Hale Wallace’s Skybolt
(From Sport Aviation, 06/1998, Page 74)
By Budd Davisson
Photography by Jim Koepnick and Leslie Hilbert
My mind was in biplane mode: Head back, vision foreshortened and out of focus so my eyes were staring straight ahead, my peripheral vision watching both sides of the runway at the same time. I was seeing everything but focusing on nothing. My left hand started forward and what had been a steady rumble from under the cowl which rocked the Skybolt even as it sat on the end of the grass runway became an enraged beast. The airplane lunged forward, the wall of noise rolled back over me and I had the weirdest feeling I had just passed beneath a lion’s fangs and was rocketing out the back side of his maw.
Three hundred and twenty-five horses were reducing the hangars and edges of the runway at Shiflet Field, Marion, NC to meaningless blurs. They were of no consequence. Only the shallow circle which encompassed the airplane’s nose and the edges of the runway counted. I kept waiting for the acceleration to let up for the speed to become constant. As the tail came up and more of the runway came into view, the seat kept insisting itself upon my backside. The runway kept flashing past and I approximated a slightly tail down attitude. Taking a second breath hadn’t yet occurred to me when the airplane skipped once and clawed its way into the air.
I glanced at the airspeed. It was already racing through 110 mph so I pulled the nose up. Then more. I stopped at what looked like a suitably ridiculous angle that held the 110 mph. The VSI was lounging around 2400 fpm.
So this is what happens when the boss builds himself an airplane. This is what a Skybolt feels like when Hale Wallace, operator of Steen Aero Lab (704/652-7382 [current phone: 321/725-4160] ), home of the Skybolt, builds one for himself.
Hale spends most of his waking hours working on biplanes and compo.nents for them. He not only is the exclusive distributor for Brunton flying wires (which makes him the sole source for ALL flying wires since MacWhyte closed down) but he also owns the rights and sells plans for the S-1C series of Pitts Specials, including the Super Stinker wing update for the four-cylinder airplanes. He has the same rights and plans for the Knight Twister (he’ll have one of them at Oshkosh this year, and is it ever cute!) On top of that, he is the exclusive U.S. distributor for the Hoffman series of fixed and constant speed propellers.
Most of what Steen Aero Lab does, however, has to do with Skybolts: plans, finished components up to wings and fuselages. Hale Wallace is Mr. Skybolt, worldwide.
So, when Mr. Skybolt decides to build himself an airplane, what makes it different from the rest?
Hale Wallace
Basically, this airplane is built right to the plans, says Wallace. We did, however, spend a lot of time at reducing weight everywhere we could. For instance, for the firewall, we used .020 titanium, which not only saved around six pounds, but titanium is much easier to work than stainless steel.
Titanium is used liberally through.out the airplane and each use is documented by engineering back-up.
All of the heavy bolts, like attach bolts, are titanium. So are the drag/anti-drag wires and all the push-pull tubes. We used it everywhere it made sense and the numbers looked okay, he says.
We used the Haigh locking tailwheel for a number of reasons, weight being one of them, Hale points out. It’s three or four pounds lighter. It also, however, lets us get the tail down another cou.ple inches and we need the prop clearance.
Although the wings are still basic Skybolt, there too Wallace has put his experience to work.
The wing spars are routed, using a hard tooling template we’ve developed. That alone saves about 15 pounds an airplane depending on wood density. In total, we’ve knocked about 30-35 pounds out of the wings alone, he says. In building the wings, he also put his experience to work to get the most roll performance possible out of the basic Skybolt wing design. He has done Skybolt wings using the Pitts Super Stinker aileron technology (symmetrical ailerons with special nose profile), but decided to stay with the normal ailerons on this one.
Wallace says, Good roll rate and response is due as much to the fit of the ailerons as their design. What we do is finish the wing up through the first coat of silver while working at getting all of our aileron gaps down to less than a quarter of an inch. Then we close up as much of that gap as possible with balsa filler strips and put the finish tapes over the balsa. By waiting to finish the aileron wells until after the fabric is fairly tight, we eliminate the problems of distorting the aileron wells in the final covering steps.
Wallace is especially proud of the canopy on the airplane.
Anyone who has ever done a canopy installation on an airplane swears they’ll never do another, Wallace laughs. This canopy solves the problem of making everything fit because you build it on the airplane. I saw a photo of a similar type of canopy on a Skybolt built by Francois Mounier-Poulat in France 20 years ago. Francois, by the way, is now my sales representative over there. We took the concept and refined it. The entire assembly only weighs about 12 pounds, which, if you subtract the weight of the open cockpit windshields only adds about 10 pounds to the airplane.
The canopy bubble is glassed into a form-fitting apron and attached to the airplane by a trapezoidal steel tube frame which swings from behind the pilot when open, and lays on the longerons when closed. A spreader bar bridging over the instrument panel is made of cross-grain balsa for light weight and easy bending and is captured in glass cloth and epoxy for rigidity. The bar is only there for a handhold, according to Wallace. The bubble pivots up and back, completely opening up both pits for exit and entry.
Another aspect of Wallace’s bullet is the engine. Hale went to Monte Barrett, who is best known as one of the premier builder of aerobatic engines, but is now accepting orders for more normal engines. Normal in this case included taking a lowly 235 hp O-540 Lycoming and swapping parts around until it was putting out close to 325 hp on the dyno. This includes one of Barrett’s cold-air induction units.
As the U.S. Hoffman importer, it is no surprise one of their three-blade, composite props caps off the propulsion department on the Wallace Skybolt. The airplane is finished in Randolph dope.
