Thursday, December 15, 2016

1080-00-108-1173 Camouflage Screen Support System Masts

Those of your who have read my former web site and blog posts may recognize the following paragraph:

The Cape Cod Packet Group had good information on these masts, guying information, and deployment. They use one 1080 mast set for a G5RV in an inverted V configuration. There was also a link on the site to another guy ring design. If deploying a G5RV in this manner 2, 10 ft. or longer crappie poles can be installed at the ends to keep the ends out of reach or ropes may be affixed to the ends and stretched out to anchors to keep the ends safely out or reach. Anyone know what happened to the CCPG or their site?

The CCPG still has a site, but the mast information is not there.
I was searching on the NSN and found the original web page HERE!
I hope the link works. This page shows the G5RV configuration I have been using with the

1080-00-108-1173 Camouflage Screen Support System Masts and my AB155-A/U mast using the tripod adapter.

Finally, if you want to compute the minimum guy length use the Pythagorean theorem: one side of the right triangle formed by the mast and the other is the ground. Determine how high you will make your mast. This is side a of the triangle. Then measure the distance from the mast base to the guy anchor. This is the other leg of the right triangle, side b. The guy is the hypotenuse, c. The advent of calculators made this really simple. Remember doing square roots long hand or with a slide rule? The theorem states side a squared plus side b squared equals side c squared, but we are interested in the length of c -- not the square.  This requires taking the square root of the sum of the squares of a and b.

Now you know the height of your mast and you know where you want the base and how far away you will place the guy anchor from the base. All anchors will be equally spaced from the base.

For example, 50 ft to the top of the mast, 35 ft from the base to the anchor. This will be the length of the top set of guy ropes.

Square each distance: 50 squared is 2500. 35 squared is 1255.

Add the two squares (2500 + 1255) = 3725. This is the square of the hypotenuse.

The guy is the hypotenuse of the right triangle. To get the answer for the length, take the square root of the sum of the squares which equals 61.033 feet.

Now add how much extra you will need to fasten the rope to the mast and to the anchor.

I use spring clips at the mast ends of the guys fastened with a bowline knot. For this I allow one foot. At the anchor end I use a Taunt-line hitch or other sliding knot that will bind and not slip under tension. (see my post from 9 December 2016, Military Masts, Part 2)  I allow anywhere from 3 to 5 feet extra at this end. My total length would be 65 to 67 feet. Many times I use more depending on how many guy lines I get from a spool of rope.

Do this for each set of guys.  For example for a 44.5 foot mast using 12 sections (44.5 inches long each) of the  1080-00-108-1173 masts the bottom guys would be 4 sections high or 14.83 feet, the middle ones 8 sections high or 29.33 feet, and the top would be 12 sections high or 44.5 feet.  It is much easier thinking 4 foot per section than the odd feet and inches so I use 16 feet, 32 feet, and 48 feet.

Each section is 44.5 inches to 44.625 inches long when assembled.  The multiples are repeating decimals that never end.  Rounding to 2 places is good enough.  Using 48 inches or 4 feet as the length of each section of calculations makes calculating the lengths much easier.

If you doubt your math, lay out a mast on the ground, measure (or mark) heights and the base to anchor distance, and use a 100 meter/330 foot tape from Harbor Freight to measure the distance from where you want to place your guys on the mast to the anchor point.

This could even be done on an empty parking (if you have permission to use the lot) lot using chalk, but you need to be certain that the distance from the top to the bottom of your chalk line mast is straight and the distance from your chalk line mast base to the anchor point is a square angle (90 degree angle).  Do one side of the mast.  Then you know how much rope you need for one set.  Multiply the total of this set by how many guys you want to make.

1 comment:

  1. The link to the CCPG mast page works. The top of the mast shows an arm that extends out from the mast to support the center of an inverted-v G5RV.
    I have used this configuration several times and it works great. I made the top arm from an extra section of mast that I cut at an angle to make a 90 degree elbow, welded the joint, added a pulley at the end, installed a rope, and gave it a try. The arm does not rotate if both ends of the antenna wire are secured. After the first time I used this I decided to drill a through hole in the top arm section to install a bolt and prevent any rotation of the arm.