Material for buoyancy finetuning ( everyday materials )

[John Marr]

Hello,
I am in the process of finetuning my pipegun's buoyancy ( tip heavy ) and I am looking for the best material.
The demands would of course be best buoyancy with the smallest volume.
I tried cork, because I have some lying around, and I like the look and how easy it is to work with ( sanding, cutting, glueing ), however it soaks up water and loses buoyancy as well as being less buoyant then other foams.
I also tried the foamy sole of some old sneaker I found, but that one was too soft, so it lost most of its buoyancy at depth.
I also have only limited access to well stocked shops, so I am looking for "everyday" materials that are light, buoyant and strong as not to get compressed at depth.

Thanks for all info!

 

[popgun pete]

Polyurethane closed cell foam is what you need where the bubbles are not interlinked with holes. One company used to sell foam cores for their spearguns and from memory it was Immersion in France. Of course the barrel tube has to be the correct ID to ensure a snug fit. Another approach is sealing plugs and these range from simple rubber bungs with a slight taper that you hammer into place and "O” ring sealed bulkheads that just slide in and are then held by external anchor bolts, usually via a loop around the bolts or screws that hold the handle and muzzle on the gun. Again they have to fit your barrel tube. For external tube support there are foam gadgets that slide onto the barrel tube, I have seen them in polystyrene, but they can suffer from impacts. There are also neoprene sleeves, but they add to drag on the barrel if they are nylon coated as in wetsuit material. Wood can be added as side stocks that are strapped to the barrel, you see them used on the Riffe Metaltech gun as an option.

http://www.imersion.net/index.php?lg=1&chx=20&fam=9&prod=81&ligi=

Then there is EVA foam like this stuff https://www.ebay.com.au/itm/HART-RO...209534?hash=item3af34ffffe:g:ekAAAOSwKEhck6Sw

 

[John Marr]

Hello,
well I have sealed the tube before without any big issues. What I am looking for is just the material to add on the outside to give the tip a bit more lift. I am not in an area with lots of shops and materials, so i will have to do with what I can find.
Will try some hardish shoe sole material next.

 

[popgun pete]

Hello,
well I have sealed the tube before without any big issues. What I am looking for is just the material to add on the outside to give the tip a bit more lift. I am not in an area with lots of shops and materials, so i will have to do with what I can find.
Will try some hardish shoe sole material next.

Well you have the internet and buying on-line is very simple. Most buoyancy strap on flotation is for adding flashlights.

 

[John Marr]

Buying online is easy, getting it delivered nearly impossible here
Will try to find where else EVA is used. Thanks.

 

[cdavis]

What should work is find a fairly light wood (not balsa, too soft) ,white pine maybe. shape it too your needs, seal the wood with thinned epoxy and it should work fine. After a few years, you might have to make it again due to water injection.

 

[John Marr]

Thanks.
Well I already uses light wood ( from an old clothes hanger ) to make little wings to help stabilizing the muzzle a bit. This works quite nicely. However the tip is still too tip heavy. So I wanted to attach some foamy pieces under the "wings". Will try a hard piece of flip-flop sole next.

 

[japppo]

I've never understood how adding foam inside a tube would increase buoyancy (imersion). I guess reducing the mass of the rubbers or spear is not an option? Maybe add weight on the handle for balance? Or add ping pong balls on the wings, sure would look weird if no other help...

 

[John Marr]

Yes, foam inside a tube only makes sense if you cannot seal it properly. jay for ping pong balls gave me an idea though:
I will take one down and see how it behaves with 4 bars on it

 

[popgun pete]

I've never understood how adding foam inside a tube would increase buoyancy (imersion). I guess reducing the mass of the rubbers or spear is not an option? Maybe add weight on the handle for balance? Or add ping pong balls on the wings, sure would look weird if no other help...

You cannot always assume that the tube barrel is sealed, for many years some JBL spearguns did not float because there were no plugs in the gun and the barrel free flooded. Some of these models were tube guns used for scubadiving and where the spearfisherman if he shot a fish did not want to chase his gun to the surface when he let go of it. The other reason is with multi-band guns (usually three bands) the flooded barrel served as ballast for less recoil with the shot. Here is another tube gun that free floods, there are even small port holes in the handle, muzzle and butt pad to make sure that water can freely pass into the gun and drain out when you leave the water. Now you know!

Top photo is auction photo, other photos are after restoration, the gun being a Sea Hornet clone and a mystery as this is the only one even seen. A triple band gun and a configuration never manufactured by Sea Hornet with a totally different lower grip shape, the gun was clearly made for spearfishing on scuba.

 

[cdavis]

John, when you test the ping pong ball, take a styrofoam cup down with you. What you end up with is a hoot.

 

[japppo]

You're right, I assumed the barrel was sealed. Assumption is the mother of all fuck ups. Thanks for the lesson @popgun pete

 

[John Marr]

Soooo.
After some real world testing using various materials; mostly shoe soles, packaging materials and wood, I can conclude that cdavis' suggestion is the best working one.
I used the quite light but rigid wood from an old clothes hanger I found and this one worked best in all depths.
Als wood is so easy to work with.

 

[popgun pete]

There are now buoyancy collars that can be fitted to tube guns, but they need to be the right diameter for your barrel tube.

Barrel Float

These MAKO Barrel Floats are very rugged yet they are easy to install. Simply slide onto your barrel and tighten the set screw

makospearguns.com

There are a few brands around, I recall an “Octosub” version, but cannot remember where I saw it about a year ago.

 

[popgun pete]

This is the Octosub that I was thinking of, there is another of a similar name based in the UK, but they may not be connected. The company makes speargun add-ons as well as other items like band elevators, a must with cord wishbones to prevent barrel skating by the band ends.

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