Arrow Tracks

ARROW TRACKS

While most mass produced commercial spearguns are made with open or no arrow track for ease of manufacture, the higher-end hobbyist and custom gun builders have been offering various partial length or full length arrow track enclosures. The reason for enclosing the arrow track has been well demonstrated by tank testing similar guns with and without enclosed tracks using equivalent band power. Though I was not a party to the experimental testing, I have spoken to those that were. The testers described both a sine wave trajectory in shaft flight (visible on super slow motion videography) and a corresponding decrease in measured impact on the target with the shaft fired from an open arrow track. These findings were not present with the enclosed arrow tracks.

The methods that other builders currently employ to enclose the arrow track include:

1. Adding delrin plastic partial enclosures to the open 1/2 track of wood guns using multiple small wood screws. This method is a quite reasonable and functional way of enclosing an already made open arrow track gun, but is labor intensive and employs multiple wood screws which I prefer to avoid in my guns due to their propensity for wood rot.

2. Milling an oversized round or square track in the gun stock to hold a large round or square delrin or Teflon insert and then repetitively pinning it over the length of the stock and milling the arrow track within the plastic. A much stronger and slicker arrow track is produced with this method, but the use of repetitive pins limits the plasticís ability to expand/contract with environmental temperature changes. Some builders have machined slots in the plastic for the pins to allow for these changes, but this adds to an already labor intensive process.

3. Milling the entire arrow track in wood or wood/epoxy graphite with or without a metal muzzle attachment to protect the arrow track roof. This is certainly the easiest technique, but wood or epoxy graphite tracks are susceptible to wear over time and more vulnerable to damage from minor abuse.

After experimenting with all of the above methods, I came up with what I feel is a more elegant solution; a trapezoidal plastic track. The procedure is as follows:

1. I first mill my stocks with a dovetail bit creating a trapezoidal shaped track.

2. I then insert a trapezoidal shaped plastic (UHMW polyethylene) blank cut to a snug slip fit in the trapezoidal track. I use UHMW rather than Delrin or Teflon because it is more durable than Teflon and less brittle than Delrin while having the lowest coefficient of friction measured against stainless steel in a saline environment. These are the same reasons it is used for joint replacements in orthopaedic surgery.

3. The arrow track is then milled into the UHMW blank.

4. The arrow track is then removed for the remainder of the gun stock woodworking.

5. After the gun stock is finished and sealed with multiple coats of thinned epoxy sealer, the arrow track is reinserted and pinned with a single machine screw just in front of the trigger mechanism. Because the trapezoidal shape captures the track vertically, the need for repetitive pinning over the length of the gun is eliminated; thereby allowing for environmental related expansion and contraction of the track without creating ripples in the track.

Trapezoidal Track

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