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Old Nov 09, 2010, 11:24 AM
jackerbes is offline
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USA, ME, Ellsworth
Joined May 2008
18,096 Posts
32" KFm3 Flat Wing Build - Part 3

32" KFm3 Flat Wing Build - Part 3

21 - Clamp or Weight Parts - I placed flat board on top of the part and place the necessary weight on top of that, more will be added to the short exposed area on the left end. Check the alignment marks several times in the first minute or two or it might slide out of alignment.

22 - Let Glue Set Up - I spritz water on the spreader and lay that aside on the can lid so I can tell how the glue is setting up. The excess glue on the spreader will foam up start setting and when you can touch it and deform it without it sticking to your skin you can work with the parts again. If it sticks to your skin give it more time. The 15 minutes is OK for parts like this that will not spring apart or pop apart from pressure in the assembly, you can unweight them in 15 minutes or so. For anything that has more pressure and wants to pull on the glue, I give it an hour or two.

23 - Glue Filler 75% KFm and Filler Strips - The KFm 75% strip and the Filler strip have both been glued into position in this photo. The plastic skin has also been removed from the top of the filler strip also in preparation for it being glued to the 50% KFm strip when it is folded back.

24 - Parts Arrangement - This is the tip of the wing with the parts glued in place. The slight amounts of stagger or overhang on the dowel and the ends of the parts will be trimmed even later.

25 - Trim 50% KFm Strip - The 50% strip has to be folded back two times. The first time will be to transfer the marks from the 50% line on the wing panel to the 50% KFm strip. Then the strip will be trimmed, folded down again, and glued into place.

I hold a board against the back of the 50% strip to help it fold down evenly and I also have some weights handy to place on top of the board once it is folded down.

26 - Fold and Mark 50% Strip - With the 50% strip folded back I make a mark on the 50% strip in line with the 50% line that is on the 75% KFm strip and the wing panel. This is so I can trim the 50% strip to be even with the line.

27 - Check Leading Edge - Look at the leading edge and make sure the dowel is centered, that the tape is holding, and and that everything looks OK there. The combination of the tape and beveled edges on the FFF really pulls itself together into a very straight, smooth, and durable leading edge.

28 - Trim 50% Strip - With the 50% strip unfolded again, use a straaight edge to trim it even with the marks made when it was folded. This will put the step right on the 50% line and make sure it is straight.

29 - Refold and Glue 50% Strip - PU glue was applied to the top of the Filler Strip and the area where the plastic skin was peeled off of the leading edge side of the 75% KFm strip. The back of the 50% KFm strip was spritzed with water, and it was folded down on top of the other strips and weighted down.

A visual check was made to ensure that the FFF panels were in contact all the way across, another board and some more weight was added on the right end to get the assembly evently weighted all the way across.

30 - Check Leading Edge - A quick check of the leading edge and everything looks good there too. I'll give this a couple of hours to set up or even overnight because the strip want to spring up, even when the glue sample is completely dry and cannot be crushed with my fingers, might be too soon. If I'm working in the evening, I would do this last thing and call it a night.

31 - Finished Wing Assembly - That finishes the wing. I use a razor saw to trim the dowel ends and a sanding shingle with 60 grit open grit sandpaper to sand the ends of the wing flat and vertical. This is the point were it starts getting exciting! This all foam wing has a very nice combination of stiffness and resistance to bending forces and the strength is very well distributed. The wing weighs 85 grams or 3 ounces at this point.

I'll follow up with more details on finishing the wing in my next post.

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