If you've ever thought about building an ultralight, or if you have built one and are interested in how other people have done it, the following pages show my experience as I build an Aventura II seaplane. My name is Steph Bensinger; I've been flying ultralights since 1984. The Aventura is the third plane I'd built; the first one was a Teratorn Tierra (now sold by Golden Circle and called the T-Bird), and the second was a RANS S-4 Coyote.
The following information defines what ultralights are in the USA, and gives a little background on ultralight construction and powerplant choices. Or if you like, you can skip the fluff and start building!
This plane's design and construction use the same materials and design
concepts as many current ultralight designs. Except for the boat hull much
of what you see here is very similar to other popular designs from RANS (the Coyote and Airaile models), CGS (the Hawk), Flightstar, Quicksilver,
and many others.
This airframe of this kit consists of aircraft quality aluminum tubing
and fittings bolted and pop-riveted together using aircraft-grade fasteners.
The wing and control surfaces are covered with heavy-duty dacron cloth,
much like what is used with boat sails. The hull on this plane is actually
Kevlar, used instead of Fiberglas to save weight.
The engine used on this plane is a 65HP, two-cycle, two-cylinder, water-cooled
powerplant sold by Rotax (a subsidiary
of Bombardier) of Austria. It incorporates two Bing slide-type carburetors,
a dual CDI ignition system (two spark plugs per cylinder), and a gear reduction
system at a ratio of 2.58:1 to drive the prop. This engine has a pull starter,
though electric starters can be fitted.
Does Bombardier sound familiar? Originally these engines were designed to
drive water pumps, then were redesigned for snowmobiles, and lately are
being used in personal watercraft. The engine used here has been specifically
designed by Rotax for use in light aircraft. They have a very high power-to-weight
ratio, mostly due to the fact that they produce power on every piston stroke,
as opposed to four-cycle engines which produce power on every other stroke.
There has always been concern about the reliability of two-cycle engines because they work harder than a comparable four-cycle. However, with proper maintenance they can be very reliable. This means you have to either be knowledgeable about your engine, or have the money to pay somebody else to maintain it. These engines do not have to be babied, but they do need to be properly maintained, or you will have an engine failure. Of course, that applies to any engine!