Skycar (oz6551)

About this Plan

Skycar. Radio control scale model.

Quote: "Ken Willard and Bob Andris present their spectacular R/C version of the full-scale rhomboid-winged Phoenix-Warren S-31.

Sometime in 1970, if present plans materialize, a 'new' sport airplane will be test flown in England. Known now as the Phoenix-Warren S31, it is a development of a design first conceived by Norman Hall-Warren in 1926! The wing layout was patented by him in 1937, and tests have been made intermittently with free flight and wind tunnel models ever since.

The original concept was for a cabin type plane, with the engine in the rear, which was relatively easy to balance because of the shape of the wing and the location of the Center of Gravity.

You can take your pick of the ways to describe the Warren-Young wing configuration - call it a Rhomboid wing, or a tandem wing with sweptback forward wing and swept-forward rear wing - or a swept back wing with a stab that sweeps forward and meets the wing tip. No matter what you call it, you have to admit that it IS different.

My friend Bob Andris, while searching for an unusual design for RCM's design contest about a year or so ago, picked this design. However, he became embroiled in other projects and let it drop for a while. I became interested and began to rekindle Bob's interest about five months ago, and together we decided to build a radio controlled model of the Skycar.

Bob corresponded with Norman Hall-Warren, who replied and gave us all the specifications necessary to build the model, including permission to publish the design if we found it successful.

So we set about it. Bob built the wing, and I designed a fuselage which would accommodate the radio up front and the engine and fuel tank in the rear. Before getting it underway, though, I built a small glider and experimented with fin size, CG location, and developed what appeared to be the best combination.

Some of the claims which the inventor of the design makes are that it won't stall, won't spin, and has great stability due to the 'scavenging' effect of the closed wingtip, where the spanwise flow outward on the forward wing is counteracted by the inward flow on the rear wing. It certainly promised to be a very interesting project.

Building the fuselage was a very straightforward job, requiring very little ingenuity, but the wing is something else! The twist in the rear wing requires that you make a sort of jig to block the tips so they sweep up to meet the forward wing, and the centersection has to be blocked up at the trailing edge so that you get the six degrees differential to the forward wing incidence. It takes some doing, and you have to be careful that both rear wings have the same twist from root to tip. The photos show how the setup looks.

No detailed radio installation is shown on the plans, since it will depend on what type of equipment you have. In our case, we used the Kraft plastic mounting tray, which made a very simple and accessible installation. Note how the forward hatch is hinged so that it swings up for access to the switch which is mounted integrally with the servos on the tray.

The nose gear was a little tricky, until I found an old Babcock escapement rudder yoke which I soldered to the top of the nose gear wire to use as a steering arm. I found that it worked perfectly, but if you don't have one, you can make an arm, or use one of the commercially available ones. However, none of the commercially available nose gears were of the right size, so I bent my own, using Jim Sunday's handy dandy wire bender.

The plans show the rest of the construction in sufficient detail for the average builder, and frankly, the Skycar is not intended for building by a beginner - even though the flying qualities are amazingly gentle..."

Supplementary file notes

Article, thanks to JHatton, AugustaWest.

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