Elevator Cord Increase?

[LSaupe 123]

I will be installing an elevator trim system prior to covering.  I also had a suggestion to increase the cord length of the elevator by 4" to help with slow speed authority (especially with flaps depolyed).

 

Worth the trip and has anyone here done this mod?

[EDMO 1078]

Forgot what model you have - the early Kitfoxes and Avids were designed not to have enough elevator to break into a power-off hard stall, and did not have enough to flare without adding power - using flaperons aggravated this condition even more - the later models increased the cord of both the VS and elevator.

I added 6" to both for my nose-heavy, big flaps, Foxy along with one manual trim tab and an automatic flap tab.  Not ready for test flights yet.

EDMO

Edited 30 Nov 2014 by Ed In Missouri

[LSaupe 123]

Hi EDMO.  Its a Model III (which measures the same as a friends Model IV-1200)

 

I see Kitfox sells a larger elevator for the Lite2 (trigear) and offers it for the others.  Anyone familiar with this one?

 

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Enlarged Elevator Model 3, 4 and Lite2 (squared)  

Designed for the tri-gear version of the Kitfox Lite2, but suitable for earlier Kitfox’s this new  Elevator improves flare authority with a full flap, forward CG condition.   

 

Part #: Part #51018.201 

Edited 30 Nov 2014 by LSaupe

[EDMO 1078]

My model 1 and 2 both measured smaller than the IV-1200. I also increased the VS and Rudder to same height as the 1200 and increased the cord on both when I built the Foxy.

EDMO

[akflyer 1427]

If you get the CG back to around 17-18" there is no need to increase the elevator size.. and the plane flys faster and better all the way around.

 

[C5Engineer 1170]

I just finished this mod. Worth every penny. EZflap in response to your reply in my thread this was not a random size increase that I dreamnt up it's an exact match to the Avid MK4. The Avid and Kitfox both made the tail feathers bigger in the later models to improve handling. You will understand why John riveted extensions onto his after you fly one.

http://www.avidfoxflyers.com/index.php?/topic/3038-avid-b-model-to-mk4-elevator-upgrade/

[thebriman 69]

Joey could you do me a favor and run a measuring tape on you elevator at the largest part of the cord, so I can compare mine to your new one.  I have a trim tab on mine but its nothing like yours, and I have the same issues that you used to have.  Im thinking I have the old style elevator and someone just added a little trim tab.

[C5Engineer 1170]

Sure thing but the earliest I will be out to my hangar would be this weekend. Anyone with a MK4 working on their bird or flying this week that could take a quick measurement?

[EDMO 1078]

After reading my design book about a dozen times concerning the balance between stability and maneuverability concerning the horizontal stabilizer and elevator ratios, I started going around the airport and actually measuring the tails on certified airplanes - I don't remember all of the ratios I came up with, but the Cessna 150 was about 60% stabilizer and 40% elevator, while the Piper Cub is about 50/50.

     Another point made in my design book is that cargo planes usually have larger tailplanes for increased amounts of CG loadings.

I guess a good compromise would be about 55/45.

EDMO

Edited 2 Dec 2014 by Ed In Missouri

[marksires 484]

Did you measure any Piper Cherokee tails? ) 

Mark

[EDMO 1078]

Mark,

I was part owner of a Cherokee 140 at one time, but I don't remember measuring the tail. I was just interested in high-wing planes at the time.

My design book also states that, "high-wing airplanes need more vertical tail than low-wing".

EDMO

Edited 2 Dec 2014 by Ed In Missouri

[marksires 484]

Ed,

I was just being a smart*ss.  Cherokees have a stabilator - the entire horizontal surface moves, so your ratio would either be zero or infinity, depending on which measurement you put on the bottom.

 

Mark

[EDMO 1078]

Ha! You noticed that I forgot to take my memory pill this morning!

Good thing you didn't ask about a Cessna 177 Cardinal!!!

EDMO

[EDMO 1078]

Maybe Joey can give us measurements of both his stabilizer and elevator, for a % that flies good?

EDMO