skwier
Active Member
Beginning a design of an ultralight (US 103) to fly from a base near 5400 feet (1640 m).
Yesterday we had gusts to 39 mph (63 kph) with airs temps to 85 F (30 C) in clear air and no clouds within 10 miles. Take off in those gusts would be foolish, but they came up very suddenly out of a blue sky and you might have to deal with something like that after you were in the air.
Please suggest sensible choices for the following or for other relevant parameters. I am thinking of a high wing tractor with aluminum tubing frame. So far this is of course a conceptual design, to see what is possible; constuction details to follow if it seems reasonable.
air foil section - which one?
wing aspect ratio
wing loading
power loading
dihedral
based on my limited knowledge in this area, I would make some first guesses:
to deal with thin air and hence reduced lift, go to a high L/D wing section, and a higher aspect rato (say 5.3 +) .
to reduce wind-gust-induced roll at low speeds for landing, go to lower aspect ratio ( say 4.0 to 5.0)
to reduce wind-gust-induced roll at all speeds and general better control, go to higher wing loading, say > 4.0 pounds / square feet (on gross weight)
to reduce wind-gust-induced roll at all speeds, no dihedral.
to reduce wind-gust-induced roll at all speeds and general better control, go to higher power per weight,
say < 11.0 lbs per horse power.
Stuart Wier
Yesterday we had gusts to 39 mph (63 kph) with airs temps to 85 F (30 C) in clear air and no clouds within 10 miles. Take off in those gusts would be foolish, but they came up very suddenly out of a blue sky and you might have to deal with something like that after you were in the air.
Please suggest sensible choices for the following or for other relevant parameters. I am thinking of a high wing tractor with aluminum tubing frame. So far this is of course a conceptual design, to see what is possible; constuction details to follow if it seems reasonable.
air foil section - which one?
wing aspect ratio
wing loading
power loading
dihedral
based on my limited knowledge in this area, I would make some first guesses:
to deal with thin air and hence reduced lift, go to a high L/D wing section, and a higher aspect rato (say 5.3 +) .
to reduce wind-gust-induced roll at low speeds for landing, go to lower aspect ratio ( say 4.0 to 5.0)
to reduce wind-gust-induced roll at all speeds and general better control, go to higher wing loading, say > 4.0 pounds / square feet (on gross weight)
to reduce wind-gust-induced roll at all speeds, no dihedral.
to reduce wind-gust-induced roll at all speeds and general better control, go to higher power per weight,
say < 11.0 lbs per horse power.
Stuart Wier
