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Alessiocannoni · 25-11-2015, 23:49

Quote:

Originally Posted by Polux

It seems to me that the failure here as to do not with the keel falling of from a structure but with the hull not being able to deal with the forces transmitted by the keel to the hull and supporting structure. I understand now what Oyster was saying with “suffered a serious incident which compromised the moulded hull”.

The keel fall due to the compromised hull. That compromise can be due to an insufficient distribution of the generated keel forces by the hull (or the hull not being strong enough) and regarding to that I am impressed with the failure of two stringers that were laminated to the hull (look at the 885 hull and look for them on the wreck). Off course that can mean, or probably mean that they were not strong enough and I raise a question:

This was a 90ft built by increasing a 82ft design. The 90ft obviously weights more and to compensate that in what regards sail power and stability almost for sure the ballast was increased.

They used the same keel structure and the same scantlings that they used on the 825 or the keel structure and all structure and hull of the boat was reinforced to take that extra ballast weight and the bigger forces it would generate?

I suspect the keel is identical and the structure as well, 8 months ago, when I was complaning about the structure because not convinced about the solidity of it, he wrote an email saying something like: don't worry, your boat has the same structure of the other 825, they are very strong! Go ahead with your around the world trip an enjoy your boat......after the accident, to reassure the owner of another 825 in building, the same man wrote to him something like: don't worry about your boat, the structure of Polina Star III was different from the other....
Thay changed version about it so many times that is difficult to say which one is the thruth. Anyways, they are trying to built more then possible in series, immagine that during the building I suggested to change the shape of the keel in order to move forward the center of gravity ( to compensate the weight of the garage), they used the identical keel, then they adjusted the balancement by about 1 Tonn of lead into the bow........one year ago, when I was complaning about that nobody care me..... now that the boat sunk and I show the lead into the bow to the surveyors they are scandalized. Enyway, in a heavy cruising boat like she is, you normally can put so much waight as you want on board....you would kill the performance, but you should not loose the keel. About the other 825: seems they stopped all the boats and they did some reinforcement inside, but as usual, everthing without share the details of their job. I'm in touch only with the owner of Albatross, the other owners or captains did not look for me......I supposed the shipyard convinced them by one of them fantabulous storyes that everything is fine and by" enjoy you boat".......one year ago they did the same with us.......

barnakiel · 26-11-2015, 04:28

Oyster is not Wolksvagen. Different volume will result in (if any) recall being directed to the owners rather than to general public.

Understanding the implied resale value loss no owner of potentially affected hull will ever disclose having received such a recall.

Correct me where I am of the track of market logic.

b.

Polux · 26-11-2015, 05:10

Quote:

Originally Posted by Alessiocannoni

I suspect the keel is identical and the structure as well, 8 months ago, when I was complaning about the structure because not convinced about the solidity of it, he wrote an email saying something like: don't worry, your boat has the same structure of the other 825, they are very strong! Go ahead with your around the world trip an enjoy your boat......after the accident, to reassure the owner of another 825 in building, the same man wrote to him something like: don't worry about your boat, the structure of Polina Star III was different from the other....
Thay changed version about it so many times that is difficult to say which one is the thruth. Anyways, they are trying to built more then possible in series, immagine that during the building I suggested to change the shape of the keel in order to move forward the center of gravity ( to compensate the weight of the garage), they used the identical keel, then they adjusted the balancement by about 1 Tonn of lead into the bow........one year ago, when I was complaning about that nobody care me..... now that the boat sunk and I show the lead into the bow to the surveyors they are scandalized. Enyway, in a heavy cruising boat like she is, you normally can put so much waight as you want on board....you would kill the performance, but you should not loose the keel. About the other 825: seems they stopped all the boats and they did some reinforcement inside, but as usual, everthing without share the details of their job. I'm in touch only with the owner of Albatross, the other owners or captains did not look for me......I supposed the shipyard convinced them by one of them fantabulous storyes that everything is fine and by" enjoy you boat".......one year ago they did the same with us.......

It seems something very wrong went on the building of Polina Star. I don't believe that a good NA like Humphreys would put 1 ton of lead on the bow to compensate the extra weight on the back of the boat. That does not make sense.

Obviously they used integrally the keel structure and support arrangements of the 825 on the extended Polina Star but even so there are ways of changing forward the center of gravity without moving the boat structure, tipping the keel forward and changing the type of keel to one were the bulbed part assumes a different shape and is moved forward.

None of that was made, and I am sure a NA would start from there even if I doubt it would be enough. 1 Ton of lead at the bow is huge in what regards the boat longitudinal balance even on an over 60T boat and deliberating increasing the weight of the boat on the bow or transom is always a bad practice.

It seems clear that the type of keel that was used and the structure was the same (don't know if reinforced) as the one on the 825 but I doubt very much that the weight of ballast would not have been substantially increased to be adjusted to the superior weight of the boat, as well as to the sail area.

Do you know if the sail area was the same as on the 825 or if it was increased?

A Oyster 825, with a hull length of 79'03'' weights 56 000kg and has a sail upwind sail area of 371m2. The new Oyster 885, with a hull length of 85' 6'' weights 74 000kg and a sail area of 448m2.

