Radio Control: Pylon Racing

Radio Control: Pylon Racing

Bill Hager

Season and Championship

For most of you, the racing season is about over. For some, however, there is one last and very important race. Every year, about the end of October, the National Miniature Pylon Racing Association (NMPRA) holds its annual Championship Race. This is usually the most competitive race of the year, as only the top fliers in the country are invited.

Qualification and Points

The NMPRA has divided the country into districts, somewhat like the AMA has done. Each district has a district vice president whose job is to coordinate racing activity in his area and to keep track of the top fliers.

We have a point system that awards points to a flier according to how he or she finishes in each race. At the end of the season, a flier uses the best six race finishes to come up with a total for the season. The top 20% from each district qualify for the Championship Race. Also, the top 10 finishers at the AMA Nationals, NMPRA officers, and past Championship winners are automatically qualified.

Race Location

The race location is rotated among California, Texas, and Florida each year. This year the race will be held at the Titusville–Cocoa Airport in Titusville, FL. It will be hosted by the Moonport Modelers.

Next month we will have a full report on this race.

Call for Tips

I have, in the past, asked for those of you who have any helpful hints or ideas to send them in, and I will pass them on to the readers. The response to this plea has not been too great. Come on, guys! I know you can do better than that.

John Jennings, a good friend of mine and an accomplished pylon flier, has put together some very good tips on trimming a pylon racer. Here we go:

"The fact of the matter is that there is a whole lot about trimming pylon racers that most racers ignore, or simply seem not to have the time for. Pattern fliers, for years, have been using some techniques that apply directly to pylon racing, as the laws of physics don't usually change from one event to another."

"Seventy-five percent of the trimming problem can be corrected by simply building straight and true airplanes. But what does a person do when his dream airplane is test flown and goes barf, barf?"

"The following steps should be undertaken immediately:"

Trimming a Pylon Racer

1. Check the CG and rebalance exactly according to the plans. If the plans say 2.75 in from the leading edge, it doesn't mean 2.9 in.

1. Check the lateral balance (i.e., wings). A simple way to do this is to grab the spinner (preferably not while the motor is running) and have someone put a finger under the tail skid, then watch to see which wing drops. When starting the trimming process, the wings should initially be balanced. Any unbalance can be corrected by driving a nail into the wingtip of the lighter wing.

1. Check the rudder for warps. If you can't remove any, just take note of them.

1. Check the wing for warps by holding it up to a light and sighting directly through the dihedral joint from the rear with one eye. Now avert your vision and look at each wingtip; compare the bottom of both tips for warps and take note of any.

1. Check the distance between the tailpost and each wingtip. Triangulate, and correct discrepancies by shifting the wing in the saddle if possible. Take note of any discrepancies.

1. Check for aileron differential. Note the difference between the left and right throws, but measure—with calipers—the up-throw of the left aileron and the down-throw of the right aileron for a full-deflection left turn (repeat for a full-deflection right turn as well). The difference between the full-deflection measurements should be less than 10 percent. Most Formula use 3/16 in (0.186 in) of max deflection. Ten percent = 0.0186 in, or about 1/64 in — not much difference. If this is not adhered to, the airplane will not roll axially into or out of a bank, and this can give the appearance of a "tuck" or "climb-up" in a turn.

Causes of differential can be:

• aileron control horns raked forward or backward;
• a difference between the fore-aft positions of the aileron control horns; or
• ailerons setting neutral on wing surfaces while the servo arm is not in the standard neutral position.

If all of this is done and no substantial warps are present, most airplanes will fly straight. If bad tendencies—like a tuck-down in a left steep pylon turn—exist, you may correct them by:

• adding right wingtip weight;
• adding right rudder trim; or
• shifting the wing in the saddle so that it is aimed to the right.

Any combination of the above will correct the tuck and will usually require a slight amount of left aileron trim. As a last resort, one can add right thrust. If no warps are present and the airplane still persists, recheck the CG and shift it slightly rearward, 1/8 in (0.125 in) at a time. (Note: Polecats require a certain amount of right wingtip weight to be correct.) The above rules also apply when the airplane climbs up out of a pylon turn—just reverse the directions of the appropriate correction.

"As most tucks can be corrected with right rudder trim, then why use alternatives?" The answer is that too much right rudder can cause yawing down the straightaway and slow you down, along with some funny tendencies upon coming out of turns. Weighting the wingtips works well because, as the turn radius decreases, the centripetal force on the weighted wing increases, causing an even greater effective force to correct the tuck. This same technique can be used for any type of pylon racer.

Let's hear some of your tips and ideas. See you next month.

Bill Hager 4622 Bridgeport Garland, TX 75043.

Transcribed from original scans by AI. Minor OCR errors may remain.