Thinking about my first plane
 

Mon August 18, 2003 03:36 PM



Hi everybody, im bran new to the rc aircraft scene. But i have experience with radio control because i build fighting robots as well. For my first plane i have decided to make a scratch built top winged trainer like plane with a .25 engine, and flat bottom wings

I know building a plane from scratch as a first one is a great undertaking. but i have a few reasons why i chose to do this. #1 its a bit cheaper and i can get parts 1 by 1 instead of all at once so that i dont have to spead loads of money off the batt.

#2 I think its more fullfilling to see something you made completely on your own soar into the air (and crash 5 seconds later )

I have a few questions ive been looking around on the net a bit but i cant seem to find these answers.

1. how large of a plane could i make with a little .25 with say a.... 9x6 prop? I was thinking maybe 45"-55" wingspan?

2. i know how important it is to get the wings just right so i need some basic infor on them like, how thick i should make them, (top of airfoil to the bottom) how wide should they be(leading edge to trailing edge)?

3. im on a tight budget (im 14 and dont ahve a job yet). so i have to use the 1 and only crappy radio i allready have. a 3 channel. with this setup i cant think of a way to control the rudder if i use a knob for throttle, the left stick for elevation and the right for ailerons. i dont beleive a rudder is absolutly necessair except for manuvering on the ground and advanced areobatics.

4. How big should i make my aleirons and elevators for this size of plane?

5. when i build the ribs for the wings, how thick should they be? how close together should they be? and should i leave them solid or cut our there centers to make them lighter?

do you guys think its possible? im trying to do the whole thing for under 250 bux, maybe 300.

Im dreadfully sorry about this long post, thanks for reading. :D

Thinking about my first plane
 

Dude911 ,

If you are on a tight budget save up and get a kit or buy plans that include a parts list. Scratch building and designing your own plane are two seperate things. You can Scratch build from plans the only difference between this and kit building is you make the kit "parts" as you go.

Thinking about my first plane
 

I admire your resolve in making this attempt. My first suggestion is simular to Crashem's, go find some plans. There are lots of plans out there for .25 size trainers that will give you all the dimensional information you need. The AMA has a big plans service, and there are several others. Plans usually cost about $10-20 and usually come with a list of materials and some instructions to help you out.

That said, the truth these days is that the ARF trainer packages you can get are actually cheaper than going your route. True, it's nice to spread out the costs, but by the time you figure it all out, and take in to account the necessary overages you have to buy (like plywood for the firewall, you'll need a small chucnk, maybe 3" square or smaller, but you'll have to buy a 12x6 or so piece), plus things like covering material and hardware, the cost comes out to more than the current ARFS.

Now, if you want to get in to this for not a lot of cash, the best way is with SPADs. Take a look at www.spadtothebone.com SPADs also lend themselves to design experimentation, and you see a lot more people designing their own SPADs comprared to much of the rest of the hobby.

All that said, here are some answers for you:
1) yeah, that's about right. 48" seems to work well for many .25 powered sport and trainer planes. A bit extra for a real floater wouldn't help. Look at the ads for some .25 ARFs for their spans, and measure the pictures to get a wing chord if you want some other opionions.

2) For airfoil stuff, it's a good idea to go download a program like Profili. It has lots of good airfoils for lots of purposes, and can print out patterns for your use. Look for flat bottom, as you said, and something in the 15-20% thick range. That means the thickness is a percentage of the chord (including ailerons)

3) Your radio is on a band that is ok for aircraft, not a "surface" radio, right? Ok, there are lots of 3 channel planes out there. You can go either aileron-elevator or rudder-elevator, either way. If you go aileron-elevator, hook up a servo in the fuse to the nose or tailwheel and use a y-harness to plug it in to the aileron channel. Don't hook up a rudder and aileron servo to the same channel though, it can work, but it's more trouble than it's worth. If you want to go rudder-elevator, just put some extra dihedral in the wing. Rudder-elevator is actually a lot easier to set up and get working right, so I'd be inclined to suggest you go that way. I do fly several different 3 channel aileron-elevator planes myself though.

4) For ailerons, you'll probibly want to go with "strip" ailerons that run the entire length of the trailing edge (TE) of the wing. In that case, a 1" bit of aileron stock will work just fine. For the elevator, you can go anywhere from 1" to 1.5" for a trainer. You can even do more or less if you want, but getting the control throws right is going to be a trick.

Side note: In general, you'll want someone know really knows their stuff to check out and test fly your own design for you. There are a TON of itty bitty details like control throws, CG, incidence/thrust line angles, etc that can really make a huge difference in how the plane flys. An experienced pilot/builder can help you work out the details and hopefully save your plane if something is a bit off.

5" for a .25 powered plane, 3/32" balsa works well for ribs. From memory, (not going and re-measuring my planes at home, since I'm at work right now), about 2.5-3" between ribs is about right. Less spacing is stronger, but heavier. Putting a hole or two in the rib will help with weight, which on a small trainer is important, but I'd probibly leave them solid anyway for strength and being lazy. Or maybe one hole just behind the spar area.

