Stupid idea No.2

[ninky]

when i was a kid i had a great idea of putting armbands on my legs and jumping in the deep end. luckily some kind adult spotted me and came to the rescue before i drowned. i hadn't quite worked out the need for buoyancy in some parts and the benefits of being able to be below the waterline in others. don't make the same mistake with your boat!

 

[Tranona]

I always find these debates fascinating for two reasons.

Firstly where is the evidence that outside extreme sailing (Tony Bullimore etc.) yachts sink and lives are lost? It is such a rare occurence that it can be ignored for all practical purposes. I know of course that not all incidents are recorded because there is non-one to tell the tale - but even unexplained losses are very small. So why the obsession with making a yacht unsinkable?

Secondly if it was a real threat and there was a practical solution somebody would make an unsinkable boat. As it is there is only one builder and one who used to build such boats. Neither have made any real impact, and owners often say unsinkability was not the prime reason for choosing the boat. Both use the same method of twin hulls and foam in between. Nobody has attempted to fill an existing boat with foam for the simple reason that the volume required is so great that you would end up with no room for people!

Anybody interested in the causes of deaths and injuries from yachting and how to minimise the risks of it happening to you should read the MAIB reports. As far as deaths are concerned there are only 3 causes - collisions with big ships, structural failure (usually on racing yachts) and being overwhelmed by extreme weather (usually in this case, the boat usually stays afloat even if the occupants are lost). Avoid those situations and you should be OK.

 

[pappaecho]

Just a thought. Will the cost of the foam be more than the value of the boat?

 

[drew silverwitch]

DO NOT USED CHEAP POLYSTYRENE
I had a Pilot18 in which it had been used for buoyancy under the deck. we had a very small leak past a keel bolt and over the season the boat got incredibly heavy as the foam slowly absorbed the water.
Having cut it all out, the local boat builder explained, you should always use closed cell foam.
We took note of this and found some 2 part stuff you can inject into the space and it will expand. We spent the next two weeks digging the foam out and re-glassing the deck back in. Well it did not look like much when we put it in but it don't half expand a long way, and you would not believe how much pressure it builds up until something gives.
I read the instruction with a lot more care now

 

[Bajansailor]

Just my two cents worth.
If you have an enclosed void space below deck, it is probably easier (and less weight!) to leave it empty, rather than trying to fill it up with foam - even closed cell foam has weight (and cost!).
Or, if you are determined to fill the space with buoyancy, I would use the plastic PET drinks bottles (the ones that contain fizzy drinks are stronger than those that you buy water in).
OK, there would still be a certain amount of permeability of the compartment if it does get breached, but it should be less hassle than foam in the long term.

A bit of fred drift re foam - some years ago we tried filling up a knackered old Avon Redcrest with 2 part expanding foam. It was not a success. Just made it much heavier, and there were so many void spaces that were not filled - which meant cutting holes to inject foam locally, and then patching the holes......

 

[bilbobaggins]

Firstly where is the evidence that outside extreme sailing (Tony Bullimore etc.) yachts sink and lives are lost?

I'm tempted to retort along the lines of "What planet...?" but will restrain myself.

Instead, may I suggest you have a riffle through the pages of The MAIB's 'Safety Digest'? Do have a look at Case 7, page 22 - and then a long think. There are others in there, more than sufficient to refute your bald statement.

It seems clear to me and many others that so-called 'human factors' are a major contributory cause of loss of life at sea - 'complacency', 'arrogance', and 'irresponsibility' being three of those.





Oh, what the hell....

 

[Bajansailor]

I must admit that I am a fan of water tight subdivision where possible - many catamarans have water tight bulkheads up forward (and aft in way of the engine rooms), and all commercial vessels carrying passengers are required to have a certain standard of sub-division (you can have one or two compartment standards, referring to the number of compartments breached while still staying afloat).
Most fishing boats have some water tight sub-division, even if it is only a collision bulkhead up forward.

 

[trying]

Not so stupid. As long as its closed cell foam so as not to absorb water. The 2 pack stuff as mentioned in one of the other threads.

I know some manufacturers use this in sealed compartments.

Can't stress enough though, as previously mentioned, understand and use the correct amount! Too much for the volume to be filled and it will keep expanding until something gives!

I witnessed the results on a new boat being built!

