profiled tail

[Eric]

I have a KF 3 with the flat(non profiled tail)
Does it make a big difference if I make the stabilizer and tailfin profiled like the newer ones?
It is than also easyer to reduce the gaps between the fin and rudder>
If it is does anyone have the drawings for the ribs/

[jtpitkin06]

Eric,


Contact the Kitfox factory. They may be able to supply you with a tail speed kit and set of ribs and the fairings for your model 3.


John Pitkin
Grreenville, Texas

[P Morel]

Just bought the rib pattern from Kitfox and they were pretty cheap. The rib kit was not available however, John was able to have a copy of the rib pattern sent to me for around $15 plus shipping. I also bought the fiberglass rudder leading edge and the vertical trailing edge from them. The ribs can be cut from from thin plywood from a hobby shop. I cut the patterns out and used 3M spray contact cement to temporarily stick them to the plywood and cut them out on a band saw. The pattern includes the horizontal stab and elevator ribs too. I finished laying everything up today and it really makes a world of difference. It was well worth the the time and $$$.

[cap01]

if i were going to do all the work of installing ribs , i would enlarge the fin and rudder and make a speedster or model IV 1200 tail out of it .

[Dave S]

Eric & Jean-Francois,

I will offer my opinions on your questions - others may have different opinions.

1) Opinion # 1 - as far as the effect on speed/drag - I don't have any empirical data that would suggest there is a major difference. That would take flight testing of aircraft identical in all respects except for the tail. Theoretically, a control surface which provides the smoothest airflow over the break of the leading edge all the way to the trailing edge so as to minimize any eddy currents should decrease drag - how much - no clue here.

2) Opinion # 2 - in my opinion - after flying series 7 kitfoxes of each design (airfoiled and non-airfoiled vert.stab. & rudder) the rudder with the non-airfoiled tail feels like it has a slight dead spot when using the rudder - that is - the plane doesn't want to quite center itself with the world without a some opposite rudder following a roll out of a turn. The two do feel different and I prefer the airfoiled tail with it's response to control inputs- I just don't know if I am explaining it well enough because it is a subjective thing. I am not certain what to attribute this to - thinking it is either a matter of how the air breaks and flows around the tail or else the slab sided tail is a little more prone to fabric deformation from aerodynamic pressure while the airfoiled tail pretty much means the fabric will hold its shape more like a rigid hard surface tail. Analogous situation - the extra false ribs on the wing improve the wing by maintaining the correct profile - possible the airfoiled tail helps in the same way by keeping the aerodynamic pressures from deforming the surface as much when the rudder is used.

Hope that helps some - just a couple ideas - maybe others have some experiences/opinions they can share.

Sincerely,

Dave S

KF7 Trigear
912ULS Warp
Airfoiled Tail





Sincerely,

Dave

[Jfquebec]

Thank's Dave ,it's help for sure,i have a kitfox 4 1200 project with normal crontrol surface ,so i think i will check for speedster tail if i can modiffy it....



Jf