ericmsil wrote: ↑
Fri Oct 02, 2020 5:12 pm
And as for the rear stabilizer, it certainly needs to be larger in size than conventional stabilizers. What about this profile of the rear stabilizer would you risk any profile? For this 1.0 x 0.16 m front wing? What would be the most favorable angle of attack for this mine to have a good reason for planning.? Thanks again.
I have been meaning to set up a program to optimise stab selection as well, but haven't gotten around to it. Also not too sure how feasible it is, since so many more details will be needed (More of a chore than needed I think). I usually just choose a neutral profile, that works for the expected Angle of attack range and Reynolds numbers. Then set it up with a angle of around 2-3 degrees to the front wing. Then tune it over a few sessions with some light shimming or fuse length changes as needed.
Can definitely help with some thumbsuck level checks when it comes to selecting a profile for low drag and to work in the expected AOA range and Reynolds number range though. But as noted you might need to tune it a bit to your liking with shimming etc. See below:
I have assumed something around the same size as the Axis 460mm Stab would suit in this case, a nice fast stab that seems to be very popular. Span of 460 mm and chord of 61 mm. So covering a Reynolds number range of about 150000 - 250000 in this case.
Angle of attack:
For the 12.5-22.5 Km/hr (s7075 profile) front wing the expected angle of attack range is +7.5 degrees at 12.5 Km/hr and -0.5 degrees at 22.5 km/hr. So assuming stab to be inclined about 2.5 degrees down compared to main wing it needs to have low drag and work in angles of attack in the range of +5 to -3 degree range.
Neutral profiles are generally the NACA00XX series. The last 2 digits indicating thickness as a percentage of chord. Looking at the range of 5% (NACA0005) to 15% (NACA0015). The Drag doesn't change that much with 10-11% doing best at the lowest end of the speed range and the thinnest profile (NACA0005) getting better as speed increases and AOA decreases. However the 5% profile would likely be impractically thin, only 3mm thick at the max chord of 61mm, the other negative is that it is very close to stall at the low speeds (stalling at about 5 degrees. While the 10% thickness profile (NACA0010) has a much safer stall angle of 10 degrees at these speeds and a more practical thickness of 6mm at the 61mm chord. So I would very likely recommend the NACA0010 for a stab profile in this case. And then tuning the angle to suit.