12 replies to this topic

[james]

I think writing up the review may have been more work than making the collar! :-)



I hope you enjoy, and the review is useful.

Cheers
James

[segal3]

Because my Seacam uses a very robust thread mounted port, I wasn’t worried about the strong buoyant force popping off my macro port underwater. This may be a concern for others though, so take this into consideration if you decide to put buoyancy onto your rig.

This has been in the back of my mind since you originally mentioned the buoyancy collar, so I'm glad you at least mentioned it.

Keep in mind that just about every flat port has a great deal of buoyant force, regardless of whether or not there's a buoyancy collar on it, so I'm not sure what the addition might do. Generally, to minimize chances of ripping the port from its mount, I suggest trying to keep any additional buoyancy as close to the mount as possible (less torque).

I do like the results however. Nice work.

~Matt Segal

[james]

Hi Matt,

Thanks for the feedback. Another factor to consider is whether your lens touches the inside of the port at all. On my Seacam housing, the focus gear meshes with a drive in the housing, so no. With my Aquatica and Ikelite housing, the lens and gear support each-other in the front, where the focus gear/control meshes with the lens. In that case, the lens and camera are mounted to the housing and the buoyant force from the port can actually be held DOWN by the lens. Weird, eh?

Cheers
James

[segal3]

In that case, the lens and camera are mounted to the housing and the buoyant force from the port can actually be held DOWN by the lens.  Weird, eh?

<{POST_SNAPBACK}>

True, it is that case with the 100mm macro with my setup. Then, however, you not only have to worry about stressing the port, but putting a lot of force on the lens mount

~Matt Segal

[bobf]

Exciting to see this new forum expand with such a well thought out project and one not yet addressed by an underwater equipment manufacturer.

This is an excellent addition to the DIY library.

thanks for sharing, james......

[Marc Furth]

Hi James,

Nice to see others interested in DIY projects and your looks very professionally made.

My thought was could you have strapped or saddled a PVC pipe with end caps on top of your port extension? It might not look as good as your masterpiece but could save a lot of time in fabrication.

Marc

[bobf]

Marc,

My initial attempts were in that direction. I seem to recall for every additional pound of 2" PVC, only a pound or two of lift was created. There was also the size factor. I tested 2" pvc only after smaller diameters provided insignificant benefits. otoh, As james pointed out, for every pound of closed cell foam used (depending on type) you could create 15 pounds of lift (16 lbs minus the weight of the foam product)

When I created my buoyancy arm system with 1/2" Core-Cell, I made a 16 pound point and shoot dual strobe rig (four pounds negative in water) weigh about one pound submerged.

I agree with your placement strategy. As james pointed out in his article, the buoyant material should be above the ballast to avoid the system's desire to turn belly up.

regards,
bobf

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[bmyates]

I hope you enjoy, and the review is useful.

<{POST_SNAPBACK}>

James,

Excellent write-up, and thanks for taking time to write it! I can honestly say that the only significant issue I have with the Seacam housing is "wrist fatigue" with macro lenses due to its considerable negative buoyancy, and your collar seems to be an excellent solution! I plan to order some of the 1-inch 6lb Last-a-foam (which you seem to recommend over the 4lb you used) today!

One question: is there any reason (other than aesthetics) not to simply cut several pieces of the 1" foam into "rings" and coat/use each ring separately, sliding onto the port however many rings are needed? I'm thinking that doing so would facilitate an "adjustable" amount of buoyancy depending on the lens/port combination used on a given dive (e.g., one or two rings when using a 50mm lens, three or four rings when using a 100mm or 150mm lens, which require port extensions). In addition to more flexibility, separate rings would also seem to totally eliminate the need for glue/resin (assuming boot stripe paint will adhere directly to the foam). Having been through the entire process, do you see any flaws in that approach?

[james]

Bruce,

I think that's a fabulous idea! I'm going to steal it right away...:-)

Make a few different sized rings (different OD) and then use velcro tape on each one so that you can stick them together to make different size collars. You can buy velcro adhesive tape at most sewing places.

Another thing that was suggested was to do a light fiberglassing over the rings during the coating process. It would be pretty easy using loose fiber (not fabric) and wouldn't add much weight.

You should coat each ring with resin at the bare minimum - otherwise, they will get totally crunched and broken right away.

Thanks for the good feedback btw, I appreciate it.

Cheers
James

[Kelpfish]

James,

Where'd all that wine go in your wine rack?

Joe

[james]

Wine is made to be drunk Joe, not just stored. Gawd, now I'm going to have to go back and see what other personal items you can see in that photo. Good, I don't see the blow-up doll!

Cheers
James

[Kelpfish]

Nice

[davephdv]

That looks just like the collar my dog use to have to wear to keep him from chewing himself to death.