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Old 01-27-2016, 02:01 PM   #101
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OC-you have raised an interesting point. Does any builder estimate potential water inflow from various holes in the hull when sizing dewatering pump capacity? Also, a hose failure downstream of a seawater pump actually may one of the better places to have a hose failure. If my input to an online water flow calculator I found is correct, the inflow is pretty scary. At sea level water pressure of about 14.5 PSI, a 4" hole will flow at over 68,000 gallons per hour! That does not sound right to me, but that is what the engineering site came up with! The seawater pump will actually function to limit the seawater intake if the hose breaks downstream. Water cannot flow freely through the pump. If your pump is 35 GPM, that is 2,100 GPH. An amount that certainly can be handled by a decent bilge pump system. In comparison, one 4" hole, unnoticed for 30 minutes, can get close to 35,000 gallons in your boat. BTW-I hope I got the water flow wrong somehow, now I have scared myself.
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Old 01-27-2016, 02:19 PM   #102
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At this point, we know two things. One is that the First Officer believes they might have grounded coming out of the Bahia Mar area. Second, that he says the first they realized they had a problem was when the boat was listing. A boat that size and classed previously would typically have something in the range of 10 pumps and alarms. Two for every bulkhead area. It also would have several emergency systems including a couple 110 and/or 24 V with 1 1/2" or so pipes plus a very strong emergency system engine driven. The other thing they should have aboard is an emergency patch kit.

Not knowing the nature of the water ingress we can't know if everything had gone right whether or not they could have kept afloat. We also don't know the systems they had. But in a classed boat with even a 4" hole, alarms, pumps and patching should have given them a good change of keeping things afloat.

Now, if it was the stabilizer from grounding, had they detected that problem on it's own, that would have given them good odds. At the very least that should have sent someone to the engine room to keep an eye on things in case anything beneath the boat hit and caused a leak. You can check those things from inside. Now, they also could have dived or used a camera to check externally.

The key to defending against any breach is detecting it the earliest possible. From their statements, they appeared not to detect it until quite a while after it happened.
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Old 01-27-2016, 02:21 PM   #103
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At sea level water pressure of about 14.5 PSI, a 4" hole will flow at over 68,000 gallons per hour! That does not sound right to me, .
It isn't right, so you can be less scared. Try about 0.43 psi per foot of head.
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Old 01-27-2016, 02:22 PM   #104
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http://www.bethandevans.com/pdf/Hole...odingtable.pdf

not sure if accurate but have no reason to doubt....


5 inch hole 4 feet under water is 60,000 gallons per hour.


Most vessels where a listing is noticed has enough water in it that unless absolutely flat water would have a noticeable "different" motion to it...THT is really strange that it wouldn't be investigated.
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Old 01-27-2016, 02:29 PM   #105
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OC-you have raised an interesting point. Does any builder estimate potential water inflow from various holes in the hull when sizing dewatering pump capacity? Also, a hose failure downstream of a seawater pump actually may one of the better places to have a hose failure. If my input to an online water flow calculator I found is correct, the inflow is pretty scary. At sea level water pressure of about 14.5 PSI, a 4" hole will flow at over 68,000 gallons per hour! That does not sound right to me, but that is what the engineering site came up with! The seawater pump will actually function to limit the seawater intake if the hose breaks downstream. Water cannot flow freely through the pump. If your pump is 35 GPM, that is 2,100 GPH. An amount that certainly can be handled by a decent bilge pump system. In comparison, one 4" hole, unnoticed for 30 minutes, can get close to 35,000 gallons in your boat. BTW-I hope I got the water flow wrong somehow, now I have scared myself.
Absolutely builders estimate that. Class societies do as well to varying degrees. Boats are equipped to fight such a breach. Crew is trained to do so.
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Old 01-27-2016, 02:39 PM   #106
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All of which points out the nicety of bulk headed stabilizers. I've seen two setups on recreational boats, one an older DeFever and the other on the Dashew FPB series. I have seen some well hidden stabilizer installations on a few larger yachts, not very accessible in the event of a shaft coming out for pounding in a plug.

Again all this is speculation.
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Old 01-27-2016, 02:39 PM   #107
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Absolutely builders estimate that. Class societies do as well to varying degrees. Boats are equipped to fight such a breach. Crew is trained to do so.
Not production vessels under 65 feet...not sure I have ever seem a factory boat with enough bilge pumping capacity to actually handle an engine intake completely gone and the derated for head/voltage capacity match. That's for us poorer guys....

