Javron Cub Building for Dummies

[pittsdriver]

Sam, I have the Airtex and it has a jumper wire on the board for the different baud rates. Nice installation. People don't realize the time it takes to figure out a seemingly simple problem.

 

[Sam D]

Interior panels

This is a bit out of sequence as fitting and covering the interior panels was one of the first things I did. But a friend had a question about how I covered the D-windows and I realized I didn’t post anything here about it. So here goes…

With the kit, I opted for the aluminum side panels. I ended up not using the two side panels on the upper baggage as I thought they were not necessary. Also, I had the upper baggage floor and rear bulkhead powder coated (you can see them in my ELT post and below). The remaining panels (lower baggage and cockpit side panels plus metal headliner) I covered with fabric.



The initial fit for the panels was accomplished when I was in Brainerd for the builder-assist week. After getting everything home, I did final a final fitting and registered more holes to match the tabs in the fuselage.

I did make an additional change with regard to the rear extended baggage bulkhead. The left side of the bulkhead was bent such that the side panel that connected on that side left little room for trim and trim indicator cables. So, I put a new bend in the rear bulkhead lip which pulled the side panel a little further in and provided some more room for the cables. Thinking about it now, months later, I could have just put a small block of plastic (sorry, don’t know the name!) to allow the cable to rub on if it made contact.

Here's a view looking down at cable clearance after I gave it a little more room:



Once the panels were all fit, I added markings to the back of each one to help me out later. These markings identified: a) which way is up, b) where the panel goes (and in what order – on top or not), and c) if the hole requires a nutplate (some holes were in spots where the panels just connected to each other and not to a tab on the fuselage).

As you can guess, I attend the Bill Rusk school of nutplates and used these throughout to accept #6 screws. One note, many of the tabs in the fuselage are too small for standard nutplates. After a couple of false starts, I found the small corner nutplates from Wicks were a good fit. Again, months later, I probably would have used the panel adhesive I wrote about earlier to affix a number of these nutplates. One further note, if you are going to use nutplates, make sure your rivets are nice and flush (especially if you are not going to cover the panels). If the rivets are a tiny bit proud of flush, you will get a slight warp in the panel when you screw it down. Its very tiny and probably not noticeable to almost anybody. But you’ll know!

As I noted earlier, I decided to cover the panels with fabric. I like the look. There may be some tiny sound dampening properties. And I don’t plan on carrying a lot of moose in the plane. I was able to find the fabric Bill Rusk used (Grey Heather tweed at Perfect Fit) and ordered 5 yards initially; however, I neglected to take into account that I was also going to cover my metal headliner and needed to order a couple more yards to finish things off.

I started off by gluing a test panel to: 1) check how the process goes; and 2) see how the panel will fit.

In certain areas where the panel slides into a channel (such as around the rear baggage door), if I wrapped the fabric around the edge of the panel, it was a TIGHT squeeze. So for those areas and the bottom edges, I terminated the fabric at the edge of the panel and cleaned it up with a soldering iron.

Gluing on the fabric is like working with Formica or similar – apply cement to both surfaces and let get tacky. Use strips of cardboard to allow positioning of fabric on panel. Slowly remove pieces of cardboard to get fabric and panel to adhere appropriately.


You'll notice the baggage area fabric is a little darker. I reversed the fabric in this area -- it is darker and appears more durable

My biggest dilemma was what to do around the D-window in the metal headliner. Since the glue comes off pretty easily with acetone, I did a couple of tests to try different covering methods, I ended up covering the side panel with one piece and cutting it flush at the D-window edge. I then glued a second piece to the D-window edge and butted it up against the first piece. Here’s how it came out.

Test gluing first piece:


Completed window


Finally, I started this thread asking about the felt used for the tubes and shown in the Piper drawings. As usual got some excellent suggestions. I ended up going with felt from McMaster Carr.

Hope this helps someone!

 

[Sam D]

Fitting the windshield

Fitting Windshield
The narrow-body Super Cub comes with the two-piece aluminum windshield trim strip from Univair (link just in case there is a need to order another one…). The wide-body comes with composite strips that I understand are much easier to install. This fact alone may push one to seriously consider the wide body! This step took me a long time. A big part of the time was learning how to stretch and shrink aluminum in a way that was acceptable to me.

I’ll outline my methods below in the hopes that they help somebody else out. I am by no means an expert here and there may be much better methods.
If you search youtube for “backcountry supercub windshield”, you’ll hopefully find the video laying out the process for the Backcountry supercub. It’s not exactly the same, but is a good primer.

Before getting into the process, I thought I’d lay out the main tools I used:

Bending block – I copied something similar I saw in Jay’s shop. This tool was indispensable for bending the trim strips using something other than the boot cowl. I made mine by taking a belt sander to a piece of 4x4. By the way, in the picture below, you can see something of a before and after in terms of the trim strips and how they end up a little more squared through the bending process.



