Buoyancy from bottles...but do they degrade?

[dancrane]

This isn't about the bottles I put at the top of my mast for anti-inversion.

SWMBO and I get through quite a few of those big two-litre fizz bottles, and I've noticed many times how extraordinarily tough they are. As a frustrated teenager many decades ago, I walloped an empty one repeatedly in my father's garage with a baseball bat. The bottle didn't turn a hair; the bat snapped.

So, they're very lightweight, very tough, big enough to represent practically-useful measures of buoyancy, and free.

In recent months I've accumulated at least forty. When I reseal my rear cockpit bulkhead, I have it in mind to strap them in the compartment as positive buoyancy. But...

...some, I left on the boat on hot July days, when the pressure was high. Now, in the cold, they've gone all flobby...there's no pressure in them. Granted I can put them in the icebox for a while with the lid off, reseal them when I take them out and effectively 'repressurize' them, although there'd be no measurable point in doing so...

...but my concern is that wrinkles in the plastic seem far weaker than in unwrinkled, pressurized bottles. So I'm wondering if, over six months, the plastic has degraded?

Not much benefit in stowing a stack of cracked bottles as buoyancy. Any idea if they're as tough after years in a hot/cold dark place, as when they're new?

 

[Nigel-in-Oxford]

Had a load in my wayfarer for years, took them out when I sold her, apart from the mould they were fine.
I used the freezer to pressurise them.

 

[dancrane]

I used the freezer to pressurise them.

Thanks Nigel, I was afraid I'm turning stupid! :encouragement:

At least if I am, I'm not alone.

Glad to know they're a workable solution. Better than expensive yellow inflatable tanks really - if they puncture, all buoyancy is lost...if a bottle cracks, it's only 20 Newtons gone.

 

[Deleted member 36384]

They can withstand hot weather without fear of bursting, the PET bottles (Coke and such like) are designed to withstand 150 psi according to the internet. They need to be secured strongly as under pressure they will behave like cats if there is a way out from the boat.

 

[dancrane]

Not meaning to give a more weird impression of my home life than is accurate, but in an idle moment the other day, I took three empty ones out of the freezer, put the lids on and waited till the ambient temperature brought the internal pressure up, then placed them lying down, each a couple of feet apart on the floor...

...then I lay down on them and asked SWMBO to pull me along, in the reputed style of Stonehenge sarsens. She said I might have been a wheeled cabin-bag, it was effortless.

Made me think they'd be usable for moving the boat over level surfaces, if no other means was available.

 

[Stork_III]

Not meaning to give a more weird impression of my home life than is accurate, but in an idle moment the other day, I took three empty ones out of the freezer, put the lids on and waited till the ambient temperature brought the internal pressure up, then placed them lying down, each a couple of feet apart on the floor...

...then I lay down on them and asked SWMBO to pull me along, in the reputed style of Stonehenge sarsens. She said I might have been a wheeled cabin-bag, it was effortless.

Made me think they'd be usable for moving the boat over level surfaces, if no other means was available.

Don't worry, nothing you can say will make us think you are any more wierd than we do already. :encouragement:

 

[DownWest]

When I had my little boat surveyed for insurance, the guy asked if I had foam in the forward compartment. Nope, says I, just sealant round the hatch. He suggested water bottles (normal 1.5lt, not pressure drinks jobs) as the best solution. If you keep them out of the sun, degredation is minimul.

 

[dancrane]

I think they're very useful, pity they're mostly just tossed, very often not even recycled.

Imagine, they could have emptied the drinks-store of the Costa Concordia and made a raft.

Although on reflection, that ship didn't actually sink very far.

I've often wondered what there was aboard the Titanic which might have kept a few souls afloat and alive, notwithstanding the cold. How many beer-bottles could have been emptied, re-corked and put in a big trunk or laundry hamper? Although the White Star line would probably have preferred it to go to the bottom rather than be used 'inappropriately'.

 

[rotrax]

I believe a Scottish motor boat company uses 2ltr. drinks bottles as underfloor buoyancy on new builds. They got a prize for enviromental dilligence IIRC.

 

[dancrane]

Impressive... ...I didn't know there are any Scottish motor boat companies.

The bottles make quite a lot of sense I think. If you own an old boat and you've ever wondered how she'd respond to a crunch with something solid below the waterline, it'd probably be some reassurance to have filled all the underfloor-spaces with tough little air chambers which hardly weigh anything and cost nothing...

...as long as the floors are screwed down tight.