Do I thnk it's possible? Yes. Do I think it's likely you will get a good flying plane off the first time? Nope. Do I think it's a worthwhile, fun, and educational adventure that I'd do if I had the time? Yep, and I've done it (well, i wasn't building a trainer, but still). There is nothing quite like designing and building it yourself. Do that, and you can really snear at all the ARF jockies, and even the snobby kit builders will have to bow down before you ;) :D :p

Thinking about my first plane
 

AAAAAHHHHHHHH damn....

that was stupid of me i never thought of the radio band, im running on 27.255. Im pretty sure thats not legal for air is it?and actually, the sticks only go on one axis, thats y i ran into the problem of not being able to rig the rudder to the same channel as anything else.

crap, well i really cant affored a kit AND another radio so i guess im gunna have to spend the extra cash. and take much longer to build this thing, but im sure it will be worth it. with a kit i think i could do it with a cheap radio at 400 bux if im carefull.

ill think about getting a kit. i think ill save designing my own plane for next time. only problem about a kit, if i break it its harder to repair since i didnt actaully make the parts.

Say if i completely destroy the wings on a kit. would it be any harder to make my own wings like i would of done when i made my own plane? it doesnt seem like it to me as long as i have the plans.

thanks

Thinking about my first plane
 

Be sure you trace all the bits and pieces that aren't shown explicitly on the plans if you want to build another when you're done! I'm pretty sure my LT-25 plan doesn't show what all the pieces look like, since they are all pre-cut for you.

I'm planning to do the same thing except it's because I want to learn fly with the stock wing, but then play around with flaps once I'm starting to get the hang of this flying thing :).

If you get a used engine, then I suspect you can stay under $400 without too much trouble, especially if you already have some of the building supplies. I'm sure all the odds and ends end up costing a bundle, but just looking at the major items... $70 for a kit (my LT-25 was $67 at tower hobbies), $130 for a 4-channel radio with 4 servos, even a new OS 25LA or magnum xl-25 is only about $60 (and shoot, the 40LA looks to be the same price as the 25LA if you are a member of the "more power!! HARHARHAR" camp). That should leave over $200 of your initial $400 for other bits and accessories... I priced out a full set of building materials from tower once (one of each CA, one of each epoxy, the fancy aluminum sanding blocks and a bunch of several grits of sticky-back sandpaper, razor saw, xacto knife etc.) and it was ~$100
That leaves another $100 for flightline supplies.

I think if you're careful, you should be able to come in under $400 easily.

-Rick

Thinking about my first plane
 

Dude!

If you want to be successfull, don't think cheap. You said you want to spend up to like $400? You can get all new equipt for that. If you want to go used, you can get good stuff for like $250 for the plane radio and engine. If you are sincere and want to do it right, I can help you find stuff. If you want to do it cheap and end up getting frustrated and quit, please don't waste my time. I will help if you want to get into it right though. You will enjoy it. I started when I was 12 and mowed a lot of lawns to pay for it. I am 37 now and still enjoy it a lot and fly full scale for a living so it is a great hobby and can lead you awsome places. PM or email me if you want help.

Thinking about my first plane
 

you can build a spad for $20 and then you will have the money for a radio.......$150 and the engine $50 so thats cheaper then what you thoughtand they fly great i was flying my buddys combat planes the other day and they wer great just not good for pattern what i'm used to flying.............oh and you can crash spads and just pop the wing back into shap and fly it again.

Thinking about my first plane
 

Keep in mind; today you can buy a new "Ready To Fly" trainer for $300. Thats' the trainer, engine, and 4 channel radio equipment.

You'll likely need about another $100 for fuel, fuel pump, starter and 12 volt battery, and a glow igniter and a couple extra props.

Then, if you don't mind good used equipment; with help you could probably get it all for $250 to $300.

Find a club and an instructor. You'll need the instructor (or you'll waste all that money), and a club quite often has contacts to people looking to sell their old equipment.

Good Luck and Welcome!
Dennis-

Thinking about my first plane
 

Do what some of the others on this thread advised and look at the Spadtothebone web site. I have built 4 of them and they fly great. You can also look in the classified section of this site and get everything you need to get started. I have bought engines and radios both off of this site and got great deals. I have a Spad DPS that I am interested in selling if you are interested. If so e-mail me at [email protected]. Try a spad they are cheap and easy to build and fly great.

Rick

Thinking about my first plane
 

Now that should be a good deal! If they're only $20 to build you can't be asking more than what, $10 or $11.00? :D
Dennis-

Thinking about my first plane
 

When people say it is only $20 to build they are only talking about the coroplast and gutter pipe cost. You also need all of the other hardware needed to build a plane ( motor mount, landing gear. wheels, fuel tank and all of the other stuff needed.) Once you buy the coro and gutter pipe you have enough to build 2 or 3 planes but you still need the hardware and other stuff. You will spend about 20 to 30 dollars on all of the other hardware depending on what you buy. I use good hardware on my planes. This plane also has an OS 46 FX engine installed on it and an Airtronics vanguard 6 channel radio with 4 servo's a battery pack and switch. I fly it every weekend and it flies very good. I just have too many planes right now and need to make some room for other stuff.

Rick

Thinking about my first plane
 

Look at auction 3142356390 on ebay. Ready to fly, prof built eagle II. It is at about $110 right now. Will sell probably around $250. Anything under that would be a huge steal! Could go to $300 but I don't think it will. Take a look! It is what you want. Comes with radio and engine.