HAYDEN — After two years evolving and building his 47th unique aircraft, SkiGull, Burt Rutan towed it to Bob Williams’ beach next to Honeysuckle on Hayden Lake Sunday for a series of water taxi tests that were conducted Sunday evening and Monday.
Arriving without its wings, SkiGull was launched much like a boat. Its unique trailer components consist of wheels mounted to fiberglass snug-fit sleeves that slide onto the back of the SkiGull’s two buoyant sponsons which act much like outriggers on a Hawaiian canoe. A similarly snug-fit fiberglass sleeve with an integral trailer hitch is installed on the nose and all three trailer components are ratchet webbed together using the rigidity of the aircraft as a frame.
Once launched, the wingless bird was led around the Honeysuckle docks to Williams’s beach and the wings were attached. By that time it was late in the day on Sunday and only slow speed tests were planned. Rutan briefed test seaplane pilot Glen Smith about the maneuvers to be conducted, and with the plane's nose pointed toward the lake midway between the two docks, Smith started the Rotax 912 iS engine and SkiGull immediately glided forward.
Tight turns showed a responsive water rudder and Smith turned out into the lake and increased speed beyond the four-knot idle taxi speed. Testing up to eight knots was done before it got too dark to proceed. While the yaw stability in the water was good, the pitch angle was too low. It was immediately apparent that this deficiency was large enough to require some significant modifications to the hydrodynamic components.
SkiGull was beached for the night and Rutan’s crew returned around 1 p.m. on Monday. Testing was done with some minor changes, clearly not enough to solve the problem but just to allow limited testing at higher taxi speeds.
Out on the lake with Joa Harrison at the helm of the boat — carrying Burt, Tonya, Brent Regan and Mike Kincaid plus Greg Delavan piloting his Boston Whaler with videographer Scott B, seaplane instructor Hunter Horvath and photographer Mike Satren — Smith began to apply more power. The Monday morning changes did allow taxi tests around 18 knots and crossing the chase boat wake. However, the low nose attitude produced vision-obscuring spray over the windshield. Further data was gathered to support the design of the needed hydrodynamic modifications to correct the nose-low attitude.
The SkiGull design is different than other seaplanes, in that most of the water takeoff run is done with the aircraft supported above the water on flexible water skis. The flexible skis are intended to provide shock absorption to allow it to operate on rougher water than conventional seaplanes. Before the skis can be extended, the long hull and low speed prevents pitch angle changes. The planned modifications are now aimed at forcing the nose higher for low speed taxi.
Back on Williams’ beach, the wings were folded back for trailer transport as informal debriefing began.
Rutan knows that SkiGull will need the modifications to make its water operations acceptable but is in no hurry since he now has all winter to work on SkiGull in his newly acquired hangar at Coeur d’Alene Airport/Pappy Boyington Field. After completing the development, he plans to publish a report detailing the process in order to help other seaplane designers who might also be seeking solutions for operating on rough water.
Taxiing and flying SkiGull off the hard-surface runways at KCOE is planned this fall and winter as weather and conditions permit.
Already Rutan’s crew of engineers, Regan, Harrison, Dale Martin of Lewiston, plus the input of experienced seaplane pilots, Smith, Horvath, Kincaid, Dr. Loel Fenwick of Cavanaugh Bay on Priest Lake and Dr. Rich Sugden of Jackson, Wyoming, and with fabrication suggestions by master artisans Dan Woodward and Trevor Budge will all be taken into account as the water taxi issues are resolved.
This team of multi-talented individuals plans to work together to develop and solve the water-handling issues. This methodical approach is old-hat to Rutan, who has developed 46 other new-type aircraft since 1968, and is delighted to find a local crew with so much experience and expertise.
“I was delighted with the low speed maneuverability and how easy it was to launch and recover the SkiGull. The engine started easily and ran smoothly on the Swift aviation fuel and all other systems performed as expected. As for improving the pitch trim, we have several options that we are evaluating. Overall I am very pleased with the results of our testing so far,” Rutan said.
Seaplane test pilot Glen Smith confers with SkiGull designer/builder Burt Rutan before water taxi tests on Hayden Lake.
Glen Smith accelerates SkiGull on a series of water taxi tests.