Heavy Elevator, maybe install a spring ????

[rogerh12]

Howdy all;

With the controls in my Model 4, I noticed the elevator moves down when I let go of the stick from a neutral position. Also, it’s a lot easier to move the stick forward than back, so I am thinking this will make my controls kinda uneven in flight. Though I am still building, I don’t see elevator balancing in the plans (my zentih had a balanced elevator) and thought maybe I could install a spring to counter some of the elevator dipping force, or something like that (or maybe that's a bad idea).

Has anyone tried this, or have any other ideas?

Am I missing something in the plans?

Thanks

Roger

[War Eagle]

I use the elevator assist spring on my series 7 and it seems to work fine. I used the kit offered but the Kitfox factory.

I looked for pictures but couldn't find any at first look.

Contact the factory and they can help you out quickly.

[t j]

Roger, I wouldn't be adding stuff that is not in the plans or didn't come with the Kit. A model 4 built by the book does not need any springs on the elevator.

After it flys you will know more about if it needs some help on the elevator. If it does it is because of a foreward CG, not the weight of the elevator.

Each day you work on the plane try to save an ounce, not add ounces.

[jtpitkin06]

Roger,


The Kitfox elevator will align itself with the stab when the slipstream blows on it… just like it does for Citabrias, Super Cubs, and MD-80s.



Stick to the plans!



You’re not missing anything. Thousands of Kitfox IV’s fly very nicely without any modifications.




John Pitkin
Greenville, TX

[akflyer]

Have you ever flown a KF? I would look someone up and take a ride in a KF IV before you start modding it out and adding a pound here and there. Strip it down and keep it light. The controls are very light and well balanced in the air...

[rogerh12]

Yes, I owned the model 2 for a while, but don't remember an issue with it as far as the elevator pitch force being uneven or anything like that, mostly I remember the adverse yaw (how could I forget it !!!).

My Aerospace engineer neighbor brought up the point about uneven control forces in pitch (as undesirable), he thought it note worth and suggest a spring, and so I figured I would check with the group. Though I must say, now that I think about it, a balanced elevator seems as good an idea as a balanced Aileron, but I guess it’s not a must-have in slower aircraft (though some people believe balanced aileron are not a must-have either).

John,; the MD-80s, was that a joke, right? I thought some other older production planes could fly this way just fine, but am not much of an expert on the older plane designs and have only flown one tail dragger (my model 2). Also, I want to build my kitfox “21st century style” with all the best mods, as long as I am taking the time to build it myself, but if thousands of flying kitfox don’t have an issue with the elevator, why should I?

However, looking at the past post, so now I am confused more than before:

War-Eagle stated: “I use the elevator assist spring on my series 7 and it seems to work fine. I used the kit offered but the Kitfox factory” . Since kifox is offering this as an option, I guess I am not the only one that has been thinking about it….. Is this a model 7 option only, or a Every-Model type option?

Roger

[akarmy]

I don't know if it's made for every model or not. John could answer that. I do however know what it's like to fly a series 7 both with the spring and without. I would say that without the spring it's a bit more pitch sensitive in flight (but not by much) Also without the spring it requires more trim adjustments at different speeds and flap positions. The spring was originally intended to add up elevator when pulling flaps as I understand it. With the spring in place the elevator stays centered on the ground, without the spring the elevator drops down and the stick is pinned forward when on the ground.

Right now I'm flying without the spring, but with the series 7 trim tabs. My winter project is to fill those in, go to the movable stab design and reinstall the spring. That's the base design for the current Super Sports.

[kitfox2009]

I have a Model 5 Vixen with the controllable stabilizer and have no issues with elevator control in flight. Of course the control stick is "heavy" when on the ground either stopped or taxiing. The natural weight of the elevator pushes the stick ahead.
I have a short "bungey cord" that I clip on the passenger stick and attach to the seat back when the a/c is parked in the hanger. This prevents the stick and PTT switches from ever hitting the lower part of the panel.
I gap sealed the elevators by using 3/4" foam pipe insulation cut to fit on each side of the control surfaces. These are held in place with tape and the two surfaces just "roll" as the elevator moves. Makes a very nice fit.
There are no issues "trimming out" stick pressures with or without flaps!
Cheers
Don

[catz631]

Roger,
My model 4 is just like yours. The elevator will balance out in flight just fine. The only thing I would concider at this point in your build is to install an elevator trim tab. That,in my estimation,you will need. I got tired of holding all the back pressure on approach to landing so I sent my elevator to Highwing LLC. Lowell installed the electric trim tab system. Actuation is by a "hat" switch on the stick. This,in addition to the "bush gear" is one of the best mods I have done to my plane.
Sure you can monkey with the flaps during cruise to get control pressures off but it sure is nice to flick a switch !
Dick
Fox 4,912
Milton,Fl

[jtpitkin06]

Roger,


Including the MD-80 was not a joke. The MD-80 elevators align themselves with the slipstream just like a Kitfox.



Here's the part you may not know...


The MD-80 elevators do not have a direct connection of cables or hydraulics for primary control. You fly the airplane with trim tabs. When you pull or push on the yoke, the cables only move a small control tab on each elevator. The slipstream flowing over the control tab is what moves the elevator.


Next time you see a MD-80 taxi out, watch the elevators. Left and right elevators are independent. In a tail wind you will often have one up and one down at the same time. When the aircraft aims into the wind everything lines up and the tabs become effective.



The ailerons are controlled with tabs the same way.


When taxiing an MD-80 in strong quartering tailwind conditions, the control tabs flop up and down so one pilot must hang onto the yoke to prevent bruised knees. Taxiing an MD-80 in gusty winds is a lot like taxiing a tail-dragger... Hang onto the Yoke!!!





John Pitkin