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Q-talk 89 - Kurt's Corner

1) When mounting the wing or canard and measuring with a string, make sure the string does not stretch. Your checks will be inaccurate. I know this sounds obvious but I thought I could overcome this by hanging a weight on the line and passing it through a pulley to put a constant fixed tension on the line. By the time I had checked from one wing tip, to the other, and back to the first, the string had stretched 3/4". I had used a piece of 1/8" construction line from the home improvement store; the type you typically hang line levels on! Other lines not to use: fishing line, kites string, thread, nylon cord or rope. Good measuring 'line' to use: thin steel cable or wire cord.

2) When checking the distance for mounting the wing or canard, do not use the trailing, leading edge or tip of the wing/canard. It will be uneven no matter how well you cut the foam core. Use points just inside the edges but measured equidistance from the center point BL-00 Make sure to mark the points on the left side and right sides at the same locations in the cord for both ends. Use your BL100 templates, if unsure.

3) If using dry micro fill to finish the plane, make sure all batches are mixed exactly the same between fill layers. This is a manufacturing process and the more variation you eliminate, the better the sanding process will be. By insuring the ratio of epoxy-to-microballons is the same by volume for every mix, you are improving the likelihood of consistency between layers of fill. I have been in the manufacturing business for many years and can tell you that a stable process starts with mixing the same components together every time, no matter what the environment. You do not have to "adjust for the weather". There have been many myths about this but by eliminating the variation in the mix, and all that's left is the variation in weather, you can determine the best and worst times to apply filler.

4) Roy Shannon and I are trying the Polyfiber paint system on our aircraft. It is water based, safer and much easier to work with in your garage at home. While it does not shine like some oil based paints at first, it will with some buffing. I know there are many critics of these waterborne paints, but there have been a lot of improvements in the last few years, driven by environmental issues, that have forced the suppliers to make better paints. Remember, most paints are about 90 %+ carrier solution (solvent or water) and the remainder are solids. It is the solids that are left on the plane for the final finish. I can not tell you about the long-term condition of the paint job yet, but I like what we have so far.

5) (This one is for the new guys) Remember your only 90% complete when you are flying the plane. These birds are easy to modify (which will happen) with a some cutting, glassing and filling. Do not get too upset when you are not sure. If all else fails, follow the plans and change it later to suit your needs, AFTER you have flown it. At least by doing this you will have a baseline idea of what it was designed to fly like.


You can order a printed copy of Q-talk #89 by using the Q-talk Back Issue Order Page.