Note that this difference in displacement does not correspond to a more beamier boat, since the beams are not very different (6.31m to 6.33m) but to a longer boat.

The Polina Star (89'11''ft) was longer than the 885, that even considering LOA has 88'10', and it has to be a considerably heavier boat than the 825.

Assuming that the Polina Star had a similar weight as the 885 and that a ballast ratio of 25% is used that means that for having the same stability characteristics the ballast on the Polina Star had to be increased in 4500kg, more if all is not on the keel and 1T is at the bow.

That means an increase of about 24% in ballast. Using the same structure, even if a reinforced one, for such an increase on the generated efforts seems problematic to me.

Off course I don't know the weight of the Polina Star, having it the same weight of the 825, as I have seen referred, makes not any sense. I don't know also if the ballast was added and how much, but if the boat displacement had increased significantly (and obviously it has) more ballast is needed to give it similar stability characteristics, comparable with other Oysters, namely the 825.

That means also that the 825 keel and keel structure of the 825 may very well be alright and well dimensioned regarding efforts while the structure and the keel of the enlarged 90ft Polina Star can have been clearly undermentioned. Anyway only the results of the expertise will tell what happens.

One way or another there is here clearly a Oyster responsibility, that I hope does not extend to Rob Humphreys (the NA), and the better they can do is to assume it, explain all situation and make amends. It is much better to assume a mistake than casting a veil of suspicion about Oyster design and built quality, one that could endanger greatly the brand reputation and therefore it's commercial success.

Alessiocannoni · 26-11-2015, 05:49

Quote:

Originally Posted by Polux

It seems something very wrong went on the building of Polina Star. I don't believe that a good NA like Humphreys would put 1 ton of lead on the bow to compensate the extra weight on the back of the boat. That does not make sense.

Obviously they used integrally the keel structure and support arrangements of the 825 on the extended Polina Star but even so there are ways of changing forward the center of gravity without moving the boat structure, tipping the keel forward and changing the type of keel to one were the bulbed part assumes a different shape and is moved forward.

None of that was made, and I am sure a NA would start from there even if I doubt it would be enough. 1 Ton of lead at the bow is huge in what regards the boat longitudinal balance even on an over 60T boat and deliberating increasing the weight of the boat on the bow or transom is always a bad practice.

It seems clear that the type of keel that was used and the structure was the same (don't know if reinforced) as the one on the 825 but I doubt very much that the weight of ballast would not have been substantially increased to be adjusted to the superior weight of the boat, as well as to the sail area.

Do you know if the sail area was the same as on the 825 or if it was increased?

A Oyster 825, with a hull length of 79'03'' weights 56 000kg and has a sail upwind sail area of 371m2. The new Oyster 885, with a hull length of 85' 6'' weights 74 000kg and a sail area of 448m2.

Note that this difference in displacement does not correspond to a more beamier boat, since the beams are not very different (6.31m to 6.33m) but to a longer boat.

The Polina Star (89'11''ft) was longer than the 885, that even considering LOA has 88'10', and it has to be a considerably heavier boat than the 825.

Assuming that the Polina Star had a similar weight as the 885 and that a ballast ratio of 25% is used that means that for having the same stability characteristics the ballast on the Polina Star had to be increased in 4500kg, more if all is not on the keel and 1T is at the bow.

That means an increase of about 24% in ballast. Using the same structure, even if a reinforced one, for such an increase on the generated efforts seems problematic to me.

Off course I don't know the weight of the Polina Star, having it the same weight of the 825, as I have seen referred, makes not any sense. I don't know also if the ballast was added and how much, but if the boat displacement had increased significantly (and obviously it has) more ballast is needed to give it similar stability characteristics, comparable with other Oysters, namely the 825.

That means also that the 825 keel and keel structure of the 825 may very well be alright and well dimensioned regarding efforts while the structure and the keel of the enlarged 90ft Polina Star can have been clearly undermentioned. Anyway only the results of the expertise will tell what happens.

One way or another there is here clearly a Oyster responsibility, that I hope does not extend to Rob Humphreys (the NA), and the better they can do is to assume it, explain all situation and make amends. It is much better to assume a mistake than casting a veil of suspicion about Oyster design and built quality, one that could endanger greatly the brand reputation and therefore it's commercial success.

The weight of the boat in cruising conditions (1000 l of fuel and 1000 of water + sails and all the stuff) was 66 Tonn, (I measured by load cells in September in Gosport by load cells because the Oyster didn't do it), the mast 1 m shorter than the n. 1, the main in mast fourling main (don't ask me why please); seems that Rob is not involved in the structures, chooses on the deck hardware, funny way to adjust the boat asset, this aspect seems to be cured by Oyster technical department, I say seems because all their technological and building solution are secrets (fortunately nobody can copy)

Polux · 26-11-2015, 07:20

Quote:

Originally Posted by Alessiocannoni

The weight of the boat in cruising conditions (1000 l of fuel and 1000 of water + sails and all the stuff) was 66 Tonn, (I measured by load cells in September in Gosport by load cells because the Oyster didn't do it), the mast 1 m shorter than the n. 1, the main in mast fourling main (don't ask me why please); seems that Rob is not involved in the structures, chooses on the deck hardware, funny way to adjust the boat asset, this aspect seems to be cured by Oyster technical department, I say seems because all their technological and building solution are secrets (fortunately nobody can copy)

Then it is a completely different story. The Polina Star should weight in lightweight condition something like 62 or 61 tons and that is not much more than the 56Tons of the Oyster 825 and surprisingly much lighter than the smaller 885 that weights 74T. that makes probably the 885 a much stronger boat.

