buoyance arms review

[bmyates 3]

Do you buy that paint at a shipyard or something? Im in yachtie heaven here in the Virgin Islands so im sure I should be able to find some paint. Any brand/type that you can share so I can go look around?

 

Did you get your housing wet yet Bruce?

 

I've had my housing for several years and hundreds of dives, so I'm well aware of how negative it is. I made some "buoyancy collars" based on James' design a year or two ago, and those certainly help, but because they go around the port/extension rings, they make the camera want to always aim skyward, so I'm thinking these arms will be the perfect complement to a small collar...

 

As for specific paint, we have lots of boat shops around here, too, and I'm just going to go in and try to find one that sticks to almost anything and is reasonably durable, and ideally "flexes" a bit, since the floats will experience at least slight shrinkage over time as they compress a bit. Having said that, I don't plan to "over-think" the paint - I don't see it as serving any functional purpose; it is strictly cosmetic to cover up the white and make the floats look less like shark bait.

 

I'm looking for something spray-on, and if I have to re-spray them every third or fourth dive trip, that's no big deal...I just want doing so to be as simple as possible (e.g., I don't want to be mixing heavy-duty epoxy resins and having to apply it carefully with a brush). I'll let you know what I end up using...

[cor 0]

I've had my housing for several years and hundreds of dives, so I'm well aware of how negative it is.

 

I meant to say..did you get the arms wet yet Obviously you know your housing

 

 

I'll go get some paint soon and see how it works.

 

Cor

[ulcs 0]

Ultralight has in production a new buoyancy arm that has 2.5 times more buoyancy than their original

buoyancy arms. We hope to ship by May 1st.

 

There will be 8", 10", 12" 14" and 16" sections

 

Terry

[knakatsu 0]

Still waiting for my second order from 4th Generation...

 

Thanks for the pics Cor - is there any reason why you wouldn't want to cover both floats with a single piece of shrink tubing? That is what I planned to do once mine came but maybe I'm missing something. In terms of getting them dry, my thought was to make sure I soaked them throughly following a dive, then use compressed air to get them as dry as I can.

 

Of course, this is all optimistic theory at this point so comments are appreciated.

 

Kory

[cor 0]

Still waiting for my second order from 4th Generation...

 

Thanks for the pics Cor - is there any reason why you wouldn't want to cover both floats with a single piece of shrink tubing? That is what I planned to do once mine came but maybe I'm missing something. In terms of getting them dry, my thought was to make sure I soaked them throughly following a dive, then use compressed air to get them as dry as I can.

 

Of course, this is all optimistic theory at this point so comments are appreciated.

 

Kory

I suppose I could cover both at the same time, but I like to be able to switch floats around still. By covering only a single one they remain interchangeable. I bought some paint yesterday after talking to a local paint shop, and i'll paint 2 floats today, see if that holds up in sea water. I'll put them in a bucket of sea water overnight first.

 

Interesting to see ulcs is making new arms. Wonder if they'll stay with the same basic metal frame with an enclosed airspace or will also use some form of flotation device. I think the current ulcs buoyancy arms are quite heavy.

 

Cor

Edited February 27, 2007 by cor

[LChan 0]

the ULCS buoyancy arms (at least the larger ones) only compensate for the weight of the arms and clamps. 25% more buoyancy will not compensate that much for the weight of the housing/camera/lens/strobes.....

[Taxgeek 0]

I'd also like to know how Andy's plumbing insulation works.

 

I have used compressible foam before - "pool noodles". It compresses at depth, but it doesn't compress all the way down to zero. What I did was use enough so that my rig was neutral at depth (once below about 30 feet, it didn't seem to compress much more or change buoyancy much for some reason - probably related to structure of foam? dunno.) Anyway, the only problem was (1) it looked really stupid and (2) the rig was really really buoyant in shallow water. I wasn't sensitive to these problems because I don't care if people laugh at me and my dives at the time involved no tinkering around in shallow water trying to shoot. YMMV, however. But for certain types of dives, it worked, and pool noodles, tie wraps and duct tape are really cheap.

 

Would you estimate plumbing insulation to be more or less compressible than a pool noodle? A pool noodle is definitely less compressible than a closed cell backpacking sleeping pad (ensolite or ridge rest style).

