Big lifeboat drop

[Guitar]

 

[amolitor]

The human body, properly restrained, can take at least 45Gs, properly restrained, facing forward.

Look up Dr. Stapp's tests: 46.2Gs max, 25Gs for 1.1 seconds. The equivalent, supposedly, of driving a car into a brick wall at 120mph.

I especially enjoyed Kittinger's description of this test run, toward the bottom of http://www.ejectionsite.com/stapp.htm

EDIT: In short, this little drop into water ain't nuthin.

 

[bistros]

It is not only the height that matters. You probably wouldnt experience anything more drastic than a free fall, or roughly one G. The fun is during the entry into the drink. I wonder what kind of a G force that corresponds to. If the air time is close to 2 seconds, you would be doing over 200 km per hour when you hit the water. If the damn thing comes to a stop at a fraction of a second you are in for a serious experience. If it lands in any way other than nose first, you are in serious trouble.

Nope. It takes 12 seconds to reach terminal velocity - about 120 miles per hour in a stable flared position. Even in a no-lift head down dive you would not be going more than 40 miles per hour after 2 seconds. Your first two seconds of falling will reach 62 feet, so from 90 feet you'd take under three seconds.

(I've done this about 400 times from aircraft, balloons and helicopters)

40 miles per hour at impact is serious - normal parachute landings are at 0-15 miles per hour depending on parachute type, direction relative to the wind etc. I've done 14-15 mile per hour landings on World War II style military chutes (T-10s, C-9s, Paracommanders) and they sure hurt compared to modern "square" rigs.

Highest I've jumped/dove into water was 50' in a rock quarry, and I sure would not want to get it wrong! I'd seriously expect a 90' drop would cause spinal compression damage especially in an uncontrolled attitude.

--

Bill

 

[ryley]

I believe it used to be mandatory for US shipping personnel to be required to do one emergency evac in a lifeboat from the simulated height of a typical cargo ship. The requirement was dropped, however, after studies showed sailors were more likely to burn alive than go through another drop.

My captain's course instructor related his story about the drop,facing forward, where essentially everyone hits everyone else's head on impact. Also, the vent in the hatch is notorious for not really sealing properly, so the last guy gets drenched, and chain puking is not uncommon.

They're designed to dive deep and come up far from the ship with the assumption that you'll be outside of whatever danger area you're abandoning. In some cases, it just isn't far enough.

 

[Rain Man]

The human body, properly restrained, can take at least 45Gs, properly restrained, facing forward.
Look up Dr. Stapp's tests: 46.2Gs max, 25Gs for 1.1 seconds. The equivalent, supposedly, of driving a car into a brick wall at 120mph.

I especially enjoyed Kittinger's description of this test run, toward the bottom of http://www.ejectionsite.com/stapp.htm

EDIT: In short, this little drop into water ain't nuthin.

Sure, survival is possible higher than 25 g's. But stuff starts to happen, broken blood vessels, impact of internal organs against rib cage, whiplash, etc. etc.

That article lost credibility when it confused the Second Law with the First:

"At the end of the run the brakes locked up, instantly producing 30 Gs. The belt neatly parted and Oscar, in meek obedience to Newton's Second Law of Motion, sallied forth."

Any high school physics student knows that's the First Law.

dash

 

[amolitor]

Stapp walked away from his 46.2G run without any substantial injury. He was BLIND for a little while, and he looked really interesting, and he had a pretty awesome harness restraining him, but it basically wasn't a big deal. This is documented widely, not just by people who are sloppy about Newton's Laws.

 

[VENOMISS]

I've watched both videos posted and noticed one thing they had in common. CALM WATER for testing. If it's hitting the fan, wouldn't it be a rather rough sea state? Could that cause probs/issues with impact if you hit a swell wrong or something? ...I don't know anything about these things, just an observation/curious thought.

 

[Rain Man]

Stapp walked away from his 46.2G run without any substantial injury. He was BLIND for a little while, and he looked really interesting, and he had a pretty awesome harness restraining him, but it basically wasn't a big deal. This is documented widely, not just by people who are sloppy about Newton's Laws.

Not to be picky but from Wiki we have:

"Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm.[10] The record for peak experimental horizontal g-force tolerance is held by acceleration pioneer John Stapp, in a series of rocket sled deceleration experiments in which he survived forces up to 46.2 times the force of gravity for less than a second. Stapp suffered life-long damage to his vision from this test.[11]."

I'd call that a substantial injury. I'd argue that most crewmembers of a ship or oil rig are untrained when it comes to handling high accelerations, whereas Stapp was highly trained and had serious restraints. These values are also horizontal accelerations. The average person will black out at only +5 g vertical after a few seconds. Voice of experience here. I'm trained now and can handle a bit over 5g for several seconds with no loss of vision or concentration.

dash

 

[svitale]

I've watched both videos posted and noticed one thing they had in common. CALM WATER for testing. If it's hitting the fan, wouldn't it be a rather rough sea state? Could that cause probs/issues with impact if you hit a swell wrong or something? ...I don't know anything about these things, just an observation/curious thought.

Calm water will have a greater surface tension so the surface is harder to break. With ocean waves, the wave moves through the water, but the water stays in place. Any wind blown water landing on the surface will decrease the surface tension.

Since a kayaker recently flung himself off a 186 foot or 56 meter and survived so the forces on the body are not too great. He did have the advantage of landing in aerated water which makes the landing softer.

