Posts: 3583
Joined: 7/16/2002 From: Conrad,
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Well, mostly pics, but I will give measurements as required. Lets start with a list of materials:
8 yardsticks (spar) 1 4X8 sheet of 4 mil coro, color of your choice. 1 8 oz bottle of Elmer’s probond polyurethane glue (home depot) Small bottle of CA Lots of clamps Two 2inch X 3 foot X 3/16” thick balsa stock One 3 inch X 4 foot X 3/16” thick balsa stock Wood glue or epoxy Woodpecker tool Lots of clamps A square foot or so chunk of aircraft (not ‘light’) ply ¼ inch thick (firewall, wing block, landing gear block, reinforcement) Misc. hardwood. Chunk of 2" (or 1" would work) pink foam, approx 3"X6"
A FEW THINGS TO KEEP IN MIND DURING CONSTRUCTION:
1: Polyurethane glue takes about 4 hours to set up in 70-80 degree temps. It takes longer in colder weather, and you always need to mist with water for expansion, and faster curing times.
2: A dremel works great for grinding flutes flat. Just use a slow speed, and don't stay in one place very long. Heat will build, and melt the coroplast. Go over the entire area to be grinded; making nice, even motions with the tool.
3: A ball point pen works good for drawing your templates. Iso alcohol can be used to erase pen marks.
4: Whenever you need to fold coroplast on itself, it's helpful to remove the inside flutes on the fold line. How many flutes depends on the coroplast. I have 4 mil coroplast that varies greatly in the width of the flutes. So use your own discretion, it should fold very easily, and not crush or kink.
5: A utility knife and steel ruler clamped to the cutting surface helps cut coroplast (especially going across flutes). Press hard, hard enough to where it doesn't even feel like the coro is there. You should be digging into your work surface slightly, so use a work surface you don't mind cutting up.
Let's start on the wing first. The wing needs to be completed before you start on the major fuselage stuff. This is not a weekend project. Since I use poly glue for nearly all of my coro to coro and coro to wood joints, it takes some time for the glue to set up. Most guys should be able to get her darn near completed in a weekend, and week of evenings. Plan on roughly 30 hours to complete.
Take two yardsticks, and rip 1/4 inch off length-wise. These 1/4" pieces need to be glued to the top of two other yardsticks, giving you two 36"X 1 1/4" yardsticks. These are the main spar. I put two inches of dihedral in mine, but it's really up to you how much dihedral you put in. After you sand or cut each main spar yardstick on the end for dihedral, butt join them and glue. Take one of the yardsticks that you ripped the 1/4 inch off of, center it over the butt-joint (18" on each side of the joint) and glue it to the main spar. With two inches of dihedral, it should just fit without hanging over the main spar. This is the main spar reinforcement. Here's a cheesy drawing to show what I mean. I hope I am being clear enough.
< Message edited by Deadeye -- 10/18/2003 3:44:35 AM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
Secondary spar:
Take two 1"X 36" yardsticks and cut in the same dihedral as the main spar. Make sure it's exactly the same, or you will have a twisted wing. Take the other 3/4" X 36" (from the ripped yardsticks in the first step) and glue it on for reinforcment. You won't use all of the 36" length on this one, as it will hang over the edge of the spar. So cut it where it just meets the bottom.
You now have two spars. One 1 1/4 inch high, the other 1 inch high. The dihedrals should match exactly when you place the secondary over the main spar. Line up the bottoms.
Cut 6 2 1/2 inch strips from another yardstick, 1 inch high. These are the spar joiners. Using a square, glue these six strips to the main spar (make sure your spar doublers are facing away from each other, in other words, the main spar doubler faces TE, the secondary spar doubler faces the LE). They should fit flush on the bottom of the main spar. Glue the secondary spar to the other end of the joiners. Here's a top and side view pic for clarity. Please tell me if these are too hard to understand.
< Message edited by Deadeye -- 10/18/2003 3:50:44 AM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
You should now have a spar built, assuming you can understand my instruction and drawings.
Next step, the wing panels. I always run my flutes chord-wise. The pic shows the majority of the dimensions. The strip at the tip of the 11 3/8 measure is about ½ inch wide. One side of the plastic was removed for the leading edge. Total width of the panel is 22 ¾. So you need 2 panels 35 ¾ X 22 ¾ . The 22 ¾ should run with the flutes.
Posts: 3583
Joined: 7/16/2002 From: Conrad,
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After your panels are cut, you need to prepare them for glueing with the spar. Set the spar on a panel, and draw around it. Make sure you are centered. Take your woodpecker tool, and center it along all of the lines and start peckering. It's better to pecker too much, than not enough. Extra woodpecker holes don't seem to effect strength.
Woodpecker detail:
Edit: I forgot to mention that you need to woodpecker the panel on the trailing edge.
< Message edited by Deadeye -- 10/14/2003 11:40:54 AM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
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Prepare both panels this way. Don't worry about the top of the wing that will fold over at this time, we will prepare it after the spar is glued to the bottom.
Mist the bottom of the wing panel with water. Be liberal. Also, mist the bottom of the spars. Lay a bead of poly glue on the spars (only one half) and carefully lay it flat on the first wing panel, keeping your main spar line lined up with the spar. Don't worry about the servo mounts in the pic, I'll get to that later.
