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Old May 06, 2005, 01:33 PM
I Love 30mm
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United States, TX, Wichita Falls
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Yippee!
Aero Engr Design Project Build Up

Howdy everyone, I just wanted to say hi and introduce myself. Ive been around on the board for a few years but since ive been busy with college I havent done much with the hobby since high school. i used to fly helicopters, and im looking to get into edfs or something.

Im a senior in aerospace engineering at Texas A&M and we just finished the design semester of our design project. we had to design a 4 seat high speed business jet (think along th elines of the maverick leader or the eclipse...except faster ). next semester we will begin the build phase where we build a wind tunnel model, and then a scale flying model. this should be a great way for me to get back into the hobby and learn a lot at the same time, as it will be my first airplane build.

im sure we might need some help along the way. we have a great faculty who teach and help who have been in the hobby for many years as well, but its always good to hear other opinions. we would really love to try either a gas ducted fan or EDFs, but past students have had a low success rate with the nitro DFs and this year was the first year they have tried EDFs.

We dont start he build untill next semester, but were starting to research and plan out our configuration now. I will keep yall informed. Oh yeah, ill post some pics and specs later on when i go up to the lab. Laters!

Ryall Meyer
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Old May 06, 2005, 03:18 PM
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Punta Gorda, FL
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Do not begin with the design or the power plant! First, you must do the system engneering by picking the aircraft performance, purpose and other priorities, like cost, range, speed, take-off distance and landing distance.
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Last edited by Ollie; May 06, 2005 at 03:23 PM.
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Old May 06, 2005, 04:18 PM
I Love 30mm
FlyinAg's Avatar
United States, TX, Wichita Falls
Joined Nov 2001
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if your talking about the full scale design, weve already done all the designing for the full scale aircraft, we did that the whole past semester, the upcoming semester is the build phase for the models. were trying to figure out how we want to build/confidure the flying model. we can make a large scale or smaller scale...it would be cool to use ducted fan because our plane uses burried engines, but if it proves too difficult we will just have to put a prop in the nose. i think our biggest worry is getting enough thrust out of a nitro ducted fan becuase i hear you have to get teh ducting jusr right. the flip side of that is using edfs, where we are concerened with aircraft weight and ducting...yall will see how difficult it may be to do this when i get some solid works and autocad shots posted.
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Old May 06, 2005, 04:27 PM
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Ryall
I'm involved with the A&M group and you're correct that this was the first year with an electric ducted fan. The power system worked well and after some changes the model flew well. In the past the IC ducted fans have suffered because the margin for error in the setup is small. It was a shame not to be able to test a design because of the power system.

Considering that the majority of the students have no modeling experience it truly is amazing to see them design and complete flying models an a rather short time. I would suggest staying with a conventional layout for the best chance of success. Teams in the past have had limited success with exotic things such as joined wings and forward swept wings but the added complexity lowers the chances for a good flying design. It would be different if you would have the time to tweak everything. Keep it simple and you'll most likely succeed on the first try. And remember there is a lot of help available when you need it.
Best of luck.
Paul
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Old May 06, 2005, 06:03 PM
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Howdy Paul, thanks for the advice. Are you one of the pilots who comes out to help fly?
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Old May 06, 2005, 06:22 PM
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Yep, that's me, and let me know if I can be of any help to you or your team.
Paul
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Old May 06, 2005, 06:28 PM
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Here is a photo of the twin EDF (Wemotec Midifans) model. It crashed on the first attempt and after a 7 hour!! rebuild with a few changes it flew later the same day. What dedication!
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Old May 06, 2005, 08:03 PM
I Love 30mm
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United States, TX, Wichita Falls
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yeah i heard the story from some of them up in the lab. i wish i couldve gone out to see them fly this year, but i couldnt. i went last semester when they flew the white uav design with the drop of landing gear. that was a nice one
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Old May 08, 2005, 02:49 PM
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United States, TX, Wichita Falls
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howdy again. here are some pics of our aircraft. there's an autocad 3 view, a solidworks structural model, and a solidworks 3d view with flames lol. there are some minor changes taht we have made. the duct entrance cross sectional area is different. its a d shaped design. the engines have also been spaced apart some. what do yall think? it would be so awesome to do a medium or large edf setup, but im really worried about ducting and engine setup.
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Old May 10, 2005, 10:30 PM
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Bedford, Tx
Joined May 2004
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Can I help

