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Project Patrol: LF-1.2

By Chad Jensen, EAA Homebuilders Community Manager, EAA 755575

Lyle Forsgren
Lyle Forsgren in front of his LF-1.2 homebuilt airplane, formerly a certified Schleicher Ka-7 sailplane

Motorgliders aren’t typically the first thing that comes to mind when we think of experimentals. While there are experimental motorgliders out there (great kits are available from Europa, Sonex, and other such companies), the idea of converting an old glider to a single-engine land airplane is something I hadn’t given any thought to. Turns out this idea has been fairly popular (although the new 51 percent rule makes it more difficult now), taking an older model sailplane and giving it new life by adding an engine. And I found someone who had done just that, right here in Oshkosh.

This month’s Project Patrol subject came about by pure chance, and I’m really glad it did. In a very short period of time, this project has proven to be very inspirational to me, and my hope is that it’s inspiring to you as well. Between learning my new job at EAA, traveling back and forth to Illinois while we plan our move to the Great White North, and building another airplane, my social schedule is tight to say the least. Case in point, it was a beautiful but windy Saturday when I had overbooked my day, but I had to make time to attend my first EAA Chapter 252 monthly meeting. This particular meeting was the Fall Chili Cook-Off, and it proved to be a delicious and worthwhile stop that day, even if only for a few minutes.
There were picnic tables spread across the hangar floor, and choosing a place to sit was a matter of throwing a dart at the proverbial board (well, maybe not in my case since I typically can’t even hit the board). The spot that I picked opened up an opportunity to write this article. Lyle Forsgren, EAA 79351, and his wife, Sandy, were sitting at the table that I chose.

I only had but a few minutes to polish off that wonderful bowl of chili and strike up a short conversation, but in doing so I discovered a man who has been designing, building, and flying his own airplanes for quite some time. Lyle is a longtime EAA member who worked for Boeing and Mercury Marine during his career. He and his wife have a beautiful piece of property with their own grass runway, and it’s a great place to design and build airplanes. He owns an RV-6A that he built and has an RV-12 project in his basement, but the subject of this article is Lyle’s LF-1.2, an airplane that began life as a Schleicher Ka-7 glider, popular in the late 1960s.

Lyle Forsgren
The Schleicher Ka-7 as seen just after its arrival at Oshkosh back in 2005

The LF-1.2 was preceded by the LF-1, Lyle’s first design, which is an award-winning single-place airplane with an outboard marine engine for a powerplant and was featured in Sport Aviation in October 1985. The LF-1.2 project is located in Lyle’s large freestanding hangar—and it’s a big hangar—big enough to accommodate the 52.5-foot wingspan of this airplane. The hangar is tucked away in the trees nicely and lends itself well to building airplanes.

The LF-1.2 uses only the wings and the empennage from the original Ka-7. The entire fuselage is of Lyle’s design, utilizing 4130 steel tubing. Mating the wings and tail to his fuselage took some accurate measuring, but that turned out to be the easy part. You see, the Ka-7 is a two-place glider, and Lyle has transformed it into a single-place airplane (single-engine land) using similar dimensions in overall length. To do this, he decided to position the engine behind the pilot, nestled in a spot under the wing, very near the CG, just before the fuselage begins to taper toward the empennage and where the rear seat would have been located on the two-place Ka-7.

Lyle chose to power his homebuilt with a 1.0-liter, inline, three-cylinder, 60-hp, fuel-injected engine pulled from a Geo Metro automobile—one that was produced from 1989 to 1994. This engine has been proven reliable for experimental aircraft, and as a matter of fact, it's offered fully converted from Raven Rotorcraft and Redrives Inc. The reduction drive offered by Raven is something that Lyle didn’t need; instead he chose to use a series of belts and pulleys to get the desired reduction ratio, according to the specs found on various websites for using this engine.

The belt system is comprised of two of the longest belts Lyle could find locally, which turned out to be 200 inches in length. The belts are rated at 30 hp each, so in order to meet his needs, a two-belt system was developed. It just so happens that it works nicely as a redundant system, though if he had a belt failure, landing as soon as possible would be necessary as the belt horsepower rating isn’t high enough to continue on one. But then, of course, it was once aglider. The belts are looped through a series of aluminum pulleys (that Lyle turned on his lathe) and run along the bottom of the fuselage toward the front of the aircraft. At that point, they turn upward through another set of pulleys to one more double V-groove aluminum pulley that’s attached to the propeller drive shaft, which finally turns the Warp Drive propeller. Sounds complicated? Perhaps to some, but it works!

Pulley system
See the entire belt system progression here.

Lyle designed this system to the belt manufacturer’s tolerance for twist and has had zero issues with it thus far. The belt’s tension is adjusted by sliding the entire engine fore or aft on its mount. The mount is made of a series of trays stacked on one another to get everything aligned and tightened down as needed.

According to Lyle, the engine was purchased for “less than $100 with the car still attached,” and he performed his own overhaul. He figures he has invested a few hundred dollars in the engine to bring it to the point of ready to run in airplane trim. Everything else he’s needed for this project he found lying around his shop. He just has the tubing on hand for building airplanes—why wouldn’t you?

The seat for the LF-1.2 came from an old car, the windscreen from a Rutan Quickie that he had stuffed away in the shop, and even the ambient pressure bottle (reservoir) for the variometer came from his refrigerator in the form of a 2-liter soft drink—with the cap now sealed. It’s this kind of homebuilding that is so inspirational to me. Resourcefulness goes a long way to bringing an airplane to fruition that you’ve designed and built from scratch.

