Peppermint Pattie (oz10598)

About this Plan

Peppermint Pattie. Radio control sport model, for .15 power.

Direct submission to Outerzone.

Quote: "This is a plane designed by Nick Damuck. It was kitted by Master Kits and published in RC Sportsman. The CAD plan was drawn by Gene Rock. I had been granted permission by both of them to submit this to you. It is a fantastic little plane, very groovy and aerobatic, and fast. I built one from a kit and can tell you an old .15 sport engine is just fine. Something like the old OS, or an Enya. I tried a ST .23 on it and it did not fly any better, so when I rebuilt it I mounted a .15 O.S. LA on it. The CAD file is something I had cooked up using one of my spare kits to copy the root and tip airfiols and create a wing plan in Compufoil. I never actually built a wing from this, so buyer beware. This plane and the Ace Super Pacer are my two most favorite planes, and I guess you could throw in the Sig Kougar. Dave"

This plan also appeared in RC Sportsman, March 1978.

Note photo of completed Peppermint Pattie model was found online at http://www.rcuniverse.com/forum/classic-rc-pattern-flying-379/5532053-peppermint-pattie.html

Update 02/01/2019: Added wing parts file (now in PDF format), thanks to JimPurcha.

Update 7/11/2022: Added article, thanks to theshadow.

Quote: "Peppermint Pattie. Or, How to Beat the Fuel Crunch and Keep Smiling by Walter E 'Nic' Damuck Jr.
There's gotta be a better way, I said to myself one evening while I was down my pattern bird, all the while wishing I could squeeze more than 10 or 12 flights out of a gallon of fuel. Besides, lugging an 8-pound airplane around is a real bother.

I began to mentally solve this dilemma. At first. I figured I'd buy one of the new 1/2A planes, but the lack of radio space discouraged me since I wanted 'full house' flying capability. I decided a .15 powered plane would be unique and give me a chance to design something that's 'just right' to practice with. After all, quarter midgets use three or four functions, and only a 4 ounce tank is necessary!

The design criteria evolved around a 300-square inch wing and a target weight of 2 to 2-1/2 pounds. For those of you with a sharp eye and a good memory, the Peppermint Pattie may look suspiciously like my Niris design in the October 1975 Model Aviation. Although many of the same concepts were used for both planes, this is not just a shrink job. For instance, the mid-wing configuration aids in performing superb axial rolls, and also provides a belly hatch so the aileron linkage can be put on the bottom of the wing, eliminating the need to provide clearance in the radio compartment.

The force and tail moment set-up, combined with a slightly longer than normal nose moment, is easy to trim with a non-critical CG, and provides excellent "grooving," even in this size plane. It will track just like its .60-powered cousins.

The relatively broad fuselage sides provide adequate area for true knife-edge flight. The fuselage itself is quite streamlined, and by eliminating the landing gear, additional improvements in drag reduction are possible.

A high aspect ratio of 6.3:1 and an aggressive taper ratio of 2:1 provide the best in roll stability and force distribtition. The airfoil is my own, being fully symmetrical, 14% root and 14-1/2% tip.

The leading edge uses my highly successful progressive curvature. That is, the root is pointed, gradually flaring to a well-rounded section at the tip. This ensures that the root will stall first, and at a higher speed than the tip.

The result has to be seen to be appreciated - Peppermint Pattie will gradually increase its sink rate as the speed is bled off, finally stalling ever so gently at about a 20 degree angle of attack. The ailerons are fully effective until stall because they extend to the tip, which remains flying until the very end.

The rudder has a 10 degree slope to eliminate the pitch down affect associated with rudder application on many other designs. The wing is placed slightly below the thrust line because it eliminates the hunting in pitch sometimes seen in true mid-wings.

While building the Pattie, I had my doubts as to whether or not a standard .15 would be enough power for pattern performance. Luckily, a friend of mine was able to lend me a potent engine. This was an unthrottled Fox .15 which would turn 17,000 rpm on an 8-4 power prop cut to 7 in, with 15% fuel and untimed crank pressure. I figured a little extra power is better than being underpowered.

It was a cold, clear day in February when I called some friends and drove out to the Wallingford, Connecticut field for Pattie's maiden flight. I arrived early and was alone with my thoughts and the Pattie. It was picturesque, with the bright sun on a crusty ground dusted with a bit of snow. My feet crunched on frozen grass as I brought the plane and field box from the car to the pit area. I was glad to have had a few moments to myself before my friends arrived, to calm my nerves. Will it fly? I asked myself, too nervous to think of the consequences. This and many more self-doubting questions plague every modeler with an untried bird. The wind died down, and I got the Pattie ready as my friends arrived. By the time the comments and jokes were all said, the wind was picking up a bit out of the north, so it's now or never.

Attach the battery, prime, flip, and the engine roared with a life of its own. Boy, did it scream! A cold sweat seemed to form on my brow. Briefly, I again checked all the controls. One of the guys lifted the plane from the cradle and looked at me for the go-ahead. Quickly wiping the oil from my hand onto my jeans, I picked up the transmitter, swallowed hard, and gave the go ahead for a hand launch.

For a split second after the launch, the plane appeared suspended - motionless. It then accelerated, dipped down and to the left. A quick twitch of the stick brought it level. With a stick at neutral, the dip and bank returned, skimming dangerously close to the ground. This time I hauled up and right, then held stick pressure while I jammed the trims over. Now it was flying level.

By the time I did this, the plane was ready for its first turn and was really moving out. With that engine the flight speed was unreal. All the controls were too sensitive, and with all that speed, I decided to fly large ovals until the gas ran out. After what seemed an eternity (on 4 ounces of fuel) the engine sputtered and died. After a long glide to bleed off the speed, I landed in the tall grass off the north end of the runway. Triumphant and relieved, I decided to pack up and get warm.

The post flight inspection revealed the need for the trim - a slight wing warp and shrunken plastic pushrods due to the cold. The engine was changed to a stock Fox .15 R/C, and the control throws reduced to give the same response feel as a larger ship. All maneuvers groove, and the plane is not twitchy like some small planes tend to be. The clean design is fast, and swinging an 8-4 Top Flite at 12,000 rpm is just right for pattern practice and general flying fun.

Once you're accustomed to it, hand launches are simple, just give the ship a firm toss: No need to run with it.

Since this plane was designed for pattern practice, it is not recommended for beginners. If you can fly a .40 or .60 aileron ship comfortably though, then try Peppermint Pattie. The construction notes are only a general guide, since you will probably have your own pet methods, anyway.

As with any plane, the selection of wood is important. With a small plane, this is even more so. Use a light grade of wood for everything except the fuselage sides, which should be medium.

Tail surfaces: As shown, these are built up from strip stock. Remember to sand the tapers as shown.

Fuselage: A straight fuselage is essential for good performance, and the Pattie has a sure-fire method of alignment. Prepare the two sides by gluing on the doublers, triangles, and stiffeners. Mark the thrust line and the bulkhead locations. Cut out and glue F-2, 3 and 4 to one side, noting that they are all the same width. Mark F-2 for a motor mount and install the blind nuts... "

Supplementary file notes

Article.
Wing parts.

CAD file

This plan is available for download in CAD format.

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