A much faster Kitfox?

[kitfox5v]

Lowell,
You need to add this to your list of toys on HW LLC. I would like to put those on my 4. I've got the ones kitfox sells but the longer teardrop will create less drag.
How did you make the seals for the farings? What are they made of? Thanks
Hope you had a great birthday. Eddie

[av8rps]

Lowell,

That is exactly what I was talking about! I had no idea anyone was doing it to the extent you are. I also think your results from trips with similar aircraft, faired and unfaired, with varying fuel burns proves this is worth doing to our airplanes.

Paul

[HighWing]

Eddie,
I've thought about kitting the parts, but most have to be custom fit. Example - the ribs I used in the horizontal tail are patterned somewhat after the ribs in the speedster tail, but not exactly. The fairings on the struts fit the profile of my horizontal stabilizer and won't fit anyone elses

Below are some photos of the Horizontal stabilizer strut and jury strut fairing tools and procedures.

1 The fairing tooling and a couple of glass fairing pieces. The tool was made by gluing a couple of pieces of balsa of the appropriate width to a strip of thin aluminum. It is then sanded to shape and covered with a single layer of light weight glass - see below for the method. It is then sanded and primed and sanded smooth. One of the fairing pieces is glued at the trailing edge and one is still open. The airfoiled foam piece for fitting to the tubing can simply be press cut using the end of the fairing piece. The fairing section on the right is 20-1/2" long and weighs 1.005 oz.
Fairing Form.jpg


2. One of the Lancair techniques. A single layer of glass cloth is laid down on a piece of vinyl sheeting and the resin is added to the cloth. After it is saturated a sheet of thin Polyfiber or other Dacron covering fabric is laid on top of the glass.
Fairing Pour.jpg



3. another sheet of vinyl is placed on the top of the glass strip and excess resin is squeegeed out.
Fairing Squeegee.jpg


4. The bottom layer of vinyl is removed and the glass is laid out on the form - previously treated with a mold release - and all air bubbles are removed by finger pressure. The top layer of vinyl is then removed and it is rechecked for bubbles.
Fairing Bubbles.jpg


5. The clamp - couldn't find it for a separate photo - is placed to hold the glass - Dacron sandwich so it wont lift up at what will be the trailing edge and secured with a couple of spring clamps. The clamp is made from a length of piano hinge with aluminum angles riveted to the free edges forming a sort of a long clamshell clamp.
Fairing Clamped.jpg

6. The finished fairing is trimmed slowly with a table saw
Fairing trim.jpg

[SWeidemann]

Kitfox Folks,

My Vixen may be one of those Arizona airplanes you are referring to. It has a built up bunch of wood framework & stringers starting just aft the firewall, running to a channel for flush mounting the spring gear, and continuing aft & tapering back into the bottom longerons a ways back. The smooth fabric on the bottom I am certain adds some speed. I get about 120 mph with a 912 ULS. I've also got my mind on some streamlined horiz strut fairings, wing strut/ fuselage fairings & wing strut-to-wing fairings. I already have a set of gas cap fairings to install.

"Also the landing gear (Grove) have been faired into the fuselage on a couple Arizona Kitfoxs going back to Murle Williams 1997 model 5 Grand Champion. Phil Laker I think did that mod to his Vixen also."

Skot

[av8rps]

Skot,

I'm curious, have you ever tested your Vixen to see just how fast it will go wide open? So many times when we are talking about speeds one guy means at x rpm, while another is using y rpm. So I've learned to ask people "What will it indicate as well as show for true air speed when wide open throttle, straight and level, at a reasonable altitude of say 7,500 ft? And what is the engines rpm at your max speed".

Doing it this way is a really good way for us to compare our fleet so we can figure out what mods really makes them go faster.

Now I don't want anyone tearing the wings off their airplanes in an effort to find out that number, but it would be interesting to know if most of our fleet could even come close to their VNE.

[DesertFox4]

Skot- I couldn't remember if your Vixen's gear had that fairing mod or not but sure sounds like it has.


Paul- I've had my model 4 with a 912uls to 132 mph wide open throttle many times. Usually at 3,500 feet or so altitude with the Ivo Lite prop. with rpms
in the 5,600 to 5,700 range for just a minute, two at the most. I have no wheel pants, spinner, jury strut fairings or horizontal stabilizer fairings. I do have gas cap fairings and strut fairings and the wide body modification along with the razorback mod. Empty weight 659 lbs.
My airspeed indicator and gps are within 1 mph on a zero wind day. We actually have quite a few zero wind days here in Phoenix.

