Kitfox 4 fin size?

[firesteve]

I'm looking to modify my Kitfox 2 fin so it is the same size as the later variants. Can anyone help with dimensions as my LAA inspector is insisting we need them and we can't 'guesstimate' (he's no fun!)

Also while the aircraft is stripped I would like to weld in the forward landing gear bracket that Grove utilize for their landing gear. I have been looking and some kitfox 2's have them and some do not? I need the dimension from the other forward bracket if anyone has it?

I subscribe to quite a few other forums but I have to say this is by far the most helpful and congenial of the lot. Well done everybody:D

Kind regards,
Steve

[SkySteve]

Steve,
I did the same mods to my plane. I don't have the dimensions, but what I did was take a large piece of cardboard and traced around a model IV speedster vertical stabilizer. My A&P used that as a template to reconfigure the vertical stabilizer on my plane. I do remember it added 10 inches to the height of my VS.

You can purchase the nose wheel kit from Kitfox Aircraft. It comes with instructions on how to install/weld in place. One of the main parts of the kit is an "L" shaped plate to weld to the front and bottom of the frame at the firewall. This plate will also help strengthen the structure.

EDIT: I just reread your post. I may have misunderstood what you are doing. It appears you are not adding a nose wheel.

[firesteve]

Hi Steve,

I would love to add a nose wheel, I have been looking at your plane for inspiration:)

The trouble I have is weight! here in the UK the CAA are very strict with regards to maximum weight limits, rightly so I suppose.
Because I have a Jab fitted it greatly reduces my load capability to such an extent that if I have two fully grown adults it only leaves me 5 liters of fuel!!!

I'm trying to save weight wherever I can buy getting rid or re positioning items as necessary, I have just removed a 6.2lb counter weight from the tail wheel!

I'm also looking into any mods to the fuselage I can do to increase my permitted weight, beef up front carry through tube etc..
If I can increase the current permitted weight from 950lb/ 432kg all up, to 450kg which is the max for a microlight in the UK I would be more than happy:D

I'll let you know how I get on. Cheers Steve.
Kind regards,

Steve

[David47]

Steve, have you asked Kitfox directly ?. John McBean is contactable via email and he may be able to suggest something. The model you have is most likely before his time there but you never know.

[avidflyer]

Here are sizes and pictures of the Kitfox 4 classic rudder. Top of rudder just after the radius is 12 1/4" Bottom of rudder is 18" just before the start of the radius. Height is 53" JImChuk

[SkySteve]

Good info, Jim. In fact, when I added height to my vertical stab I also added a model IV rudder. So, Steve, one idea is to order a model IV rudder (you'll need to add height to your rudder anyway, and the model IV rudder provides more rudder authority. then just make your Vert Stab fit the new rudder.

[firesteve]

Excellent replies gents, I'll get a mk4 rudder on order as it makes perfect sense to make the VS fit accordingly.

Cheers for you help guys :)

[avidflyer]

You do realize that the hinges are different from a Kitfox 2 to a 4. JImChuk

[SkySteve]

You do realize that the hinges are different from a Kitfox 2 to a 4. JImChuk

Cut and Paste (I mean, cut and weld) Actually, If I remember right, only the top hinge was different (if I remember right).

[avidflyer]

No, they are all different. JImChuk

[SkySteve]

Jim,
Thanks for the correction.

[tommg13780]

Steve,

I did the rudder mod to a model 2 by purchasing a model 4 rudder from Kitfox aircraft and modifying it to fit the existing model 2 hinges. Also we went with a balanced (Cub style) kind of birds beak which confines the work area to the rudder only. The existing model 2 rudder was cannibalized to get the hinges transplanted and the birds beak over top of the vertical fin.

This modification corrected the Yaw neutral characteristic and improved rudder authority by a large margin. Major components were the new rudder at approximately $400 and about $400 in professional tig welding. Cover and paint was done by myself and considered incidental cost. Well worth the expense and effort.

[avidflyer]

There is a guy on the AvidFoxFlyers site that just enlarged the rudder on his Kitfox 3. Really doesn't look like that much work if one has access to someone who can weld and bend tubing. He probably had about $50-$60 worth of new tubing in this remodel. I do like the idea of the birds beak over the top of the verticle stabilizer the way you show Tom. For another $20-$25 or so of tubing, that could be added on to the original. JImChuk

[David47]

The "birds beak" you refer to is an aerodynamic horn balance. As the added area is forward of the rudder hinge line it will change the characteristics of the rudder hinge moments, which is reflected in the pilot forces you apply. In short, when you add a horn balance, it will change the rudder forces you need to apply for the same rudder angle. From memory, adding a horn will lower the rudder forces required for the same rudder angle.

