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Balancing an 8’’ dome (filled with air)


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#1 softnuance

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Posted 15 January 2009 - 10:57 AM

Ikelite 8’’ dome port
Ikelite body for Canon 10D

I tried this material in my bath tub. The air in the the dome brings the whole housing into a 45 degree horizontal position. (lens looking at the sky.)

Am I supposed to balance it? I know about the Near-neutral buoyancy but this time it’s about the orientation of the housing.
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#2 Drew

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Posted 15 January 2009 - 11:44 AM

I moved this to the appropriate forum.
I too am trying to figure out a way to customize the balance of the housing, especially since my new housing will be used for video occasionally. I'm not familiar with Ikelite mounts so I don't know how much weight it will take before the weight affects how the o-ring seats.
The best way to get it balanced without making the housing negative is to add a little bit of weight to the bottom of the dome lens shade and some buoyancy to the housing body. This should tip the housing forward enough. You'll have to experiment with the balance of weight and buoyancy floats. For buoyancy float suggestions, search the forum for Stix and foam as keywords. Good luck.

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#3 james

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Posted 15 January 2009 - 12:00 PM

When I needed to balance out my housing - I used an ankle weight around the extension ring. Of course, I wouldn't recommend it with a housing that doesn't have a secure port mount.

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#4 softnuance

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Posted 15 January 2009 - 12:19 PM

An ankle weight sounds scary. The Ikelite port is held by 2 tiny plastic pieces.

I think i'll fix 2 (90 degree) metal bar (fixed to the handles) that will hold weight without touching the body or the port.
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#5 cdoyal

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Posted 15 January 2009 - 01:17 PM

If I can get my rig neutral, I'm so happy I don't care about balance!
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#6 CADiver

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Posted 15 January 2009 - 09:47 PM

If I can get my rig neutral, I'm so happy I don't care about balance!


I second that ... now if it's neutral, isn't it already balance ?
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#7 james

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Posted 16 January 2009 - 06:36 AM

No.

A system can be neutral but not balanced. If the center of buoyancy is not above the center of gravity the system will rotate until it is.

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#8 Drew

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Posted 16 January 2009 - 08:42 AM

To add to what James said, trust me, having a well balanced rig keeps your mental and physical balance as well... especially now with the 5D2 shooting video as well.

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#9 CADiver

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Posted 16 January 2009 - 09:51 AM

To add to what James said, trust me, having a well balanced rig keeps your mental and physical balance as well... especially now with the 5D2 shooting video as well.


I agree but let me rephase it, if it's neutral, isn't it easier and lighter to manipulate the rig into position, so balance or not would be less significant ? I suppose if it's not balance, one hand shooting would be very difficult ...
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#10 rbailey

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Posted 18 January 2009 - 01:17 AM

Good point and question, will watch this thread and answers with interest.

I've a Ikelite 8" it's neutrally bouyant but tips/rotates heavily.
After a 2 or 3 hour dive (Rebreather) I suffer very badly with wrist strain from fighting it vertical all the dive.
I've thought about some more weight in the base and then arm floats to give a turning moment but not done anything yet.

Cheers,
Richard B.
Camera : Canon 350 D. (8MP, D-SLR, APS-C.)
Housing : Ikelite eTTL hosuing.
Ports : 6" Dome, 8" Dome and Flat port and selection of extenstions.
Lenses : Sigma 10-20mm, 17-70mm Macro, 105mm Macro (with +4 diopter).
Stobes : 2 x Ikelite DS 125.
Arms : Ikelite, 18 inch quick release (LHS) and 8"+6" standard (LHS).
AND a Yellow Box Of Delights to breath from undewater and loads of other really fun stuff.


Check out ther results at :-

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#11 bvanant

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Posted 18 January 2009 - 11:20 AM

I agree but let me rephase it, if it's neutral, isn't it easier and lighter to manipulate the rig into position, so balance or not would be less significant ? I suppose if it's not balance, one hand shooting would be very difficult ...

Depends a lot on how not neutral the system was and how much righting moment the dome port adds to the system. In my hands, a slightly neutral housing that sits upright means a lot less arm and wrist strain than a neutral housing with a big dome port that needs to be twisted. YMMV

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#12 Bandycootz

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Posted 03 February 2009 - 01:31 PM

Good point and question, will watch this thread and answers with interest.

I've a Ikelite 8" it's neutrally bouyant but tips/rotates heavily.
After a 2 or 3 hour dive (Rebreather) I suffer very badly with wrist strain from fighting it vertical all the dive.
I've thought about some more weight in the base and then arm floats to give a turning moment but not done anything yet.

Cheers,
Richard B.



Hi Richard,
Just reading ur comments and noticed your set up very similar to mine. Just about to use the 10-22 in the ikelite housing with 8" dome port, but the gear sleave and focus ring don't fit. I see you have a similar wide angle and wondering what I am missing? Is there a specific extension or additional gear sleave? Only came with a standard size one?

Cheers
Steve

#13 rbailey

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Posted 03 February 2009 - 07:49 PM

Hi Richard,
Just reading ur comments and noticed your set up very similar to mine. Just about to use the 10-22 in the ikelite housing with 8" dome port, but the gear sleave and focus ring don't fit. I see you have a similar wide angle and wondering what I am missing? Is there a specific extension or additional gear sleave? Only came with a standard size one?

Cheers
Steve


Hi Steve,

To avoid Hijacking responded here :-

http://wetpixel.com/...showtopic=28619

Cheers,
Richard B.
Camera : Canon 350 D. (8MP, D-SLR, APS-C.)
Housing : Ikelite eTTL hosuing.
Ports : 6" Dome, 8" Dome and Flat port and selection of extenstions.
Lenses : Sigma 10-20mm, 17-70mm Macro, 105mm Macro (with +4 diopter).
Stobes : 2 x Ikelite DS 125.
Arms : Ikelite, 18 inch quick release (LHS) and 8"+6" standard (LHS).
AND a Yellow Box Of Delights to breath from undewater and loads of other really fun stuff.


Check out ther results at :-

http://www.images-underwater.net/



#14 Maarten_NL

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Posted 04 February 2009 - 12:55 AM

Ikelite 8'' dome port
Ikelite body for Canon 10D

I tried this material in my bath tub. The air in the the dome brings the whole housing into a 45 degree horizontal position. (lens looking at the sky.)

Am I supposed to balance it? I know about the Near-neutral buoyancy but this time it's about the orientation of the housing.


If you can add bouyancy to the rear of the set, neoprene sleeve for flasharms for example, to raise the rear. and then weight to the bottom to neutralize the bouyancy.
UW Setup: Canon EOS 50D / 60mm Macro f2.8 / Tamron 17-50 f2.8 / Sea&Sea YS27DX / Seatool housing