My buoyancy solution

My A1U, Amphibico housing, and monitor are fairly neutral, but when I add my lights it sinks like a brick. I read an article by James Wiseman about a buoyancy collar he had built for his camera, and decided to follow his lead. I purchased some four pound density closed cell foam, fiberglass, and resin from fiberglasssupply.com, and began my first fiberglass project. I'm attaching the float to the top of the video housing with velcro straps attached to the mount screws. In my salt water pool it is still slightly negative, but should be OK in the Ocean. I've tried to attach a .jpeg file if you want to take a look. Now I just need to get to the Ocean and give it a try.

Vic

Very nice!

Cheers

James

Great idea...see you got one of the last A1 EVO'S with mechanical controls along with left hand piece controls. They don't make them like that anymore.

Did you see our review we did on it?

You will find that 4lb. density foam is going to crush too easily, and then will not have the same buoyancy as on the surface. I have used 8lb. density foam, and it is only usable down to about 40 feet. The higher the density, the greater the crush (pressure) resistance.

Dan

I used 6# density foam down to 100' and it performed well. It did crush a little, but not very much. Maybe a 5% loss at most for me. YMMV depending on the shape and coating.

Cheers

James

I coated most areas with two layers of fiberglass, and probably three coats of resin. I have a couple rough spots, so I may sand a bit and add another coat of resin. I used the 4 lb core, since that's what had been used in the article, and down to 100 ft, with about one millimeter of deflection. I guess I will not know until I try it and see how it holds up to 4 atmospheres of pressure.

I've had the housing for a little over a year, and thought the review you did was great Wagsy, and I still want to try out some of the manual settings you recommended. Most of my diving has been in Bonaire, Roatan, and Mexico, so the water has been clear enough that light has not really been a problem. I've only used the lights on one night dive, and it was way to heavy, so I hope this will help.

Vic

Hope it works well for you as it looks like you did a really nice job on it.

Dan

You will find that 4lb. density foam is going to crush too easily, and then will not have the same buoyancy as on the surface. I have used 8lb. density foam, and it is only usable down to about 40 feet. The higher the density, the greater the crush (pressure) resistance.

Dan

I assume therefore, based upon your actual experience, that all close cell foam is not created equal.

For instance, Core-Cell "A" at 4lb density ( a cubic foot of 4# density foam would weigh approximately 4 pounds) is compression rated at approximately 90 psi. If one atmosphere is equal to 14.7 psi at sea level, then according to how I interpret the spec sheet, Core-Cell "A" at 4# density should not begin to compress (crush under pressure) until beyond a depth of 165 feet has been reached.

(90psi/14.7=6.12 atmospheres.......subtract one atmosphere for surface pressure......5 (atm) times 33 (feet of water depth per atm) equals 165 feet...........

spec sheet may be found here:

http://www3.gurit.com/pdfs/corecell/Corecell_A_Foam.pdf

All that said, which I admit is completely based upon theory* and not real world conditions, if your actual experience suggests that a particular 8# density foam compresses at 40 ft, then I would request knowing which foam in particular you tested so that we can avoid it if possible.

regards,

b

*I have tested bare (no fiberglass or resin) Core-Cell "A" 500, compression rated at 135 psi. It has performed well on my strobe arms, showing no signs at all of compression, down to at least 100'

bobf-

I hope your analysis is closer than what others are predicting. I used the "Last-A-Foam" from fiberglasssupply.com, the same that James had used in his article, but I did not get a spec sheet for it. I doubt that I will exceed 100', and most of the time probably much less.

Thanks for all the comments, I'm glad to see others are interested in my little project.

Vic

OK, I found the spec sheet at http://www.generalplastics.com/uploads/pdf...Package2004.pdf?

which shows 73 PSI at 75 degrees F, so it looks like I should be OK to about 130 ft. Sounds like James was right on target, since there is no reason to use heavier foam, which would reduce the buoyancy.

bobf - I don't know exactly what kind of foam I have. I have 2 blocks from a local supplier, one marked 6# and the other 8#. The 8# foam is very hard and difficult to compress by hand. I built a float for a heavy wide angle lens that I no longer own. The deeper I went, the more it shrunk, to the point of being almost useless at depth. So yes I guess all foams are not created equal. Texas Divers float should work well as long as the fiberglass shell has no leaks, otherwise 4# density foam by itself would not work well. (Admission - I wrote my original reply in haste during a short lunch break, and did not realize he was coating it with fiberglass)

videodan-

I don't expect the fiberglass and resin to contribute much to the compressive strength since it's strength is actually along the surface, not normal. The fiberglass and resin is more to protect the foam. The foam should hold up to the water pressure even if no coating was applied using the compressive strength in the spec. As you noted the material properties are not related to the density. That is why the material bobf linked to has a deeper depth calculated, since his was good to 90 psi, and mine is only 73 psi. I guess the foam you have must have a much lower compressive strength property, which is not to be unexpected. It would be interesting if you can get a spec sheet to see if the numbers work out.

Vic

I can see a serious flaw in your setup. I bet when you get home from a dive trip, you find that all you have is hours and hours of footage of the same turtle...

Just got back from our trip to the FL keys. Didn't get to do all the diving we had planned due to waves being a bit larger than my liking when trying to get on and off the boat with video gear. The dives we did do in Key West had visability of about 40 ft, and the reef was in pretty poor shape. On the upside, I did finally get to do a "sea trial" on my float that I had built for my video housing (see picture in OP). It was about as perfect as I could hope for. I had it down to just over 90 ft, with no visible deformation, and the buoyance was just slightly negative, so the rig would slowly sink if I let go, and stay upright. One thing that I did notice is that even with the float located just above the center of gravity of the housing and light combo, it takes some effort to shoot up or down. The camera likes to stay level, and pans easily horizontally. I would think that the folks that mount the floats to the light heads would really notice a bigger effort required for the up and down shots due to the distance from the center of gravity, so please sound off with your findings.

On another note, I did have about 1 tablespoon of water seep into one of the light heads, so I'm going to replace the O-rings, and hopefully no permanent damage occured. Does anyone out there have a set of these old lights (made by Amphibico) they are parting out, and would be interested in selling one, or both of the light heads as spare parts?

Thanks

Vic