HOW TO USE A SLING SHOT OR BOW AND ARROW TO INSTALL H.F. RADIO ANTENNAS
IT IS ALL ABOUT WEIGHT
THE COMMON SLING SHOT
The key factor in launching antenna support lines is the weight of the projectile. At first this may sound a little odd, but after many years of installing antennas using "natural support structures" I have discovered the real controlling factor is weight. This is best illustrated by a review of the sling shot method of antenna construction. Typically the sling shot is used to launch a lead weight, 1 to 3 ounces. Here is how it breaks down by weight. A 1 oz. lead weight will travel well, altitudes of 50 or 60 feet are realistic, depending on the power of the sling shot and operator skills. A 1 oz. weight will NOT fall cleanly to the ground passing through a tree. If the shooter goes all the way over the tree it can work. Any interference with limbs, leaves, sap, and it will not work. The 1 oz. is simply not enough weight to do the job. No problem - MORE WEIGHT !! Here is where the problem starts, a typical sling shot has limited range. When the weight goes up the range goes down. At 2 oz. the range drops to about 40 or 50 feet. This assumes the line is light weight (5 to 7 pound test) and releases freely for the entire trip through the tree. The free fall is a lot more reliable and a line can usually be shot through a tree. Even so - forget pine trees, cottonwood, and some others. Every small branch the line passes over will induce some drag and that can add up to enough to make a second and third shot necessary or even kill the project entirely. Another problem is the weight whipping around a small branch on the pull back, with the obvious result of a hopelessly snagged line. At 3 oz. you are done, the range is so short a big rock or brick thrown up will do a better job. In my antenna trick bag I keep a "bean bag" just for that purpose. It has a brass rivet to tie a cord through and is very handy for getting over low limbs AND to pull a cord back up to the top of a tree to facilitate lowering it close to the trunk for a cleaner installation. The sling shot is cute and has some limited applications but know the limitations. The commercially available one I have seen sells for $100 last time I looked. It is not rocket science and a home built one will work just as well. Most well stocked ham junk piles will have at least some of the components which can reduce the cost. A cash outlay of $0.00 is possible with a large enough junk collection. I still have the one I put together over 35 years ago.
THE BOW AND ARROW
Currently I use a compound bow and custom modified arrows. Over the years I have tried a crossbow and a recurve bow. I do not recommend the crossbow. The big problem is mounting the line reel. The crossbow itself will work but the handling of the line gets to be a problem as far as I am concerned. I have had some reports over the years of the arrow leaving the bow WITHOUT the line behind it for a number of reasons. I started with a light duty recurve bow and a tape-on bow fishing reel. Enter the weight problem. Arrows simply do not weigh enough believe it or not. At first I used fiberglass bow fishing arrows dipped in bright thick paint. They worked reasonably well and were easy to find in wooded areas. The tail of the arrow was already drilled for a line. I use no arrow rest, just allowing the arrow to rest in the notch in the bow, this prevents the line from getting snagged. For my money about 10 to 15 pound line is about right for this application. Care is necessary to see that the line is free to travel when the bow is released. If the line snags on anything on release either the arrow will end up in the next county sticking in the top of a new convertible or on a unexpected and immediate return trip to the shooter more or less along the line of travel. These outcomes are way not good. Recently I decided to option for MORE POWER and started using a light duty compound bow. This presents a new set of problems and requires more attention to the old problems. Once again it comes back to weight. Even with a heavy arrow the compound bow has to much power. The problem is easily fixed by adding more weight to the arrow. More weight is better, the heavier the projectile (in this case the arrow) the more reliable the fall. After years (literally) of trial and error I finally discovered composite arrows. They are ideal. They will not bend (arrows can get side ways and whack limbs) or break easily. They are hollow AND have a removable nock (tail shaft). They have a threaded end for a variety of points. To build up a arrow I remove the plastic nock and plug it with hot glue (more on this later). To minimize danger and damage I mount a rubber bumper (equipment rubber foot) to the tip with a brass 6-32 screw and lock washer. I fill the arrow with at least 30 grams of #8 shot (as in shotgun shell shot), more can be used, I consider 30 grams the minimum (that is about 1 oz. of just shot). The tail piece (nock) is then pressed into the arrow and aligned. A hole is then drilled through the arrow just behind the fletching and THROUGH THE GLUE PLUG IN THE NOCK. This allows attachment of the line and prevents the loss of shot through the hole. Keep in mind this arrow is designed to be shot UP not on a horizontal plane. The final weight of the arrow and shot will work out to be about 40-45 grams minimum. For the final touch I spiral wrap the arrow in bright automotive pin stripe, this makes the arrow much easier to find in grass and weeds. A short piece of heat shrink at each end to secure the pin stripe completes the construction. With the removable tail piece the weight can be adjusted by adding or removing shot. I have tried a number of different devices to control and retrieve the line. The best so far the the bow fishing rod. It consists of a short casting rod that screws into a threaded mount on the bow designed for a vibration damper. This assembly also had a mounting for a spinner reel. I prefer the open faced reels (WalMart $12) because they hold a lot of line and can spool it off at about 500 miles an hour with no snags. Once in arrow is through or over the tree the bail is flipped over on the spinner reel and pulling the line back is easy. Usually (on a good shot) I simply cut the line at the arrow and pull back heavier cord with the line (typically about 20 pound mono-filament). The short "casting rod" if very handy to reel in "the big one" by swinging the rod and reeling in the slack on the return swing. The compound bow and composite arrow has enough power to use even heavier line but anything over 20 pound is difficult to handle. Heavy line tends to coil off the open face reel and tangle. The short casting rod attachment costs about $15 or so. They are hard to find and only available at large sporting equipment retailers, but well worth the time and cost. The rod assembly solves all problems with the line getting snagged on release and permits the line to spool off very fast along the path of the arrow.
In the picture column to the right I arranged the pictures in the general order of development over the years. Each picture will open in a new window and in full size with much more detail.
Here are some links that I found interesting. I don't necessarily recommend these methods but thought readers might find some useful information on these sites.
http://www.radioworks.com/ninstallant.html
RADIOWORKS is a very well written and maintained site, fun reading. I like his grass roots approach and agree with what he has on this above page almost 100%.
http://www.qsl.net/k5lxp/projects/Launcher/Launcher.html
K5LXP built an interesting device, looks a little complicated to me. I will stick with the bow and arrow myself.
http://www.arsqrp.com/ars/pages/back_issues/2002_text/0302_text/launching.html
This is short and fun to read, very funny. Contains a few pictures and some good tips on getting a line up, mixed with a little humor.
http://www.antennex.com/hws/ws0502/seall.htm
Shows how he constructed a sling shot launcher. He suggested a 1/2 oz weight which I have found is waaaaay to small. An interesting page in any case, short and easy to read.
