Apr 18, 2011, 09:17 AM
USA, ME, Ellsworth
Joined May 2008
KFm2 Wing with Polyhedral Tips - Part 1
KFm2 Wing with Polyhedral Tips - Part 1
Building a new 48" x 11-1/2" KFm2 wing for the KFoenix Stick, this wing could be used on a Slow Stick too of course.
The plan is to make this RET only wing for slower flying and training and camera work. I'll build it with a flat center section and tips with 2-1/2" of dihedral on each side and no ailerons will be fitted.
If you want a flat KFm2 wing with ailerons this same build will work for that, just don't cut and bend the tips for dihedral.
The instructions are keyed to numbering on the photos as they are posted and named.
2 - 24" x 48" sheets of Dow Protection Board II or FFF sheet foam with the sheets still joined by factory folded edge.
2 - 1/4" x 36" wooden dowels (cut to 31" long, can be full length and up to 48" if you are not going to make the polyhedral tips)
Colored package sealing tape
Clear package sealing tape (Duck brand "Standard" weight
Clear duct tape (Home Depot or Lowes)
Gorilla Quick (White) PU glue (regular PU will work, setup times will be four to five times as long)
Clear plastic corner guard (Lowes or Home Depot)
Snap tip utility knife
Fine tip Sharpie marker
Sheet rock square or long straight edge
18" or so metal ruler
tape (from Wal-Mart) works, do not use any "heavy duty" tapes).
I'm starting with two sheets with the skin side out, if yours are skin side in you can reverse the fold. If the skin cracks along the fold (the future leading edge of the wing) when you do that you can lay the two sheets flat and put strip of clear standard weight package sealing tape over the folded edge to repair it.
01 - Draw the cutting lines on the top sheet, I use a fine tipped permanent marker. The layout for the KF2 wing is the same as for the KFm4 wing in the drawing. The only difference is that the KFm2 wing only has a single step on top of the wing (the KFm4 has steps top and bottom).
02 - Cut through both sheets all the way across at the line that is the bottom of the wing center panel (that is the line where the trailing edge will be at the wing center.
Keep the utility knife inclined back as far as possible when cutting to avoid snags in the skin on the bottom or the foam. I follow a long straight edge and use two or three passes to cut all the way through.
03 - Turn the sheets so you are cutting only on the top sheet and cut out the areas from the KFm2 strip back and in to the center panel. Start your cuts with a plunge cut at the line intersection, avoid leaving crossed and overcut lines as it will will invite a crack starting there later.
04 - With the waste removed you will have a wing center panel that is 11-1/2" x 48" and attached to it at the leading edge is the one piece KFm2 strips and the center panel. Another center panel filler will be cut from the waste later to go beneath the center panel. That will strengthen the wing center and fill the area beneath the center panel.
05 - Take one of the pieces that was cut off of the bottom of the wing cut two 1-1/4" x 48" filler strips. One of these will support the KFm2 strips up near the leading edge and the second will support the back edge of the KFm2 strips and also form the lower half of the step that is there. Peel all of the skin off of the filler strips by picking one end up at a slight angle to the foam and lifting it. If you lift it at too steep an angle it will tear at the pin holes and you'll have to pick it all off in little pieces.
06 - The arrangement of some of the parts is seen here. One of the 1/4" x 31" long dowels is up near the folded edge and one of the filler strips is just behind it. Center the dowel on the 48" wing panel (8-1/2" in at both ends) and make a line to mark where the ends will be. Fold the KFm2 strip and center panel down until flat on the wing panel. That may cause the dowel and filler strip to move back a little and you want to allow them to do that.
07 - Raise the KFm2 strip up without moving the filler strip and then draw a line along the back edge of the filler to marks it's location. The line is seen draw here and the other marks are for the dowel ends.
08 - Lay the dowel aside for now. Spritz the area from the line and forward with water (I use a small fine spray plant mister). This is a key part of making the any PU glue foam up and work right. Run a bead of glue down the filler strip and spread it evenly across the foam. Hold the strip to the light and make sure the full width has a light, even, coat of PU glue on it.
09 - Place the filler strip with the glue side down and align it with the previously drawn line. Weight it to bring it into full contact and give it 10-15 minutes to set up (for Gorilla Quick). Make sure the end are weighted so that the foaming action does not raise them up.
To be continued...