Carving wingtips made easy: 14 simple steps to shape up

HOW TO

I really enjoy building airplanes from kits. To be able to create a flying model from a box of balsa sticks, sheets and blocks gives me a lot of satisfaction. Part of that enjoyment comes from carving those balsa blocks to a required size and shape.

A lot of kits use a rectangular block of balsa for the wingtips that you must carve and sand to its final shape. Carving a wingtip is easy and, to me, a lot of fun. You only need a few basic tools to produce expert results.

For this article, I used a Dynaflite Chipmunk, which has a relatively simple wingtip shape, but this technique can be used to produce just about any shape of wingtip that you want. Here's how I do it.

Before you start, assemble the tools and materials you'll need: a manila folder (to draw the wingtip pattern on), a French curve, aliphatic-resin and thick CA to glue the balsa block to the wing, a flexible ruler, a razor plane, a sanding bar, sandpaper In a variety of grits and a ballpoint pen or a pencil.

1

I don't like to cut up my plan, so I use a French curve and carbon paper to trace the wingtip shape onto a manila folder, and then I cut the pattern out. You could alternatively use a copier to make a copy of the wingtip. After you've cut out the pattern, check It against the plan for accuracy.

2

Pin the pattern onto the tip block and draw the tip's outline on the block with your pen or pencil. Don't use a felt-tip pen; the Ink tends to bleed.

3

Use a jigsaw or a band saw to cut the block just outside of the line; you want to leave a little wood so you'll be able to sand the block to the proper shape later. If you don't have a Jigsaw or a bandsaw, use a razor saw, but take your time and remove only small pieces at a time.

4

Using the pattern as a guide, sand to the line to smooth the wingtip. Be sure to sand it so that the outline Is flat. Now pin the tip block to the wing so that It completely covers the tip rib.

5

Using the tip rib as a guide, trace the airfoil onto the block's Inside face.

6

Be sure to draw the entire airfoil. If you make a mistake, lightly sand the block to remove the outline and draw it again.

7 Cut just to the outside of the airfoil shape line. When you've finshed cutting, your block should have both the plan view and the airfoil cut Into It.

8

Glue the block to the tip rib and use pins to securely hold It while the glue sets. I use thick CA in the center of the block and aliphatIc resin on the block's outer edge. When you pin the block to the wing, the excess glue will ooze out, and If you use CA around the edges, It will harden the balsa and make it very difficult to sand. The aliphatic resin Is a lot easier to sand, and you'll end up with a smoother job. Allow the glue to cure thoroughly before you proceed to the next step.

9

Before you start to shape the block, trim It so that It conforms to the wings taper (thickness) and airfoil shape. Use a razor plane and sanding bar to remove wood from the top and bottom of the block, and sand It smooth. Use the wing as a guide and work slowly, removing only a little wood at a time. Check your progress often. Don't sand the wing; sand only the block, or you'll risk altering the airfoil's shape. The tip block should be flush with the tip rib and should continue the wings taper.

10

To keep the block symmetrical while you shape It, draw reference lines to guide you. Determine the midpoints along the thickness of the block in several places, and mark these points. Using a flexible ruler, join the marks you made and draw a centerline from front to rear. ill

Use your tip pattern to draw reference lines on the top and bottom of the tip. You'll use these lines as guides when you carve the tip.

12 Use a razor plane (Master Airscrew's razor plane works very well) to shave the balsa off the comers of the tip. If you don't have a razor plane, use a sharp razor blade or hobby knife. Work slowly, and shave off only a little at a time, being careful not to gouge the wood. Continue to shave off wood to achieve the general shape of the tip. Don't remove too much wood at one time; you can always go back and remove more if necessary.

13

Start with 100-grit sandpaper and sand away the ridges left by the razor plane. Continually "eyeball" the tip for symmetry as you sand. Once you have shaped the tip to size, sand It with progressively finer grits of sandpaper until it is smooth as silk.

14

The finished tip! It has smooth lines that blend gracefully into the end rib. Rest assured, when your flying buddies see your finished wingtips, they'll think you spent many hours carving and sanding. Don't tell them that it took only a little effort and forethought to produce these excellent results.

Dynaflite; distributed by Great Planes Model Distributors (760) 744-9605.

Master Airscrew; distributed by Windsor Propeller Co. (916) 631-8385; masterairscrew.com.

Copyright Air Age Publishing Nov 2002
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