Dumping keel and mast to make boat "unsinkable" [Archive]

SeaSpark

04-01-2006, 04:34 AM

gggGuest

04-01-2006, 05:34 AM

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

04-01-2006, 07:26 AM

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

04-01-2006, 09:41 AM

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

04-01-2006, 11:18 AM

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.

Doug Lord

04-01-2006, 12:31 PM

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

04-01-2006, 12:51 PM

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.

Doug Lord

04-01-2006, 01:00 PM

Like I said...?

SeaSpark

04-01-2006, 01:05 PM

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

04-01-2006, 04:01 PM

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

04-01-2006, 11:35 PM

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

04-02-2006, 01:36 AM

SeaSpark,
I like your idea. It remembers me what lizards do: Throwing away their tails when in danger...:p
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

04-02-2006, 07:23 AM

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

04-02-2006, 09:23 AM

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

Doug Lord

04-02-2006, 09:40 AM

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?

SeaSpark

04-02-2006, 11:55 AM

The lifting keel does give a split interior in the centre part of the boat, this is bothering me highly but i don't want to give up the lifting keel.

Cruising possibilities about double in Holland for a shallow draft craft and it enables you to reach the last few quiet places here. I want to make long voyages, but it also has to be a good boat for weekend passages in Holland.

Making even more small compartments is what i am trying to avoid.

The boat will be very difficult to invert becouse of the buoyancy of the wing mast. The mast damaging the deck is the least of my worries when my boat is in the condition a want to pull the plug.

The system does not need to be very complicated. Most elements are already there in the form of the locking mechanism for the lifting keel and the bottom of the wingmast that also has to be removeable for service.

The connection between keel and mast could be a heavy nylon strap over a simple roller under the deck at foot of mast. The strap will fit in the gap between mast and masttube and will have to be fitted to rotating ring at mast foot. I am now concidering a quick release with a pre-attached rope to lead to a winch in the cockpit. The cockpit is a save place on a sinking ship with a mast comming down.

Getting rid of the rig will involve cutting the nylon strap, the mainsheet can have a quick release. Investigating the possibility of a sharp blade under the roller that cuts the strap automaticly when mast is at maximum height. The yacht will have a temporarily forestay only in use when headsails are used which will not be often in cruising mode.

I would like to have another person on board to gather supplies and preparing the liferaft the same time.

Thanks to everybody for their input.

RHough

04-02-2006, 12:17 PM

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.

Engineering?

50ft LOA = 45ft LWL? for a RM30 of around 130,000 lbs?

Displacement 40-60,000 lbs? Ballast 33-40% of displacement?

That gives 13,000 - 24,000 lbs of ballast.

Assuming only the torque from the RM and the heeling moment of the sail is acting to hold the mast in the boat, how is 13,000 lbs going to overcome the friction caused by 130,000 ft lbs of torque? Will the mast move?

If you add a forestay so you can hoist headsails, you will need running backstays or enough leach tension to tension the forestay. This puts a compression load in the mast that would act directly against and in addition to the friction from torque. The mast probably would not move.

Novel idea, but it won't work unless you have a frictionless bearing surface to mount the keel and mast to the boat. The bearing surfaces must also have zero clearance unless you are planning to let the keel and mast rattle around in the boat. It will be very difficult to find a zero clearance, zero friction mounting system that is dimensionally stable within the temperature ranges that a world cruiser must endure. If it is not exactly right, the keel and mast will bind at some temperature and the system won't work. In other conditions the keel and mast will move inside their supporting structure and create point loads and shock loads, possibly making them self eject.

SeaSpark

04-02-2006, 08:46 PM

RHough

04-02-2006, 09:27 PM

In my opinion the concept of rotating free standing masts has already been proven.

Well designed self aligning bearings at bottom and deck level in combination with a bearing that takes vertical loads at bottom wil help solve the problem. Use of modern materials will help making things not to heavy. Most of the additional weight will be near bottom of boat.

Defending this opinion is beyond the scope op this thread.

I'm sorry if bringing up the mechanical realities of making the system work is not on topic. You don't want to discuss the idea further? Without considering the physics and engineering required to make a system work, we may as well be talking about turning lead into gold. Does this idea fall into that category?

You asked for feedback. I gave the idea enough thought to try to engineer a system that would work. Now making it work is off topic?

No question that low friction systems exist that will allow the mast to rotate while under load. What is needed is a low friction system to allow the keel to drop and the mast to eject while under load. Standard bearing systems won't do the job.

To get the mast to come up out of the deck it has to slide under load, sticking the mast in a tube is not going to work. As the mast makes its way out of the boat the per unit area loading of the support structure increases. At some point it will bind or break the surrounding structure.

