Another Kitfox IV rebuild project

55 posts in this topic

Posted

So I took a few minutes today to weigh my new gear and the stock Kitfox IV gear. The stock gear legs are 15 pounds for the pair, uncovered, no axles, brakes or wheels. The new gear is 20 pounds, also no axles, brakes or wheels. So looks like I'm about 5 pounds heavier than stock, but 4.3 pounds lighter than a Grove gear which the website says is 24.3 pounds.  I'm happy with that.

On another note, i finally got the fuselage all sandblasted. Weather was not cooperating, so I had to hang plastic sheet in one section of my barn to get it done. I also got the primer coat on tonight, but didn't get any pictures with the cloud of paint mist. White urethane will go on tomorrow I hope. I really hate painting tube structures and will be glad when its done.

Share this post


Link to post
Share on other sites

Posted

Progress is being made. I fabricated a new firewall today. The old one was badly mis-shaped and consequently did not seal to the cowl really at all. In order to make sure the cowl was holding its proper shape I had to make a new windshield and cleco it in place. I then cut a 1/4 plywood blank for the top of the firewall that was a bit undersized and clamped that in place. With the cowl on I used a 1-3/4" diameter cable pulley and with a pencil ground to fit in the pulley bore I ran it around the inside of the cowl. This gave me a line 7/8" offset from the cowl. From there i was able to cut the cowl exactly 3/8" undersize which allows for the bulb seal that I am going to use for the edge seal. The bottom part of the firewall is basically straight cuts so I jus winged that. I didn't build the firewall like the plans say because I don't like the idea of drilling into the fuselage tubes and riveting. I had welded on about 20 tabs for attaching the firewall and welded up all the holes from the previous firewall attachment. It attaches to tabs on the top horizontal tube, center horizontal tube, and the tube under the rudder pedals. The engine mount will also clamp it. This way, I can also get to the nuts underneath for the rudder pedals by just taking the screws for the firewall off from underneath. I'm terrible about taking progress pictures so i only got the final result.
 
I also got the ELT and antenna mounted. Not a big deal but I decided to mount the antenna inside the fuselage and here is how it came out.
 
I also got the autopilot servos mounted and made some temporary pushrods to get things figured out. Everything looks like it is going to work well. A couple picture of those are attached too.
 

20201110_191235.jpg

20201110_191245.jpg

20201110_191251.jpg

20201110_191308.jpg

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Looks like it's coming along.  What kind of AP are you using?  Making progress, but it always takes longer then we expected.  Keep at it.   JImChuk

Share this post


Link to post
Share on other sites

Posted

Looks like it's coming along.  What kind of AP are you using?  Making progress, but it always takes longer then we expected.  Keep at it.   JImChuk

I'm using Garmin. It will have the following components:

  1. Garmin G5
  2. Garmin GMC 507 autopilot controller
  3. Garmin GMU 11 magnetometer
  4. Two Garmin GSA 28 servos

I found that the G5 can be used as the encoder for a transponder,  so it  will feed altitude info to the GTX 327 transponder via serial data out. The serial data input and output can be set for different tasks and I will  use the serial input for inputting navigation data from an Android tablet running Avare or Naviator. This will give GPS steering for the autopilot.

The G5 can replace the airspeed, altitude, vertical speed indicator and skid/slip ball, the weight gain will be minimal. Probably a pound or two, and that  will be saved because  I can lose the blind encoder since the G5 does that  too.

Share this post


Link to post
Share on other sites

Posted

got the laser cut instrument panel that I ordered from sendcutsend.com and couldn't wait to test fit the stuff in the panel. I highly recommend sendcutsend. You simply upload a cad drawing of what you want, pick the material, pay, and about a week later a perfectly cut instrument panel appears on your doorstep. This panel cost $53 delivered.

Wiring is progressing. The airplane had good wiring for the com and intercom, so reusing that. The harness for the G5 and the autopilot stuff is almost done. Still a lot of wiring to do still though.

 

20201119_210016.jpg

2 people like this

Share this post


Link to post
Share on other sites

Posted


gonna be tough making left turns with your rudder pedal setup. ;)

1 person likes this

Share this post


Link to post
Share on other sites

Posted (edited)


gonna be tough making left turns with your rudder pedal setup. ;)

Yeah.  Been fighting getting the rudder pedals to swing smoothly. Too much drag in my opinion. They rotate and are probably smooth enough but won't fall on their own like I think they should. In the picture there is nothing holding that pedal vertically other than the drag on the pivots. I dorked around with it so much that I've now decided to do a little mod to make it better than the factory design. Not really anything wrong with the factory design, just that the original builder of this airplane did a shoddy job on it and the brackets are a bit cockeyed making the bolts not in line with the pivot tube. When I got it the bolts were loose and it was pivoting on the bolts in the aluminum  brackets rather than on the plastic bearing. The build manual says not to do  that. I'm going to put a full length stepped shaft down the middle of the pivot tube so that the bearings stay  inline. Hopefully that will take care of it. Might have  to egg a few holes where it bolts to the fuselage even though I loath egged holes. It'll work though. 

