs, treetrunks, or even large plastic containers at speed will impart immense forces to a keel structure, easily comparable to a hard grounding. Further, it is the case that such impacts commonly occur at maximum hulls speed, which speed is likely to be faster in the more lightly built "cruiser racer" type structures, that indeed Oyster was going for in this poorly thought out design.

Polux in particular has expended a lot of words trying to diminish the commoneness or severity of grounding incidents. What his words in fact do is underscore the danger of collisions with whales and submerged objects for boats whose structures are now admittedly by all and demonstrably severely to fatally weakened by these kinds of impulses. In such circumstances, there is a 100% certainty of hundreds or thousands of miles further strong forces being exerted on the keel before even an effective assessment of the damage such an impact has imparted to these underbuilt, difficult to examine structures.

It is even possible, perhaps even likely, that such an event was what finally wrecked the keel structure of the Cheeki Rafiki. In the MAIB report the following sequence occurs, taken from communications with the craft as the catastrophe began:

"Wednesday 14 May 2014
1014 – email, from Cheeki Rafiki

‘position update at 1000ut 37 00N 052 05W 24hour run 176miles...just hit a big
wave hard and it fixed the stereo.’ [sic]

Thursday 15 May 2014
2022 – email, from Cheeki Rafiki

‘we have been taking on a lot of water yesterday and today. today seems worse i think stbd water tank has split so that is drained checked hull and sea cocks for damage but cant see any. i will go for a swim when weather improves in about 24 hours we are currently monitoring the situation horta is 900 miles away. our position is 38 38N 048 59W any thoughts from your end i will check emails in 2 hours’ [sic]"


It seems to me more than possible that the "big wave" that was hit "hard" was not in fact a wave at all, but something rather more solid.

I know I have hit solid objects hundreds and thousands of miles out to sea in thousands of meters of water. I know many others who have too. How would you feel if you did, in the likes of a 40.7, or else in one of these "new style" Oysters? Could you even be sure that the last wave you just fell off with a bang was really a wave after all? Would you wish you were in fact in an "old style" Oyster?

I know I would!

I doubt very much the solid object theory, why? well I guess the only massive object floating in the oceans are Shipping Containers, if they fall from the top of a wave in one of this containers is Game Over ASAP, then they continue sailing, with the stereo fixed,,, other stuff you can see sometimes floating around is wood logs , driftwoods, but I cant believe they are able to dislodge a keel, long time agoo I bump in a massive piece of wood with my boat with the result of a depth sounder log broken and few scratches in the hull... the 40,7 underbody shape don't like to much to pound to windward or fall of from waves , the Bang is fenomenal and the whole boat suffer ,,,,
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Old 13-12-2015, 06:07   #408
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Re: Oyster Problems?

A yacht is not "like a automobile" when it comes to collision damage. Yachts are intended to safely take their crew on trips where no repair facility or technicians are available during the entire passage. No tow trucks out there either. If there is a design/build of boat that requires inspection/repair immediately after hitting a submerged object then such a yacht should only be sailed a few miles from the nearest inspection/repair facility.
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Old 13-12-2015, 08:43   #409
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Re: Oyster Problems?

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A yacht is not "like a automobile" when it comes to collision damage. Yachts are intended to safely take their crew on trips where no repair facility or technicians are available during the entire passage. No tow trucks out there either. If there is a design/build of boat that requires inspection/repair immediately after hitting a submerged object then such a yacht should only be sailed a few miles from the nearest inspection/repair facility.
Again, I am not defending at all that a keel should be lighten attached to a boat. Just saying that I don't see any reason for a boat to have a keel on a boat that can sustain hard groundings without any damage. Maybe what I call a hard grounding is different from what you call hard groundings.

I call a hard grounding when a boat is stopped net by a rock by a frontal shock when sailing at cruising speed (6/7K). I don't know if there are boats that can sustain that without at least minimal damage but certainly all boats should be deeply surveyed after that and I am quite sure that almost all will need repairs.

Neither I am saying that a boat after having a collision on a keel should not be able to be sailed to safety.

It is vary rare that a boat is sunk after a keel collision. As it was pointed out already the boats that we know that were lost after losing the keel had the keel structure weakened by groundings that occurred many months before and were not properly repaired.

The disagreement here regards having boats that can sustain a hard collision and can be sailed to safety but have to be repaired versus boats that can sustain hard collisions without any need of repair (if that can be possible).

Furthermore very few boats are lost due to keel problems and much more by other reasons. Regarding hitting a container normally the first part to be hit is the forward section of the hull and regarding that if one really wants to be safe and consider that eventuality frequent, the best is to change for a steel hull or at least an aluminum one.

Finally has these pictures of Sydney 38 that ended up thrown big waves to the rocks show:


Even a very light cruiser racer can have a strongly attached keel that certainly suffered not only a hard grounding, but many, till it was thrown over the rocks. The keel was in place and on a movie, that I posted previously, we saw that could still be transported by helicopter without risking falling off and when they landed we could see that could sustain the weight of the boat also without problem.

