Buoyancy bags

[fisherman]

Looking for some: they seem to be expensive on ebay, got one, but it has a pinhole leak, so not the best.
Spend the wee small sleepless hours wondering what else would do. A 6in sewer pipe is 17.6kg per metre, could use glued stopends, but a bit heavy.
At the moment I have 120kg worth of danfenders jammed under the seats, which worked under test in quiet water. Being a traditional shape the boat sinks upright, but is just a bit too awash for security.

 

[Wansworth]

Had an old boat years ago,put lots of insulating under a raised floor,continuous little white beads,don’t know if it would have worked

 

[fisherman]

My IP12 GRP punt has a screwed down floor with 44 lidl 2 litre water bottles under it. Not done a test.
I've seen some disasters with 'sealed' ply/grp decks: inevitably there is a leak, keel bolt or pinhole somewhere, and the deck breathes in temp changes, blowing out air and sucking in water. If there is two pot foam it gets waterlogged, and extensive research says none of it is closed cell. Best is a void, with a drain bung to a sump somewhere.

 

[Wansworth]

Be a man,your ancestors with their leather boots and tarred waterproofs would think nothing of setting off into a gale in your punt,buoyancy is for loosers?

 

[fisherman]

I've been a man for seventy years, I'd just like to be one for a few more!
Always fancied those leather boots mind.....

 

[lw395]

My canoe has a rubble sack containing oddments of polystyrene packaging at each end.
Soft drink bottles are an option. The innards of wine boxes.
Some racing dinghies still use buoyancy bags. Merlins for instance. Some of them cover the bag with a laced-down canvas cover which keeps the bag lower in the boat and the boat less low in the water. You could use such a cover over any buoyancy I suppose. Basically if the bag rises an inch from the floor, the boat goes down an inch. Ever inch matters when it comes to sailing a boat out from a swamping!

 

[fisherman]

The physics intrigues me. Once having sunk the boat it had about 9 in freeboard. Some of the buoyancy came adrift and floated up: the effect if you analyse it, is, the water level in the boat drops as the air space comes out of the water making it theoretically more stable. As long as there is no exchange of water inside to out or vice versa. All the buoyancy does is deny the water somewhere to be.

 

[William_H]

If Fisherman is asking about his traditional shaped boat (not his punt) then I think the best bet is sealed tanks which are made up of the seats/bunks of the boat. ie along the sides. If it is too hard to seal them then use bags or bottles. The important thing is to keep the buoyancy at the sides. This will aid stability. If water in flooding can slosh to the sides then self righting gets lost. This can happen if buoyancy is in the centre line of the hull. In any case buoyancy must not be used to permanently seal the area as you you need access into the area for cleaning drying etc. So no foam. ol'will

 

[coopec]

I've often thought about this myself.

Surely heavy inflatable bags keeping the yacht afloat would be a better bet than a liferaft? (Automatically inflated from an air bottle)


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Jul 16, 2016 - 25 posts - ‎18 authors
Im exploring the idea of fitting Hypalon inflatable fenders as flotation ... Always thought self inflating makes sense for a bigger boat though.

 

[ltcom]

So many liferafts are thrown away.could the tubes not be repurposed for buoyancy bags?

 

[michael_w]

The fabric Crewsaver bags are much tougher than the plastic Holt ones.

 

[fisherman]

Its the 15ft sailing rowinbg oyster punt seen in the sea trials thread.

 

[Rocksteadee]

Start collecting 1.5 l fizzy bottles. They can take a bit of pressure and each one is a bouancy aid in its own right

 

[Wansworth]

Its the 15ft sailing rowinbg oyster punt seen in the sea trials thread.

Mere detail?

 

[fisherman]

Start collecting 1.5 l fizzy bottles. They can take a bit of pressure and each one is a bouancy aid in its own right

See#3

 

[awol]

Wine in 10l boxes has a metallised plastic bag with a tap - a mere 100 of those and you have a tonne of buoyancy and possibly a sore head.

 

[Rocksteadee]

Sa

See#3

Saw that. I was just noting that an area filled with 1.5 rather than 2 will give more as getting more in due to the smaller gap between bottles and that water bottle caps are not designed for pressure so can easily pop off

 

[fisherman]

The fabric Crewsaver bags are much tougher than the plastic Holt ones.

Yes, and the Crewsaver one I just got on ebay has a pinhole. (Stayed up three hours, was stated). Soon as I strap it, or sink it, it loses pressure.
Messaged the seller, but £6.50 the bag and £3.10 postage, what's the point?

 

[fisherman]

Sa

Saw that. I was just noting that an area filled with 1.5 rather than 2 will give more as getting more in due to the smaller gap between bottles and that water bottle caps are not designed for pressure so can easily pop off

I glued them all. A mix of sizes would be most effective.

 

[coopec]

Deleted