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Author Topic: Dont sink.  (Read 2286 times)

Just Add Water

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Dont sink.
« on: July 26, 2015, 03:36:53 PM »

I have been looking up a bit of science on floatation today cos the weather is poo.

So Most chaps use pool noodles in there power boats to keep them afloat, I have just purchased one 4ft long and 2 1/2 ins dia,  this is said to keep 15lb afloat and my boat tips the kitchen scales at 16lb.

I am thinking with the radio box sealed, and a bit of bulkhead at the front with foam balls then I should be OK 8) I am not planning to try it out, but wondered what you all think about my less than scientific calculations.

By the way there is a 2 inch gap behind the exhaust pipe to the noodle.

Bernie.
 
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Shipmate60

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Re: Dont sink.
« Reply #1 on: July 26, 2015, 07:06:48 PM »

You could fit a nice bag filled with polystyrene balls in the gaps.


Bob
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Jerry Hill

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Re: Dont sink.
« Reply #2 on: July 26, 2015, 11:02:23 PM »

My thoughts, I'd sink it and find out. Corrosion X the engine's electrics, and block the diaphram vent hole to make your life easier. I'm saying this because in my recent entry to petrol boats I've had many inversions and total sinkages, it's no big deal to clear the engine and get going again, so it shouldn't be a big deal to do this on purpose to have that total sense of surety.



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derekwarner

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Re: Dont sink.
« Reply #3 on: July 26, 2015, 11:28:01 PM »

Bernie.....initially I was with science and Bob on this...there is no reason not to believe that bloke who said 'Eureka'

However there is that finely established line between positive buoyancy and sinking

The foam manufacturers spiel 'that it keeps 15lb afloat' needs clarification and understanding........the thought or concept that this same foam material would preclude a 15lb model from sinking may be valid, however is sinking to an unrecoverable depth your concern?. :o.. or are you assuming that the vessel will not fill with water?

That 2" gap between the muffler & the foam noodle when measured in the kitchen is filled with air, however if water entered the hull that same space is now filled with the same weight of water that occupies that space....the same applies to each and every air void in the hull

Maybe some more thought is required %) ......Derek
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NoNuFink

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Re: Dont sink.
« Reply #4 on: July 27, 2015, 12:38:42 PM »

Just FYI

A quick back of the envelope calculation for the floatation effect of a cylinder of 2.5" diameter x 48" long gives me a figure of about 8 lbs so you would need at least two of them anyway.

The volume of the cylinder is 3861cu cms approx.  Archimedes tells me that amounts to 3.861 kgms of lift whiich is about 8.5lbs.  Further more that assumes that the foam remains cylindrical (i.c. not compressed). does not absorb any water and weighs nothing.

NNF

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rickles23

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Re: Dont sink.
« Reply #5 on: July 27, 2015, 03:14:31 PM »

Hi all,
Is it possible to weigh the boat

Get something that weighs the same

Attach to noodles

Test.

Regards
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Shipmate60

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Re: Dont sink.
« Reply #6 on: July 27, 2015, 04:07:20 PM »

You are assuming that the whole hull would fill with water without ANY air pockets.
Nothing to stop you  blanking off the whole bow section or filling with bags of polystyrene balls which will ensure that the bow would remain above the water.


Bob
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Just Add Water

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Re: Dont sink.
« Reply #7 on: July 27, 2015, 04:26:49 PM »

You are assuming that the whole hull would fill with water without ANY air pockets.
Nothing to stop you  blanking off the whole bow section or filling with bags of polystyrene balls which will ensure that the bow would remain above the water.


Bob




Yes the bow has a small bulkhead with balls in it.
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Just Add Water

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Re: Dont sink.
« Reply #8 on: July 27, 2015, 04:28:35 PM »

Hi all,
Is it possible to weigh the boat

Get something that weighs the same

Attach to noodles

Test.

Regards



That is my first plan because the deepest part of our lake is 16 feet so no chance of getting my feet wet. no no.
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w3bby

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Re: Dont sink.
« Reply #9 on: July 27, 2015, 05:22:03 PM »

..... Nothing to stop you  blanking off the whole bow section or filling with bags of polystyrene balls which will ensure that the bow would remain above the water.

Not my first choice as it puts the radio box relatively deep under water when the hull is vertical. I prefer that the boat floats low in the water and level. This reduces the chances of major damage if the boat is hit by another boat and reduces the pressure on the radio box, giving it a good chance to do its job and keep the radio gear dry.

Don't forget to attach flotation to your cowl as well, nothing worse than see it detach from the hull in a blowover and disappear.....
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