Those wings look really small? ? ?
did you scale down a full size model ???
have you calculated the wing loading of this design?? as an RC plane.
it looks like it will have to fly really fast to stay in the air with such small wings.
I would like to help any way I can. I am a good builder and any questions you have, someone on RCGROUPS is sure to have an answer.
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Old May 10, 2005, 10:38 PM
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Nice looking design. If you are wondering about how to make ducting let me know.
Paul
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Old May 10, 2005, 11:41 PM
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United States, TX, Wichita Falls
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Quote:
Originally Posted by Julian537
Those wings look really small? ? ?
did you scale down a full size model ???
have you calculated the wing loading of this design?? as an RC plane.
it looks like it will have to fly really fast to stay in the air with such small wings.
I would like to help any way I can. I am a good builder and any questions you have, someone on RCGROUPS is sure to have an answer.
that is the full scale, we havent done anything with the model design. the aircarft is of our own design, designed from scratch...the wings do look deceptively small, but they are the right size for the full scale. keep in mind the plane is really really small...its only 29 feet long and its wingspan is 27.5 if i remember correctly...wing area is 79 square feet. fully loaded takeoff weight is about 4900 pounds. another thing that makes the wings look so small is its fat fuselage.

the other two teams in my class suffered from the same problem: the aircraft are small, but the fuselage has to be wide enough to carry four people comfortably. this gives you this short stubby little fuselage that can look a little disproportionate at times. im anxious to see how the aircraft scales down because i too have thought about how these small highly swept wings will perform on a model. the full scale aircraft uses fowler flaps that extend over about 70 percent of the wing, so we have a landing stall speed of only 75 kts, yet our software and intuition says that this plane can go above mach .8 easily.

another problem these short stubby fuselages cause deals with stability and control. if you notice our vertical tail is huge. in order to get a large enough C_n_beta for proper cruise stability we have to have lots of tail area. were workin on some sort of strake to help out and take a little area off the vertical tail. im not quite sure how stability and control will all work out on the model either.

if anyone else is interested in any of the other specs, lemme know because i would love to share and talk about our trials and tribulations. i appreciate the response ive gotten here already, it looks like im in good company i cant wait to get the ball rolling on the build!
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Old May 11, 2005, 10:31 PM
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Bedford, Tx
Joined May 2004
234 Posts
How far down are you going to scale the model to? 25% 20% 15%
I calculated with your 27.5' wing span. here are the results. 6.875' , 5.5' , and 4.125'
Here are the conversions to inches. 82.5", 66" ,49.5"
The reynolds numbers on a model become more realistic with a larger wing area. This means that your airfoil will work better the larger it is. I would opt for the 1/4 scale or 25%, this will also give you more margin for error in your airfoil. Calulated at 25% your wing area would be 19.75 sq ft. 2844sq inches. Now this is good size for a model. With this we can figure up some wing loading numbers to get your ideal weight. If this model weighed 15lbs or 240 oz then you would end up with a 12.15 oz sq ft
wing loading. at this level it would float and fly really nice. 18-25 oz per sq ft is not unheard of in the hobby. The smaller you get with the size of the model the more weight is a penalty. This is when building lite becomes a huge factor. Weigh all of your components if you can before you decide on the size of the model. I know you guys carry some kind of telemetry and cameras on board. this also has to be calculated in the total weight of the components.
Fowler flaps???? do you already have a design for these on the model. I know many that have tried to make these. It can be very complicated on a model. There is a good model design book available that you may want to look at. http://www.amazon.com/exec/obidos/tg...glance&s=books
http://www.amazon.com/exec/obidos/tg...=UTF8&v=glance
this second book details flaps and there use on RC planes. He has some very good information on how they make the plane react?
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