A good thing about the 2-litre bottles is that the curved wall easily squashes to fit flush into any space where it's placed. At a wild guess, I reckon the 2-litre size weighs up to about 25 grams empty, whilst offering 80 or 90 times that much buoyancy. Better than blocks of polystyrene which seems to absorb water over time.

 

[Pete7]

Dan, what you need is plastic ducks. From mid Pacific they have reached Europe:

http://www.mnn.com/earth-matters/wi...00-rubber-duckies-lost-at-sea-teach-us-about-

Pete

 

[dancrane]

Indeed, very deceptive - if they weren't quite cute, their diaspora would be a frightening indication of the consequences of pollution at sea.

Of course, if one had seven thousand rubber ducks wedged behind the saloon berths and under the floor, and in that weird cavity between the fridge and the quarter-berth, a part of you would slightly be hoping to be caught on film, the day a falling crane smashes the boat in two and the ducks come out to play.

 

[Baddox]

Balls

Plastic, play pit ones that can be bought by the bagful from toy shops are also recommended to adding buoyancy to areas that may flood.

 

[nigelmercier]

I took three empty ones out of the freezer, put the lids on and waited till the ambient temperature brought the internal pressure up, then placed them lying down, each a couple of feet apart on the floor...

...then I lay down on them and asked SWMBO to pull me along, in the reputed style of Stonehenge sarsens. She said I might have been a wheeled cabin-bag, it was effortless...

Thank you, you've just solved my problem of how to move my shed.

 

[Seajet]

If planning on getting the boat up beaches for picnics etc ( ! ) a couple of small fenders are handy rollers, and make some buoyancy in the meantime - the comments about securing such things are serious - heavier than lemonade bottles ( I'm knee deep in those too ) but probably more durable.

They can even be hung over the side if alongside another boat or jetty, though a buoyancy aid usually works.

Now we can start a thread on ' why do old fenders go sticky '...

 

[dancrane]

Thank you, you've just solved my problem of how to move my shed.

Hmm... I expect it could work! Especially if you have one of those little pumps they used to sell to re-pressurize fizz bottles...the deflated bottles slip under the shed, flat, you pump them up, then...prepare for rolling thunder. Well, slight movement, anyway. Don't count on it, though.

 

[markhomer]

why bother with stuffing bottles in boat , when you can :

http://www.bbc.co.uk/news/world-asia-pacific-10759623

 

[Daydream believer]

if the space you intend to fill with bottles is airtight anyway then why bother with bottles
My phantom has nothing inside the tanks
But then I do not intend to go ramming things & making holes
Even if you do ding a hole in the tanks you will not sink completely, just take a few gallons on board

That said I did hit a squib with my Shearwater once & that sank

 

[dancrane]

My phantom has nothing inside the tanks...But then I do not intend to go ramming things & making holes

I guess you don't wear a seatbelt either, because you don't intend to crash? I know what you mean, though...a sealed tank which is holed, is most unlikely to fill and sink...

...but on my boat, the compartment concerned is a gaping hole cut in the rear cockpit-bulkhead by a previous owner. Long story, but the Osprey Mk2's rear compartment was originally designed to be air-tight. Once I've put the bottles in, I plan rebuilding the bulkhead, with tubes to the transom (for which purpose the bulkhead was clumsily cut away)...

...so technically the compartment won't be at risk of taking on water, but I don't trust my workmanship that much...and when the bottles are free, and practically weightless, and won't be visible...I thought, why not use them to prevent swamping?

Phantom...nice boat. :encouragement:

 

[Daydream believer]

I guess you don't wear a seatbelt either, because you don't intend to crash? I know what you mean, though...a sealed tank which is holed, is most unlikely to fill and sink...

Phantom...nice boat. :encouragement:

For the record - I ALWAYS wear my lifejacket on my hanse 311. I always hook on going forward, I have a life raft on my cruiser.
My squib does have bouyancy tanks- But i have not looked inside!!

I have to sy you sound very nervous of your Osprey
they are beautiful boats & very stable, good performance
talk of lead centreboards etc will just ruin performance & oddly enough stability
A boat that goes forward rather than sideways is actually easier to sail as it releases wind easier
i would suggest that you should look at good quality foils & sails
As for stopping the complete inversion an inflatable sock ( can be purchased I have seen them & know someone who used it in a 505 successfully)
You need to practise capsize & how to right
Remember to release the kicking strap before righting also when upright lift the centreboard - so you need to be able to reach the control from the water
If you have difficulty getting aboard wear a capsize loop or rig a footline along each side