Another Triple Stars issue

[davidpm]

I saw this quote on the CW website

"“At 0200, we came off a wave so hard that it blew out the knotmeter transducer. Within minutes, the floorboards were floating, all systems shut down, and the main breaker tripped. We hand-pumped 2,000-plus gallons of sloshing seawater out of the boat, but the damage was done. Everything was out due to saltwater immersion. And the engine died, and we had to get towed into Charleston.”"

I've personally experienced the same thing off on the way back from Bermuda.
I've heard of this other times also.

If this is a common vulnerability, which it appears it is, I'm surprised it is not dealt with more aggressively.
1. Better knot meter
2. Remove device before storm and plug
3. Use model that does not need spinner.
4. Skip it completely

We almost lost a Farr 395 but had 6 experienced people on board so no damage was done.

If this is such a major vulnerability it is amazing that it is not dealt with better.

[Hartley18]

David, there are an awful lot of transducers out there now from ages past and I'm not surprised to hear something like that ocurring... but as far as the "major vulnerability not being dealt with better" most of the new thru-hull Raymarine transducers available - and I'm sure many other makes also - now have:

(a) flow-limiting flaps to reduce the flow of water into the boat when the transducer is pulled for whatever reason, and
(b) screw-down retaining/locking rings.

If someone "came off a wave so hard it blew out the transducer", my immediate thought is that it was either a very old type that should have been replaced long ago and/or wasn't installed correctly. The boat must also have been pounding pretty badly at the time and in imminent danger of breaking a lot more than the knotmeter. The fairings they make for these things are designed to handle a huge v-bottom stinkpot belting through the waves at +30kts, so it seems really unlikely it can't handle whatever forces a tiny round-bottom sail-boat can dish up.

What condition was the transducer in when you got back to port?? Presumably it was completely smashed..

[Waltthesalt]

With GPS maybe we don't need knot meters

[mitiempo]

Originally Posted by Waltthesalt

With GPS maybe we don't need knot meters

GPS will tell you speed over the bottom - the knotmeter will tell you speed over the surface. Often entirely different results. Ideally you need both.

[SlowButSteady]

I'm not doubting that this was a PITA, and I realize that you got this as a second-hand account. However, something is missing from this story. If the transducer was 1 inch in diameter (about the size of a Signet transducer), and it was effectively about 1 meter below the waterline, then it would let in about 1.35 liters of water per second or about 5 cubic meters of water per hour. If the folks in this story really had to dewater 2000 gallons (7.6 cubic meters), it should have taken about an hour and a half for that much water get through the transducer fitting. Could no one jam a wood plug (or something) into the hole in all that time? Also, my calculations assume no pressure equalization (and lowered flow rate) as the boat filled, and no automatic pump(s) went on before the system failed.

Somehow, I suspect that more went wrong in this mishap than just a failed transducer.

BTW, you might note that a good sized (2000 gal/hour or better) bilge pump would have just about kept up with the flow under such circumstances.

[brokesailor]

Maybe he just meant to say a **** load of water?

[Barquito]

Somehow, I suspect that more went wrong in this mishap than just a failed transducer.

That was probably the case. They may have been dealing with a number of things, and didn't give the situation the attention it (obviously) needed. 2000 gal of water might have been an over-estimate, but, who can blame them, given the situation. Regardless, still begs the question of the OP: If the s*** is hitting the fan, maybe you won't notice that your boat is filling with water right away. Having 1" hole in the hull could be a problem. Would be a good argument for thru-hull transducers that can fend for themselves a bit more.

[tommays]

Are knotmeter transducer has a 1/4 " SS pin holding it in with a second pin locking the 1/4 " in place

It is NOT coming out and the blank is no better or worse

IF it did come out there is a wood peg tied in place right there BUT the water shoots about 2' high (trust me we clean it every week)and if nobody was home the boat would sink pretty fast

[davidpm]

Originally Posted by SlowButSteady

Somehow, I suspect that more went wrong in this mishap than just a failed transducer.

BTW, you might note that a good sized (2000 gal/hour or better) bilge pump would have just about kept up with the flow under such circumstances.

I agree that more went wrong. It always does.
That being said:

• If it was a 1.5" hold rather than a 1" hole how much faster would the water come it? double or more, you seem to have a source for that calculation.
• The 2,000 gal per hours bilge pump does not pump 2,000 gal per hour. These are ideal number based on not pumping any height at all and no restrictions.
• I suspect that you could expect a pump to be incapacitated some large percentage of time do to clogging.
• A half hour can go by very, very quickly when you are panicked and trying to find a leak then trying to figure out why the pump is not working and trying to make sure the boat is still sailing and beam to and out of control.

I think that one limiting factor in a boat emergency is that when something bad happens it is almost always combined with multiple simultaneous issues.
If there is only two people on board deciding what to do first and second is a very big problem.

And of course if there are two people and one person starts freaking out that can make it even harder for the one person to do everything especially if the freak-out person is physically in the way or a danger to themselves or others.

So I don't think that anything more than a broken speed sensor along with bad weather and the resultant chaos along with a little crew fumbling would be necessary for that particular disaster.

I think Doug Seabag's story and the one quoted above are good examples of how small things can easily escalate into life threatening events.
Sometimes even the smallest mistake or bad luck can be all it takes to turn a small issue into a big one.

[SlowButSteady]

Originally Posted by davidpm

I agree that more went wrong. It always does.
That being said:

• If it was a 1.5" hold rather than a 1" hole how much faster would the water come it? double or more, you seem to have a source for that calculation.

• The calculation is pretty straightforward. Google "flow through an orifice", or "flow through a pipe" and set the pipe length to zero.
  
  

  Originally Posted by davidpm

  The 2,000 gal per hours bilge pump does not pump 2,000 gal per hour. These are ideal number based on not pumping any height at all and no restrictions.

  Right. A one inch diameter hole will let in a bit over 1300 gallons/hour (about 5 cubic meters). So, a 2000 gallon/hr pump should either be able to keep up, or come pretty close to keeping up (depending on head height, pipe drag, et cetera)
  
  

  Originally Posted by davidpm

  I suspect that you could expect a pump to be incapacitated some large percentage of time do to clogging.

  That may well be more of a problem than anything else, particularly if the bilge hasn't been kept clean and/or the pump isn't properly installed. But, that's just one of the other things that may have gone wrong (to which I alluded in my earlier post).
  
  

  Originally Posted by davidpm

  A half hour can go by very, very quickly when you are panicked and trying to find a leak then trying to figure out why the pump is not working and trying to make sure the boat is still sailing and beam to and out of control.

  Which is EXACTLY why dewatering should start right away in such an emergency. It's also why a good, LOUD high water alarm should be installed to give the skipper and crew a heads-up that something is wrong BEFORE the floorboards start floating, AND a good high capacity bilge pump should be installed to give them some additional time to get things under control.