Buoyancy from bottles...but do they degrade?

[dancrane]

Very good points, thank you. LW395 mentioned the kicking strap today, too...it hadn't previously occurred to me what a difference that must make, though I can see why it does.

I've spent plenty of time sitting without much noticeable effect, on the end of centreboards, on smaller boats than the Osprey. I'm really not nervous of capsize - I'm just keen to pre-empt the difficulty of the event, by ensuring I can right her unaided when she goes over, without waiting for some helpful chaps in a RIB. Ultimately it'll be no difficulty for me to arrange a boatload of keen sailors to assist with a test, but I was thinking beyond the test - because it's perfectly possible the test will show I cannot easily raise her as she is.

A lead centreboard was an idea in that direction, because I'm concerned that even using all known techniques, my 70kgs may not suffice in the leverage department.

But it's difficult to raise the subject without inviting a chorus of incredulity about my odd choice of singlehander...so I persist with ideas which don't make sense to most folk here.

I've actually no wish to besmirch a nice old pure racing boat with weird overweight assemblies and tackles. As you say, good sails and foils count for more, giving controllability...

...and I really ought to invest in a drysuit so my hands-on experimentation can begin mid-winter.

 

[Daydream believer]

.

A lead centreboard was an idea in that direction, because I'm concerned that even using all known techniques, my 70kgs may not suffice in the leverage department.

If the centre board is lead filled you will not get it up easily so when/if you capsize you will not be able to raise it easily
The point about raising it is that with it down the boat cannot slip sideways & the sails tend to fill with wind ( letting the kicker off helps prevent sails filling)If the sails fill then the windward rail lifts so it is harder to get back on.
If you can get your weight on the windward rail & the sails are not filled it should drop down to you & you just roll aboard.
70Kg is more than enough to right the boat. you can always get hold of the jib sheet & use it to allow you to move out to the end of the board to use your weight to the best effect.

You will need a fairly long tiller extension to allow you to get onto the trapeze. You could get 2 & fix them at 150degrees to each other so you do not have to tack the extensions when tacking the boat. Also you can grab one as you get on & bear the boat off a bit to stop it just luffing & tacking on you & capsizing again

 

[dancrane]

70Kg is more than enough to right the boat. you can always get hold of the jib sheet & use it to allow you to move out to the end of the board to use your weight to the best effect.

Thanks for that, D.B. I'm keen to believe it, I'll be very glad to report it too, once I get the drysuit.

I read of Progrip being stuck round the bottom six inches of a centreboard to make it easier to get as far out as possible. Makes some sense, except...non-slip below the waterline?

 

[Daydream believer]

Thanks for that, D.B. I'm keen to believe it, I'll be very glad to report it too, once I get the drysuit.

I read of Progrip being stuck round the bottom six inches of a centreboard to make it easier to get as far out as possible. Makes some sense, except...non-slip below the waterline?

Ruins the flow round the board
You would be better spending the money on a set of decent sailing shoes with good grip

 

[DaveS]

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.

An alternative (or a supplement to rigid bottles for those areas against the hull) is inflated wine box inners. Lighter than plastic bottles and, if not blown up too hard, readily conform to fill any shape. I have used these many years ago for just this purpose, but they were not put to the ultimate test so cannot say how effective they would be in extremis.

 

[dancrane]

An alternative is inflated wine box inners...

Begging your pardon, Dave...isn't there another reason for choosing that option?

 

[DaveS]

Begging your pardon, Dave...isn't there another reason for choosing that option?

Oh, yes...

 

[prv]

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.

I suppose it would look somewhat like the time we filled a friend's car with thousands of rubber ducks:

Pete

 

[dancrane]

Looking closely, I spy balloons under the ducks, obviously added to bulk-out the void. And seeing that it's a convertible, wouldn't the ducks lift the canopy off the car anyway?

And I'm not convinced there's adequate access to the pedals for safe driving...in the field of amphibious cars, this looks to have come from the drawing board of Richard Hammond.

 

[prv]

Looking closely, I spy balloons under the ducks, obviously added to bulk-out the void. And seeing that it's a convertible, wouldn't the ducks lift the canopy off the car anyway?

And I'm not convinced there's adequate access to the pedals for safe driving...in the field of amphibious cars, this looks to have come from the drawing board of Richard Hammond.

Yep, it's true, we cheated slightly by stuffing the footwells with a couple of balloons - also because some people in the team were concerned that the ducks might find their way up into the pedal workings or behind the dash, and cause problems unspecified. But it was only three or four balloons in each footwell, promise - the rest was genuinely a pile of 3,600 rubber ducks.

Oddly enough, buoyancy and driveability were not among the desired effects.

Pete

 

[dancrane]

Four months later, and my bottle collection is now up to over ninety, good for around 1800N of buoyancy...

View attachment 41637

...and they only weigh about 4kg. At this rate, by the time my boat has gained 6 or 7 kilos, every cavity aboard will be stuffed with eco-friendly tough plastic unsinkability. :encouragement:

 

[LittleSister]

You are concentrating on the buoyancy of the bottles, but seem to have overlooked the lack of buoyancy of the space between them. You will get much more buoyancy from a properly sealed compartment. Filling it with bottles will only seal a portion of the space.

 

[dancrane]

That's a bit negative isn't it, L.S? The 2l lemonade bottles are squashy enough to dominate the volume of any tight area where several dozen of them are placed. And surely it's much easier to retain individually sealed containers behind an existing bulkhead, than to totally seal the bulkhead itself?

My boat's a dinghy which has had some of its bulkheads messed about - so the bottles are simply an economical plan to prevent wholesale swamping.

 

[LittleSister]

That's a bit negative isn't it, L.S?

It certainly wasn't meant that way.

 

[dancrane]

Thanks, no offence taken.

Really, it's surprising how small a proportion of any given space can't be filled by these round, vertical-sided bottles. Placed as in my photo above, the space between any three is tiny - probably less than 300ml per 6000ml of space occupied by the surrounding bottles. And that's without squeezing them to mould into bulkheads and corners.

 

[jimmcgee]

that picture has just told me how to store all my 2 ltre homebrew bottles neatly , thanks Dan :encouragement:

 

[dancrane]

Yes, they stack quite well, but you need to maintain tension round them - and have enough length of line to let you to add more empties - otherwise it can all go very wrong...

View attachment 41644

 

[jimmcgee]

thats what they look like just now , and the wifes not happy

Yes, they stack quite well, but you need to maintain tension round them - and have enough length of line to let you to add more empties - otherwise it can all go very wrong...

View attachment 41644

 

[dancrane]

Yes, I had just been very smug about how tidily they all fitted together, and how neatly they fit in the airing cupboard, when I saw that one bottle was sticking out a trifle too far...

...I nudged it back in, and the whole magnificent translucent monolith fell into a horrid untidy pile of recycling. Surprisingly, I was able to build it back into shape in under ten minutes.

As long as the tension is maintained on the cord, it's possible to carry them around, without collapse. Quite fashionable too. But, very important to lie the pile flat when adding bottles.

As mentioned in this thread last year, I've found the bottles look and stack much better if their internal pressure is high - so each of mine spent 30mins in the freezer before stacking.

What? That's not weird, is it? Not really.

 

[oldsaltoz]

Surprised no one mentioned the pool sticks.
They have been used to stuff the area between deck and hull on small power boats for many years, they are closed cell so do not rot or absorb moisture.

Good luck and fair winds.