For health reasons, I try to stay away from any of the polyurethanes, Wallace explains. Also, I always use Razorback on the fuselage because it is nearly bullet proof and has a neat appearance on the inside. I’d prefer to use cotton on the wings, but you can’t find good cotton, so I use dacron like everybody else.
Whatever he uses, the airplane looks terrific!
As I climbed on board Wallace’s airplane, I’ll have to admit I first thought the canopy arrangement to be a little fragile looking and probably hard to manage. I was wrong on both scores. All I had to do was reach be.hind my head and urge it forward until the canopy pivoted down and I held it by the spreader bar. There couldn’t have been more then a pound or two in my hand. It was necessary to pivot the canopy so the nose was pointed down hill. From then on, it was a simple matter of dropping it into place and locking the two canopy latches. To jettison it, all I had to do was pull a pippin on either side of the cockpit.
Hale had warned me to keep the stick back while the engine was run.ning because letting the stick forward could raise the tail with the smallest application of power. As I moved out towards the runway, I could see what he was talking bout. There was absolutely no doubt that there was a truckload of horsepower under the hood.
I’m not a fan of locking tailwheels on little airplanes, but this one worked quite well. Wallace had used the throttle assembly off a lawn mower as the engage mechanism which was located under my left hip. With the tailwheel locked, it drew a rail-straight line. With it unlocked, the airplane was perfectly willing to go someplace else and took some brake to stay on top of it.
That first takeoff was exhilarating, to say the least. It was right up there with any of the rocket-powered aerobatic specials. Just keeping the speed down to an acceptable level during the climb was an interesting chore. Later I tried climbing at best rate, which is down around 90 mph, and the angle had to be approaching 45 degrees. It was ridiculous and fun at the same time. The rate of climb was well over 3,000 fpm.
In a couple of minutes after that first takeoff, I was at 5,000 feet and let the nose down and the speed build. And build. Showing 2350 square, it stabilized at about 165 mph indicated which at that altitude and temperature was well over 170 mph TAS. This has to be the fastest Skybolt in history! Hale said his two way average going to Tulsa for the biplane bash was 176 mph at less than 13 gph. Now, that’s hauling for a big biplane!
Incidentally, I tried running at reduced power settings just to see how much of the speed was due to brute horsepower and how much was airframe related. Backing the power off to what I guessed to be more normal power, only brought the airplane down to about 150 indicated, so it was still quite fast. This is undoubtedly because the airplane was probably the straightest Skybolt ever built.
This airplane was an easy 35 mph faster than any Skybolt I’d ever sat in and that extra speed was noticeable in a number of ways. At normal Skybolt speeds, the aileron pressures were lighter than most I’d flown, about on a par with a Pitts S-2A with fairly quick response. Don’t forget, a Skybolt is much larger than a Pitts, so shouldn’t be as nimble, but it’s closer than you’d think. As the speed went up, the pressures built slightly until they were about the same as the S-2B, but the roll rate increased at the same time.
The canopy seemed to let the entire world into the bigger than average cockpit. That’s always been one of the Skybolt’s strong points: It’s cockpit size and shape makes it really comfortable. You’re sitting there, legs spread wide, lying back at just enough angle for it to be easy on beat up backs like mine, while the incredibly smooth Lycoming up front is helping you stack up the miles. No homebuilt biplane is Cessna-stable but the Skybolt comes close. Combine that with a good GPS and the urge to go someplace usually can’t, and shouldn’t, be resisted.
The airplane had so much more straight level speed than most Skybolts that dropping the nose for any kind of overhead maneuver was overkill. It was perfectly happy to loop out of level flight and hold its altitude. In fact, if you weren’t careful, you’d gain altitude. It would do a half-vertical roll from max level with a hammerhead turnaround and another half roll on the way down without breathing hard. Dropping the nose just a tad gave 200 mph and it would do anything from that speed.
The speed gave the airplane a ballistic feeling that I generally assume to be coupled with a much higher wing loading. This lead to a misperception on my part. It felt like a heavy airplane, so I flew approach like it was a heavy airplane. Here again, I was wrong. Let the record show that 90 mph over the fence is entirely too fast for the airplane. After a lovely, easy to control, slipping approach, I blew it and floated half the length of the runway before it decided to land.
Power up, let’s try that again.
This time it was 85 mph. Skybolts are all wonderful slipping airplanes which does away with any blindness factor until just about ready to touch down. Even then, the visibility is much better than most taildraggers. Let the record show that 85 mph is still too fast. Too much float. Too much runway behind me on touch down.
It became obvious the diet Wallace put this airplane on had paid off and it was going to take a bunch more approaches before I had it figured out. What I didn’t have to figure out, however, was the ground roll. Once it touched down, I’m not certain I moved my feet at all. Most Skybolts are pussy cats, but this one was nose-wheel simple. Maybe there’s something to this locking tail-wheel thing after all.
Ignoring the massive amount of power, the most important factor one should bring away from studying Hale Wallace’s personal Skybolt is that attention to detail pays off. There was nothing about the airplane that was overtly fancy. No chrome. No super-stitched upholstery. No fancy anything. However, there was absolutely nothing out of line. No gaps that were uneven. Everything was simply right. It all fit and lined up. That meant the airplane flew the same way. It was absolutely one of the most die-straight airplanes I’ve ever sat in and that alone made it a pleasure to fly. Toss in 325 of Barrett’s famous ponies and what’s not to like?
When the boss builds an airplane for himself, he builds it the way he wishes everybody would and it shows.
NOTE: You can view more articles by Budd Davisson on his website: Airbum.com