Any R/C aviators? I need some info.

[onewhippedpuppy]

As my AE senior project, a group of us are doing a design challenge. Essentially, we design an original aircraft to accomplish a specific goal, then compete in a series of challenges against other schools. Anyway, I have no desire to reinvent the wheel, and need some good sources for R/C airplane parts and materials. Production items will save us time, and also be of similar/greater quality than what we can build. We'll also need the over-the-shelf stuff like radios, receivers, servos, etc. Tower Hobbies is a big one, but anything you know of I will check out.

Before anyone suggests it, I'll add that I am also going to check out all of our local hobby stores. I just want to look at all options.

Also, we are now accepting sponsors!

[Tim Hancock]

Matt, as you probably know, when talking about small models, just about anything will fly if the cg is close. I have heard of guys mounting engines on record album disks and flying them. Don't get caught up in wasting alot of energy on airfoil designs. I have designed and flown a bunch of RC planes over the years and the most important thing is always to keep it VERY light. The other thing main thing to consider is that if you will be flying slow ONLY, you want big exagerated control surfaces/throws for maximum control at very low airspeeds. If however it will be flown at fast speeds also, big control surfaces/controls are not so good.

I can give you alot more info if you desire it. Just keep in mind that this small light stuff is much more forgiving than the real deal and a 1/2" foam slab wing will work just fine on a small light weight model.

[Hawkney911]

http://www.towerhobbies.com/


great place to get anyting hobby related

goodluck!!


wait looks like u allready had it down......nvm then

[berettafan]

www.rcgroups.com

many builders there. look for the foam builders forum. as Tim mentioned foam is the ticket. wing loading is key. you will want to use electric power if possible as it is very reliable. consider using things like carbon wing spars for stiffness. i believe the foam of choice is bluecor. it can be laminated and shaped just about any way you like.

i have had very good luck with Hi-Tec (sp?) O5S receivers (very small, light and cheap) and small Hi-Tec servos as well. your battery system can be an issue and will depend on the AUW of the plane. Lipo's are getting reasonable but handle them with the utmost care.

the lighter your plane the cheaper the power system will be. do not drop big bucks on AXI brand motors or similar. there are Chinese generics out there (www.gorillabobsshack.com is one example) that will do a fine job.

anticipated wind conditions will dictate your build, IMO. a 9oz plane will not like wind at all. a 6lb plane will have no problem with it (provided you are a semi experienced RC pilot).

what are the challenges btw? any payload capacity req'd?

[berettafan]

oh, and www.hobbylobby.com carries a better quality lineup in general.

btw, using a computer radio will give you more flexibility in setting up control surface throws, etc.

what's your budget?

[onewhippedpuppy]

Off of the top of my head:

Aircraft must fit in a 4 ft x 5 ft square. NiMH or NiCAD batteries only. Max battery weight is 4lbs. Electric motors only, as many motors as you want. Must take off in 75 ft fully loaded. 40A max circuit. Challenge is to carry a random combination of 14 water bottles ballasted to 1/2 lb, and 4 4x4 brick things at 1.8 lbs. As I said, it is a RANDOM combination of the two, and they won't tell us until the challenge. Max payload is a bit over 7 lbs. First challenge is empty airplane, fly as many laps as you can in 5 minutes. Scoring is # of laps/battery weight. Second challenge is with random payload, must complete two laps (no time limit). Payload loading is timed, mission score is 1/(loading time x empty weight x battery weight). Payload flights are not timed.

SO, important stuff is a lightweight but powerful battery, plenty of lift, good motor/prop match, quick load/unload payload, quick unloaded flight. We have lots of ideas, and I plan on picking up the lightest and best of everything that goes on the airplane.

[cmccuist]

One word - SPAD. You build planes out of the corrogated plastic that they make signs out of and PVC rain gutter. There are literally thousands of designs. And they're cheap to build and they patch up pretty easily WHEN you crash.

Lots of websites out there with free plans, sources, forums - like this one:

http://www.spadtothebone.com/

[onewhippedpuppy]

Also should add, we can change props between the two challenges. Hopefully can find a speed prop and power prop and switch them out.

[berettafan]

okay, tough but not impossible.

I fly a 6' wing telemaster with 14 Nimh's and the 3520-7 motor and it weighs in at approx. 6lbs unloaded. i also strap a 11oz camera under it and it actually flys better!

Consider the 3520-7 motor from Gorilla Bob and accompanying ESC. you will probably be pushing very close to 40amps carrying that kind of weight.

Batteries (Nimh) can be pch'd from www.cheapbatterypacks.com. They will custom up a pack for you.

I expect you will NEED carbon fiber spars to carry that kind of weight and you will use every bit of 5' for the wingspan.

[berettafan]

check out 'motocalc' for planning your system. it is a freeware program that will be of great assistance in ballparking your setup.

also, 5 minutes is very short run time for a plane capable of lifting 7lbs with under 40amps so you have some battery room to play with. consider having multiple packs made up to wire in series (ie 2x7 or 3x5 or similar).

