LocLine Arms

[Teamcasa]

...PVC is nice as a finished product, but it's not easy to experiment with unless you have a lot of time and PVC.

This is where math is your friend.

I determined the total negative buoyancy of my lights was X (about 1.2lb per light).
The area displaced by my ABS tubes was Y

Water volume for Y

X = 2.4 lbs
Y = 80 CI = 2.9 lb of water

Result slightly positive.

ABS, like PVC will not change buoyancy at recreational diving depths. Noodles and neoprene will.


Dave

 

[mdmbike to scuba]

Thanks Dave for the math ahhhhh LOL. Plan "C" Im going to go with neoprene wraped around the arms. First to give more strength to the arms and add some buoyancy "I hope". Next, is to cut the noodle to fit some how. If I get some time before I leave Im going to get back into the pool to test it. What do you guys think? Mark

 

[ronscuba]

I was good at math back in the day. LOL.

What's the easiest way to determine how negative a system is ? Lights, arms, housing, lens etc.. And how do you determine displacement of the PVC ?

 

[Teamcasa]

I was good at math back in the day. LOL.

What's the easiest way to determine how negative a system is ? Lights, arms, housing, lens etc.. And how do you determine displacement of the PVC ?

Pi*R2*L

But technically, you would have to minus the actual weight of the ABS(black) or PVC(White) pipe and caps.

Dave

 

[merxlin]

Thanks Dave for the math ahhhhh LOL. Plan "C" Im going to go with neoprene wraped around the arms. First to give more strength to the arms and add some buoyancy "I hope". Next, is to cut the noodle to fit some how. If I get some time before I leave Im going to get back into the pool to test it. What do you guys think? Mark

You might try wrapping the arms with foam pipe insulation first putting a layer of neoprene over it. It is the same material as the pool noodles, already has a hole in the middle, and comes in a variety of sizes at most Home Depots, Lowes and hardware stores. It should be more buoyant than the neoprene.

 

[mdmbike to scuba]

Merxlin Thanks for the idea. I may have to stop by home depots and see what the they have. Mark

 

[mdmbike to scuba]

Ok here are the arms with my cut up wet suit. I hope

 

[ronscuba]

Wow, those are long light arm segments.

 

[mdmbike to scuba]

The arm are only 15links. Ron, think they are to long? Mark

 

[ronscuba]

Just want to be clear, I am only a hobbyist, and definitely not an expert.

I know some like a longer arm for more flexibility in controlling where the light comes from, for example lit from the side, but in my own experience, I haven't found a need for long arms. It may have to do with my lamps having a wide beam (appx 90 degrees).

Do you find yourself fully extending the arms when you film ? If so, forget my comment and don't fix what isn't broken. If you rarely fully extend them, you might want to try shortening them. That might help keep the arms from moving.