Positive flotation in 'bigger' boats . . .

[Grandad]

Re: Positive flotation in 'bigger' boats . . .

One point that complicates things is that for flotation to be of net benefit, it has to actually displace water, meaning that until it is submerged, it's only added weight, however slight. Putting all the flotation low in the vessel, if that was possible, would ensure the greatest benefit. The problem that I see, is that once submerged, balance becomes critical and the boat will likely roll over. The heavier superstructure without flotation will of course hold the boat upside down while passengers are left clinging to the slippery hull. So the trick would be to provide as much flotation as possible in the gunwales to form a stable perimeter. Next, your stern is far heavier, so the bow maybe the only part sticking out of the water, unless you pack flotation around/above the engines which is usually not practical. Ya, I think on a larger boat, I'd invest in an emergency inflatable or carry/tow a RIB that could also be used for gunkholing in the shallows. - Grandad

 

[jigngrub]

Re: Positive flotation in 'bigger' boats . . .

The problem that I see, is that once submerged, balance becomes critical and the boat will likely roll over. The heavier superstructure without flotation will of course hold the boat upside down while passengers are left clinging to the slippery hull.

So the boat is going to roll over like this one did?
Lund Boat Floatation Video - YouTube

 

[smokeonthewater]

Re: Positive flotation in 'bigger' boats . . .

fwiw, fuel is lighter than water and will provide some boyancy thus weight of fuel does not get counted on the negative side....

Personally I think that the manufacturer is FAR better equipped to determine where and how to place flotation... as mentioned above adding it in the wrong place could actually cause problems. A swamped/sunk boat in waves could pose more danger than it's worth for people in the water.... comfortable (inflatable) pfd's that will actually be worn, a life raft/dingy, and an epirb would be my choice way before adding foam.

 

[Home Cookin']

Re: Positive flotation in 'bigger' boats . . .

the whole notion of adding floatation to a professionally built boat is just silly. Why not install two 30' pontoons like outriggers? Add a second hull like on a tanker? A giant balloon on the superstructure so it won't roll?

Seriously. This is the stuff people dwell on in February after being stuck inside and on land for months.

Positive floatation is a false security anyway especially in cold (<50*) water. Just makes it easier to know where to start looking for the bodies. very very few boats by design stay upright. Most roll like a swamped canoe and leave a small amount of bow sticking up. I have experience with this.

 

[jigngrub]

Re: Positive flotation in 'bigger' boats . . .

. very very few boats by design stay upright. Most roll like a swamped canoe and leave a small amount of bow sticking up. I have experience with this.

Uh... yeah, those would be the poorly designed entry level boats of yesteryear.

Did you even watch the 2 videos I posted? There are lots more too:
unsinkable boats - YouTube

Todays boats with positive floatation are both nearly unsinkable and self righting. Boat design and manufaturing has come a long way since the old "Flippers" were built.

How about a self righting unsinkable 44 footer?:
Coast Guard Response Boat Self-Righting Test - YouTube

Sure, not all boats are made like this, but there are a lot of them out there that are.

... and it also depends on how well a boat has been taken care of and maintained, a boat with saturated floatation foam will float like a granite rock. But there are boats out there today that won't even take on enough water to get your feet wet when the floatation foam takes over... believe it or not.

 

[tpenfield]

Re: Positive flotation in 'bigger' boats . . .

Yea, I'm not planning on living in the thing if it were to become swamped, but just to stay up at the surface so I can resuce the beer and chips. :joyous:

In any kind of rolling sea, it will probably roll over at some point. . . . Visions of those 4 football players who swamped their boat in the Gulf of Mexico a few years back come to mind . . . and the one who managed to stay with the boat.

It seems that there is no clear definition of what positive flotation means . . . vaguely, one would think that it means 'not sink' (that would be negative flotation, wouldn't it?), . . . but has to how well it does 'not sink' is where things get fuzzy.

 

[jigngrub]

Re: Positive flotation in 'bigger' boats . . .

Remember this thread penfield?

http://forums.iboats.com/boat-topic...-topics/sons-cigar-boat-goes-down-564062.html

Could've been a real tragedy had it been in deeper water.

 

[tpenfield]

Re: Positive flotation in 'bigger' boats . . .

Remember this thread penfield?

http://forums.iboats.com/boat-topic...-topics/sons-cigar-boat-goes-down-564062.html

Could've been a real tragedy had it been in deeper water.

I don't remember that one, but definitely would have been more of a people problem in deeper waters. I see the thread got closed due to name calling. . .

 

[tpenfield]

Re: Positive flotation in 'bigger' boats . . .

I just got another email from Formula boats . . . I must say that they are very prompt at responding, etc.

The final word is that they do not test nor certify the boats over 26 feet for positive flotation, so it is not known for sure. They said that they have seen them go down past the gunwhales, but not completely sink.

Anyway, I will plan on adding somewhere between 24 and 32 cubic feet of flotation over the winter, as I usually get really bored around February.

 

[jigngrub]

Re: Positive flotation in 'bigger' boats . . .

The only way to positivly find out if your boat has positive floatation would be to test it, and for some reason I don't think that's going to happen.

You can get the 40 cu. ft. kit of 2 lb. foam from USComposites for $264, about the cost of a half of a tank of gas for that boat.

Playing with that foam should be fun and provide you with several hours of entertainment in the cold dark months ahead.

 

[25thmustang]

Re: Positive flotation in 'bigger' boats . . .

My old 29'er was claimed to have positive foam flotation and not sink. I did find foam throughout it when doing my work. Quite a bit of it up high on the hull sides more towards the stern.

My new 34'er would sink.

Sounds like if you have the room it might add a little sense of security to add the foam.