3D 4 ME

I'm currently designing my first scratch built plane and I was just wondering which wing design to use. I've narrowed it down to 3 choices. I need as little drag as possible without sacrificing stability. The reason, because I need to be able to reach high altitudes. I'm designing a high altitude research aircraft with rockets on the sides to reach higher altitudes than other planes. So, with that being said, I need suggestions on which of these designs I should use. (sorry if they look light or are hard to see, I can't take off the flash)

Laird SS

If you're really trying to go high, make sure you have FAA approval for any flight you make. Otherwise you could get into more than a peck of trouble.

Just a suggestion.

3D 4 ME

Well, I wasn't really thinking of going as high as a full scale plane. I'm hoping to reach just under civil airspace. But in case it comes to that I'm planning on flying somewhere with low air traffic.

Sharku

should have read more carefully

id go with 3 due to more lift

dolanosa

Still too many variables.
How high do you want to fly? Must have the right airfoil.
Duration? How long do you want to stay up at what power settings?
Airspeed envelope? Landing speed, cruising speed that you want.
Total estimated weight? How much do you want to lift with the wings?
Rocket to be used? If you don't want to make your own motors, you can at least maximize your fuel burn here.
etc...etc.

By the way. is there a reason you're using a wedge shape? I assume that you want to go pretty fast with the rockets but the shape will probably slow you down.

For cool factor, I pick #3

build light

I think it is clear that you haven't thought this project completely through which is one reason to ask questions. Good choice.

What kind of control do plan on using for this craft?

How big will it be, or maybe I should ask how small will it be?

How far apart will the rocket engines be from each other?

What kind of airfoil will you be using and what will be the percentage thickness?

Are you planning on using propeller power to some altitude and then lighting off the rocket motors for more altitude?

Quote:
"I need as little drag as possible without sacrificing stability."

Decreasing drag usually does not create instability.

Quote:
"The reason, because I need to be able to reach high altitudes. I'm designing a high altitude research aircraft with rockets on the sides to reach higher altitudes than other planes."
Quote:
"Well, I wasn't really thinking of going as high as a full scale plane. I'm hoping to reach just under civil airspace."

These two statements seem to be in contradiction. How do you reach higher altitudes than other planes and yet stay below civil airspace?

Quote:
"(sorry if they look light or are hard to see, I can't take off the flash)"

Put a small piece of electrical tape over the flash, then after use, remove tape.

Umm what sort of research will you be wanting to do? I love an interesting project!

Good luck with the build! I like number three as well.

Robert

batchelc

My Feedback: (7)

Wing stability (making the wings stiff enough) will be a challenge for the first two.

Before you "fly high" you should check with the AMA first. Generally "civil airspace" goes to the ground or 700 or 1200 feet in most places.

FlyerInOKC

My Feedback: (6)

If I remember correctly models are limited to a 500 ft. rule. Check the AMA rules they list the limit. Anything above that and you won't be covered by there insurnace. Don't forget the AMA requires a waiver if you go over a specific size and speed. Just hask the turbine drivers on that one. You maybe required to make a notification to the local air traffic control if you go above the modeling limit. The FAA is not very forgiving on stuff like that and Homeland Security has been known to get envolved.

3D 4 ME

Well, I've thought about the aircraft's dimensions, powersource, control systems, and stuff. But I think the most difficult task I have right now is building a 3-dimensional plane out of flat depron sheets. I have no idea how I'm going to do this. I don't even know what the bottom of the plane is going to look like. The drawings I posted are just examples for the wing design, the fuselage and canards are just to give a general idea of what the plane's shape will look like. I have another drawing that shows where all the components will go but it's rather small and has a different pair of wings. I have somewhat thought out how to overcome some problems but I did underestimate how difficult scratch building can be.

3D 4 ME

I figured that the swept back shape would allow for more speed. It's going to be a single EDF jet with estes rocket motors on the sides. I assume that square wings will create unwanted drag and prevent the craft from reaching very high.

build light

Scratch building does not have to be difficult.
It just now occurred to me that you may have complcated things a little by also wanting to try designing an unproven model.
Could be you might leve out the design part for now and just stick to scratch building. While building an existing design from scratch you will probably get ideas for the model in this thread that you will want to use. Write them down! Give your intended design a name or some kind of designation and keep a notebook of it. Later, when you become more experienced in building then the design work will come much more easily.

I know what its like to get all excited about a project! Gotta love the excitement of it all!
Don't back down, just change courses a little and steam full ahead and don't slow down. This excitement needs fuel and you need to feed the hunger my friend!

If you were thinking that building from scratch ment you had to design your plane, then you better design youe engines or motors as well!

