109JB's Kitfox IV rebuild

[109JB]

So I finally got a chance to get my project airplane home today. This is a Kitfox IV speedster powered by a 80 hp Rotax 912 UL that I bought from an insurance auction. It actually belonged to an acquaintance of mine and was located only about 30 minutes away. The airplane suffered a loss of engine power followed by a forced landing to a waist high bean field, which ended in a rapid nose-over. The vertical tail struck the ground and the aft fuselage got bent as did the vertical stab. The horizontal and elevator look OK as do the wings and struts. The plan is to rebuild the airplane while incorporating a few key modifications which will include these main mods but also a lot of little weigh next to nothing mods:


1. Landing gear area reinforcement


2. Tail spring mount reinforcement


3. Fuselage widening (Murle Williams style)


4. Provisions for future autopilot servo mounting


5. Upgraded panel with only engine monitor, Garmin G5X, tablet computer for navigation, intercom, radio, and transponder.


6. Upgraded baggage area.


It will probably be a little while before I can really get into it as I have to clean out and sell my father's house since he passed away recently. He was a pilot too and I had wanted to get him airborne in the other Kitfox I have but his health never got well enough. I know he would have also loved to see the rebuild of this project airplane. I learned most of what I know about fabrication, welding, machining, and general mechanicing from him.


Anyway, Here are some pics of it stuffed away in the storage part of my barn.

24229
24230
24231
24232
24233

[DesertFox4]

Best of luck on the rebuild John. Sounds like some nice mods.
A friend just installed a Garmin G5 in his Model 4 Kitfox and so far really likes it. The wide body mod is a nice addition too.

Sincere condolences on the loss of your father John.
So many of us here inherited our love for aviation from our dads and owe many of the very best times of our lives to their influence.

[109JB]

Best of luck on the rebuild John...Sincere condolences on the loss of your father John.
So many of us here inherited our love for aviation from our dads and owe many of the very best times of our lives to their influence.

Thanks. What you say is so true. Even though we could butt heads like no other pair, it was because we were so alike. He is and will continue to be sorely missed. It has been 4 months since he passed away and I’ll still be doing something and think to myself “I need to call Dad and ….” I then catch myself. Basically, it sucks!! Now clearing out his house I find things we worked on together from years ago and they bring up now bittersweet memories.

On the airplane I’ve kept the list of structural modifications small because one of my goals is to keep weight down as much as possible. The logs for this airplane say it was 619 pounds empty and I want to keep it under 650 with the mods I’m adding. That would still give me 550 useful load to the 1200 gross. The structural mods I listed should only add a couple pounds and I’m considering covering with Oratex to keep weight to a minimum.

I have looked at the Mangy Fox rebuild that Larry did and it looks great. I’m considering some tail enlargement, but I think I’ll put that decision off until later. I have a friend that has a long wing IV 1200 with a 912 so I’ll probably fly that airplane a bit this spring to check out the handling to decide if I’ll enlarge anything. I have a IV 1050 and on that one I do think it could use more vertical tail surface. I know the 1200 has a larger tail so maybe it is sufficient, or maybe I just need to increase the rudder chord to accomplish what I want to do.

On that note I do have a question. Since this is a speedster it has the airfoiled tail surfaces. Since there is some tail damage, I was contemplating going back to the slab surfaces as it may be easier to do the repairs and eliminate the wood ribs. Can anyone who has flown both the slab and airfoiled surfaces relate if there is any handling or performance benefit to the airfoil surfaces? If there is, I would keep them but if it is only aesthetic then they may go depending on what I see when I pull the covering.

The most major mod I want to do is eventually put in an autopilot to ease the workload on cross countries and a Grove gear. Beyond that there aren’t really a bunch of mods I want to make. My experience so far with my IV 1050 indicates that it is a pretty decent airplane the way it is and I don’t want to make it into something it isn’t

[efwd]

I bet Kitfox has the capability to cut new wood ribs for the IV. They are the simplest things to install. For the $ I would certainly aim to keep it a speedster. IMHO

[109JB]

I have another Kitfox IV that has slab sided tail surfaces. Call me an odd duck but I actually prefer the aesthetic looks of them over the airfoiled speedster surfaces. I'm not at all worried about cutting ribs, most of the ribs are probably intact anyway. Even though I prefer the slab side surfaces I am more than willing to keep the airfoil surfaces for a benefit. In that vein, I have been reading past Kitfox articles and found one that said:

"The vertical fin, rudder, stabilizer and elevator have a moresubstantial appearance with their newintercostal ribs and they do give the tailgroup a more effective feel in flight."

So it sounds like there is a handling qualities benefit. Be nice to hear from anyone that has flown both to see the magnitude of this benefit.

[109JB]

Finally got some time to mess with this one and got the Rotax 912 running today. I know the guy this airplane used to belong to and it was a afternoon flight in late August last year when the engine quit when he was at about 1,500 ft agl. I didn't really do anything to get it running. I just ran a hose from the pump inlet to a gas can on the ground, put some run out blades in the prop hub and it started pretty much right away. The only things are:




1. The temp and dew point (23/15 deg C) are right in the middle of the "moderate icing at cruise power"/"Serious icing at descent power", so I guess it is possible it was carb ice, but this Kitfox has the short filters back at the firewall which everyone say are not ice prone. I guess the reasoning is that with the carbs back there they are drawing in warm air from inside the cowl. I wonder about that theory though.


