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Glen Marshman’s RANS S-9 Chaos

Strictly Business

By Glen Marshman, EAA , for Experimenter
Photos by Bob Rubino

This article originally appeared in the May issue of EAA Sport Aerobatics

Glen Marshman

My goal was to build a new aerobatic airplane that would be competitive in the Intermediate category, fit into the light-sport aircraft (LSA) category, be cheap to fly and maintain, and cost $35,000 or less.

When the proposed LSA rulemaking came out, I thought it was a great idea. It seemed to finally be a cost-effective way to have fun flying. I flew out to the RANS factory and met up with founder and owner Randy Schlitter. I was very impressed with the factory because it was very clean and high tech. When I was there, I flew an S-6 – the closest thing to an ultralight I’d ever flown, but it was a real airplane! In the corner of one of the RANS hangars was an S-9. It was a neat-looking little bird, so I asked about it. But it was out of production at that time and went to the back of my mind.

I built a Pitts S-1S and competed in it for years. I’d spent a ton of money on the project – equivalent to three S-9s. Wanting to do something new, it was time for me to make a change, so I called the factory and asked about the S-9. I was told it was back in production; I reserved a production slot.

While the factory was making parts and compiling kits, I gave thought to how I could go about making this little bird really perform. The answer was simply to build it light and give it a lot of horsepower.

580.7-cc two-stroke engine
This fire-breathing little 580.7-cc two-stroke engine is capable of pumping out nearly 100 ponies!

The plans call for installing the 65-hp Rotax 582, but there’s a higher power alternative. Steve Beatty, owner of Airscrew Performance, builds a Rotax 583 that puts out close to 100 hp. The 583 is almost identical to the 582 but doesn’t carry an aircraft designation. Unlike the 582, the 583’s single ignition is solid-state with electronic ignition control. In addition, the 583 sports the Rotax Adjustable Variable Exhaust (RAVE), with variable exhaust ports. This combination allows the 583 to produce 97 hp on the same displacement as the 582. To use this carbureted engine on the aerobatic S-9, Mikuni pumper carbs are put in place of the standard Bing units. A ground-adjustable two-blade Warp Drive propeller set at 8 degrees gives a consistent 7,500 engine rpm, and the airplane leaps forward like an Extra on takeoff.

The tuned exhaust was reported to be “challenging” to install correctly

The tuned exhaust was reported to be “challenging” to install correctly

Click images for larger views
The tuned exhaust was reported to be “challenging” to install correctly, but it sure looks like Glen pulled it off.

The kit is pretty straightforward, but I’m not sure it’s for a first-time builder. I’ve built a RANS S-6, and its much higher sales volume has allowed the factory to refine the kit and plans to a greater degree than the lower-production-volume S-9. In addition to a large network of S-9 builders, RANS technician Ed Schwab has built an S-9 himself and is very helpful, so you’re not alone during the build by any means.

pre-welded fuselage
The pre-welded fuselage comes from the factory, with all fittings and tabs in place.

J-B Weld was used to bond the aluminum leading edge skin to the tubular forward spar
J-B Weld was used to bond the aluminum leading edge skin to the tubular forward spar.

left wing poly fuel tank and wing-walk deck
The left wing poly fuel tank and wing-walk deck are ready for final attachment.

PVC plumbing pipe and fittings
PVC plumbing pipe and fittings were used to make the fixture for rotating the wing.

Click images above for larger views

Glen Marshman

I made a lot of nonstructural changes, mostly for ease of maintenance and simplification. Because I’m of smaller stature, I moved the instrument panel 7 inches aft to allow better access while seated. The configuration also allows good access to the rear of the instruments, making maintenance a breeze.

instrument panel

instrument panel

Click images for larger views
The instrument panel has been moved 7 inches further aft than what the plans specify, allowing for better access to either side.

The plans call for fabric covering aft of the firewall, but I decided to fit removable aluminum panels so I would have easy access to the rudder pedals and brakes. One structural modification I made was to replace the stock S-9 rudder with one from the RANS S-7. This gives me about 15 percent more surface area and increases yaw authority substantially. Because the hinge points are the same, it just bolts in place.

rudder installation
The larger rudder installation, borrowed from the S-7, was a simple bolt-in modification which looks right at home on the S-9.

For electrical power, I chose a KW voltage regulator. The beauty of this unit is that it needs no minimum startup voltage. In addition to powering the radio and tRANSponder, it tops off the miniature sealed battery I mounted to the firewall so I can listen to the radio with the engine shut off.

electrical system
A minimal electrical system only requires a simple voltage regulator to keep the juice flowing and the battery topped off.

Some of my mods created a few challenges. I tossed out everything I could to save weight. That means one 9-gallon fuel tank mounted in the wing root (along with the header tank located under the instrument panel), no electric starter (pull-start), and a smaller than normal battery. It isn’t a cross-country airplane, and I have no provision for baggage. I also use a fuel-oil pre-mix to save on weight by not having an oil tank and an injection system. This also adds a level of safety, eliminating the concern for a failure with the oil system.





Click images for larger views

Making It Pretty
For paint, I contacted Dan Stewart of Stewart Systems which manufactures a waterborne paint that uses an ecologically friendly process. The top coat lays down differently than thinner-based urethanes. There are no toxic fumes or combustibles to be concerned with; it cleans up with water so it’s eco-friendly. I’ll never use anything else again.

The engine masked and the fuselage ready for paint

Green glue binds the fabric to the tubular structure.

Control surfaces
Control surfaces “before”

Control surfaces
Control surfaces “after”


With everything complete, my final build weight, with radio and tRANSponder, came in at 411 pounds empty.

Summing Things Up
The positive side of building and flying the RANS S-9 is the low initial cost for a new airplane and the fact that it’s inexpensive to fly and maintain. It has a simple and inexpensive two-stroke engine that burns between 3 to 7 gallons/hour (with the stock 582), depending on how hard you flog it. I built it light and simple; the RANS S-9 isn’t an Unlimited-performing airplane, nor was it intended to be. Whatever class it can compete in, the project will be a success for me.

I’ll contribute an upcoming piece covering testing and tuning of the airplane I’ve named Strictly Business, as well as a flight report, in a future issue.

First flight of Glen Marshman’s RANS S-9 Chaos Strictly Business, January 14, 2011


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