Unsinkable... so was the Titanic... etaps et al....

I find the concept that full cruising kit lowers the boat's water line by four inches to take some believing. Certainly that isn't the case wih us, I would guess something like one inch would be nearer the mark.

However, just musing about the likely effects of adding lots of kit, here's an attempt to find the overall effect on submersing.

Heavy items - anchor, chain, spare anchors, bikes, tinned food and beer, tools. With the exception of the cans, for me this comes to 380 lb. A brief experiment shows that cans have neutral buoyancy, so I'm discounting them. For the sake of the argument, I'm happy to double the figure, making it 760 lbs.

Buoyant items. 12 Fenders. These displace something like 220 lbs. Manual washing machine 40 lb. 20 gallons diesel, 18 lb. various plastic containers, 40 lb? Total 320 lbs. Add to that various spaces in the boat that would be buoyant, e.g. part filled water tanks, tops of lockers, and I think it's fair to add at least another 30 lbs and maybe as much as 100 lbs? Total something like 350 - 420 lbs.

So all we are actually trying to support, in addition to the boat which we know is buoyant, is around 400 lbs. Since, in the case of Etaps and the smaller Sadlers, the boat will still sail when all seacocks are open, that doesn't seem excessive to me.
 
Take a look at 'free surface effect'.... this may cause a heavily flooded boat to capsize...

i've no comment on the unsinkability bit though..... we don't know enough detail to determine either way.... but i'm inclined to support Vyv's post above....
 
A heavily flooded boat will have a lower centre of gravity so lessening the effects of free surface movement
“The higher up these fluid motions occur, especially above either the craft's center of moment (buoyancy) or center of mass, the more pronounced the instabilities.”
However my comments were made about multihulls, or “floating tea trolleys” as the original poster referred to them, which I feel would suffer even less from free surface movement.
As for unsinkable I would bet my house on it!
 
[ QUOTE ]
Heavy items - anchor, chain, spare anchors, bikes, tinned food and beer, tools. With the exception of the cans, for me this comes to 380 lb.

[/ QUOTE ]

You cant have much in the way of chain and anchor?
I have just over 300lb in chain alone and a couple of 40lb anchors?

do you mean kg by any chance?

Rob
 
I have 60 metres of 8 mm chain. Call it 200 ft at just over a pound per foot, according to West Marine. Two 35 lb anchors. I also have lots of Anchorplait and a Fortress with about 7 metres of 8 mm chain, but this is included in the doubling up. Although rope sinks I doubt if its density is all that much more than 1, so it's probably almost neutral for these purposes.
 
Thanks Vyv. To meet the criteria set by the French Marine Marchande for 'unsinkable' for a yacht, I understand its not just a case of being able to float when flooded. I don't know all the details, I have been looking but my French is not so good, but I do recall being told that the boat has to float a certain % of freeboard/length, be able to sail and recover from something like a 90deg knockdown.

It would be helpful if Etap were to add a link to the relevant web site that has the specification. It would silence a lot of the sceptics, well some anyway.
 
The amount by which a boat sinks as a result of additional weight is governed by its waterline plane area. The larger this is the less it will sink. I think it is expressed as kg displacement per cm. In other words how many extra kgs displacement required to increase the draft (lower the freeboard) by 1cm. Luddites can have lbs per inch if they want. So a modern wide beam shallow bodied boat will sink less than an older narrow beam boat of the same WL. Many modern boats also have a lot of flare in the topsides which increases stability as the boat heels. Therefore the waterplane area increases as weight is added. Andrew Simpson did a whole article on this subject a few years ago in PBO when he was explaining why his latest live aboard boat is a modern wide beam shallow hull light/medium displacement design.

On the subject of unsinkability, I guess that the reason it has never caught on is because the incidence of yachts foundering at sea as a result of holing in UK waters is almost non-existent. Three recorded cases in the last 12 years. Wahkuna, the Moody which had the front 3 metres wiped off in a collision with a container ship in 2003; Megawat a Hanse 371 which lost its rudder, breaking the tube away from the hull in the Celtic Sea in 2005 and Ile D Yeu which collided with a chemical tanker in the North Sea in 2006 - sinking after the crew had been rescued.

The downsides of Etaps and Sadlers have all been stated - cost, loss of living space, difficulty of repair, potential deterioration of foam etc. Obviously some people are OK with this but not enough to make them high volume sellers.
 
[ QUOTE ]
I guess that the reason it has never caught on is because the incidence of yachts foundering at sea as a result of holing in UK waters is almost non-existent. Three recorded cases in the last 12 years. Wahkuna, the Moody which had the front 3 metres wiped off in a collision with a container ship in 2003; Megawat a Hanse 371 which lost its rudder, breaking the tube away from the hull in the Celtic Sea in 2005 and Ile D Yeu which collided with a chemical tanker in the North Sea in 2006 - sinking after the crew had been rescued.


[/ QUOTE ]

I'm in total agreement with your point but I'm sure there have been a couple of others - there was a Sunsail boat a couple of years back, and the Ouzo must have sunk even if we don't quite know how. A guy at work's boat sank on it's mooring too.
 
Yes, but the Sunsail was a lifting keel 6.7m which was swamped (if it is the same one I am thinking of). I have excluded Ouzo and the Twister that disappeared off Holland in 2000 because no wreckage has been found of the former - and it is suggested that it was either swamped or suffered massive damage. The wreckage of the Twister showed extensive damage and it is believed to have sunk immediately. One might argue that in both cases an "unsinkable" hull might have survived the impact sufficiently to have remained afloat, but the MAIB reports did not speculate on this.
 
