A dinghy as a lifeboat

[fish53]

Originally Posted by MartinR

I have 2 pieces of rubberised sailcloth with eyelets in the corners I can use for fothering. Normally we use them as sunscreens for the pilot house windows.

I think this is a lot about mental preparedness. Having thought through what to do in different kind of emergencies. Not to panic with 2 feet of water sloshing around in the boat.

Have you ever calculated the amount of flooding before negative buoyancy is reached? I've seen a sailboat sink and the last foot or so of freeboard goes pretty fast, I would assume it's the keel weight. I've also seen powerboats that remain awash on the surface for a surprising amount of time. Somewhere I have a flooding table that gives volumes of water from different size holes at differing depths, I'm sure that's easily found on the internet.

[Adelie]

Negative buoyancy occurs when the boat dips below completely below the surface. Even with a hole in the hull the boat has positive buoyancy. Rapid loss of buoyancy starts when a port, lazarrette or the companion way go below the exterior surface of the water. That’s when it goes fast. Trim may be slowly changing up to that point but the boat is still positive.

The better question is how much floatation would it take to float you boat at some reasonable trim. I calc’d it for my boat so I could figure out how much buoyancy.

I figured about 2600lb floatation which works out to 40cf.

The ballast is 1000 lb dry or 880lb immersed.
The hull and rig is about 1000lb. Floating at the desired depth I figure 400lb will be immersed. While the fiberglass hull is denser than seawater a lot of bulkheads will also be immersed which are lighter so I figure the immersed section is neutral. That leaves 600lb hull, deck& rig needing to be supported.
My water storage is under the cockpit so as the section floods the water becomes very slightly buoyant since it’s fresh water. Actually the water is all in 1/2gal containers and any empty ones will provide about 4lb buoyancy each. I’m calling for worst case so I assume they’re full and neutrally buoyant.
Anchors and chain are about 70lb but stored below flooded waterline so about 64lb.
I have about 170lb batteries which will be immersed but the panel is above the waterline so I just call that 170 even.
The motor and fuel in the cockpit will be above the waterline. Together I’m figuring about 150lb.
Any personal gear under the v-berth would be approximately neutral. I’m intending to store things under the V-berth in drybags with the closure down so air can’t leak out over time. I’m ignoring that for this calculation.
That’s 1870 so I call it 1900.
I need to keep me and 1 crew above the flooded waterline so 2x250 is 500.
200lb of food above the waterline gives me 2600.

What I’m aiming for is the flooded boat to float with the interior water level at the cockpit sole and at the level of the V-berth.

I have a lot a ideas about where to put all the floatation but I haven’t started installing so I won’t go into that.

[fish53]

Originally Posted by Adelie

Negative buoyancy occurs when the boat dips below completely below the surface. Even with a hole in the hull the boat has positive buoyancy. Rapid loss of buoyancy starts when a port, lazarrette or the companion way go below the exterior surface of the water. That’s when it goes fast. Trim may be slowly changing up to that point but the boat is still positive.

The better question is how much floatation would it take to float you boat at some reasonable trim. I calc’d it for my boat so I could figure out how much buoyancy.

I figured about 2600lb floatation which works out to 40cf.

The ballast is 1000 lb dry or 880lb immersed.
The hull and rig is about 1000lb. Floating at the desired depth I figure 400lb will be immersed. While the fiberglass hull is denser than seawater a lot of bulkheads will also be immersed which are lighter so I figure the immersed section is neutral. That leaves 600lb hull, deck& rig needing to be supported.
My water storage is under the cockpit so as the section floods the water becomes very slightly buoyant since it’s fresh water. Actually the water is all in 1/2gal containers and any empty ones will provide about 4lb buoyancy each. I’m calling for worst case so I assume they’re full and neutrally buoyant.
Anchors and chain are about 70lb but stored below flooded waterline so about 64lb.
I have about 170lb batteries which will be immersed but the panel is above the waterline so I just call that 170 even.
The motor and fuel in the cockpit will be above the waterline. Together I’m figuring about 150lb.
Any personal gear under the v-berth would be approximately neutral. I’m intending to store things under the V-berth in drybags with the closure down so air can’t leak out over time. I’m ignoring that for this calculation.
That’s 1870 so I call it 1900.
I need to keep me and 1 crew above the flooded waterline so 2x250 is 500.
200lb of food above the waterline gives me 2600.

