Performance Data

[Kalayzor]

Hello to all!!

I am part of a chapter of the American Institute of Aeronautics and Astronautics at Daniel Webster College in Nashua, NH. We're participating in the the AIAA's annual Design/Build/Fly competition, and I need some help concerning flight data from model aircraft.

The challenge is to build a radio controlled aircraft from scratch to perform a series of challenges, mostly involving carrying different weights (up to ~14lbs) around a racetrack course. However, the major component of this, that my group is worried about at any rate, is a restraint that our aircraft must take off in 100ft or less.

Right now, we're (our subgroup) is trying to figure out our wings. While we're researching different airfoils, possible construction/materials to use, etc, we also want to design to a reasonable specification. So, I'm wondering if anyone around here has data on their aircrafts' best rate of climb...and, if so, if they'd mind sharing it. I'm looking for GA catagory aircraft, particularly those built for heavy lifting/STOL operations (Super Cub, etc) though I wouldn't object to Cessnas, etc. When you post, please let me know not only the best climb rate but also the type of aircraft it's for, motor used, current draw for the motor, prop diameter, and any fiddly things done with the wings, if possible.

Thank you!

[vintage1]

Climb rate, once you get an efficient motor prop weight, is entirely power/weight ratio.

Think in terms of gain of potential energy and do your analysis based on that.

Cruise power is pretty much drag to lift ratio times speed times weight.

Cruise Flying speed is the square root of wing loading.

So to get the most efficient load carriers, use loads of wing area, and enough power to lift the weight you want as fast as you want to.

If lifting power is more important than cruise speed, use flaps or an undercambered wing.

If cruise efficiency is important, use a slender elliptical style wing, but beware, these are tricky to handle in low speed turns and will bite you.

Most model aircraft will take off in less than 100ft, if they have enough wing area. Or power. power to weight and a reasonable prop will get you up to flying speed ..you can work out what thrust to weight will get you comfortably over stall speed in under 100ft.


I would certainly be looking at something like a 8ft span plus vintage model to carry 14lb of payload, with a bloody great undercambered wing.

Here's one I took last weekend.

I'd say that would just about carry 14lb of payload. Probably weigh about 25lb AUW and need something like 1500W or a couple of horsepower of engine. Wing could have more chord to get takeoff/landing speed down. 2bhp is about a '150' 4 stroke. (25cc). 1500W is a big electric motor and battery! Either will work.

second shot is the slowest plane that day. Not low drag, but very low wing loading.

Wing section is not hugely critical at model Reynold numbers, especially for this sort of application. The key thing is a fairly deep section, for structural strength (about 15-25% depth to chord) and a bit of undercamber to bring the stall speed down. And lots of it to carry the payload.

Are there any points for speed or efficiency?

[mnowell129]

Vin,
AIAA Design build fly has specific criteria. Must be electric. Battery weight is 4 pounds max, must used nicad or nimh, max current draw must be 40 amps.
This is basically a 40 cell sub c pack.
There are other criteria..
rules here:
http://www.aiaadbf.org/2009_files/2009_rules.htm

[vintage1]

Vin,
AIAA Design build fly has specific criteria. Must be electric. Battery weight is 4 pounds max, must used nicad or nimh, max current draw must be 40 amps.
This is basically a 40 cell sub c pack.
There are other criteria..
rules here:
http://www.aiaadbf.org/2009_files/2009_rules.htm


Ok. that fits neatly with the 1600W I reckoned would be needed for a fully loaded plane. 40V x 40A :D

Looks like speed and manouverability would be useful, but not cruise efficiency, so a moderate aspect ratio is OK.

I'd be torn between mild undercamber or flat bottomed, with flaps.

The requirement to get it into 4' long boxes probably means it will be 96" span max. So a fairly broad chord works. Probably need detachable tail feathers as well.

Interesting exercise.

[Brandano]

I'd launch with a bungee assist too. Never mind me, am Italian, we always try to bend the rules. :)
[edit:] Darn, they tought of it already! (/me just read the rules)