In that case the ballast needed to compensate would be of about 1.5T, a bit less on the keel due to the 1T of ballast on the bow. That means about 10% more ballast on basically the same keel structure. That can be on the origin of the problem but it will make the 825 scantlings not as different as I was supposing on the first approach, even if 10% may make a big difference regarding efforts.

It is worth also pointing out that the D/L of the Polina Star is considerably lower than on other Oysters and that indicates that, if the same materials and building techniques were used (as it was the case), it is a less strong boat, specially considering that the type of hulls and boats is very similar.

The Displacement/Length regarding similar typed boats decreases with size, meaning that it is possible to build lighter bigger boats with the same "strength" than comparatively smaller ones and therefore they have a smaller D/L ratio, meaning that they are comparatively lighter, considering length.

So, looking at recent Oyster designs we can see that the 625 has a D/L of 180.8 but the 100, the biggest of all Oyster designs has a D/L of only 128.1.

The 825 has a D/L of 147.8, very close to the one of the Oyster 885 145.5 and that indicates already a slightly lighter built, but the one of the 90ft Polina Star is really low compared with those, with 121.9, lower than the one on the big Oyster. That indicates a even lighter built.

That does not mean that the boat cannot be strong enough with that D/L for a 90ft boat. Performance cruisers of that size can have as low as 82, but they are a different type of boat with a much lighter interior, with much more effective keels with a bigger draft and that allows a smaller ballast and a bigger proportion of their weight on the hull.

JJ77 · 26-11-2015, 10:21

Today also in Yacht.de;

Oyster 825: krasse Bilder eines WracksÂ*|Â*YACHT.DE

what a nightmare..

Cheers,
JJ

Bill Seal · 26-11-2015, 11:26

It's interesting that none of the sub-structure seems to have failed. It looks like they were depending on the peel strength of the hull laminate. I wonder if they just glue the winches on with their magic accumpuckey.

CarstenWL · 26-11-2015, 11:30

@Polux:

Quote:

for the ones talk German: What is the exact translation of "Kielflansches"?

Flansch is flange in English.

Actually it is difficult 'to guess' what they mean. By the word it would only be the 'connection area' of the keel.

Carsten

Polux · 26-11-2015, 12:02

Quote:

Originally Posted by Bill Seal

It's interesting that none of the sub-structure seems to have failed. It looks like they were depending on the peel strength of the hull laminate. I wonder if they just glue the winches on with their magic accumpuckey.

In fact the keel structure depends on the hull laminate strength or in other words on the hull integrity. The forces transmitted by the hull should be absorbed by a large part of the hull to prevent what happened here assuming no defective built. The relative small part of the hull that delaminated indicates that the forces were not sufficiently transmitted and absorbed by a large part of the hull.

And bonded agents had to be brought by somebody as the responsible for this, even on a hull that has the keel structure laminated to the hull

**neilpride** · 26-11-2015, 14:17

The laminate thicknes around the keel stub is ridiculous , Hard to see a minimum inch of glass right there, is just BS in all the aspects....

Mirage Gecko · 26-11-2015, 14:59

What is the "dog chain" shown in the photo of the inside of the keel please?

**neilpride** · 26-11-2015, 15:02

looks like a guide to run wires or a hose trough the limber hole???

transmitterdan · 26-11-2015, 15:20

Quote:

Originally Posted by neilpride

The laminate thicknes around the keel stub is ridiculous , Hard to see a minimum inch of glass right there, is just BS in all the aspects....

You may be right about that but it appears the keel stub was not the initial failure. From these pictures it appears that somewhere through the hull layup (pretty close to the inner layer) the resin did not adhere well enough. Due to the design the hull layup is in tension such that if even one layer of glass fails to adhere to its two neighbors (i.e. delaminates) there is nothing to support the ballast. When the keel fell sideways as the hull peeled away like a can of spam then the keel stub failed. But it does not appear the initial failure was the keel stub. If it were the whole bottom would not be ripped off on both sides of the keel.

From these photos the failure is most likely due to both design and construction failures. There is a reason most boats have the keel bolts land inside the hull with large load spreading backing plates. This boat looks to have been designed to have no keel boats that penetrate the hull laminate. I'm sure that seemed clever to someone at the time.

transmitterdan · 26-11-2015, 15:21

Quote:

Originally Posted by Mirage Gecko

What is the "dog chain" shown in the photo of the inside of the keel please?

Probably some remnant of the salvage operation. They had to raise the keel from the bottom so may have used a chain to attach to lifting bags. May have been used as a messenger.