When I was running waterfalls the trick was to find the correct angle to land at the bottom. Land too flat and you shrink a few inches. Too deep and you eat the paddle shaft and pop backward into the hydraulic for a few recycles. Nail it just right and the nose breaks the surface and the boat shoots forward then resurfaces just like the one above.

 

[VENOMISS]

I've watched both videos posted and noticed one thing they had in common. CALM WATER for testing. If it's hitting the fan, wouldn't it be a rather rough sea state? Could that cause probs/issues with impact if you hit a swell wrong or something? ...I don't know anything about these things, just an observation/curious thought.

Calm water will have a greater surface tension so the surface is harder to break. With ocean waves, the wave moves through the water, but the water stays in place. Any wind blown water landing on the surface will decrease the surface tension.

Since a kayaker recently flung himself off a 186 foot or 56 meter and survived so the forces on the body are not too great. He did have the advantage of landing in aerated water which makes the landing softer.

When I was running waterfalls the trick was to find the correct angle to land at the bottom. Land too flat and you shrink a few inches. Too deep and you eat the paddle shaft and pop backward into the hydraulic for a few recycles. Nail it just right and the nose breaks the surface and the boat shoots forward then resurfaces just like the one above.

Thanks for the insight there.

 

[sinner]

With that reeeeeally fast orange paint job...

Wots

it

rate?

 

[daffy]

looks like a moore 24 popin' out of a big nasty one!

 

[InNeedOfSomeRestraint]

It is not only the height that matters. You probably wouldnt experience anything more drastic than a free fall, or roughly one G. The fun is during the entry into the drink. I wonder what kind of a G force that corresponds to. If the air time is close to 2 seconds, you would be doing over 200 km per hour when you hit the water. If the damn thing comes to a stop at a fraction of a second you are in for a serious experience. If it lands in any way other than nose first, you are in serious trouble.

Simple physics. If you fall from 55m your impact velocity is 33m/s or 118 km/h or 74 mph. If the thing goes, say, 2m down into the water before stopping, that represents a deceleration of 269 m/s/s or 27g. It is a misconception that "g's" are a force - "g" is acceleration.

The human body can take about 25 g before it starts to "fall apart". So I'm guessing that these things are designed to go a lot further into the water before they pop up. If they stop over a distance of 3m the acceleration goes down to 18g.

The pictures don't show clearly how far it goes into the water. I'm guessing it is about 4 m which would make the impact quite survivable without broken bones, provided the occupants were restrained.

dash

We need to remember that all of this terrible vision loss, femur cracking, concussion inducing fun is all in place of drowning on an oil rig that's screwed the pooch.

 

[SeaWay]

We need to remember that all of this terrible vision loss, femur cracking, concussion inducing fun is all in place of drowning on an oil rig that's screwed the pooch.

Less likely to drown of a sinking oil rig than be burnt to a crisp first.

google "piper alpha".

Many people die in free fall life boats every year during maintenence and testing, some of the quick releases have a hair trigger, or are badly maintained.

if you are not properly strapped into the seat, injury is guaranteed.

cheers

SW

 

[InNeedOfSomeRestraint]

We need to remember that all of this terrible vision loss, femur cracking, concussion inducing fun is all in place of drowning on an oil rig that's screwed the pooch.

Less likely to drown of a sinking oil rig than be burnt to a crisp first.

google "piper alpha".

Many people die in free fall life boats every year during maintenence and testing, some of the quick releases have a hair trigger, or are badly maintained.

if you are not properly strapped into the seat, injury is guaranteed.

cheers

SW

What a boatload of fun that turned out to be.

 

[Pavook]

that lifeboat drop reminds me of some of my better craps. enormous force of entry, controlled surfacing, lots of cleanup.

 

[AlStorer]

It is not only the height that matters. You probably wouldnt experience anything more drastic than a free fall, or roughly one G. The fun is during the entry into the drink. I wonder what kind of a G force that corresponds to. If the air time is close to 2 seconds, you would be doing over 200 km per hour when you hit the water. If the damn thing comes to a stop at a fraction of a second you are in for a serious experience. If it lands in any way other than nose first, you are in serious trouble.

Simple physics. If you fall from 55m your impact velocity is 33m/s or 118 km/h or 74 mph. If the thing goes, say, 2m down into the water before stopping, that represents a deceleration of 269 m/s/s or 27g. It is a misconception that "g's" are a force - "g" is acceleration.

The human body can take about 25 g before it starts to "fall apart". So I'm guessing that these things are designed to go a lot further into the water before they pop up. If they stop over a distance of 3m the acceleration goes down to 18g.

The pictures don't show clearly how far it goes into the water. I'm guessing it is about 4 m which would make the impact quite survivable without broken bones, provided the occupants were restrained.

dash

As said, the boat goes under a lot further- also, the way it is designed it will be converting some of the downward motion into forward motion, transferring some of those g-forces to another plane. Essentially: It's a lot more complicated than that. Also, still better than burning to death on a exploding platform.

 

[kent_island_sailor]

The other day a ship called the USCG to announce they were launching their lifeboats to test them. I guess life in the anchorage was getting boring

 

[familysailor]

 

[sinner]

Here's another I found along with the one you posted. People inside.....yikes!Fire sprinklers on the outside too, although they look a bit anemic.

Thanks for sharing.