If flooding

[sorvju-f]

I started to think like preparing!

What should you do if for some reason you get videohousing full of water.
It means that UW I will get 10-12 kg negative buyoancy!

Is BCD enough to compensate the lost or...?

Comments, please!

Jukka

[Jonathan Bird]

What should you do if for some reason you get videohousing full of water.

I have never had it happen fortunately, but I would imagine that the first thing I would do is start swearing like a truck driver.

After that, I would go up.

I can't imagine that the housing would be too heavy to get to the surface though. Might take a lot of air in the BC though.

Jonathan

[Kelly]

Hi Jukka,

Lets hope that never happens to you. That seems like a lot of weight. I think my set up is about 2 or 3 lbs negative, and if it flooded I doubt I would feel the full surface impact of it's weight. Buoyancy is a matter of displacement of water, which would still displace water whether flooded or not. I'm not an expert though.

You'd need to know the lift capacity of your BC, and it's current working lift to know how much more you can take on. If you're really concerned about it, you could try it in a pool. Add 12kgs to your current weight system (make sure it is ditchable) and jump in.

I dive a backplate/wing (capacity is 40lbs/18kg) set up with double steel 100's and carry a 50lb lift bag for those times I might need a bit of extra lift (hasn't happened yet, but it's good to have). But so far the 40lb wing has been sufficient even when carrying another 40cuft stage. I do think I'm close to it's capacity though.

Just some food for thought....

[Ken Hawk]

What should you do if for some reason you get videohousing full of water.
It means that UW I will get 10-12 kg negative buyoancy!



Jukka

Drop it and claim on the insurance ;)

I don't think you would have any trouble at all getting it up, if you did you could always send it up on a DSMB.

Ken

[sorvju-f]

Drop it and claim on the insurance ;)

I don't think you would have any trouble at all getting it up, if you did you could always send it up on a DSMB.

Ken

Ken, haven't you had ever problems with insurance company:eek:

When i go to office of my insurance co, officers are running out and even planning to jump out of window:D

Sorry, but what is DSMB?

Jukka

[sorvju-f]

Hi Jukka,

Lets hope that never happens to you. That seems like a lot of weight. I think my set up is about 2 or 3 lbs negative, and if it flooded I doubt I would feel the full surface impact of it's weight. Buoyancy is a matter of displacement of water, which would still displace water whether flooded or not. I'm not an expert though.

You'd need to know the lift capacity of your BC, and it's current working lift to know how much more you can take on. If you're really concerned about it, you could try it in a pool. Add 12kgs to your current weight system (make sure it is ditchable) and jump in.

I dive a backplate/wing (capacity is 40lbs/18kg) set up with double steel 100's and carry a 50lb lift bag for those times I might need a bit of extra lift (hasn't happened yet, but it's good to have). But so far the 40lb wing has been sufficient even when carrying another 40cuft stage. I do think I'm close to it's capacity though.

Just some food for thought....

Kelly! Actually I know that my BCD is taking up about the same than yours. I took this question up because I have never thought it myself and wanted to videographers to use couple of seconds to think about it. Suprising things can lead to narrowing thinking UW.

Jukka

[Andrew]

Hi Jukka,

What a subject to think about, nothing like being prepared! I would doubt that it would have that much impact on the negative weight when in the water probably a kg or 2. The only difference would be the water which would now surround your camera and the reduction of the positive effect of air which would have been expelled from housing. As it is underwater, I would guess this should have very minimal effect and should be easy enough to bring up with your normal BC.

Where you would really notice it was when you were lifting the rig out of the water, but then if you hold it it an angle the water will run out and it will be the same as when you went in... well apart from having a completely wrecked kit!

Just my thoughts, lets hope it never happens!
Andrew

[sorvju-f]

Hi Jukka,

What a subject to think about, nothing like being prepared! I would doubt that it would have that much impact on the negative weight when in the water probably a kg or 2. The only difference would be the water which would now surround your camera and the reduction of the positive effect of air which would have been expelled from housing. As it is underwater, I would guess this should have very minimal effect and should be easy enough to bring up with your normal BC.

Where you would really notice it was when you were lifting the rig out of the water, but then if you hold it it an angle the water will run out and it will be the same as when you went in... well apart from having a completely wrecked kit!

[QUOTE]Just my thoughts, lets hope it never happens!

That is what I really hope too!

My video rig is top-side about 12 kg. In water it is very little positive ( its amazing ). It means that according Archimedes law replaced water weight is little bit less than the weight of the rig. Of coarse density of water is influencing to replaced water weight calculation.

If the air inside the housing is disappearing due the flooding, replaced water amount is reducing a lot...my quess is at least 80 %.

