small boat buoyancy repurposed 2 liter bottles

[Landrith]

I have seen some old brown foam in production fiberglass boats that seems to have lost its buoyancy over decades. I know white styrofoam loses its buoyancy from gasoline and solvent spills. I have plenty of 2 liter bottles. Any thoughts to the wisdom of under floor buoyancy for a self bailing deck of a small power skiff. At least their necks could be securely tied and they could be contained between stringers or frames, sole and hull. If the boat is not wrecked (my fear of light plywood air chambers which also prevent good access to the inner hull when sealed).

I remember the Rothschild that sailed on the 2 liter engineless catamaran built of bottles. I don't have that many. lol. And I do not think fuel was a worry of his crew.

[JimConlin]

I’ve got a few vinyl beach balls stashed away in random spaces.

Does anyone know of a brand of beer whose containers are resealable?

[NeilMB]

Does anyone know of a brand of beer whose containers are resealable?

Grolsch and other swing-top glass bottles are re-sealable and quite airtight, but I doubt they have positive buoyancy given the weight of the glass.

[MushCreek]

I had a buddy that added flotation to a cabin cruiser by filling up the spaces with gallon plastic milk jugs, and then used pour-in foam around them. It saved a LOT of expensive foam. I always thought is was a good idea. 2 liter soda bottles are surprisingly tough. We tried to break one once, filling it with water and tossing it off of a tall building, driving over it with a car, etc., and it was nearly indestructible. It would take a pretty serious collision to compromise them.

[Peerie Maa]

Check that they do not collapse under external pressure.
Ping Pong (table tennis) balls make good buoyancy. They have a better packing ratio than bottles.

[Rumars]

For securing, get a piece of heavy duty netting, tie them individually to the mesh, then wrap them with it.
For packing ratio, there are rectangular and even hexagonal bottles, as there are different sizes.
For collapsing, buy a bag of dry ice, drop some into the bottle, screw the cap on.

[StevenBauer]

Check that they do not collapse under external pressure.
Ping Pong (table tennis) balls make good buoyancy. They have a better packing ratio than bottles.

This doesn’t seem like a good idea to me. Table tennis balls are made of celluloid and are extremely flammable. Not to mention expensive.

[P.I. Stazzer-Newt]

Check that they do not collapse under external pressure.
Ping Pong (table tennis) balls make good buoyancy. They have a better packing ratio than bottles.

Spheres have a 3d packing ratio of only 74% - cylinders make pi/root12 or nearly 91%

[johngsandusky]

I once made amas for a quick and dirty canoe from 2x2l bottles taped to the ends of an 8' 2x4. You could stand in the flat bottom canoe with only a 24" beam.
My now deceased kit built Folbot Super had gallon milk bottles in the ends, and I've used dollar store kickballs in a canoe. Your soda bottle idea will work, watch that they don't crack or chafe over time.

[woodpile]

The closed cell insulation foam from big box stores comes in varying thicknesses and is very east to cut to fit odd, shaped spaces.

[Peerie Maa]

Spheres have a 3d packing ratio of only 74% - cylinders make pi/root12 or nearly 91%

Was that cubic packing or hexagonal?
Ping pong balls fit into those corners that liter bottles do not reach.

[Peerie Maa]

The closed cell insulation foam from big box stores comes in varying thicknesses and is very east to cut to fit odd, shaped spaces.

Once it is cut to fit, put it into a robust airtight plastic bag.

[kbowen]

Any thoughts to the wisdom of under floor buoyancy for a self bailing deck of a small power skiff (?)

As I was planning my boat a naval architect pointed out that disaster flotation should include a lot of closed volume high up in the hull, and that stuff under the floorboards could re-capsize the boat when it filled with water. So I created storage areas under the side decks with home-made hatches. They are not totally watertight, but when I did a capsize test there was only a bit of water in each compartment when I got the rest of the boat bailed out. I also use 2 beach rollers for fenders and I tie those up under the side decks when under way. The boat is stable upright when swamped, and I can bail it dry.