 

Susan

 

 

 

Let us know how that works uw, Andy. I'm afraid you will find that soft foam insulation like that compresses dramatically at depth, and will be virtually worthless below 50 ft or so. The closed-cell foam people use that seems to work is "hard," stiff stuff that you can't compress with your fingers/hands, and thus resists compression under pressure. OTOH, you might find that your insulation works fine at shallow depths, in which case we'd all like to know!

[ulcs 0]

the ULCS buoyancy arms (at least the larger ones) only compensate for the weight of the arms and clamps. 25% more buoyancy will not compensate that much for the weight of the housing/camera/lens/strobes.....

 

My original post has been edited, a typo. The new arms will have 2.5 times more buoyancy arms than the original ones.

 

Please re-read my original post

 

terry

[james 0]

A good durable flexible marine epoxy paint is what I used on my collar. It's called "bootstripe" paint and available at most boating places.

 

You can also easily paint/coat your foam with polyesther resin and then a coat of hardener. Then paint them. Again - that only takes a few hrs.

 

Cheers

James

[bmyates 3]

A good durable flexible marine epoxy paint is what I used on my collar. It's called "bootstripe" paint and available at most boating places.

 

OK, I've spent 15 minutes chasing Google references, and can't find a single online source for "bootstripe pain" - got any online sources, James?

[cor 0]

I went to a local paint store and talked to the owner about this issue. He recommended just trying a cheap acrylic polyurethane paint. I paid a few bucks for a 29 oz can that he whipped up for me in a darkish blue. I did only 1 dive with it so far, but the paint looks untouched. I went to 140 feet to see if the paint would crack as the floats compressed, but nothing happened. The guy told me this paint stretches well. I'll do some more testing, but this paint seems to work just fine, especially if I do 2 or 3 layers of it.

 

Cor

[james 0]

I got mine at West Marine which is now Boat US

 

Cheers

James

[drsteve 6]

Here are my buoyancy arms. I followed the lead a friend and others on these forums. They consist of capped PVC tubing cable tied to my ULCS arms. It isn't pretty but it is cheap, effective, and doesn't change buoyancy at depth. Total cost was < $20.

 

Unfortunately since the PVC is soft, the paint chips off pretty easily. I probably should have left them white, but it appealed to my vanity though to have it beautiful if only for a little while.

 

It is almost neutral in the water. I still need to do a little more fine tuning to get the balance perfect. It is much more manageable this way than before I added the floats. The arms are 12" and 8". I put double floats on the 8" arms. I also have 5" arms, but I have pretty much discontinued using them.

 

[NWDiver 42]

Somebody may have asked this but I will be "The Jerk" and try to go cheap...

 

Can you just buy the floats and jam them over existing TLC or ULCS arms?

[knakatsu 0]

Somebody may have asked this but I will be "The Jerk" and try to go cheap...

 

Can you just buy the floats and jam them over existing TLC or ULCS arms?

 

 

Thrify question but the STiX arms have removeable ball ends to allow the slotted floats to slip on to the arms with a snug fit, and are much smaller in diameter than TLC/ULCS arms.

 

By the time you bored out the floats enough to get them on to the TLC arms, over the the ball ends, you would have lost a majority of the float volume (buoyancy) and, they would be extemely loose on the arms.

 

Kory

[malodiver 0]

Cor,

Just back from the Voyager trip. 1300 miles !!!! Got some great shots. I used John's arms on my Sea Cam D2X system and I dont need physical therapy on return from the two week trip. They worked fantastic. I needed two long arms on each side for the 9 inch wide angle port. Perfect neutral bouancy. WOW what a new experiance.

As I was afraid of, the short arms were not enough to float the Macro port. John rigged up a floatation collar for the Macro port that I trialed for use with the arms. It worked great. Perfect ballance. The two together provided neutral bouancy. He will probably have that available for those that need more than the arms for Macro. I cant believe how much easier it was to focus the 105 on those Pigmy Seahorses, when I wasnt trying to hold up that heavy camera.