Edited by 109jb

Share this post


Link to post
Share on other sites

Posted

Been working a lot on the airplane and not much picture taking.  I did get the wheel pants on, and tonight a milestone. The fabric covering has begun. I'm going to be using the latex finishing process shown here: http://wienerdogaero.com/index.php

 

20210127_210016.jpg

20210127_215530.jpg

20210131_194515.jpg

20210131_194529.jpg

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Hey John,  Looking at the first picture,  I see you put your pants on one leg at a time just like the rest of us...  :lmao:  Sorry John, I was able to resist on the Kitfox site, but my warped sense of humor is getting the best of me now.  Not meant to be mean, just funny.   JImChuk

PS  good progress!  will be interesting to see how the latex pans out.  Back when I was flying ultralights, I had a Himax.  Was talking to Wayne Ison who designed the Mini max and Himax, and he said that with their first minimax, they painted it with latex, and it was still good nearly 20 years later.  I've looked that weiner dog aero site over in the past as well

Share this post


Link to post
Share on other sites

Posted (edited)

Hey John,  Looking at the first picture,  I see you put your pants on one leg at a time just like the rest of us...  :lmao:  Sorry John, I was able to resist on the Kitfox site, but my warped sense of humor is getting the best of me now.  Not meant to be mean, just funny.   JImChuk

PS  good progress!  will be interesting to see how the latex pans out.  Back when I was flying ultralights, I had a Himax.  Was talking to Wayne Ison who designed the Mini max and Himax, and he said that with their first minimax, they painted it with latex, and it was still good nearly 20 years later.  I've looked that weiner dog aero site over in the past as well

My Sonerai fuselage was covered with polyfiber and finished with polytone. For many reasons the airplane sat disassembled in a hangar and the polytone was badly stained by bird poop. I tried many things to get those stains out without any success. My yellow Kitfox that I sold also had stains on the polytone that would not come out.  On the Sonerai, having read the Wiener Dog Aero stuff, I decided to scuff the fuselage and paint it with latex. It came out great but i didn't get the airplane flying before my mother passed away. Because of having to deal with her affairs, my ailing father and other life stuff the airplane went back in the hangar. That happened in early 2017. The airplane got pooped on again and covered with dust but the latex washed up just fine without stains. Also the cost comes into play, and homebuilding is an adventure, so why not.; Here is a picture of the  Sonerai as it sits now. Looks great even up close. I would consider the gloss as good or probably better than polytone and that is as sprayed without buffing. The wings and cowl are painted with automotive urethane though.

 

20200816_162718.jpg

Edited by 109jb

Share this post


Link to post
Share on other sites

Posted


Looks good the two tubes that run from the spar carry through to the fire wall? Did you run them that way I have only seen that on the model 5-7

Share this post


Link to post
Share on other sites

Posted


Looks good the two tubes that run from the spar carry through to the fire wall? Did you run them that way I have only seen that on the model 5-7

nope. I didn't change any of the basic fuselage structure. I only did the wide body mod and welded on some tabs and made the landing gear.

1 person likes this

Share this post


Link to post
Share on other sites

Posted


I saw the wide body mod what is your total width? Looks nice and roomy.

Share this post


Link to post
Share on other sites

Posted

More fabric work tonight. My shop has a bunch of stuff and I keep a skid loader in there to plow, so I had to find a way to roll out fabric while keeping it clean. What I came up with is moving the skid loader out, sweeping the floor and then rolling out builders paper. I also used the builders paper to make a template for whatever piece I need and then roll out the fabric and cut out around the template. 

So I didn't get any shots of the in-process, but I got the right side fabric on . Coming out good. I can say using the Stewarts process for attaching the fabric is sooo much easier than polyfiber. I did polyfiber on my Sonerai and while it works well, it is a pain to work with it. Messy, smelly, and a million clamps. On this fuselage side I used 2 clamps and only for initial positioning.

TJay - I can't remember how wide it came out. I'll try to remember to measure it tomorrow night, but if I remember right I went 2-1/2 wider each side.

20210201_210503.jpg

20210201_204408.jpg

20210201_204421.jpg

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Tjay. I measured the width at the top of the seat back. It is 43-1/2 st that point

Share this post


Link to post
Share on other sites

Posted

Tjay. I measured the width at the top of the seat back. It is 43-1/2 st that point

Thats awesome thats even wider than a model 7 kitfox Should be great.