The keel faces some of the same problems to a lesser degree. Hoisting the keel in near calm conditions is a far cry from what is needed to let it drop out of the boat while ejecting the mast in an emergency.

There would be a better chance of getting the mast out of the boat if it was pulled rather than pushed. A helium balloon stored inside the top of the mast and tethered could inflate and pull the mast out of the boat, clear of the deck and hoist an emergency radio antenna at the same time.

Respectfully,

Randy Hough

Ari

04-02-2006, 11:48 PM

Why do you need to dump the keel ? why do you need to dump the mast ? I had known a guy who had circumnavigate single handed and got overturn at cape of good hope, the Australian built mono named "Jalur Gemilang" righted it self up, main mast broken, set a jury and sail to Falkland. If he had dump the keel and the whole mast, will he be able to sail to Falkland and safety ? or should he wait for rescue ? will be in better scenario if he dump the self righting facility from his boat..for sure he will be stranded and not able to complete his journey. If he is on his own budget..maybe he can salvage the mast and continue with the journey.Since this journey are fully sponsored and the sponsor budget had taken this scenario into account, the support team fly him the new mast and sail..with a C130 Hercules and he have about two weeks vacation in Falkland before continuing his journey.:cool:

solrac

04-03-2006, 04:02 PM

ooopssss. may be simpler solution: attach some explosives to the keel bolts....(and be aware of the location of the red button)
by the way, someone knows if C4 is waterproof?:)
well, seriously now,
why not thinking on a kind of "airbags" similar to the used on cars?
lets see:
1. don't know your boat size & displacement, so, let's supose: a sailboat 30' (on the 4 to 5tons displacement) it will preety do about 1200kg hull + 1500kg ballast, so, in case of a serious emergency, you will need a "flotation" device to compensate that sinking weight (about 3ton, let's take 4ton to be sure)
well, 4ton water @ 1.025 density will make a 4100 kg need for water displace on interior space, that's about 4m3 air on some kind of baloons yeap?
2. each car airbag is at least 200lts capacity, so will be impractical to connect 20 airbags on line, maybe a kind of rubber bag (or bags) that can be inflated to that size (low pressure only, you don't want the cabin's roof been blown out...)
3. The gas tubes (i.e, CO2/Nitrogen/Hellium/Argon or whatever it can be found there) come in standard size & capacity of 45kg on a 200bar pressure, it makes about 13m3 gas @ 1 bar (atmospheric pressure) enough to inflate whatever it's been needed.
4. the car Airbag system is preety crowded of sophisticated electronics, not suitable for a ship I think, but, surely your boat has a 12v supply, in that case, a simple hi-pressure solenoid valve conected to gas supply tube & bags, a couple piping & a red panic button conected to activate the solenoid and that is all...
5. think you will need some professional advice, to determine the rigid points inside the cabin where to attach the bags also.

airbags:
http://www.airbagsystems.com/main.htm

Solenoids:
http://www.ascovalve.com/smartcat/sc_app/sc_filter.asp?famID=2&code=0,0,0,0

DanishBagger

04-05-2006, 06:16 AM

I don't get it, even though the lightweight boat (hull+deck) could in theory float by itself, I wonder if it would still float with all your paraphernelia in the boat (warps, anchors, water, fuel, ekstra sails etc). If you dump the keel, you will have a huge hole in the bottom of the boat.

I would definately go for the watertight bulkheads, or at least go for watertight areas. Or perhaps even go for superfast inflatable "lungs". That way it might stay afloat.

At least that's what I think.

Edit: Come to think of it, let's say that you are indeed able to eject the mast, first of all, how would you get it to fall in the right direction and not damage the boat or kill you? Secondly, what if it's ejected, lifts, say a meter/3ft out of the mast hole and then all that weight coming down on the deck again?

DanishBagger

04-05-2006, 06:17 AM

C4 is indeed waterproof, solrac. the problem is what if water short-circuits the detonators?

SeaSpark

04-05-2006, 06:32 AM

The keel box for the lifting keel will provide a "well" so water can't enter the boat.

I have been looking in to airbag like systems, the material of the bag will have to be very strong so it will not get punctured when it meets something sharp when beeing blown up.

As an alternative i have been thinking about a thin bag that fills with a 2 component foam. You need quite a large amount of foam for this and i wonder if it will cure fast enough. You would be able to carve out the foam to reach supplies needed for survival.

DanishBagger

04-05-2006, 06:45 AM

How about the mast when it is ejected and comes back down?