Metal stretcher/shrinker from Harbor Freight – I agonized over purchasing these because they cost about $150 and I can’t think of another time I’ll use them besides this time. However, since I’d never worked with tools like this before, I didn’t want to borrow them from someone and feel like I had to hurry up and use them to get them back (that being said, if anyone wants to borrow mine, you’re welcome to them!) These are pretty simple tools and might need a little grease and attention prior to their use. At one point during the project, the shrinking tool was not operating smoothly until I took it apart, cleaned it up and added some grease – then it was good to go again.


Hammer and dolly set – So far, I’ve used this for a few purposes: 1) knocking down some of the ridges from the tooling above; 2) “stretching” the material when it only needed a little stretch; and 3) removing the bevel bend in the top of the front trim strip in order to put it in the stretch or shrink tool.



Inner/rear windshield strip

As I was contemplating writing this up, I was thinking of suggesting that the best approach to getting this right was to just rub your lucky rabbit’s foot and burn some sage. Then, I was heartened re-reading Bill Rusk’s write-up on the matter:

I wish I could give really good directions for installing the inner windshield strip but this one is tough.

Here is how I ended up approaching it along with some additional hints. I don’t know that this is the best way to approach it – just how I did it.

Step 1: Using a fabric tape, locate and mark the center of each trim strip.

Step 2: Measure back 5” from the top of the firewall and make a mark on the boot cowl (equally between the two rows of rivets). The front edge of the rear trim strip will go here.

Step 3: Reference line: Mark the top middle of the windshield and the bottom of the windshield. Place the windshield on the boot cowl. Line up the top middle mark with the center Piper channel and lightly clamp the top of the windshield in place. Line up the bottom middle mark on the windshield with the mark on the boot cowl from step #2. Secure the sides of the windshield as well using clamps. Trace the bottom of the windshield onto the boot cowl. This is to provide a general idea of how the trim strip will curve around the boot cowl.

Step 4: Carefully bend the strip to match the contour of the boot cowl

This (and step 5) is the hardest part and took the longest

Use a bending block as described above and take your time. I always tried to quit for the day when I found myself getting antsy about the results.



Don’t kink it – it’s very easy to put too much bending pressure on the strip if you’re not paying attention and have your hands too far apart. The fix for this (for me) was to only bend when my hands were very close to each other. Once you kink the metal, it will always want to bend at that point and making further shaping very difficult. I had what I’ll call an “incipient” kink that I had to be very careful with – and which impacted how tightly I could bend the strip on the left side.

Step 5: Once you’ve got the strip pretty close to matching the shape of the boot cowl, start thinking about how you are going to get the windshield-backing part of the strip to align with the windshield. I did this by taping down the trim strip “about” where it would go and then putting the windshield on. This gave me a general idea of how the windshield would meet the trim strip.

You will likely have “pooches” where the strip is sticking up at too sharp of an angle from the boot cowl and needs to relax a bit. For me, this was in the very front and right at the sharper turns on the sides. These areas need to be “shrunk”.

The shrinker essentially grabs the aluminum and squeezes it together thereby “shrinking” the material. In the case of the trim strip, shrinking the metal -- and I only put the wide end (i.e. the backing) of the trim strip in the shrinker or stretcher – either pulls the backing back toward the cockpit or allows a sharper bend of the trim strip while keeping the backing in the same place.

Below is a couple of pictures from when I was working on the front trim strip showing the results of using the shrinker (of course the second picture looks like I'm just pressing harder, but that's honestly not the case!)


I made a bunch of test strips to get a feel for how much pressure to use on the tool and what results I got.



There is a limit to how much aluminum can be worked and I tried not to find that limit.

Step 6: Drill holes

First, try to wait as long as possible to drill holes in the strip – there are a few reasons for this. First, as Jay taught me with the fuel lines during the builder’s assist week, it’s a good idea to work the part until its “happy” in its position. In other words, better not have it in place under stress. Second, you can crack the metal at the holes if you continue to work it significantly after the holes were drilled. Finally, after the 3[SUP]rd[/SUP] or 4[SUP]th[/SUP] time you re-cleco the piece onto the cowl, you will begin to experience loose clecos which result from the #40 holes beginning to wallow out. Not only do these clecos not do their job, you may be forced to move to a larger rivet (not the end of the world, but seems like it should be avoided).

The inner strip has a hole in the center and then additional holes every 2”. Using a #40 bit, drill and cleco the center hole and then proceed outward from the center. After I had a few holes on either side, I paused the drilling, took the strip off, and made bending adjustments before continuing to drill. Here's a picture of the inner strip clecoed in place with the windshield.



