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A short introduction I have been building planes now for around two years. I chose the foam format because shaping the material is very easy. From simple designs like those of a Cessna, to a 100mph pylon racer, to an Extra 300, have all been built in the same manner. This is the seventh and final version of the Extra 300s, and all three I have built using this design fly superbly Good luck Material used:
Section 1: The fuselage
Print P1 and cut out two A1 parts, which will give you one left and one right side. Tape them together and make sure they are the same shape by sanding the edges to get equal sides. Trim away the tail section as shown in T1 making sure the overall thickness is at least 20 mm. Tape together at T2 and glue together at T1 to achieve T3.
Now to get the basic shape, glue a 20mm balsa nosepiece A2 that you will sand to shape later. Make sure you place the two sidepieces on a flat surface to get a parallel fit to the fuselage before gluing the nosepiece. You should now be at stage P2 except that your balsa nose is still square.
Carefully cut and glue A3, A4, and A5 into place making sure the fuselage stays square and true, checking after each piece is glued into place. This is the most important stage of the whole construction, as this will determine whether your Extra flies straight and true. Now cut and glue A6, A7, and A8. After this stage, start shaping the nosepiece.
You can use P5 as a template to get the shape right for the nosepiece. Once you are happy with the nose, you can put your rudder and elevator connector rods through the fuselage as shown in P1. If you have not done it already, now cut and glue A9 and A10 into place. This will now complete all the pieces to create the fuselage. Sand it to shape using P6 as a guide. Now comes quite a tricky bit. You need to cut out A12 from the fuselage. First, glue a connection piece A15 between the left hand side and right hand side of the fuselage. This will stabilize the two sections at their thinnest point after cutting from the fuselage and create an exact fit later.
Using P5 as a template, use a Dremel tool to cut out the breather hole, making sure it is in the center of the fuselage.
You can now cut out the motor mounting flap A13 from the nose section. Make sure you cut enough to enable the mounting of your reduction unit or direct drive motor. Cut a 20 x 20 mm balsa block and fit at position A14 for the wing-mounting pen. Also glue two strips of at least 10 x 1,5 mm at position A11 both sides of the fuselage for added strength.
At this stage, your fuselage is virtually complete, besides the covering that comes later. Section 2: The wing Using the wing templates, print them and glue them to a 5mm balsa plank. Cut out and remove only the top part of the template, as this is the side we will cut first.
From a 30mm styro sheet, cut out the wing shape, and mark the front and top with a pen. On occasion, I have cut the wing just to find out I cut it backwards.
Once you have cut the top of both halves of the wing with a hot wire, glue the top section the template back to where you cut it from, and then cut out the underside of the template. Turn your wing halves over placing them in the parts left over from the first cut.
Cut out the bottom the same as you did the top and once you have your cores cut, line them up against each other making sure they are perfectly matched up. Tip to core, core thickness, tip thickness, etc, to avoid strange flying behavior later. Once you are satisfied that the cores are true, sand off the surfaces with a fine sandpaper and using either spray adhesive, or any other method, glue 1mm balsa skins on both surfaces using the left over pieces from the original cut to lie the cores into. Once dry, cut a 10mm leading edge, and glue into place.
Mark the center line or utmost tip position of the leading edge with a pencil and sand the leading edge to shape. Do the same to both left and right wing halves checking your work frequently to make sure that you have two exact wing halves.
Now, using 5-minute epoxy glue, glue the two wing halves together. To ensure that the top of the wing remains perfectly flat, turn the wing upside down on your works space and let the glue dry.
Once dry, the wing will have a natural dihedral of 1.5 deg, giving extra stability. For inverted flight, the built in one degree of attack to ensure straight and true flight without any need for elevator input. Now that the most difficult part of the building process is complete, we move on to the next stage, and that is finishing the model ready for covering with Oracover or any other material you prefer. Section 3: Getting ready to cover Before you can cover the fuselage, you need to cover it with 1 mm balsa sheets. This ensures not only strength in the lateral force, but also gives a good surface to adhere the Oracover. When selecting balsa for this purpose, choose only "A" grade and the softest balsa you can find. This is usually the lighter colored balsa. It needs to bend around the fuselage in many places and is not the easiest of tasks to accomplish.
Start by spraying on your adhesive on both the fuselage and balsa and letting dry for 10 minutes before attempting to cover. Starting with either the left or the right hand side, use 100mm balsa plank and with a rubbing motion, press against all curves working from the center where the wing will mount, to the tail, and then to the nose. Trim and glue with styro instant glue. I also use an activator spray to help in the more difficult places. Once all covered, you can go ahead and cover with Oracover or similar finish using a hot iron. Before covering the wings, we need to cut out the ailerons and servo recesses.
Once these have been cut out, and the servos mounted with double side tape, we can fit the strip of balsa that we cut out for the cable back where it came from, and sand off any unevenness.
