Flying Models Centerfold Plan - September 2010
No-Cal Polen Special
It’s a plane that deserves to be modeled and here it is in
a F/F No-Cal version, drawn from Jim Newman’s 3-view.
By Dave Linstrum/Photos by the author
As detailed in Jim Newman’s July 1999 "A View from Here," the Polen is a racy-looking homebuilt that reminds Jim (and me) of a P51 Mustang. As created by Dennis Polen, it is an excellent subject for the Flying Aces Club No-Cal Profile Scale event. It has a long body for a long rubber motor, essential for endurance.
While this No-Cal version is not eligible for the FAC Mass Launch Events (it must earn 40 scale points to comply) it will be a worthy entry in the regular No-Cal event at outdoor contests. Built light with a rolled motor tube and large balsa prop, it can compete indoors as well. For more info on the full-size aircraft, see Jim’s article and three-view. Using a Walt Mooney technique, I enlarged the three-view to the 16-inch allowable span using a zoom lens copier, then pasted up parts to suit a centerfold.
Note that the plan that appears with this article is not full size even though it may seem to be so in the centerfold. You could build off this plan, but it is easy when making a copy to enlarge it so the span is exactly 16 inches. Measure the span as published and use a calculator to compute the enlargement. I had to reduce the 11x17 building plan to suit the slightly narrower FM centerfold. If you enlarge onto an 11x17 sheet of paper, you will have a duplicate of the original plan. Make two copies, one to build on, the other for patterns such as ribs and tips. You will also want to copy the three-view for FAC judging. Rules require that the No-Cal be a recognizable version of the full-size aircraft. I slightly enlarged the tail and added a bit to the body length (and of course more dihedral) for F/F stability, but I think you will agree it does look like the full scale bird.
I moved to Provo, Utah from South Florida in 1997. Among the locals, there is lots of interest in ancestry. Let me assure you that this Polen has a worthy family tree. It joins a long line of No-Cals that I’ve been designing since 1990. All were published in AMA’s Model Aviation. Now I present the latest in this long noble line of No-Cal designs— the Polen Special.
If you have no experience with stick and tissue, rubber freeflight models, you will need to get some before building this Polen. This article is not an instruction booklet like you might get with a kit. I won’t tell you how to glue Part A to Part B, but will highlight some of the unusual methods and materials. I suggest you build some of the simple models from the Peck line first, such as the Peck ROG, the One Nite 16 and the Prairie Bird. You can get the 2000 Peck Polymers mail order catalog for $4 from: Peck Polymers, Box 710399FM, Santee, CA 92072-0399; phone 619-448-1818. You can order materials for the Polen as well as the kits. Also get a Peck 5:1 rubber winder. I suggest Peck for one-stop shopping.
There are some materials that you can obtain locally at office supply or artist materials stores. For control outlines (inked directly on colored tissue) get a Micron Pigma #5 pen. This is waterproof and makes a smooth line. Other technical pens, even an Ultra-fine Sharpie, will do. For the gold and white pin stripe (ruled on a piece of copy paper, then cut out and applied) you will need a Sanford 476815 Slim Tip Gold Coat Metallic Marker, also waterproof. You may also want to get a self-healing cutting board and some FoamCor for a building board. Scraps of this stuff can often be obtained from an artists frame shop. They also may have scraps of dark artists mat board, which works well as a disposable cutting board.
A craftsman is only as good as his tools. You will need some special balsa-working tools including: an X-Acto knife with #11 blade, a single edge razor blade, plastic bead-head dressmaker pins, glue applicator (Build with Duco cement or Tite Bond. While CyA glues may be much quicker, I still prefer the more traditional adhesives because of their more suitable qualities.) Also have on hand small artist’s sable brush, and a small needlenose pliers to form the wire shaft and rear hook. Wax paper covers the plans.
I suggest you build in an uncluttered, well-lighted work area. Keep your tools in an easy to find array and sit in a comfortable chair or stool. I like to build while listening to soothing music with phone unplugged. I enjoy New Age Jazz piano music, as played by Jim Brickman or Elise West, a Salt Lake City artist.
It is not necessary to strip all wood for the Polen—ordinary 1/16-inch square and 1/16-inch sheet will do. You will have to strip the 3/16-inch wide motor stick from 1/8--inch sheet and a 3/16x1/16-inch for the “L” section that makes the stick stiff. Make a rib slicing template from 1/32-inch birch ply. Cut a blank from 1/16-inch C grain balsa at least 2 inches high and as wide as the template. Tape this to the cutting board on the bottom only.
