Better RC Sailboat Rig Tension Meter

RC sailboat rigging tension meter. Derived from a The EC 12 Manual. Tension meter can be used on any RC sailboat. Base is 3mm slab with elliptical openings to reduce overall weight. Raised circular areas on base plate are used connect and restrain the arm. Additional raised areas are used for tension posts and spring attachment and for the bail for the brass arm. All 3D printed parts are millimeter dimensions

Brass arm is 1.19mm (3/64") Dubro #8161 Brass Rod. 

Bail for brass arm and brass arm retention pin is 0.81m (0.32") Dubro #8160 Brass Rod. 

Spring is from a ball point pen mechanism that retracts and extends the ink tube.

SS cap head 2mm x 6mm screws are used for tension post bushing, left end of the spring retention and the arm stop bushing. SS cap head 2mm x 10mm screw is used on tension meter arm.

Ruthex 2mm x 4mm threaded inserts are used for tension posts, arm stop, and the spring attachment to the base. The screw in the arm that secures the right end of the spring is simply threaded into a close tolerance hole in the arm.

An index card is taped onto meter base for recording calibration markings. The thickness of an index card is also used to ensure the arm rests just above the base.

An accurate kitchen scale with 8 pound range is required for calibration. Eight one-pound weights are required as well a ¾ pound weight is needed for initial arm position calibration. 

Test Rig & Meter Calibration

A ~4' length of rigging or wire is required to make a test rig.  Ideally this line/wire will be identical to the rigging line on the RC sailboat that you want to set to a specific tension using this meter.

Tie a loop in one end of the ~4' test rig wire /line. Secure the loop to the ceiling or an elevated hanger. On the lower end of the test rig line/wire secure a plastic container with that can hold up to eight pounds of weight. I used a plastic container with a screw on lid that previously contained peanuts. For weights I used BBs. I drilled hole in the container lid, fed the lower end of the test rig line thru this hole, and tied a button on the end. With this arrangement I can readily attach and remove the container to the test rig line/wire to change the weight.

Calibrate the arm position such that the arm just comes off the stop when a ¾ of pound weight is in the plastic container. The initial arm position can be moved left or right by adjusting the screw that secures the right end of the spring. When there is  ¾ pound of weight in the container the arm should be just moved off of its rest stop. After this initial calibration of the arm position remove the ¾ of pound weight from the container. Then add a 1 pound of weight into the container and mark the position of the left top of the arm on the index card.

Repeat this process with 2, 3, 4, 5, 6, 7, & 8 pounds of weight in the container to increase the tension on the test rig wire/line. The photos are of a new meter that has not yet been marked during calibration.

Set the desired tension on your sailboat rig and go sailing.