But class vessels and the better boats maybe/probably.....
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Old 01-27-2016, 02:54 PM   #108
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All of which points out the nicety of bulk headed stabilizers. I've seen two setups on recreational boats, one an older DeFever and the other on the Dashew FPB series. I have seen some well hidden stabilizer installations on a few larger yachts, not very accessible in the event of a shaft coming out for pounding in a plug.

Again all this is speculation.
I have seen some great setups on all kinds of boats...rarely do I ever see all the good put into one boat.

Of course I tend to worry a bit...flew single engine helicopters in places no one should so it's been beaten into me to worry a little about a few things....but most boaters tend to overworry the basics that are easy to check/correct and miss the stuff that can haunt them at the wrong time.

Like everything...if you have the basics in good order... you should be good to go. But run a boat aground and ignore potential damage, take it to sea, ignore a list (if any of these tidbits are true)...then being on a sinking boat shouldn't be a surprise.
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Old 01-27-2016, 02:56 PM   #109
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Not production vessels under 65 feet...not sure I have ever seem a factory boat with enough bilge pumping capacity to actually handle an engine intake completely gone and the derated for head/voltage capacity match. That's for us poorer guys....

But class vessels and the better boats maybe/probably.....
I agree with that. Most builders way under size the capacity of the pumps they put in.
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Old 01-27-2016, 03:11 PM   #110
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I agree most boats don't have what I described, but a 120' classed vessel should. I was describing what I felt the boat in question should have had based on boats in that size range I'm familiar with. There just should have been many alarms going off much sooner than they detected a problem.

It's also my understanding that some of the class societies require stabilizers to be installed watertight while others don't require that. I haven't checked it myself, but was told ABS doesn't require it.
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Old 01-27-2016, 03:39 PM   #111
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It's also my understanding that some of the class societies require stabilizers to be installed watertight while others don't require that. I haven't checked it myself, but was told ABS doesn't require it.
Stabilizers should break the fin way before they endanger the hull mounting.

Same with pod drives... but there are cases where things don't break where engineers say they should.

Wait and see.

I found the rate of flooding computation formula:

the formula to compute the flood rate is as follows:
gpm = 5.67 x diameter of the penetration squared multiplied by the square root of the depth below the waterline.
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Old 01-27-2016, 03:57 PM   #112
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That flooding formula seems quite a bit higher than the chart I posted and a couple other sources I just looked up.


Not that it is all that important...just curious whose formula?
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Old 01-27-2016, 04:28 PM   #113
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Old 01-27-2016, 05:16 PM   #114
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the formula to compute the flood rate is as follows:
gpm = 5.67 x diameter of the penetration squared multiplied by the square root of the depth below the waterline.
So, 5.67 x 4 x 4 x 3.16 or so.

287 gpm

16,680 per hour. The bethanddevans chart shows 1,012 per minute. So this formula is considerably less if my math is correct.

Is it 5.67 x (diameter squared) or (5.67 x diameter) squared.

I assumed the former. The second interpretation would give 1,625 gpm so much higher.
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Old 01-27-2016, 05:44 PM   #115
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Thanks for that post and link stubones; I was searching for that chart in vain.

I remember being scoffed at here for having 8 bilge pumps. And a large dewatering pump.
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Old 01-27-2016, 06:17 PM   #116
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And with credit to a quiet forum member, as to the question of whether ABS has the same rules as Lloyd on stabilizers. Posted on another forum.

So does ABS. The rules for yachts follow the "standard" IACS wording that the stabilizer be fitted in a watertight compartment or if damaged cannot lead to flooding of auxiliaries or other necessary equipment or create progressive flooding.
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Old 01-27-2016, 06:23 PM   #117
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http://www.maritime.org/doc/pdf/salvorshandbook.pdf

this is another source with slightly different formulas. Look on page 227 mid way down.

Stu
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Old 01-27-2016, 06:42 PM   #118
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http://www.maritime.org/doc/pdf/salvorshandbook.pdf

this is another source with slightly different formulas. Look on page 227 mid way down.

Stu
I don't get the same page numbering as you apparently. Can you give a section number?
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Old 01-27-2016, 06:47 PM   #119
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I don't get the same page numbering as you apparently. Can you give a section number?
Flooding rate. Use the search function since it is a searchable PDF.
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Old 01-27-2016, 06:51 PM   #120
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And with credit to a quiet forum member, as to the question of whether ABS has the same rules as Lloyd on stabilizers. Posted on another forum.

So does ABS. The rules for yachts follow the "standard" IACS wording that the stabilizer be fitted in a watertight compartment or if damaged cannot lead to flooding of auxiliaries or other necessary equipment or create progressive flooding.
Most of the boats at FLIBS had a bunk over the stabilizers.

That's another problem with standards if they let you inspect and grade your own work. I guess the bunk occupant is the early warning system.
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