Too Negative

[BamaGirl 0]

After reading a post from last June about negative vs. positive preferences, I'm almost afraid to write-in. But, I am in the Beginner's Forum so take it easy on me - okay?

 

I have an Olympus C-5060, Ikelite housing, a DS-50 and a DS-125. When I had just the DS-50 it was manageable. After adding the 125, the weight is too much for me. Perhaps for men it's not a problem, but for this woman with an elbow injury it is!

 

Are there any quick (I leave for Bonaire in a week) & inexpensive fixes?

 

Thanks

[anthp 0]

Could you add some high density foam (like from a yoga/exercise matt) and wrap it around the strobe arms? I have seen someone else with that setup.

[BamaGirl 0]

Thanks Anthony. How would you secure it - zip ties?

[anthp 0]

Sounds good to me. I think the person I saw had actually found some tubular foam (like the insulation you sometimes see around water pipes) and slid it down the arms over the balls. The foam was kept in place by the arm clamps. Cable ties would work a treat though I reckon.

[cor 0]

One thing ive seen someone use is fishnet floats. Or swimmingpool floats. Those little round floats that hold up a net on the surface. They dont compress much, so at depth they maintain their buoyancy. He used some kind of elastics to just wrap it around his strobe arms.

 

Cor

[james 0]

For shallow diving, you can get those colored "pool noodles" at Walmart or equivalent store. Cut to size and slip over your strobe arms. They will work well down to perhaps 60 feet. Anything deeper you need hard foam.

 

Cheers

James

[dawktah 0]

I'm learning myself but are you in fresh or marine water?

 

My Ikelite housing was neutral in marine, so I'm just wondering what will happen when I add the DS-125. Currently in Chicago and need to have all I need when I get to BVI.

[james 0]

The DS125 has weight in water. Not sure exactly how much, but it's around 6 oz I'd guess.

 

Cheers

James

[BamaGirl 0]

Dawktah,

I'm in saltwater. My Ikelite housing and DS-50 were manageable in saltwater - using one hand in current conditions. After adding the DS-125 I was very surprised at the increased weight. I've used the DS-125 for a photo class (pool) but haven't yet been in saltwater. Thankfully currents aren't a problem in Bonaire, but I'm quite sure I won't be able to get any one-handed shots without some added bouyancy.

 

Thanks James - I'll try it!

[paninaro 0]

Note that if you've only tried the DS-125 in fresh water, it will seem lighter than that in salt water (because it's displacing the salt as well).

[bobf 0]

Good guess james! I calculated that the DS 125 weighs around 5 ounces in salt water.

 

Fill a straight sided round bucket almost full of water.

Place a ruler standing vertically inside.

Measure the height of the water.

Add a DS 125

Note new height of the water.

 

We can now determine the volume or displacement of a DS 125 (or any other negatively buoyant object)

 

Volume(displacement in this case) =Length times Pi times radius squared

 

The bucket I used measured 13 inches across. It's radius therefore is 6.5. I put 7.5 inches of water in it. I gently placed a DS 125 in the bucket and the water level raised one half (0.5) inch on the ruler.

 

The volume of the DS 125 then would be calculated:

 

0.5(the increase in height of the water) times 3.14 (pi) times 6.5 squared (the radius of 13 inches)

 

0.5(L) times 3.14(PI) times 42.25(6.5 squared)=volume

0.5x3.14x42.25=66.33

 

The answer, 66.33 is presented to us in cubic inches.

A cubic inch of salt water weighs .59 ounces

For every cubic inch of water displaced, .59 ounces of lift (buoyancy)is created.

 

the DS 125 displaces (volume) about 66.33 cubic inches of water. Each cubic inch of salt water weighs about .59 ounces. 66.3 times .59 ounces equals around 39 ounces of weight displaced. The DS weighs around 44 ounces on land. Subtract the 39 ounces of water displaced and the net result is it's negative weight in water of around 5 ounces.

 

the above calculations are based upon the Archimedes Principle of water displacement......

[james 0]

Better yet, hang the DS125 from a spring scale and submerge it all the way. Read the weight off the scale...:-)

 

Cheers

James

[Ana Rodriguez Blanco 0]

Hi BamaGirl! Maybe in this moment you don't want to spend more money in new arms for your strobes. But in a future, if you want to change them, there are positive buoyancy arms, Ultralight has that kind of arms. For your trip you can try with tubular foam, but if this keeps on being a problem you could try that solution.

 

Regards

[kathymm 0]

We use sections of wetsuit arms. Cut holes in them where the sync cord and mounting bracket are.

 

We are lucky enough to have a "local" wetsuit shop to get the neoprene arms from. You could use an old wetsuit you don't mind cutting up but it might not have the bouyancy of a new piece of neoprene.

 

Have fun in Bonaire!

Kathy

[danschmitt 0]

If you are going deep and foam comression is expected to be bad, you can do capped PVC pipes (tie wrap or tripod mount.) I'll leave the air displacement of a capped pipe math to other so inclined posters.

[Kelpfish 15]

How negative is the camera system?

 

Joe