this time it have to be light if it gonna be small. i'll keep posting all my calculation and consideration in this post so others can learn as well.
for the mean time, this is my first try on making a small stick. the wing and tail design actually i borrowed from dougmontgomery (RCG) KFm-5 DLG. an unmotorised glider. i just use a stick design with a motor an combined it togather.
doug design
my mod
the maiden flight went well at first, but it seems like the blm that i used cant handle 2cell. other than that the design is proven. so it looks like i have to design for use with 3cell.
some short video of the maiden flight.
update 3/2/09 :
I’m gonna go with a new design. It’s not satisfying if I’m using totally what dougmontgomery have designed. Although its just wing and tail. I might as well gonna have to go with what I already have in my possession, in term of power systems and building material. I’ll stick to single fuse as what I’ve done above. Because my point is to make it simple. This is some of my target for this build:
1. it gonna be a slow flier as my corostick.
2. max weight gonna be 500g.
3. will only be controlled by ailerons and elevator. Meaning 2 servos needed.
4. wing loading have to be below 10 oz/ftsq for a slow flight and a nice glide with moderate stall.
5. wing aspect ratio between 5-8 for slow roll respond.
6. wing will be build using kfm airfoil - will decide later on which one to use.
7. meant for night flying.
My first consideration - would be what I already have.
1. mini servos 5g.
2. 3 cell bty 1300mAh.
3. esc 30A.
4. 4ch rx.
5. blm 1500kv + 8040 / 1000kv + 1047.
My 5g servos would be great for my ailerons n elevator. Its light as well. I’m deciding on using one servo for aileron as it suit my 4ch rx.
With 1500kv blm + 8040 I’ll get about 600-700g of thrust n I think that enough to handle my stick n bail out from any emergencies with enough power.
As for the fuse, I guess you guys have noticed it that I’m using a hbk2 tail boom on my mod doug dlg. I’ve a bunch of it from my crashes on learning how to fly rc helicopter. So it will be the fuse for this stick as well. Carbon rod boom or arrow shaft can be an alternative as well. As I said, im using what I already have.
Soon I’ll be getting on the wing design considerations. So stay tune. I hope my writings inspiring you guys in building your own. Rc Aircraft is not all about flying it, trust me you’ll enjoy the build n flying it. As I’m, I’m proud of my corostick till today. Although its not an exact science in plane design, but all the basics is still there. And it flies.
update : 3/3/09
The wing.
The wing of my stick will determine some of my stick flight characteristics. Such as how slow I can go without stalling. How sensitive it will be to roll control. How well it going to glide. Is it going to have self correcting ability for roll axis and so on.
First let’s take a look at what I want my stick to be able to do.
1. I would want it to be able to fly well in a slow speed. Low wing loading going to help.
2. Moderate glide ratio. With low wing loading n kfm airfoil I hope I can work some thing here.
3. moderate roll response. I think wing aspect ratio of 5-7 would be just nice.
4. some self correction on roll axis for easy control. Thinking putting some dihedral on the wing. Might not be much as it will have ailerons.
update 3/4/09:
Wing Loading - I’ll put my wing loading as 10oz/ftsq for a moderate glide and stall characteristics. As from what I found from some research that I’ve done, for a glider like plane I’m going to need a wing loading not more than 10. from here combine with the wing aspect ratio, I can determine the wing span and chord.
Wing Aspect Ratio - For a moderate roll response I’m going with 5:1 (span:chord) trainer style, as I would like to be able to have some quick response to get out from any trouble at low altitude. There will be some lift to drag ratio factor involve, but i don’t think it going to make any different for a simple build plane.
Dihedral - I’m going to go with 3 deg of dihedral for some self correcting in roll and pleasant flight.
update 3/5/09:
Wing calculation
After making some simple calculation using all the basic that I’ve gathered while building my corostick. This is some of the numbers that I’ve got so far for my simple stick wing.
Estimated AUW = 500g (17.64oz)
Wing Loading = 10 oz/ftsq
Wing Aspect Ratio = 5
Dihedral = 3 deg
The numbers gonna give me
Wing Span = 35.64“
Wing Chord = 7.13“
Dihedral = 0.97“
To make it simple I’m gonna with this number
Wing span = 36”
Wing Chord = 7”
Dihedral = 1”
Wingloading = 10.08 oz/ftsq
Still right on target.
For airfoil I decided to give KFm 3 a try. Some extra lift might help.
1st step = 3.5” chord
2nd step = 5.25" chord
As im going for Depron as building material, its gonna be a three layer wing and some sanding needed. Got a good reference on how to do it from internet. Lets see if KFm airfoil is worth the effort as it said.
Gonna go with the wing build next.
Note .:: nih syok sendiri-sendiri ja nih, just ikut takat ilmu yg ader. Itu pun dok research kat internet. Kalu ader kwn2 yang nak menokok tambah dipersilakan. Ble gak kwn sedut sdikit sebanyak ilmu kwn2. ::.
Translated- I would appreciate if you guys would be kind enough to drop some comments so that I can learn more. So far, what I’m doing is just base on what I learn from my research in the internet.
update 3/6/09:
on second though. i'll finish the calculation.
Fuse n cog
Estimated wing CoG location = 30% of wing chord = 2 1/8” -> carbon spar position.
The simple rule of thumb for model airplane fuse is;
The nose gonna be (1-1.5 x of the wing chord) from the leading edge of the wing.
The tail gonna be (2-2.4 x of wing chord) from the trailing edge of the wing.
so my stick fuse have to be somewhere between 28” to 34”. I think I’ll go for 1 x nose and 2 x tail .
As for the fuse I’m using 2 HBK2 tail boom joint together, it measures only 25”. So it looks like I’ve to make some extension to make it at least 3” longer.
then to balance my fuse n wing on CoG, there’s a simple rule of thumb as well;
the wing CoG should be 30% from fuse nose.