Jack

[knakatsu 0]

Cor,

Just back from the Voyager trip. 1300 miles !!!! Got some great shots. I used John's arms on my Sea Cam D2X system and I dont need physical therapy on return from the two week trip. They worked fantastic. I needed two long arms on each side for the 9 inch wide angle port. Perfect neutral bouancy. WOW what a new experiance.

As I was afraid of, the short arms were not enough to float the Macro port. John rigged up a floatation collar for the Macro port that I trialed for use with the arms. It worked great. Perfect ballance. The two together provided neutral bouancy. He will probably have that available for those that need more than the arms for Macro. I cant believe how much easier it was to focus the 105 on those Pigmy Seahorses, when I wasnt trying to hold up that heavy camera.

Jack

 

 

Jack,

 

Thanks for the great report. Just a few questions - What arm length(s) and floats did you use for both WA and macro?

 

I am thinking of adding a StiX arm and float to my focus light to compensate for the macro port but don't know if it will be enough. Thank you.

 

Kory

[bobf 0]

I would begin any buoyancy compensation project by first deciding on the goal. IOW, do you want your rig to be positive, neutral, or slightly negative underwater.

 

I would next determine how negative the rig is underwater before any modifications. This could be approximated with the aid of a hand held "fish" scale (spring or digital style). Attach a fishing line from the hook of the scale to the camera rig. Immerse only the rig into water (keep scale out of the water) and hold it as motionless as possible (if the camera is "bobbing" up and down, so is the answer ). If fresh water is used, keep in mind that salt water will make the rig more buoyant (3%?).

 

An alternative (preferred?) method for finding the underwater weight of an object is to determine its actual displacement (volume) (*see below*) .

 

If the weight of the water that is displaced weighs more than the dry weight of the rig itself, then the rig will be positively buoyant ( why boats float).

 

Once you have determined the rig's underwater weight, then determine the buoyancy of the material you choose to add to your rig. If you are purchasing a brand new strobe arm system, StiX offers a guide to the buoyancy of each component they offer.

 

If you wish not to purchase a new arm system and are adding to strobe arms already owned, then buoyancy of the chosen material can be determined in the following manner:

 

choose a known size of buoyant material (volume in cubic inches)

weigh the known volume dry

 

Salt water weighs 0.037 pounds per cubic inch. Multiply the volume of the buoyant material (in cubic inches) by the weight of water (in cubic inches) it will displace. Subtract the dry weight of the material from that subtotal and the result will be how much lift is created.

 

For best results, choose materials that will not compress when exposed to recreational dive depths. As materials compress, they lose volume and subsequently the ability to displace water.

 

Example of a material that does not compress at recreational dive depths:

 

A 4' by 8' sheet of 1/2" Core Cell A weighs 5 lbs per cubic foot (12x12x12= 1728 cu in.)

Core Cell A weighs @ 0.0028 pounds per cubic inch

 

Since water weighs 0.037 pounds per cubic inch and Core Cell A weighs @ 0.003 pounds per cubic inch, then 0.034 pounds of lift can be created with every cubic inch of Core Cell A added to the underwater rig.

 

Lets assume you wish to add 1 pound (16 ounces) of buoyancy to your rig using Core Cell A. Divide the target of 1 pound by the benefit lift of 1/2" thick Core Cell at 0.034 pounds per cubic inch. According to the math, @ 29.4 cubic inches of Core Cell A would increase buoyancy by 1 pound.

 

If you had a single 12" long strobe arm, you'd probably only wish for 10" of linear material placed on it so that free movement was not impeded upon by the strobe arm clamps found at either end of the arm. If you were to cut and install 4 pieces of Core Cell A measuring 10" by 1.25" by 0.5 inches around the arm (encapsulate the arm), 25 cubic inches would be added to each strobe arm. 25 cubic inches of Core Cell A would yield a net benefit of (25 times .034) 0.850 pounds or 13.6 ounces, about 2.5 ounces shy of the target.

 

If you had a pair of 8" long strobe arms:

 

a 6" by 1.25" by 1/2" section of Core Cell A would yield 3.75 cubic inches of displacement per section

4 sections per strobe arm would yield 15 cu in per strobe arm

15 cu in realizes a lift benefit of (15 times .034) 0.51 pounds or 8.1 ounces per arm

therefore two 8" long arms with the above modification would yield a benefit of @ 1 pound of lift. If your dual strobe arm system consisted of 4 x 8" arms including the above modification, then 2 pounds of lift could be created.