2. The other thing I notice is that this airplane doesn't have a fuel return line as called for by this Rotax Safety Notice. I wonder if this could have been a case of vapor lock.


Anyway, I'm happy it runs and for the price I paid I'm really happy. To let the cat out of the bag, I paid $5100 for the whole airplane and it looks like the only real problem is the little kink in the fuselage. It has a newish Garmin SL40 comm radio, a Terra transponder with encoder, and a flightcom intercom. I figure those are worth about $1500 all together.

Here is a short video of the run today with flopping windshield and all.


https://youtu.be/aTSHOBCX4Lg

[109JB]

Another day of playing with my new project. Here is the second run of the engine after getting it home. I ran it for about about 5 minutes this time. Just enough to get it warm enough to do a full throttle run. It ran great but I must have the prop pitched too high as I could only get about 4800 rpm. I'm very very very happy. I still have lots of checking and running to do but it is going perfect so far.



https://youtu.be/D9j-Sh1-IjU

[109JB]

Here are some pictures of the fuselage damage from the nose over. Not as bad as I thought. Looks like the longerons can be straightened, except for maybe one in one bay. Only a couple diagonals will need to be replaced. I'll probably straighten everything and then decide which ones don't cut the mustard. The 2 diagonals I think are kinked so they will have to go, at least the kinked section. The one picture with the colored lines shows the tubes that are bent. The green ones are those I believe can be straightened. The yellow ones are the ones that are borderline and the red ones are the ones I think definitely need replaced. I'll see once I start working on it. I may try to do some straightening before stripping it down to a bare fuselage.

[109JB]

I was doing a little on the airplane today and came across something that puzzles me. The flaperons on this airplane appear to be multiple piece units with a joint at every hinge location. I forgot to take a close up but you can somewhat see it in this picture. Basically it has 4 short flaperons and they have about a 1/4-inch gap between them with a small tab at the trailing edge to keep them aligned there. The gap is covered with a bit of white duct tape. Not sure I'm too keen on this arrangement but apparently it works. I've tried searching both on the forum and on the internet but can't find anything on this. Anyone know about this? My other Kitfox IV has one piece flaperons.

24337

Edit: Zoomed in you can actually see it pretty well. Here are a couple cropped showing the joints. They still have some tape on then in these.

24338
24339

[Dusty]

From what I have seen this appears to be a speedster thing possibly to stop binding under high G.
I have only seen one speedster here, it also had an extra mass balance per side.

[avidflyer]

Page W-D-10 in my Kitfox 4 manual describes how to slot the flaperon for the speedster model. JImChuk

[109JB]

Thanks guys. That is exactly what my airplane has. The manual says it is for high load situations. If i were the original builder I don't think I would have put the slots in. Oh well. Not much I can do about it now. Thanks again for letting me know what they were.

[109JB]

Got a little more done. Last night I made a towbar because moving it in and out of the small space where I have it in my barn right now was a real pain with the wings folded. I was going to just buy one until I saw the prices. I spent a total of $14 for 2 wheels and the rest of it is a piece of 1/2" solid bar, a piece of 3/4" black gas pipe, a few washers an couple cotter pins and a piece of a can of rustoleum green paint I had lying around. about an hour of cutting and welding and I had this.

24341

This morning I went about making a tubing straightener. I wanted something easier to handle that the 2x4 setup I used on my other kitfox because you needed 4 hands to operate that setup. I had a hardwood picture shelf thing that was getting tossed that I used for the backbone. The clamp screw is made from a 6" carriage bolt and a couple 1/4" bolts I had on hand. this screws into a nut that is welded to the 2 straps that have a series of holes spaces about 2 inches apart From there are some 3/4" plywood blocks that I drilled a 1/2" hole through the edge and then cut done the center of the hole to straddle the tube. That's a piece of 1/2" bar in there where the longeron or other tube being straightened would go. The outer blocks can be moved closer together or farther apart depending on length needed.

24342

So I did some straightening that I'll talk about later, but while lying under the airplane working on straightening tubes, I saw this:

24343

Anyone see a problem with this picture?

Back to the tube straightening. I worked on it for about 1-1/2 hours and got things pretty straight. It is crammed into basically the size of a small 1-car garage so I couldn't get pictures too well, but all of the longerons are going to straighten fine, and I even got the 2 diagonals pretty straight but not quite straight enough. I will have to cut a section of those out and replace, but it looks like I will be replacing a total of about 12 inches of tubing to get the fuselage fixed. I'll see if I can get some pictures later.

[Dusty]

That spring setup is a bit suboptimal!
can you post a photo of your tube straightener in action as I can't quite picture how it operates.
cheers

[109JB]

The weather looked a little iffy this morning, but cleared up so I was able to pull the airplane out and do a good bit of straightening of the tubes. Still a little more to go but I'm taking it slow. Here are some pictures of the tool I made in action:

This one shows it loaded onto the lower longeron. The screw is on the bottom and when you crank it it draws the straps and the center light coloerd plywood block toward the dark colored backbone board.

24344

This one shows how far past you have to go the account for spring back of the tube.
24345

Here it is after releasing the tension on the screw
24346

Here is a sight picture of the top longeron showing how much it bent during the mishap.
24350

This is after about 10-15 minutes using the straightener. I go real slow because you don't want to overbend it back the other way. So I go slowly and a lot of times you have to slide the yoke around to the high spot because it may not always be in the center and cna change as you slowly work th tube back straight. Just to note, this isn't straight enough but its getting very close.
24349

[109JB]

As a reminder, this is what the airplane looked like before I started straightening this morning:
24351

This is what it looked like just before I put it away this evening.
24352

[Dusty]

Thanks for the photos, now it all makes sense.