Using the X-Acto, cut along the curve of the template and discard the first piece. Then move the template down 1/16-inch and cut again: you will have a rib. Make ten of them. Trim a bit from the front of the ribs as you install toward the tip, then trim to fit at the trailing edge. Note there is no tip rib, just the flat tip from sheet. This gives a nice thin flat airfoil at the tip where you want it. Note the stab and fin (built separately from the body so the stab can be fitted) are simple flat plates.
With one wing half pinned down, tip up the other so you have a 3-inch “V” dihedral under that tip. Glue the joint well and add the two root ribs, slightly tilted. Let dry before removing from the board. You will cover the wing in two halves, joining the tissue at the ribs.
The front Peck nylon bearing is mounted on a 1/32x1/8-inch aluminum standoff (smash a piece of aluminum tubing flat if need be) that allows minor thrust adjustments. Bind with thread and glue (Duco) the bearing to the U-shape aluminum and then the other side to the motor stick. Bind and glue the rear hook, which is bent from a Peck 1/32-inch prop shaft. The stick assembly is glued to the right side of the body frame after covering the left side. Note that only one side of the body and the top of the surfaces are covered—the FAC rules allow this. The rules also allow building with gear up—a good thing as there are no Robart retracts small enough for this Polen!
Use orange Esaki Japanese tissue from Peck: the model is all orange except for its markings. Water shrink the tissue on a frame, then remove and iron. This will help avoid warps. Cut the tissue for all parts about a half inch larger all around. Tape lightly to the plans so you can rule the control outlines (a broken line symbol on the drawing) and add the prefab pinstripe to the body. Use a glue stick for this. You may adhere the covering to the parts with a glue stick (apply using a toothpick or a brush dipped in rubbing alcohol) or with Elmer’s white glue thinned with water. The latter requires that you keep the part flat on the board while it dries.
Add a piece of black tissue or black paper for cockpit canopy (black paper can be made by leaving the cover up on a copy machine, but do not let the operator catch you—they think it uses too much toner). Using a very fine brush and white acrylic, letter the words "EXPERIMENTAL" under the canopy and "Polen Special" in script on the fin. Note the fin is covered before the stab is fitted into its slot in the body.
Glue the leading edge of the stab to the body, leaving the trailing edge loose until the model is trimmed. You may use shims under the trailing edge to trim. Check to see that it is aligned from top and rear (sight along body). Then add the fin. Glue the motor stick to the body at each upright. Glue the wing to the cutout in the bottom of the body, again aligning carefully. Finally, add the prop shaft, with a brass washer, then the silver Peck prop—either a 6-inch or 7-inch for windy flying. The latter size can cause torque problems so be careful. Bend and clip off the shaft at the hub notch. Your Polen is now finished!
Low wing models do best if trimmed to climb left in a loose spiral. Warp in about 1/16 right rudder (yes—right for cross trim) and add a balsa or cardstock trim tab about 1/4 x 2 inches to the trailing edge of the left wing midway out. Bend the tab about 1/16-inch plus down. You may also need a bit of left and downthrust: bend the aluminum hanger. Check that the balance point is as shown on the plans—add bits of solder to the nose or the tail to correct. Trimming can also be done with the stab trailing edge. Do not do any "test glides." Trim the model under power only. The glide is not very good anyway.
Make up a 14-inch loop of 1/8-inch FAI Tan II rubber: tie the knot well. Lube it and attach it to the prop hook. Have a friend hold the prop hub while you stretch wind from the rear: using 5:1 winder, put in 100 turns. You can work up to max winds and longer loops later. If you fly in the wind, you may need 3/16-inch rubber. Launch into the wind with the nose slightly up—do not throw! The model should spiral up to the left. Make trim adjustments with the wing tab and/or prop hanger. Stab trim can also be used. Then glue the trailing edge. Do not expect much of a glide: that prop and loose motor add a lot of drag. Endurance comes from a nice long steady climb. I hope you enjoy this simple freeflight version of the Polen Special. Send a photo of your model to the editor for use in our Barnstormers feature. Good luck!
This article originally appeared in the March 2001 issue of Flying Models.