The Truth from Steve Alexander on enclosed track speargun

[Iyadiver]

Gentlemen & Ladies,

This is what I received from a good friend. The info was from Hawaiin SkinDiver Online but the website is out of action now.
Some of you might have read this but there should be plenty out there who is still in the blind.

ENJOY.....................


Do enclosed spear tracks improve
speargun accuracy? >> Jasmine


Jasmine > This is a common question that I often get asked. First let me saythat if you hunt where there are plenty of fish and you can get all you want, then an enclosed track gun is not going to help you. However, if you go home empty handed too many times because the few fish you saw were just out of range, then an enclosed track may improve your odds. I started building guns with enclosed tracks about 13 years ago simply as a means to hold the shaft in place while hunting. This was a necessity with my
over-and-under, dual-shaft guns, especially with the bottom shaft. Then, as more and more divers, following Terry Maas’ lead, started targeting the big Tuna, I saw a need for spearguns with more range to increase the number of opportunities to hit and land these fish. Like everyone else, I tried adding more power to my gun, but it became erratic as the shaft bowed when fired
and the recoil increased drastically. My solution was to increase the gun weight and enclose the spear track. This resulted in a gun that would shoot a 3/8" shaft powered by 6 bands, over 30ft. with consistent accuracy.

So how much of that improvement was attributed to the enclosed track? Not very much, I’m afraid. John Warren, a part-time gun builder in S. California has made several guns with up to 7 bands that have exceptional range and accuracy with only the slightest depression on the top of the gun for a track. These guns, however, are extremely heavy. I would have to say an enclosed track is beneficial under certain circumstances, that is, if the shaft is subject to very high band tension and the diver wants the gun to be reasonably light for handling purposes. On the other hand, an enclosed track is entirely a waste of time if the shaft is not being over-powered. So, at what power level does the shaft become unstable during acceleration? That depends on many variables, such as: tip weight and drag, shaft diameter, shaft length and hardness and how straight it is. Also as previously mentioned, gun weight, especially at the muzzle end, has an effect on recoil in the vertical direction, which can destabilize the shaft considerably. Underwater testing of your particular combination is the only simple way to tell for sure, but “generally” a 5/16" x 65" shaft in a close fitting, half round track, will handle about 300 pounds of rubber tension; and a 3/8 x 72"
shaft is OK up to about 420 pounds. Shorter shafts can take more power, longer ones less. Again you may get away with more power if the gun is very heavy.

There is another way to increase range without sacrificing accuracy; Increase the stiffness of the spearshaft by increasing the diameter. How about a gun with a half-inch diameter shaft and nine bands that shoots 45 feet? This may seem a little extreme, but you’re only limited by how much gun weight and size you’re willing to lug around and how many bands you’re
willing to cock! Remember, the more range you have the more opportunities you will have. SA



Delrin vs. wood track: improved speed, range & durability?

Unless you just “gotta have the look”, a Thermoplastic track such as Delrin or Teflon is not worth the money or effort. The popular misconception is that since Delrin and other plastics are commonly used as bearing materials, they would make a great speargun track because of their friction reducing properties. The fact is there is no friction reduction advantage because there is no appreciable friction to reduce. For the same reason, there will
be no wear on either the track or shaft. Unless a wood track is habitually fired with a track full of sand, it will last a diver’s lifetime and probably his son’s too. Tests have proven that the plastic track won’t buy one nickel’s worth of increased range, speed or track life. The downside to plastic is its high thermal expansion rate. Temperature changes affect the plastic track to a much higher degree than wood or aluminum. I discovered this the hard way when I built my first few plastictrack guns many years ago. You can’t solidly mount the track to the wood because when the ambient temperature changes, it causes the track to expand or contract enough to cause the whole gun to warp by as much as a quarter inch. Of course, this is not a problem if you hunt in water that is the same temperature as the air in your shop when you screwed the track down. The only alternative is to let the track “float” or slide independently in the gunstock by slotting the mounting screw holes for example. This works OK if the gun is over built with a sufficient amount of wood in the stock to make up for the stiffness lost to the sliding track. I would have to say that the only advantage a plastic track has over a wood one is the durability where the thin upper surface of the track is exposed to damage from wire wishbones or accidental impact. So if you really like using wire wishbones or are in the habit of tossing your gun in a barrel with everyone else’s when you go out on a boat, then a plastic enclosed track could be a real advantage. SA



REGARDS,
Iya

[Aquiles]

Wow great information, Thanks

DQBN

[Iyadiver]

UR MOST WELCOME..........

In fact Jay Riffe spoke of almost the same on the matter of enclosed track in a private email to my friend.

In summary :

" Enclosed track shows no obvious accuracy improvement with thicker 3/8 ( 9.5mm ) shafts. "


If two of the world best have spoken similiar I guess they know best.


IYA

[foxfish]

I have dug up this thread because I though it might interest some of our gun builders?
Some good points made but not much bearing on the type of guns most of us Europeans use.

[strangelove]

Great research foxfish, I am not sure if it is a perception that I have (I do own both enclosed track and open tracks, epoxy and oil finishes), when I fire the open track, I think the shaft does not slide as easy as the fire shots with enclosed (delrin enclose). I get the feeling that the open track shot is slower then the enclosed track - this perception is accentuated with epoxy-finished gun. I wonder if any one else has that impression.

[hteas]

A friend of mine had an Alexander open track Reef model that slowly deteriorated during a trip to Baja. By the end of the trip he had to hit the gun after pulling the trigger to make the shaft start moving. It was an oil finished teak gun, and definitely was slow. I don't know whether the track was too small or whether the wood was aging poorly and the grain stuck up, but I am sure he will never spend the extra for wood again.
Howard

[foxfish]

Just goes to show that you can read anything about anything on the forum & find many different opinions.
I can defiantly see the benefits of delrin enclosed tracks for small diameter spears like 6 - 7mm but as I have no experience of using such a gun I will have wait until I build one!

[strangelove]

One more thing about the enclosed track, at least for me, it does take longer to load. Since the open track one can just slide the shaft straigth to the trigger house, the enclosed track you have to thread the shaft from the muzzle.

[slingshaft]

Loading an enclosed track seems worth the extra time and effort for thinner high strength shafts. "Speed Kills"

[miles]

During our search for tuna gunz, we also looked at the enclosed track models from various manufacturers. One of the GREATEST dis-advantages was actually a simple thing. If your spear gets bent by a fish, you will not be able to use that spear in an enclosed track again!! With our current guns, we'd simply bend the spear back into shape and continue spearing.

Makes a big difference when you're travelling to exotic locations, as then you'd have to carry many spare spears with you!!