On this movie you see a very light small French cruiser racer, with the same type of keel, hitting at high speed a big whale in the middle of the Ocean. No problem for the boat or keel that did not need any repair...only for the sailor that hurt is back.

A funny thing, the boat name was "Baleine Blanche" that means white whale
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Old 13-12-2015, 11:54   #410
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Re: Oyster Problems?

Paolo,

You and I will disagree on this. I think a keel should remain in a safe to sail condition if it hits something hard enough to stop the boat when traveling at hull speed. Anything less should not be taken off shore.
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Old 13-12-2015, 12:05   #411
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Re: Oyster Problems?

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Originally Posted by Polux View Post

On this movie you see a very light small French cruiser racer, with the same type of keel, hitting at high speed a big whale in the middle of the Ocean. No problem for the boat or keel that did not need any repair...only for the sailor that hurt is back.

A funny thing, the boat name was "Baleine Blanche" that means white whale
Looks to me it hit on the side, not the keel. Didn't stop the boat.. And that could have been avoided IMHO.
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Old 13-12-2015, 13:11   #412
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Re: Oyster Problems?

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Paolo,

You and I will disagree on this. I think a keel should remain in a safe to sail condition if it hits something hard enough to stop the boat when traveling at hull speed. Anything less should not be taken off shore.
Hum, some confusion here. I thought that I made clear I agree with that. The difference is that some think that the boat should not suffer any damage on the keel or keel structure while I think the boat should remain in a sailing condition that allows it to be brought to a shipyard to be surveyed and properly repaired.

Note that we started talking about hard groundings, that is where keels are damaged and hard groundings happens near the shore, not really offshore.

The possibility of a boat to be damaged offshore by a keel hitting an object with enough force to create damage on that zone is truly remote. It is much easier to damage the hull or the rudders against a container than to damage the keel.

In fact I don't know of a single accident of a boat that sunk because the keel hit offshore an object.

The closest I can get to that regards a case with a racing Open 60 (that did not sunk anyway) that really has nothing to do since the boat was sailing at close 20K, the keel is a canting one, with a draft of 4.5m and that creates completely different efforts on a hull when hitting something solid compared with a yacht with a 2.3m draft boat sailing at 7K, not to mention that a fixed keel can be built more strongly than a canting keel.

Maybe you have more information regarding boats that sunk due to having hitting objects with the keel, I mean that sunk immediately in consequence of that accident. I would like to hear about it.

Note that the cases of the two First 40.7 and a Sweden yacht 42, were the boats sank had to do not with an immediate collision that damaged the keel (and sunk the boat) but with older groundings that damaged the keel, not having been the keel repaired.

On the last case with the First 40.7 the boat crossed the Atlantic with a damaged keel and only sunk at the middle of the return trip. Plenty of time since the groundings that originate the damage that lead to that accident, to repair properly the keel and tightening the keel bolts.
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Old 13-12-2015, 13:30   #413
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Re: Oyster Problems?

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Originally Posted by Polux View Post
Hum, some confusion here. I thought that I made clear I agree with that. The difference is that some think that the boat should not suffer any damage on the keel or keel structure while I think the boat should remain in a sailing condition that allows it to be brought to a shipyard to be surveyed and properly repaired.

Note that we started talking about hard groundings, that is where keels are damaged and hard groundings happens near the shore, not really offshore.

The possibility of a boat to be damaged offshore by a keel hitting an object with enough force to create damage on that zone is truly remote. It is much easier to damage the hull or the rudders against a container than to damage the keel.

In fact I don't know of a single accident of a boat that sunk because the keel hit offshore an object.

The closest I can get to that regards a case with a racing Open 60 (that did not sunk anyway) that really has nothing to do since the boat was sailing at close 20K, the keel is a canting one, with a draft of 4.5m and that creates completely different efforts on a hull when hitting something solid compared with a yacht with a 2.3m draft boat sailing at 7K, not to mention that a fixed keel can be built more strongly than a canting keel.

Maybe you have more information regarding boats that sunk due to having hitting objects with the keel, I mean that sunk immediately in consequence of that accident. I would like to hear about it.

Note that the cases of the two First 40.7 and a Sweden yacht 42, were the boats sank had to do not with an immediate collision that damaged the keel (and sunk the boat) but with older groundings that damaged the keel, not having been the keel repaired.

On the last case with the First 40.7 the boat crossed the Atlantic with a damaged keel and only sunk at the middle of the return trip. Plenty of time since the groundings that originate the damage that lead to that accident, to repair properly the keel and tightening the keel bolts.



Don't know how we got onto hard groundings, as this started with CR which suffered only soft groundings before total keel failure. And as stated many many times, the whole issue is that the type of keel and hull construction you so love cannot be "surveyed and properly repaired" without astronomical expense, vastly more so than traditional forms of construction. It says it right there in the MAIB report. Have you ever repaired a damaged keel of any sort personally?
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Old 13-12-2015, 13:34   #414
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Re: Oyster Problems?

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Originally Posted by Polux View Post
Again, I am not defending at all that a keel should be lighten attached to a boat. Just saying that I don't see any reason for a boat to have a keel on a boat that can sustain hard groundings without any damage. Maybe what I call a hard grounding is different from what you call hard groundings.