[109JB]

I have a question for all the more experienced Kitfoxers out there. This airplane has a little problem. Now that the fuselage is straight to where it needs to be I find that the leading edge of the flaperon on the right wing when folded will hit the horizontal tail. This happens when you rotate the flaperon into the vertical position next to the vertical stabilizer.

It must have been built this way because when I got the airplane it came with a set of the wing trailering supports and the one that connects from the aft fuselage to the wing strut had been lengthened to keep the wing out far enough that the flaperon didn't need to be rotated to the vertical position. I know the 2 previous owners but not the original builder of the airplane. and will ask them if it was always this way but based on what I see it must have been.

I didn't get a picture of this and I have since taken the wings off of the airplane.

It obviously didn't affect the flight performance of the airplane because the 2 previous owners and others I know that have flown the airplane said it was a really nice flying airplane.

If possible I would like to correct this because as it is the airplane would never be a candidate for an enclosed trailer since not being able to completely fold that wing makes it too wide.

What do you guys think? Can it be rectified?

[avidflyer]

Are you saying that the wing is lower at the tip then it should be? Looking at old pictures of my Kitfox 4 with the wings folded, the flaperon clears the elevator by about 3" with the flaperon tight against the vert. stab. My first thought would be to measure from the rear spar bolt hole to the lift strut attachment bracket. If that dimension is longer then it should have been, the wing tip would be lower. (less dihedral then it should have had) Compare both wings. Other then that, is the elevator level/parallel in relation to the wing carrythroughs? Or maybe I didn't understand your question. JImChuk

[109JB]

With the wings folded the right wing tip is lower in relation to the left wing tip. Not by much, but enough that you can't fold the right wing fully without the flaperon leading edge touching the fabric on the horizontal stabilizer. It clears the spars on the H-stab, but with the airfoil ribs it touches the fabric. Since I was recovering anyway, I did fold it all the way by cutting the fabric out of the innermost bay on the top of the H-stab. If I remember right the left wing clears by an inch or 2 but not more than that. Dang it. I should have taken pictures.

Looking at the build manual I have, the placement of the wing strut brackets on the spar is different for the speedster. They are placed 1 inch farther outboard. This would mean less dihedral on the speedster which would lessen the clearance to the stab on the folded position.

Measuring the geometry, the struts would have to be extended about 3/8" to get clearance when folded. I'll install them as built first and use a laser to see what the dihedral is on each side and if it matches first before making any decisions, but I think 3/8" might be doable on the strut heim joints.

[t j]

The damage in the photos looks to me like it ended up on it's back. I would stretch a string on all the struts and wing spars to make sure nothing is bent there. Also, you can't change the dihedral much once the attach holes are drilled in the wing spars.

[109JB]

Yes it was on its back. That was said in the first post. The only wing damage was one broken tail on a top leading edge short rib. Everything is straight now. This problem existed from the builder as evidenced by the modified trailering strut for that side. It doesn't need much change in dihedral and even if it did one could always fabricate new internal reinforcement plates and rivet them in. Would only need to do the bottom plates. I'll find out if the dihedral is off once the weather is fit to put the wings back on.

[jrevens]

In analyzing this, one thing that would cause the "misalignment" when folded is a slight difference in the angle or position of the tube that is welded to the spar carry-through tube of the fuselage, that the spar attachment bolt goes through. Just the tiniest misalignment of that tube (the holes drilled in the carry-through for it) when it is installed/welded will result a considerable misalignment out at the wingtip when folded, regardless of how correct the dihedral is in the flying position.

[109JB]

Lets see if i understand what you are saying correctly. I think you are saying that if the fuselage mounted tube the rear spar bolt goes through is rotated CW or CCW when viewed from the side of the fuselage, that this will affect the height of the wing tip when folded.

If I am understanding you correctly I will have to disagree. While that may be true if the rear spar was the only pivot point, it isn't. The lower strut mount on the fuselage is also a pivot point. So when folded the strut is still holding up the wing. The three points that are of concern here are the rear spar attach, the lower fuselage to strut attach, and the strut to wing attach. The triangle formed by these 3 points is very stiff and the mechanical advantage in the strut/wing setup will far outweigh any bending moment influence that bolt going through that short 2.5" long tube at the rear spar attach can muster. So in essence if that tube were misaligned/rotated, folding the wing could put undue stress on the spar bolt, reinforcing plates, etc. but it would not have any appreciable affect on the tip position.

[jrevens]

You’re right, John. I was obviously not thinking very clearly. If the 2 pivot points on the fuselage are not in exactly the same alignment with each other, comparing the right side to the left side, or the fuselage & tail structure isn’t straight, or the wing dihedral and washout isn’t exactly the same, etc., then the position of things when folded may not be in alignment & where you want them to be. You & I and everybody else knows this, so I don’t know why I was thinking the way I was. Sorry about that!

[t j]

Sorry, I missed that you said in the first post that it nosed over. Blame it on the 70's. I'm 70 now.:D

When I started rigging the wings on my classic 4 the instructions said to make sure the wing tips were even when folded. I chased that for two weeks. The best I could do was get the wing tips to about an inch and a half from even when folded back. I studied the situation for some time and finally observed that the rear wing spar to fuselage attach bolt and the lower strut to fuselage bolt formed the pins of a "Hinge" that the wings swing on when folding back.

