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newbie to the hobby needs help building his first sratchbuild and could use some tips

#1
hello everyone, my name is samaki, and i'm a 16 year old from clarksville, TN. I am new to the hobby, and want to get into scratch building and flying RC, and i had a project that i wanted to start on, and was wondering if i could get some help/ tips.
i'm going to try and make an A-10 Thunderbolt II, but the way i wan to make it is out of foam, but i want it to have certain characteristics while flying. I want it to be very controllable at as slow speeds as possible, (which i want it to be able to fly at), have stability, but i also don't want to spend that much, and would like to keep it as cheap as possible. Also, i want it to have some nice aesthetics on the way it looks, Too. Can i get some help with this build?


Also, i didn't know which thread to post this in so sorry if its the wrong one >///<
 

earthsciteach

Moderator
Moderator
#2
Welcome to the forum, stormchaser!

What you want to do is very, um, doable. And, you will get plenty of tips from folks on this forum. The A-10 reminds me of a big, angry crop duster, and its wing configuration lends it to some docile flight characteristics. I recommend building something a bit simpler (and quick) for your first plane, though. You can actually be building the A-10 while you learn to fly something requiring less time investment. Or, buy a beginner airplane for around $100 and learn to fly on it. Here are a couple of cheap, quick build options to get you off the ground and bare the brunt of your learning:
http://flitetest.com/articles/FT_Old_Fogey_Scratch_Build
Then, maybe move up to this:
http://flitetest.com/articles/FT_Bloody_Wonder_Scratch_Build

Now, to the A-10. What size are you thinking? I normally start with choosing a wingspan and scale the rest of the plane around that. A 1 meter (39ish") span should make for a manageable, nice sized Warthog, in my opinion. Much smaller than that and it may be twitchy. Much larger and it simply takes more materials, power and time. What were your thoughts?
 

CrashRecovery

I'm a care bear...Really?
Mentor
#5
Welcome to the forum!!!!!!!!! Leave it to monkey to find plans.... This gives me an idea for another scratch build. I can see I nice melding of EA and flitetest building..... Only don't know how I would want to power it..... Edf or pusher
 
#6
Welcome to the forum, stormchaser!

What you want to do is very, um, doable. And, you will get plenty of tips from folks on this forum. The A-10 reminds me of a big, angry crop duster, and its wing configuration lends it to some docile flight characteristics. I recommend building something a bit simpler (and quick) for your first plane, though. You can actually be building the A-10 while you learn to fly something requiring less time investment. Or, buy a beginner airplane for around $100 and learn to fly on it. Here are a couple of cheap, quick build options to get you off the ground and bare the brunt of your learning:
http://flitetest.com/articles/FT_Old_Fogey_Scratch_Build
Then, maybe move up to this:
http://flitetest.com/articles/FT_Bloody_Wonder_Scratch_Build

Now, to the A-10. What size are you thinking? I normally start with choosing a wingspan and scale the rest of the plane around that. A 1 meter (39ish") span should make for a manageable, nice sized Warthog, in my opinion. Much smaller than that and it may be twitchy. Much larger and it simply takes more materials, power and time. What were your thoughts?

well, i was thinking about a good sized wing, and then i was gonna build the rest of it to scale around that, but in terms of size, I dont really know how big i want it, i dont want it to be small, so 1 meter sounds good for a proyotype, but the thing i'm worrying about it is power and the servos. i was thinking twin EDF's , to fit with the style, and will 9g servos work? also, a battery that will power it and not die on me. also, does anyone know where i can get some foam or what kind to get? i looked around today, but couldn't find anything but Styrofoam, and i dont think that will work that well.
 

earthsciteach

Moderator
Moderator
#8
Foam board is good and will work well for the wings. For the fuselage, you may want to use foam insulation board, the kind you can buy at Home Depot or Lowes. You can laminate it together into a block and carve the fuselage from that.
 
