Evaluating Your Cut
Here is a simple, inexpensive, safe foam cutter you can make and use that really works. By Lee Aston
I highly recommend that you always do test cuts on less expensive foam and scrap to get the bow movement and function right before attempting to cut the more expensive foam. Make your mistakes during the learning process not on a critical cut.
Cutting foam is a learning process. Look carefully at every cut you make and work to improve it on the next cut. There are many variables that can make a significant difference in the quality of your cut if you are not getting the quality of cut you want. This applies to both the single jig and automatic cutting systems. If you are not satisfied with yours here are 10 ideas to try:
1. Changeyour cutting temperature.
2. Check your wire tension.
3. Change your cutting speed.
4. Try different cutting wires.
5. Route the strings on the bow differently.
6. Raise or lower the cutting board.
7. Try different foam.
8. Add weight to the swing arm on the automatic cutter.
9. Loosen the tension on the suspension of the bow to the ceiling.
10. Move the ceiling connection point forwards or back to improve bow movement.
I hope this information has been helpful. I am a hobbyist not an electrician or an engineer. What I have told you is the way I have made my foam cutter work for me. There are many other good ideas out there and I encourage you to seek out other ideas and methods to make your foam cuts as safe and precise as you can.
FREE "WILD WING" PLANS
1. Cut a piece of EPP foam 2" x 12" x 24".
2. Split it diagonally with a 9" to 3" cut making two identical pieces.
3. You need to cut an angle on the 9" end of each core that will sweep the leading edge of the wing back 38 degrees. The easiest way to get close is to lay the two pieces of foam side by side so that the 9" sides are together. The longest side of the foam pieces is the leading edge.
4. On the trailing edge which is the flat edge, measure over 4" on each side of the back from the center. Draw a line up to the other corner on the 9" end of the wing. Double check and make sure before you cut that you have the right side of the wing and the right angle.
5. Cut the foam and check your angle.
6. A parallel matching tip angle should be cut
7. Make a cutting board out of ¾" particle board that is the exactly same shape as the foam to be cut.
8. Make your one piece jig as described in the foam cutting text using the top of the SD7032 airfoil over the bottom of the SD6060 enlarged to 9".
9. Screw the jig to the 9" edge of the cutting board with the leading edge to the front and the trailing edge ¼" forward from the trailing edge of the cutting board.
10. C-clamp or screw the anchor to the table as described in the text, with the flat corner bracket to the front.
11. Put a bolt through a hole in the anchor 1"-1.5" above the top surface of the cutting board. Put this bolt through the chin link on the cutting bow that has the rubber bands through it and secure it with a washer and a wing nut.
12. The bow should be able to move with the pivot of the wire taking place at the two chain links and the rubber bands adjusting the slack.
13. Put the foam block on the cutting board.
14. Put the weight board on the top of the foam with a weight (brick) on it as described in the text.
15. Align the wire on the cutting bow with the trailing edge of the core, with the core near the far end of the bow. Lift the cutting wire over the cutting board and foam to the leading edge of the wing and check the leading edge alignment.
16. Scoot the cutting board and foam towards the anchor until the angle of the foam is the same as the wire on both the leading and trailing edge. Make sure the wire will not exit the foam leading edge on the tip when tracing the one piece jig at the root.
17. Turn on your ventilation fan. Do not let the smoke off of the cutter rise into your face. I also use a small fan in the room to help clear the smoke.
18. Set the cutting wire in the back slot of the jig preparing to cut.
19. Turn the cutter on.
20. With your hands on the cutting spike and the top of the bow where your thumb can reach the on/off switch, trace the jig cutting the bottom of the airfoil first then circle the leading edge and cut back over the top of the airfoil and exit the foam.
21. Cutting speed is totally by touch but very crucial. If the cutting wire hesitates it will leave a groove root to tip on the core. If you do not trace the jig exactly you can end up with all kinds of defects.It is important to make sure the cutting wire is caught up with the bow as you go around the leading edge so the leading edge comes out straight.
22. If your wire breaks, turn off the thumb switch, turn off the power supply switch and unplug the unit from the wall before you touch either end of the broken wire. The wire will still have power even when it is broken until the power is turned off. Wires do not break very often, but when they do they are the greatest danger in foam cutting.
23. Separate the core from the foam it was cut from, which we call the bed. Work over the top and around the front to separate the core. There will be spots where the melted foam will stick the core to the bed. Most are easily separated. We tend to have more trouble on the trailing edge where the foam is thinner and the cutting wire exits the foam. Use an exacto knife as needed. If the core tears or pieces come out use a low temperature hot glue gun and glue them back in.
24. Remove the core from its bed and use the guillotine foam cutter to trim the trailing edge of the wing so that the entire trailing edge is 1/8" thick.
25. Follow the instruction on the "Wild Wing Instructions" on "Lee's Blog" on www.utahflyers.org for complete building instructions for one of the best little planes you'll ever fly.