To check the alignment of the lower strut attachment bolt holes I leveled the fuselage and dropped a plumb bob with the string running through the top carry through wing attachment lug. On the wing with the high tip, the plumb bob point centered in the lower strut bolt hole. On the wing with the low tip, the point of the plumb bob was about 1/4 inch forward of that bolt hole. It then became clear what was going on. One wing hinge was vertical and one was tilted a little off from vertial.

I called the old Skystar factory and asked what I should do. He said to just rig the wings when spread and not worry about the uneven tips. Mine was not a speedster so dihedral provided plenty of clearance from the horizontal stabilizer.

Does this make any sense?

[109JB]

Does this make any sense?

Sure does. I have a IV-1050 and I know that one wing sits a little lower than the other when folded too, but since the long wing IV has more dihedral it still clears by plenty. I had thought that maybe the lower pivot was too far forward and was going to check. Not sure anything could be done about the short of welding on a new strut mount to the fuselage. That would probably result in the strut not bent right and having to make a custom length set of struts. Lots to think about. First thing will be to get the wings back on and measure a ton of stuff. I probably should just leave it alone but it's supposed to be a folding wing airplane so I'd like to fix it. We'll see.

[109JB]

I was looking through the paperwork I got with the airplane for something else and happened to see notes from the second owner who re-did the airplane back in 2007 and one of the entries read "Why doesn't right wing fold correctly? So it seems that the right wing didn't fold right way 13 years ago either. I know that guy so I'll give him a call and see if that note was referring to this issue (I think it must be) and if he ever found anything out about it.

[109JB]

Having completed my initial assessment of the airplane I decided it was time to get the shop ready and to do more disassembly. I'll have some pictures of the airplane later, but wanted to comment on a practice that just flat out puzzles me. I even went into the builders manual that came with the airplane and it is in there so it isn't a one-off builder screw up. What am I talking about? Rivets in steel tube structure. Now I'm not talking about cases where there may very well be a valid reason for doing it. I'm talking about doing it just because it is easier.

For example, the firewall on the Kitfox IV at least, is riveted to 3 different tubes at the firewall station using aluminum pop rivets. There are probably 30 rivets for that alone. That is 30 places for potential water intrusion and if water does get in it has no way to get out. Can you say "rust". Sure, the firewall needs the rivets to hold the different pieces of the firewall sheet metal together, but it doesn't need to be riveted to the tubes. It can't go anywhere because it is sandwiched between the engine mount and the fuselage and any more security it needs can be handled with a few tabs. I've now have all of those drilled off rivet tails inside of those tubes and can't get them out. At least not easily. I'm going to wind up welding all of those holes shut and putting on maybe 6 tabs for the firewall security.

Another example is a hole drilled into the top of door sill tube. What is it there for? A little wire clip that you can drop into the hole to keep the door open about 3 inches at the bottom. Ok fine, but it is also about 3/16" diameter and in the top of the tube. There is obvious rust around the hole telling me that water has had a chance to get in there and there isn't any other hole at the low point for the water to get out. I'm seriously debating whether I should just replace that whole tube or at least cut out the rear section of one to see if it is rusted inside.

I could give several more examples from my airplane from nose to tail but you get the point. I would much rather see a screw and a little sealer that a rivet. Aluminum pop rivets have a mandrel that many times falls out leaving a hole and they also work loose. Probably 1/3 of the rivets I removed were loose.

From my perspective drilling holes into steel tube structure for no good reason is an unnecessary practice. I previously built a Sonerai IIL and when I welded that fuselage it wound up with exactly 4 holes that go through into the interior of the tube structure. Those holes were put in specifically for a path to introduce preservative coating to the inside of the tubes. These holes were then plugged with sheet metal screws and a sealer (they don't leave tails inside if removed.). It can be done, and in my opinion should be done this way if possible.

OK. I'm coming down off of my soapbox now.

[109JB]

Have had other things going on but did receive my Garmin stuff and have had a chance to play with the G5. Super easy to get going in a basic sense. 2 wires and an old serial port plug got it going. I'll be putting it in with a GMC507 autopilot controller, and servos, so I want to be able to pipe in navigation data so it can fly a planned route. In that vein, I played around with a $5 bluetooth module, and a $2 TTL to RS232 module, and was able to get Avare on my Android phone talking to the G5 without any problem. You can tell that the nav is working in the picture below because the CDI needle on the G5 has appeared. Without a nav signal the CDI isn't there. There is also a pic of my current plan for the instrument panel. I may or may not mount the standard airspeed indicator. Also, to answer the inevitable questions, the green LCD below the G5 will be an engine monitor that I will build myself, and the green LCD on the right side of the panel will be a home-brew instrument that has the basics in digital format in case I want to fly from the right seat.

24647

24648

[DesertFox4]

I like it John. Was very impressed with a friend's new install of a G5 in his model 4-1050.
Nice layout on that panel. Everything you could need.

[109JB]

Well I finally got some other things done and started to work on the Speedster rebuild. I got the airplane moved to the front heated side of my barn from the rear cramped cold-storage area. In the background you can see another project that I need to work on and will be doing so concurrently with the Kitfox.