The foam - what will happen if, say it is mixed with seawater (say the bag erupts while it's expanding, or if it cannot expand in one direction because it has "plugged" itself? Will it make the hull, for instance, crack?

I don't know, I have never liked technological/mechanical solutions when an ordinary non-moving part could be used. How about making some flotation rooms instead, along the boat, that way, if the boat is holed, either only the flotation rooms would be filled with water, or if the hole is outside the flotation rooms, then it would still float. No moving parts to screw up.

I like to adhere to the principles of KISS, simply because less is prone to go wrong.

SeaSpark

04-05-2006, 07:33 AM

When my boat is in the condition i want to sacrifice the keel and mast just to stay afloat damaging the deck will be the least of my worries.

I totally agree with the KISS principle.

My main reason to want a 50ft boat is higher speed potential and more comfortable motion at sea, interior volume is less important to me.

The first solution i came up with to make my boat hard to sink with was bonding large volumes of foam in construction elements like scantlings, ribs and interior, sacrificing some room. The Etap yachts are a good example of this.

It has been proven many times that bulkheads not always succeed in keeping a boat afloat. Many bulkheads on a relatively small boat are impractical.

solrac

04-05-2006, 09:54 AM

It has been proven many times that bulkheads not always succeed in keeping a boat afloat.

That's the reason larger passenger boats do have a different approach: they use life rafts instead... (oops, remember Titanic...)

I agree with your security concerns (my job does involve people's security on petroleum piping facilities), but, my feeling is you are dreaming on a technical imposibility, need some kind of device, activated just in case, to minimize damages, & save the hull, (even if it has been broken).
I would suggest first, your concern must be to save the passengers, for the rest, the insurance company is the one who must concern about...

if you're thinking on a 50' boat, (let's say a displacement of about 7/8ton on an approx. weight of 10ton), think there is no practical way to save the hull in case a disaster, other different thing is saving the passengers on a life raft, there are a lot of models available out there.

In my country, the regulations state that you must carry an auto-ejectable life raft (one or more) of the adequate size for all passengers on your boat, for anything bigger than 4ton displacement....

Sailing4Fun

04-05-2006, 02:49 PM

I have read the thread ... I think I understand the concern.... but I am not sure I follow the thought process on your solution to this seemingly highly unlikely event.

I understand that you want a lifting keel ... that makes sense ... especially if you are cruising in shallow water.

But the rig ... the rig ejection system ... is what leaves me scratching my head. Especially since there is a huge possibility that once you've dumped your rig ... that you will be in more trouble then you were when you had it.

If I understand your thought process ... and I might not ... you are concerned that in the event of a collision your boat will sink. To stop this from happening you are going to eject the keel and the rig, and merely leave yourself floating helplessly in a battered hull.

For the record ... Rig Ejection system will now be referred to as RES

Questions:

In the event of RES Failure (partial or total): the rig and keel are ejected at a less the opportune time ... you’re left with nothing ... and nothing to build a jury rig with.... PROBLEM ... and a likely one ... since as you are circumnavigating the world it will be difficult for you to check the wear on the components holding this system together

OR

The rig fails to eject properly (are you really going to want to test this system before HAVING TO USE IT? (Masts and keels are expensive and a pain to get back once you have dropped them on the bottom of the ocean)): you have a hole in your boat ... and despite all the effort you have gone to to save your boat in the event of this type of incident you still end up in a raft (which you will be required to carry).

THESE ARE ONLY TWO SCENARIOS

Possible Solution to your anxiety:

Take the advice of the people on the form (way more educated then me ... but I am trying to get there slowly) and build a boat that is self-righting and has the proper amount of subdivision. If you feel really uneasy about this add some secondary floatation ... foam under the cockpit sole.

Even if you don’t want to have the doors closed all the time, my guess is it would be as quick to close all the doors, as it would be to get the RES into action.

Probably my biggest concern ... the fact that I think your forgetting that most retractable keel setups are built to keep the keel in the boat, especially in the event of failure. I am actually totally mind boggled as to how you think your going to get around that issue.

I am sorry if I have come across as a bit of an jerk ... it was not my intention ... but I have spent most of my young life around boats ... I am studying to be a naval architect and while I think protecting life at see is incredibly important, I don’t think your solution is appropriate.

Cheers

Sailing4Fun

solrac

04-05-2006, 08:28 PM

I was thinking in another issue: in the event you can blow out keel & mast, there is a big posibility for the weight distribution you might have that the hull ends upside down... (woow, you must not worry about the keel bolt's holes...)
to how are you going to survive on a hull floating on the ocean upside down?
how are you going to get in & out the cabin? maybe a scuba drive will help? a couple diving tanks & a snorkel?
(sorry for the joke, couldn't stop it)
the only thing that will save your life on a critical moment is the keel, who helps righting the hull.... the issue is not there, just be creative adding enough flotation

yokebutt

04-06-2006, 12:49 PM

Sparker,

If you really are worried about sinking, then increase the thickness if the foam sandwich in hull and deck, that wilol work.

