Oh, and what power system are y'all using, Jeremy? We're using the Astro 60 geared on ~36 2400 mah cells. We get about 11 lbs of thrust from this setup, and it lasts for nearly 5 minutes.
Posts: 91
Joined: 4/22/2002 From: Champaign,
IL, USA Status: offline
What prop are you guys using? I seem to recall maybe a 24X12?
We don't have quite the headroom that you guys do on propulsion. We run an Astro 60 w/superbox turning an 18X18 APC on 40 CP1300's. Static, it draws around 29 Amps, and we get between 2.5 to 3.5 of WOT time in the air, depending on mission, speed, etc. Static thrust is about 9 lbf uninstalled, and drops to around 8 installed. Our takeoffs aren't quite as authoritative as the one I witnessed SWAG-1 do, and we have less runtime, but I think our plane might be a bit faster. Depending on wind conditions, we may have energy trouble with the radome mission, but with management, I don't think it'll kill us.
I noticed that Junior has no apparent inlet for motor cooling. Have you guys checked motor temp after flight? Bryan had called me to consult about some battery troubles - perhaps the motor is overheating. Ours needs a decent amount of air to stay cool, and we even added a heatsink. If nothing else, it certainly looks cool!
Oh, if anyone wants to try out the Belle, I'm attaching my RealFlight model of it. It looks like a P-51, but flies like our little beast. Takeoff is actually easier with the real thing, though. Gotta hate that Realflight landing gear model. Just unzip the files into your Planes directory. Both the aircraft and the engine are in there.
_____________________________
Landing: Contest of strength between planet and aircraft. NOTE: To date, planet remains undefeated.
Posts: 91
Joined: 4/22/2002 From: Champaign,
IL, USA Status: offline
The Belle got a set of wingtip skids, too. These long-winged planes with high CG's need 'em. Mike Cross even touched one of them on Saturday. How did you guys approach it? We used some music wire "feelers" that do a nice job of popping the wing back up, but not too hard. I like 'em a lot, as I was breaking ailerons when I'd try to recover from a tip-down. Since the aileron needed to go down on the tip that was down, the corner of it wound up scraping - a great way to break loose a horn. Now, the skids stop it short, and take care of some of the recovery by themselves.
Also, how does the SWAG platform handle wind? I've found that the Belle has a real tendency to weathervane, making taxi operations in strong wind either difficult or impossible. Does your trike gear help with that, or have you even had to operate in windy conditions yet?
_____________________________
Landing: Contest of strength between planet and aircraft. NOTE: To date, planet remains undefeated.
Posts: 4655
Joined: 6/23/2002 From: Palmdale,
CA, USA Status: offline
[QUOTE]Originally posted by MarkVZ Oh, and by the way, our school wanted to do a twin-boom design like yours for optimal antenna placement, but it is in defiance of the rules to have part of the aircraft's structure obscure the 360 degree "view" of the antenna. I think the only exception is wing struts or landing gear legs. I'm not sure if the SAE competition has different rules, but your A-Tail design would not be legal with the antenna in that position. [/QUOTE] . I didn't see that fine point in the rules about the antenna view, just that it had to be 3 inches from structure. A later redraw on mine places the thing with the flat sides vertical, behind the fuselage, so the round side faces the airflow. And thinking further, it could be mounted on the "sensor" box so that after the box is deployed, it will rotate to the upright position. Just shows what a leaking mind can come up with! (Since finding a small r/c Humvee isn't panning out.)
Posts: 4655
Joined: 6/23/2002 From: Palmdale,
CA, USA Status: offline
You shouldn't read into rules the intent. If it's not specified, it's not a rule. For instance, both these installations fit the rules in my opinion. Unless there's a clarification somewhere, the antenna need only be spaced off the airframe... orientation not specified.
Posts: 91
Joined: 4/22/2002 From: Champaign,
IL, USA Status: offline
Paul, the 360 FOV requirement was actually made in the FAQ:
"Question: Can fairings be applied to the fuselage that “in effect” fair the antenna if they remain at least the specified 3” away. Answer: No. The statement “the antenna must not be faired in any manor” can also be viewed such that the “antenna must have an unobstructed 360 degree horizontal field of view”. An exception to the field of view will be made for the vertical tail(s) and/or wing struts. "
Otherwise, your "ahead of the nose" configuration would be an extremely smart way to go - the wake would impinge on the fueslage and reattach, substantially reducing the drag increment from the radome. Balancing would be the only problem I see, and could be taken care of by moving the payload for that config.
_____________________________
Landing: Contest of strength between planet and aircraft. NOTE: To date, planet remains undefeated.
