lets build a BIG ap/av plane. - RC Groups
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Sep 05, 2007, 05:17 PM
Back in black............
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lets build a BIG ap/av plane.

ok I have been out for a while. but I am back now. funds are tight around my house right now. I am getting married 9-29-07. my soon to be in-laws said they would help with the funds for that then backed out 6 weeks to go. yipe. I find my self with out a ap plane big hole that needs to be filed. I dont have a lot of rc stuff right now " will fix that asap" I got to digging around last night to see what I have. I have this set of wing that I built for a
scratch foamy that I was working on. fuss is gone. I have a bp3520-7 and a 14x8.5 zinger prop and 3s7800 tp lipo. if I figured it wright I am looking at about 60oz of thrust and 35mph out of this power setup. so this is where you guys come in. what to build. I guess you need to know what the wings are

wing 17.7oz that's one side at 48x19.5 that is a 1872 wing area
boy I dont remember building that big oh well. that gives me 36oz for the wings. this thing is a ap plane so as long as it come in under say 80oz climb should be good. wings a symmetrical and no dihedral has to have at lest one aileron.

this is where you guys come in.

pusher or tractor?
fuss or stick?
single tail twin tail?
if twin A tail, Ttail, Vtail, duel rudder tail, what ever I cant think of.
the wings split in the middle so how about the fuss does it come apart in the middle also. does just the tail come off.

there will be 4 goals to the build.

1 must keep it cheap "hahaha hahaha haha""ok stop laughing now"
2 keep it as light as can be. {this is where I always get into trouble}
3 needs to be easy to transport even though it is really big.
4 would be nice if it flys.

that it from me please let those idea rip

Oh and here is the tread for the plane that i was building that the wings come from. https://www.rcgroups.com/forums/showthread.php?t=625178

OK yalls turn now
Last edited by cars4fun2001; Sep 05, 2007 at 05:23 PM.
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Sep 05, 2007, 05:38 PM
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quailbird's Avatar
https://www.rcgroups.com/forums/showthread.php?t=733640 Take a look at this! I'm making one very similar but I'm using an aluminum tube I found left over from an old volly ball net.
Sep 05, 2007, 05:51 PM
Back in black............
quailbird I was reading that the other day. still cant believe that the tap held the wing together. that would never work for me. are you using the aluminum tube for the fuse?


I have already decided my winter project is a Hot Wire table.
Sep 05, 2007, 07:03 PM
Registered User
quailbird's Avatar
Yes on the fuselage, only my wing doesn't fold. I love the way that planes floats through the air. Perfect for AP.
Sep 05, 2007, 10:33 PM
Back in black............

well lets see what we have here

ok guess its going to be a twin boom plane. any one know how to figure out how far back the tail needs to be? I don't have a clue. as it sets it wieghs in a 52oz
wing span is 98" with the center I have everything for a tricycle landing gear. as it sets the back of the booms is 29.5" from the TE of the wing. I am thinking twin ruder and elevator between the booms. sound good? well thats all for now

any input welcome.

Sep 06, 2007, 12:11 AM
Suspended Account
Ok, you're getting off target.

"1 must keep it cheap "hahaha hahaha haha""ok stop laughing now"
2 keep it as light as can be. {this is where I always get into trouble}
3 needs to be easy to transport even though it is really big.
4 would be nice if it flys."

The twin booms will add complexity and transport difficulty due to breakdown and assembly considerations. You'll also probly need to add ballast to the nose.

Rip those booms out, make a large maggie-like or eyespy fuselage for that wing. No carbon booms, do it entirely out of foam.
Sep 06, 2007, 12:30 AM
Pull out early!
DiveBombDave's Avatar

How far apart are your booms, and what's their ID and OD?

Why not make a standard elevator and twin fin/rudder setup, with CF extending forward that would insert into the ends of the booms? This way you can get the tailfeathers a little further back. You could do the same thing with an A tail - and it may be easier to fold and open to lock at about 110degrees.

There is a golden ratio in sailplanes that the tail moment (distance from center of wing chord to center of stab chord) is one-half the wingspan. With the booms being 29.5" long from the TE, you add (say) a 7" deep stab and 3" deep elevator where they are inserted into the boom ends (and pinned). The center of that surface is 34.5" from the TE, and 44.5" from the center of the wing chord. So 98" span divided by 44.5" tail moment is just a little over that 2:1 ratio, so that's what I'd do.

I asked about the boom spacing because I'd figure the horz stab area I need. I'd guess (open target here fellas) around 280-300sqin.

If you want to do an A tail, I'll measure my AP3 since your plane would match it in about 135-140% scale... I could measure my A tail and elevators and give you the measurements that scale them up to suit, if you would like.

With 13 square feet of wing area, loaded the same as my AP3 (which is very light loading) would be near 10lbs. That motor on 5s would swing it for sure. All up at 8lbs and it'd be as lofty as a kite!

Sep 06, 2007, 12:36 AM
Back in black............
Originally Posted by skymind
Ok, you're getting off target.
story of my life.

