Drain holes...????

[belercous]

I now see the error of my ways.

And I also now understand why I thought baffles open at the bottom would take on more water than ones which are open at the top. I was only figuring on the compression of the air above the water in the cell with the hole & not the air above the water in all of the cells. That would explain why my boat doesn't list despite being fairly heavy: the more cells a log has the more buoyant it'll be.

My logs don't have drain plugs so perhaps I'll have a couple put in when I take it to the shop next year.

[Captain Tony]

Thanks guys:
I agree with the difficulty of draining a tube if all baffles were closed at the bottom - it just wont flow to a rear mounted drain plug.

I got a little more information from both Belercous and Moser's explanations.
I can see their logic in a pontoon boat tube that is static - i.e. not moving and not gaining water weight.

And I agree with the position that the level of water in a ruptured section of tube will seek the same level as the water the tube sits in.
Unless a pressure force were acting on the water it can't go higher than the outside level surrounding it. Right on so far !!

However, my assumption of water moving to the next section in progression, is based on the added weight in that ruptured tube
which would cause it to settle ever increasingly into the lake/river.

Each additional volume of water increases the list and quantity of water being driven, under way, eventually flooding the majority
of the tube to the point that it exceeds the remainder buoyancy of the currently undamaged sections.

Also as an aside, Berlercous you are correct that the metal of the Titanic was inferior as proven in the Olympic however, the fact remains
that each of the so called watertite compartments were designed with the bulkheads not reaching all the way to the top and sealed to the deck above it.
Not just a small amount of space which may have slowed the inevitable, but a considerable amount and therefore creating "The Perfect Storm" of Titanic ship flaws.

So if the Titanic had not ripped open so many compartments it may not have taken on so much water and sank but the compartments still
contributed to the demise as they allowed water & weight to fill too much of the then buoyant ship. As to "watertite" - they were not !!

Good discussion. My contention is based on a pontoon tube being punctured and then being driven to shore, dock, shallows etc.
By virtue of the forward movement more & more water must surely enter.

What do you think ?

[Moser]

I agree Tony, the key word being eventually.

The tubes I've seen cut open were both round Crest tubes, one of them is my current center tube which was cut down from 23 feet to 14 feet The gaps at the bottom of the baffles were SMALL perhaps 3/4 of an inch high maximum and tapering down following the interior of the tube, maybe 3 to 4 inches wide across the bottom of the baffle. That is not a very big gap, just enough to let the tube breathe and drain small quantities of water. Once the breached section has leaked enough to cover that gap there is no way for water to get in because the trapped air is holding it out, if the air stays in, the water stays out. This provides a catastrophic fail safe, it is desigend to keep you from sinking quickly in the event of a hull breach. No you can't keep using it and with enough sloshing around it will allow more and more air out, and water in.

I looked for that Tahoe tube I saw a picture of last week, that baffle was all the way around the inside of the tube, with a hole about 3/4 of an inch right at the bottom, but now I cant find the picture.

One day when I'm under my boat I'll pull the plug out and run my little Depstech camera up in it and take a picture of the baffle and the gap, seeing it makes it easier to understand what it is doing.

[Captain Tony]

Thanks Larry.
Makes sense. I would be interested in seeing that when ever you get that camera in the 'toon.
Just an F.Y.I. - the attached link is about the new Titanic II soon to be launched in 2022.

https://allthatsinteresting.com/titanic-2-ship

[belercous]

"And I agree with the position that the level of water in a ruptured section of tube will seek the same level as the water the tube sits in.
Unless a pressure force were acting on the water it can't go higher than the outside level surrounding it. Right on so far !!"

That was my belief until I realized that the water level in the damaged section (cell) wouldn't reach the same level as water it sits in because it's not dependent on the buoyancy of that particular cell, but rather all the other cells combined. As Moser said, the only cell which could have that level, or higher, would be the one with the vent. Even in the breached cell the water level couldn't rise to the level the pontoon rides at because it's not just the air pressure in that cell it's working against, but the air pressure in every cell which counter-reacts it.

Tony: besides the inferior metallurgy of the Titanic's skin, more sections were ripped open than its designers planned on. Further exacerbating the Titanic's problem was the fact that the sections were not sealed off as quickly as the engineers had planned for. Sealing off the damaged sections would not have prevented the ship from sinking, but it would have kept it afloat longer, perhaps allowing more people to be saved by buying more time for other ships to rescue the passengers.

As for driving a boat with a damaged pontoon to shore (under full power): the extra pressure speed would have put on the log, filling it with more water, would have been relieved when the boat stopped as the added pressure of speed would have been removed & the pressure inside the log would have equalized to stasis (sought equilibrium).

[Captain Tony]

Hey guys: If the Titanic were a pontoon - the trip would be very cold !! And it was that night.

We visited Halifax Nova Scotia four years ago and went to the grave site of some of the victims that were
found and brought to land. A very touching and somber site. 209 Victims recovered and carried to land.
Some shipped to family by rail and the rest buried in 3 Halifax cemeteries'.

Here are my final thoughts on the ill fated ship.

Designer Hubris.

The Titanic was famously described by its operator as “practically unsinkable”, because its hull was separated into sixteen “watertight” compartments using remotely activated watertight doors. If the hull were to be penetrated, that compartment would be closed to prevent propagation to other parts of the vessel. In the worst case, this design was assumed to enable the ship to sink very slowly and allow passengers to evacuate with time to spare. However, these compartments were not really watertight, as they did not possess a roof section (making the bulkheads higher would have reduced interior space and made the ship less comfortable for passengers). When the iceberg sliced through the hull of the first six compartments, a chain reaction began of the watertight bulkhead filling up, then flooding the compartment beside it.

This paragraph taken from the below article on what happened and why. Many factors involved but even with 5 or 6 of the "Watertight" compartments ripped open the ship could have stayed on the surface longer if the compartments were "Watertight"

https://risk-engineering.org/concept/Titanic

I know this doesn't relate to where the holes are in a modern day pontoon tube; but I found it interesting and wanted to share the facts.

[FogHorn]

I have imagined I was Capt Smith and wondered what I’d have done faced with the problem... and thought I’d try perhaps to pump the water into the aft compartments or open seacocks to the aft compartments to keep the ship more “level” .... wondering if that were possible/practical and might save the ship ....