FMS Typhoon CoG

[Neil James]

Hi

just finishing an FMS 100mm Typhoon ARTF, (what little finishing it needed!) and I'm trying to balance it. The instruction sheet says the CoG should be 40/45mm behind the LE but even with a larger than suggested battery mine is nowhere near that. I've stuck 2oz of lead inside the nose so far and it is still a bit rearward.

To me the suggested position looks a bit far forward but I'm sure someone on here will know for sure Any suggestions?

[Broken Prop]

Hi Neil

As a general guide around 27% of the chord should be good starting point for the CG of most models so if that coincides with the FMS instructions stick to them.

The Typhoon (in common with most warbirds) has a short nose moment. This is because in real life they were hanging a 1 ton engine up front and needed to keep the nose short to balance the aircraft. We do not have heavy engines in our models and so this type of aircraft always needs weight up front to compensate.

I am not familiiar with the model, but can you move the battery forward a little? That would be preferential to adding ballast, which increases the wing loading and raises the stall speed.

Good luck!

Pete

Edited By Broken Prop on 11/09/2017 21:26:52

[Denis Watkins]

I can only look at the manual Neil, but that C of G does look too far forward, but the writers are the boffs.

With scale estimates and calculation from diagrams, I make it 54mm from the leading edge.

My advice is to hang on for more advice from FMS owners.

[Neil James]

Thanks guys, I calculated a position 60mm from the LE which looks more realistic based on experience, but yes, I'd like to here from someone who's flown it before I try! At least too far forward is better than too far back.

[Neil James]

Found some more information about this on rcgroups: it turns out that the 60mm location I calculated is the preferred position by those who've flown it and it seems to fly well set up like that. Haven't been able to fly mine yet but it's taken 70g of lead so far and is still tail heavy, according to the instructions! I'm now at 50mm so I think I'll test fly it there and see what happens. Just need the wind to drop now!

[Neil James]

Update: finally managed to get the first flight in! In the end I compromised & set the CoG to a halfway position of 50mm. The model shot off the ground in what seemed like a very small distance and flew without any problems apart from needing a lot of left aileron trim. Rolls were pretty axial and dropping flaps or gear didn’t need any compensation. Unfortunately the wind picked up & got gusty during the day which made the last landing rather untidy! Fortunately it hit the grass rather than the tarmac and the only damage was the loss of two cannon barrels - I knew they would be a problem!

Of course I took a snap before the first flight 😏