This means that my byoancy is changing about 10 kg to negative direction.

Is anybody agreeing with this?

Jukka

[solisti]

Do you mean that 80% of your video rig is air? Time to re-design the housing? Sounds awfully lot to me...??? Then again, what do I know... :o

[Ken Hawk]

Ken, haven't you had ever problems with insurance company:eek:

When i go to office of my insurance co, officers are running out and even planning to jump out of window:D

Sorry, but what is DSMB?

Jukka

1 of these Jukka, every diver should have one :D

http://www.divelife.co.uk/index.php?cPath=62_74

Thanks Ken

[Kelly]

[It means that according Archimedes law replaced water weight is little bit less than the weight of the rig. Of coarse density of water is influencing to replaced water weight calculation.

If the air inside the housing is disappearing due the flooding, replaced water amount is reducing a lot...my quess is at least 80 %.

Jukka

by "replaced water", I assume you mean "displaced" water? Displacement is a method used to measure volume, and since the size of this rig hasn't changed, the displacement will remain the same (according to the first part of definition below). What HAS changed is the density of the rig, though in my unexpert opinion, it hasn't changed much, basically reflecting only the differences in density between volume of the air (under pressure - which changes too) and volume of water. But don't forget the camera (highly dense) is unchanged, as is the houseing (also highly dense).

This is pulled from a definition off the internet:
any object floating upon or submerged in a fluid is buoyed upward by a force equal to the weight of the displaced fluid..... Buoyancy may be thought of as the density of a fluid relative to the densities of objects submerged in it

I doubt it would equal all that much weight. If you ever "experiment" let us know....:D I can't offer up my newly received D200 & housing for this one :D

just my .02 worth..... :p

[Kelly]

Warren's going to jump in here any minute to correct me.... :D :p :D

[sorvju-f]

by "replaced water", I assume you mean "displaced" water? Displacement is a method used to measure volume, and since the size of this rig hasn't changed, the displacement will remain the same (according to the first part of definition below). What HAS changed is the density of the rig, though in my unexpert opinion, it hasn't changed much, basically reflecting only the differences in density between volume of the air (under pressure - which changes too) and volume of water. But don't forget the camera (highly dense) is unchanged, as is the houseing (also highly dense).

This is pulled from a definition off the internet:
any object floating upon or submerged in a fluid is buoyed upward by a force equal to the weight of the displaced fluid..... Buoyancy may be thought of as the density of a fluid relative to the densities of objects submerged in it

I doubt it would equal all that much weight. If you ever "experiment" let us know I can't offer up my newly received D200 & housing for this one :D

just my .02 worth.....

This is interesting!

Sorry, I might make some errors due to my language skills!

I founded one pic which is explaining Archimedes Law

http://physics.weber.edu/carroll/Archimedes/images/buoyancy.gif

According this I have two ways to take my rig to water:

1 Everything sealed, no flooding...the amount of water is coming out of this pipe corresponds the outer diameters of my rig.

2 Backdoor open...water runs and fills open space inside the housing and also fills and destroys the camera and fills the dome ( also about 1 liter )...in this case water amount, which comes out of the pipe is smaler...my evaluation was 80 % less...( maybe better to say 60 to 80 % )...but this is something I am not voluntary testing;)

If the water amount coming out of this pipe is smaller the up-pushing figure is smaller..and the result is that weight is showing bigger number than in case 1.

Maybe I have to point the thing that size/volume/weight of my video-rig is not comparable to D200 system.

I try to get picture to understan the size of this rig...stand by.

Jukka

[sorvju-f]

1 of these Jukka, every diver should have one :D

http://www.divelife.co.uk/index.php?cPath=62_74

Thanks Ken

Ken, its POIJU and I have it + reel ( + 100 kg to carry ( and pay ) with me during diving trips ):D

Jukka

[sorvju-f]

This is interesting!

http://physics.weber.edu/carroll/Archimedes/images/buoyancy.gif

I try to get picture to understan the size of this rig...stand by.

Jukka

I couldn't resists:D

http://sorvjuf.1g.fi/kuvat/UW-chat/Video+rig+size+comparison+800.jpg/full

You can find a pen also which give you an idea about the size!

Jukka

[Andrew]

Wow this is all getting very complicated, but I like the drawings Jukka.

My thought is this as I am no professor, if you pick up a full bottle of water underwater it weights a fraction of the weight of it when out of the water. So if your housing is full of water, it should only weigh a fraction of the weight as well??

Maybe I have missed something...

[sorvju-f]

Wow this is all getting very complicated, but I like the drawings Jukka.

