ISON Tandem AirBike Builder's Log

April, 2000 -- Southern Airplane Tour

Tour of airplanes, that is -- not by airplane. Our primary motive was to go aero-shopping at Sun 'n Fun, but the missus and I managed to squeeze in 5 more aviation-related stops as well as a couple of "vacationy" days on Sanibel Island, Florida.

First we drove to Lexington, KY to see the only Tandem AirBike that has been powered by the 80hp Jabiru 2200 4-cylinder 4-stroke engine. It was built by Steve Wright of Wright Aircraft Works LLC, and is now owned by Alex Boone.

Steve feels that the Jabiru is an ideal engine for the Tandem, but then he also likes to have a 503 on his single-place AirBike, so we know he likes power! Steve did a really nice job incorporating the Jabiru into the Tandem, adding a simple dynafocal-type mount to the front of the Tandem's fuselage (which is SOP for the Jabiru).

Steve also did a slick job of melding the Jabiru's stock fiberglass air scoops into the Tandem's stock fiberglass engine cowl, ending up with a custom-looking one-piece "cowl." If you look just in front of the rudder pedal in the photo above you can see a large piece of rubber tubing projecting from the carburetor back into the fuselage where the air filter is mounted. I was skeptical about how this large engine would look on the Tandem's nose, but pleased to find that it really does look good there. And the performance must be truly amazing with all that power.

Here's the instrument panel, with a custom fiberglass instrument box made by Steve on top. You can see the air filter below it. Alex says the red BRS rip cord on the right is mounted in the best location they've been able to find for it, but he still isn't wild about the location. Cold, windy weather prevented Alex from taking me for a ride in this bird. Alex says the sides of the windshield flex inward at medium-to-high speeds which drastically reduces the front passenger's protection from wind. He recommended some sort of a brace that will prevent this from happening.

Our next stop was Wallaby Ranch, a wonderful hang gliding resort SW of Orlando, FL. We camped out here for two nights, just left of the glider on the ground at far left, while we were in the area for Sun 'n Fun. In this photo you can see an Australian Bailey-Moyes Dragonfly doing what I hope to do to some degree with my Tandem -- towing a hang glider aloft. The Dragonfly was designed specifically for this purpose but is a bit expensive for my taste.

I enjoyed one tandem instruction flight with Malcolm Jones, the Grand Poo-Bah of Wallaby Ranch. He has six of these Dragonfly tugs, and described times when there are 60-80 gliders in the sky above the ranch. I'm finding it really tricky to transition from 3-axis flight to weight-shift flight, as the pitch inputs feel completely backwards. In a 3-axis you pull back to go up, but in a weight-shift glider you push forward to go up. Someday when I can enjoy a large chunk of glider time at once I'm sure I'll be able to burn the reflexes into my nervous system, but it's really frustrating just doing a little at a time.

Once you get used to not having any airframe below you whatsoever, hang gliding is really sweet. Since you're only flying around 30mph and there is no engine, it's super quiet and relaxing, and the relative wind seems almost nonexistent compared to a powered plane.

This is one of the powerplants of choice for ultralight tugs these days, and I am strongly considering using this combo on my Tandem. It is a Rotax 582 with a 4:1 gearbox and a 6-blade Ivoprop. It's actually two 3-blade Ivos ganged together, but Ivoprop sells it as a unit and includes the required longer bolts and spacers.

The reason for the 4:1 gearbox is to slow down the prop (the main noise-producing part of the powerplant), making it much quieter. The extra blades are added to make up for the loss of thrust from the lower prop speed. They're also using a pricey add-on clutch inside the gearbox which smooths out the engine's power impulses and also allows the prop to freewheel at low rpms. This adds drag at idle helping the tug to descend rapidly so it can get down fast and hook up another glider.

At Sun 'n Fun I visited the HKS/Flightstar exhibit and inquired about the engine my friend Robert has been waiting for. I was assured that the engine's problems have been fixed and that they'd be rolling off the production line in 1-2 months. When I asked about what I had read about the 60hp HKS 700E only giving performance similar to the 52hp Rotax 503, I was offered a ride in an HKS-equipped Flightstar II just a few paces away on the ultralight runway. Well, OK, twist my arm...

The photo above is of the HKS on the airplane I flew (notice the trike in the ultralight pattern). The demo pilot let me do most of the flying, much to my delight, and I have to say that more of my attention went to flying the airplane and watching the airshow traffic than evaluating the engine. What I do remember about the engine is that it wasn't very loud, it wasn't quite as smooth as I expected and it wasn't as powerful as I expected. This may be terribly unfair as I was so (happily) distracted by flying the plane, but it seemed like cruise rpm (+/- 75%) was just about enough to keep us from losing altitude. And perhaps I was unfairly attributing roughness to the distinctive sound of the muffler's unusual can. The flight was way too short and I wish I could do it again and pay more attention to the engine.

Midway through our subsequent stay on Sanibel Island, we drove to Immokalee, FL (NNE of Naples) to see Tariq Ebrahim's single-place and Tandem AirBikes. Here's how we found the Tandem upon arrival, and I was able to help Tariq rig up the wings as if for flight. I was disappointed to find the wing folding/unfolding procedure much closer to Wayne Ison's description than Steve Wright's. It is not something you would want to do for every flight as I had hoped. It does seem to be an awkward two-person job. I had hoped to make dollies that would enable one person to do it alone, but seeing how difficult it is for two people to get all of the pins and bolts inserted, I'm not holding out too much hope for that now. Looks like I'll have to find a full-size hangar after all.

Here's Tariq's basic 503 installation -- this is the engine the Tandem was designed for and it shows. Tariq had bad cooling problems with the fan-cooled 503 until he removed the fan and shroud and installed this Flightstar "SuperCowl" air scoop. The SuperCowl is supposed to add 2hp to the 503 when the fan is removed like this.

Here Tariq warms up his 447-equipped single-place AirBike so he can buzz around and show us how it flies. It is very maneuverable and looks like a lot of fun.


Our last stop of the trip was at the ISON Aircraft plant near Bradyville, TN. We had a lovely visit with the friendly staff and enjoyed a tour of their facility. Shown here are (L-R) Wayne Ison, Kathy Little and Skip Little. Larry Israel was not there on this day. I happened to show up just as they were about to give a package to UPS which contained my flap motor and elevator trim servo kits, so UPS got stiffed.

Over 3800 miles in 12 days! It's good to be home!