Just like the plans say….”This is the big one!” This is the chapter in which the wings are constructed. It’s hard to believe that just about half of the airplane (at least from appearance anyway..) will be built in about 200 hours.
First, some jigs are made that will hold the foam in place for the various layups. These jigs, like so many aspects of this project, are simple yet ingenious in their design. Each jig is made of 5/8" particle board and a template of the wing is laid out on the jig and cut out. The jig is then cut into 4 pieces per plans and held together with small tabs. This is so the jig can be assembled in various pieces so the many layups can be done.
Once the jigs were constructed, I ordered the wing foam cores from Featherlite. Many builders cut their own foam cores, but since this truly is a “one man show”, I didn’t have anyone to hold the other side of the hot wire saw. I also figured that these are critical airfoils, so I had the experts do them.
The first step is to cut out the area where the wing attach bolts will go. This was simple because you are working with foam. Ten minutes with the Dremel and those were complete.
Next, the aluminum hard points are installed and the shearweb layup goes over the top of them.
After the shearweb is done, the wing is laid down with the bottom facing up. Now the sparcap, nav2 antenna, and bottom wing skin are done.
The jigs are once again assembled and the wing is flopped over so the top can be worked on. The top is pretty much the same as the bottom with the exception of a thicker sparcap and wing skin since the top is in compression. The rudder conduit is also carved out of the foam and a small plastic tube is embedded. The rudder cable will travel through this conduit.
The trailing edge “fishtail” is trimmed off and this allows for a perfect glass-to-glass trailing edge that is straight.
Once the top is completed, the inside wing ribs are constructed.Here is the wing root rib that will eventually house the aileron belcranks and push rods.
The ailerons are cut out of the wing’s trailing edge, but I will hold off on doing this step until some cash can be saved up. On to the left wing………..
With the completion of the left
wing, it was time to get serious and start
to make this project look like
something other than my retirement fishing boat. This step involved coaxing Vaunda to park her
car out in the driveway for about 3 days because I needed all 35 feet of our tandem
garage. I wasn’t as brave as a fellow builder though.
Yes, that is his kitchen/family room that he used for the same operation! He said the cold weather was the reason for doing it in the house. Do you have any idea how many aluminum shavings are produced from a 5/8” hole saw going through 1.5” of aluminum???? 3 times!!!!!
This step is probably the most critical of the whole building project. The wings have to be set at 0 degrees incidence in relation to the main spar. This will guarantee that the main wing will continue to fly long after the canard has stalled. This is the main safety factor of the canard design. For how crucial this is, the plans make it very easy to do. I took the advice of Wayne Hicks and used the wing jigs for support. I fabricated 4 simple jigs to support the main spar in place. Lag screws were used and made adjusting a simple and precise means of accomplishing the task.
These two pictures show the front and back of the jigs with
the lag screw adjustments.
Walk like an Egyptian……….
I fabricated a simple water level…….the same thing the Egyptians used to accurately build the pyramids so long ago. As you may or may not know, water always seeks its own level. So all I did was place one end of the tube level with one wing, placed the other end of the tube at the other wing tip and shimmed the wing until it was even with the water level. This was used to verify that the jigs were level over the 28 foot wingspan in a garage designed to allow water runoff in the event of a flood. Needless to say the left tip had to be shimmed about 4.5” up to be level with the right wing tip.
Here is the water level measuring the right wingtip jig.
The only problem with this whole thing is there is more than one factor that must be accounted for. Incidence is the most important, but we also have to account for dihedral. Dihedral is when you look at a plane from the front and the wing tip is higher (or lower) in height than the wing root is. This plane uses zero degrees dihedral so the tip should be the same height as the root. We also have to account for sweep, or how far back the tips are in relation to the root of the wing.
I quickly found out that as soon as you make an adjustment to one, it throws another out of whack. After about 3 hours of chasing measurements around, I came up with a very good setup. Once this was accomplished, I did as another builder states “Took the leap of faith” and drilled my first hole. The plans call for a 5/8” hole to be eventually drilled into a 2”X2” wing attach plate. Doesn’t sound hard, but due to small mis-measurements in building the wings and spar, you have to wonder. You’re drilling blind into some pieces with only the measurements from the plans to go on. In the end, everything was perfect! The plans allow for shimming of a wing with washers once the plane is completely assembled. To make a long story short, over the 28’ distance, I will have to add one washer that is .040 inches thick (just over 1/32”) to the left wing. I find this truly amazing to achieve this kind of accuracy for something that is built in a garage by a “first timer”. That is how well these plans are written! I built the spar last year, (with no reference to the wings) and stored it. Built the wings this year without ever looking at or measuring the spar, put all the pieces together over Labor Day, and they fit with that kind of accuracy! I don’t know about you, but it blows my mind!
