Insiration or not to inspiration :)

Hi,

I am returning to diving after a short absence, now that my son is a little
older. I used to dive with twin 12's on air or Nitrox, after a while of not
diving, I sold the regs, twinset, wings and backplate.

I'm notw thinking that an Insipration may be the way to go, I like the idea
of the reduced weight over a twinset and for the dives that I like it has
reduced deco advantages for me.

Can anyone recommend an instructor that can get me through the course and
also sell me a unit. I'm based in Dublin so any Irish instructors would be
good but apart from that my 'home' is in the Midlands so anywhere in and
around a few hours of Birmingham would be good.

Cheers,

Matt

In article <cf7ova$bcv$1@kermit.esat.net>,
Matt Lemon <matthew@jacklemon.com> wrote:

>Can anyone recommend an instructor that can get me through the course and
>also sell me a unit. I'm based in Dublin so any Irish instructors would be
>good but apart from that my 'home' is in the Midlands so anywhere in and
>around a few hours of Birmingham would be good.

The Ambient Pressure Diving web site has a list of Instructors -
http://www.ambientpressurediving.com/ and you can always give Nicky or
Sarah at the factory a call to get the latet information.

Gordon

On Mon, 9 Aug 2004 12:44:17 +0100, "Matt Lemon"
<matthew@jacklemon.com> wrote:

>I'm notw thinking that an Insipration may be the way to go, I like the idea
>of the reduced weight over a twinset and for the dives that I like it has
>reduced deco advantages for me.

I like the idea of reduced weight, pity it's not true

Laz

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A foolproof method for sculpting an Elephant:
First, get a huge block of marble. Then, chip away
everything that doesn't look like an Elephant.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Change "nospam" to "ntlworld" to reply.

Lazarus X <lazarusx@nospam.com> wrote:

> "Matt Lemon" wrote:
>
>> I'm notw thinking that an Insipration may be the way to go, I like the idea
>> of the reduced weight over a twinset and for the dives that I like it has
>> reduced deco advantages for me.
>
> I like the idea of reduced weight, pity it's not true

Sad but true. A twinset is seriously negative and my 300/10 were
negative with attitude but the ol' turtle is about neutral and you have
to make up the difference in lead.

Saying you ought to try before you buy seems sound but we know
it's addictive so once you have a go it's pretty predictable you will
just max out the credit card and get one anyhow.

nigelH

On Mon, 9 Aug 2004 16:45:03 +0000 (UTC), "Nigel Hewitt"
<news@REMOVETHISnigelhewitt.co.uk> wrote:

>Lazarus X <lazarusx@nospam.com> wrote:
>
>> "Matt Lemon" wrote:
>>
>>> I'm notw thinking that an Insipration may be the way to go, I like the idea
>>> of the reduced weight over a twinset and for the dives that I like it has
>>> reduced deco advantages for me.
>>
>> I like the idea of reduced weight, pity it's not true
>
>Sad but true. A twinset is seriously negative and my 300/10 were
>negative with attitude but the ol' turtle is about neutral and you have
>to make up the difference in lead.

The counter lungs are the problem. With OC, your buoyancy constantly
changes with lung volume and the effective buoyancy will be driven by
the average between fully inhaled and fully exhaled (or slight towards
fully inhaled if you are a breath holder). With CCR, your effective
buoyancy will be driven by volume that you run the counter lungs at
which is typically about 3/4 of max lung volume. The problem is all
that extra gas requires lead to sink it.

IMO the key to rebreather comfort (i.e. avoiding Inspiration back) is
to get the weight of the weight belt and the lower part of the unit.
I initially used the weight pockets but I retired them at the request
of my back. I then run weights down the side of the harness for a
while but I have now moved to a backplate.


Laz

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A foolproof method for sculpting an Elephant:
First, get a huge block of marble. Then, chip away
everything that doesn't look like an Elephant.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Change "nospam" to "ntlworld" to reply.

"Lazarus X" <lazarusx@nospam.com> wrote in message
news:lehfh0tuhqlkl9cuhg3tnm743egs253g47@4ax.com...

> The counter lungs are the problem. With OC, your buoyancy constantly
> changes with lung volume and the effective buoyancy will be driven by
> the average between fully inhaled and fully exhaled (or slight towards
> fully inhaled if you are a breath holder). With CCR, your effective
> buoyancy will be driven by volume that you run the counter lungs at
> which is typically about 3/4 of max lung volume. The problem is all
> that extra gas requires lead to sink it.
>
> IMO the key to rebreather comfort (i.e. avoiding Inspiration back) is
> to get the weight of the weight belt and the lower part of the unit.
> I initially used the weight pockets but I retired them at the request
> of my back. I then run weights down the side of the harness for a
> while but I have now moved to a backplate.

I'm sure you didn't mean to write it the way that it reads -

Your counter lungs should be run at minimum loop volume, certainly to leave
the surface you'll need the whole loop empty if you're correctly weighted,
then the counter lungs should only contain enough for one full breath: This
is minimum loop - the minimum amount to refresh your lungs, any less and you
run the risks of CO2 retention, any more and you'll use more O2, more gas in
the counterlungs requires more O2 to reach the set PO2 and chances are that
you'll be dumping more excess gas that you don't need with that O2 in it (by
volume) controlling the buoyancy as O2 injection duration will be greater.

All buoyancy control is achieved using the buoyancy control device.