Yoke.

Wellydeckhand

04-07-2006, 05:44 AM

solrac

04-07-2006, 09:34 AM

mmmm... have anyone seen the National Geographics videos of "re-floating" some sinked ships? they use some kind of inflatable really big "bags"
Don't think it would be so difficult to find.
alas, the inflatable poles used for regatta signalization?
the kind of zodiac inflatable boats material?
even a couple rubber truck tires can do the job, lets check:
a standard truck tire camera 760/14 full inflated @ 1 bar holds about 1.10 / 1.20m3, at 5 bar it holds about 2.5m3 (do not try this, apart from risk of exploding, the external pressure force of about 5kg/cm2 may harm a lot of your cabin) you wouldn't need more than 4.... (just tell me, haven't you ever played at beach or river when you were a kid with one of this?) :D :D :D

DanishBagger

04-07-2006, 09:46 AM

What about mylar? That is what they use for wine-bags amongst other things as far as I know.

solrac

04-07-2006, 01:48 PM

What about mylar? That is what they use for wine-bags amongst other things as far as I know.

filling it with wine? not bad....:D :D :D :D thought it has a 0.88 density respect water, can be a lot of fun, but don't think it will help as floating device... :D :D :D :D :D :D

yokebutt

04-07-2006, 05:13 PM

Once upon a time, there was a Danish engineer who raised a sunken ship by blowing in styrofoam beads. Unfortunately, he was denied a patent because he got the idea from an old Donald Duck comic magazine.

Yoke.

DanishBagger

04-07-2006, 05:14 PM

filling it with wine? not bad....:D :D :D :D thought it has a 0.88 density respect water, can be a lot of fun, but don't think it will help as floating device... :D :D :D :D :D :D

Hehe, I thought I'd put it there, because if it can hold an acidic fluid, it must be pretty tough :P

SamSam

04-08-2006, 10:29 PM

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.
Any comments welcome.
SeaSpark,
The following is a quote...

"On boats, it has been well proven that the very distribution of weights athwartships and into the rig are in fact favorable to stability in a 'dynamic' environment. We have observed that boats that have been dismasted are much more likely to be rolled over. This is due to the lack of inertia (lesser roll moment of inertia) and the relative ease with which a heavy roll can be suddenly induced. This cannot be demonstrated by static analysis as one would normally expect, since the dismasted boat obviously has 'more' static stability without a mast - in the actual ocean though, it is the opposite."

from this page about a third of the way down under 'ROLL MOMENT'
http://www.kastenmarine.com/beam_vs_ballast.htm
The site was posted by someone in another thread. The guy seems to know a few things and according to this it would seem you might be accomplishing the exact opposite of what you want as far as safety. Sam

SeaSpark

01-17-2008, 04:25 PM

The guy seems to know a few things and according to this it would seem you might be accomplishing the exact opposite of what you want as far as safety.

This guy should also know it is more safe to stay on your boat for as long as possible before stepping in your liferaft.

Omeron

01-18-2008, 04:45 AM

SeaSpark, i love novel ideas as yours, it lubricates the brain cells and practices mind. But since you are taking all this trouble to save yourself
in a rather unlikely occurance, i would think that you would test it a few times to make sure it works.
I am just curious, how many times would you eject your mast and drop your keel, to make sure it works ok!
Ofcourse doing this on a sunny summer day, on flat water is one thing, and trying it in the dark of the night, with breaking seas, and water rushing in is another.

TeddyDiver

01-18-2008, 06:22 AM

Didn't read the whole thread throw, and so don't know if this has been mentioned before.
Had a thought about your idea, and In think distributing the ballast partly, from 50/50 to 70/30, btw hull (or long keel) and lifting keel would give you the chance to keep your mast.

SeaSpark

01-21-2008, 07:55 PM

think distributing the ballast partly, from 50/50 to 70/30, btw hull (or long keel) and lifting keel would give you the chance to keep your mast.

Very good idea, with a weighted centerboard/long keel configuration like this it should be possible:

http://www.dickkoopmans.nl/images/zwaardjacht.jpg

My initial plan was to have a boat that could go faster than the speed determined by its waterline length with added headsails in fully crewed conditions. This is not possible with the hull shape shown above.

I can have impractical ideas.