Lyle Forsgren
The ambient pressure vessel for the variometer is a standard 2-liter bottle, with the cap sealed with Pro-Seal. It’s nestled under the propeller shaft. The chains in this image are used to support the airframe while the landing gear has been removed.

Speaking of fruition, the LF-1.2 is a certificated experimental amateur-built, fixed-wing, single-engine airplane and not certificated as a self-launch sailplane. You may not be able to tell from the photos in this article or the gallery, but in this configuration, this airplane has flown after having been signed off by Lyle’s designated airworthiness representative (DAR), Joe Norris, a person we’re all familiar with as EAA’s former Homebuilders Community manager.

The first flight occurred in the late spring of 2010. It wasn’t flown much after that, which is why it’s back in the state you see in these photos. Early flight testing revealed two problems that Lyle has been working on solving, one issue being that of cooling the engine. Part of the cooling, or lack thereof, is airflow through the radiator, the other is windage in the crankcase since the engine is installed vertical. He feels he has addressed the radiator airflow with a set of adjustable louvers on top of the fuselage between the wings.

The windage problem may have been solved by welding a bread pan to the bottom of the oil pan, creating a windage tray to enlarge the cavity around the crankcase.

The second issue Lyle had to deal with on the first few flights was tailwheel steering. Since the aircraft has only one main gear wheel, with tiny little wheels on each wingtip, once there was no longer enough forward speed for aileron control to hold the wings level, one of the wingtips came down to the ground. The ship then wanted to pivot from the drag of the lowered wingtip, but the castering tailwheel wanted to turn away from the down wing due to its pivot point being ahead of the wheel. This didn’t allow it to be taxied in a normal fashion, that is, if dragging a wing while taxiing can be considered “normal.” Lyle’s answer to this is a tailwheel pivot on a shorter arm, and direct-coupled steering.

Other changes to the engine involved rotating the throttle body (fuel injection—no carburetor, hence no float bowl), removing the exhaust gas regeneration (EGR) circuit, converting the wet-sump oil system to dry-sump, and moving the oil scavenge pump and distributor to alternate locations because they simply wouldn’t fit in the orientation chosen for the engine, which is vertical, flywheel down.

Lyle Forsgren
With the Geo distributor normally directly driven off and inline with the camshaft, Lyle had to adapt its operation from the side in order to fit everything within the confines of the fuselage. Larger view

With all these items addressed, Lyle hopes to have the airplane up and flying again soon. He can’t tell us when that will be because conditions need to be perfect, and it will be a decision made on that particular day when all factors are considered to be optimal.

One area that presented a small problem in this new airframe was the controls. Originally as a glider, the controls had a straight path from the base of the control stick back to the bell cranks actuating the rods that control the ailerons and those that connect the elevator. With an engine now in the way, the entire control system back to those points had to be redesigned.

Lyle Forsgren
The left side of the engine bay. Note the way that the elevator controls run outside of the airframe and then are neatly guided to the inside.

Both control inputs now had to make a trip down the sides of the fuselage first before heading aft. The ailerons are more complex, because not only do the rods have to make a turn toward the rear, but they also need to turn upward to the wings. And then turn, yet again, outward through each wing.

The elevator control is made from three different sections to make inputs properly, while the ailerons have six lengths of control rod action. Getting the angles and measurements right is critical, and Lyle has nailed it. The controls actuate very smoothly and are quite light and balanced. The wings from the glider still have the spoilers, and those are operated with a lever on the left side of the cockpit, using a locking mechanism put in place to keep them stowed when not needed.

Lyle Forsgren
The spoiler lever also actuates the main wheel brake when pulled beyond the full open position.

As mentioned, the fuselage is Lyle’s design, and while the aft section of the fuselage is fabric covered, the section from the nose to the aft end of the wing is covered by a fiberglass shell—call it a cowl if you will. This was made by modifying the fuselage from a Monerai self-launch glider that Lyle had acquired at one point. It was cut down the middle and spliced for the needed width to go around the tube structure he built. The fiberglass work is very nicely done, and it makes for a very unique-looking flying machine when installed. Lyle was just getting ready to put the covers back on the airframe on the day of my visit, perhaps to pull it out to fly it again soon.

The time invested in this project over the course of four years is estimated at 800 to 1,000 hours, although Lyle admits that keeping track of hours worked isn’t on his list of priorities. “It’s done and ready when it’s done and ready,” Lyle says.

The LF-1.2 aircraft is designed as a simple, single-person, fun flying machine, and so far Lyle has enjoyed the process of getting it to this point. He says that once the airplane is rolling and the dragging wingtip is lifted from the ground, it’s a lot of fun to fly. It carries about 5.5 gallons of auto fuel in a custom-made aluminum fuel tank that’s fitted just in front of the instrument panel and between the pilot’s legs, which is plenty of fuel for a gas-sipping three-cylinder engine to power the climb to altitude. Once there, the engine can be shut off for glide for a while, or rather the pilot can leave the engine running and fly over for breakfast on a local grass strip.

Lyle Forsgren
There are lots of details in this picture: custom T-shaped aluminum fuel tank, fuel delivery system, belt drive, cables, control rods, and ambient pressure bottle. Lyle’s work on this airframe and systems is quite extensive.

This design has really piqued my interest, and I found myself looking for a glider in need of restoration to create a motorglider of my own! As mentioned, Lyle won’t tell us when the next flight will be, but when he has the bugs worked out, he will be more than happy to show off the airplane—a fine example of what a homebuilder can do with the freedom to create an airplane in his own garage.

We’ll be certain to publish a follow-up report once Lyle’s LF-1.2 is flying again. For more images, please see the gallery.


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