Making a Hunter Europa Unsinkable

Little Rascal

Little Rascal

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A theoretical question - at the moment.

How easy would it be to make my Hunter Europa (19ft) unsinkable?

I've been reading Roger Taylor (Mingming - Corribee 21 to Greenland) and he seems to place great store by unsinkability, especially in view of containers, ice etc and as he's a singlehander, being unable to keep a continuous look out.

He did it by virtually filling the boat with foam. I was wondering if dinghy style airbags would work - enabling them to be let down when space is needed.

The boat displaces just under 700kg so I reckon I'd need at least 700 litres of airbags, for example 6 x 125l bags from a Flying Fifteen.

How much reserve buoyancy would I need?
I'm guessing it would be best to fasten them low down in the hull too?

The Europa is a pretty seaworthy boat (for her size) and I'm not taking her to the Arctic (!) so at the moment it's just a theoretical exercise - but would it work?
 
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There's a big difference between unsinkable and survivable. You could theoretically use airbags to make your boat unsinkable, but it would be totally unstable, may well invert, and wouldn't be likely to provide you with adequate shelter to survive. As for how many airbags, you'd need enough volume not only to cover the boat's displacement, but also the added weight of crew, equipment, stores, etc. And you'd need to consider whether just floating (ie awash) is sufficient. It's a non-starter.
 
I did the same calculations when I got my Seahawk17. Someone had already started filling the voids with expanded polystyrene waste. I worked out I was going to need about 150 5 litre plastic containers (I have a source). Just where I was going to put them and what benefit I would really obtain I wasn't sure.

So I didn't. I also chucked the E.P. away as well.
 
pvb said:
It's a non-starter.
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It is. At the moment for me anyway.

But I am interested.

The point about survivability is a good one. You wouldn't last much longer in a flooded cabin than in open water at high latitudes.

I suppose what you would trying to protect yourself against is some kind of massive flooding via hull damage or the wrong kind of wave up the chuff.

Theoretically you'd then have time to repair or at least slow the leak and limp on home.

I guess you would need to provide enough buoyancy to get the hatch above water to be able to pump out. Hence securing the bags low down (quarter berths, bow bags etc)

The stability issue is a good point too. You could end up capsized first, then flooded...

However at 19 feet a liferaft isn't quite so easy to carry... :rolleyes:
 
Rather than trying to install permanent foam buoyancy, it might be better to try and create various separate water tight compartments, on the assumption that only one (hopefully) would be holed in the event of an accident.

For instance, if there is a vee double berth forward, the aft transverse bulkhead of this berth could be a collision bulkhead of sorts, and if the access panels into the compartments underneath can be made reasonably water tight (eg with rubber gaskets and securing latches) then you effectively have a buoyancy compartment(s).

Here is an excellent article by James Baldwin about how he effectively made his wee sailboat Atom pretty much unsinkable, using the concept of water tight compartments :
http://www.atomvoyages.com/projects/UnsinkableBoat.htm
 
Little Rascal said:
I guess you would need to provide enough buoyancy to get the hatch above water to be able to pump out. Hence securing the bags low down (quarter berths, bow bags etc)

The stability issue is a good point too. You could end up capsized first, then flooded...

However at 19 feet a liferaft isn't quite so easy to carry... :rolleyes:
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Wouldn't securing flotation bags low down potentially increase the risk of capsizing?

As for stowing a liferaft, if you think you've got space for 800+ litres of airbags, I'm sure you can find somewhere for a liferaft!
 
I'm not convinced that low-down buoyancy will lead to instability.
When supported by it's buoyancy, the boat will sink down into the water until this buoyancy is fully submerged and working- but it won't sink any lower than this, as no further buoyancy is coming into effect and if it did sink lower, it would just carry on sinking and founder completely.
So if you fix the buoyancy low down, you keep everything above it dry... the keel of course remains where it always was, low down, so I reckon stability would be fine.
I may be completely wrong, of course!
 
Robwhelton said:
I'm not convinced that low-down buoyancy will lead to instability.
When supported by it's buoyancy, the boat will sink down into the water until this buoyancy is fully submerged and working- but it won't sink any lower than this, as no further buoyancy is coming into effect and if it did sink lower, it would just carry on sinking and founder completely.
So if you fix the buoyancy low down, you keep everything above it dry... the keel of course remains where it always was, low down, so I reckon stability would be fine.
I may be completely wrong, of course!
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Your theory's fine if the sea is calm and the water comes in at a controlled rate. The OP was talking about something different - "I suppose what you would trying to protect yourself against is some kind of massive flooding via hull damage or the wrong kind of wave up the chuff." In that event, I reckon it'd be unstable.
 
elton said:
A search of all forums for threads with "unsinkable" in the title yields 15 results, some of which you may find quite interesting.
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Sorrreeee! :o

Bajansailor's article indicates that buoyancy should be high up not low. My original thinking on this was as Rob said, that if it's above the hatches it's useless. I think that flooded in a seaway you would need it higher for stability.

