Thunder Tiger 54. Which size properller would you recommend?

[David Davis]

I am entered in La Coupe Des Barons in June, Covid 19 permitting. This is an event for an iconic French three channel trainer which looks vaguely like a WW1 monoplane fighter. This is a picture of our club's entry in 2019; the 2020 event was cancelled.

The event consists of a concours d'elegance where your model is judged statically followed by four flying rounds. The first round is known as "casse baguettes" or " break the sticks." 70 balsa wood sticks are pushed into the ground, ten rows of seven, each stick two metres apart which is bigger than the wingspan of a Baron. All you have to do is break or touch a stick and you get points for any stick you touch or knock over; you have a judge supplied by the organising club standing behind you keeping score. Of course you have to fly less than one metre above the ground to hit a stick and any inaccuracy in your flying results in an accident. After five minutes of attempting to knock over the sticks, the survivors of the first group are called in and the second group gets its turn.

The second round is a pylon race between two pylons, then there's a break for a typical French four-course lunch washed down with a little vin rouge then the competition resumes with the third round in which a trainer slowly pulls a crepe paper streamer and contestants have to cut it with their propellers. Of course with up to eleven aircraft in the same airspace at the same time the chances of a collision are great! Finally there's the limbo round in which models have to fly through a "goalpost" ten metres wide by four metres high. It sounds easy but the goalpost is several metres away and not square on to the pilots. Suffice it to say that the attrition rate is enormous and it doesn’t do to be too fond of your model! The attached video from 2017 gives you some idea of what goes on.

**LINK**

Basically there are two low-speed events and two high-speed events. If you can fly quickly and accurately you're in with a chance of winning, but I can't!

This year my Baron will be powered by a Thunder Tiger 54 fourstroke. Recommended prop sizes vary from an 11x5 to an 11x10.

Would there be any merit in fitting a low pitch prop for the slow events, say a 13x4, and a coarse pitch prop for the speed events?

[Martin Harris - Moderator]

Sounds like an excellent idea. I'd bung on some different props and give 'em a go, any local regulations permitting.

[Jon H]

i would try 13x5 for slow and perhaps 12x6 for fast? the problem you have is the model itself does not lend itself to breaking the sound barrier so an 11x7 may be slower than the 12x6 due to the loss of thrust and the high drag.

Truthfully, i would probably fit a 12x6 and just use the throttle as needed for the desired result.

[David Davis 2]

I think I'll follow your advice Jon, saves adjusting the engine between rounds.