Mod. III Control Modification

[Caballo]

I am contemplating installing the Kitfox Mod. IV, flaperon / flap control, conversion kit on the Kitfox, Mod.III (#1050) that I have recently resumed the building process on.

Has anyone installed this kit on their Mod.III to date? Is there a noticeable difference in aircraft control, between the two systems? Or was this possibly a safety option, with no noticeable difference in control?

At this stage, I am still sifting through the service bulletins and letters to see what componants I will need to order and replace, before actual building begins this go around.

[Slyfox]

I have the flaperon control on my kitfox. To be honest, I never use the flaps. Does this just give you the ability to have flaps? Like I said, I never use flaps, I have many other options for landing, like slipping, and full rudder with wings level to slow er down for landing. I like the lazy approach when landing the plane. Pull the power and land. If I need to slow the plane, I use slips, full rudder wings level just off the runway, or just bank er good and pull on the elevator on the base to final. I know I'm a nut.

[cap01]

the mod kit is listed in the kitfox catalog at the kitfox website . not much of a discription , youll have to call them for more info and see if it worth the money .

[t j]

Caballo, in a nut shell, the Model 4 flaperon control system has a 2:1 differential designed in. In a bank the travel on the aileron going up goes twice as far as the aileron going down. It counter acts adverse yaw and also helps maintain aileron authority when using flaps.

I think there is no differential in the Model 3 aileron system which means you need to use more rudder to coordinate the turn.

Tom Jones
Classic 4 builder

[Slyfox]

In that case, I would put the new design on it.

[Caballo]

Thanks, these replies help a lot. When I get a complete list of componants I have to purchase, per the service bulletins and letters, I will finalize my decision on this.
I like the additional control described by Tom. I am assuming this will make the Mod. III flaperon controls operate a little more like the citabria and super cub ailerons I am used to flying? Add a little rudder to initiate the turn then neutralize the rudder pedals once the turn has been established.

Mark
KitfoxIII (#1050)

[Mnflyer]

Hi Mark, the model 4 flapron mixer control system provides differential aileron which will reduce the adverse yaw, which for me is a non issue you just learn to use the rudder. The model 3 flaperon control does limit flaps to about 20 degrees which is more than enough for the Kitfox, one thing to consider if you intend to fold the wings any amount with the model 3 system there is no need to disconnect any of the control rods but with the model 4 system you have to disconnect the control rods to fold the wings. The model 3 benefits much more from enlarging the rudder/vertical fin area this will do more for flt characteristics than the differential aileron will ever do. I have a model 3 and have flown it more than 670 hrs and it is a good flying plane like I posted the best mod I did to it was to add a dorsal fin and increase the vertical fin area.

[DesertFox4]

I admit to loving the way the model 3 flies. I did not care so much for the flapperon control mixer though. Lots more parts(strange shaped aluminum blocks) that could develop wear. Not a great trade off for having to unhook two rods to fold wings on the model 4 on up. Wear is always something to look for on any flight control system. The model 4 system seems much less prone to wear.


Again, as our Kitfox fleet ages we need to be vigilant for maintenance concerns on our higher time aircraft. Let's keep that great Kitfox safety record intact and share information that is vital to that goal.

[Mnflyer]

Hi Steve, you are absolutely right in that the model 3 system has many joints and wear points and simpler is always better in my book, I guess if I were building a model 3 I would probably go with the model for system designers figure out way back in the 30's that differential aileron movement was a good thing, and since you have flown both the model 3 & 4 systems you know about both, and for me disconnecting the controls would be a non issue also as I only fold the wing every couple of years at the most. I really think that the model 4 was is an excellent plane the best of the original Kitfox line.

On my plane I replaced the main pivot bolts in the mixer/control and went from plain AN bolts to MS or AN close Tolerance bolts these bolts are much stronger and are close tolerance thus reducing wear plus I coat them with grease and check them every 300 hrs or so.

[Hallgrimur]

To what purpose would you do this mod in the first place..?? What do you gain. Some of the Kitfox flyers commenting on this, I notice, never even use the flaperons.. So there is no experience there.
I for one use them often on my older model for shortfield landings, to lower a bit the stalling speed, but mostly to increase visibility (lower the nose) on final appr. I need some 30 - 50 meters to land with or without the flaperons. Final appr. speed is then close to stalling speed. The problem with the older models like mine, with the smaller tail section is the increased control movements needed. > My advice, do something else to make your plane more safe or to have more fun flying.. To be honest!

regards
Hallgrimur

[SkyPirate]

Hallgrimur,.the advantage of the mod is that your aeleron "mode" of the flaperon system is at a ratio of 2 to 1,..this reduces yaw induced by the aeleron input,.so less rudder is needed,.the flap system is still effective and better because now with flaps (using the mod) you gain more control with your surfaces ,..less control input get's more results.
the model 3 fly's great just the way it is,..just as the model 2 does as well,..but they do have allot of moving parts in the flaperon mechanism.
changing the mixture on the plane will not make it unsafe,..,.now if you are use to flying it with one control mixture set up and then change it ,..it will be like flying a different plane ,..and it will be a good thing or bad ,..depending on the indiviuals desire in handling that motivated changing the control mixer set up.
I know some say ..if it isn't broke ,..don't fix it but some also say use the "Kiss" method,..keep it simple sir this mod is the simpler of the 2

[Hallgrimur]

I am sure you are right in every way Chase. I am not trying to dispute that.
I for one have learned a lot by reading your comments on the Kitfox and also from Steve, the Slyfox. You both are to be admired for your willingness to shear with all of us Kitfox flyers your experience and studies.
What I mean regarding modification of the flaperons, or what I am trying to say, is it worth it, and then it depend on how the individual is operating the plane and the need for manuvearing at a very slow speed etc..
The Kitfox is a fantastic plane and very forgiving to the pilot
Kind regards
hallgrimur

