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Old 25-07-2014, 15:17   #106
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Re: The Blue Pearl Sinking

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Originally Posted by sailorboy1 View Post
I think for the most part "overbuilt" means the builder didn't/couldn't calculate the forces so threw more material at it hope that it was strong enough.
I think that is partially true. Modern 3D computer stress analysis modelling allows the designer to calculate the loads much more accurately. This has the benefit that the structure can be strong where it needs to be, but lighter elsewhere.

However, for a cruising boat there is advantages in having some structures stronger than might be deemed strictly necessary. "Overbuilding" in other words.

If we take the rudder for example. The hydrodynamic loads can be be accurately modelled and a perfectly adequate rudder constructed. On the other hand an "overbuilt"rudder will cope with the hydrodynamic loads, but might also be able to sustain an impact with a large object such as a log at moderate speed, or remain functional after a grounding on rocks. Such an overbuilt rudder is likely to be more expensive and heavier, but many cruising sailors are prepared to put up with the drawbacks to gain this extra protection.

The intended function of the boat is important. Within reason,"overbuilding" of key structures is a very positive attribute for a long distance cruising boat.
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Old 25-07-2014, 15:23   #107
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Re: The Blue Pearl Sinking

But you are just making an assumption that the builders aren't already "overbuilding". It is standard design in lots of structural engineering design to have safety factors up to 50% over what is needed.

If you start designing for impacts when do you stop as to what you are factoring in being hit (logs, whales, super tanks, Africa)?
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Old 25-07-2014, 15:25   #108
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Re: The Blue Pearl sinking

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Originally Posted by Bluewaters2812 View Post
Okay, I thought we are hull 80 but yes it is 5080.

FR-BEYF5080i607

I think hull number 5088 was a Cyclades 50 but wonder who it was sold to?

Len

Is it model type F5 and hull #080? That's the way those specific digits would parse out from the HIN on our model...

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Old 25-07-2014, 15:27   #109
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Re: The Blue Pearl Sinking

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On the other hand an "overbuilt"rudder will cope with the hydrodynamic loads, but might also be able to sustain an impact with a large object such as a log at moderate speed, or remain functional after a grounding on rocks. Such an overbuilt rudder is likely to be more expensive and heavier, but some cruising sailors are prepared to put up with the drawbacks to gain this extra protection.
Geesh...that's not overbuilt. That is built correctly for mission. I don't want to go to sea in a boat that just meets engineering specs for a perfect voyage. Its like cars that are built so the occupants stand a chance of surviving a collision. I've spent a night grounded on a sandbar inside a reef off the Mexican coast. One of the longest nights of my life. We survived, the boat survived, but it took a pounding that wouldn't likely be in any computer analysis software of a mass production boat builder today.
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Old 25-07-2014, 15:58   #110
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Re: The Blue Pearl Sinking

Getting back to the reality of living with what you have and learning from this event.

If you have a spade rudder system like Len's.... Do the reverse figure 8 test I mentioned before on a regular basis, paying particular attention to harmonic fatigue in the structural supports.

Recognize that Spade rudders are unprotected and more susceptible to catastrophic failure due to hitting logs, containers ...etc ...
As Jim advised... Look at a way to seal that section from flooding the rest .

If shopping for a trans ocean yacht.... Decide if a rudder protected and supported at the bottom with a strong Skeg.... is one of your priorities?
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Old 25-07-2014, 16:16   #111
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Re: The Blue Pearl Sinking

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Originally Posted by Jimbo485 View Post
This is correct. Not hard to do and makes total sense.

All of our thru-hulls, except the water maker intake, are located on the other side of watertight walls that extend higher than water level.

This means that rudder failure, stern or bow collisions or thru-hull failure are all contained and separate from the main internal hull volume but all still accessible for observation or repair.

The effort and cost to design this in to a boat is negligible.
But how much higher than the waterline are the bulkheads? Have you calculated what would happen if that compartment floods? How much water will the compartment hold and will that weight be enough to lower the boat in the water so the top of the bulkhead becomes lower than the waterline?

You know that is what happened to the Titanic?
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Old 25-07-2014, 16:30   #112
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Re: The Blue Pearl Sinking

Here is a pic of my friends bene's stern tube...

It was a 2003 not a 2006.
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Old 25-07-2014, 16:59   #113
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Re: The Blue Pearl Sinking

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But how much higher than the waterline are the bulkheads? 150 mm. Any slop over the edge will not be catastrophic, but we can easily block it off if necessary.

Have you calculated what would happen if that compartment floods?
Yes.

How much water will the compartment hold and will that weight be enough to lower the boat in the water so the top of the bulkhead becomes lower than the waterline?
150 litres. No.

You know that is what happened to the Titanic?
Yes.