Next, we need to trim the wing to fit the fuselage. Measure exactly 10 mm from the leading edge of the wing, and line it up against the fuselage to get the width and trim the leading edge as shown. Repeat this step for the trailing edge, but this time measure 30 mm.
Section 4: Fitting the parts together
Glue a 1.5 mm triplex piece to the front of the cutout in the leading edge. Measure the center and drill a 5mm hole. Insert a 5 mm dowel into the wing.
Now trial fit the wing into place. Note the spot at where the dowel marks the previously glued balsa 20 x 20 mm wing-holding mount as described earlier at point A14. In theory, this should be exactly in the center. Drill the appropriate hole into A14 and fit the wing into position as shown.
Now trial mount the top part of the fuselage with the wing in place to ensure a tight fit. At this stage, you will need to use another piece of triplex to keep the top part of the fuselage in place once the nylon bolt has been inserted as shown here.
You can also use this opportunity to trial mount both the elevator and rudder, assuming you have cut out the slot for the rudder already.
Section 5: Fitting the electrics
Take note of the diagram below to locate the electrics. If you do everything correctly, the seven-cell battery pack will fit perfectly for the correct CG. Depending on the gearbox you use, and whether or not you used an aluminum spinner or landing gear, you should still have enough movement in the placement of the battery pack to adjust the CG. If not, you can use a couple of nails in the tail section to adjust your plane for level flight. I used exactly 4 x 40 mm nails in the tail to get the CG perfect. In the picture above, you can also see that there is provision on part A7 to fit a sturdy landing gear if you so desire. Even with a landing gear, I just toss the plane into the wind and she flies straight and true every time.
Notes on mounting the motor: You can select to mount your motor combination with a little down-thrust in mind (usually 1 to 1,5 deg), but I didn't and still haven't even after ten flights or so. Section 6: Final notes and first flights
Once everything is mounted, you can just use tape to tape the engine-mounting flap back into place. You will also need to cut strips of foam to secure the battery. I did not use any straps to secure the battery. I just made sure my strips of foam hold the battery tightly. Don't forget to fashion a battery hatch in the hole that was left after all the parts had been glued together. Aileron throw should be about 8 to 10 mm. (use 40% exponential). Elevator throw is 8 to 10 mm (use 50 to 65 % exponential, and 80 and 100% dual rates). I suggest that you set the rudder with as much as you can give it. Mine is 55 mm, just missing the elevator with no expo at all, for those all-impressive snap rolls and knife-edge flights. For motor choice, I used a 15 to 17 turn car motor (Corrally or Reedy) with a Graupner belt drive 2.5 :1 reduction unit. This combined with a 10 x 6 APC prop is nice and quiet and provides 1000 grams of thrust. At an all in weight of around 1300 grams, this gives the plane enough thrust to take off from grass within about 20 m, and 6 to 8 minutes of flying. Of course a brushless system and more thrust are always fun. For the initial launch (hand launch), I dialed in about 1 to 1.5 degrees of up elevator, just in case I needed to do a quick recover from a bad launch. However, in my case, she flew straight and true, and only needed minimal aileron trim (1 click) With 1 degree of washout, the tip occasionally stalls if you insist on flying right at the stall point, but she quickly recovers. Inverted flight is an absolute breeze and I was amazed that there was absolutely no need to feed any elevator at all once it completed a half roll to fly inverted. She just flies as if she was the right way up. This is very handy for those lethargic rolls across the flying field. Landing is also a breeze, very predictable, and comes in true every time. One important note is that the CG must be spot on if you want to fly good aerobatics. When nose heavy, the rolls become more of a spiral, and if too tail heavy, she will wallow around the sky as if she has fleas in her pants.
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Mar 10, 2006, 08:02 AM
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#2 |
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Registered User
Join Date: Jan 2005
Posts: 127
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Where is the templates for this project?? i'd like to be starting building this plane next weekend but i couldn't find the templates yet...
Tks... |
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Apr 10, 2006, 03:58 PM
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#3 |
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Registered User
Join Date: Apr 2006
Posts: 5
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plans missing
HI there,
i need the plan also. Is this a dead project ? Andreas |
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Apr 10, 2006, 06:57 PM
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#4 | |
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Registered User
Join Date: Jan 2005
Posts: 127
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Quote:
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Apr 12, 2006, 04:38 AM
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#5 |
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Registered User
Join Date: Apr 2006
Posts: 5
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Hello "hate"
i just like to start the discussion. we are not the only one . [URL=http://www.rcgroups.com/forums/showthread.php?t=503856[/URL] I think i got it now. Save the pictures locally. They are in jpg format . JPG´s are resizebale by any graphics software. Greeting from Germany Last edited by cellarsnorser; Apr 12, 2006 at 05:07 AM. |
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Apr 12, 2006, 08:16 AM
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#6 | |
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Registered User
Join Date: Jan 2005
Posts: 127
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Quote:
a full plan, with all templates in a single image would be a good thing.. |
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