Deadeye

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.

Deadeye

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.

Deadeye

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.

Deadeye

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.

Deadeye

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.

Deadeye

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:

Deadeye

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.

Deadeye

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.

Deadeye

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.

Deadeye

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.

Deadeye

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.

Deadeye

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.

Quicker

So far so good for me. Keep up the good work!!!

rsieminski

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.

Deadeye

The wing is 4 mil, as is the rest of the plane. I don't know how 2 mil would work. I would think with the dual spars, that it would be strong enough, but can't say for certain.

Deadeye

The vertical stab is one piece, folded over. Cut per the pic, and don't forget to woodpecker the ENTIRE coro mating surfaces. There is also a 1/2 strip removed from the center. These flutes need to be opened a little with a razor, and try to keep it straight! The straightness of this cut determines how straight the vert stab will be. Remove the inside skin, and try to bring the halves together, if it's to hard, remove some of the flute. A dremel with a sanding drum on low-medium speed does a nice job, just be careful not to burn through to the other side.

The rudder still needs to be cut , so don't fold and glue yet. I need to see if my measurements will show up for the vert. stab.

EDIT: DOH! my fonts look kinda small. Can you guys see it?

FlyBlueSkies

My Feedback: (2)

Yes!

Once I click on the larger image, I can read the dimensions OK!

Excellent pictures!

gr8johnson3

well i can not see the dimensions on my screen. dont know why but i cant. also can anyone tell me how to print this stuff so it will fit on the paper. it cuts the right part off when it prints. thanks alot. great job deadeye

gr8johnson3

ok i can see the dimensions now. must have been the monitor settings. but i still cant get it to print.

Deadeye

I fixed that other vert stab pic above, and now here's the rudder. It needs to be prepared the same way you did your ailerons. Only, instead of leaving some of the flute for the coro to grab, you have to grind or sand these flutes flat, so all you have left is the inside skin for the hinge. The vertical stab has to fold flat, and if there is any flute left on the rudder, it will be raised on the hinge line, dramatically reducing the effectiveneness of the rudder in flight.

The rudder and elevator halves are the most 'complicated' pieces in the Cor-Star. Be patient, they take a little time to make right. Make sure you weigh them down when gluing, and check often that the poly glue isn't pushing the wooden blocks out of position. Your result will be an extremely stiff and strong rudder. I have landed very hard on the tail of my first Cor-Star (hard enough to snap the wire...TWICE),and the rudder isn't showing any signs of fatigue.

When the rudder is glued, go ahead and glue it's hinge into the vertical stab, glue the vertical stab halves and fold them onto the rudder hinge. Make sure you can move the rudder 45 degrees in both directions. Don't forget to mist with water!

novabill

You are the man Deadeye

I love your building techniques. When is the fuse coming?

WILLIAM

Deadeye

OK, on to the Horizontal stab and elevator halves. They go together just like the vertical stab and rudder, with one exception. You have to use a wire for a torque rod on the elevator halves, I found it easier to drill my holes in the torque rod blocks, after they were glued into the elevator halves and the glue was completly dry. I used 1/8 wire, but you can substitute whatever you want, as long as it won't flex to much. The elevator control horn can be mounted to the torque rod block (so it doubles as a control horn block) after the wire is epoxied in, and after it's glued into the horizontal stab.

The template shown for the hor stab is paper. Tht's why it looks different, but it still gets the point across. You may opt to make paper templates of all of your hard to make parts, makes building the next one MUCH faster. And after flying this beauty, you will never want to be without one again.

Don't worry if your tail surfaces don't have clean edges just yet, after the hor stab/ elevator and vert stab/rudder are glued and dried, you can clean up all the edges that dont match. Just be sure on the hor stab that you have equal distance from your center line.

The elevator pic shows woodpecker detail and poly glue. These halves are ready to be folded and clamped or weighted down. DON'T FORGET TO MAKE TWO OPPOSING ELEVATOR HALVES A RIGHT AND A LEFT!

Deadeye

In response to novabliss, the fuse is the next step.

These pics show the completed tail assemblies. You will need to notch out a spot in the hor stab for the vert stab's joiner piece to slide through. Don't glue them yet, it's much easier to do this in one step after the fuse is mostly built, and the wings are bolted on.

gr8johnson3

Deadeye, what is the dimension on the elevator where the flutes are removed and the fold is done? i see the 11 3/4, but it looks like the fold length is smaller distance to make the angle.

Deadeye

Whoops! I forgot that measurement. It 9 7/8 inches.

Bear with me, this is my first attempt at plans. It's rather difficult to put into words what needs to be done sometimes. In fact, I have been making several changes to several of my posts in this thread. You may want to go and re-read some of them. Bah, there's a fly on my keyboard...adowtpwet9wetiw-0f9swerwp;sfkmspdv...got it!