Also, don’t rush replacing the trim strip after you’ve made some shrinking or other adjustments. Take the time to make sure it is re-bent to fit nicely. Otherwise, you’ll be putting unnecessary stress on the clecos. Also, pay attention to a few-hole’s-distance beyond the hole you’re currently drilling to make sure you’re headed in the right direction before securing the strip.

You will also need to “flatten” the trim strip where the side of the boot cowl is essentially vertical at the end. Also, you may need to put a little more bend into the instrument panel as it may stick out a bit too much where the rear trim strip passes it. Finally, the backcountry video has a pretty good description of where the trim strip should end up (in terms of up and down location). For length, I cut it short of the “fuselage side” (not sure the name) so that the windshield could lie flush on the inner trim strip and the fuselage side (i.e. on the same plane)

Step 7: Final adjustment and riveting

Once you have the holes drilled and the strip clecoed in place, put the windshield on and check for proper fit with the trim strip. If there are gaps, those areas need to be stretched. If there are “pooches”, those areas need to be shrunk.

When you’re happy with the fit, remove the strip and countersink the holes for rivets. (Technically, I think the material thickness calls for dimpling, but I went with counter-sinking and like the results). The rivets you will be placing are temporary and you’ll be drilling them out. As such, use aluminum rivets. I was able to find 3/32” aluminum flush pop rivets from McMaster Carr.

For riveting, like the clecos, start from the middle and work your way out. I drafted my son to crawl into the cockpit and place opposing pressure from the inside of the boot cowl so that I could put some good pressure on the rivet and avoid any gaps in the riveting and get a nice tight fit.



Step 8: Place the windshield on and use a ratchet strap (attached to the strut fitting points). The picture in step 6 above shows the ratchet strap in place. Somewhere along the way, I drilled the top of the windshield to be able to secure it. But I left drilling the sides until the end. Also, I trimmed a little bit of the bottom of the windshield in a couple of places where it was hanging too low on the inner trim strip. I used a Dremel and made multiple passes with pauses in between so that the plastic never got too hot. Also, I ended up putting on and taking off the windshield a number of times and adjusting the inner trim strip until I has happy with the fit (I should say “happier” because as I write this, I am still considering one more stretch of the inner strip after I remove the temporary clecos.

Step 9: Fit the front windshield strip. This is a little easier this time around because the rear strip and windshield is already on – so you’re not guessing as much about fit. Essentially, repeat steps 4-6 with the front trim strip. (As you get to about where the final holes would be, go to step 10).

You’ll notice that the front trim strip has a slight bevel bend at the top. You’ll need to remove this in order to use the stretcher/shrinkers. I used the hammer and dolly for this.
The holes will begin one inch out from the center and proceed every two inches (so that each hole is between the holes in the inner strip). I just measured the center point between each inner strip rivet and drew a line outward. Then, I put on the outer strip and transferred the lines onto the strip to know where to drill.



Step 10: Side trim pieces. The side trim pieces are secured with five screws. In order to give some room on the backside next to the tube, I placed the holes 7/16” from the edge of the trim strip (and underlying fuselage). I put the first hole about an inch down from the top. The bottom home, if all goes well, will marry: the outer strip, the side trim strip, the windshield, and the fuselage side (see picture below). After these two, I placed another three screws equally placed down the trim strip.

 

[pittsdriver]

Sam, Instead of going through all that work it is very easy to lay up a composite fairing. I get the windshield fitted and lay up the fiberglass cloth and resin directly to the windshield and cowl over a release such as duct tape. Total time to fabricate is an hour or so for a fairing that fits perfectly.

 

[Sam D]

Sam, Instead of going through all that work it is very easy to lay up a composite fairing. I get the windshield fitted and lay up the fiberglass cloth and resin directly to the windshield and cowl over a release such as duct tape. Total time to fabricate is an hour or so for a fairing that fits perfectly.

Funny you should raise this. I thought of this very post of yours often during the process!

 

[pittsdriver]

It is a pretty easy process but I've been doing fiberglass starting with surfboards when I was 12. Working with composites is a good skill to have in your bag as there are all kinds of things you can do even on a Cub. Here is a carbon fiber instrument panel overlay. Something to think about for the next airplane you build. By the way that is the nicest aluminum fairing I have ever seen on a Cub.

 

[Bill Rusk]

Sam

Awesome write up. THANK YOU!!. That is one of the most difficult parts of the whole build. That and the lower cowl. I have begun to tell folks to do that part during the builder assist with Jay. ie get him to help you with the really hard stuff. Great job. It will look fantastic. I also agree that if you have some fiberglass experience that way will yield a perfect trim strip as well.