Posts: 4655
Joined: 6/23/2002 From: Palmdale,
CA, USA Status: offline
[QUOTE]Originally posted by Starfire ...
Otherwise, your "ahead of the nose" configuration would be an extremely smart way to go - the wake would impinge on the fueslage and reattach, substantially reducing the drag increment from the radome. Balancing would be the only problem I see, and could be taken care of by moving the payload for that config. [/QUOTE] . Prop clearance of the deployed payload is a problem. How to get the plane past/over the box after it's dropped, and not have the prop hit it... The number of ways to skin this cat....
Posts: 91
Joined: 4/22/2002 From: Champaign,
IL, USA Status: offline
[QUOTE]Originally posted by Tall Paul . Prop clearance of the deployed payload is a problem. How to get the plane past/over the box after it's dropped, and not have the prop hit it... The number of ways to skin this cat.... [/QUOTE]
Not if you pitch the payload out the side!
Sound crazy? Yep. It works, though.
_____________________________
Landing: Contest of strength between planet and aircraft. NOTE: To date, planet remains undefeated.
I originally installed angled plates in an attempt to direct the inlet air around the sides of the batteries, but those have since been removed. I also cut louvers in the tops of the battery boxes. The batteries seem to be delivering more power and staying cooler now. Heatsinking the motor sounds like a good idea.. our gets almost too hot to touch after flight. Regarding the Astro 60, it seems like there's some animosty towards us because Astro seems to be telling people that MSU got their last 60 for a while
Our wingtips just have the small nylon GP wingtip skids installed so that the wintgip doesn't get torn up on tip-overs like on the last one. They aren't there to prevent the tip, just minimize the damage. Because of the tall LG we try not to taxi SWAG. It will taxi, just tends to tip onto a wingtip if a corner is taken too fast. The nosewheel configuration keeps it straight on takeoff until the tail can aerodynamically keep the plane straight.
We flew today in a 10-15 mph crosswind and she handled fine. Our pilot didn't report any weathervaning tendancies. We got off in 120 feet no problem witht he full load. This could be the end of our flight testing, however, in order to reduce the risk of a mishap.
Have you tried the 4-lap mission with box and antenna? We can complete it, but not with much power to spare, even with our 2400 mah packs. We are swinging a 22-14 prop.
We assembled our plane in 20 seconds today without even trying to do it quickly. We hinged both our main gear and nosewheel and it just takes a quick flick of the wrist to latch it. Our aileron servos plug in when the wing panel gets plugged in. It's a lot different from our last one.
Have you tested your box-firing mechanism yet? I was just wondering if the kickback from the box would try to tip your plane over. I really want to see it in action!
Thanks for looking up the antenna thing... it *was* in an FAQ and not in the original rules. MSU scrapped the twin boom design after we asked them about that and they answered in the FAQ. I'm almost glad we did, because we see minimal effects from the antenna where it is now. It's not as big a deal as we once thought.
Hopefully Bryan gets updated pics of SWAG Jr. up soon!
Posts: 91
Joined: 4/22/2002 From: Champaign,
IL, USA Status: offline
Haven't done the radome mission in its entirety yet - that's on tomorrow's agenda. However, given this thing's climb rate and glide ratio, I doubt we'll be in too much trouble there. Even if I can't fly it WOT the entire time, I'm pretty sure that I can fly a motorglider type profile if needed. Also, while our setup doesn't take off quite as well as yours, we do fly faster and draw less current, I think. It's all in the tradeoffs. What does your setup draw static? Motocalc seems to predict 40ish amps... sound right?
And yes, we've successfully dumped the payload several times. Works great, and has no tendency to knock over the plane.
Well, off to bed.
_____________________________
Landing: Contest of strength between planet and aircraft. NOTE: To date, planet remains undefeated.
Posts: 691
Joined: 6/21/2003 From: San Diego, CA, USA Status: offline
Greetings fellow DBF-ers!
I just want to say congratulations to everyone who was part of the DBF competition this year. It was a lot of work, but it was great fun to see all the different teams and check out the many different design philosophies. I hope you all continue with the competition next year as well!
I've been building models for many years, but this was my first time with DBF and it was quite a thrill. I'm a grad student in chemistry, so there were challenges just finding time to get together with the aero guys. Below is a pic of our plane... it might look familiar to some of you.
Printable Version
All Forums >> RC Airplanes >> Aerodynamics >> UIUC AIAA Design/Build/Fly Project 
UIUC AIAA Design/Build/Fly Project - 
(Since finding a small r/c Humvee isn't panning out.)
