RE: Balsa USA 1/4 Scale J-3 Cub
Hi PA PEN
You gave the wing span as 108". If you divide 108 by 2 you get 54. Divide 3/4" by 54, then get the arc tangent you get .8 degrees. That is just under one degree. I would call that a straight wing. This is high school trigonometry which I learned around 1952. Love it. If I screwed up others will chime in. I just reread what you wrote; "from the top of the fus. to the string". I assume that fus. means fuselage. Frankly, I do not understand the directions now, so you can disregard everything I wrote, but I decided not to delete what I wrote. I mistakenly assumed that you were referring to "from the top of the wing center to the string". On your plane the wing center is a portion of the wing that is permanently attached, screwed, glued, etc., to the top of the fuselage. The two wing halves are then attached to this central wing portion. Please take the following with a grain of salt. I have built two 71" Sig J3-Cubs, and my own design of the same plane, built from Coroplast, so my plane is a SPAD. I have studied the method of construction of your plane, specifically how the two wing halves are attached, and I see a very weak condition. I am not an expert in this area. I suggest you contact others who have built this plane and ask them if the method of attaching the wing is correct and adequate, based on the photos that you have provided. I have been flying R/C since 1972, and based on what I have seen, I would not fly that plane. I want you to understand that I do not feel comfortable writing this, and urge you to contact others who know more about it. I would like you to let me know the outcome of this. I have been wrong many times in my life, and one more time will just make me grin, but I will have learned something else. I am a retire Mechanical Engineer, and I ask you not to let that influence you in any way.