#9
How would i laminate them together? because i was thinking that, it would let me shape it perfectly. Also, got the wings built :D
I'll post pics soon, but the scale might be a bit off, the wings turned out bigger than i though, but that's not that bad, now, one thing i need to do, what about power? i dont know what to use to power it, i was thinking twin 64mm EDF, but would it be enough? i dont know its it will be enough, or to little.
 

earthsciteach

Moderator
Moderator
#10
I have had success using this product to glue them together:
http://www.loctiteproducts.com/p/a_...octite-Spray-Adhesive-General-Performance.htm
While it says it is foam safe, don't put it on too heavily or it can melt the foam a bit. Just make sure you are holding the can at the recommended distance from the foam (I spray it from about 12" away). I think I bought it at Lowes.

Twin 64mm edfs should do just fine, but that really depends on the end weight.

Do you have any experience with hot wire foam cutters? If not, do a bit of Googling and you tubing. Its a foam cutter's best friend! You can make one yourself really inexpensively. Check out this build log that is ongoing at the moment. This guy is GOOD!
http://forum.flitetest.com/showthread.php?4611-quot-Scale-quot-Gee-Bee-R3-Scratch-build

Looks like he is hand carving and sanding everything. It will probably give you some helpful ideas.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#14
Storm,

the battery side is easy. get/make a Y connection between the batt and ESCs.

the signal side, you have options:


simple: connect a Y between the ESCs and rx, but break the power lead (center lead) between one of the ESCs and rx (rx and servos powered by the other ESC).

plus: dirt simple and can be done with parts from LHS or stuff lying around, works with "dumb" transmitters
minus: motors are ganged together (no differential thrust), limited number of servo power available (more on this later)​


moderate: if you've got a spare channel on your Rx, you can remove the Y, plug one into the throttle. the other ESC can be plugged into the other channel *except* it's power line must be cut. Don't mangle your ESC wires to do this. get a short extension and remove the power lead. Also if you try this with a non-programmable transmitter, it probably can't be done w/o some custom electronics on the plane.

plus: Still simple on wiring, Motors can be programmed with differential control (turn left and the right motor speeds up to pull you through the turn).
minus: must have a programmable radio and complicated programming. still limited on servo power.​


hard: build a power distribution board. can be done with perf board and headers. basically, the board plugs between your ESCs , servos and Rx. in effect:
  • everyone shares the ground
  • everyone receives their signal from the rx
  • rx receives power from one ESC and the servos receive power from the other ESC
By far the most complicated setup, but gets the most out of what you have. The reason you'd do this is each ESC can only support so many servos at one time. the higher your cells, the fewer servos it can support. This allows you to spread the available rx/servo power between both ESCs, doubling what you can support.

plus: more current available to spread between rx/servos/lights/... Can work for either ganged or differential motor setups.
minus: *complicated* - extra board/wires, extra weight (not much, but every gram/oz counts!).​

if you're interested in the third setup, Hotwax put together a article describing the layout and board:

http://flitetest.com/articles/utilising-both-becs-in-the-ft-cruiser

Check it out and feel free to ask questions.
 
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Craftydan

Hostage Taker of Quads
Moderator
Mentor
#16
Sorry Storm. Didn't answer that question, because I don't know. It's also *not* an easy question to answer, and may not be answerable with just the info you have.

The motor/EDF you picked is strongly lacking in specs. While they give a torque and speed at 4.8v, that's the very top of 1S battery(probably not what you'll use), and doesn't tell anything about what current it will draw at 4.8, nor what the max current/voltages it will tolerate.

To then size the motor to the battery (ignoring mAh capacity for now) you need to know
  • rough final weight of the airplane
  • maximum thrust for a for each suggested cell rating (you don't have and usualy won't)
  • maximum current draw at each suggested cell rating (you don't have almost always will)
most people cheat on the second one by multiplying the voltage by the maximum current to get watts, then using the rule of thumb W/lb of aircraft. Depending on the style of flying you want this RoT number changes, but 100W/lb should give you a fair balance of flying, and set your target for maximum weight.

Subtract out the weights for the things you know (motor, rx, servos) and you have the remainder left for the things you don't (airframe, battery). if you've got an idea for your airframe weight, you should know how much weight you have left for your battery for 100W/lb.