Thanks for posting

Bill

Oh yeah......UHMW (ultra high molecular weight) is the plastic stuff that works great for high abrasion areas. You can even get it in a "tape". I used it on the bottom of my fuel pod where the water rudder retract cable just barely touches the pod. Great stuff in a lot of places. Great for Ski bottoms too

 

[Sam D]

Fitting wings (part 1)

Fitting the Wings
I took the project to the airport and made it look “planey”. Here are the major tasks I did to prepare and install the wings and perform other related tasks:
Preparation – Initially I thought I could hang the wings in my driveway before realizing all the stuff I’d need to do. So, I needed to have it in a place it could sit with the wings on for an extended period of time. And that was the airport. The project was at the airport for about a month during this process.



Before heading to the airport, I did some basic prep at home including test fitting all the hardware and removing powder coating from bolt holes where necessary.
I also prepped the lift struts. The lift struts are extruded aluminum into which you will bolt blocks at either end. Jay suggested applying zinc chromate/phosphate to the inside of the struts where the blocks are inserted. I did that and tried to spray a little further into the strut.



Once the strut interiors were primed and dried, it was time to insert the blocks. For the top blocks, the portion that bolts to the wing will be angled coming out of the lift strut. The block on the top of the forward lift strut should be turned so that it angles back. The block on the top of the rear lift strut should be turned so that it angles forward. For the bottom block for the forward lift strut, the threaded hole for the fork is off-center. You will need to position this block in the strut such that, after the forks are threaded and the struts are attached to the fuselage, the top of the front and rear strut are flush with one another (the bottom of the front strut will drop down a little below the rear strut).



I put the bolts in the struts such that the heads would always face toward the wing / up. For torqueing the nuts on the lift struts, I used guidance on this site (which also agrees with AC43-13). (The main consideration here is which way to orient the heads of the bolts. Of course, they all need to point the same direction. For airflow purposes, I chose to have the bolts arranged such that an angle of the hex head of the bolts faces into the wind. I’m sure this will make the plane much faster!)
Once I got the project to the airport, I removed the flaps and ailerons, which were attached with temporary hardware by Javron, and the fuel tanks.
I also built the wing stands suggested by EAA (EAA link). The Javron wing stand is good for shipping but not as good for taking on and off. It was nice to have a ready spot to put the wings.



Wing installation – here’s the process I followed:

• Prep struts below as the front strut will go on immediately after wing is attached
• Re-check all attach points with hardware to confirm everything fits

• 3 people – one at wingtip and one at each wing root attach point. Wingtip guy holds it up while wing is fit and strut is attached (consider getting this jack stand from Harbor Freight to give the end guy a break)

• Can temporarily secure/align holes with screw driver
• Wing attach bolt may need light tapping with rubber hammer
• While prepping for next step, can quick clamp 2x4 vertically to compression strut to hold wing (repeat this step later when first wing is on so that plane doesn’t tip due to imbalance)

Attach lift struts

• Prep
  • Per Jay’s suggestion: to pre-set front strut for proper dihedral: screw bolt onto fork as far as it will go. Screw fork into block such that space between bolt and block is .375” - .400” then tighten bolt onto block. (this was later adjusted, see dihedral and washout adjustments below.)
  • Check fitting on upper end of strut (this hole might be a bit small)
• Raise strut to match angle of how it will finally fit (BCSC manual has pictures of this)
• Angle has to match just right so that bottom fork can go on strut attach fitting
• Attach bottom first then top
• Clamp vertical 2x4 to compression strut so that plane won’t tip with one wing. Wing will stay on airplane with just front strut on
• Repeat process with other wing and remove 2x4 off first wing
• Repeat process with rear strut
• Setting washout:
  • Javron sets their angle of incidence slightly higher than stock. Therefore, you can’t use the stock rigging instructions for washout. The following process was suggested by Jay:
  • Using a digital level, zero the level at the wing root rib
  • Go out to #15 rib (round wingtip) and level with 1/8” spacer at 30” (similar to stock rigging which uses a 3/8” spacer) – should see 1.8* on digital level (I modified this slightly and through some trigonometry, accounted for the 1/8” spacer by changing the angle to 2* (2.04 to be exact)
• Dihedral and washout adjustments – I had to make some adjustments to my initial settings. When I first set the wings, the measurement of the strut forks noted above was .400”. This resulted in a 4” distance from a string strung wingtip to wingtip to the spar at the wing root. After a couple of adjustments, I ended up with the measurements at .330” - .340” and the string was now 3.25” to the wing spar.

• For washout, I measured about a million times and finally got both wings to the same washout at 2*.