No scratch building means not having pre cut or preshaped parts assembled in a box that you merely assemble together.

Design work is more tedious and has more steps and stages when starting out.

Always remember to have fun while doing this!

Robert

batchelc

My Feedback: (7)

At 200 knots or below typically sweeping the wings will not gain you an advantage drag wise. Sweapt wings typically give you an advantage near critical mach. other than that they move the CG and make the wing worse at low speeds. Sometimes designers do this to get the CG in the right place though.

http://books.google.com/books?id=C8Z...o+aerodynamics

The above is a great book to learn the basics.

With foam sheat you will most likely have a problem with torsional stiffness of the wings.

You may want tto buy extra foam and just have a go at it.

I would reccomend that you call AMA and check on the regulations attaching pyrotechnics to R/C airplanes. You may be better off building it as a rocket with a cardboard tube.

3D 4 ME

Thanks. I know what you mean by building another model first, I'm planning on building some free flight gliders from plans by Dave Powers. After that I'm going to build a profile version of my design powered by a prop instead of an EDF, that way I can get used to it's flight charateristics. (even though profile physics are probably different) I just hope that my project won't stay on paper forever and that I can build at least one prototype.

3D 4 ME

Well, I wasn't planning on flying at an AMA field. Besides, I'm not just making this plane just because I want to fly a model beyond 500ft. I was inspired to build this model because I thought of a design for a full scale UAV that could reach beyond the limits of conventional turbine engines (hence the reason for the side rocket boosters). So I thought that if I wanted that to become a reality I should prove it's effectiveness on a smaller scale. Which is why I drew that plane in the first place. I don't know, I think I'm just an ordinary 15 yr. old kid who wants to do something great.

Sharku

having second thoughts?

try going small making smaller scales then if it works try getting wind tunnel data , maybe if its good you could talk to an aerospace engineer [if you can] , there are also books about making UAVs

well thats what ive done.. just can really get my plane funded , i do have 3d drawings if anyone want to take a look at it ,

PS im only 14 , though my older brother is an aerospace engineer access to good info is all what you need try to work around your speed range and design the wing from that , there is not point on making a delta wing if your not going to reach mach 1 or above , you might also want to try making is quiet and reducing its radar signature [read books about surface to air stuff] if you could make something like that you might get a scholarship [basing on the country never went to the US so >.>]

Sharku

3D 4 ME

Not having second thoughts, it's just that I recently realized that it's not going to be easy. Although right now I don't have the time, I'm not giving up, I'm going to make it happen. Thank you all so much for believeing in me. As for the wing design I'm going with number 3, it's probably the most practical one, and it's more stable. Stability is what I need when it comes to a tail less design.

batchelc

My Feedback: (7)

3d -

Start by reading the book in the post above. That will give you a good foundation to learn the basics.

For stability and control you can usually make 1/4-1/2 scale foam board gliders to get an idea on CG. A gyro could also help you with some artifical stability. Try and design it to be slightly positive - not neutrally stable in pitch. You can always fine tune it with CG.

As for the rockets - I would start out with making a propeller version first and them gradually refine your design. Most good airplanes have multiple changes to the design prior to production. Then make sure you get all the correct permission and permits, and have a safety plan before attempting anything with rockets. The LAST thing this hobby needs is bad press from a 15 yo kid burning something down by accident.

BTW - I am an aircraft engineer and graduated from Embry-Riddle Aero Univ in Daytona Beach, FL.

3D 4 ME

Thanks. I'm going to order some depron to make some gliders. I have a gyro coming in the mail but it's for one of my helicopters. I need to buy a large quantity of materials and electronics so I can build several models without taking trips to the hobby store. (especially since my LHS is moving further away) I'll be sure to take all the necessary precautions before flying this thing, I don't want the world to see our hobby as something dangerous and think that it should be illegal. It's bad enough we have the EPA, FCC, and homeland security on our case all the time.

vertical grimmace

My Feedback: (1)

Also, you will find most high altitude designs have higher aspect ratio wings. So the #1 drawing would seem to be better there. I agree that I would get your design ironed out with the most efficient propulsion source available, a propeller. Then if a ducted fan or even a turbine is desired, you can modify the design from there.

3D 4 ME

Thanks. [8D] I've always liked #1 the best, I've decided to make a wing similar to #1 with the base of #3. I'm going to go with an EDF after I test it with a prop. I would get a turbine but I'm not rich. Infact, it hurts my wallet just to buy the $40 case of depron. So far, all I have right now is drawings. I'm going to draw schematics for the wiring and electronics this weekend. Keep checking this forum to stay posted on the project. I'm going to start a new thread when I start building. Thanks again to everyone for all the support.