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Kit Building: Doors (Under Construction)

The instructions with the doors may be greatly aided by photos of doors on completed Challengers.  

Guiding Principles

The biggest challenge with the doors is getting started.  Don't be fearful - just wade right in.  You might drill a hole or two in the wrong place, but it won't matter in the end.  Doors are for looks and to keep the elements out - they are not structural per se.  Of course, you don't want them falling apart in the air and whipping through your propeller and tail section either, so be careful!.  

I got some very basic directions from Kris Falk that added to what came with the kit and just waded right in.  It wasn't all that hard, and I was pretty proud when builder/inspector Kris Falk said my door frames were the sturdiest he'd ever seen - even before the lexan got attached.

In our opinion, the majority of any mistakes you might make will be hidden by either lexan, paint, or a door hinge (if you drill a hole or two in the wrong spot like I did!  This is especially true if you order you plane with the tinted lexan (advised) and paint your cockpit and door tubes black.

Please bare in mind that the tubes for the doors are probably not perfectly identical from one kit to the next.  Close, but not perfect.  I doubt the airframe is exactly the same either.  This means that your doors will fit your Challenger.  They may not fit every Challenger.  Borrowing doors from somebody else's plane as a pattern may help you with the concepts, but not necessarily with measurements!  It may be good guidance, but they will not likely fit perfectly.

The trick is to build the doors on the airplane!

It's really not that hard once you get started.  Just allow yourself lots of time and don't get impatient.  Your first door might take you a day.  The other side will take half as long as the first.

One more thing, all airplanes change shape slightly once they're airborne and the weight shifts from the landing gear to the wings.  So guess what, the doors don't need to be built to exacting tolerances because they will fit a bit differently in the air anyways as soon as you lift off.

Getting Started

The first thing is to separate all the tubing that came with your doors.  There will be six matching pieces per side that are labeled with a felt pen showing numbers from 1 to 6.  

Assemble yourself some 1/8 inch drill bits, some packing tape, and a wheelbarrow full of patience.

You'll need to make yourself a few spacers - about 1/2 inch think is just right.  I used some cardboard.  Some folks cut the small square lexan samples provided with the doors into strips and use those.  

1. Install the Top Frame & Seat Belts

The instructions in the kit for this part are generally pretty good, although they are backwards relative to the front and back of the assembly.  Not a big deal really, and most door frames are built per the instructions (i.e. backwards!).  You'll just have to modify the front seat belt bracket positioning.  My Challenger door frame is installed per the instructions (backwards).

Here are some shots of the top frame - at the front, middle and rear.

My top door frame is installed exactly per the manual dimensions.

I moved the mounting for my front seat belt back a bit to clear the midpoint support on the door frame.  

You won't need to do this if you flip the door frame end for end when installing.

I learned this from a seasoned builder named Bruce Brown.

The Top Lexan

Wade right in - this stuff is actually very easy to cut.  Just scribe and snap - just like it says in the manual.

Use a straightedge and guide a fresh blade along the line you want to cut.

This piece needs some notching, so plan on tinkering for a bit!
Put the piece over a table edge and press - it will break nicely right along the scribed line.  I even found that with subtle adjustments I could even follow along on a curve.
Please note my flaperon control is disconnected there in this photo - I took it off so I could test fit the lexan.



That reminds me - I have to make another hole in the lexan to reinstall the flaperon control!

2. Install the Front Windshield Bow Tubes
I did a lot of fiddling to pick just the right spot.  Mine is pretty much where the longeron starts to curve inwards.  You can see the rear seat rudder pedal and gusset in this shot.  Note that the tube does not angle back when installed - it is hanging free in the photo as the top has not yet been attached.  Use a Cleco or Aluminum rivet as you have to take this off to do your fuselage fabric.

Note the judicious use of packing tape prior to drilling and clecoing!

Now, here's that same part at the top.  It has  here been trimmed for length and angle.

You can see the top tube in this shot as well.

Here is the bow tube and the top tube.

Note the use of felt pens ("Sharpies") for marking.  PLEASE, no pencils on aluminum airplane parts - pencils start corrosion and stress lines immediately on aluminum.

Cutting parts.  Just eyeball the angles, cut gently with a hacksaw and file edges smooth.  Go easy with the vice - you don't want to squish your door tubes!  You can just hold the tubing with your hand and saw it off.

3. Fit the Top Tube


Here's one of those chunks of scrap lexan as a spacer.  I used about three of them along the top of the door, and two in between the door and the front tube.

Here's the rear end of the top tube.

4. Fit the Bottom Tube
I used three strips of cardbox taped together for my bottom spacers.  This worked out to about half an inch.

Tape and cardboard!  A bit here and there, and the door frame holds together quite strongly so you can drill holes!

5. Fit the Front, Rear and Middle Tubes
You can see here about how much clearance I left between the bottom tube and the windshield frame (bow tube).  My front tube just went on top of the bottom tube.

6. All Taped and Ready to Drill
Just before I started drilling holes and clecoing (is that a verb?).  It is actually quite sturdy at this point.

You'll see the angles I decided to use and the placement of my middle tube.  All up to the builder!  I like parallel lines, so that's how I placed things (more or less!).

While doing a nice job is important, flying the beastie is the real important thing, so get building!

7.  Drill and Cleco
Did I mention I bought about 144 clecos and I still want more!

If I'm not mistaken, this is the inside of the top font corner.


This would be a shot of the top of the middle tube.
And the rear tube (at the top)
I only had this picture of the bottom gussets - this one from the rear - and on the bench now just before I started popping rivets.

8.  Riveting (Isn't it)
I didn't take too many pictures of this step, but if you're this far along, it is pretty hard to mess up.  

For one to many Clecos ...

   Remove  Cleco

   Insert Rivet

      Re drill a bit if rivet won't fit!

   Pop Rivet

Next Cleco

I elected to use stainless steel rivets.  Overkill I know, but my doors are very sturdy.  Will help when putting them on and off in prairie winds!


PS - yes that is one of two completed wings - ready for paint - in the background!

10.  Back on the Plane to install the Lexan

Reinstall the door frame on the hinges.  lexan installation is a a two person job - at least at the start.  One person holds the lexan, the other lines things up, and drills the first hole or two, and pops in the clecos.  Kris popped by this week and motivated me to get on with it.  We had the lexan on this door in about half an hour!
I held the lexan up and Kris went to the other side of the plane to make sure it was in the right spot (front to back).  We just lined it up with the hinge pins which makes it even with the top of the door frame.

Once we had the lexan pinned to the door frame with two clecos, we carefully removed the protective backing from the lexan in a strip where the door tubes line up.  This has to be done very carefully so as not to scratch the lexan.  We pulled a bit away and carefully sliced it with an Olfa Cutter a couple of inches away from the lexan.

We went right across the top, and then worked our way down with one hole and cleco in each vertical tube at a time.  This way, as the door starts to curve, one person can hold the lexan tight against the door while the other drills and clecos.  I would imagine that if you did all of one vertical tube or the bottom first, you could end up with a warp in the lexan and it would not fit tightly against the door tubes.

We went across the bottom tube last.

You might be able to see the small piece of lexan we used for spacing the rivet holes in this shot if you look really close.  Our spacing is about 4" which worked out very evenly on the door.

The Fine Print - Caution

Ideas, illustrations and photos are the author's own work and are for information only.  
Builders of Challengers should always follow the Quad City manual.

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