Run cables

• Aileron cable behind front spar goes overhead in fuselage – this cable stays in wing during cover
• Once you get cables on and can move stick, note where cables will exit the fabric (so after cover, you know where to cut holes for exit points) Jay measures distance from front wing strut
• Gas tank – there are two fairleads that go in here. Put those guides in now (permanently). Make sure snap rings are on gas tank bay side so that they can be removed if needed later. (For fun, see how many times you can drop these while trying to put them in…my PR is five times)
• Lift strut guides and fairleads – install these temporarily so that you can get a feel for the aileron movement with them in (see if there is any binding, etc).
• Flap cable – the ends of this cable need to be swaged (this task is left with builder to help meet the 51% rule)
  • Using mechanic wire, secure “splitter plate” of flap cable in fuselage. First, attach flap handle and cable to flap handle. Make sure cable is taught all the way to splitter plate. Then secure splitter plate to fuselage using mechanic wire (can pull forward to seat belt attach tube and attach to sides as well). Important to make sure plate is centered in fuselage (so that cables are equal length to flaps and, therefore, apply equal force to flaps when used.

• Screw ends of barrels on turnbuckle – make sure two threads showing on each side. Put up in bell crank.

• Take crimper, come up from bottom, pull it and pull sleeve against thimble, one guy runs swedge and one guy runs cable. Follow AC43-13: One crimp in middle to set. Crimp two is side closest to eye. Crimp three is farthest from eye.
• Aileron cable – overhead has some plates to hook together. 3” long. Hole on each end.
• Aileron stop on torque tube – can unscrew these stop bolts to the point that torque tube is held straight up and down. I had some trouble with the getting the floor aileron pulleys in the housing – they were a little tight. I made a simple spreader with a bolt and some nuts with very good results.

• Once the cables are set, I took lots of pictures and compared my measurements with the Piper wing covering drawings to note where cable would exit the fabric.

Part 2 will cover fitting the wing root fairings

 

[DENNY]

Note the angle to the top aileron cable has as it exits the top of the wing. The grommet and cover that is on top of the wing has to match that angle. I see lots of cubs that had the cover slot placed perpendicular to the false spar and had to be cut out to match.
DENNY

 

[Dan Gervae]

Your project is astounding....your attention to detail is spot on! Nice work! If I build another Cub, it will be a Javron...

 

[Sam D]

Fitting wing root fairings

Fitting wing root fairings

First a little background – the Javron kit comes with a four piece wing root fairing set per wing: rear, top, bottom and front. My understanding is that the Javron wing root fairing does not have the “tightening” mechanism of standard cubs. I believe this is due to the size of the flaps (i.e. the extend all the way to the fuselage). Therefore, you don’t have the cinching action of tightening the fairing. As a result, you need to secure the fairings a bit more. There are many ways to skin this cat and the way I did it may not be best for you but here goes...

I started with the rear fairing. Jon Lee was good enough to stop by Jay’s shop and take a bunch of pictures that really helped show where things got attached. In the photo below, you can see how I attached this fairing. I also used to tape to simulate the fabric covering to ensure I had clearance. On top, I notched the fairing where the skylight trim strip comes across – this is that the top fairing strip will overlap on a relatively flat surface. Finally, you’ll note that I made a small notch in the fairing where the fuel line exits the (future) fabric.



The top fairing gets secured to both the butt rib and the piper channel on the sides of the skylight (thereby securing the skylight as well in this spot). If you want your holes on either side (wing side and fuselage side) of the wing root fairing to line up, you’ll need to locate the screws on the wing side first. The fairing is intended to butt against the fuel tank cover (not overlapping) on the butt rib. However, the butt rib has rivets where the lip for the fuel tank cover is attached and flutes to create a bend in the top of the rib. Given the rivets and the flutes, you are limited to the spaces between these rivets and flutes to locate your holes to attach the wing root fairing.

The next photo shows the placement of the right top wing root fairing. Both of the rear clecos go through this fairing as well as the rear fairing.



Here is a view of the left side rear and top fairing and how they are attached.



Here is a view of the bottom right fairing and how it is attached.



You may notice that around the hinges, there is a lot going on. And trying to locate nutplates in here was going to be a challenge. So, I made a nutplate “subpanel” if you will.



The front fairings probably took me more time than the others combined! I started with poster board templates. Below is a picture of one I reversed in order to give me a straight line to lay down a masking tape guide.



I attached the poster board and cut it down until I had an even gap to the windshield (and a mostly pleasing symmetry when viewing them head on). Keep in mind that the required gap changes based on the orientation of the fairing to the windshield – at the top, it lays on top of the windshield (almost parallel), and at the bottom the fairing is perpendicular to the windshield. I then used the poster board as templates to modify the front fairings provided. Here is a picture of it in place (should have taken more pictures!)



I then took a ton of pictures of the control cables and where the would exit the fabric – I hope I took the right ones and answer my own questions when covering!
One final note, in the picture above, the front right hole ends up in a very difficult place to put a nutplate. I crafted the simple tool below that allowed me to put 3M adhesive to the ears of the nutplate, secure it and fish it into the recess of the frame and then “grab” it with a screw. Seemed to workout ok.



