kid c

Not quite as simple as it seems. Basically, a designer must start somewhere. In order to have something to relate to as a base, a line is drawn from which everything is located, generally called a datum line, or base line. Yes, just a line on a piece of paper, but very important. Everything is measured and designed off this lline to locate the design and their relationships. If a wing is angled up of down compaired to the line, it is a positive incidence or negative incidence. Same with elevator and engine. Built a pattern plane for a friend a few months back. It called for 1/2% positive and 1/2% negetave in the wing and elevator. Had to laugh at that cause there are not many people that have the equipment to correctly measure 1/2%. The typical mechanical units you buy can not measure that close, few people have a crutuch or stand that will keep everything in place that well. The new "Smart Levels", digital type will correctly measure to 1/10th of 1 degree. You can get the job done right with one of these. Trouble is a decent one is around $75. to $100.00. Robarts and GP now make them for around $50.00 including the fixture, not sure just how much quality there is there. One click on your elevator trim is around 1/2 to 1 degree. Have you ever seen a home brew design that screams down the runway, but wont lift off the ground?, or one that flys but no control over where it goes. These are usually incidence issues. On the other extreem, a foamy generally has no airfoil, but can fly very well if designed and constrcted correctly. The wing produces no "lift" from design, but it does force the airframe in a direction from "angle of attack".

Before we go off thinking we are so smart, look at any bird gliding, and then at the general design of our present airplanes. Wanna real kick, go to a picture of the original Wright Bros. "Wright Flyer", and then to the latest design in aviation, the Eurofighter. Ahha, took us about 100 years to get back to where we started with the basic canard design of the brothers. Wonder just how smart we will be in the next 100 years?