Brian FitzGerald’s Quicksilver MXL+

Back in 2006 my Good Friend and Christian Brother Mike Rodriguez sent me a copy of the EAA Chapter 88 newsletter he was editing. At that time I had been without wings for a good number of years after selling my Quicksilver MX. In the interim I had shot a number of movies about Ultralight Flying and was still an avid Aviation fan but I wasn’t able to get airborne being wingless and overcome by gravity. Much to my surprise, amazement and extreme delight my Beautiful Wife Debra happened to look at the newsletter and out of the blue said “you should buy this”. She threw the paper across the bed and I saw she was talking about the MXL that was for sale in the newsletter. Interestingly enough I had just seen it in person during one of my continual trips to local airparks where it was hangared at Selby Field. I had not even considered buying it because for many years we had done OK paying the mortgage and keeping the kids in shoes but had really had no extra money to speak of – at least in my mind. In actuality this revelation came at a time when we were in the final stages of bringing our two children Bevin and Jack up. My business was doing pretty good and money was available to contemplate such a project. I called up Larry Hart, the owner, and we met out at Selby Field to look the MXL over. (Here’s a page on the web about Larry’s latest airplane. It lists him as female and I know he’s not so you’ll have to ask him what that’s all about…)

Larry rolled it out and took it around the patch. It flew pretty good and I was particularly interested in the fact that it had full three axis controls. The Quicksilver MX I had years prior to this was a two axis plane having only rudder and elevator controls. You could get it to maneuver OK but it had no crosswind capability and the high dihedral of the wings made it very susceptible to tipping on the ground from side gusts. It got me in the air for a few years but it was extremely rudimentary. I sold it to a guy in Ohio and was grounded for about 7 years.

Larry and I worked out a price and I bought it with the intention of making a lot of updates and modifications.

From this photo you can see some of the things that I intended to change.

1. The fabric was getting pretty old
2. The propeller was an UltraProp – not efficient.
3. The “tail cage” was the old design with limited width that mandated a small propeller
4. The reduction pulley used only 4 belts and turned too fast
5. It had no nose cone – which I like for its ability to smooth out the yaw and for general aesthetics
6. The steerable nose wheel was non-standard

Here are a few shots of the re-build process that Steve did for me:

This is not an exhaustive look at the re-build process but you should be able to see some definite upgrading. Here is a list of the things I have done in order to update and improve the plane. Some were done at the time of Steve’s Apr/May 07 re-build and some have been done since then. Because of the totality of these improvements I call it a Quicksilver MXL+.

• New Fabric
• Added “High Thrust Kit” – this is actually a series of changes including a widening of the tail geometry to allow a larger prop, substituting the pulleys for a 5 belt system at 2.6:1 ratio and updating the elevator control system to the current design
• A 64″ 2 blade PowerFin Prop (I wanted one of these for years. It is very light and stiff – made from carbon fiber)
• The nose fairing – I had flown MX’s before with and without a fairing and had definitely noticed better tracking through the air with the fairing. I also like the way it looks
• Factory elevator trim – Very important after you have been into a flight for any more than 15 minutes…
• A set of 4 high intensity Police Car LED strobe lights on the wingtips

The plane flies great and can land and take off just about anywhere. The design is a little heavy in aileron response but quick in pitch and rudder control. When I first got the plane I checked the stats on it’s Rotax engine and noticed the best torque at 5500 rpm. From this I deduced that to be the best operating level for performance. 5500 rpm would yield 53-55 mph airspeed and burn about 3.5 gallons per hour. In this last year, though, I have explored minimum flying speeds and can maintain altitude with settings as low as 4500 rpm in dead calm air although at 4650 I can hold altitude in pretty much any type of air. At 4650 rpm I get about 38 mph. The really big thing about this, though, is how much gas I save at this engine speed. I haven’t measured the gallon per hour improvement per se but I definitely notice that I have a LOT more gas left than I used to when going on the same trips as before. It’s almost like I can SELL gas when I land now. Sure, I’ve lost some airspeed but it isn’t like an ultralight is going fast anyway.I strongly suggest if you have a Quicksilver you experiment in this area.

My analysis is this: Of course an engine uses less gas at lower rpm but I think there are also important aerodynamic reasons for the improvement in fuel efficiency and thus range. Mainly it is because the airframe seems to “like” the slower 38 mph cruise. At 55 to 63 mph this airframe seems to “shudder” a little bit. Maybe that’s too strong a word but I get the feeling at those speeds that it is “pushing against” the air rather than “cutting through” the air. My visual representation of this is of trying to push a barge up a river too fast. At the “right” speed the barge will move the water around it’s flat front end and you can move it at a reasonable rate. If you try to push it too fast you just build a big, turbulent wave up in front of the barge and burn a LOT more diesel through the tug motor to yield a marginal speed increase. Ultralights in general and the Quicksilver line in particular are a lot like this. They were made for Low & Slow flying and that’s where they fly best. If you keep that in mind you will have more fun, put less wear on your motor and get more range out of your gas.

Blue Skies & Tailwinds!

Brian FitzGerald