Well, here they are.....all 28 feet. In the picture on the right, the boards attached to the wing are what set the incidence. A level is placed on the board and the wing is adjusted until it reads level. Once the holes are drilled, another board is bondoed on to the main spar at 0 degrees. When the spar is put into the fuselage, I will use this board to confirm the spar is level in the fuselage.
Next on to the ailerons………..
The next part of the wing construction I undertook was fabricating the flappy things that make the plane bank left or right. The plans call for the ailerons to be done before attaching the wings to the main spar. I opted to do the main spar step before the ailerons in case I had screwed up a wing and needed to scrap it. No sense doing the extra work on the ailerons on a wing that was no good. Fortunately, everything went to plan in the previous step.
The scary part now is you have to cut the aileron out of a good (rather expensive both in labor and money) wing. First I laid out the cut lines for the aileron according to the measurements in the plans. Using a dove tail saw, I carefully cut the aileron out from the wing.
The left picture shows me cutting out the aileron. The rear spar layup is shown before final trimming on the right.
The next step involved removing foam from the back section of the wing so the rear wing spar can be laid up. Additional reinforcing layups were done where the aileron hinges would eventually be installed.
Once all the proper reinforcements were applied to the wing, work turned to the aileron itself. The most important step involved the installation of the counter balance. There have been some cases of flutter reported because of improper balancing of the ailerons. This usually happens when an owner who is not the original builder repaints the plane and doesn’t rebalance the ailerons. Hinge brackets are also installed into the forward edge of the aileron. These are what the hinge will be riveted to when they are installed. A short portion of the control system is also embedded into the inboard side of the aileron. A control torque tube will connect to this piece that will allow it to be controlled from the side sticks in the cockpit. Once these steps have been accomplished a lay up is done over the forward edge of the aileron to close it out.
In the left picture,the aileron is mounted trailing edge down in some scrap foam so the counter balance can be installed. I am cutting the foam out of the aileron for installation of the torque tube in the right side picture.
The next step is to first temporarily install the hinges into the wing. The plans call for bondo to be used, but I opted for clecos (temporary rivets) that we used years ago during racecar fabrication. They are infinitely reusable and install and remove in less than a second. I highly recommend them for this step.
Next the tricky part comes, attaching the aileron to the hinges. You have to jig the aileron in place so it lines up perfectly with the wing on the sides and trailing edge. Once this is done, there is no way to hold the hinge against the aileron. Numerous ideas have been proposed over the years, even using soft earplug foam on the back of the hinge to “push” the hinge tab into place on the aileron. The one that I opted for and worked great was using a couple of hacksaw blades stuck down between the hinge lines to hold the hinge against the aileron.
The picture on the left shows the hinges being attached to the aileron. The photo on the right shows a close up of the clecos and how the hacksaw blade fits between the hinge to hold it in place against the aileron.
The last step just involved making the hinge attachments more permanent. Nutcerts are installed on the back side of the hinge/wing side of the hinge and a screw is installed from the top of the wing. The aileron half of the hinge is riveted to the aileron. To remove the aileron, simply unscrew the wing hinge portion and remove the aileron.
Here the aileron is complete with the exception of the final install of the screws and nutcerts.
The same steps were completed for the left wing.
Well, with this last step of completing the torque tubes and belcranks, brings an end to the big chapter. Big in amount of labor involved and in the physical size of the pieces made.
This last step involved a plans change. The original plans call for a ¼” piece of phenolic block to be placed in the wing root for a bearing surface for the aileron torque tube. An inexpensive nylon bearing has been found and doesn’t loosen up over time. The phenolic block tended to get sloppy causing play in the control system. This change is approved by Nat Puffer.
In the left picture you see the
bearing support surface I made at the suggestion of Jack Wilhelmson,
out of 6 plies of bid. I riveted nutcerts to the back of the layup
and drilled holes so the bearing can be bolted to it. This allows the bearing to be replaced if
needed later on. I dripped wax (red
substance) into the thread holes so epoxy couldn’t get into the nutcerts. On the right you can see the bearing installed.
I glassed the insert in place in the wing root and assembled the necessary hardware as called out. Below you can see the final assembly. The bearing and bearing surface are to the left side of the picture behind the silver arm.
That finishes the chapter.....Total time 232.8 hours.