Introduction: Make a Small Foam Glider - LET L-23 Super Blaník
Middle picture: http://home.nwi.net/~blanikam/ba/fot09.htm
Glider, But Why?
1. To demonstrate the flight of a Civil Air Patrol glider (LET L-23 Super Blaník) for educational purposes in an outside environment (large scale only) after being duplicated in a classroom environment (hands-on project).
2. Why not? (;
OK, What Do I Need?
1. High Density Foam
- (1) Foam Block for Body: 10" x 4" x 1"
- (1) Foam Block for Wing: 9" x 2.5" x 0.75"
- (1) Foam Block for Horizontal Stabilizer (little wing on tail): 4" x 1" x 0.5"
2. (1) Foam Cutter *note: the cutter I used was MADE in classroom and that is not part of this instructable*
3. (1) School Glue
4. (1) Calculator
5. (1) Ruler and Protractor
6. (1) Pen or marker
7. (2) Toothpicks
8. (1) Small Paintbrush
- (1) high grit sandpaper
- (2) low grit sandpaper
10. (as needed) Solder or Floral Wire (for weight and balance)
11. (4) 4A Paper
12. (as needed) Push Pins
13. (1) Weight for Nose of Glider
- Hair Tie, OR
- Balsa Wood Carved as Canopy, OR
- 3D Printed Canopy
14. Personal Qualities
- (most of it) common sense ;)
- (all of it) good attitude and patience
15. Wax Paper (table cover for gluing parts)
16. (as needed) Nose and Mouth mask for yourself or anyone around you who does not like strong smells
17. (1) Cup for Water & Glue
!!! Warning: This project is messy. The sanding foam is the messiest part. This project involves heat. Cutting the foam.
Step 1: Drawing Up the Plans
1. Print out the blueprint of the glider, link here:
2. Measure and scale the printed plane. So, I used SolidWorks to obtain my scale of the glider by what the software automatically having scaled the picture to when I entered it in as a "Sketch Picture." Here's how to input the blueprint as a sketch picture: tools>sketch tools>sketch picture. Lets say you don't want to do all that though; download the document, print the document w/o making changes, and measure the plane on the document making notes as shown ^. I used 1":1.8815" as my scale.
3. The nose of the glider is a parabola. The photo above shows how this can be drawn or visit this site for more information: https://mysite.du.edu/~jcalvert/math/parabola.htm
4. I scaled up the side profile of the glider on 4A paper and scaled up the parabola to trace on the foam.
Step 2: Lining Up the Plans
1. If your foam isn't already the sizes stated in the materials list go ahead and cut it down to those sizes. Do not mark on the other sides unless absolutely necessary.
2. Next I marked up the foam for the body of the glider and lined up my glider profile on the foam.
3. I used push pins to keep the paper in place while punching holes in the paper and foam to outline the glider's body shape. Every couple of holes I'll mark a hole with a pen so that I'll be able to see my outline when I go to play connect the dots. I used the same technique for the nose of the plane.
4. I did not trace any other parts of the plane. I either free handed it or used my scale and drew it straight on the foam.
5. OH NO! You mess up a measurement in pen. No biggie! Flip over the foam and start over; that's why #1 says not to mark on other sides unless absolutely necessary. :)
Step 3: CUT!
1.CUT! Use mask or fan as needed. I started the cutter at 2.16 amps and went up to 2.80 apms max. The wire on the cutter needs to be straight and tight if you want your parts to come out even. Cut slowly and smoothly; it is better to leave on too much foam while you can always sand it down but you cannot add foam back.
2. After I cut out the profile I place it back in the shape with the help of push pins. Note: I left those green colored strips on to make cutting the shape easier. Because of that I did not have to worry that I was not holding the foam straight, but I used the table as a guide. Flip the foam and cut the curves in the body of the glider.
4. Wings: I cut the one piece of foam for the wing down to the right shape and cut it in half. This way each wing had the exact same shape. :)
5. The same was done for the horizontal stabilizer, but here use the table or wall as a guide for the cutter.
Step 4: Sand
1. Before sanding I placed the wing where it should go on the glider when it will be shaped. I marked the location with pen then used a tooth pick to join the 2 wings and body.
2. Cut! Just like cutting, use mask as needed. :)
3. Start with the high grit sand paper to sand the shape of the body and the wings. Note: I free handed the airfoil and used the cutter to cut away the larger bits of foam on the wing I otherwise would have sanded off.
4. Take your time here and do not carve into the foam with the sandpaper. Be sure not to forget to sand the bottom of the wings as well, and line up the wings to make sure sanding is even. Use two toothpicks in the extra foam block to test the balance of the glider again. Place the glider wings on the toothpicks about 1/3 the way to the front of the wings. Adjust sanding as needed.
Step 5: Glue
1. Glue the wings on the glider body with the tooth pick in the glider. After the wings dry about half way glue the horizontal stabilizer using scrap foam to hold drying parts in place, OR to keep the parts from shifting around use tooth picks to stick the plane in the extra foam where the horizontal stabilizer is supported.
2. Coat the entire plane in a water and glue mixture.
3. OH NO! You broke the tail now? No problem! If you haven't already go ahead and snap the tail off at the thinnest point! Do not cut the tail with the cutter. Sand a toothpick down some with low grit sandpaper and snap it in half. Sand the rough end to a point and use it to connect the tail and body. Glue. This will help prevent the tail from snapping off when testing the glider in a flight.
Step 6: Weight and Flight
1. When the glue dries use two toothpicks in the extra foam block to test the balance of the glider again. Place the glider wings on the toothpicks about 1/3 the way to the front of the wings.
2. Adjust weight as needed with trimmed down floral wire or solder by poking small pieces through the foam. Sand to adjust weight as needed.
3. I used a hair tie for weight on the nose of the glider, but a 3D printed canopy or balsa wood could also work. This is up to the builder's discretion.
4. After I finished the assembly I had to make numerous minor changes by sanding the wings and re-applying glue coats.
5. Fly! Test fly the plane. If the plane flies fine congrats! if the plane does not fly fine go to step 7.
Step 7: What's Wrong With the Glider?
1. Because the glider is so small the smallest bend or misalignment will skew the flight. If the glider flies straight then turns upside down and falls the issue could be a heavy tail. Sand down the tail a little bit or add weight to the front. Use the toothpicks under the wing to test for equal weight of the tail and nose.
2. If the glider only dives then the nose could be too heavy. Sand down the nose or remove weight from the nose.
3. If the glider turns left or right sand the wings till they are even.
4. If the glider has another problem where the flight is not straight the angle of incidence could be off. This is the bottom of the horizontal stabilizer and the bottom of the wing. Point the nose of the plane to the ground and drop the plane. If the plane dips back or forward then the issue is the incidence. Put tape below the horizontal stabilizer and one below the wing. The two pieces need to be parallel. If they are not determine if the front or back of the horizontal stabilizer needs to raised or lowered. I had this issue and I solved it by melting a little bit of the foam on the tail in front of the horizontal stabilizer and gluing it down.
5. Fly in a low wind area to test for these after tackling these problems.