Force 5 (oz8943)
About this Plan
Force 5. Radio control sailplane. Standard Class Sailplane. Wing area 839 sq in.
Quote: "Frail birds and high winds don't mix too well. Here's a machine for those less than perfect days. Force 5, by Howie Applegate.
Force 5, described by the Beaufort Scale as a fresh breeze of 19-24 miles per hour, or 16-20 knots. Although some of us sailplaners don't feel too comfortable flying in Force 5 winds, this ship is designed to take it, and handle well to boot.
This aircraft is designed around a wing with an aspect ratio of 11.19, which is quite normal for machines of this size. The airfoil is a Goettengen 609 which is blended at the tips. The wing outer panels are washed out approximately 2-1/4 degrees, which gives very desirable stall characteristics. Let's get on to building.
Tail Structure: The horizontal tail is flat in lower camber so it can be built directly over the plans. Pin down the lower trailing edge 1/16 x 1 in, the lower leading edge 1/16 x 1/2 in, the 1/16 sheet lower center-section (leave a 1/8 wide gap in the lower center-section for the spar which will be added later). Insert the 1/16 x 5/16 lower tips and all the 1/16 thick ribs and install the 1/16 x 1/2 upper trailing edge.
Now add the 1/8 x 1/4 spruce leading edge. (This lays flat on the 1/4 face). A 1/16 x 1/4 balsa cap goes over the 1/8 x 1/4 spruce. Install the 1/4 x 5/16 tips and the 1/4 thick leading edge gusset, and tip gussets. You may want to install the 3/32 x 1/8 diagonal braces in the three bays outboard of the spar ribs.
Install the 1/8 x 1/4 spruce spar after securing the 5/32 OD brass tubing to it. This tube is what holds the stab onto the airplane, so wrapping the thread on them to hold them in place is a good idea. Epoxy is not necessary to use if the thread is smeared with Ambroid or Tite Bond. If you do use epoxy, however, make sure the inside of the tubing is free of it as it will really be a job to remove it after curing.
Install the remaining diagonal braces, upper center-section sheet, and 1116 x 3/16 capstrips. The stab is now ready for sanding.
The rudder is framed out in 1/4 x 1/2 balsa with 1/16 x 1/2 ribs. The trailing edge should be shimmed up with 1/8 thick scrap balsa to centralize it during the build-up. Install a control horn seat of a build-up to 1/2 or a piece of 1/2 sheet.
The vertical fin is a sandwich, consisting of a 3/16 thick balsa core, a 1/8 thick doubler on either side of a core, and a 1/32 plywood outer cap. The 3/16 leading edge core has a piece of Gold'n Rod inner tube bound to it..."
Force 5, Flying Models, June 1979.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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