[onewhippedpuppy]

Thanks Berettafan, bookmarked both.

Are you suggesting it might be an advantage to change packs for each challenge? We are allowed to use different packs between the empty and loaded challenges. I think we stand a lot to gain/lose with optimizing battery & prop to work with our motor, as well as for each challenge.

[berettafan]

well i'd defer to whatever Mike has to say about it (i am new to the hobby) but the idea of flexibility in pack size is simple to implement.

you'll need several packs charged and ready to go regardless. a 6lb plane with lots of lift (my telemaster is just that) would not be fun to fly at 1/2 the weight as you'd probably be putting in a lot of down elevator to maintain level flight. i believe (again, Mike may correct me) that your limitation in lifting 7lbs will be the amperage and your limitation in flying laps unladen will be wing design as a high lift wing (flat bottom, curved top) is not the fastest way around a circuit. perhaps some manner of flaps would be helpful. Mike?

if flaps become an option you will need at least a 6 channel radio with programming capabilities. I use a JR 6102 and am very pleased with it.

another thing to consider is gear or no gear.

[onewhippedpuppy]

I'm leaning towards simple gear, non-retract. Do they have wire gear that will support a plane with around 10 lb gross weight? As for the wing, my initial idea has been to utilize some form of flaps, possibly manually adjusted between challenges. You are right about the airfoil, anything with a lot of camber will have a lot of induced drag.

[onewhippedpuppy]

While the design must be original, you are allowed to use existing components for your original design. There is nothing that explicitly prohibits you from soliciting advice from others, you just cannot allow them to do your work or design for you. I'm simply gathering information.

Prohibiting advice from others seems like a very closed-minded way of doing the design. Might as well prohibit the use of any outside text sources as well.

[onewhippedpuppy]

Really, my primary goal with this thread was to gather info regarding sources for components and materials. Probably not the best idea to share our design on a well-travelled website anyway.

[cstreit]

10 lbs is really heavy for an RC plane, you probably want to look into the aluminum gear rather than wire gear. The strength of wire gear is okay, but the load it palces on the airplane at hard landings is brutal. With a wide aluminum piece, that load is better distributed.

[Tim Hancock]

Matt, aluminum thin walled arrow shaft (archery stuff) is VERY light yet VERY strong/stiff and can be bought at most hunting supply stores. Carbon fiber arrow shafts are good also, but many are a heavier wall thickness compared to the aluminum. I have used the aluminum tubes as leading edges of large ailerons made from light weight competition Balsa to gain torsional stiffness in a very light structure.

Depending on how skilled the pilot will be (light balsa construction is not very tolerant of minor oop's), you may want to stick with durable foam as a main building material but reinforce it with arrow shaft type material and reinforced packing tape.

[GO DAWG GO]

Aircraft must fit in a 4 ft x 5 ft square.

Matt,

Beneath it all. lets calculate wing loading first. All other variables will be designed to support this.

From your information the total weight/mass will be X for the airframe and 7 lbs of payload with a max of 4 lbs of batteries. (you will come now where near this weight in (Lipo) Lithium polymer.

Lets say for giggles you have a total gross aircraft weight of 11-12 pounds. mass will rise rapidly when you build a landing gear system to support that weight. Largest wingspan you can have is 5 feet and a cord of ~18 Inches.

Check Renolds and NACA airfoils you WILL need a A symmetrical High aspect ratio airfoil. wing loading is 1.5 lbs per sq ft. (Very high ) with a mono wing

I would no doubt make a bi-plane then you increase weight a smidgen but decrease your wing loading by 50%. (Slower airspeed this will be necessary for the takeoff requirement).

Look for a digital brush less motor and speed controller that will create a minimum of ~7 pounds of static thrust to propel your craft and hit V1 before the mark. My calculations are approximate but very close. The more the better but with the weight issue being most important. This is a good engineering experiment. You will find yourself in stade studies for efficiency. adding motor weight for more power. wing area for lift.

Let me know if you want me to help. I am a aerospace engineer and have won the Boeings Engineering Machine Competition for 3 years in a row and a R/C Flyer.

Foam is very-very strong for its mass..Epoxy will not attack it and a great adhesive ....Go this route.

Bob

[berettafan]

10lbs AUW holy ****! might need more motor than the 3520-7 then.

I suggest starting with the assumption that the plane will use a 5' wingspan and 4' long fuse. Go buy some foam and start playing around.

Carbon fiber gear is available (askman camera mount is what you're searching for).

I feel certain you will be changing props for the various challenges.

I wonder if a bi-plane is worth considering? 5' is just not very wide for that kind of weight.

As Tim mentioned earlier COG is everything so be sure to set it right when testing.

[berettafan]

Bob can you talk about the symmetrical wing and it's relationship to speed vs. a flat bottom wing?