Determining C of G

[FAWGie]

I am at the stage of detemining the C of G as well as mass and balance for the Vixen. A problem that perplexed me somewhat is that the plane always landed nose heavy...

As most of you may already know, the Vixen, Bushbaby, Avid flyer and kitfox are essentially the same aircraft....So I phoned the Bushbaby expert "Boet" and had a good long chat with him about it....

The end result was that Boet found the problem and after implementing the solution, I am smiling with the CofG finally where it should be with far less weight on the nose.

Below is a picture of a typical bushbaby and one of the Vixen before we corrected the problem....

See if you can spot what my problem was...I'll let Boet explain the dynamics of the solution.... (Boet, a very BIG thank-you for your assistance and generosity of your time!!)

[Mogas]

MLG axels on the Vixen were too far back vs the centre of pressure on the wing.
Either that or you fitted the tailwheel on the wrong end

[Rudix]

You had the main wheels the wrong way round !

I am sure both take-offs and landings will be a lot better now....

Fly safe,
Rudi

[skybound®]

Studied the pictures harder. I am sure it has more to do with the fact that the Bushbaby is landing on grass whereas the Vixen is using a paved surface.


Will go with Rudix - can see the BB wheels are sweeping forward and the Vixen backwards.

I have a neat little program that helps you do the calculations and produces a professional W&B report that I used to submit to CAA.

[LarryMcG]

Will your program work for the Waiex as well?

LM

[skybound®]

Yes should do as long as you have the arms of all the main items like Pilot, Pax luggage compartment, fuel tanks etc.

[FAWGie]

Look here....
http://www.kitfoxaircraft.com/images/Ex ... %20W&B.xls

[Boet]

Thanks Steve. Glad to be of assistance. The very first BB that I fitted a nosewheel to, I was supplied those "wrong direction facing" legs. Right from the word go, I cast a bit of a beady eye on this mod, and started pestering poor Monty about the main wheels being 6" too far aft. Lacking, in those days, the tecnology to send a picture, I tried to fly the aerie in question. SCARY stuff. I would leave the ground sort of "suddenly", and PLONK down, no matter how hard I tried to make a decent arrival. Eventually the hammer dropped, and after the little oversight was rectified, the aerie still handles like a dream. The inner and outer parts of the legs were interchanged by accident. That is why I knew, and could help you.







Stupid man learn from own mistakes. Wise man learn prom stupid man`s mistakes.

[FAWGie]

Yip. all correct....The gear mains are the wrong way around.....the crazy thing is that 340 hours have been flown this way and although it was a delightful plane to fly, landing required a very experienced pilot...As Boet says, you have hardly touched the mains on mother earth and the nose plonks down...and take off was all three wheesl rotating at the same significant speed.....

It's going to be an absolute pleasure to have this matter sorted out....

My nosewheel wight before the gear was corrected was 112Kgs and now after correcting, is 62.85kgs..... That will make a HUGE difference with the groung roll and handling....

[James Bentley]

Yes, I recall flying in your Vixen after it was first built and it performed fantastically once it had left the ground. Handling during the landing phase was tricky and you are quite correct the nose wheel comes down rather abruptly once the mains have made contact with the runway.

I think Stew Allen who built the Vixens copied an incorrectly assembled Bushbaby as has been pointed out. Glad to hear it has been sorted out.

I have good memories of the time it was at Howick, watched it progress from a stack of metal tubing to a flying machine then going on a number of flyaways as a group. Found some of the photos the other day and will be happy to pass them on to you.

James
Eva's Field

[FAWGie]

Hi James,

Thanks for the feedback....As you already mentioned, she is a stunning performer once in the air and now with the C of G vs Wheels corrected, ground handling is going to be superb. I believe that Stew Allen actually built 6 of these aircraft and discontinued production as he found the cost to produce vs sales margin insufficient to make it a viable long term business. The great part is that he did some excellent improvement in this plane when compared to the Bushbaby, the most noticeable being the steerable nosewheel with gas shock. I beleive that my plane (serial number 02) had the build assisted by the first owner (Chris Bailey) from Howick. I would love some photos - will pm you my e-mail address....