Sinking Cats

[fastcat435]

I am very sure the Outremer will sink if the buoyancy chamber are not taken into account .
If a Catamaran is build with closed cell foam that adds a lot to the buoyancy of that Cat.
It also helps in keeping the weight lower and that again helps in buoyancy so the knife cuts on both sides.
If on top of that you are able to keep the weight of your boat low that helps again.
This means that the cats with the lowest weight in a certain length combined with built in buoyancy have the highest safety factor.

Gideon

[Spammy]

Fastcat, I agree that closed cell foam appears to be the best overall choice as a core material. Balsa is good for several reasons, but the durability in the event of water intrusion is a deal-breaker for me when it comes to balsa.

Rocky

[fastcat435]

Originally Posted by Spammy

Fastcat, I agree that closed cell foam appears to be the best overall choice as a core material. Balsa is good for several reasons, but the durability in the event of water intrusion is a deal-breaker for me when it comes to balsa.

Rocky

That is the reason for us not to use Balsa. Foam lasts and lasts even with water intrusion.
We also use cored laminate under the waterline so Balsa is completely out.

Gideon

[Eleven]

Much repetition here again but just on the Titanic. The film was a re-write of history, no doors were locked, etc etc. The build is fully recorder, the design engineer wanted full height bulkheads designed to hold a flooded compartment separate from the rest of the ship. On cost grounds he was over-ruled and many partitions were not to the full height. An economic decision but 'fairly' sound. The shipp would still survive a single compartment being severely holed and flooding, it was the long rip flooding at least three adjacent compartments that caused the lower bulkheads to overspill into dry compartments. The list didn't help either. She was designed to be unsinkable and it was such good press that it was not ammended at the same time as the design was changed.
Elsewhere there is much on surviving an upturned cat. Basics pre-sailing things like anchor points under the bridge deck to secure your liferaft once flipped, cupboards that stay shut while the swell inside the upturned hulls washes everything out thro the doorway to the sea. The other prep is to mark on the outside of the hulls the right place to cut through, and clamp a saw somewhere to effect an entry. A lot can then be done, after the storm, to recover the cockpits, bedding etc to make survival a lot more comfortable and well fed than a life raft. Pre-planning for the occasion.

[cat man do]

For Spammy

The first 3 are pics of an uncored (solid glass) cat.

It was a deliberate sinking I believe (insurance) and I dont think it entirely sank.

Others from Oz may know more.

Others are of capsized multi's showing what a great and habitable liferaft they can be

Dave

[Factor]

Dave - the first three pics are of (I Think) "Eroica", a fastback 43 that was allegedly deliberately scuttled and later recovered and is now sailing again. Without going into it the crew that had been on the boat left it due to the skippers increasingly irrational behaviour.

[freetime]

From another thread on this forum.

[BigCat]

You can have a solid bottom and core the rest of the boat. That's what I'm doing in my build, and I believe some stock cats are built this way as well. If you don't trust buoyancy tanks, you can fill them with 2 pound density pour in polyurethane foam. This can be gotten in fire retardant formulations, at an extra cost. I am putting this floatation foam inside my crossbeams and in the bridgedeck structure. You can also do the math to make sure the boat will float, as I mentioned previously. Floatation foam will give you a net buoyancy of 62 pounds per cubic foot. Balsa can't be the source of much trouble if it is fully laminated. It is voids in the lamination that can give you problems. It is difficult to get any core to stick fully to the very rounded parts if the hull is made in a mold. (See: Professional BoatBuilder - August/September 2005 for proof.)

[cat man do]

Originally Posted by BigCat

It is difficult to get any core to stick fully to the very rounded parts if the hull is made in a mold.

Yep, seen this and had to repair firsthand.
Some of the repairs were in flat sections, it still had voids.
Boat was in Survey as well

Good enough reason NOT to have a moulded boat IMHO

Dave

[BigCat]

Originally Posted by cat man do

Yep, seen this and had to repair firsthand.
Some of the repairs were in flat sections, it still had voids.
Boat was in Survey as well

Good enough reason NOT to have a moulded boat IMHO

Dave

As far as laid up in a mold, it's probably OK if it's solid below the water, because that's where the curvy bits are. Any core below the waterline would have to have so much goop to bond properly that you might as well have gone with solid, in terms of weight.