Let’s install the wings.
You’ll need to have a helper, along with a way for each wing to rest in position before the lift struts have been attached.
You will also need a level, four 2″ wood blocks, and a drill / drill bits.
Before you do anything, ensure that the cabin of the aircraft is dead level, front to back, and side to side. If you have a taildragger, you’ll need to raise the tail using a chair, or wood blocks, or… whatever you choose. Work at it until your cabin is absolutely level. If you have a tricycle gear airplane, you’ll need to shim the main and/or nose gear of the plane until the cabin is level.
Once your airplane cabin is level, front to back, side to side, you may proceed.
Start by loosely placing the root of each wing over the wing carry through. Then place each wing tip on an adjustable stand, to support them while you work on them. We like to use an adjustable, clamping stand for each wing, but you can use whatever works. For instance, a solid stack of wood boxes, a short extension ladder with wood blocks… etc.
<insert picture of wing on stand>
The current version of the ultracub assumes a 32″ wing root to wing root spacing. This is achieved using the two inch wood blocks as spacers, between the cabin and the wing spars. This allows ample distance from the wing pin holes to the end of the carry through tube. Your setup will look like this:
Here’s another view of the setup:
A string line is run from wingtip to wingtip. We like to attach the line using masking tape. Also, assuming your work floor is level, it is useful to measure the height of the wingtip. If your floor is not level, the job is more difficult. It is useful to ensure that the floor is level using a ‘water level’. If it is not, the low side should be shimmed up using an appropriate board. For instance, if one side is 3/4″ low, put a 3/4″ thick board on that side, so that measurements will be equal on each wingtip height.
Here’s a photo of the string line running over the cabin area:
As indicated in the photo caption, raise the tips so that the gap is 3 1/2″. Also ensure that each tip is exactly the same height over your shimmed floor height. Measure, remeasure, and consult the opinion of a friend who is excellent with measurements.
Let’s measure the distance from the rudder post to the trailing wingtip.
There is not any exact value which is correct, due to slight variations in wing length and wing placement. What is important is that the distance from the rudder post to the wingtip is exactly the same for each wing, and that the leading edge is exactly square. You will need to push each wing forward or backward slightly to square the leading edge. You will need to ensure that each measurement back to the rudder produces an equal value for each wing. Do it slowly, carefully, and with the assistance of a friend.
If you did not attach your fuselage squarely to your cabin, you will have an unsquare setup. It will probably fly fine, but will look goofy to the observant. Don’t be goofy.
When all is square, the leading edge will look like this:
Now it’s time to drill four holes for the wing / cabin attachment pins, one at a time. Each hole is first drilled with a smaller diameter bit, then a hole of the final diameter. Since we use AN5 pins or bolts, they have a final diameter of 5/16″. The starting diameter that we like to use is 3/16″.
We also don’t like to drill through the *bottom* of the spar until after the hole reinforcement stud has been bolted in place into the carry-throughs. That is why the AN5 pin is shown resting in the following photo:
It is great idea to recheck the placement of both wings after each hole is drilled, and also check the dihedral by re-taughtening the string. Keep a keen eye on the positioning of the wings as each hole is drilled. Go slowly, get an experienced friend’s advice. You don’t want to screw this up.
The front carry-through gets an AN5 pin at each location. The rear carry-through gets an AN5 bolt.
After the four holes have been drilled, you’ll want to remove the wings, and drill the carry-throughs through with a bit of diameter x/16″. Each carry-through stud is then installed with an aluminum locknut on the top and the bottom. The stud must then be dressed with a file, so that the spar will fit back on. The wing can then be reinstalled, and the bottom of the spar tube can be drilled through.
When this is done, the AN5 bolt is bolted on the rear carry-through on each side; and AN5 pins are placed in the front carry-throughs.
You’ll want to mount the lift struts as soon as possible, so that the wingtip stands can be removed.
Incidentally, the taught string will now show a center ‘lift’ of about 3″, as opposed to the original targeted measurement of 3 1/2″. This is due the additional height of the spar roots over the carry-through stud.
You will also need to cut out the rear spars just enough to allow the wings to fold.
<insert picture here>
Next: Mounting the lift struts and jury struts