Share this post


Link to post
Share on other sites

Posted

2" wider per side then.  Same as mine.  I started to type this last night, but took it off.  When I did mine, I ran a tube from the back corner of the door frame extension down to the longeron for added support.  Another thing it did was give me a place to terminate the front of the fabric on the side of the fuselage.  Then I ran a scrap piece under the bottom of the door.  Saved some fabric that way I figured, and you can't tell it either.  I'm a bit of a cheapskate in case no one's noticed.... Keep at it though John,  looking good.  Will be interesting to see how the latex paint turns out.  I've thought about it many times myself.  JImChuk

Share this post


Link to post
Share on other sites

Posted

Another side done and one side of the vertical tail to fuselage transition piece. So far so good.

 

20210202_195727.jpg

20210202_195737.jpg

20210202_211507.jpg

20210202_211519.jpg

20210202_220317.jpg

20210202_221221.jpg

Share this post


Link to post
Share on other sites

Posted


How are you getting along with the covering system? I got a buddy doing a badlands ultralight with it. Looks like a nice product. Other than you use a lot of blue towels I really like that you don't get brush marks on the tapes.

Share this post


Link to post
Share on other sites

Posted

Covering is going very well. I have previous polyfiber experience, and the Stewart method is a whole lot more pleasant. It is very easy to do and I like that the fabric can be repositioned. I remember doing my Sonerai in polyfiber I used probably 30 spring clamps. On this the most I've had in there is 2. I'm actually using 3m Fastbond 30NF glue which is reportedly the same as Ecobond. Holds very well. 

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Well I'm committed now. Here is a picture with the first cross-coat of latex primer on. I now have the second one on and it is going well. Hope to be painting color on it this weekend.

 

 

20210215_222948.jpg

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Coming along John!  Will be interested in seeing how it turns out.  I was going to use latex years ago, but didn't on the fabric.  I did end up going with a latex DTM  paint on the fiberglass and metal parts on my Avid MK IV and it seemed to be ok.  I had the paint store color match it to the Juneau white poly tone, and it was an exact match.  JImChuk  

IMG_0426.JPG

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Took a step backward today. While painting I noticed that the longerons had pulled in at one location from fabric tension. An Internet search revealed that at least on the model 4 and earlier the final shrink temp should be 300 deg. F, whereas I used the 350 stated in all of the fabric covering manuals. I have the build manual for the airplane but it did not have the fabric covering section otherwise I may have caught it in there. Anyway, I checked the rest of the airplane and only the one bay on top pulled in like this. All others were fine. So I had to pull the top fabric and peel the side fabric from the bay in question. Once I did that the tubes were once again straight. No damage, just a setback and a little fabric and tape to re-do. Worst part was cleaning all the glue to prep for re-attaching.

Click image for larger version.   Name: 20210218_174301.jpg  Views: 1  Size: 111.4 KB  ID: 27308

These tubes are also the same location that incurred the trailering damage on my previous Kitfox, and I have seen many examples of damage in this area on various sites and forums. Most I've seen were trailering damage, but I remember at least a couple that were landing damage. It all adds up to this location being a weak link in the fuselage truss. I had thought about reinforcing this bay before covering and now wish I had welded in some tubes. Since there is still fabric everywhere except that last top panel, I couldn't weld now, or at least it would be problematic, so I decided to fabricate some diagonal reinforcements and install them with structural epoxy. Each end of the 3/8 x 0.035 cross tubes have a half section of 9/16 x 0.035 tube welded on to form a saddle over the longerons. As noted they were then installed with structural epoxy.

Click image for larger version.   Name: 20210218_225957.jpg  Views: 2  Size: 102.6 KB  ID: 27309

Hopefully tomorrow I'll get the side pieces re-attached and a new piece of fabric on top with the tapes and hopefully at least one coat of the primer.

Share this post


Link to post
Share on other sites

Posted

Your project sounds so similar to mine.  I started with a model 2 but it has the model 4 wing, etc.  I used the 3M glue for the fabric and latex house paint.  I wore a mask when spraying but it's nice to not have that toxic odor. I also widened my fuselage to 43.5".  I think you mentioned a DIY AI. I have two 3.5" 480x320 displays in mine one for the engine sensors and the one shown which receives data from a Pixhawk.  I will be flying a club Cessna on Sunday and will evaluate this then.  In the photo, the green line in the center is the horizon.  The software will evolve once I know the Pixhawk is reliable.  Another weird similarity is that I use a skid steer as a snowplow.

IMG_20210218_174834475.jpg

Share this post


Link to post
Share on other sites

Posted

Coclimber, are planning on an autopilot using the Pixhawk?

I will be using large RC servos controlling trim tabs on the elevator, rudder, and flaperons on my build. The plan is to eventually have a three axis autopilot but I'm not sure what direction I want to go for control. Something like a pixhawk would work well but I don't think you can connect a local display to the pixhawk board for control. I don't like the idea of connecting over an RF link.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now