Jerry Boggs Super KR-1
What HAPPEN if you took a professional craftsman who has on occasion turned out beautifully restored examples of early Mercedes touring cars, rare Ferraris and exotic Bugattis ... and turned him loose on a homebuilt airplane? Well, talent is talent, and assuming our craftsman has some aviation background, likely as not he is also going to turn out a beautiful airplane. That certainly was the case at Oshkosh last summer when Jerry Boggs showed up with his Super KR-1.
Unfortunately, a lot of EAAers missed the opportunity to drool over this little airplane because Jerry had to leave early in the week to get back to the world of auto restoration, but those who did can enthusiastically bear witness to the superb craftsmanship that went into its construction.
Jerry calls his homebuilt a Super KR-1 because indeed it does incorporate a sufficient number of changes from the Simon pure Rand-Robinson version to justify a qualifying prefix to the name ... and it's the nature of some of these changes that make "Super" seem appropriate.
Looking at the airplane, your attention is instantly drawn to the unusual 3-blade propeller -- so let's start there in our laundry list of modifications and work our way to the tail. The prop looks like something Bernie Warnke might have made initially for a 180 Lycoming, then decided to saw off the blades at the decal location so it would fit the KR-1. Obviously, the airplane is not powered by the customary VW engine.
Jerry originally intended to use a VW and, in fact, bought one to convert. He changed his mind, however, when he ran across a little 65 hp Lycoming O-145. Weighing about 165 pounds and not significantly larger in physical dimensions than the VW, the little Lyc looked like the way to go ... and, besides, it was "aircraft" he reasoned. But before he got around to installing it in the airframe, a third choice presented itself. A Trade-A-Plane ad for a GO-145-C seemed too good to pass up, so Jerry gave the owner a call. An air boat operator in Florida had already placed a deposit on the engine, but the owner, an EAAer, hated to see it put to a non-aircraft use. After talking airplanes for a while he agreed to sell the engine to Jerry and send back the air boater's deposit.
The GO-145 is an interesting little engine that occupies one of the more obscure corners of aviation history. Lycoming came out with their O-145 in the late 1930s and built several series of it until the great lightplane industry bust of the late 1940s sounded the death knelt of the Great American 65 Horsepower Lightplane ... the production of them, that is. The O-145 started life rated at 55 hp at 2300 rpm and with a "cruising" rating of 42 hp at 2100 rpm. It had a displacement of 144.49 cubic inches and a compression ratio of only 6.65 to 1. It weighed 165.5 pounds in the O-145-A configuration and 167.5 pounds as an 0-145-A3 - which signified the addition of a starter and generator drive. The O-145 was a good little engine, but had a hard time keeping up with the Continental A-50 and its 171 cubic inches. And when Continental upped its compression ratio from 5.4 to 1 to 6.3 to 1 and went from 50 hp at 1900 rpm to 65 hp at 2300 rpm, Lycoming had to try to keep pace. They boosted compression on the O-145 to 6.5 to 1 and tweaked the little 4-banger up to 2550 rpm so as to pull 65 hp. Continental, with those extra cubes to play around with, cranked up the revs to 2600 and got 75 horsepower out of their engine (A-75) ... then upped compression to 7.65 to 1 and went to 2700 to thump out 80 hp (A-80). This left the little Lyc gasping for breath, but the company valiantly forged onward and upward by twisting the revs all the way to 3100, where they claimed 75 hp. Well, as they say in auto racing, "there ain't no substitute for cubic inches." Even though they had the same rated power, pilots noticed that a 65 Lycoming powered Cub or Taylorcraft just didn't seem to have the guts of a 65 Continental powered bird-of-the-same-feather on a hot day with a heavy load Ditto the 75 horsepower jobs. The problem, of course, was that the higher revving Lycomings didn't enjoy the propeller efficiency of the slower turning Continentals ... especially the 75 horsepower O-145-C.
In an attempt to get back the prop efficiency, Lycoming decided to gear the O-145. They added a long nose to the case and stuffed it with toothy little gears with a ratio of 27 to 17. They rated the engine at 75 hp at 3200 rpm and, indeed, it seemed to pull with a lot more authority than did the direct drive O-145-C. Thee's no free lunch, however ... the weight went up to 193 pounds, 195 with starter and generator drive. The engine was certified and used on the Piper 5-5 Cruiser, the Funk B75L, the General Skyfarer and the prototype Rich Twin 1-X-2, an unusual little tri-gear twin with the engines mounted up over the wings in the pusher configuration. The installation was never as popular as the Continental A-75, however, and Lycoming eventually threw in the towel on the O-145 to concentrate on their infinitely more successful O-235, the grandaddy of all their four-bangers that power so many of today's lightplanes.
The GO-145's gearbox predictably was a problem. Just as with the postwar Continental GO-300As used in the Cessna 175, pilots insisted on lugging the engines at low power settings ...which quickly resulted in some expensive noises emanating from the gearbox.
Ah, but I diverge ... let's get back to Jerry's KR. It's the GO-145, you see, that gives his tiny bird a muscular look up front and was what caused Bernie Warnke to have to build such wide, stubby little blades for the propeller -- a powerhouse combination for a little KR-1. The engine is mounted on a swing-out mount, as per Fred Keller's plans. The stock Piper J-5 exhaust system, including the muffler was retained so only one pipe extends from the cowling.