 

Paint and fastening system used to attach material to strobe arm (glue, cable ties, plastic nuts and bolts, wire, o-rings, etc) should be chosen carefully as they will affect the end result.

 

* To determine Volume:

 

Choose a container of known size. A common household pot for boiling large quantities of water would be sufficient as long as the sides of the pot were straight and not angled outward. For example, my wife has a straight sided pot that measured (diameter) 13" across. Its radius therefore is 6.5". In order to determine the displacement of my rig, I filled the pot with 7" of water. I next placed a ruler along the interior side of the pot, vertically into the water. As mentioned, the water depth read 7". I then placed each component of my rig separately into the water and noted the increase in height of the water on the ruler.

 

Say once the component was immersed, the height of water as noted on the ruler increased one inch, from 7" depth to 8" depth .

 

To determine volume of a cylinder, the following formula is used:

 

V=L*Pi*r²

 

The increase in height of the water inside the pot will now be noted now as the Length of the cylinder

 

Volume equals Length times Pi (3.14) times the radius of the pot squared

V=1 (height increase of water) times 3.14 times 6.5²

V=1*3.14*42.25

V=132 cubic inches

 

The object that I placed into the pot of water that increased the level of water by 1" therefore displaces 132 cubic inches of water.

Edited March 12, 2007 by bobf

[H2Oplanet 0]

Two Questions:

 

(1) Can someone explain how best to make a buoyancy collar for a flat port when shooting macro? i shoot macro with the 100mm Canon as well as the 180mm Canon. Just purchased the Stix system and I like the idea of using the collar in conjuction with the buoyancy arms for macro which would allow me to limit arm lengths and reduce bending moments.

 

(2) You guys got me concerned about Sharks now since there are many species here in North Carolina plus I'm joining JASA/Wetpixel for the Bahama shoots in July. I can use techniques in this thread to cover the white floats with black but shouldn't I really be more conerned with my large, shinny SeaCam housing and the two large SeaCam 250 strobes??

 

Please advise...

 

Scott

[seagrant 4]

If you had a pair of 8" long strobe arms:

a 6" by 1.25" by 1/2" section of Core Cell A would yield 3.75 cubic inches of displacement per section

4 sections per strobe arm would yield 15 cu in per strobe arm

15 cu in realizes a lift benefit of (15 times .034) 0.51 pounds or 8.1 ounces per arm

therefore two 8" long arms with the above modification would yield a benefit of @ 1 pound of lift. If your dual strobe arm system consisted of 4 x 8" arms including the above modification, then 2 pounds of lift could be created.

 

Paint and fastening system used to attach material to strobe arm (glue, cable ties, plastic nuts and bolts, wire, o-rings, etc) should be chosen carefully as they will affect the end result.

 

Bobf you are a wonder with the math!! I do admire that ability you have!

 

As you know I tried the corecell on the 8" ULCS arms and it did not displace the weight that was calculated. I'm sure it works out on the "drawing board" but in real water situations......, well obviously in my real-water situations I got 1.6 oz of buoyancy per section for the 8" ULCS arms. Ryan spent a lot of time and effort making the core cell floats and I felt terrible for all his caring and efforts that they didn't displace the nearly 4oz that he thought they would. They only displaced slightly more than the existing ULCS buoyancy 8" arms. Of course the corecell material could be stacked but it proved very unwieldy for me personally (but that was just for me). I did have another WetPixel member help me with some of the tests. We were very careful and only used one or two zip ties so as not to add weight to the tests.

 

I do feel a corecell buoyancy collar in addition to some sort of float on the arms would be beneficial. Problem is some ports have focus knobs that can make that difficult I'm told. Still I'm hoping to get a buoyancy collar made for me at some point (it has been promised...... ....)

 

As you probably know I've used two of the Patima BCs, one on each inside 8" arm and find them very easy to live with. Every buoyancy solution has some drawbacks but the drawbacks for me personally with the Patima BCs were less than stacking the arms with so much foam (6 sections per arm wasn't even enough), and I didn't want longer arms because of the difficulty of handling them for me.