Actually in addition to these sections, we also have totally sealed sections at all bows and sterns that go to deck level. Effectively we have 8 compartments, 4 totally sealed and 4 to above the waterline. This is easier on a cat because of the shape of the hulls but our steel monos also had the totally sealed feature.

People worry more about EPIRBS and calling for mummy than preparing a well designed, tough boat.
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Old 25-07-2014, 17:02   #114
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Re: The Blue Pearl Sinking

zboss:

Golly, do you know what caused that damage? Merely repeated cycles? A blow?

Ann
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Old 25-07-2014, 17:17   #115
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Re: The Blue Pearl Sinking

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Originally Posted by Jimbo485 View Post
Actually in addition to these sections, we also have totally sealed sections at all bows and sterns that go to deck level. Effectively we have 8 compartments, 4 totally sealed and 4 to above the waterline. This is easier on a cat because of the shape of the hulls but our steel monos also had the totally sealed feature.

People worry more about EPIRBS and calling for mummy than preparing a well designed, tough boat.
Yep, it can be done in a monohull too! We have two watertight bulkheads forward: between the chain locker and the sail locker, and between the sail locker and the forepeak cabin. Then there is the aft one, between the lazarette (where the skeg and rudder assemblies are located) and the aft cabins.

While one can envision scenarios where these are of little avail, they do offer considerable protection in the event of collision or rudder strikes.

These sorts of features are why we bought a "one-off" boat rather than a production boat... the design was not compromised by an accountant or a marketing manager. It would be very expensive to design and commission such a boat from scratch. None the less, we paid about the same for our boat at 13 years of age as a similar sized Bennie of around 5-7 years age. The decision was a no-brainer for us. At some point we will have to give up our lifestyle and sell our boat/home. I confidently expect that she will bring more return at that time than would the equivalent priced Bennie, etc that we might have purchased in 2003. There is always a market for quality.

Cheers,

Jim
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Old 25-07-2014, 17:48   #116
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Re: The Blue Pearl Sinking

Inded!!! safety factors are raped by some builders without talking about hull scantlings, raped to!!!

My impresión is some builders are just in a rush to build the next hull and give it up with some basic construction, like this particular rudder post construction, man come on, what the frokkk is thinking the builder designing this Fg tube without lateral real fg supports or that crapy ply ridiculous tabbed to the Wall? its insane...... to add more dog **** to this pile of errors some builders even choose hollow SS tube for rudder shaft construction, gime a break...

my guess is 3 more layers of FG , a bunch of ply pieces and solid stock make a diference in final boat Price of 500? 1000? there is only one thing come to my mind , save money ...500 or 1000 is nothing for us but from a builder doing thousands hulls each year its a big deal, its called mass production chain of errors ..no matter how brutal a collision in the rudder can be , the structure need to be intact...same aply to keels... more complex to design and build...

And to sumarize , some EU builders CEO need a strong kick in the ass but they are hiding in a Wall of numbers, thinking oh well its just 1 hull of 3000, who care? my 2 cents,,,
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Old 25-07-2014, 17:53   #117
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Re: The Blue Pearl Sinking

A good tool will come with bulkheads fit in and watertight doors in them. Amels did, Oysters did, not sure if they stick to this noble tradition.


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Old 25-07-2014, 18:03   #118
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Re: The Blue Pearl Sinking

Amel yes, still doing collision bulkheads full watertight and the engine room is watertight to....
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Old 25-07-2014, 18:54   #119
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Re: The Blue Pearl Sinking

There are some clever boat builders out there who do go to the extra effort. Unfortunately they are not appreciated and usually go broke. Many conversations on this forum show this lack of appreciation. The German boatbuilding dynasty in Brazil who built our boat went out of business the same way I understand.

I do like the way they designed our thru-hulls to be in one of the partially sealed compartments (open on top but walled off above the water line). This same design logic applies to the battery compartment and main water tank. The cost and effort are so small compared to the level of risk reduction. Clever German boat builders and British designers and Brazilian tradesmen!

None of our electrics are below the waterline except for the battery compartment and controller inverter compartment which are both independently walled off above the waterline. All bilge pumps are mobile to cater to all the various compartments and almost all bilges are dusty. In some compartment walls I have drilled limber holes and then plugged them with shaped wine corks for increased flexibility when the SHTF.

If most boats hit something hard, they will take on water, electrics will go under and then they will hit the rescue button. There are better ways.....
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Old 25-07-2014, 19:02   #120
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Re: The Blue Pearl Sinking

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Originally Posted by zboss View Post
Here is a pic of my friends bene's stern tube...

It was a 2003 not a 2006.
http://www.cruisersforum.com/forums/...4&d=1406327413
OMG. There is no resin in that laminate!
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