I call a hard grounding when a boat is stopped net by a rock by a frontal shock when sailing at cruising speed (6/7K). I don't know if there are boats that can sustain that without at least minimal damage but certainly all boats should be deeply surveyed after that and I am quite sure that almost all will need repairs.

Neither I am saying that a boat after having a collision on a keel should not be able to be sailed to safety.

It is vary rare that a boat is sunk after a keel collision. As it was pointed out already the boats that we know that were lost after losing the keel had the keel structure weakened by groundings that occurred many months before and were not properly repaired.

The disagreement here regards having boats that can sustain a hard collision and can be sailed to safety but have to be repaired versus boats that can sustain hard collisions without any need of repair (if that can be possible).

Furthermore very few boats are lost due to keel problems and much more by other reasons. Regarding hitting a container normally the first part to be hit is the forward section of the hull and regarding that if one really wants to be safe and consider that eventuality frequent, the best is to change for a steel hull or at least an aluminum one.

Finally has these pictures of Sydney 38 that ended up thrown big waves to the rocks show:


Even a very light cruiser racer can have a strongly attached keel that certainly suffered not only a hard grounding, but many, till it was thrown over the rocks. The keel was in place and on a movie, that I posted previously, we saw that could still be transported by helicopter without risking falling off and when they landed we could see that could sustain the weight of the boat also without problem.

On this movie you see a very light small French cruiser racer, with the same type of keel, hitting at high speed a big whale in the middle of the Ocean. No problem for the boat or keel that did not need any repair...only for the sailor that hurt is back.

A funny thing, the boat name was "Baleine Blanche" that means white whale


It's hilarious that you think the fact that the keel is still attached to the boat means anything in this case. It's probably the only part of the boat which is still sound at that point, because that is a cast iron keel. The hull itself is almost certainly toast at this point, and I seriously doubt it is water tight. Just because the boat can be airlifted out without sinking doesn't mean it can sail away without sinking! Because sink it certainly would have if put in the water.


Anyone know if "Low Speed Chase" was repaired and sails again, or was totalled by insurance? I'm guessing the latter.
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Old 13-12-2015, 15:46   #415
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Re: Oyster Problems?

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It's hilarious that you think the fact that the keel is still attached to the boat means anything in this case. It's probably the only part of the boat which is still sound at that point, because that is a cast iron keel. The hull itself is almost certainly toast at this point, and I seriously doubt it is water tight. Just because the boat can be airlifted out without sinking doesn't mean it can sail away without sinking! Because sink it certainly would have if put in the water.


Anyone know if "Low Speed Chase" was repaired and sails again, or was totalled by insurance? I'm guessing the latter.

I do like the name.


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Old 13-12-2015, 16:45   #416
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Re: Oyster Problems?

I doubt its sailing again, probably the amount of cash to fix it can surpass the boat value .... I gues the hull side resting in the rocks is holed , etc....
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Old 13-12-2015, 17:09   #417
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Re: Oyster Problems?

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I doubt its sailing again, probably the amount of cash to fix it can surpass the boat value .... I gues the hull side resting in the rocks is holed , etc....
Yes, plus rudder is gone.


This brings us to the original point of these conversations. If the boat is cheap to buy, but expensive to diagnose let alone repair, it'll be a throw away every time.
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Old 13-12-2015, 19:24   #418
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Re: Oyster Problems?

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I doubt its sailing again, probably the amount of cash to fix it can surpass the boat value .... I gues the hull side resting in the rocks is holed , etc....
Well, one thing is for sure, that Sydney 38 keel and hull after being rammed by heavy seas against rocks and thrown to a rocky island is in much better shape than the one of the Oyster that did not ground neither touch any rock, and by the way the rudder is only half broken (only the spade).

"Despite being thrown up on the rocks, there was relatively little damage to the hull of Low Speed Chase.

There were about 257 waves an hour at the Farallones. Given the forecast, it would be expected that two to three waves would have been over 30 feet high. Low Speed Chase was in 28 feet of water when she was hit. A 30-ft wave would easily break in 28 feet of water, as the rule of thumb is that waves break in water 1.3 times their height."

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Old 13-12-2015, 19:33   #419
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Re: Oyster Problems?

food for thought ..... The perfect racing machine would disintegrate as it crossed the finish line.
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Old 13-12-2015, 21:38   #420
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Re: Oyster Problems?

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Well, one thing is for sure, that Sydney 38 keel and hull after being rammed by heavy seas against rocks and thrown to a rocky island is in much better shape than the one of the Oyster that did not ground neither touch any rock, and by the way the rudder is only half broken (only the spade).

"Despite being thrown up on the rocks, there was relatively little damage to the hull of Low Speed Chase.

There were about 257 waves an hour at the Farallones. Given the forecast, it would be expected that two to three waves would have been over 30 feet high. Low Speed Chase was in 28 feet of water when she was hit. A 30-ft wave would easily break in 28 feet of water, as the rule of thumb is that waves break in water 1.3 times their height."

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So was she repaired or not? I count at least 5 holes in the hull on the port side, some quite large.
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