Sinking housing - maths problem and advice sought !!

Anyone out there able to help me?

I've been using a SeaPro housing for my video camera but have found that it
is quite difficult to hold steady as it is quite seriously negatively
buoyant - i.e. bloody heavy, ready to go in the water it weighs approx 7.5kg
(don't even think about the baggage allowance problems...)

The internal dimensions are as follows:
Diameter - 55mm
Length - 180mm

The overall external length is a little more due to the Optolite port on the
front and the rear 'door' which is a clear laminate block. There are also
external handles mounted from a block on top of the cylinder.

I've been pondering how to reduce some of the negative buoyancy and it has
been suggested that layer(s) of thick wetsuit type material velcroed to the
housing might help but I am not sure that this will have much effect given
the overall weight of the unit. I guess any solution needs to be removable
in order to allow drying etc.

Any sensible (humorous also welcome, but I'd prefer sensible!) suggestions?

Regards,
Sam

Sam Broad wrote:
> I've been pondering how to reduce some of the negative buoyancy and it has
> been suggested that layer(s) of thick wetsuit type material velcroed to the
> housing might help but I am not sure that this will have much effect given
> the overall weight of the unit. I guess any solution needs to be removable
> in order to allow drying etc.

The problem with neoprene is that it compresses and what will
be buoyant at the surface will be nothing like as good at depth.
It is quite a problem to find something that is consistent in
deep water. The old Bathyscaph people use paraffin I believe,
wood might work if you can get cherry or one of the light
ones. Plastic foams will collapse. The other problem is that
you will need quite a lot of it by volume - several litres.

Perhaps revising the handles so it is less of a problem to hold
might be a more profitable line to follow.

nigelH

Thanks - I guessed that the volume might be an issue. As the housing is Ali
a lighter material would have been less of a problem - the camera itself is
a small proportion of the weight. I don't film very deep - generally only
where I can use ambient light - the torch that goes with it is bloomin'
unwieldy and adds a great deal *more* weight so I rarely use it! I'm also
doing some weight training before my next trip at Xmas to build up the old
muscles! If I can't devise a reasonable solution and Popeye tactics don't
work then it maybe time to reinvest...

The handles are about half way down either side, supported by a bar across
the top and give a good couple of inches clearance from the housing. It is
quite easy to handle in the water and I don't want to resort to any form of
harness that would make it difficult to dump - although I currently use a
lanyard (with an extension piece so that I can get it away from my body to
film) and clip to a ring on my BCD just in case I need both hands free... So
not sure how I could better that - anyone suggest any better method?

Regards,
Sam

"Nigel Hewitt" <news@REMOVETHISnigelhewitt.net> wrote in message
news:41596dfc$3@news.star.co.uk...
> Sam Broad wrote:
> > I've been pondering how to reduce some of the negative buoyancy and it
has
> > been suggested that layer(s) of thick wetsuit type material velcroed to
the
> > housing might help but I am not sure that this will have much effect
given
> > the overall weight of the unit. I guess any solution needs to be
removable
> > in order to allow drying etc.
>
> The problem with neoprene is that it compresses and what will
> be buoyant at the surface will be nothing like as good at depth.
> It is quite a problem to find something that is consistent in
> deep water. The old Bathyscaph people use paraffin I believe,
> wood might work if you can get cherry or one of the light
> ones. Plastic foams will collapse. The other problem is that
> you will need quite a lot of it by volume - several litres.
>
> Perhaps revising the handles so it is less of a problem to hold
> might be a more profitable line to follow.
>
> nigelH
>
>

> Any sensible (humorous also welcome, but I'd prefer sensible!)
suggestions?

Helium?

CAS

On Tue, 28 Sep 2004 15:24:37 +0100, "Sam Broad" <snb@enterprise.net>
wrote:

>Anyone out there able to help me?
>
><snip>
>
>Any sensible (humorous also welcome, but I'd prefer sensible!) suggestions?
>
>Regards,
>Sam
>
>
Attach a self injlating dsmb to it.

Keep adding air as you do down to keep it neutral.

Better still, add a drysuit autodump to the top of the dsmb then
adjust it to maintain neutrality on the way up also.

Could reduce the length of the smd to the maximum needed to achieve
buoyancy, or leave it at full length and fully inflate it at the end
of the dive (shut the auto-dump first) to act as your smb, taking your
camera up with it and saving you having to lug it aroung on the
ascent.

Suspect this may just slip out of the sensible catagory.

David

On Tue, 28 Sep 2004 17:31:33 +0100, "CAS"
<calumscottREMOVETHISBIT@yahoo.com> wrote:

>> Any sensible (humorous also welcome, but I'd prefer sensible!)
>suggestions?
>
>Helium?
>
>CAS
>
>
Stupid boy.

Put some expanded polystyrene inside the housing to make it more
bouyant...

But, the reality is that there probably aint much you can do about it.
Any sort of float needs to be crushproof.

Most "good" housings are neutral or slightly negative in the water.

Pete S.

> I've been using a SeaPro housing for my video camera but have found that
> it
> is quite difficult to hold steady as it is quite seriously negatively
> buoyant - i.e. bloody heavy, ready to go in the water it weighs approx
> 7.5kg
> (don't even think about the baggage allowance problems...)
>

I know this is not useful for the topic but take your video camera on to the
plane in its housing as you are allowed one camera per person not included
in the baggage allowance. Just pretend you cannot take it out for security
reasons!!

Not helpful on original post though!

Sorry

Bari Pollard.

"Sam Broad" <snb@enterprise.net> wrote in message
news:hBf6d.24$Hw5.17@fe61.usenetserver.com...

> The handles are about half way down either side, supported by a bar across
> the top and give a good couple of inches clearance from the housing. It is
> quite easy to handle in the water and I don't want to resort to any form
> of
> harness that would make it difficult to dump - although I currently use a
> lanyard (with an extension piece so that I can get it away from my body to
> film) and clip to a ring on my BCD just in case I need both hands free...
> So
> not sure how I could better that - anyone suggest any better method?
>
> Regards,
> Sam
>

http://www.steadicam.com/ maybe???
--
MarkW

nospam to scuba to reply

"Mark Williams" <mark.nospam.williams@ntlworld.com> wrote in message

> http://www.steadicam.com/ maybe???
> --
> MarkW

Those things dont even like heavy rain.........

"Keith Manning" <NOSPAM@tesco.net> wrote in message
news:Z6i6d.345$z%3.308@newsfe1-win.ntli.net...
>
> Those things dont even like heavy rain.........

No that's just the operator

MarkW
nospam to scuba to reply