Boarding Seas

[ebb]

Somebody should have pointed out that:
total vessel displacement is to the load waterline.
Emergency bouyancy is the minimum extra to keep the vessel from sinking.

Am I correct in thinking, that once completely swamped the boat reverts back to its actual total material weight? IE, using the classic illustration, pushing a basketball into the water requires more effort the deeper one pushes. But if the ball broke, it would take little effort (weight) to immerse.

Once totally flooded, awash, only actual total weight of vessel plus occupants needs to be kept afloat for rescue.
To float boat above the sheer much more flotation is required.
Therefor the reserve flotation airbags (noodles) idea put forth here should be attached below the sheerline and calculated to provide enough bouyancy so that the swamped vessel could pumped out and 'refloated' at sea. That's what I had in mind.

Poof!

As to the original problem. These days, after decades of forced air-holding boats and fabric, there shouldbe something, some air bag, that is tough enough to be expanded into a void with sharp protrusions such as the lazarette (viz ob motor) to act as space filling reserve bouyancy.

[mbd]

Now I get ya Ebb.

How about airbags strategically placed in these "emergency" voids, which could be deployed when needed, then repacked when all is well... Kind of like an air bag in a car.

I understand that styrofoam has better floatation than the equivalent volume of air - makes me wonder if it wouldn't be better to permanently attach enough of the stuff in the nooks and crannies to make the boat positively buoyant - if that's possible.

Although, the styrofoam option would take up a constant amount of volume, whereas the airbags in their deflated state would take up much less valuable volume...

[ebb]

Mike,
Personally don't see how enough foam could be squirelled away in an A/C cruiser to make significant difference. But there's no reason emergency bouyancy bags couldn't be secured inside the boat, placed in a way the inflation of the bags wouldn't hurt or smother an occupant below, and leaving some room to manuever. Maybe the bags could be inflated in a totally swamped situation to void enough water to get the vessel to float on its own again.

[There you'ld be, soaking wet and cold, still alive after the worst night of your life. The bouy bags are keeping the boat afloat at the sheerline, but waves are still washing aboard over the stern into the cockpit. Looking into the companioway there is only water below upto the bridgedeck. You reach in, push a switch and in a series of hisses and whooshes the water below erupts out of the companionway. Instead of water there are tan pillows in the space. Suddenly the boat is floating a foot higher and the raildogs are flopping now but keeping the waves out. You find a snickerdoodle bar in the emergency bag and the sun breaks thru the clouds.]

Check out the site below. Just found it. One comentator described this as 'emerging technology.' The outfit targets small boats and puts the self-inflating airbags down on the spray rail in speed boats. But it certainly is the right idea, my comment being that if the vessels they depict overturn the placement of the bags might float the boat but probably upside down.

Keeping a displacement ocean going sailboat in trouble afloat will require a lot of serious and clever development of a system - but it's an idea that's already here! Nothing new under the sun. I'ld have more faith in the outcome if, instead of this company being in Colorado, they were located in Coronado.

www.goboatingmag.com/main/article.asp?id=3555

[CapnK]

Just some related thoughts -

When I rebuild #370's interior, I'm planning on making all compartments below berth-level able to be sealed off independently of each other. Hopefully, if something pokes through the hull, I'd be able to seal the area long enough to limp into a port for repair. Several ounces of prevention (say about 10oz/sq yd) may well be a lotta pounds of repair, though.

I'm thinking to lay in a sheet of kevlar-reinforced glass (should be spelled with a $$, I think ) against the hull interior from the bow as far aft as I can afford it, from maybe 12" above waterline down. I have a friend who builds surfboards, so I can get the stuff at his cost, which will help.

This is not to make the hull bulletproof, just as a way to help dissipate the shock of striking something outwards fast (which is what kevlar does in the BP vests), to minimize the breadth of any actual punctures. Will it make a huge difference? I don't know. It's a simple thing to do, won't add much weight, will actually lighten wallet. I've seen some of what lurks out on the ocean, on and just below the surface. Scariest thing ever was a 60+' tree trunk with only the stoutest of roots left, poking out from one end. Nothing higher than 2' out of the water, 98% of it was just under. I was on a Hobie, daytime, sighted it perhaps 50 yards away, and was able to swerve in time. Hit that puppy going 5 kts in a seaway and it would not be fun. Pray that you don't find a lost shipping container of Nike shoes or lumber out there at night... Paranoid? Yes, any time in water depth is over deck height.

As far as sealing lockers off, in its simplest form, maybe having pre-drilled holes around the edge of the lockers, and keep fasteners and tool to apply them handy. Some sort of commercial latch may work for this also, I haven't looked yet to see what is available. I'm planning on raising the level of the settee berths to above waterline, perhaps on level with the v-berth surface. I think it unlikely that the aft quarters could be hit strong enough to puncture, but may close off an area under the cockpit floor for a little reserve buoyancy in that area anyway. Forward most compartments would store those things only needed very rarely and/or at anchor, enabling them to remain closed for passages.

[ebb]

Great ideas!
Why Kevlar? Has problems with wet out I hear.
If you will be tabbing your furniture in you'll be adding plenty reinforcement to the hull.

You may have seen Jim (twice around) Baldwin on the Triton page or his own page on this subject. He has given a lot of thought to staying afloat.

[oops, gotta go!]

[CapnK]

Hi ebb -

Kevlar because from what I understand about how it works in BP vests is to take the force of a striking projectile and rapidly transfer that shock outwards along the length of its fibers, instead of allowing the shock to penetrate in.

I'm thinking that if it works with bullets and human chests, it should work to spread the shock load / point load of an impact on a saiboat hull as well, onto other areas of the hull. I'm no engineer, but it seems that if you could unload the impact forces out over a wide area fast, there would be less damage at the point of contact.

Yes, Jim B's pages are awesome. Both his and Glissando's refits served as inspiration for me to start looking for an older boat, and will serve the same duty in the future as I refit one myself.

[ebb]

KEVLAR!!!
Ok, but you know how my brain works:
First of all if you hit that qnarly tree (I've actually SEEN that tree!) it's "unlikely" you'll get holed. The hull will crack, if bad will get stove in, but hold together.

If that is correct, then applying rubber and fabric is a better way. With the kevlar, the mechanical bond might not hold. Of course I don't believe this, but it is possible that the kevlar is so strong that it could be pushed off as a unit, as a skin, and let the water in. While a rubber skin would be more likely to expand and keep the hole covered.

Wonder if such a product exists off the shelf. I did search for awhile for rubber tank coatings (to create builtin watertanks) without success, but was looking for potable stuff.

What you think about the rubber alternative? (like hypolon) - probably exists out there already. Rubber tanks in the market for years now.