What I’m aiming for is the flooded boat to float with the interior water level at the cockpit sole and at the level of the V-berth.

I have a lot a ideas about where to put all the floatation but I haven’t started installing so I won’t go into that.

Rather than give up 40 cubic feet of space I'd consider an inflatable option.

[Dockhead]

Originally Posted by fish53

Other than readily available plugs for all hull penetrations, a damage control kit, premade panels to replace broken windows and adequate pumps, manual as well as powered, what else is there? I have seen an inflatable sort of tube that when inflated partially filled the interior of the boat but I have no real information on those.

Well, there is:


1. Proper bilge alarm so that you are aware of flooding early. I am amazed at how many boats lack this. If you're sailing hard and everyone is in the cockpit and something happens, you might not notice until it's too late.



2. Procedures, thought through, written down, rehearsed with the crew.


3. Plugs, and materials for fothering.


4. A real dewatering pump. Bilge pumps aren't designed for the bulk removal of water. I have a massive 44,000 gph trash pump with folding fire hose discharge.




Flooding is terrifying. Fortunately it happens rarely, but Plan "A" absolutely should be to fight to keep the boat from sinking. If you're not prepared to do that, it is unlikely that you will be able to overcome a flooding emergency.



Life raft is definitely Plan "B", but the goal is to stay separated from the ocean (and thus alive) in any case, and no matter the circumstances.

[Kenomac]

Originally Posted by Dockhead

Well, there is:


1. Proper bilge alarm so that you are aware of flooding early. I am amazed at how many boats lack this. If you're sailing hard and everyone is in the cockpit and something happens, you might not notice until it's too late.



2. Procedures, thought through, written down, rehearsed with the crew.


3. Plugs, and materials for fothering.


4. A real dewatering pump. Bilge pumps aren't designed for the bulk removal of water. I have a massive 44,000 gph trash pump with folding fire hose discharge.




Flooding is terrifying. Fortunately it happens rarely, but Plan "A" absolutely should be to fight to keep the boat from sinking. If you're not prepared to do that, it is unlikely that you will be able to overcome a flooding emergency.



Life raft is definitely Plan "B", but the goal is to stay separated from the ocean (and thus alive) in any case, and no matter the circumstances.

What is a "trash pump"? Make, model and cost?

[Dockhead]

Originally Posted by Kenomac

What is a "trash pump"? Make, model and cost?

A trash pump is a pump with macerating blades and large diameter discharge, and high powered motor, intended to drain construction sites with water full of debris. It makes an ideal dewatering pump.


Because in a real flooding emergency, all kinds of debris ends up in the bilge water, and non-macerating pumps clog.



Mine is German, I think Wilo is the brand, with a 3" discharge and weighing something like 30 kilos. It came by truck in a wooden crate and I hauled it on board using the boom as a crane.



A hard choice is gas powered or electric. Mine is electric, but my generator is mounted well above the waterline.

[Kenomac]

Where do you keep the thing (trash pump)? I thought you were the one obsessing about excess weight? We have a large macerating bilge pump that weighs in at only around 20 pounds. Why is yours so heavy?

Make, model and picture please.

After looking online at Honda trash pumps, it looks like one would need to have at least a four inch hose and be the size of your stern locker in order to move 24,000 gallons per hour.... so yours is actually larger?

[IslandHopper]

The trash pumps we have on our work vessels are all Diesel and if i was going to have one on my boat it would be the same, can't see the point in Gas (petrol) or electric....

Similar type units to these...

https://www.riequip.co.nz/shop/Buy+W...rash+Pump.html



Plenty of options if you have the space.....
https://www.google.com/search?rlz=1C...YRZprU#imgrc=_

[Kenomac]

Originally Posted by Dockhead

A trash pump is a pump with macerating blades and large diameter discharge, and high powered motor, intended to drain construction sites with water full of debris. It makes an ideal dewatering pump.