My thought is this as I am no professor, if you pick up a full bottle of water underwater it weights a fraction of the weight of it when out of the water. So if your housing is full of water, it should only weigh a fraction of the weight as well??

Maybe I have missed something...

Let me put the question this way:

How much the wage is showing if you put this filled bottle to wage under water

and

How much the wage is showing when you put this same bottle to wage top side

...solution is in the picture.

Maybe we are diving next time with wages and bottles and our padis thinks seriously to have new padi next time:D

Jukka

[Warren_L]

A lot would also depend on the rate of water intrusion. You might notice it getting heavy before it is even nearly full.

[Kelly]

Jukka,

I made the assumption that your housing leaked, not that the back door flung right open. Yes you will displace less water in this case, but I still don't think the change in over all density will cause you 10 or 12kg of additional weight that you'll have to deal with. You've exhausted what I can remember from grade 11 physics ;) and that was a very very long time ago:eek:

Your language is fine, btw. I have trouble with it too, and it's my first language, you should hear my Finnish! :D

[Jonathan Bird]

I think Jukka is on the right track. There is a fair amount of air in the housing which provides a fair amount of buoyancy. How else can you explain a housing that weighs 20 pounds on land being neutrally buoyant in water? You take the air out, the sucker is going to sink like a rock!

Jonathan

[Kelly]

There is no doubt in my mind that it'll sink, I believed it would sink in my first scenario, too. I just don't believe it will add the full surface weight of 10 - 12 kgs. :eek: That'd be scary! Archimedes Law still applies.;)

[lettsdive]

This is what happen to me, I own a Nikon D80 with ike housing, I have dual DS200 Strobes, the camera and housing weighs 13 lbs, I did not count the weight for the strobes and arms as the strobes did not flood so they should not be entered. I was doing a Dive on JB King, depth of 155 and a current of 2+knots, the camera had a total flood, a lot of words go through your mind in a hurry, so I abort the dive and came to the surface, with a safety stop, the only difference was I felt the extra weight you were carrying in your hands, as I didn’t want to let it hang from my safety tie off as it would of done more damage banging on the wall coming to the surface, it was not as easy to dump air from dry suit and BC as the extra weight from the loss of the air in the case made it more difficult, surprisingly you be surprised how awkward it becomes when you have case arms and strobes and now being negative, but as I mention the dive is not a easy one either so it made it more difficult. All said and done make sure you are not to over weighted and remember that the deeper you go the less buoyant your wet suit is as well, a lot of factors to think about, last option drop it go back later and retrieve it with proper gear and have insurance on it, remember your life is worth far more then a camera

Roy

[sorvju-f]

This is what happen to me, I own a Nikon D80 with ike housing, I have dual DS200 Strobes, the camera and housing weighs 13 lbs, I did not count the weight for the strobes and arms as the strobes did not flood so they should not be entered. I was doing a Dive on JB King, depth of 155 and a current of 2+knots, the camera had a total flood, a lot of words go through your mind in a hurry, so I abort the dive and came to the surface, with a safety stop, the only difference was I felt the extra weight you were carrying in your hands, as I didn’t want to let it hang from my safety tie off as it would of done more damage banging on the wall coming to the surface, it was not as easy to dump air from dry suit and BC as the extra weight from the loss of the air in the case made it more difficult, surprisingly you be surprised how awkward it becomes when you have case arms and strobes and now being negative, but as I mention the dive is not a easy one either so it made it more difficult. All said and done make sure you are not to over weighted and remember that the deeper you go the less buoyant your wet suit is as well, a lot of factors to think about, last option drop it go back later and retrieve it with proper gear and have insurance on it, remember your life is worth far more then a camera

Roy

Roy, I started this thread only like prethinking, because when you have went the case trough in your mind and then if it actually is happening the situation is not more 100% suprise.

You really have met the situation and it was great to hear your comments!

With video-rig the drawn situation is worse.

I second 100 % to your last sentence.

Jukka

[Papa Bear]

Well I know someone out there has a formula for this but I do know displacement , Archimedes's Principle, has an effect on a object in the water. I Know that we bring salvaged boats up from the bottom with as little as 250lbs of lift for a boat that would wight 2000 to 3000 lbs if you lifted it off its trailer! So yes displacement makes a difference! Once it floods it wights less than in air because of the displacement of all the parts in and outside displacing water at 8.3lbs per Gallon. So If the volume of the cavity is a Gallon, then maybe it will only wight whatever the volume wight would be? Like I said someone has the math! But it will not ever weigh what it would be out of the water, water is neutral in water!

[Kelly]

I second 100 % to your last sentence.
Jukka

I third it!:D ;)