Nov 10, 2010, 12:32 PM
USA, ME, Ellsworth
Joined May 2008
32" KFm3 Flat Wing Build - Part 5
32" KFm3 Flat Wing Build - Part 5
Now we'll cut the ailerons out, mount and hinge them. and finish up the linkage. I made the ailerons 1-1/4" wide and 11" in length measured from the outboard tips in. That should be plenty of aileron authority for a high winged aileron trainer/sports flyer, I'd be surprised that very much of the available deflection will be used in flight.
40 - Layout Aileron Cuts - The aileron layout is marked and drawn on the back edge of the wing.
41 - Cut Ailerons - The ailerons are cut with the tools seen here and as previously described. Avoid crossing cuts at the corners, keep the knife inclined back at an angle, and it all goes nicely
42 - Bevel Ailerons - The edge of the aileron, and the wing where it meets it, will be beveled to form an inverted "V" on the bottom of the wing to allow for the aileron to swing down. The hinge line will be the mounting tape and located on the flat top of the wing so no additional clearance is needed for up swing.
I have posted an image here that explains package sealing tape hinge. This is the Worlds Greatest Hinge For Scratchbuilt Foamies (WGHFSF). It is simple to master, works perfect, and is easily mastered. Try one on some scrap first if you want some practice.
Lay a straight edge on the bottom (plastic skin side) of the aileron and cut a 30-40 degree or so bevel on the edge that will meet the wing.
43 - Bevel Aileron Cutout - Lay the wing on the corner the bench so that the area from the 75% step back is flat on the cutting mat. The plastic skin side will be up, lay a straight edge along the edge of the aileron cutout and make a 30-40 degree bevel on the wing.
44 - Mount Ailerons - As seen here the wing is bottom side up with a half exposed strip of tape is already attached to the top surface and laying sticky side up. There two short pieces of light cardboard laying on the wing as the spacers for the line. The aileron will be laid on top of the spacers with the edges of the two bevels aligned vertically.
45 - Tape Aileron to Wing - The aileron is almost in position here, that will be aligned and held in position and the tape will be lifted up to vertical and pressed into adhesion with the wing bevel, then on around and onto the bevel on the aileron. Use your finger tips to get the tape in contact and then lay the tape on the aileron smoothing it forward.
To finish the WGHFSF hinge turn the wing over and let the wing and aileron lay flat on the bench. Use a tongue depressor with smooth rounded edge to press the tape down into the bottom of the "V" and back against the bevels on the sides.
Then turn the wing over and you see a narrow line of exposed tape. Pressing on the back aileron edge will push the tape up into an inverted "U" on the top of the wing. Lay a strip of tape that is the width of the aileron on the wing above the aileron, push on the aileron to get the gap/exposed tape line even, and lower the tape down across the gap and onto the aileron. Work the tape down smooth, fold the aileron up on to the wing and smooth it on the bevel, and you will have just created the WGHFSF hinge.
46 - Locate Control Horns - Use a square or corner of a piece of paper to located the control horns. The line for mounting the hors is in line with the servo horn and at right angle to the KFm step.
The control horn seen there is made from a Dollar Tree store dental flosser. The drill has a 1/4" tube drill in it and will be used to drill two holes in the top of the aileron. The legs of the control horns will be set in hot melt glue in the holes. When I drill the holes I just drill the tape on the top layer and the foam and pick the foam out of the hole leaving the tape to close the hold on the bottom.
For the horns to work properly, the hole in the control horn needs to be directly above the hinge line, not in front of or behind it.
47 - Mount Horns and Linkage - Seen here the horns are glued in place, Mini EZ connectors have been added to the horns, and the linkage to the servos fitted.
48-49 - Check Aileron Action - This all looks good, I'm getting about 45 degrees of up and down travel, this will be a candidate for low rate setting on the TX, I can tell already.
I am checking the ailerons here with a servo tester that will test two servos at a time. With that I can rotate a knob to see the same directions of travel and travel limits I'll see with the TX set to defaults. Very handy little thing to have in the shop.
The few remaining touches will be to add the protectors on the wing center at the leading and trailing edges where the rubber bands will cross, maybe add some tip plates to the end of the wings, and some colored tape at least on the bottom of the wing to help with inflight visibilty.
I'll fill you in on the details later...
Last edited by jackerbes; Nov 14, 2010 at 05:02 PM.