Unsinkable boats realy?

The above examples all appear to be manually inflated. Maybe they should be like the quick inflation rafts, as riding around with them inflated is not much more benefit than using fixed foam. No time to go from bag to bag to inflate in an emergency, when you need them most. Replacing a deployed car bag which should be cheaper with mass production is still very expensive- though a car air bag is more complex than a boat bag. If it's the middle of a storm, air rescue may be delayed considerably. The bill for CG or navy rescue may not continue to be gratis in the future, especially for frivolous excursions. Flat water stability might not hold with wind/waves or structure damage- worse to have an inversion or stance without protection.

FWIW.

PC

 

The Etap sail boats made in Belgium designed by Van de Stadt and Jack Ridder are unsinkable. Etap has been making unsinkable boats since the end of 70's or very beginning of the 80's. The biggest is 30 feet if I remember.
Excellent reputation, good, fast, rigid and comfortable as the flotation foam serves also for insulation. Very appreciable in cold seas. Highly regarded even used and 30 years old.
We tried a 26 feet in 1983, we made trials with the boat full of water in a state 5 sea with no problem, slow but totally functional and safe. Excellent design and engineering. In Europe the Etap are dispensed of security raft.

 

senior moment...... I forgot about ETAP. I went to see them at the Annapolis show when they were first introduced to the US. Very nice boats and yes they do advertise them as unsinkable.

 

There have been a few large cruisers that were billed as unsinkable, Wellington is one name that comes to mind. There have been others

Steve.

 

The Etat are better than advertised, they are really unsinkable. But better than than, they remain functional even full of water. A lot of people saved their lives with unsinkable boats in some coastal waters like Britanny, Anglo Normand Islands, Scotland, Norway where rafts are useless as you are washed immediately to the shore and beaten to death on the rocks. And someone said it's easier to find a boat than a small raft or worst a guy in the water. The "unsinkability" thing is perfectly feasible on boats until 30 feet, it's a question of brain juice and the old Van de Stadt had a lot...he solved very elegantly the problem.

For bigger boats it becomes more difficult because for a question of stability and survival (keeping enough free-board and stability) most of the volumes must be placed near the junction deck hull so that takes a lot of volume just in the habitable section.

 

The Macgregors also are really unsinkable and functional when full of water, at least the cat was and im fairly sure the same holds true for the others. The impressive part is they did it in an entry level boat.

Steve.

 

I guess my old 1960`s DIY ply boat (self Inflated) with many hundreds of litres of air under the floorboards in plastic containers would not qualify as legal flotation in many countries and it did not cost much or take much thought to construct.

 

A lot of sail dinghies are unsinkable as it's pretty easy to put the volumes under the seats and to keep enough freeboard and stability. It was a big fun to sail a 420 full of water...A lot of RIB's are also unsinkable with the soft "airbag" around the hull which serves of bumper at the same time. For monos it's simpler to put the airbag outside around the hull than inside...It has been made several times for working boats.
I knew about the cat by Mac Gregor. it's pretty easy on cats as you can put a lot of volumes under the floors without affecting the stability full of water. A lot of small cats can be filled of foam under the floors and thus making them impervious to bottom hull punctures. If you add the thickness and the low density of a sandwich hull combined by the big surfaces of a multi, it becomes even easier at least until 40-50 feet on light catas.
On trimarans it's a breeze with the high volume amas (together they make now more than 4 times the displacement...). Except total dislocation of the structure, nobody leaves a trimaran even capsized. You have water, provisions, radio etc, you must be insane for leaving the trimaran.

 

If the repartition is good no problem, but just volumes under the floor the boat will make the turtle...

 

If you do not have the flotation as low as possible you will get your feet wet,better to stay afloat than to worry about turning turtle. Damage above the waterline would be a problem if you sink that far.

 

ETAP ?

This article says they went bankrupt

"new ETAPs haven’t been produced or sold commercially in the U.S. since early 2009, when the Belgian yacht company that designed and built the classic ships declared bankruptcy,"

http://www.businessweek.com/articles/2012-02-23/etap-yachts-rebranded-as-armageddon-life-rafts

 

Tom, floatation location is actually pretty simple and below the sole is the worst place for it. If you have a significant enough of an issue, whereas the floatation location decisions come to play, getting you feet wet is a minor concern.

 

I am afraid I can not agree with you par, the flotation must be in the water that is intruding to support any weight otherwise you will sink untill enough support boyancy is flooded. Just like a raft in the bottom of my boat.
My concern was damaging the bottom from a rock or log not ocean going survival.
www.glen-l.com/webletter/webletters-7w155-floatation.html

 

This appears to be the link Tom intended: https://www.glen-l.com/weblettr/webletters-7/wl55-flotation.html

USCG floatation requirements: http://www.uscgboating.org/assets/pdf/downloads/FLOTATION.pdf

Ike's New Boatbuilders Website http://www.newboatbuilders.com/ has a page with good information about floatation: http://newboatbuilders.com/pages/flot.html It includes a link to set of Powerpoint slides with recommendations on what to use and where to put it: http://newboatbuilders.com/docs/flotation_2.ppt

Slides from Richard Akers' presentation on floatation at IBEX in 2004. http://www.shipmotion.com/pds/IBEXFlotation.pdf Ike's page on floatation also has the link.

 

Right DCockey thank`s .