Until next time, here is a picture of my daughter Sofia hard at work at Marty’s fabric covering seminar at Oshkosh!

 

[Sam D]

Under-seat bulkhead

Under-seat bulkhead

This was a pretty straightforward project. Underneath the rear seat, there is a gap. I believe the original Super Cubs have a leather/fabric panel here to make it look nice and prevent (somewhat prevent?) items from dropping into the nether regions of the plane. I decided to make a simple aluminum panel to cover this area which would be screwed into the floor and would bend over the rear seat cross tube at the top.

First thing I did was make a template out of poster board. I then cut holes in the sides for the rudder cables and a hole in the center for the elevator cables. This center hole comes out somewhat triangular because the bottom cable swings more with the movement of the stick/torque tube than the upper cable.



The most challenging part of making the template was figuring out the right height to make it so that it was flush with the floor and folder over the cross tube nicely. I finally realized that the floorboard has a slight bow to it – so a straight-line bend was not going to give you the same distance at all points. (Note: I pretty much did a straight-line bend and it came out fine in the end).

I then transferred the template measurements over to the aluminum and cut out the holes before bending it.



I then bent the panel in a brake. However, because of the tight bends around the cross tube, I was only able to “start” the bends which I finished as follows. (If you meet my wife, be sure to tell her THAT'S why I keep that old wood around! )



To secure the bottom of the panel to the floorboards, placed the panel in position and located 4 holes evenly on each side of the center cutout. Before locating the holes, I also ran some tape on the topside of the floorboard to mark where the diagonal cross tubes are under it…and avoided those spots. Once the holes were drilled, I used the same tee nuts I used for fastening the hinge on the rear seat. If you imagine screws instead of clecos, here is what the finished product looks like:



Edit to add: it was suggested that you could also attach the bulkhead to the floor behind the bulkhead (i.e. make the bend 180* in the other direction). I like this suggestion and would probably set it up this way if doing it again. It would make the presentation a bit cleaner.

 

[Sam D]

Wing Stands

Wing Stands

I’m turning to working on my wings. I don’t have a rotisserie (yet? Still hoping to borrow instead of buy) and didn’t really want to set the wings on the ribs. In Bill Rusk’s Javron wing building thread, it looked like there were some wing stands, so I stole the idea and made some out of wood:



I didn’t realize the wing root side is actually at different levels (should have looked at the stand the wings came on!) but this was easily fixed by drilling a second hole.

 

[Sam D]

Landing/Taxi Light Installation

Landing/Taxi Light Installation

For the taxi/landing lights, I opted for two-single lights (one in each wing) in order to have wig wag. I’ve seen these lights located in a number of positions on the wing and I chose the somewhat standard position of the first bay outboard of lift strut attach/N-brace bay.

If you order the light kit from Javron, here’s what you get (well you actually get two of everything shown, except the hardware. You also get the lens for the light(s). Mine was a single piece that I needed to cut in half but this may not be common as I originally had a single light unit and opted to change to two units.



Here is my single lens before I cut it in half. I was trying to get the cut just right on the center, but as you will see later, these pieces are quite a bit larger than you will actually need.



Marking the opening

First, I marked where opening goes on leading edge as follows:

• Center: Center line was located equidistant between leading edge screws into ribs (my positioning)
• Top: 4 11/16ths inches back from bend on leading edge -- hook a tape measure over (as suggested by Jay)
• Bottom: 4 ½” back from leading edge bend on bottom (also suggested by Jay)
• Side: Measure width of the opening of the bezel (the frame that will hold the clear plastic lens on the wing). Add one inch to this measurement (1/2” per side) (Jay again)

Just a couple of side comments here. First, keep in mind that the bottom of the wing will be what’s visible when the plane is sitting on its gear. If, like me, your wing is sitting on a table at this point, the bottom of the wing will be difficult to get to (and therefore easy to mess up!). Also, you really can’t measure too many times. Keep measuring the top and bottom and sides and test fitting the bezel until you are comfortable that everything is where it should be (I aspire to be so good that some day I’ll only need to measure twice before cutting once!)



For drawing nice even lines on the sides, you can use a strap of aluminum. A trim piece you’ve previously fouled up makes an excellent tool!


Cutting the hole

Then, I said a little prayer and proceeded to cut into the leading edge as follows:

I drilled the corners first and used a ½” step drill (after drawing the holes on the leading edge). I also used the step drill a little like a router to make a slightly larger area to cut into. After this, I used the snips to cut out the hole (starting about ½” from the line and getting closer on successive passes) and finished with a combination of a file, Dremel with sanding bit and sanding block to finish it up.



