How common is it for boats to be unsinkable? ie. has built in floatation

[gregcope]

Don't know about the Open 40s, but from what I can see Pogo do not use double skinned hulls, but vacuum infused GRP/Foam composites - just like Bavaria and many other production builders. This leads to a hull around 10-20% lighter than a conventional hand laminated hull - probably even lighter in the case of Pogo because their aim is to produce a very light displacement boat, typically about 60% of a "conventional" cruiser of the same size.

The foam does not make it unsinkable. it is used to stiffen the laminate.

But Pogo's are unsinkable because they fill voids/areas with foam. Although different from the Sadler design in implementation, is the intent and result not the same? Unsinkable? Slight loss of storage space?

 

[gregcope]

Yes, the boat is far from sailable but is at least afloat. Some time ago I calculated the amount of additional buoyancy available, in fenders, half full tanks, even beer cans which have positive buoyancy, and the result was surprisingly high.

vyv with that much beer, do you find it hard getting crew ?

 

[Tranona]

But Pogo's are unsinkable because they fill voids/areas with foam. Although different from the Sadler design in implementation, is the intent and result not the same? Unsinkable? Slight loss of storage space?

I can't see any claims that they are unsinkable and just filling the lockers with foam would not provide enough buoyancy. As you see from Vyvs description of the Sadler it not only has foam in voids, but also 40mm thick in the hull. The Etap was the same.

Pogo don't make any claims on their website about added foam except on the details of the 50 which has foam in the stringers, under the bunks and other unspecified area to "aid insubmersibility". Otherwise they are made using a common construction method of vacuum infused GRP foam sandwich - just lighter than more conservative designs.

 

[gregcope]

I can't see any claims that they are unsinkable and just filling the lockers with foam would not provide enough buoyancy. As you see from Vyvs description of the Sadler it not only has foam in voids, but also 40mm thick in the hull. The Etap was the same.

Pogo don't make any claims on their website about added foam except on the details of the 50 which has foam in the stringers, under the bunks and other unspecified area to "aid insubmersibility". Otherwise they are made using a common construction method of vacuum infused GRP foam sandwich - just lighter than more conservative designs.

Agreed with infused sandwich construction.

They also inject foam into voids.

Check their specs, in french, look for “Réserves de flottabilité” which basically means reserve bouancy. Provided by foam. Cat A rated.

 

[Tranona]

Agreed with infused sandwich construction.

They also inject foam into voids.

Check their specs, in french, look for “Réserves de flottabilité” which basically means reserve bouancy. Provided by foam. Cat A rated.

Cat A does not require any form of reserve buoyancy. The key factor that would determine the category, particularly on the smaller boats would be the stability (AVS and STIX) and downflooding angle. The hull form lends itself to achieving good numbers on this for the boat's size because of the high form stability and buoyant coachroof. The designers will have had achieving this as a key objective.
It illustrates well how the requirements can be met with very different designs.

I can't see any detailed specs on their website and in the descriptions on each model I see no reference to foam except on the 50, nor any reference to the category , although I assume they are all Cat A given they are advertised for offshore use.

 

[Kelpie]

But as you illustrated in post#10 that amount of foam only gives you neutral buoyancy in lightship mode. Add on all that beer and the other stuff you cram in plus water, fuel etc adds up to well over another tonne to the basic 5.7 tonnes displacement. According the Kay (who Andrew quotes in his PBO article) you need 1.5 times the displacement in foam to achieve enough freeboard to make the boat habitable and capable of sailing.

That would really reduce the interior volume available for stowage.

Do you know for certain that the Salder 34 "Dorothy Hackforth" was sailing in light-ship mode?

 

[Daydream believer]

Also maybe someone could invent a quick release keel on sailboats so when you pull
the lever the keel falls off and sinks to the bottom while the boat floats on its side or upside down.

Yes on the mass production side of the market the likes of beneteau and bavaria have had some success on that and on the higher end of the market oyster did experiment with one of there more expensive designs. Bavaria could not get proper detachment, only a bit of a "wobble", .Beneteau managed complete inversion but oyster could not get the flotation bit quite right
on the "one off" side early designs such as Simon le bon's Drum did very well as did one ot two others.

i believe they all decided to cancel further research after limited success and lack of demand

 

[Tranona]

Do you know for certain that the Salder 34 "Dorothy Hackforth" was sailing in light-ship mode?

No - the opposite. its displacement would have been greater as it was fully equipped for cruising. Therefore (even accepting Vyv's point that some things like empty cans and fenders would themselves be buoyant) it would float even lower.

The only reason I mentioned light ship is because that is the condition where the foam would have maximum impact in terms of how the boat floats, and the decks would be awash.

 

[vyv_cox]

Do you know for certain that the Salder 34 "Dorothy Hackforth" was sailing in light-ship mode?

I believe the Dorothy Hackforth was a sailing school training yacht. The name is that of the lady mayoress of Weymouth(?) who provided the purchase cash.

 

[Tranona]

I believe the Dorothy Hackforth was a sailing school training yacht. The name is that of the lady mayoress of Weymouth(?) who provided the purchase cash.

Small correction She was mayor of Poole and the money was raised during her year's office - don't know how much she contributed herself. It was indeed used for sail training

 

[Seajet]

Sued or used ? there's a significant difference !

Our clubs' Sailability Norfolk Oyster ( which I've skippered now and again ) was launched by the lady Mayor of Portsmouth - these people will go anywhere for a glass of warm white wine and a curled up sandwhich !

In fact I think she put quite a lot into what is an astonishingly expensive boat given what she is.

 

[gregcope]

Cat A does not require any form of reserve buoyancy. The key factor that would determine the category, particularly on the smaller boats would be the stability (AVS and STIX) and downflooding angle. The hull form lends itself to achieving good numbers on this for the boat's size because of the high form stability and buoyant coachroof. The designers will have had achieving this as a key objective.
It illustrates well how the requirements can be met with very different designs.

I can't see any detailed specs on their website and in the descriptions on each model I see no reference to foam except on the 50, nor any reference to the category , although I assume they are all Cat A given they are advertised for offshore use.

Try googling:

site:www.pogostructures.com flottabilité

This will show pages on that site that reference adding bouncy and float-ability, or in this thread unsinkability.

Does that help?

 

[vyv_cox]

Small correction She was mayor of Poole and the money was raised during her year's office - don't know how much she contributed herself. It was indeed sued for sail training

She launched the boat.