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
Make sure you only do one wing half at a time. The spar needs to be clamped flat against each panel, and due to the dihedral, you can only do this one side at a time, and only on the bottom of the wing panel. While you wait for this to dry, make some servo mounts. These can be of any design you want, and some may opt to just SPAD them in (use cable ties or the like). I cannot vouch for this strength-wise, as I have only used wood ones.
Do the other side of the wing just like the first side. You should now have a full wing, with only the bottoms of the wing panels glued to the spar. Take your servo mount, and center it between the end of the wing, and the center. Mark where the servo will go, and carefully cut your hole in the bottom of the wing panel with a utility knife.
More to come later, I gotta get to work.
Servo Mount detail:
< Message edited by Deadeye -- 10/18/2003 3:55:08 AM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
Glue your servo mount to the spar. Make sure you can get a servo in and out of the hole you cut in the coro. The mount sits flush on the inside of the coro, then simply attaches to the spar. Now we'll work on the front wing mounts. I used 1" square hardwood, that is at least the heigth of the spar (grain should run height-wise), so two 1X1X 1 1/4 inch cubes of HARDWOOD will do. Drill a 1/4 inch hole in the center of this block. You will have to curve the top part to fit the airfoil. Once you have it the way you want it, epoxy it to the spar, and poly glue the side that mates with the bottom coro piece. Your holes should be roughly 2 inches apart, or 1 inch from center.
< Message edited by Deadeye -- 10/19/2003 12:37:17 AM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
Now, poly glue some 1/8 ply to the rear of the wing, approximatley 1- 1 1/2 inches from the trailing edge. Make sure you clamp or tape this plate to the coro, or the poly glue will lift it away as it cures. This is your rear wing bolt plates. You will still need a ply plate or fender washers on the outside of the wing, but this interior plate stiffens it up considerably.
< Message edited by Deadeye -- 10/14/2003 1:41:32 PM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
Time to build the ailerons. Aileron deminsions are 33 1/4" long X 2 1/2 inches wide of doubled over coroplast. Cut 2 strips of coro, flutes going the long way, 33 1/4 X 6 1/2. Here's where it gets tricky. You have to cut 1 1/2 off one side of the flutes, and shave them down slightly., then remove 2 flutes in the center so it will fold and bend properly. Woodpecker the mating coro surface, and the hinge. Mist, and apply poly glue. Fold over the two halves, and clamp into place. You can opt for CA glue here, but it will flex more than poly glue.
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
When you are sure you have all of your inside work done, including woodpeckering the top coro to yardstick mating surfaces, it's time to fold over the top panels (one at a time), and glue them into place. I use a clamping system made up of a 6 foot 2X4, and a 6 foot 2X2. Clamp the 2X4 on top of the 2X2, keeping the back edge flush. The following pictures will show my detail. Use another 2X2 to clamp the trailing edge with the aileron inbetween. Make sure you mist and liberally apply poly glue here. The better expansion, the better your wing will be. More water makes the poly glue expand more. Make sure you can flex your aileron when it is clamped. It's easier to do this if you have the TE lined up with the edge of your table, so your aileron hangs over the edge.
EDIT: I don't know why my first two pics disappeard, but I replaced them.
< Message edited by Deadeye -- 10/15/2003 12:23:54 PM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
I ended up taking my Cor-Star's wings to the band saw after they were built, to whap about 2 !/2 inches off each wing tip. This gives it a faster roll rate than the regular wingspan, but it also comes in a bit hotter. The whole point of the double spar system, is to give the coro an abrupt curve at the LE, just like the balsa 4*. One spar didn't get the edge up like I wanted. The resulting wing, looks much closer to the 4* than a single spar could provide. Here's is the cut off wing tip. Your wing's profile should look something like this. Notice how the poly glue has attached itself to the aileron hinge. Notice how it seeps into the coro, and makes thousands of tiny little 'rivets'. Once your wing is dry, feel the LE. Pretty tough, eh? I smacked my first Cor-Star into a fence post, and it hurt the post more than my wing. The resulting wing will be about 1 pound heavier than the balsa 4*. But don't worry! We will regain that pound, because the fuse builds about a pound lighter than the balsa one.
EDIT: Your bottom will be flatter than this wingtip shows. On my Version 2, I centered those wing joiners on the main spar, verses a flush bottom mount. It's not really necessary to do this, but try it if you want. Just be careful not to kink the LE. Built per my plans, the LE is just about to the point of kinking. In fact, if you have done it right, you will notice a hatch (diamond) design on your LE. The coro is almost at it's kinking point. Once the glue is dry, though, it will not kink.
< Message edited by Deadeye -- 10/18/2003 4:01:52 AM >
Posts: 3583
Joined: 7/16/2002 From: Conrad,
MT, USA Status: offline
The next stps will be the tail feathers. These can be cut in a an hour or two. However, I don't want to go on if my instructions are not clear. Some feedback would be much appreciated.
Posts: 1406
Joined: 4/24/2002 From: Sarasota, FL, USA Status: offline
Clear as a bell. This is all 4mm right? 2mm for the wing is too flimsy? Looks great! Thanks for the step by step build. I can see one on the build table allready.
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Cor-Star 60 Version 2.0 plans and pics - 
