Dive Knife Handle Material for Buoyancy?

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Emphasiski

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Jun 27, 2010
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I'm a diver, and have dropped many dive knives prying something up, off or out of something, however these knives were dropped in Guam, where the visibility is damn near endless. Needless to say...the knives were easy to find.

Since then I've moved back to my home town of Spokane, WA. The fresh water here is murky and has limited visibility. If I drop a knife, I'd at least like it to sink extremely slowly, or pop to the top.

Can anyone make any recommendations as to how I could achieve this affect when I get around to making my dive knife?
 
My first recommendation is that you wrap a lanyard around your wrist when you use your knife. That works above and below the water's surface.

Second is to make the knife itself out of a lightweight stainless.

The third recommendation is to design the handle so that it has an extremely boyant portion made of a very brightly colored material.
 
Being a diver I am sure you know that what floats at the surface may not float 60' down. I suggest mocking something up that would be the same weight as your planned knife, bring it down and let go to see what happens. With enough experimenting you may be able to get something that is neutral at your normal dive depth, buoyant above that, and slow sinking below.
I lost a few dive knives while diving and not realized it till I returned to the boat. One I got whipped around by a current while exiting a wreck and slammed into the hull. When I got back to the boat all I had was the two straps and half a sheath. The others I think I just didn't put back in right and they fell out.
 
Los Angeles said:
My first recommendation is that you wrap a lanyard around your wrist when you use your knife. That works above and below the water's surface.

Second is to make the knife itself out of a lightweight stainless.

The third recommendation is to design the handle so that it has an extremely boyant portion made of a very brightly colored material.
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A lanyard isn't always feasible. Dive knives are normally held on or near the ankle for comfort and "out of the way" convenience. I've made hundreds of paracord bracelets, lanyards etc, and for the life of me can't think of one worth tying on a dive knife.

unky_gumbi said:
Being a diver I am sure you know that what floats at the surface may not float 60' down. I suggest mocking something up that would be the same weight as your planned knife, bring it down and let go to see what happens. With enough experimenting you may be able to get something that is neutral at your normal dive depth, buoyant above that, and slow sinking below.
I lost a few dive knives while diving and not realized it till I returned to the boat. One I got whipped around by a current while exiting a wreck and slammed into the hull. When I got back to the boat all I had was the two straps and half a sheath. The others I think I just didn't put back in right and they fell out.
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Very true, but something that is buoyant at 10-20 feet, will at least sink slowly or be neutrally buoyant at 60, giving me time to snatch it before it falls and sinks in the mud. I was thinking of a lean rubber handle with a layer of 4-5mm neoprene. I wasn't sure if anyone has made one that is sure to work.
 
I think cork might compress and loose its buoyancy at depth. My brother was on a submarine: Foam coffee cups left in a void outside the hull later appeared as minitures once everything was squeezed out of them.

There is a material I'ver heard of which consists of tiny glass spheres full of air or vacuum. They can be cast into a resin to form fairly strong, depth resistant material of excellent buoyancy. I don't know how big a handle it would take, but making a minimalist blade would also help.

You could also try placing something like an empty medicine bottle in the tang and casting it in securely enought to prevent compression. That's the principle behind the submarines with the cast bubble crew area.

Ideally, something approaching neutral buoyancy would be ideal - it wouldn't rocket away from you up or down if dropped.
 
Two things I can think of. Foamed aluminum, although it's rather hard to come by. Foamed PVC is much easier to find, maybe a stacked K-bar type handle out of it. . . .
 
Here you go... :D
images
:D

It wouldnt be easy... but What about making a hollow handle, or some other kind of void and filling it with a tiny helium balloon? kind of a pontoon handle...

Jason
 
You would have to do some testing, but whatever steel you use you would have to skeletonize a lot under the scales, cork sounds good, make the handles extra thick as if it were for somebody with arthritis.try not to put too much finish on it, the more it soaks up, the less buoyant it is. Try the neoprene too. Also horse stall mat rubber. Keep us updated as to what you do and how the testing goes. Check with rod building supply type websites to get the blocks of cork big enough for scales. Who knows, you might have to laminate the material to get it thick enough.
 
I'm going diving today. I've cut a couple blanks, and my mom gave me a bunch of wine bottle corks. I've also got a patch of neoprene, some tire rubber and I also covered one of the blank tangs in some caulking compound as kind of an off the wall idea.

For the most part I'll just be duct taping the materials to the blanks, and testing the buoyancy every 20 feet. I'm being told there's a chunk of the lake that goes near 140ft in depth. So I'll go until I get to cold.
 
Have you thought about a hollow handle or maybe even filling a tube handle with something that floats like the stuff Boston Whaler puts inside their boats?
 
Try some closed cell foam maybe?

McMaster has a variety...

Buy a piece, cut enough to mimic a handles volume, dive to depth and see how much weight it'll float.
Fishing weights would do nicely...

A knife could then be built to suit...

Of course it'll be different in saltwater than fresh, different depths, etc...
 
I think cork might be the best bet, but if that does not work, perhaps a re-sealed CO2 cylinder from a pellet gun could be built into a handle
 
I've been a professional diver for a long while. Fortunatley, I've never lost a knife. I think that you could come up with a design that had a skeletonized handle filled with foam, etc. However, I think the knife would likely have to be extremely large to accomodate enough bouyant material to actually make it float. I'd probably go with a good sheath and maybe an lanyard.
 
zaph1 said:
I remember seeing floating lanyards that would keep the knife bouyant.
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After my tests yesterday, I think this might be the best idea. Although it would probably function as a fob more than a lanyard for my wrist.

As for how yesterday went, I made it to 80 feet and the chills came real fast, I was able to test the cork then I had to get out. Went and rented a dry suit, and went back down later that afternoon. There must have been a current or something going on in the water. I went back to the same spot and at 80ft it was just way to dark and murky to see much of anything. So I stopped at 80 and did what I could...
I don't know how long cork would last in terms of serviceability [might fall apart], and it gets pretty compressed down there. The neoprene seemed to slow the rate of decent but not by much as I went farther down, it might be a comfortable handle cover. The tire rubber was a bad idea, I lost that blank...it sank to fast. Last but not least, I'm not putting any caulking compound in a knife, I couldn't figure out how to incorporate that into a sturdy handle.
 
Emphasiski said:
After my tests yesterday, I think this might be the best idea. Although it would probably function as a fob more than a lanyard for my wrist.
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What about something like this bobber on the end of the lanyard so if you did lose it you'd be able to see a light easier? I've never used one of these so I don't know how it would work, but I just think something illuminated could be helpful.
 
Glad you liked my idea. Although, I'm seriously considering a foamed PVC stacked handle with a stick tang. If I build it someday, I'll let you know.
 
MT Borg said:
Hollow handle filled with Helium ? ;-p

Maybe compressed Helium ??
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As soon as you compress something, you increase its density, thereby lowering its buoyancy.

Hence things like cork becoming less buoyant at greater depths...
 
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