> From: "Scobie Puchtler or Sarah Felstiner" <[EMAIL PROTECTED]> > Date: Sun, 11 Feb 2001 22:20:52 -0800 > To: "Dave Seay" <[EMAIL PROTECTED]>, "RCSE" <[EMAIL PROTECTED]> > Subject: RE: [RCSE] Discus launch confusion > > The real story (in my humble, but strong-sounding opinion): > > Somebody obviously fluttered a set of ailerons discus launching at some > point Scobie, A good post on the subject. I'm one who has said ailerons will flutter on launch, and if un-reinforced, they will! Of course it all depends on the way the wing is put together. I'm talking about a stock wing that has been "kit-bashed" into submission for discus launch. The ailerons might be fine for a small launch, but over time and as launch speed increases, they most likely will flutter or the wing will start to crack specifically where the aileron ends near the tip. When I say "stock" wing, I'm also talking about a light lay up, maybe a 4.5 oz wing (w/out servos). There are many ways to design a wing to prevent this situation. Trilerons, faced surfaces, extra carbon all can work. It's just that you pay a slight weight penalty. Ironically, ailerons are not what is really needed to counter the yawing motion of the throw. The rudder is still doing most of the work. I've been flying a wing that has a center flap for speed control, but does not have ailerons. This is an easy structural reinforcement, as the forces seem to be taken in by the outboard panel before they get to the stress riser caused by the flap. There seem to be daily developments in the discus arena. My comments are based on what I have seen (and done) over the last 6 months. It is an exciting time as this facet of soaring is in a big evolutionary leap. A handful of us have been getting together on the weekend at a local field and we exchange ideas and go head to head with all the different planes. This is where you can see how different designs are working. I'll throw maybe three or four different discus planes and see how they respond to my throw. You can see right away what is happening during launch. Your comments on the balanced rudder are right on. A v-tail produces a lot of twist on the tail boom and it robs you of energy on the way up. Yes, it could be reinforced... My observation, after the plane is set up for discus, is that the design still comes down to two factors: Airfoil and Planform! Back to square one! JE -- Erickson Architects John R. Erickson, AIA RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