25614

I also have started repairs to the cowling that was damaged during the nose-over. I probably should have just bought a new lower-forward cowl that was the most damaged. I made a jig to hold the cowl in its proper shape using the cowl from my flying Kitfox. I started by glassing patches on the largest cracks so that the cowl would again hold its shape well enough to chase down the other smaller cracks.

25615

Once that was done it was chasing the smaller cracks, and there were a lot of them. Here are a couple pictures of the inside and the outside of the lower front cowl after all of the glassing was complete. Every crack got a minimum of 2 layers of biderectional cloth inside and at least one, or two layers on the outside. The outside layers will get sanded back to fair the shape, but at least one external ply will remain after sanding.

25616
25617

The upper front cowl is getting the same treatment but there is far less damage. What is pictured here is the extent except for one crack that still needs to be repaired on the top by the camloc fastener.

25618
25619

Its amazing how long this takes. I probably have 20 hours into these repairs on the cowl alone and I still have to fill and fair the exterior. The good news is the rest of the cowl only has a couple small cracks.

The wings are fine and I really just have to decide what to do about the fuel tanks on them and recover them. However, I have wing pieces from another Kitfox IV that was damaged but there is enough of the spars and ribs intact to make extensions. At this point I think I am going to make removable extensions to extend the wing by one bay each side.

The fuselage is straightened and all looks fine except I need to replace 2 diagonal tubes that were bent beyond the point of straightening. Other than that, some of the tubes in the aft fuselage are showing some rust peaking through the powder coat. Nothing major or needing tube replacement, but I may sandblast the entire fuselage and epoxy prime and paint it. Before that I will weld up most of the holes that were drilled for rivets. I just don't like this practice and in most cases is not necessary.

More to come but probably slowly.

[109JB]

So I'm starting to work on the fuselage, removing coating on tubing, reinforcing the main landing gear area, adding some tabs, etc. One of the things on my list of modifications is to reinforce the tailwheel mount. I want to get this done before epoxy priming and painting the fuselage. Does anyone have a picture of how they have reinforced the tailwheel mount to give me ideas?




Thanks,

John Brannen

[Eric Page]

Does anyone have a picture of how they have reinforced the tailwheel mount to give me ideas?
See the last photo in this post (https://teamkitfox.com/Forums/threads/10652-Project-5-build-thread?p=93350&viewfull=1#post93350).

[109JB]

See the last photo in this post (https://teamkitfox.com/Forums/threads/10652-Project-5-build-thread?p=93350&viewfull=1#post93350).

So it basically just needs a gusset? I was thinking it needed something else. If that's all, I'll do it tomorrow.

Thanks.

[Jerrytex]

https://teamkitfox.com/Forums/threads/9710-pic-needed-of-tail-spring-mounting-flange-reinforcment?p=83606#post83606


It's actually a thicker plate on the bottom, and gussets.

[109JB]

I've been working on getting things welded on the fuselage in preparation for finishing sandblasting.

Here I finally replaced the kinked tubes from the nose-over damage. Ultimately decided I couldn't get them straight enough and just replaced them. Those were the only tubes that had to be replaced due to the damage.
25774

Here is my mockup of the autopilot servo mounting.
25775

And then the brackets welded in for the actual mounts. Also in this picture is my mod to the elevator bellcrank to eliminate side-to-side play.
25778

Also did a cockpit widening modification.
25779

Added a bunch of tabs too. I think I finally have it to a point where I will finish sandblasting and epoxy priming and painting the fuselage.

[109JB]

Its either raining or the wind is blowing 20 mph so I can't sandblast. So I decided to start welding up my cabane landing gear. I got the two legs done to the point where they fit on the fuselage. Still need to cut the front leg tubes and put the axle mount tube in.


25814
25815

[109JB]

Got the new gear almost done. Just 4 straps to weld over bushings. Came out good.

25888

[bbs428]

Interesting thread. Love the instrument panel.
All the fixes and tweaks are coming out real nice.

[109JB]

Got some better pictures of my new gear and also did some weighing.


The stock Kitfox 4 landing gear weighs 7.5 pounds per side for just the gear leg uncovered.
A wheel, tire, brake and axle weigh 16 pounds per side (Carlisle 16x6.5-8 4 ply on there now)
So the total for the stock gear is 47 pounds




My new gear, each leg + the shock strut weighs 8 pounds per side
The cabane weighs 4 pounds
Same wheel, tire, brake and axle, so 16 pounds per side
Total = 52 pounds


So it looks like I'll gain 5 pounds for the gear itself, which I think is worth it. I will be going from the 16x6.5-8 tires to the 21x12-8 tires so that is an additional 8 pounds for the pair (10.7 pounds vs 6.7 pounds per tire difference). So my total landing gear weight will be 60 pounds.

I read in another recent post that the Grove gear is about 35 pounds just for the gear leg. My gear without axle, tire, etc works out to 20 pounds so I'm very happy with that.

25994
25995

[109JB]

I guess the grove gear for a kitfox 4 is about 25 pounds. The 35 pounds is for 5 through 7 series. Still happy with my 20 pound gear though.

[109JB]

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 close to final result.

26068

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.

26069

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. Here are a couple pictures of that too.

