FF Sport and Scale
Fernando Ramos, 19361 Mesa Dr., Villa Park CA 92861; E-mail: [email protected]
THANKS TO those who have taken time to E-mail me. It is interesting to note what appeals to many modelers out there, such as the comments I made regarding the RAF 34 airfoil.
I received dozens of E-mail messages from modelers who wanted the ordinates for the airfoil, so I included them in this month's column.
I want to show you how to plot an airfoil, but it will have to wait until next time; I have been incredibly busy building a set of Cub wings for a friend who did the upholstery on my Bellanca Cruisair. We swapped work.
I have been restoring my 1949 Bellanca for several years. I took the fuselage down to the bare bones, sandblasted and powder-coated it, then replaced all the wood. I made a new instrument panel and completed the wiring; all systems work.
I covered the fuselage and applied the first coats of nitrate dope, then took it to be upholstered. The wings were microballooned (they are plywood-covered) so the surface would be as smooth as glass.
If you think removing tissue from a model to re-cover it is tough, try removing cotton that has been on for 40 years. Both wings are almost ready for covering.
Airfoils and the Bellanca
Giuseppe Bellanca was known as a genius at designing aircraft with incredible wings. My Cruisair is no exception; it has a very thick root with a semi-symmetrical-looking airfoil, then it changes to an undercambered section out toward the tip.
The Bellanca will cruise at approximately 140 mph. When I bring it in to land, I cut the power at the numbers and glide in, using flaps as necessary. I have never tried landing the Bellanca without flaps, because I would never be able to get it down. It has a 34-foot wingspan, almost making it a glider.
I worked on a 1931 WACO F-2, and it had a Clark Y airfoil. The Cub wings I am working on also have the Clark Y. When it comes to models, scale or otherwise, the Clark Y is hard to beat. Almost any french curve can give you a good representation.
Probably more important than the airfoil is the model's weight and good thermal activity!
For those who have the time, it would be great to find out how one airfoil compares to another — or several others — by building the same wing with different airfoils. Fly the model in no-wind conditions using the different wings, and keep track of the number of winds, etc. Each wing will have to be flown several times in order to get an average. Then compare numbers.
Wire-bending tips
I have several hints to share with you. The first is on wire-bending.
Many modelers shy away from this relatively easy task, but as with anything else, you might wonder what all the fuss was about once you learn how to do it.
Fulton Hungerford (of spoke-wire wheel fame) was a champ at bending wire. He gave me a box of many different kinds of universal joints, all made from wire.
Regardless of the diameter wire you bend, a simple rule applies: step back exactly the diameter of the wire. If the wire is 1/16 inch (0.063 inch), make a mark 1/16 inch back from where you want the bend. This rule is used only when the bend is 90° or less.
(I say it's a "rule"; actually, this is what I learned works. There are handbooks with tables showing how much step-back is necessary, etc., not only for wire, but for sheet metal. I learned the basis for this rule by doing, and I refer to it as a rule since it works each time. Could it be the Ramos Rule?)
Just place your pliers on the mark, which I apply with a fine-tip felt marker, and bend. After bending half the gear, I turn it over and use the same side of the drawing to bend the other half—there's less chance for errors. This can use pliers to bend wire as thick as 1/8 inch, but a wire-bending tool should be used on anything larger. Since most readers are probably rubber fliers, I will pass over using the bending tool.
Many landing gears on scale models have a trailing leg as part of the gear. This requires soldering the trailing leg to the main gear wire. Wire wrapping is generally used, followed by soldering.
If you go to an electronics-supply store, you can purchase copper wire in sizes from a few thousandths of an inch in thickness and up. Heavy copper wire is the last thing you need to use on a small model; therefore, having a variety of sizes is recommended.
Now you know there is no mystery to bending wire.
Making cowls and molds
Several years ago, I built a Sopwith Snipe at 1/2 inch = 1 foot scale. I made a pine-wood plug on a lathe in order to make a fiberglass cowl. After I had the proper shape, I sanded and varnished the cowl plug.
I went to a hardware store and bought a couple of heavy paper buckets that house-painters use. I cut the top half off a bucket and filled the bottom portion with plaster of Paris. I inserted the Vaseline-coated plug (to keep it from sticking to the plaster after it dries) into the bucket until it was just below the surface of the plaster. The plug was held there by weights until the plaster cured.
The easiest way to get the plug unstuck from the plaster is to drill a 1/4-inch hole in the bottom of the bucket, deep enough to reach the plug. Use a compressor to blow air into the hole, and the plug will pop out, leaving a nice mold.
The plaster mold is coated with Vaseline before it is laid in fiberglass cloth. I use bidirectional cloth (one that will lay flat on compound curves), and put in several layers using resin. Once this has cured, I use the same hole in the bucket to blow out the fiberglass cowl. Using fine cloth, a very light cowl can be made fairly easily.
Some time later, I decided to build a Sopwith Triplane in the same scale as the Snipe. When it was time for the cowl, I thought I could use the same mold I made for the Snipe—wrong! The cowl was a bit larger, and the shape was a bit different.
I didn't want to make a new plug if I didn't have to. Then an idea struck. I coated the Snipe plug with Bondo (material used for fixing small dents in cars) in a thick, even layer. I mounted the plug on the lathe and turned off the extra Bondo to the new shape. This worked fine, though it took a fair amount of time to sand and fair the new shape. After I had the correct shape, I sanded and varnished it again and proceeded as before.
Here is another trick for making small cowlings:
- Use a piece of polyethylene (heavy plastic) from a milk jug.
- Cut out the desired cowl shape, warm it with a heat gun, and form it over a plug.
- When cool, trim and use as a mold or the cowl itself. It is light, strong, and waterproof.
RAF 34
Finally, I want to comment about R.A.F. 34. In response to readers' requests from an earlier column, I am printing the ordinate table and figure for this airfoil (Fig. 2). I hope it will be of use in your scale projects.
Happy modeling,
Bob Hunt
Transcribed from original scans by AI. Minor OCR errors may remain.
