35% Extra 330S

Construction (Page 1)


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Since I received no instructions in my kit, I contacted ZN Line to see if they had any instructions. More so I was interested in not so much the step by step, but more so the incidences they were using, thrust angles, center of gravity, etc.  A few days after I had sent them an email, a very nice gentleman by the name of Serge Bordais from France gave me a call. He was very helpful and answered most of my questions.  He emailed me most of the numbers I was looking for, as well as some pictures of the construction phase. I already had a fairly good idea of how this kit went together, and looking at the pictures he had sent, it confirmed on how I had pictured the construction to go.

Landing Gear:
After looking over the kit, taking a few measurements, and deciding on where to start. I decided that installing the landing gear would be my first step. This way, with the gear installed, I can sit the fuselage for subsequent steps.  The first thing I did was to build the landing gear frame. The frame consists of a 1/4" aircraft ply plate, that is fitted between two 1/8" light ply half formers. The basic idea here is to build the landing gear plate first, fit the gear, then glue it into the fuse. The actual gear is in two pieces,  made of carbon fiber, and when fastened, will sit below the gear plate.

Here is a picture of the gear. If you notice there are four blind nuts per gear, that are glued in with epoxy. The reasoning for the blind nuts, is that  the gear will sit under the plate, and in the fuse. In other words, the bolts will screw in from the top, go through the plate, and then into the gear. The beauty of this is that it is very neat, and you won't see any bolts from the exterior of the fuse.
Once I fitted the gear onto the plate, the next step was to glue the whole structure into the fuse. After dry fitting the plate, I notice that some of the formers that were supplied didn't fit as nice as I would have liked, there were some gaps, which I felt needed a little fixing.

Here is a picture of the landing gear plate. Again you will notice that it doesn't sit as nice as one would like. After a little trial and error though, and adding a few pieces to the plate, I got it to fit reasonably well. The concept of the plate is that the rear half former sits below the wing tube, and the forward former along with the two arms, extend into the forward section of the fuse for added support and gluing area.
Once I achieved a reasonable fit, I then had to mark out where on the fuse the gear would exit. This took a little measuring, and fooling around, as you don't want to cut into the wrong place of the fuse. So I started with a very small hole, and enlarged it slowly, always making sure that I was enlarging in the right direction. Once I had the hole close to the size, I decide to leave it, glue in the plate, then finish enlarging after the glue was dry.
The next step was to sand the area where the plate goes. Remember to always sand fiberglass very well in order to achieve a good bond. I also removed any foam that was in my gluing area. Again, you want the glue to contact the fiberglass, and not the foam for maximum bond. I used West System Epoxy for gluing. I've used it in the past on similar projects, and have had great success with it. I usually add a thickener to the epoxy. This gives the epoxy viscosity, which will enable you to make nice fillets around the formers. I used West System #404 filler which is a powder that you add to the epoxy. You can use milled fiberglass as well. They will both produce similar results.

Here is a picture of the plate while drying. As you can notice, I added some wood to various spots, to achieve a nicer fit, as well you will also notice that I have an incident meter sitting on the plate. The reasoning for that is you want the plate to sit level when gluing, this way the gear will sit level in the fuse.
Here is another view from the other side. Again you can see that the wing tube and the plate are both level.

Finally, once the glue is dry, the next step is to finish cutting the opening in the bottom of the fuse to accept the gear.
        Here are a few pictures of the installed gear and plates. I've yet to install the wheel pants, axels and wheels, for the simple fact that I haven't had a chance to purchase them, but I will finish that part off at a later time.

Wings and incidences:
There is no particular order on how I will complete this project, and I will probably jump back and forth between the fuse, wings, etc, depending on how I foresee the plane taking shape. There are still many things required on the fuse and gear, but I've decided to leave that for the time being and jump to the wings and stabs. My reasoning is that I would like to first fit the wings, calculate incidences, and establish all the basic lines, before gluing in the remaining formers in the fuse. This way I will be able to see the alignment of where anti-rotation pins will protrude, not to mention leaving room in the fuse to get at things.

The wings/stabs/and rudder supplied are all foam cored, balsa sheeted. They come pre sheeted and require leading edges, root and tip ribs. The ailerons and elevators are routed in the skins to give you your control surfaces.  In other words they are foam core, balsa sheeted, and that's it. The rest is up to you to finish. Zn-Line does supply the necessary balsa and ribs to finish the wings off.
Here is a picture of the wing. The root of the wing, comes with slots that are designed to house balsa blocks that will give strength to the anti-rotation pins. The foam comes pre slotted to accept blocks, although Zn-Line does not supply the blocks. So I had to make them myself, which took a little time, because of all the angles. Although with a little trial and error, it didn't prove to be too difficult. Once I fitted the blocks, I then glued them in, along with the wing tube sleeve.
The next step is to glue the root ribs on to the wings and stabs. They were supplied by Zn-line and fit fairly well. Once the glue is dry, my next step is to glue in the anti-rotation pins.
        I used some hardwood dowel for the pins, and then used a Dave Brown push rod shaft to cover the wood dowel. The reasoning for this is that the it gives added rigidity to the dowel for when mating it to the anti-rotation donut in the fuse.
Once that was done, the next step is to set up the airplane to calculate incidence. When I first started on the Extra, I took some preliminary measurements, with the already installed wing tube, and stab tube. I found these measurements to be pretty accurate, and in line.  This makes set up a lot easier.
The first thing I did was to level out the fuse. I have a large, level and relatively straight table, which is essential in obtaining good results. I used a level and incidence meter on the canopy opening of the fuse. That is my reference point to where everything will be measured. By placing a box under the fuse, and a few weights in the fuse to keep it steady, I would shift the angle of the fuse, till I had a zero reading on the meter. My next step is now to level the fuse laterally. For this I had another meter/level on the wing tube inside the fuse. Again, by shifting the fuse, I eventually had a zero reading in both places.
Once everything is level, my next step is to get the wings level. I used a few methods here to insure that I was accurate. The first method I used is an incident meter. I placed it on the wing and rotated the wing till it read zero. Once I had a zero reading, I then used a square, placed it on my level table, put a piece of masking tape on the square, and marked off where the trailing edge was. Once I had that mark, I then took the square, and took the same reading from the leading edge of the wing. It was spot on in the same place I made a mark at the trailing edge, hence assuring that I was accurate on all accounts. I then took the same square, and went to the other wing, and took measurements from both the leading and trailing edges, again they lined up with the mark on the square. Now that I was sure the wings were level, I marked off the locations on the fuse.
The next step is to mark and drill holes in the fuse to accept the anti-rotation pins. I made the holes a little oversized so that I can make any mild adjustments. The anti-rotation donuts are made out of 3/8 " aircraft ply, and the reasons I used a fairly thick piece of material, is that because of the contour of the fuse, I would have to sand them at an angle, so they would sit flush on the fuse. This in turn would cost material.
Once I fitted the donuts on the fuse, I then glued them in with West System Epoxy  (make sure you don't get glue on the pins or the wings will never come out again)  made any final adjustments, and let them dry over night.
My final step and once everything was set to dry. I did my final check, which involves my eyes. I sat behind the plane, and sighted the trailing edge to ensure that everything is straight. (Sometimes your eyes, are the best level)

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Last Updated 05/03/2007