Hi Aki,
It is nice that you have seen my plan as I learned a great deal from looking at the plans for your F1L's. As explained in the write up, the 210K is 210K psi where psi is the English dimension for pressure in pounds per square inch. The 210K psi is the elastic modulus of the balsa for the motor stick. The modulus can be measured using the Euler trick of measuring the force it takes to start to buckle the motor stick. The F1L motor stick is light and weak enough to be able to be buckled by hand. I also use a deflection method similar to that described by Larry Coslick in his Hobby Shopper series to confirm the modulus. Once one has measured the modulus and the density, the SC is easy to calculate. But, as I said in the article, I design using the modulus and a target deflection for most of the critical pieces.
I use metric (SI) measurements in my everyday life but for plans submitted to the AMA, I decided to use the normal (for the USA) English system. Bill Gowen, with support from Fred Rash, has given me much grief over matters of dimension. You can imagine how using Pascals instead of psi would have confused many US readers.
Good air and long flights,
Leo
---In Indoor_Construction_at_yahoogroups.com, <adanjo-373@...> wrote:
I found this description on Leo’s F1L plan on INAV website.
Motorstick: 4.7# 210K (129SC), 0.250”x 0.125”
What is the K?
How do you test such a thick wood to get the SC?
Aki
Received on Thu Nov 14 2013 - 20:51:02 CET