46' Post SF Sinks

LOL, that reminds me to my youth, when we put potatoes in exhaust tips...

This is the polar opposite of the ice to fire incident and I would really like to see the mechanics of how either could happen. One has the pipe being blocked because it expands, the other has it blocked because it shrinks. In either case the muffler had to be made with gas path clearances of only a few thousandths of an inch for that to happen.

Reference the thermal characteristics of a thin tube made of 18-8 SS, if it were 10 inches in diameter it might change diameter by 5 or 6 1/1000th of an inch across a temperature swing of 500F or so.

(numbers are purposely vague because steel alloy is unknown but generally a number of 0.0000096 inches per inch change per degree F applies)

Jimbo

Any new facts on what may have happened?

Hi

My friend what happen now?
Think about it, if you have a loud explosion at the dock, it might take you a few minutes to figure out what just happened.

Hi Marc, Not much to think about...loud bang...either you've been shot, or your boat is going to sink...the mind can process that pretty fast.

Yeah, but your first instanct is to check the engine room. That boat went down in a minute flat. It takes longer than that to figure out it didn't come from the engine room.....also opening a lazarette hatch, you probably can't even see the mufflers......

Engine

probably you're right Capt, this kind of incident has such a turn, so I believe that your analysis is more precise. thank you

in my 46 you have to lift out the fish box to get to the bilge.
Just one more step.

and some fish boxes are full of stuff that has to be emptied of "stuff" before you can lift out the box.

In this case, it was probably full of ice if they were headed out fishing. In my experience and the water flow figures Marmot published, and what Jimbo described.....this boat went down in a minute or two......very hard pressed for anyone to stop it in time. Unfortunately.

yes some engines are hard to run and require well-established techniques, most of people should have a minimal knowledge

Must have been one big a*s beaver!

Was the Beaver stuck in the exhaust and that's where the explosion came from? The beaver thing doesn't make a lot of sense because you'd think that the boat would've sunk on it's own before the motors were even running, as it looks like the exhaust sits with water in it all of the time at the dock.

Hey, I wasn't the one who came up with that lame excuse...then I thought about what kind of animal lives in water and like to burrow? Beaver! I was going to go with Octopus...but that would be just down right silly. So according to "surveyor" this genius figured an animal crawled up in there and caused the back pressure....it's about as intuitive as my Beaver! C'mon J, I thought it was funny.

I thought the General consensus of the Forum was fiberglass fatigue...I tend to believe that's the best theory as opposed to some animal! I can't believe they would list a cause like that. So the wisdom of the Forum seems to hold true in this case, all surveyor's are not created equal...and you get what you pay for. Animals. Holy Crap! I need another drink.

Animals can chew through a lot, but seldom metal. More likely he crawled inside through the outlet and made himself comfortable. He may have needed to slink himself in, but when the engine started or water flowed in he wouldn't have the time nor thought to slink himself back out. In panic he'd just clog the outlet with his body or nest and boom. I've seen a few cases where squirrels went in through bilge or drain openings, then chewed their way into the boat pretty well destroying it. First time I've heard of this result. Most times I imagine they'd exit as soon as the boat starts moving in the lift or certainly when splashed. I always recommend taping over all opening for that reason although I've never bothered with the exhaust. Maybe now a a few more pieces of tape would be a good investment.

I think it was fiberglass fatigue as well as a blockage or excessive backpressure. Which could've been caused by a few people standing back there putting the exhaust underwater.

I don't think tape would be any match for some determined beaver!!!

The whole concept is a little fishy, one would think the beaver or whatever it was would have taken off as soon as folks started to move around onboard.

On the subject of animals entering spaces and being too big to exit I worked with a couple of fishermen off the factory trawlers in the Southern Ocean, they said seals used to get under the fish factory floors at the start of a trip and be too fat from all the junk they ate to get out again at the end, their stories of how they got them out are not suitable for YF

Going back to look at the photos in post #22 again, I too think there is something a little fishy. Fiberglass fatigue in piping happens when a system has been subject to severe over-pressure a great many times and seldom fails catastrophically as this pipe did.

That pipe doesn't even look like it is made of fiberglass, it looks more like PVC or other material that might have had a very thin wrap of very light glass cloth. It appears to have a seam at the bottom of the photo, there is no separation of plies as would be evident on the edges away from any initial point of fatigue failure. The only indication that glass fiber was used anywhere is the appearance of what looks like a very few places where some fiber material was ripped out from under a paint layer.

Most fiberglass exhaust components made by reputable manufacturers show some weave beneath the paint, they are functional devices that don't receive a great deal of cosmetic treatment. The lack of fibers showing at the broken edges, the perfectly straight and undamaged seam, and the fracture mode that more closely resembles plastic pipe makes me wonder if the muffler was home-made or a counterfeit.