26070

26071

[VictorV]

Finally got some time to mess with this one and got the Rotax 912 running today. I know the guy this airplane used to belong to and it was a afternoon flight in late August last year when the engine quit when he was at about 1,500 ft agl. I didn't really do anything to get it running. I just ran a hose from the pump inlet to a gas can on the ground, put some run out blades in the prop hub and it started pretty much right away. The only things are:




1. The temp and dew point (23/15 deg C) are right in the middle of the "moderate icing at cruise power"/"Serious icing at descent power", so I guess it is possible it was carb ice, but this Kitfox has the short filters back at the firewall which everyone say are not ice prone. I guess the reasoning is that with the carbs back there they are drawing in warm air from inside the cowl. I wonder about that theory though.


2. The other thing I notice is that this airplane doesn't have a fuel return line as called for by this Rotax Safety Notice. I wonder if this could have been a case of vapor lock.


Anyway, I'm happy it runs and for the price I paid I'm really happy. To let the cat out of the bag, I paid $5100 for the whole airplane and it looks like the only real problem is the little kink in the fuselage. It has a newish Garmin SL40 comm radio, a Terra transponder with encoder, and a flightcom intercom. I figure those are worth about $1500 all together.

Here is a short video of the run today with flopping windshield and all.


https://youtu.be/aTSHOBCX4Lg

Did you fly that beast home with all the bent tubing etc? I like the floppy windscreen. Duct tape might have been appropriate :)

[109JB]

Did you fly that beast home with all the bent tubing etc? I like the floppy windscreen. Duct tape might have been appropriate :)

Fortunately it was only 20 miles from my house and I won the auction for it. Trailered it home.

[109JB]

Working on the panel now doing a test fit of components. I had the panel laser cut by sendcutsend.com. The harness for the G5 and autopilot components is completed except for final install and hookup to power. Harness for the intercom and com radio is also complete as I am using the old harness from before disassembly because it is in good condition and well made. That saves some time. On the left side of the panel is the G5 efis, a digital tachometer, a display for a home-brew engine monitor, and a tablet. Behind the tablet is a hole for a glove compartment. On the right side of the panel is the radio stack with transponder, com, and autopilot controller. Above those is the trim indicator and the intercom. Far right is a backup airspeed indicator, another display for whatever, the hobbs and the ELT panel. Switches across the bottom. I still have to fabricate a tablet mount , then pull it apart and put the matte black vinyl overlay on it. Even this simple of a panel is a lot of work and it ain't done yet.

26131

[109JB]

I did some more work on the panel tonight. It has been overlaid with matte black 3m vinyl and is getting populated. The white in the middle is the glove compartment that will reside behind the tablet. Still have to mount a few things including the tablet mount but it is getting there. Also waiting for the AC switches for the ignition. For the switch labels I cheaped out and printed vinyl labels on my printer. Not perfect but pretty darn good and really easy.

26202

[109JB]

Took the last couple weeks building off to go get this:

26516

[rv9ralph]

Cool.. Congrats.

Ralph

[DesertFox4]

Congrats John!👍👍👍

[Eric Page]

Very cool -- congrats!

[Frontier Fox]

That is fantastic. I’m sure it will be worth the effort.

[PapuaPilot]

Congrats John! 👍 👍 👍

[109JB]

Haven't posted about my project for a while. Been working lots to hopefully have it ready yet this spring. However, I've reached an exciting and fun stage. Started fabric covering. But I also posted in another thread about mounting the wheel pants. So here are a few pictures of both of those steps. I'm using 3m Fastbond 30NF to attach the fabric. Reportedly it is the same as the Stewart EcoBond. A friend is using Ecobond and the 3m stuff I have looks, smells, feels the same and holds like gangbusters. I did a test panel with it last year. Will be using the 3m Fastond up through tapes and then using the latex process at http://wienerdogaero.com/index.php I have thought long and hard about this and part of my decision is based on my Sonerai. That airplane was finished with polyfiber using polytone for the topcoats. It is fine except that bird dung and other things stain the polytone and I tried all the tricks and could not get the stains out. As a result I topcoated the poytone with latex and it has held up well, has better gloss than the polytone and doesn't stain. Don't take this as a recommendation, only as a this is what I'm going to do and I intend to post my progress, results and occasional updates on longevity.Anyway, here are the pictures.

27074

27075

I also decided to square off the top of the rudder just because I like the look better.

27076

[109JB]

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. Like this:

27091

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.

27092
27093

[109JB]

Another side done and one side of the lower fin to aft fuselage transition.

27117
27118
27119
27120
27121

[109JB]

Well, I am committed now. The first cross coat of latex primer is on.

27288

[jrevens]

I’m interested to see how it turns out for you, John. I saw a very nice looking latex paint job on an airplane once. Maybe you’ve already commented on this, but how does latex house paint hold up to fuel?

[109JB]

My Understanding is that it holds up pretty well as long as any spills are wiped up promptly. I gathered this information from a few sources. It seems that nowadays the model airplane crowd is also using latex paint on large size models powered by gasoline engines. I used to be into RC airplanes pretty heavily about an eon ago, but never used latex. The consensus there is that latex is gasoline proof except for the possibility of staining if gas is left on the painted surface. This is also what I have gathered from research about latex on full size airplanes too.

On my Sonerai it was covered with polyfiber and topcoated with polytone. I found that with that airplane and also my Yellow Kitfox I sold last year that the polytone stains horribly. Both of those airplanes had what stains from bird droppings that I could not get out. The Yellow Kitfox also had gas stains due to bad gaskets on the fuel caps. The Sonerai, I wound up cleaning and then scuffing with scotchbrite, then putting an additional topcoat of gloss white latex. It came out great and has not stained. After painting with the latex, my mother passed and the airplane wound up in the hangar for another couple years and got covered with dirt, grime, and bird droppings again. When I finally brought it home to get flying again last year, I simply washed it with a hose and mild detergent and it looks as good as the day I sprayed it on. I will say though that where the latex is on the Sonerai it does not get fuel on it, but the bottom does get some oil and exhaust smut and that has cleaned up fine.