[SkyPirate]

well thank you Hallgrimur ,.. you nail it when you said ..it depends on the individual ,..and that is also what makes the kitfox unique ..it is a very versatile aircraft that meets many needs,..with upgrades/mods available,.model 3 mixture mod ..spring aluminum gear,.trike or tail dragger.airfoiled tail or not,..one piece turtle decks,.etc
all mod's that have bled down from a newer version that enhance the roots of all kitfox aircraft

[Slyfox]

I fly my model 4 a lot. Maybe not so much last year. Only 146hrs. But I have flown it over 1300hrs now. I have no wear on my controls. I don't just fly point a to b either. I'm pretty tough on the little bird. I like yank and banks and other things She is a tough bird and I wouldn't think anything adverse about the controlls on the model 4, they are real tough.

[Slyfox]

Aw shucks. I just like to hear that people are enjoying their kitfox's. If I can put in a few tips, well, maybe the family will grow bigger and bigger. Makes for more fun for all of us.

[Caballo]

GB - I do not see a modification offered in the kitfox catalog for adding a dorsal fin and increasing the vertical fina area? Is this modificatoin available at this time?

One response I've gotten on the Mod.III flaperon control modification to a Mod.IV control system was that they thought that I needed to change from a Mod.III wing to a Mod. IV wing also, in order to complete this modification? This is not what I understand from the catalog however.

[Caballo]

John at Kitfox cleared up my confusion on the Mod.III to Mod.IV flaperon control modification (PN-19065.000). He said, "There are a couple of brackets that get bonded into the fuselage to mount the mixer assembly, new mixer assembly, flaperon push-pull tubes, Control column, flap handle, bellcranks, push-pull tubes. Basically you are replacing your flaperon control system."

I am still curious about the possibility of adding a dorsal fin and increasing the area of my dorsal fin through a modification, like GB mentioned inhis reply below.Great comments.

Really does help to understand prior to ordering something I may not want or need. - ThanksMarkMod.III (#1050) Kitfox

[SkyPirate]

To add a dorsal fin in front of the vertical stabilzer..it should have been done prior to covering ,..it's made from aircraft grade aluminum,.. once formed you have 3 choices ,,don't put anything inside of the formed area,..or cut and epoxy some foam into the void to hold the shape ..a couple 1 inch wide sections evenly spaced ,.or make some aluminum ribs to put inside of the fin ,..this can also be epoxied so no rivets showing.I say this ..because dorsal fins tend to attract hands for moving the tail sideways,..it will keep the shape more rigid with something in the void to hold it from beer canning,..

you can add one after it's covered ,..after making the fin ..set it in place draw a line where it meets the top of the tail deck and tail,..remove it and use MEK to take the finish back to the fabric ..install your fin then cover the seams or the whole fin with fabric,..bring the new section of fabric back to painted condition,.. poly brush etc,..


Chase

[Caballo]

Are there any instructions for this dorsal fin modification that you are aware of?

I am leaning toward the flaperon control mod, since I have not completed the Mod.III control system to date or covered the aircraft (see attached).
Does anyone know of a builder who has actually installed the flaperon (Mod.IV) control system on a Mod.III Kitfox?

[SkyPirate]

No instructions to my knowledge ,..I'm thinking it would be considered a personal ad on item,.owners choice.

myself if I were to add a dorsal fin I would go vertical 1/3rd the vertical stab height and forward 2 inches of the cross tube in front of the vertical stab.

because the dorsal fin and the airframe are 2 different materials I would prime the interior of the fin where it meets the fuselage.

you can tape a piece of string from the vertical stab to a forward position to find what catch's your eye as the right angles or connect points ..hope this helps

Chase

[Mnflyer]

Hi Mark, there is no factory mod for increasing the tail area, go to my album and you can see the dorsal fin and the vertical fin enlargement that I did. Adding a dorsal fin is very simple what I did was use 1/2" heavy wall alum tubing fabricated an attach bracket at the forward end and riveted it to the flat plate bracket for the radio ant aft of the turtle deck the aft end I used a 5" peice of square U channel that fit over the 1/2" alum tube cut the top part of the U channel out to slip over the vertical fin tubing and bolted it on the aft side of the tube (I do NOT drill into any of the structural tubing so as not to weaken them). I then just covered the fuselage as you normally would and you have a small dorsal fin. With the heavy walled tube it will take any loads execpt directly pushing on it for handling of the plane. As for the vertical fin area I used 0.020" thick alum made a forming jig to bend a nice rounded leading edge I added 2" of area to the fin, attached the top using a steel channel that fit over the top of the fin tubing used aircraft CherryMax rivets to attach the channel to the alum addition and did have to drill a hole in the tube at attach the channel there, at the bottom I just went with a screw thur the fin addition and the gap seal I had fabricated before just under the covered fin area ahead of the stablizer attach bracket. Like I posted before this improved the flt very nicely and it was one of the best mods I have made other than installing the HKS vs the 582.

[Caballo]

Thanks GB and Chase, these posts helped me understand what is going on with this mod. This really helps. I like it. I am defintely going to install this mod.

"Git 'er done!!!"

Mark
Mod.III (#1050) Kitfox

Please, also let me know if any of you run across another builder who has installed the (PN-#19065.000) flaperon flight control system modification (Mod.IV controls on Mod.III wings) on their Mod.III Kitfox.

[SkyPirate]

glad I could help Mark

Chase