Ken

[Merlin4550]

We have put plastic water bottles into small garbage bags until the particular space is filled, then tie the bag itself tightly. It makes for pretty efficient filling of empty areas, and can also be removed very easily if needed.

A harbor guy recommended we scrunch the bottles very slightly before screwing their lids on, because hot temperatures can inflate them. Not sure if it's needed in Michigan, but why not?

[sp_clark]

This doesn’t seem like a good idea to me. Table tennis balls are made of celluloid and are extremely flammable.

That (italics mine) may have changed (at least here in the USA) some years ago. ABS is the newer, safer material now used for those and a whole lot more things we mostly take for granted like some piping used for plumbing.

Nitrocellulose (celluloid is a mixture of this and camphor) was commonly used for all kinds of things over a hundred years ago but that's no longer the case owing to its tendency to burn with vigor once ignited.

[SalsDad]

For my Diablo (RIP) and a couple other boats, I filled the seat compartments with 1 and 2-liter bottles. They fit in through 6" access hatches, and allow drainage/ventilation of the compartments without sacrificing too much buoyancy. The other advantage to "scrunching" them a bit, is they can deform a bit to pack tighter.

Not sure I would foam the bottles in place, but that works good with the lumberyard panels, or - cheaper around here - washed up dock flotation, cut with a handsaw. Not sure what is the point of putting good quality foam in a bag....

Alas, when my bride first visited the barn, she was unimpressed with hundreds of empty soda bottles, amid the porcupine poop, nasty old dock foam, yogurt cups, boat hardware (with 6" squares of deck still attached), rope ends, old wood stove parts, and other treasures. Its is all gone now, and I fear I will never again amass such a collection of useful items...

[Landrith]

Alas, when my bride first visited the barn, she was unimpressed with hundreds of empty soda bottles, amid the porcupine poop, nasty old dock foam, yogurt cups, boat hardware (with 6" squares of deck still attached), rope ends, old wood stove parts, and other treasures. Its is all gone now, and I fear I will never again amass such a collection of useful items...

I awaken at night with that fear! I have relocated my bottle stash to the barn at the family farm.

[CaptChap]

Grolsch and other swing-top glass bottles are re-sealable and quite airtight, but I doubt they have positive buoyancy given the weight of the glass.

As a far, far aside - this mention of Grolsch beer bottles brings back memories of once, in my much younger days as a struggling medical researcher, I decided to try brewing my own beer (with the help of a friend/biologist/neighbor), and since we were too cheap to buy a bottle-capper device, we decided to just frequent our neighborhood (Coconut Grove, FL) bar which happpened to serve Grosch. We asked the bartender to save us the empties, and we made a habit of drinking our share there almost every night, until we soon had 48-50 or so bottles, complete with the little red rubber seals and white ceramic caps. Long story longer, we did our home-brew, and it was so good that we continued making batches which were consumed all too quickly (also won best in the local Miami Home-Brew competition that year...as an "ale"!). Sweet memories!

[Yeadon]

As I was planning my boat a naval architect pointed out that disaster flotation should include a lot of closed volume high up in the hull, and that stuff under the floorboards could re-capsize the boat when it filled with water. So I created storage areas under the side decks with home-made hatches. They are not totally watertight, but when I did a capsize test there was only a bit of water in each compartment when I got the rest of the boat bailed out. I also use 2 beach rollers for fenders and I tie those up under the side decks when under way. The boat is stable upright when swamped, and I can bail it dry.

Ken

On my Bartender build, the plans call for lining the underside of the decks with closed cell foam. The plans roughly describe exactly what you've said here. I'm using the 2" pink Foamular closed cell foam that you can buy at the big box stores. It'll be glued in. I'd use a glue like this.

The use of bottles, ping pong balls, etc, always seemed really janky to me. There, I've said it. I've used Bomar hatches on air tight tanks. Together they're the buoyancy needed in capsizes. I do think a builder could use Foamular sheets, cut out rough shapes and then glue them together into the general cubic volume needed. Then you could carve the whole block into the right shape.