Self Healing Hull

[Ike]

This is very interesting.

http://www.sail-world.com/USA/Self-H...Research/50903
Self Healing Yacht Hulls: One Student's Research
'If only we’d had one of those self-healing hulls!' .
'We were sailing at night when we hit the whale. We were thrown from our bunks by the collision, which shocked us all, and knocked a large split in the side of the yacht. However, with our self healing hull, only a small amount of water entered before the hole covered again, and the automatic pumps were able to deal with it easily...'

Sounds like stuff from a science fiction movie? In the future, it just may be possible, thanks to a female doctoral student in Lausanne, France.

[clmanges]

Wow, amazing. And I'm a life-long sci-fi fan.

[BillyDoc]

Very interesting approach to the problem. I'm discouraged, however, when I remember that builders worldwide have consistently refused to use resins that resist osmosis (like epoxy) to save a minuscule amount of money up front, with the result that a major expense is transfered to their unsuspecting customers. These same builders would never spend the money for this hull technology, and it is way too sophisticated for the small workshop or "one off" production.

BillyDoc

[daiquiri]

I agree with BillyDoc. I have like an impression that, in this cynic world we live in, it would cost less (and therefore would be preferred) to build a new boat and hire a new crew to replace the, ehm... lost one, than to install and maintain a complex system like that one.

[Stumble]

I also have some concerns about the process of self repair. It seems that the way the hull heals itself is by having tiny bubbles of material present in the hull. So that when the hull breaks these bubles pop and out comes the sealent.

I am just curious how the bubles effect the resistance of the material to breakage in the first place. If they reduce the final strength of the hull enough they may just encourage breaks that they can then heal.

[Squidly-Diddly]

I started to build a boat using that stuff long ago.

they claimed that the sandwich would be semi-self healing and if punctured the semi-ridged foam would tend to spring back and semi-seal the hole.

These were sheets about 7/16" thick.

[Ike]

Well I am pretty sure that in building Alinghi, expense was not a big issue. But as was said I doubt if this technology will trickle down to the production boat or even the average custom boat. However it's good that someone has actually taken a different approach, and it works! Maybe someday it will be available to use regular folk. But I am glad it generated some discussion.

[ancient kayaker]

[[/b]

Originally Posted by Stumble

I also have some concerns about the process of self repair. It seems that the way the hull heals itself is by having tiny bubbles of material present in the hull. So that when the hull breaks these bubles pop and out comes the sealent.

I am just curious how the bubles effect the resistance of the material to breakage in the first place. If they reduce the final strength of the hull enough they may just encourage breaks that they can then heal.

According to the article there's a trade between impact on initial strength if the bubbles are large and plentiful vs insufficient healant to fill the gap if the bubbles are small and sparse. Shape memory alloy wire are used to close the gap in response to an electrical signal, to minimise the amount of healant required.

Neat, but I see snags with this: 1) they aren't yet able to direct the signal to the appropriate wire and 2) it seems to be limited to repairing delamination, where the gap to be closed is small and not very stressed.

If I understand correctly, it may restore the structural integrity of delaminated material but it cannot close and reseal an actual, serious leak. That being the case it's not going to stop a boat from sinking if it has a mind to, although it could help a damaged boat to stay together.

I'm not sure your average Joe Boater wants or needs all that. Unless you're engaged in a desperate fight with nature in the middle of an ocean race, what you really want to do when your boat has a nasty thwack on the bilges is creep cautiously to the nearest repair facility and get it checked out and fixed.

So, now for some good news. My idea for the average boater is, forget the bubbles of exotica and the fancy alloy wires, and use the optical fibers mentioned in the article that are to be used to detect the location of damage. These can be incorporated in one or more of the glass or carbon cloth layers. Now have an electronic box pass light through the fibers and detect any change, and raise an alarm. It doesn't have to located the injury, just alert you to the fact there might be one. A survey can find and quantify it. The optical fibers might be incorporated for relatively low-cost during the cloth weaving process. Finding and connecting them up might be more of a challenge but it is soluble. Do that for less than, say, 5% of the value of the boat and there'll be a market.

Of course, if you drill a hole anywhere in your hull the alarm will go off. If the fiber pattern has redundancy so broken paths just reduce not eliminate the light signal, then the alarm threshold of the box can be recalibrated after a repair or alteration. It would have to something that could not be done by some crook dealer to cover up an improperly repaired area, so the ability to rest the alarm needs to be restricted to responsible persons.

[Landlubber]

"so the ability to rest the alarm needs to be restricted to responsible persons."



we are talking about the boatbuilding industry aren't we????????

[ancient kayaker]

I was trying to look into the future and anticipate the influence of human involvement and greed. Like what we all wish MicroSoft would do before releasing faulty operating systems with wide open back doors for hackers to exploit. Your point is esentially my point, who can be trusted? Looking for similar issues, there's winding back auto mileage counters and changing VIN plates on stolen vehicles.

If this idea or something equivalent becomes adopted, we will need to make this as difficult as possible to limit the impact of human greeed which has the potential to undo all the good that could result from this kind of technology. If you can't trust the alarm then it is rendered valueless.

At this point it's probably more important to identify the technical and financial challenges.

Can optical fibers be incorporated into a composite, without impacting strength and durability, and still remain operational? I don't know enough qbout composite manufacturing to answer this question. The fibers would have to be continuous and extend beyond the edges for later connection. Is this best done during the weaving step or in the layup operation? What kind of sheath is needed to prevent light leakage into the resin matrix and at the same time ensure good adhesion? How many fibers per inch, how many layers of fibers ...

Can the fibers be identified after hull completion and be hooked up economically into a detector system? Builders would have to avoid cutting the fibers when trimming edges. Optical fiber connection is a well established technology but not as easy of convenient as electrical connections; it might be necessary to have many small electronic boxes to group the signals together at strategic locations for transmission to a central box.

What about deterioration with age of fibers, resin, optical connectors?

What's an acceptable false alarm rate? (Nothing's perfect).

And of course the biggest question of all, is it worth the trouble?