Cessna 170 (Guillow's kit #302)

[David Lewis]

As an experiment I built two Cessna 170's. The first kit I drilled lightening holes and omitted half the wing ribs. Gross take off weight came out to 31.9 g.

The second airplane I re-cut all the parts from contest balsa. Gross weight is 13.8 g. The prop, spinner and wheels are carved balsa. Markings are brush painted enamel. Rivet and panel lines were drawn with a felt tip pen. Both airplanes have working brass-bushed balsa tailwheels, and are covered with 2 um thick aluminized mylar.

Future changes are stronger landing gear and wing attachment, better airfoil, enlarge the plans to 1:15 scale and improve scale fidelity.

[Bill Gaylord]

Your experiment has very purposeful results. I came to the same conclusion that simply using lighter balsa will reduce weight far more than lightening, unless of course one blows holes through their model to the point where it looks like it was shot multiple times with a 12 gauge. This is especially true with heavy wood like we commonly see in older die-cut kits. It's easy to find wood closer to contest weight that weighs 50% or less than the heavier wood. Lightening parts 50% requires extensive surgery. I recently built a new sheeted wing for an rc Guillows P51 using contest grade formers, 1/32" sheeting, and lightweight iron-on covering. I believe it's as light as any of the previous non-sheeted wings I built for kits in the series, using stock wood.

[David Lewis]

Good point. Light balsa is a powerful weight saver because strength-to-weight ratio goes up as density goes down.