On the duration side, this is a difficult balance of adding more weight vs. adding more capacity. more weight means higher throttle setting, and shorter flights. more capacity means you can run the throttle longer at a given setting. this is coupled together by motor efficiency, which is something that is never speced. if your motor is still running efficiently, flight time can increase with added capacity/weight. if it's not, added capacity and weight will actually reduce your flight time.

To calculate *minimum* duration, take your selected battery capacity, then divide the maximum current draw. you should get decimal hours -- will probably land in the 3-10 min range. less is a bad fit, more is hard to do. keep in mind this is a full throttle, the whole flight -- we put wings on these planes so they don't have to run full throttle.





Looks like a nasty mess of things to calculate, doesn't it? It's why most people follow other's plans for sizing things, and either tweaking in ways they understand or trying things out with parts on hand. Don't let this discourage you, but you might want to take an easier step for your first scratch build.






*My recommendation to you* either:

  • if you haven't bought this EDF *and* you can't find the specs for it, find another one. you won't know if you can use it until you've bought and tested it -- rarely a good deal. Contact LT -- they may be able to scrounge up the specs. If so, then run the numbers above. Otherwise, start looking at other EDF setups where the info is available

or

  • Look at plans others have published and see their recommended setups. Most will publish some sizing info and suggest the battery that worked for them. By all means pick a plan you like, but choose one with plenty of info to build on.
 
#17
For laminating foam, I use 3M Super77 spray adhesive. Elmer's Spray adhesive can also be used. Both are foam safe, but Super77 is the best.

I'll second earthsciteach's comments. Start with the Old Fogey and use it to learn on. I've had excellent results using the Old Fogey to teach with.

I started on a similar path to you. I wanted to start with a F4U Corsair. After totalling the model, I nearly gave up on the hobby. Fortunately a friend told me, "Get a trainer, try again."

So... start with a trainer. You can still build the A10, but at least with a trainer you're starting off with a plane that is more likely to grow your interest in the hobby--not stamp it out.

Cheers!
Randall
 

willsonman

Builder Extraordinare
Mentor
#18
This is a great first project! It can teach you many different aspects of building all at once. I'm not big on EDF units as they tend to be fairly inefficient and need larger batteries due to that. You may want to consider twin pusher motors. COnsider the setup on J Morgans ME262 as an idea. For the complex shapes such as airfoiled wings and the engine cowls a hot wire setup will make your life so much simpler. Please see my video for some instruction:
Hot wire airfoil templates
And see my latest build to get some ideas how you can make the cowls:
http://forum.flitetest.com/showthre...Build-Inspired-by-David-For-teaching-everyone
There are so many things to learn that I suggest just digging in where you can. As you go, post here and many others will chime in and lend a hand with suggestions and links.

For your basic aerodynamic design I would suggest you start by deciding on wing design/construction. KFm wings can be very strong and efficient but not very scale. If considering an airfoil I would try and sway you toward a flat-bottomed airfoil since its less complex to cut and gives excellent lift if you get heavy handed and do not build as light as you would think. Try and keep your tail planes as flat stabs. Do not try to airfoil them too much as the flight characteristics may be more to handle than what a beginner may want to deal with and you may have a discouraging crash. For CG calculation I recommend this simple site. On the same site this page will give some great tips to make a successful scratch build.

A trainer WILL give you the eye-hand coordination you will need to pilot a plane. As a little motivation... check out the A-10 I saw recently.
 

Ron B

Posted a thousand or more times
#19
I agree with those who are suggesting you start with a simple trainer to begin with and work on your A10 while you are learning to fly. You will crash a lot and learn how to repair your planes before you start flying your dream plane. I am just getting started after an absence of 42 yrs. but still remember how it was having to learn back then and am having to learn all over again. I am starting out with the old fogey this time and have learned a lot in just building from plans. I would suggest to a first time flyer to get a good rtf or to get a flitetest quick build kit for your first plane but still do one of the planes that is a trainer.
 
#20
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