People dont buy an Etap just because of the unsinkabilty, although it has to be said it does have a certain attraction. We bought our second Etap (we are on our third) attracted by the solid engineering, the quality of build, light and airy interior, helped by the now popular on many boats, panoramic window. none or little condensation, cooler in summer, warmer in winter. Add to this an abundance of decent hand holds and from the 32S upwards, proper sea berths, and full length hand holds.

What stops Etap from being a volume seller is the fact that is NOT an AWB, just compare a 37S with boats the same length. You wont find double aft cabins on Etaps, that's not just because of the foam, but because of a balanced hull shape, max beam, well forward. (having said that the new 28S does have a fat arse)

Your point about the degrading of the foam, have you ever seen a case of this? The foam has been around for about 35 years now and I have never heard of it degrading.
 
agree, build is very good. Ours is 1981, and nothing wrong with the foam, never heard about that urban myth.....

The unsinkable bit, goes on the list of course and to some degree reasures all the family. Of course if you want to get a raft as well. Its a bit like all those countless insurances we go for ( water, boiler, house, buglars, washing machine, and so on ) /forums/images/graemlins/smile.gif,
but hopefully never ever use.
 
I think the foam degrading thing was from the Sadlers....

You can tell if there is a problem apparently if when you walk on the deck there is sort of a crunching noise underfoot...

certainly when I looked at a34 a couple of years ago it was a bit crunchy..


Ive never heard of that problem with the Etaps.


I am sure that a Sadler expert will elucidate.
 
I agree absolutely with you. There are good reasons for buying an Etap that are nothing to do with its unsinkability. So why do they persist in promoting it when it has so little value?

I was admiring a Starlight 35 out on the hard at the Club yesterday and thought how brilliant a boat it is, and how much more successful it might have been if it had been built simply and conventionally - and probably 20% cheaper!
 
Starlight 35.....mmmmmm.....

Now that is my all time desireable boat....

they have never claimed that the Starlight is unsinkable, but the double hull also adds alot of strength and stifness.... so if they got rid of the inner hull I doubt it would be the same boat!

But they are fabulous arn't they!

/forums/images/graemlins/smile.gif
 
Know they did not claim it was unsinkable, but it was "twin hulled" rather than foam cored - and not without quality problems in manufacture IIRC. If all the main design parameters are the same then the hull construction should be irrelevant. Guess if we really wanted to know we should ask Stephen Jones - all his recent designs seem to be "conventional" construction!
 
The foam degradation problem with Sadlers is yet another example of the 'what if' being converted into 'it did' with no evidence. Once industrial polyurethane foam has cured there is nothing that will degrade it except mechanical damage. I have heard a tale, but never seen any evidence, that wave pounding at the flat areas immediately astern of the bows on a Sadler 34 caused the foam to powder. I suspect that in fact these tales derive from lightweight round-the-world racers that did have a similar problem.

I have known several boats that had a 'creak' on deck, my 34 is one. Having owned it for 12 years now, I am certain that this is not a serious problem. It has not become more widespread in my ownership. If I was really bothered by it the problem can be fixed very easily.

My purchase of a 34 was not influenced at all by any claims of unsinkability. The foam filling does reduce stowage a little but there is plenty of kit on board for two of us to live aboard for half of the year. Its advantages are that the boat is very well insulated, quiet, has a full internal moulding that not only provides high quality locker space but also makes the whole structure of the boat extremely stiff.

Nowadays it's difficult to imagine how these boats were built at a cost that was competitive with conventional ones. The standard of the grp work is very high, although the wiring on the early boats leaves a lot to be dsired. This was corrected after about 1988.
 
re weight of kit for full time liveaboard..

Just totting some figures up...

200 lbs of anchors,
600 lbs of 10 mm chain
250 lbs of 8 mm chain.
450 lbs of batteries.
95 lbs of windlass
130 lbs of outboard (Tohatsu 18)
150 lbs of watermaker kit
100 lbs of hydrovane
70 lbs of chubb !!!
100 lbs of liferaft.
100 lbs of nylon coiled rope (possibly nearer 200 !)

so theres around 1 ton before we got to the other things lol..

My electric winches add another 70 lbs over standard, eberspacher another 30 or so.

Then, engine spares (starter, alternator, injectors etc etc)

Tools !!.. Jeeez, a LOT lol.. inc the welder and power tools..
Electronics gear - must have around 100 lbs of gear, plus my workshop at a hundred pounds weight.. plus ssb's in stock

then, the folding bikes, trolly, generator, towed genny, wind genny...

thats before we get to other 'normal' items lol..

I ADDED over 100 lbs of high current wiring on the last refit (over and above the original marginal setup..)

the lists goes on and on...
 
You need a cellar on your boat then..or a garage /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

Tim
 
You must log in or register to reply here.

Other threads that may be of interest

mogmog2
Maxwell windlass 10 VW looks interesting (to a windlass noob)
2 3
Replies
56
Views
1K
Neeves
N
Mr Googler
A rebuild thread to keep you all happy for the long winter
5 6 7
Replies
133
Views
5K
Mr Googler
Mr Googler
Y
The Seafarer 700 and NASA clipper sounders saga
Replies
10
Views
367
Dellquay13
Dellquay13

Share this page

Top