[109JB]

BTW, the first cross-coat got sanded this evening, fixed a couple spots where I didn't get the pinked edges locked down, and then put on the second cross-coat. The really nice thing so far is the ease of this process. The primer coats all go on with a cheap foam brush unlike polyfiber where everything is sprayed. Only the final color coats are sprayed with this. Also the primer sands easily with 320 grit dry paper. The primer is thinned with water enough that it flows out very nicely and only requires a very light sanding. I think I have a method worked out that will yield nice results. Brush on the thinned primer and once getting about 1/2 of a fuselage side done, go back and "tip" it with a pretty dry foam brush. From there it flows out great. Also dries fairly fast. I was able to sand about 30 minutes after finishing brushing and by the time I got to the last part that was painted it was ready. I'm hoping I'll get all the primer on before saturday and then get ready to spray.

[jrevens]

My Understanding is that it holds up pretty well as long as any spills are wiped up promptly. I gathered this information from a few sources. It seems that nowadays the model airplane crowd is also using latex paint on large size models powered by gasoline engines. I used to be into RC airplanes pretty heavily about an eon ago, but never used latex. The consensus there is that latex is gasoline proof except for the possibility of staining if gas is left on the painted surface. This is also what I have gathered from research about latex on full size airplanes too.

On my Sonerai it was covered with polyfiber and topcoated with polytone. I found that with that airplane and also my Yellow Kitfox I sold last year that the polytone stains horribly. Both of those airplanes had what stains from bird droppings that I could not get out. The Yellow Kitfox also had gas stains due to bad gaskets on the fuel caps. The Sonerai, I wound up cleaning and then scuffing with scotchbrite, then putting an additional topcoat of gloss white latex. It came out great and has not stained. After painting with the latex, my mother passed and the airplane wound up in the hangar for another couple years and got covered with dirt, grime, and bird droppings again. When I finally brought it home to get flying again last year, I simply washed it with a hose and mild detergent and it looks as good as the day I sprayed it on. I will say though that where the latex is on the Sonerai it does not get fuel on it, but the bottom does get some oil and exhaust smut and that has cleaned up fine.


Oratex will also stain, as some of us have found out. I think that a polyurethane paint is probably one of the few types that are very resistant to fuel and most other things. The PPG Durathane that I used on my first homebuilt was extremely "durable" and it really looked just as good after 28 years (and I expect it still does) as it did when I applied it. The latex intrigues me... I think I'd try it if I ever build again. Do you think that it is going to be heavier than the typical Poly-Tone job, for instance?

[109JB]

Oratex will also stain, as some of us have found out. I think that a polyurethane paint is probably one of the few types that are very resistant to fuel and most other things. The PPG Durathane that I used on my first homebuilt was extremely "durable" and it really looked just as good after 28 years (and I expect it still does) as it did when I applied it. The latex intrigues me... I think I'd try it if I ever build again. Do you think that it is going to be heavier than the typical Poly-Tone job, for instance?

I will certainly find out about the weight. I have a 1 square foot piece of the fabric that I cut off of this airplane and saved when I started the rebuild that is obviously Polyfiber with polytone topcoat. I also have a test panel with the latex that is done through primer and just needs topcoat. Once I spray topcoat I'll cut a 1 square foot piece of the test panel and weigh them both. I can say though that the paint when thinned covers the fabric very thin but is doing a good job. I don't even think I have used a quart of paint and have done 2 cross coats on the fuselage. Just judging by how it is filling the weave so far I think I will probably need about 2 or 3 more cross coats before putting color on, so primer will be only around 1/2 gallon on the fuselage.

According to the information at http://wienerdogaero.com test panels that he has done show that the latex comes out about the same weight as the Polyfiber.

Here are the benefits I'm seeing so far with the latex.

Cost. It doesn't get any less expensive than this.
Non-toxic. Huge benefit here.
Everything is brushed except color coats. This one is a somewhat minimal consideration but I don't have to hang plastic in the shop for as long.
I can brush paint the jambs and a few internal spots where fabric will show.
Looks. I was very pleased with even as-sprayed latex finish on my Sonerai, and the results Malcolm at wienerdogaero gets by buffing look amazing.

[109JB]

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.

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.

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.

[Birdseyeview]

You mentioned cleaning the glue off the fuselage tubes was a real pain. Have you tried rubbing the glue off with a rubber sanding disc dresser? If you're not familiar with these its a rubber bar about 1 1/2" square and comes in various lengths (see picture below). Its used to clean up belt sander belts that have caked up with residue. I got mine at a local hardware store that sells professional sanding tools. This works like a dream on excess Stewarts glue anywhere on the fabric and on fingers too. If the 3M glue you're using is anything like the Stewarts glue it should work great, just needs a little rubbing. By the way - I've painted my Kitfox with latex last winter per the weinerdog.aero method and I couldn't be happier with the results. I rolled my primer and top coats on with a nylon foam roller and never did use the new air compressor I bought. The final coats of black and white trimix my paint scheme came out glossier than polytone and I didn't actually need to spray anything. The yellow I used was not that glossy (more like polytone) but it turned out to be a great look anyway.