Installing the channels

There are airfoil-shaped channels for the sides and straight channels for the top and the bottom. Each channel has a narrow edge (3/8”) and a wide edge (1/2”) with a joggle or step in between. The channels will step down toward the center of the opening in order to hold the light cover. By looking at the airfoil-shaped channel, it becomes somewhat clear that the narrow edge will go under the leading-edge skin while the wide edge holds the light cover.

Based on Jay’s advice, I located the side channels as follows:
Straight channels (top and bottom) will go in first. They will be riveted in place with the rivets that will also hold the nutplates for the bezel. (Note: if you’re following the Backcountry manual, this is a departure from their approach). The bezel will only be screwed in along the top and bottom.
Plan on 4-5 nut-plates evenly spaced across the top and bottom of the opening. Further, plan on the 2 outer-edge screws aligning with the vertical line of rivets that will hold the side channels in place.

I laid out where the channel pieces would go on the leading edge. Based on that, I located the holes 3/16” from the outside edge of the channel pieces. I drilled the holes in the leading edge and then drew lines on the center line of the 3/8” edge of the channel strips. I then sighted this line through the holes already drilled to position the channel strips under the holes and drilled them out.



Cutting the light cover
At this point, I positioned the light cover over the wing opening and, using masking tape, marked the opening on the cover.



I used a Dremel to make the initial cut on the lend cover (with multiple passes so as not to “linger” in any one spot and overheat the plastic). After the initial cut, I used a sanding block to get the fit just right.



Installing the light assembly

Before installing the side channels, the opening is at its largest, so it’s a good time to install the light assembly. Each assembly has two “plates” with large circle where light goes. One of these plates has a longer flange on two side with two holes. This is the back plate and those two holes are to connect to the side pieces. The other is the front plate which will screw into the back plate holding the light in place. For this step, you don’t need to assemble the front plate with the light (but I did). The side pieces have one hole above a series of holes in an arc. The series of holes is to be able to adjust the light. A taxi light will be tilted farther down so that it does not point into the sky when the plane is sitting on the ground. Also, I installed nuplates on the back plate to make it easier to attach the front plate in the future.



Finally, you’ll need to decide whether the flanges of the side pieces point out (i.e. are visible on the side of the assembly) or point in (are hidden behind the assembly). I chose to keep the flanges pointing out to make them easier to get to.

Once I put together the light assembly, I positioned it against the spar – both centered in the hold and slightly above the bottom spar cap. I then temporarily installed the channels to confirm that the light assembly had adequate clearance. Then I drilled out the holes. I found the easiest way to do this was to use a 12” #28 bit.



Installing channel strips

I riveted the side strips first so that I could confirm that when I positioned the bezel for drilling, I could confirm that it covered the sides with the channels installed.

Drilling bezel

Before installing the top and bottom strips, I added two layers of masking tape to simulate cover and paint. I also drew an extended line across the holes I had drilled in the top and bottom to make sure they lined up right on the bezel. Then I positioned the bezel for drilling and used a 90* drill to back drill the holes



Nutplate install

My last task was to enlarge the #40 holes in the top and bottom to accept #6 screws and drill and install nutplates (to also secure the channels)



Eventually, I will probably have the front light plate powder-coated black. And I will repeat this whole process on the right wing…

Hope this helps.

 

[soyAnarchisto]

I love these threads so much. Erry time I lift the carpet, or lie on my back and look up behind the panel of my 66 year old aereoplane, I dream of building my own experimental super cub!

 

[Jlee]

Great write up as always Sam!


Sent from my iPhone using SuperCub.Org

 

[Bill Rusk]

Awesome write up Sam. Please keep it up. And THANK YOU!!

Bill

 

[Sam D]

Pitot Tube Bracket

Pitot Bracket

I went with a very basic pitot tube from Aircraft Spruce (https://www.aircraftspruce.com/catalog/inpages/unheatedptubes4.php?clickkey=5714). Then I had to figure out where on the wing to put it. Here is a useful thread describing location: https://www.supercub.org/forum/showthread.php?32722-Pitot-Tube-Location

In the end, I decided to locate it on the rear spar just outboard of the jury strut. As Web points out in the thread linked above, the bracket is part number 11580-00. But there aren’t (or I couldn’t find) very good drawings of it. So, I used the opportunity to mess around with Solidworks and create a design. If anyone is interested, I’ve attached a pdf of the final design. I don't think I can attach the Solidworks file (if anyone is interested, I'd be happy to send it to you). I went through a number of design iterations before getting the angles right – one of the benefits of using a CAD program.

Once the design was done, I printed it out (after confirming the scale was right) and spray-adhered it to some aluminum. Then I drilled the holes and cut the piece out of the aluminum (I used the pitot tube itself to match drill the screw holes). Before bending the piece, I installed nutplates as it would have been a little tight after it was bent up. Finally, I bent it into position then located it on the spar (making the bottom flush with the bottom of the ribs) and match drilled the spar.

