Dumping keel and mast to make boat "unsinkable"

[SeaSpark]

As a sailor i have been dreaming about my world cruiser design for a long time.

The dream so far:

50ft strip-wood epoxy, free standing rotating wing masted monohull.

The rig is to give good performance when used as a cat, but when crew is available and we want to go fast headsails can be added. It will have a lifting keel and rudder. This to be able to go everywhere and to reduce wetted surface when in light weather go fast mode.

While thinking about safety i came up with the following idea:

A wood epoxy hull with foam sandwich interior and deck is very light and will float when holed (or even split in two) by for example a collision. If it were not for weight of the keel. My design has a lifting keel so it is easy to dump. To keep some sort of stability the mast will also have to go. It has no stays so is easy to dump also. Then the idea came to dump the mast using the weight of the keel, see illustration. The weight of engine, water and fuel tanks have to provide stabilily in this condition.

The idea may be a bit drastic but it is better then beeing on a liferaft.

Any comments welcome.

[gggGuest]

A multihull that was designed to be able to be sailed inverted might be easier to engineer. Lot of work on on designing storage for fluids etc, but If you're going to go to such extremes to deal with such a rare event...

Perhaps a sort of double cockpit arrangement where if the craft inverts you can release hatches to what would normally be a seales compartment on the underside of the hull, and then detach a cover to make a minimal cockpit with just enough facilities to get you home. A traction kite system might be eaiser than a jury rig on the underside.

[SeaSpark]

I mean a cat rig (large mainsail no headsail) on a monohull, not a catamaran.

As for complexity of engineering, the fluids are always stored as near as possible to center and bottom of boat anyway. The design already has a retractable keel and free standing mast so the engineering could be quite easy compared to making a watertight hatch and mini cabin in the hull.

I will most certainly carry a kite as jury rig!

[SailDesign]

That would be like designing a car's wheels to fall off in snow so you don't slide. How are you going to get home again?
Why not add some watertight bulkheads (and remember to keep the hatches shut!) and design the boat to be self-righting from any angle. Neither is hard to achieve, and you could still jury-rig something to get home even if the mast is gone. No keel = no sailing.
Steve

[SeaSpark]

On a 50ft yacht enough bulkheads to survive a severe collision are impractical as is the need to keep them shut all the time. They weigh a lot and have big impact on interior layout.

Getting home on a liferaft is also no easy task, a kite on the keel (not rudder)less yacht will enable you to reach the closest downwind land.

Sounds to me like Steve was dead on: if you design for such a rare possibility mighten the collision just as easily knock out the function of the keel/mast ejection mechanism? That system seems pretty nifty as long as they both go at the same time and the falling mast doesn't hurt the boat or crew any further.But I wonder if you really gain anything when you lose so much....

[SeaSpark]

Among going over the rail and fire, collision is one of the greatest dangers at sea. It still is a rare possibility but i want to sleep comfortably during a solo crossing.

The keel box will have to be very heavy anyway and so will the tube for the rotating mast. The dumping system is in between these closely bonded contructions, the safest place on the boat.

When the crew is under deck level they will be safe when someone (or the only crew member) pulls the locking pin. For pulling the pin i suggest a manual winch like used on boat trailers.

When you make sure everyone is clipped on on deck and have a good fire spreading prevention system the three major reasons for disaster at sea are delt with.

The gain is in not beeing on a liferaft.

Like I said...?

[SeaSpark]

Very unlikely on an unstable boat like this.

Among the forces working on a standing mast many are pulling sideways.
The deck area around a free standing mast is very heavy in construction.

[SailDesign]

SeaSpark,
You ask for opinions, and then reject any that don't fit your version of reality.
Enough bulkheads to survive a severe collision are not as bad as might seem. The bulkheads do not have to be collision-proof, just watertight, and this technology has been around for years, and worked well. Keeping the hatches shut is just a good habit - like wearing the seatbelts in your car rather than expecting them to miraculously work when not buckled up.
If you are that worried about sailing around the world, maybe you should shelve the idea.
Steve

[SeaSpark]

I really appreciate your comments, but as i am the one that put this idea on the forum i consider it my task to defend it.

To prevent sinking watertight bulkheads are the best solution, i agree, but even on military submarines they are only closed in case of an accident. I like the bulkheads used on some ofshore racers. They are made of the material used for inflatables with zippers for doors like in a drysuit. Very collision-proof. They still are quite expecive, have their impact on interior and are not very nice to look at.

Loads of money are spend on safety equipment on yachts, i still think my solution will add little weight or cost to a design.

[Guillermo]

SeaSpark,
I like your idea. It remembers me what lizards do: Throwing away their tails when in danger...
Maybe an easily frightened captain will put his finances in high risk if he loses keel, mast and sails everytime he begins to sweat cold, but...
Seriously, I like your 'lateral thinking' approach. Keep tight on it.
Maybe a drawback is the needing of keeping workable a system that probably will never be used in real life.

[MikeJohns]

Originally Posted by SeaSpark

On a 50ft yacht enough bulkheads to survive a severe collision are impractical as is the need to keep them shut all the time. They weigh a lot and have big impact on interior layout.

Often it is sufficient to compartmentalize the vessel with cofferdam type barriers after analyzing the trimmed floatplane for the damaged waterlevel.
For example a raised pilothouse/salooon over the engineroom can have such barriers fore and aft of the engine room access is simply down stairs from the saloon fwd and aft, along with a full fwd bulkhead Your 50 footer may be able to be holed in any section. In any case you will need some retained bouyancy to float the remaining weight of machinery, stores and sundry items so I would think you will need sealed ends either way.

From an engineering point of view you are adding complexity the bane of all systems. Novel idea though.

[SailDesign]

SeaSpark,
Defend away, no problem
Do you not think, though, that the keel trunk and the mast tube will have just as severe an impact on the interior as a watertight bulkhead or two? There will be a centreline obstruction just where you would usually put the saloon. We built a boat recently (56' Dutch design) with a lifting keel, and there really was no saloon. Add to that the mechanism, and you have a seriously split boat.
Do you have any means to prevent the mast from hitting the boat on the way down? How does the system work if the boat is inverted following the collision? How do you operate it if the compartment that is hit is the one with the mechanism in it?
These are just a few questions that cameup in the, oh, two minutes since I started writing this.
:thoughtful:
Steve

Sea Spark, I'm curious: Assuming you'll be sailing when catastrophe strikes-how would you de-rig the mast(get rid of sails, forestay etc) quickly enough in such circumstances to allow your system to be able to work fast enough to save the boat?