Some years back Michael Gibbs had the exact same model 4 Kitfox with the same engine but with wheel pants, large spinner and streamlined jury struts and an Ivo Medium prop and he could hit VNE (140 mph) in level flight under the same conditions. I can't recall what his empty weight was but I think slightly heavier than mine. He also climbed that Kitfox up to 17,999 feet in altitude and still had a little more ceiling left.

[Esser]

I don't think anyone will rip their wings off if it's within reason. A really good advantage to the Kitfox is that is has push rods which helps with flutter. The bad thing is it has a flexible wing which is not good. Also, I don't know how well the flapperons are balanced as I havent got that far yet. On that note, the flapperons don;t seem that stiff. You could inject a dense foam in them but you will certainly get corrosion issues if you do that.

All that being said, I do think the Kitfox has some efficiencies to be gained. If you want to go faster, that is a different story.

[av8rps]

Steve,

Well, you and Michaels Model 4's are just more proof of the potential our planes have for higher speeds. So just imagine if we could do more clean up on them and go even faster...

I think there is something special that happened when the Murle Williams wide cabin mod was done on some of those Model 4's. I'm thinking it must give the short fuselage better aerodynamics / taper, much like the new Kitfox has being wider, and not requiring doors that are bubbled out.

So how about short or long wings? I'm pretty convinced the 4's with the Speedster (short) wing are faster than the long wing. But with the newer and heavier Kitfoxes, the short wing wouldn't work as well as the long wing for speed as it has to fly at too high of an angle of attack even when at cruise. Anybody have any thoughts about that?

Skot- I couldn't remember if your Vixen's gear had that fairing mod or not but sure sounds like it has.


Paul- I've had my model 4 with a 912uls to 132 mph wide open throttle many times. Usually at 3,500 feet or so altitude with the Ivo Lite prop. with rpms
in the 5,600 to 5,700 range for just a minute, two at the most. I have no wheel pants, spinner, jury strut fairings or horizontal stabilizer fairings. I do have gas cap fairings and strut fairings and the wide body modification along with the razorback mod. Empty weight 659 lbs.
My airspeed indicator and gps are within 1 mph on a zero wind day. We actually have quite a few zero wind days here in Phoenix.

Some years back Michael Gibbs had the exact same model 4 Kitfox with the same engine but with wheel pants, large spinner and streamlined jury struts and an Ivo Medium prop and he could hit VNE (140 mph) in level flight under the same conditions. I can't recall what his empty weight was but I think slightly heavier than mine. He also climbed that Kitfox up to 17,999 feet in altitude and still had a little more ceiling left.

[Slyfox]

this is my story. I have the kitfox 4 1200. speedster wings. empty weight 630lbs, my horizontal has the wood inserts, so it's not a flat horizontal. vertical is normal, flat. I have all gaps sealed including the rudder, I have the plastic fairings on the struts. I have the 912uls with the medium IVO inflight. I can take off within 100 ft. I can climb out @ 60mph with a vsi of 1800ft min. I cruise all day long at 120mph. I have thought of cleaning her up a little more. I think 120 is just fine and the take off is great. Just ask Scott. My thought is if you clean her up too much than slowing down coming into an airfield will change, meaning it won't. at least like I like. I love the fact that I can pull the throttle and flatten the prop and do a real nice short approach. unless you have witnessed my short approaches you don't know what a true kitfox can do. I personally don't want to screw with this one. so my dirty little plane, both visual and actual flying is just fine with me. I love the way she is, I'm not changing her. so you can have your fast kitfox if that's what you want. for me if I want fast, which I do, I go fly my rv. she does very much right there at the 200. now that one, if I can make her go faster you bet, that is what she is designed for.

as far as going up high. I believe the kitfox is a low flying machine, you know, flying through the trees and along the river bank. I've personally never flown to 17000 ft even in the rv. do you have oxygen. I've got it in the rv. just asking. the only time I've taken the rv up high is to go over weather.

have a nice day

[n85ae]

I can easily exceed VNE in level flight with N85AE if I firewall the throttle
with my IO-240B, I have a 74" Sensenich prop on it. The engine is very
smooth thanks to recent dynamic balance of the prop, but ...

It feels like a runaway train at 140, and it's NOT a comfortable speed at
all. The plane is all wrong for going fast ...

My Dad (the one with the PhD in Aero Engineering) told me once - Don't
waste your time trying to make it go fast the shape of the plane is all
wrong. If you want to go fast build a different plane.

Jeff

Now I don't want anyone tearing the wings off their airplanes in an effort to find out that number, but it would be interesting to know if most of our fleet could even come close to their VNE.