 

[skywagon8a]

Pitot BracketView attachment 58353View attachment 58355

Very nice, but where is the static port? This is a pitot/static system. Both air sources are required for accuracy. Look at the two ports on the back of your airspeed indicator. One is labeled P and the other is S. The S is also connected to the rate of climb and the altimeter instruments. The location of the S​tatic port on the airplane effects the accuracy of all three instruments.
This is the pitot tube you should have with the static ports attached to it. https://www.aircraftspruce.com/catalog/inpages/pitot15144.php?clickkey=3046038

 

[pittsdriver]

I've used these on my last three builds. They work great and are easy to mount. I use push to connect fittings for the whole pitot system. The will even slip on the aluminum tube on that pitot tube. They work great and make things simple. The plastic ones work fine and are much lighter than the metal. You can get them local in the sprinkler supply section as they are used for drip irrigation. www.mcmaster.com/tube-fittings/for-tube-od~1-4/

 

[wireweinie]

I've used these on my last three builds. They work great and are easy to mount. I use push to connect fittings for the whole pitot system. The will even slip on the aluminum tube on that pitot tube. They work great and make things simple. The plastic ones work fine and are much lighter than the metal. You can get them local in the sprinkler supply section as they are used for drip irrigation. www.mcmaster.com/tube-fittings/for-tube-od~1-4/

Have you pumped these up or down on a test box to see how 'gas tight' they are? There are strict limits for leaks on the pitot and static systems.

Web

 

[pittsdriver]

They are designed for high pressure air systems so yes I think they can seal tight. I have used them on 6 or 7 airplanes and they do not leak and make for an easy install.

 

[wireweinie]

How did you test them for leakage? If they seal properly then great. But if you just installed them without checking the system for leaks then you can't trust your airspeed or altitude readings.

Web

 

[pittsdriver]

The same way I test any other pitot static system with a vacuum gauge. Why do you think these fittings aren't any better than compression fittings. These are way better and you can pop the line apart any time you want.

 

[fancypants]

I really like those quick connect pneumatic fittings. Much easier to deal with than the nylon compression fittings. Festo is a good brand.

 

[wireweinie]

The same way I test any other pitot static system with a vacuum gauge. Why do you think these fittings aren't any better than compression fittings. These are way better and you can pop the line apart any time you want.

As long as they meet the leak test criteria then have fun with them.

Web

 

[Sam D]

Very nice, but where is the static port? This is a pitot/static system. Both air sources are required for accuracy. Look at the two ports on the back of your airspeed indicator. One is labeled P and the other is S. The S is also connected to the rate of climb and the altimeter instruments. The location of the S​tatic port on the airplane effects the accuracy of all three instruments.
This is the pitot tube you should have with the static ports attached to it. https://www.aircraftspruce.com/catalog/inpages/pitot15144.php?clickkey=3046038
View attachment 58357

Thanks for the feedback. I was planning on venting the static port to the cabin. However, in seeking to support my response to your comment. I was coming up somewhat empty. I thought Piper had done that with the supercub but it appears they stopped the practice at some point. The final nail in the coffin was this from Tony Bingelis in The Sportplane Builder:

Some builders (ugh) install the altimeter and the vertical velocity indicator with absolutely no static line connections. They are merely attached to the instrument panel. The instrument's static opening in the rear is left open to the cabin or cockpit atmosphere. This is sloppy practice even for a strictly VFP Putt-Putt, and provides, at best, very nervous and inaccurate gage readings.

So, here is the new and improved bracket. Sadly, I was unable to use the original bracket as the screw holes are different between the two types of pitot tubes.



Thanks again for the input.

Sam

 

[wireweinie]

You do what you decide is best but that line he gave you about sloppy practices and inaccurate readings is a load of crap. I can't swing a dead cat without hitting a fabric airplane with no static ports. And some of the pilots of these aircraft are the best in the world at operating in remote and dangerous geography and would tell me in no uncertain terms if the instrumentation I just installed was inaccurate.
If it makes the recertification tests easier, I'll plumb the static connections on the instruments/encoders together to give one connection point for the test box. But I will still leave it under the instrument panel unless there is already an external static port installed.

Web

 

[pittsdriver]

That pitot static tube works great. I have them on the last three Cubs I built. Venting into the cockpit causes inaccuracies. Put an inspection hole next to it in case you ever need to service it. It is also easier to put it on after covering.

 

[Bill Rusk]

Vented to inside and based on my GPS airspeed is within 1 MPH. Keep it simple. You are not building a rocket ship to go to Mars, just a 100 mph Cub. Just my opinion and all that rot.

Bill