Wobbly prop?

I suppose I'm getting itchy fingers. It's 15 months since I finished building JONL and I'm starting to think how I might get my hands dirty again making a few improvements.

One thought that recurs often is the idea of fitting a variable pitch propeller to my steed. This, it is alleged, would transform the aircraft, providing even shorter take off runs and anywhere between 5 and 20 knots of additional speed in the cruise, whilst simultaneously reducing fuel consumption. Quite a feat if all that can be achieved in one go!

The principle is simple enough: at slow speeds a fixed pitch propeller is set too coarse and as a result the engine cannot reach maximum revs and thus, maximum power. By having a finer pitch this problem is fixed and take off becomes a more efficient affair. Conversely, in the cruise the prop pitch needs to be much more coarse so the propeller takes a bigger slice of air per revolution at a given engine speed, resulting in higher air speed. The problem is that these requirements are mutually inconsistent, so a compromise is necessary with a fixed pitch propeller. And compromises aren't good in aviation.

Enter the in-flight variable pitch propeller. This can be adjusted for fine pitch during take off and coarse pitch in the cruise. The propeller and engine can therefore work together to provide the best combination of power and thrust for any given situation. The system is variously called variable pitch, constant speed or, more prosaically, wobbly prop. And I want one!

There are a couple of options that are approved for fitting to the Sportcruiser. One is electrically driven, with a pitch control motor in the propeller spinner, connected via slip rings to the pitch controller. The other variant is perhaps nicer. Here the propeller pitch is driven via hydraulics, with the control motor mounted somewhere convenient, such as the fire wall.

The electrical system is simpler and cheaper but it is also heavier and the weight is in the wrong place, right at the front of the aircraft, which is a nuisance for weight and balance considerations. The hydraulic system has fewer moving parts and much less weight at the nose of the aircraft but is the better part of twice the price.

It's a difficult decision and I'm not planning to rush into it but I am thinking about it quite hard. I reckon there is every chance that this will be a project for when the summer flying season is over.