[dholly]

Jim did not add the balanced rudder design because the height of his plane on his trailer would have been too tall for his storage building opening. He also could not lower the tail support on the trailer to provide extra clearance without the wing tips interfering with his tow vehicle. In short, to add a taller vertical stab/rudder, he would have been forced to make costly alterations to his building or trailer. Hopefully, the extra chord alone will provide a significant improvement in slow flight rudder authority and I anxiously await his pirep.

The other comments raised on his AFF forum build thread regarding this mod is that you may need to 1.) reposition flaperon counter balance weights to prevent interference with wing folding and 2.) strengthen the V.S. side rudder post to better handle the increased forces the larger rudder imparts. One member who enlarged his rudder slipped a reinforcing tube into his rudder post.

[firesteve]

Cheers guys, I must admit I had no idea that the hinge design had been changed!

[TJay]

I do think the hinges that Jim posted are only for the 1200lbs Model If you find a Kitfox 4 1050 rudder they should match the early birds,

[Av8r3400]

The 1050 rudder is shorter than the 1200 (with the goofy hinges).

That was the first mod I did to the Mangy was to cut off those rod-end style hinges.

[av8rps]

Might just be me, but I kind of like the earlier, shorter rudder style of the Model 4 -1050 and the earlier model 1-3's. I'm sure the taller fin will handle slightly better than the shorter verical, but after flying a bunch of these type planes over the years, it seems they all fly a bit different anyhow. So I just adjust myself to the particular flight characteristcs (which also keeps my feet from getting lazy...). Plus, if you are concerned about weight and an inspector ok'ing changes I'd just stick with what it came with. Again, that's just my opinion. But I think all the early airplanes flew pretty well, albeit differently than later models. Although there is more to the improvements in later models than just the change to the vertical. The control system mixers are hugely different, which provided differential to ailerons in the Model 4, which in my opinion is probably the biggest change between models.

Oh, and for a bit of trivia, did you know the vertical on early Kitfoxes was styled from a P-51 tail? Yup, just look at the profile of the early Kitfoxes and you'll see it. So if you change over to the newer tail you will lose that fun little bit of early Kitfox identity / history.

Plus, if you keep the standard vertical you'll end up being a better pilot :)

Disclaimer / Warning: FREE INTERNET ADVICE

[DesertFox4]

" Oh, and for a bit of trivia, did you know the vertical on early Kitfoxes was styled from a P-51 tail."

For a little bit more Kitfox trivia, so was the 7 Super Sport's vertical stabilizer.

[jrevens]

...

Plus, if you keep the standard vertical you'll end up being a better pilot :) ...



Gee, if I'd known that I would have decreased the size of the one on my 7 SS ! :rolleyes:

...Just kiddin' you, Paul!

[HighWing]

Might just be me, but I kind of like the earlier, shorter rudder style of the Model 4 -1050 and the earlier model 1-3's...

I learned long ago and will be taking advantage of this once again soon. With the shorter vertical, it is much easier sharing hangar space as the vertical fin will easily fit under the wing of a second airplane. I am helping a friend with some mods and will have his Mk 4 Avid side by side with my Kitfox in my hangar when we leave town this weekend.

[t j]

" Oh, and for a bit of trivia, did you know the vertical on early Kitfoxes was styled from a P-51 tail."

For a little bit more Kitfox trivia, so was the 7 Super Sport's vertical stabilizer.

I didn't know that but an old B-17 Crewman in my neighborhood looked at my Model 4 and said, "It's got a tail kike a P-51".

[David47]

" Oh, and for a bit of trivia, did you know the vertical on early Kitfoxes was styled from a P-51 tail."

For a little bit more Kitfox trivia, so was the 7 Super Sport's vertical stabilizer.

I'm liking my SS7 build just that little bit more now, if that's possible ....

[HighWing]

I didn't know that but an old B-17 Crewman in my neighborhood looked at my Model 4 and said, "It's got a tail kike a P-51".

That explains a lot. Recently when I was doing a bit of research on the creative genius that developed the Kitfox, I found the attached site. I recall back in the day attending one of the factory fly-ins and there in the hangar was a mock up of Dan Denney's newest creation. The mock-up was Denney's way of desiging a cockpit that would accommodate a full sized man in a 3/4 scale Mustang. Very impressive at the time and more so as I read the article linked below.

http://www.ksql.com/myriad/thunder.htm

[av8rps]

Ok, ok. I just knew I'd get a rise out of you guys for my fin height comments. Nothin' like a little more lively forum conversation...

And Yes, the newer kitfoxes have the P-51 vertical shape also, just taller. (So for the experts out there, did the early 51's have a shorter vertical than later ones?)

And YES, keep that fin short and you are guaranteed to be a better pilot! Why would that be? Because you have to be a better pilot just to keep it going straight :D.

I started out with the Avid Flyer prototype as my 1st plane, and compared to an early Kitfox, the Avids' vertical was even shorter. I'm convinced that made me a better pilot. I checked out in a Pitts S-2 in a half hour after putting 300 hours on that short finned Avid. My instructor asked me where I developed such good stick and rudder skills? So something helped.