 

[NUTMEG]

Thanks chaps

This forum and your collective wisDom are invaluable! Sophie has been used as a day sailor for a season and apart from checking for leaks the forecabin lockers and the void beneath the cockpit are simply not needed. Seem sensible to me (although hopefully unnesesary) to fill them with something useful rather than remain empty. As for cost, exterior builders foam slab seem cheapest but I like the idea of 1ltr containers. Will take Vics advice and have a good measure up when Sophie comes ashore and see if the idea is feasible. By the way the mud patten are under
construction! Thanks again chaps.

 

[Tranona]

I'm tempted to retort along the lines of "What planet...?" but will restrain myself.

Instead, may I suggest you have a riffle through the pages of The MAIB's 'Safety Digest'? Do have a look at Case 7, page 22 - and then a long think. There are others in there, more than sufficient to refute your bald statement.

It seems clear to me and many others that so-called 'human factors' are a major contributory cause of loss of life at sea - 'complacency', 'arrogance', and 'irresponsibility' being three of those.



One case out of how many over the last 20 odd years that there have been proper investigations? In this case it did not result in a sinking and the vessel made it to port safely under its own power. Note the recommendations did not include advice to make boats unsinkable - just not to fit unsuitable seacocks. This is very well known fact.

Please show me some other cases!

Of course everything is possible, but it depends on what you are looking for. If you are looking for sinkings due to holing of the hull you will find them - but along the way you will not "see" all the other incidents which cause deaths and injuries that are NOT due to sinking from holing- and there are many more of those!

Improving safety is about learning from the root causes and taking action to avoid the most common situations. You will never remove the random incidents - the point is they are not systemic, whereas the records show that there are common causes which I have identified.

Much of the concern about safety is due to "imagination" - imagine what would happen if - rather than what actually happens. Improvements in safety come from evidence based thinking, which is what MAIB is about - rather than imagination.

And BTW I did not say it was impossible, only that it is rare. The problem with all such incidents is that they are so rare that they do not conform to any statistical pattern so can only be assessed on the basis of the individual facts.

I think you will agree that as just about all seagoing boats have seacocks - many 3 or 4 - the failure of one on one boat is not an indicator that all the other tens of thousands will fail. Rather that they are a pretty fool proof bit of kit if you use the correct material!

As to your suggested contributory causes, might I suggest that you actually read the conclusions and recommendations of the reports, which are much more specific than your sweeping statements! Then it will become clear (I hope) that complacency, arrogance and irresponsibility are never mentioned - the MAIB is not prone to using judgemental terms, only to establishing the facts.

 

[grumpy_o_g]

I seem to recall the RAF survival instructor's advice that "One should step up into one's liferaft....

Could I point out that this was probably sound advice, but was given to Aircrew on the basis that it was potentially a long step down from your aircraft Sir?

 

[William_H]

Boats sinking

Of recent years in our club"s racing we have had 2 sinkings. Both of f/g boats both due to being driven too hard laid over and the cabin filled with water via the main hatch and or forward hatch. One an M27 very light racer had forward hatch open for spin stowage and pretty much filled with water when laid over. Trapped air meant it didn't sink completely and was towed to a bank where it settled.
The other was a Farr 727 sport which was laid over with a just a large jib and too many people. The boat settle with about 1 metre of the stern and rudder out of the water. The air became trapped in the under cockpit area. Both boats were recovered with little damage but major loss of equipment.

Now it seems to me that apart from laying the boat over in hard racing a boat may sink from hitting a sharp object or from failure of fittings drains inlets etc or failure of rudder fixings. I did tear the stern out (well big holes in the transom at least)of a small cat once when the fixed transom mounted rudder hit a rock.

I think the best approach is water tight compartments and bulkheads. Most small yachts have bunks down each side with under bunk stowage. If you are willing to forgo the stowage or have good seals and locks on the compartments then a large amount of flotation can be achieved. Likewise under the floor boards (in the bilges) is a good place to put bouyancy. The lower the bouyancy the sooner it starts to work to hold the boat up so not allowing water to pour in because the boat is sitting low in the water. And of course the better chance you have of removing the innternal water.

I understand my type of boat when built new, now has a bulkhead sealing off the stern aft of the quarter berths. That would certainly provide a lot of bouyancy although not necessarily low down. It would if combined with a bow bouyancy tank keep it afloat. The bulkheads also isolate the area in case of a hole in that area. ie failure of rudder pintles structure.
So lower bouyancy keeps the boat higher makes it more usable to you and the crew and does not allow more inflow of water as a low boat will. Try to retain any water in the boat to the centre line as any water flowing to the sides of the hull will detract from natural righting ability. Another case for sealing under bunk areas.

I would suggest just seal off what you can and stop worrying olewill