The fuselage came in for quite a number of changes to permit use of the Lycoming. It was lengthened from 12.5 to 15.5 feet (including the 14 inch spinner) and the firewall was beefed up. 3/32 plywood was used to line the inside of the fuselage frames back to the seat and urethane foam was sandwiched inside for insulation - resulting in an unusually quiet cockpit, according to Jerry. The built-in fiber glass fuselage fuel tank shown on KR-1 plans was eschewed in favor of an aluminum one Jerry heliarced together out of .050 sheet. It has the advantage of being removable -although it is a half hour job.
The rudder pedal and stick installstions are also from Fred Keller's' plans ... and, as you can see in the accompanying photo, are in uncommonly luxurious surroundings for so tiny an airplane. The seat covers came out of a brand new VW Rabbit that had been totalled and the fuselage side panels are covered in a similar material.
As you can also see in the photos, the vertical fin and rudder have been enlarged and are altaed in profile from the stock KR configuration ... to an aesthetic advantage, in my opinion. 3 hinges were added to the rudder and the horizontal stabilizer received 3 spars -- for strength and to add a little weight at the opposite end of the lever from the engine. The elevator is balanced ... as are the ailaons. Three leaves were used in the tailspring and an overaize tailwheel was fitted to handle the anticipated extra weight of the Supes KR-1.
The wings pretty well follow the Rand-Robinson formula except there's an extra foot of span to keep the wing loading in roughly the same ball park with the VW powered versions. Stock Rand Robinson gear leg struts were used but have a 4130 plate epoxied on the top of the casting to provide more bearing area when it is bolted to the tranverse leaf spring. Some KR owners have had cracks develop in their gear castings and Jerry thinks his fix may be the answer. So far he has found no cracks, so he may be right.
Finishing is Jerry's forte ... he has been in the body and fender and painting business for the past 32 years ... and it showed in the finish of his airplane. Interested in how a pro would do the job, I questioned him at length on his methods. First, however, you should know that early on he deceided against using Dynel. (I'm assuming here that most of you have at least a passing acquaintance with the Rand-Robinson foam/Dynel/epoxy construction method.) In addition to more scientific testing, one day he dropped a screwdriver on a sample and didn't care too much for the ease With which it penetrated the cloth. His ultimate decision wes to use 8 ounce fiber glass cloth instead. Jerry started out using a particular brand of epoxy resin, only to have the company go out of business. He switched to another label with no noticeable adverse effect and finished the airplane with it.
Jerry's finishing sequence went like this: first, two coats of epoxy were worked into the glass cloth; next came a coat laced with microballoons; then, coats of 100S DuPont primer (a product recommended for use in fiber glass work and which is compatible with polyurethane paints); and, fianally a basic coat of white Sherwin-Williams acrylic enamel with the so-called "plasticizers" added. The brown and green trim are Imron. Mow, if you have ever been within shouting distance of a homebuilder's shop, you know I've completely skipped over the hard parts . . . the hours and hours of back breaking, knuckle skinning, dust producing sanding. No, those super finishes don't come out the can, troops.
Jerry's technique in the primer phase, involves spraying on a cat of light gray primer, then a mist coat of darker gray. Sanding quickly reveals voids and high spots that have to be worked out to the level of the rest of the surface. With his years of auto body work experience this was the easy part of the project for Jerry . . . and it was obvious at Oshkosh. Nothing else there had a better finish than his Super KR-1.
A lot of EAAers stopped by to inquire about the finish and how they could duplicate it. Jerry's answer was always the same -- it's not so much the brand or type of materials used, it's patience and elbow grease that REALLY make the difference.
Incidentally, the tasteful paint scheme is not the one originally planned for the airplane. Jerry admits his wife talked him out of whatever colors he had intended to use and into the present white, brown and green. Well, anyway, SOMEBODY made some good choices.
The KR-1 had been started in July of 1974 and after 4 years and 10 months of building and reworking it into a Super KR-1, the little bird was completed and licensed on May 19, 1979. It was flown for the first time on June, 1979. The airplane itself has flown well from the start, but props have been a problem ... and maybe the engine. The first flight was made with a Hegy prop but it allowed the revs to go all the way to 3800! The original Warnke blades had very thin tips and Jerry thinks they flattened out enough at high rpm to almost stop producing thrust. Whatever, it simply wouldn't get the plane off the ground.
All the fiddling around with propellers made it impossible to get the Super KR's time flown off prior to Oshkosh so Jerry trailered it in for the few days he could stay. This made it ineligible for judging, but, at least, members had the opportunity to admire his handiwork and profit from some of his ideas. One that got a lot of attention was the fact that his fairings, including the gap strips at the wing attach points, had no screws, clamps or other mechanical fasteners. Instead, they are stuck on with the 3-M double-faced tape normally used to attach automobile side molding on new cars. Really slick.
Since Oshkosh Jerry has done further flying ... and experimentation with the latest Warnke blades. He has not been able to get up to rated rpm with them and has recently turned his attention to the engine. After cold weather hit Ohio, he brought the KR home and tore down the Lycoming.
At this writing (late January), the engine is back together, but extensive testing will have to wait until warmer weather. (Stop laughing, you Sun Belters!)
Jerry Boggs (EAA 65200) resides at 1141 St. Agnes Ave,Columbus, Ohio 43204. He works for an outfit apropriately named The Body Shop. A life-long aviation enthusiast, he soloed in 1944 and has been flying regularly ever since. His first EAA Convention was the last one in Rockford (1969) and he hasn't missed one since.
Once he gets the engine/prop combinatian sorted out on the Super KR-1, Jeny wants to build a set of the new long wings ... to make his bird a Super KB-1B. His immediate goal, however, is to be flying at Oshkosh '80.