 

Of course not everyone would feel as comfortable with the Patima BCs and adjusting their air volume once in a while but I do, I, along with a number of others who shoot a lot, find it quite easy (and actually sort of fun to fiddle with, like a lift-bag or something like that). And I don't have to adjust it that much, sometimes not at all.

 

Hopefully I can use those BCs on the arms in conjunction with a corecell collar for the Subal 105vr port which is quite heavy. And I might even try a couple of the new ULCS buoyancy arms in addition when they are released. Granted I do need the rig a little lighter than most divers.

 

Upshot is I'm really glad John is distributing these Stix arms and floats, etc. I'm glad ULCS is making new and more buoyant buoyancy arms. I'm glad you are doing the math to find a corecell solution and I'm happy Ryan Canon cares so much to help people get their rigs less negative. I'm also happy Patima made a simple BC float to attach to the housing or arms. All these things and others are steps in the right direction. Of course it would be a lot easier for all if the housings just had a bit more air space designed in at manufacturing time to result in less negative housings, etc. But that is a wish and what we are dealing with is what is here and now.

 

Again, thanks for the math and all the suggestions!

 

Take Care, Carol

[bobf 0]

Bobf you are a wonder with the math!! ........I got 1.6 oz of buoyancy per section for the 8" ULCS arms...........

 

Carol,

 

Thank you for the kind words.

 

When you first contacted me it was in the middle of my busy season..............I wish I could have been more helpful at the time...........

 

I do not fully understand yet what size Core Cell (HxWxL) is meant when you refer to "section" in your post. When you state you realized 1.6 ounces per "section" for the 8" strobe arm, can you please define "section". Is that for each single piece of Core Cell A (if so, what HxWxL)) or for a set of four pieces as described in my post:

 

a 6" by 1.25" by 1/2" section of Core Cell A would yield 3.75 cubic inches of displacement per section

4 sections per strobe arm would yield 15 cu in per strobe arm

15 cu in realizes a lift benefit of (15 times .034) 0.51 pounds or 8.1 ounces per arm

 

If I quickly do the math, a 6" by 1.25" by 1/2" piece of Core Cell A will displace 3.75 cubic inches of water.

3.75 time 0.034 (weight of water minus weight of core cell per cubic inch) equals 0.1275 or about 2 ounces of lift per 6 by 1.25 by 1/2. I arrive at this conclusion based upon acknowledged fact (Archimedes Principle).

 

I do agree however that what takes place on the blackboard and what takes place in real life does not always jive.........

 

And I strongly agree with you that all of this discussion is extremely important...........especially including the fact that strobe arm manufacturers are addressing the issue with renewed vigor.

 

One important note to consider with whatever direction anyone is to take, whether starting from scratch with a brand new strobe arm system or modifying an existing system. Length matters!!!!!! The longer the arm, the more surface available to add "streamlined" buoyancy.

 

btw, I should also mention as a clarification. There are several types of Core Cell, each with their own performance specifications and subsequently letter "suffix". The particular type I refer to in my post is called "Core Cell A". There is also a "Core Cell S", "Core Cell T", Core Cell P", etc............

[cor 0]

btw, I should also mention as a clarification. There are several types of Core Cell, each with their own performance specifications and subsequently letter "suffix". The particular type I refer to in my post is called "Core Cell A". There is also a "Core Cell S", "Core Cell T", Core Cell P", etc............

Also, within the different types there are different densities. Core Cell S has several densities, and if you get the wrong one (very dense, usable for deep sea rovers) you will get very bad buoyancy properties as opposed to less dense versions of core cell S or even A.

 

When I spoke to a boat maker in Amsterdam he told me that the dense versions are the most commonly sold ones because they're used in boats. He had a hard time getting me the lightest version (usable upto 300 meters I think).

 

But, eventually I ended up buying the stix arms, as this thread shows

 

Cor

[bobf 0]

Also, within the different types there are different densities. Core Cell S has several densities, and if you get the wrong one (very dense, usable for deep sea rovers) you will get very bad buoyancy properties as opposed to less dense versions of core cell S or even A.

