On Tue 09 Nov, Scobie Puchtler or Sarah Felstiner wrote: > A pal of mine who is new to RC but a talented engineer came up with a > fascinating mechanism to translate two channel control into a fully > articulated tail boom. His model had a lot of practical problems, but was > fascinating to watch, and could clearly be made to work. I've gotten started > a few times on some bird-like control systems (not the articulating tail, > exactly, but some other funky ideas) but have gotten distracted by other > (slightly)more practical projects. If you get any other good sources or > comments on avian aerodynamics, please share! Thanks. The model I saw had a Lancaster-like tail section, which was hinged at the wing trailing edge, with the servos acting as counter-weights, I guess - doesn't nedd to move much for great efficiency! What I have in mind is a bird-like tail - inverted V-tail, quite long, say concisting of two 30-60-90 triangles, with the pointy tip forward and the 90 degree angles back to back, so to speak. Such a tail will never stall, that's for sure. I would include tailerons in it, for roll control, but it would move sideways for rudder. For trimming purposes the batteries would be movable (on a tray, up in the 'head'), as for landing (high CL) you need bigger rudder + fin area. Birds do it by moving the heavy legs forward, and to improve stall characteristics, they introduce some forward sweep, increases the size of the tail (increased stabilisator area and fin area), by spreading the tail feathers like a Japanese fan :-)! And they deploy gigantic flaps and flap their wings energetically, to increase maximum CL further and to increase thrust, which is to a great deal angled downward, the birds landing with their fuselages more or less vertical! And seabirds spread their feet, which acts as very efficient air brakes. The only birds that really haven't learned all these tricks are those that have a very high wingloading, making this kind of semi-hovering impossible. Typical are swans, swifts & albatrosses, which all need lots of speed to fly and make very high speed approaches. Loons are even more extreme, I guess! What they gain is effiency, with the mute swans having flying weights of up to 40 lbs! So these guys operate on low Cls, while a gannet, which also is an efficient bird, can use all the tricks above: Wing forward, feet down and spread, tail down - nearly 45 degrees, to compensate for the forward position of the wing and to counter the nosedown momentum of the flaps, while semi-hovering at max Cl. To ensure that the wing stalls as late as possible they have great help form the small feathers on top of the wing - if a stagnation bubble is created these small feathers rise throught the stagnant air and reattaches the airflow, and if the circulation reverses, they lift, too, like Kasper flaps, and increase lift further! Yours, Tord, Sweden *'`'*.,.*'`'*.,.*'`'*.,.*'`'*.,.*'`'*.,.*'`'*.,.*'`'*.,.*'`'*.,.* -- If reply difficulties - use [EMAIL PROTECTED] Tord S. Eriksson, Ovralidsg.25:5, S-422 47 Hisings Backa, Sweden RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