Breath holding is a bad on a RB as it is OC

When you achieve the correct trim in the water (Single, Twin or on a RB)
you'll find that instead of the weight hanging on your hips, it will remain
for the entire dive, pulling in the small of your back across your backbone
and hence why we then start looking at weight distribution, a stainless
steel plate being one aspect of that.

A lot of the deeper RB divers and cave divers put the weight inside the
case, _BUT_ they generally carry ditchable in their pockets as well,
remember if you are correctly weighted at the start then ditching just 2KG
(just a set of ankle weights in your thigh pockets), is enough to keep you
on the surface.

Best

/F
http://www.e-aquanauts.com Technical Training.

In article <lehfh0tuhqlkl9cuhg3tnm743egs253g47@4ax.com>,
Lazarus X <lazarusx@nospam.com> wrote:

>>>> I'm notw thinking that an Insipration may be the way to go, I like the idea
>>>> of the reduced weight over a twinset and for the dives that I like it has
>>>> reduced deco advantages for me.
>>>
>>> I like the idea of reduced weight, pity it's not true
>>
>>Sad but true. A twinset is seriously negative and my 300/10 were
>>negative with attitude but the ol' turtle is about neutral and you have
>>to make up the difference in lead.
>
>The counter lungs are the problem.

Actually they're not. Assuming you are running them at minimal volume
on a CCR, anyway.

The problem is really the rest of the loop - ISTR that it's the best part
of 6 litres, maybe more, and as far as we are concerned, it's rigid, so
it's volume isn't going to change. Even with 2.5Kg of Sofmolime in it,
theres still that additional lead required to sink it.

Gordon

Gordon Henderson <gordon@lion.drogon.net> wrote:

> The problem is really the rest of the loop - ISTR that it's the best part
> of 6 litres, maybe more, and as far as we are concerned, it's rigid, so
> it's volume isn't going to change. Even with 2.5Kg of Sofmolime in it,
> theres still that additional lead required to sink it.

Hey Gordon,

I have it in my head from somewhere that a standard Inspitartion
is just about neutral straight out of the crate with tanks, 'lime but
no lead but I don't know where I got that idea from.

Can you confirm or deny?

nigelH

On Mon, 9 Aug 2004 21:37:32 +0000 (UTC), gordon@lion.drogon.net
(Gordon Henderson) wrote:

>In article <lehfh0tuhqlkl9cuhg3tnm743egs253g47@4ax.com>,
>Lazarus X <lazarusx@nospam.com> wrote:
>
>>>>> I'm notw thinking that an Insipration may be the way to go, I like the idea
>>>>> of the reduced weight over a twinset and for the dives that I like it has
>>>>> reduced deco advantages for me.
>>>>
>>>> I like the idea of reduced weight, pity it's not true
>>>
>>>Sad but true. A twinset is seriously negative and my 300/10 were
>>>negative with attitude but the ol' turtle is about neutral and you have
>>>to make up the difference in lead.
>>
>>The counter lungs are the problem.
>
>Actually they're not. Assuming you are running them at minimal volume
>on a CCR, anyway.
>
>The problem is really the rest of the loop - ISTR that it's the best part
>of 6 litres, maybe more, and as far as we are concerned, it's rigid, so
>it's volume isn't going to change. Even with 2.5Kg of Sofmolime in it,
>theres still that additional lead required to sink it.

Good point, I had never actually though of it that way. There is a
lot of gas in the rest of the loop which is dead easy to demonstrate
by manually injecting O2 and seeing how long it takes to hit the
cells. For me it is just as I breath in on the third breath.


Laz

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A foolproof method for sculpting an Elephant:
First, get a huge block of marble. Then, chip away
everything that doesn't look like an Elephant.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Change "nospam" to "ntlworld" to reply.

In article <cf8rdl$d8d$1@titan.btinternet.com>,
Nigel Hewitt <news@REMOVETHISnigelhewitt.co.uk> wrote:
>Gordon Henderson <gordon@lion.drogon.net> wrote:
>
>> The problem is really the rest of the loop - ISTR that it's the best part
>> of 6 litres, maybe more, and as far as we are concerned, it's rigid, so
>> it's volume isn't going to change. Even with 2.5Kg of Sofmolime in it,
>> theres still that additional lead required to sink it.
>
>Hey Gordon,
>
>I have it in my head from somewhere that a standard Inspitartion
>is just about neutral straight out of the crate with tanks, 'lime but
>no lead but I don't know where I got that idea from.
>
>Can you confirm or deny?

Can't do either as I don't really know...

My unit has integrated weight pockets so it will sink rather rapidly if
I let the gas out and it's been a long time since I've been on a RIB
with a weight belt so I don't really know...

I also have the old fibreglass case on mine still, so that might
make a difference...

I have seen someone[1] remove the back off a new case underwater and it
seemed fairly neutral underwater, so the new case might not be an issue...

Lets see.. Manifold (brass, -ve), Sofnolime (-ve), pillar valves
(-ve) cylinders (+ve) airhoses (-ve) handsets (-ve) headset, sensors,
batterys (-ve) and breathing loop and canister (+ve) So maybe it does
all balance up...

I do know that I need more or less the same amount of lead on my unit
as I used to use when diving twin 10's, although I've recently removed
the backplate and gone back to the standard harness without adding any
more lead to the weight pouches... (which might explain why I felt a bit
floaty at Teignmouth.. Hmmm. Ah well, I'd better get used to it, I guess!)

Gordon
[1] Big Mike from the factory. Do not dive with this man!!!