27310

[109JB]

Yep. Sanding disc eraser is what I used. It just was a pain getting it off everything, especially getting the loose top edge of the side fabric cleaned.

[109JB]

Just noticed you are in Oregon, IL. Not too far from me in Morris, IL. We'll have to do a burger run together once we get our birds flapping their wings.

[Birdseyeview]

Yes on the get together somewhere down the road. I'm hoping to have first flight this summer. If you're ever in the Rockford area give me a shout. Its alway interesting to talk with other builders and to see what they're doing.

[109JB]

Hey Larry,. I'd be interested in seeing pictures of your paint if you can post some.

[Birdseyeview]

Here's pictures of my paint job as requested. These were taken this last fall. I still have the protective plastic film on the windscreen and doors. The paint scheme is a knock off of a classic design that you might recognize. The same pattern is on the wheel pants as well but I didn't use latex on the wheel pants.

2731827319

[109JB]

Had about 1-1/2 hours this morning and got the side fabric stuck back down and the new top fabric on. Heat shrunk everything and longerons still straight. Once primed you won't be able to see it. Glad I fixed this instead of having to look at it for years and years.

27320
27321

[109JB]

Here's pictures of my paint job as requested. These were taken this last fall. I still have the protective plastic film on the windscreen and doors. The paint scheme is a knock off of a classic design that you might recognize. The same pattern is on the wheel pants as well but I didn't use latex on the wheel pants.

2731827319

Very nice. You said you rolled it and it came out better than polytone. Did you buff it at all like Malcolm at wienerdogaero does, or is it "as rolled"

[Birdseyeview]

At this point it is all "as rolled". As a result, all but the yellow are high gloss but not the mirror smooth surface that is possible with a last coat sprayed on the surface and buffed after that, but its fine as is for me and my sensibilities. Light sanding in between coats was key to the way it ultimately turned out since tiny specks of dust tend to accumulate in each coat. I did all the painting last winter in my heated basement shop and my wife's very sensitive nose never complained once about any smell.

[109JB]

Getting the color on her. The gloss of the latex is definitely better than polytone. The white is really hard to tell but the blue has a little orange peel which was not unexpected. It is about what I was expecting and is in the perfectly acceptable realm for my tastes. If I ever decide to I could color sand and buff it but I doubt I ever will. Overall I would call it a success but in doing the fuselage I have learned a few things and will be modifying the process a little. The results that Malcolm at wienerdogaero.com gets can't be argued with, but at least for me a few changes to his process make it much easier for me. For my rudder and landing gear legs I made the following modifications which work very well for me.

I am starting to thin the first coat of primer a bit more than he recommends in order to make it easier to get more complete wetting of the fabric.

On the primer coats on the fuselage I used the wienerdoaero method and brushed each coat on sanding between each coat with 320 grit dry sandpaper. I still brush that first coat on, and on the landing gear I also brushed several coats, putting the primer on in one direction and tipping it at 90 degrees. Ultimately I went to spraying the primer on. The primer is still thinned and sprays nicely, leaving a slightly orange peeled surface. The orange peel is much easier to sand smooth than the brush marks from brushing/tipping. On my rudder I am spraying all but the first primer coat and it is going very well. You can get a smooth finish brushing and sanding, but it is a lot more work in my opinion. Spraying i was also able to reduce the sanding interval to 1/2 by applying 2 coats (one cross coat) at a time, waiting until the first coat tacks up and applying the crossing coat. I have also gone to wet-sanding with 400 grit which again is much easier for me.

Anyway, here is crappy picture of the airplane after the first cross coat of blue was applied and had dried about an hour.

27494

[109JB]

Got the final coat of blue on early this morning and just now got it unmasked. Came out really well. It has a little orange peel, but that was expected. Gloss is good and overall I am very pleased with the results. I didn't construct a booth so someone that did could probably get better results as there is a bit of dust specking because it seems my shop heater is set to turn on and blow stuff around exactly when I start pulling the trigger on the paint gun. Anyway, so far latex is a win for me.

2749627497

[Eric Page]

That looks great, John. Nice work!

[109JB]

Been a very long time since I posted in this thread. I have still been working on this one but not fast enough. Since I started this one I found a Glasair 1 kit with engine for a steal, and I also got hold of another Kitfox and repaired it, got it flying, and have sold it already. Need to get this one finished up so I can get going on the Glasair. Like I said, I have been working on this one and here is about its current state. I've done a couple more things that you probably wouldn't notice. Anyway, here it is right now. Stilll some work to do but getting closer.

32996

[klamath101]

Slightly off topic, I have bent up a few ripper shanks farming and never had any luck re bending them back to original, they always bend again in the same spot usually worse than the first time. Is there a special procedure for bending aircraft tubing during a repair to avoid that.

[jrevens]

Slightly off topic, I have bent up a few ripper shanks farming and never had any luck re bending them back to original, they always bend again in the same spot usually worse than the first time. Is there a special procedure for bending aircraft tubing during a repair to avoid that.

I don’t think so. 4130 N (normalized) is usually cold bent, and the bending process causes it to get a little harder and stiffer in the bend area (“work hardening”). Go slow to help minimize that. Respect minimum bend radius and use a good bender if needed to maintain concentricity when forming a new piece. When trying to straighten a bent piece during a repair, sometimes heat is required. If heated too much and cooled slowly it can become annealed and will have less strength.