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A new Aero Sled


Olav Aaen
Back in the summer of 1978 Polaris decided to exit the Sno-Pro race circuit, much because of a bad accident that claimed the life of team member Jerry Bunke. The 1977 and ’78 season had been extremely successful for Polaris and its “Midnight Blue Express” with almost total dominance in the 250, 340 and 440cc classes. The new IFS sleds had annihilated the competition and there was not much left to prove.

Undoubtedly pressured by corporate lawyers and other concerned management personnel, corporate decision makers decided that a new race program would support privateer racers with the 1978 factory machines. However, this was not very popular with the racing department, which felt that privateers would lack the resources to compete against the onslaught from very determined Arctic Cat, Scorpion and Ski-Doo factory teams.

Reluctantly, the race shop started choosing the privateer teams, and our Aaen team was allotted a 340 RXL that had been raced by Steve Thorson and a 440 triple RXL that had been Brad Hulings race sled. In the meantime, Thorsen and Hulings were picked up by Arctic Cat and moved to the “Scorpion Squad.” We were lucky enough to nab Tim Bender. Bender had shown great form on Yamahas in 1977 and ’78, but Yamaha backed out for the ’79 season. With Tim as our main rider we managed to secure sponsorship from Amsoil, putting us in position to compete on the full Sno-Pro schedule.

Glory days – From left is the Aaen Performance test platform mounted to Tim Bender’s pickup truck bed, Tim racing the Aero sled during the 1979 season at Alexandria (Minn.), and the two Amsoil sponsored sleds sitting in the Alexandria track’s pit area.
Aero beginnings
Tim moved to Kenosha to be near our shop and work on the sleds full time. We quickly realized that we probably would not be able to gain much more power by tuning the engines, since these were full blown factory racers. To find a possible advantage against the other factory teams we felt that using aerodynamic downforce to improve handling was promising.

Racecars were going through dramatic handling improvements by using aerodynamic downforce devices like spoilers and wings, so why not try it on a race sled?

There are pitfalls in the aero game though. If you get your shapes or downforce pressures out of balance you could end up with an ill handling disaster. We needed some way of engineering an efficient and well balanced sled, and the traditional approach would be to use a wind tunnel. As we checked into rental prices for the few U.S. tunnels available, we quickly realized renting a wind tunnel would drain our race budget in a couple of days, so it was out of the question.

We thought, if we couldn’t move the air around the sled, maybe we could move the sled through the air. We knew that rocket designers used special sleds on rails to measure the forces on the rocket shapes as they were propelled up to speed. The answer was Tim’s pickup. By building a platform on top of his truck and driving it down a highway we could measure downforce in front, in back and the drag forces on the sled by placing it on a floating platform with scales in strategic locations.

The “flying platform” worked well and gave us good, consistent force readings. We managed to increase downforce both in front and back, and also reduce drag by using a side panel going all the way to the back of the sled on the right side.

Our first races with the Aero saw some problems as we were forced to install stiffer springs to counter the extra downforce and then strengthen the frame as it started to bend under the increased load. At the Wausau, Wis., race, Tim went through the turns without shutting off the throttle due to the extra downforce, then he went on to win the 440 mod class at Peterborough.

The largest advantage was on large flat tracks with sweeping corners, as the higher speeds also gave more downforce. An unexpected benefit came from the side plate, which made it possible to enter a corner at high speed without losing the rear, because the plate acted much as the large “fences” on the wings of Outlaw Sprint cars that raced on dirt.

The Aero sled was competitive and held up the Polaris colors against the onslaught of the other factories. Unfortunately, as racers often do, we sold the 440 sled after a couple of seasons, and the new owner decided to restore it to the original Polaris 440 “Midnight Blue Express” livery as he felt that might be worth more money in the future, since it had been Brad Hulings factory racer.

The 340 Aero sled was sold to a racer in Canada, and I have no idea what happened to it. As a result, neither of the two original Aero sleds can be located.
Fabricating – Aaen Performance’s Mark Jacox works to refabricate the Aero sled’s body and tail.
Remaking an Aero
As the years went by many people remembered the sleds, and other factories, including Scorpion and Ski-Doo incorporated some of the aero sleds’ features into their machines. With recent heightened interest in vintage racing sleds I have often been asked if a new aero sled could be recreated, and my answer was always that if someone had an RXL chassis I still had one original spare hood left from the race team, but the rest was all made in aluminum and would take time to fabricate.

Few people are willing to redo an original Polaris RXL these days, because of their high value just in their original shape, until Brad Warning came along that is. Brad is a heavy vintage enthusiast, who has recreated Kawasaki IFS Sno-Pro sleds and built the “Radical Radial” featured in AmSnow’s December 2009 issue.

Brad happened to have an RXL chassis, and after making sure I had no more hoods or forms to make them in, he was willing to finance the project as long as he had the only replica. Brad understands the effort involved with a project like this, and was willing to spend the money necessary to get the job done right. We started working on the project last March, and the goal was to finish it in time for the Hall of Fame Vintage Roundup in St. Germain, Wis., on Memorial Day.

The fabrication included constructing the tail section wing and side panel from aluminum sheets, a new radiator housing matching the hood, reinforcing suspension mountings and trimming the hood and mounting it in place. With only pictures to go by it took awhile to mockup the tail by scaling it up from side views, but after several cardboard mockups, we were happy to be close to the original size and shape.
Like old times – The paint job on this recreation of the slick Aero sled from the late 1970s shows great attention to detail. It’s a virtual dead ringer for the
Fabrication was more involved than we had thought, and this always seems to happen as we run into small design details that have to be solved all over again.

Recreating the Aero sled answered some frequently asked questions, like how much weight did the rear wing and side panel add. The answer is 10 lbs. for the wing and 5 lbs. for the side panel. On the other hand the hood was 5 lbs. lighter leaving a weight penalty of 10 lbs. Yet Tim gained several hundred pounds of downforce to aid the sled’s handling.

Unfortunately the sled remake project dragged on a little longer than planned and it was a very anxious Brad that took the sled with him to finish painting, decaling and construction of the aerodynamically shaped seat with only two weeks to go before the Hall of Fame Roundup last May.

With the paint barely dry he showed up on Friday night of the Memorial Day weekend with an absolutely stunning finish, and the sled drew a lot of attention as one of the show’s main attractions. A lot of people who had seen the original Aero sled in action shared their memories. One recalled Tim going wide open and passing sleds through the turns at Wausau to the roar of an excited crowd. Tim’s original matching race leathers were donated to the cause by Brad’s friend John Bertolino, who has a large collection of Tim’s race sleds and the leathers are now being restored to original condition.

Perhaps the most satisfying encounter was when one of the old Ski-Doo race team members came over and divulged that the Aero sled had caused a lot of concern at the Ski-Doo factory, and as a result they had increased the engine development program to try and beat it with sheer power.

Tim kept racing with us for many years. We dropped out of Formula One when the twin tracks took over and concentrated on the Formula Three program where Tim ended up winning four straight Eagle River World Championships on Yamahas. He is now back with Polaris, running the Hentgess Racing Team and tuning T.J. Gulla and Tim’s son Bret Bender’s sleds for the ISOC Snocross Pro circuit.

The Aero sled replica is now displayed in the main showroom at the Snowmobile Hall of Fame in St. Germain, Wis., where it can be studied in detail by interested and aspiring racers and builders.

Read more online about the Aero sled. Check out Olav’s feature on sled aerodynamics in the November 2008 issue.
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