Re carrying a liferaft:
You can't deflate a canister! The point was the bags would only be inflated when needed (or when you're concerned!)

An 80 litre(kg) pillow type buoyancy bag measures 140cm by 46cm dia.
 
Little Rascal said:
Re carrying a liferaft:
You can't deflate a canister! The point was the bags would only be inflated when needed (or when you're concerned!)
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Ah, I understand now. So how exactly were you planning to predict "some kind of massive flooding via hull damage or the wrong kind of wave up the chuff" in time to be able to blow all your bags up?
 
pvb said:
Your theory's fine if the sea is calm and the water comes in at a controlled rate. The OP was talking about something different - "I suppose what you would trying to protect yourself against is some kind of massive flooding via hull damage or the wrong kind of wave up the chuff." In that event, I reckon it'd be unstable.
Click to expand...

More thought experiments (oh goody):
let's say that somehow the entire craft gets swamped and flooded. You have the top part of the cabin full of water, some/most of the lower cabin filled with buoyancy, and the keel below all of that. The waterlogged cabin space is about neutral buoyancy, but the keel is very dense- so once the boat has a chance to right itself, it will. It will then rise again until the buoyancy is at the surface- remember, if the buoyancy were to remain underwater, that would mean it was insufficient to support the boat and the whole lot would sink anyway. Once the upper part of the cabin is above the surface, it will drain.
Perhaps in a very rough sea there would be enough movement for the boat to roll and flood the upper cabin repeatedly- but it would always want to self-right and place the cabin-top above the surface.
If you can keep the cabin-top watertight, even to some degree, then it will not swamp every time the boat rolls. This might mean keeping washboards in place and fixing stormboards to the windows.

If, alternatively, the buoyancy is placed high up, then the whole boat sinks down until it is awash. Perhaps it will roll less in a rough sea but it is effectively uninhabitable. I don't see how this is in any way a better position to be in- and it's certainly completely unrecoverable.
 
Little Rascal,
If you haven't read 'Very Willing Griffin" by David Blagden, I bet you'd love it. He goes into a good bit of detail about preparing his Hunter 19 for the Ostar. I've lent out my copy, and I can't remember if he talked much about adding a lot of buoyancy, other than the fact that every food or water container played a role.
That's a fun boat you have there ;-)
 
Little Rascal said:
The boat displaces just under 700kg so I reckon I'd need at least 700 litres of airbags, for example 6 x 125l bags from a Flying Fifteen.
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Remember that even submersed GRP has buoyancy. The 19 (or maybe the Europa) displaces 681 kg, of which 340 kg is iron ballast. Iron has a specific gravity of around 8, so you need 7/8 x 340 = 300 kg to hold it up. The rest is mainly GRP, with some lighter wood offset by some heavier metal. GRP has a typical specific gravity of 2, so you only need 1/2 x 341 = 170 kg to hold that part up. Total 470 kg. Of course there are considerations of stability, payload and so on as well.
 
I made my kingfisher 20 unsinkable - even if I could get a few seconds to grab dinghy, VHF, water etc - (ref 117 days afloat - Baileys). Used a combination of methods including four inch closed cell foam which hacksaws into any shape, watertight lockers using ply over openings and simple round cheap hatches ( rubber o ring seals). the aft end was partially supported by eight 20 llitre fenders, found in a jumble which fitted in both cockpit lockers - secured of course. Managed to exceed displacement of boat which gave me lots of reserve buoyancy.
 
Inserting bags in your boat will serve no purpose other than preventing your insurance company from buying you a new boat. Their effectiveness is very doubtful in any but the smoothest sea state.

Obviously, the problem is more important in the smaller yachts. Years ago while in the AF, I spent some time bobbing in 2C water... not good!

My opinion is that flooding in a smallish boat in cold temps automatically becomes a case of SURVIVAL. You will be washed overboard within a few minutes.. almost certain.

I would rather have a good waterproof survival suit with a top notch life jacket (with hood please) than hope some haphazardly inserted air bags placed wherever possible & accessible might do for my future on this planet.:D

Think out of the box maybe??? Perhaps oil platform supply companies may help?? They have the best of equipment.

You do have a problem finding a boat borne solution. GL
 
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I agree. Filling up cockpit lockers so that they are no longer useable on the 1000:1 chance that you will sink in a flash seems a bit over-cautious.
If the worst case scenario should happen....


....well we all die sometime.
 
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