I think I can make it brake down with only 6 nylon bolts. 2 1/4" and 4 1/8". one servo for the rudders on one wing and a link between them, a hs85mg on the elevator and one servo on the other wing for a single aileron. the best way I could think to do it so it would brake down was a t tail with duel rudders don't know what the is really called. the battery pack will set in the nose so there is a lot of ballast there. if it works right the booms will come out of the wings the elevator will come off and the wings will split apart leaving the pod as a separate piece. camera will be right on the nose so it will be the first thing to the sean of the crash. sound like it will work?

I can always build a maggie-like or eyespy fuselage for the wings to bolt on to and just leave the booms out. I was just looking around at what all I had and this is what jumped out at me so to speak.

thanks and please keep it coming.

Sep 06, 2007, 12:41 AM
Back in black............
Dave give me a sec I was typing at the same time as you.
Sep 06, 2007, 12:58 AM
Back in black............
ok I had to read that a couple of times.
I think I followed it pretty good.

the booms are 24" apart. they are slid into the wing tell they but up against the main spare that is just about center of the wing just a tad forward. the idea was to put a tube glued into the wing for them to slide into it would be easy enough to set the tail moment that way but I don't know if i could get 7" with out making it weak. humm now you got me thinking again.


ps the booms are tapered with the wider part in the wing. i cant get the id and od untell tomorrow my shop is next to the bed room and Amanda is in bed
Last edited by cars4fun2001; Sep 06, 2007 at 01:04 AM.
Sep 06, 2007, 01:44 AM
Pull out early!
DiveBombDave's Avatar
If you had another set of booms, you could cut a couple of 14-16" sections that could be slid over the outside of the tailbooms about 5-7". Then you could use the back 9" for the base of the A tail surface. I drew this up for ya, just shooting numbers. I just finished my Sr Telemaster glow 1.20 skydiver drop plane tonight, finished the drop rigging and ready to test drop tomorrow afternoon, wind permitting.

If you hinge the top of the A tail it'll fold flat, and then a certain length tube can be bolted in for the horizontal part of the "A," and will lock in that angle.

Sep 06, 2007, 02:04 AM
Back in black............
I like that plus a Atail would be lighter on the back end. how about servos would hs 85 be strong enough for it? I would rather make the booms connect closer up to the wing. there not glued in there yet just stuck so it would be easy enough to do it that way. the tubes that will be glued into the wing can just stick out a little more and it would still be easy to brake down.

I have never had a Atail how do the fly? I have noticed that most of them hove some dihedral on the main wing and this one has none. will this effect the use of the Atail any. what about the single aileron good idea or bad. I have had planes in the past with just one and the seam to work fine. would need to be pretty big but that shouldn't be hard. the wing is very slim so it should cut through the air like a hot knife through butter.

the drawing help allot I have always been a visual person.
Sep 06, 2007, 02:25 AM
Pull out early!
DiveBombDave's Avatar
Once an A tail is mixed right in the radio, it flies just like a normal tail. I'd go with two ailerons - you ain't hurting on weight at all, and the single aileron thing can cause weird tip stalls (two crowds on the single aileron debate).

In programming the radio for the A tail - first is to make sure they both go up/down with elevator, and then they both swing to the same side with rudder commands. You can then make their travel a little more sensitive in elevator than rudder (like a 60/40 split) and that helps sometimes. But with ailerons, you won't really use the rudder stick much. If the plane has a weird tendency when you use aileron alone to roll/steer, you can mix some rudder to the aileron and make it fly better, without having to coordinate both sticks in turns.

If you could mount boom "stubs" into the wing, up to the spar, that you could slide the booms you have now over top of, then that might buy you enough tail moment that you could mount the surface at the back 9" of the booms. But as-is (running from the spar to the back of the surfaces), those booms are sized more for a 72"-80" span, I'm fearing.

Two HS225MG's would be small, light, and powerful (especially on 6v). 85's would be about all they could do (no nose dive stuff).

Single boomers are easier, if you made a deep Eye-Spy type fuse and boom (or like skymind said, a big foam magpie type fuse). But I love a twin boomer!

Gotta hit they hay, long day tomorrow.

Last edited by DiveBombDave; Sep 06, 2007 at 02:31 AM.
Sep 06, 2007, 06:37 PM
Registered User
txflyboys2's Avatar

I can see the "A-tail" and twin boom ideas have got your interest like they did mine! Between Dave and CactusJackSlade's successes, the temptation got the best of me. Our A tail bird (SS Depron Dragon) flies like a dream. As Dave said, it is just a matter of getting it dialed in right on your Tx. And I also agree with Dave on the servo to each aileron setup. With that much span, you will be glad you did. If you have metal geared servos, all the better. Let me know if you have any questions. Will be glad to help out...........I think you are onto something here!

Sep 06, 2007, 07:01 PM
Back in black............
yea I gotta admit I really like Dave avatar. great in flight shot. what kinda motor angle do you need. the only pusher I have ever had didn't last very long "pot hole and hot landing on a maiden flight" and had major thrust angle issues. motor should be pointing up and right when viewed from the back correct?

gona head home now stop and pick up a few things.


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