Because in a real flooding emergency, all kinds of debris ends up in the bilge water, and non-macerating pumps clog.



Mine is German, I think Wilo is the brand, with a 3" discharge and weighing something like 30 kilos. It came by truck in a wooden crate and I hauled it on board using the boom as a crane.



A hard choice is gas powered or electric. Mine is electric, but my generator is mounted well above the waterline.

The closest thing I could find to what you’ve described looking online for a self-priming salt water trash pump capable of the volume you claim, is a 4 inch electric pump weighing 350 pounds costing $2200-over $3,000 that can handle 44,000 gph, everything else is twice as heavy, twice as large and more expensive.

https://pumpbiz.com/manufacturer/amt...p-15hp-4872-95

I’d be very curious to see exactly what you have on your boat, where you put it and why you thought it necessary to take it to this level?

We have a Jabsco puppy pump 11gpm combined with a KPM Predator 350 50gpm on each boat.
https://www.jabscoshop.com/marine/pu...24-volt-dc.htm

[RaymondR]

I have pondered on the rapid flooding scenario on and off for years and a couple of the ideas I have come up with were:

Internal fothering using the inflatable bags that 4WD enthusiasts use which are inflated using the engine exhaust. Many of the places in the hull which are most likely to be breached are situated in relatively small volumes where a big, tough balloon would tend to plug the breach when inflated.

Massive volume pump with the impeller mounted on the front of the engine flywheel. Most of the time it would just spin in the air, however rising bilge water would prime the pump allowing massive volumes of water to be pumped from the hull.

An attachment clamped onto the outboard motor which would turn it into a high volume, low head, propeller pump similar in principle to those used by irrigators.

[MartinR]

I guess you have a submersible centrifugal pump that can accept bigger particles, not macerating? These are great and not too heavy.

On another note, watertight/water delaying compartments improve safety a lot. Not hard to integrate.

[Simi 60]

Originally Posted by Kenomac

The closest thing I could find to what you’ve described looking online for a self-priming salt water trash pump capable of the volume you claim, is a .....]

might be something here
https://mvdirona.com/2017/04/fighting-water-ingress/

[Kenomac]

Originally Posted by Simi 60

might be something here
https://mvdirona.com/2017/04/fighting-water-ingress/

But the largest pump on your list only moves 6,000 gallons per hour. Dockhead claims his “trash pump” moves 44,000 gallons per hour, which would require a massive size, weight, hose size and cost increase to go along with that sort of capacity.

[fish53]

Originally Posted by IslandHopper

The trash pumps we have on our work vessels are all Diesel and if i was going to have one on my boat it would be the same, can't see the point in Gas (petrol) or electric....

Similar type units to these...

https://www.riequip.co.nz/shop/Buy+W...rash+Pump.html



Plenty of options if you have the space.....
https://www.google.com/search?rlz=1C...YRZprU#imgrc=_

Nice but for many not very realistic. This is much like discussing firefighting equipment, you certainly need some but if your boat has limited space as many do piling safety equipment in every available space makes no sense. Sure I'd like a dewatering pump and I'd like an SCBA but if the dewatering pump is on top of the SCBA when I need it I may succumb to smoke inhalation before I can don it. The same with having some sort of station bill describing duties and muster locations, my boats 28 feet you'll know where to be because I'll tell you. No just having a buttload of safety equipment doesn't make you safe, having the right equipment for all purposes appropriate for the vessel that's going to carry them and the knowledge to use them to best affect is in my opinion best. I find this interesting in a thread where some decry the inconvenience of carrying a life raft to much to tolerate.

[IslandHopper]

Originally Posted by Kenomac

The closest thing I could find to what you’ve described looking online for a self-priming salt water trash pump capable of the volume you claim, is a 4 inch electric pump weighing 350 pounds costing $2200-over $3,000 that can handle 44,000 gph, everything else is twice as heavy, twice as large and more expensive.

https://pumpbiz.com/manufacturer/amt...p-15hp-4872-95

^^^ And that bad boy in the link is 3 Phase ^^^

Gallons Per Hour: 39600 (660 GPM)
Voltage: 208-230/460 Phase: 3
Horsepower: 15

..............should dim the lights a bit