 

When I spoke to a boat maker in Amsterdam he told me that the dense versions are the most commonly sold ones because they're used in boats. He had a hard time getting me the lightest version (usable upto 300 meters I think).

 

But, eventually I ended up buying the stix arms, as this thread shows

 

Cor

 

For more information on Core Cell options, visit:

 

http://www3.gurit.com/marine/products_corecell.php

 

If you download the Core Cell S .pdf file, you'll notice as Cor has mentioned, that it is available in three variations, ranging in average density from 9.3 lbs per cubic foot to 19.7 pounds per cubic foot. As previously stated, the Core Cell A that I've experimented with has an average density of 5 pounds per cubic foot. My first samples of Core Cell A were from the remnants of a 51' sailing vessel being constructed near my home port. More specifically, off cuts from the sailing vessel's structural bulkheads. This is tough stuff!

[cor 0]

For more information on Core Cell options, visit:

 

http://www3.gurit.com/marine/products_corecell.php

 

If you download the Core Cell S .pdf file, you'll notice as Cor has mentioned, that it is available in three variations, ranging in average density from 9.3 lbs per cubic foot to 19.7 pounds per cubic foot. As previously stated, the Core Cell A that I've experimented with has an average density of 5 pounds per cubic foot. My first samples of Core Cell A were from the remnants of a 51' sailing vessel being constructed near my home port. More specifically, off cuts from the sailing vessel's structural bulkheads. This is tough stuff!

Did you ever try out what the max depth is for core cell A300? The main issue right now with the floats from the stix arms is that the max depth is around 110-130 feet. After that the floats start compressing. The biggest benefit is its weight, next to nothing. Id like to try some core cell A300, which is probably a bit better than what the stix arms use. I can probably cut floats out of A300 myself.

 

Cor

[bobf 0]

Did you ever try out what the max depth is for core cell A300?

 

Cor

 

No.

 

But if you wouldn't mind allowing "math" to get wet for us again...............

 

According to the Corecell A spec sheet, A300 compression strength is rated at 65 psi.

 

Next, calculate pressure (psi) at your target depth of 130 feet..........

 

Air pressure at the surface = 14.7 lbs

descend the first 33 feet and add 14.7 lbs

descend another 33 feet and add 14.7

descend another 33 feet and add 14.7

descend another 33 feet and add 14.7

 

total depth equals 132 feet = 73.5 lbs psi

 

To determine specifically how deep you can go in salt water to reach 65 pounds absolute psi, first subtract 14.7 to compensate for pressure at the surface (1ATM):

 

65 psi - 14.7 psi = 50.3 pounds per square inch

 

We know a single square inch column of salt water 33 feet deep weighs 14.7 pounds. Every foot of salt water therefore weighs .445 pounds (14.7/33=.445). To find how much water is needed then to exert 50.3 pounds of pressure per square inch, divide 50.3 by .445. Answer= 113 feet.

 

At 113 fsw, 14.7 psi will be exerted by the air in the atmosphere and another 50.3 pounds per square inch will be exerted by the salt water equaling a total psi of 65..........the tested limit of Corecell A300. After that point, according to the spec sheet, A300 should begin to compress...........just as the StiX buoyancy foam reportedly does.

 

Corecell A500 has a compression strength rated at 135 psi. Using the same formula as above, first subtract 14.7 to acknowledge the first ATM, yielding 120.3 psi. Divide 120.3 by .445 equals 270.33. Corecell A500 should be fine until a salt water depth of @ 270 feet is reached.............according to how I read the specs.......and do the math..........

 

Id like to try some core cell A300, which is probably a bit better than what the stix arms use. I can probably cut floats out of A300 myself.

 

As far as the ability to cut floats from A300, I can state through experience that 1/2" Corecell A500 cuts relatively easy with a standard utility (matt) knife (2-3 passes). Corecell A500 can also be shaped easily with sand paper, rasps, belt sander, etc.......I would therefore "assume" you would have no trouble.

 

I have also cut 3/4" thick Corecell A500 and 1" thick Corecell (unknown letter suffix because it was another "leftover" piece) with a standard utility (matt) knife.

 

hth,

b