That giving me about 8 3/8” from the nose to place the wing on the fuse at CoG mark. Then I could work to balance my stick at that point.
update : 3/7/09
Stabilizer, Fin n Control Surfaces
Parts that’s going to make my stick flies batter. Needs the tail horizontal and vertical stabilizer for pitch and yaw stabilization.
Again comes the simple rule of thumb:
stabilizer (horizontal) - surface area 20%-22% of wing area. I’ll make it 22%. With aspect ratio of span to chord 3:1.
elevator - 20% from stabilizer area.
fin (vertical) - 1/3 of stabilizer surface.
ailerons – im going with strip ailerons, easier to use one servo. It will be 1/8 of wing chord.
From that I get this numbers after rounding:
Stabilizer = 5” chord x 13” span
Elevator = 1” of stabilizer chord
Fin = 5” x 5” (will cut later for some looks, then the area will be as calculated)
Ailerons = 1” of wing chord
update 3/10/09:
Here's how my simple stick would look like. Typical simple stick huh ?!
Notice the wing mount? that for placing most of my electronics n battery.
update : 3/12/09
Wing Construction
I've start building my simple stick. Here's the wing construction. again, i change my mind. instead, i go with 0deg dihedral on the wing. it's hard to build dihedral with carbon tube. so i decided i'll go straight.
update 2/13/09:
i'm still thinking wether to stay with elevator ailerons or put on rudder as well. would have batter control with rudder. at the same time i'm thinking about how i'm gonna fix my aileron servo into the wing. that might slow me down.
here's some more work that i've done.
update : 3/16/09
As usual, i've change my mind again. i'm going with rudder as well. So my simple stick becomes a 4ch airplane. Here's some more of the contruction details. There's some pictures missing of the steps, as i'm keep forgetting while building it.
boom made of honey bee king 2 tail boom. joint togather using pencil :). Add 3" extension to get 28" fuse.
I've maiden it on last saturday. The flight went well. Interm of i've a chance to discover that, its not for beginer. Maybe if i stick with the original plan to have dihedral on the wing, it may be more forgiving for beginer.
found that :
- need lots of DR/Expo for aileron n elevator.
- the KFm 4 works perfect. perfect lift.
- power system seems to be to fast for a stick.
- got to redo the tail section. as i've scaled down the stabilizer and it doesnt seems proportional to the wing. instead of 13" span, i'm using a 10" stabilizer. and an inch extension to the rudder might give me more control on the ground.
- CoG is aft by 1/4 in from calculated.
- boom joint got to redo for strength. as this is what happen later that day. the pencil inside the joint snap.
here's the maiden flight video. judge it yourself.
btw : i'm proudly to inform :) that yesterday, i've got comments posted on my corozagiV2 youtube video and my blog post on the same subject, from the originator or KFm airfoil. Mr Dick Kline himself. Who's 40 years ago throwing paper airplane from his 10 storey (if i remember it right) office window down to the street as a hobby just to see how far it would go and keep finding the best way to fold his paper airplane for maximum flight.
for those who interested on this checkout this link for more information on KFm adaptation to rc airplane. This is where it all started in rc using KF airfoil.
update 3/17/09:
this some more build information that i miss before.
i forgot to mention about fuse and electronics placement. it is best to prefix all your component without the battery to the fuse so that you get the plane CoG at place. From that you can then fix the battery tray under the CoG. by that it easier to move the CoG fore and aft just by moving your battery.
with a shorter fuse length, i would say my simplestick gonna be a bit sensitive on the pitch. and as the size shows, maybe the control is the same as nemo :) thats why im putting gyros on my simplestick. not so simple huh? :) just for the sake of to feel n learn how it works in a plane.
actually i mange to test it on the 'Sambutan Hari Wilayah At DKNE'.
here's short flight report of its 2nd flight at DKNE:
i start pluging my battery without adjusting both the gyro gain. which is set to center. as i take off the plane started to have a tail wag ups and down. and from what i've learned from dave powers videos, its because im having to much gain on pitch gyro.
bring her down and switch the pitch gyro off following the advice of fellow rcers at that time. then take off with only roll gyro. this time the roll is making the same thing. came down, dialed down the roll gain. and got it dialed perfect. it stablise itself.
bring her down again, and start dailing the pitch gyro. at that time it came to my mind, gyro will initialise on startup and will read it startup position. if that so, what happen before, i let her on its take off position when i plugin the battery. which is not parallel to the pitch neutral axis. so once i take off the ground, i tend to make it fly and the gyro is trying to put the plane on its neutral position which is the take off position (tail down). resulting in the plane wagging up n down. so this time, i plug the battery with her leveled to the table/ground. after the gyros initialise and only i put her ready for take off.
and it flies with gyros. not a perfect flight, but it proves what dave is doing. still need some tweaking with the dr/expo/gyro settings for a perfect level flight. cant wait for another fligth to dialed her in.
update 3/23/09:
finally, she's dialed nicely with two gyros. one for aileron n one for elevator. the only thing is, i still cant get the CoG to be right. as for my shorter boom version, it seems that this plane tends to be nose heavy. tried to put a weight at the tail, and it end up the CoG moved to the center of the wing chord. but still it quite nose heavy.
i found that it is nose heavy as it dive when i try to do the glide test. meaning throttle is cutted.
got to figure out later. maybe somethings wrong with the wing placement.
here a short video of my SimpleStick with gyros.
updated 4/23/09:
as i said before, all of my stick airplane is inspired by BMNF NiteStick with originated by Mr Ahmad (Che Mat/Masam). From the first time i lay my eyes on that plane, i said to my self, i got to build myself one of those for night flying, but with my own design n calculation. and now after more than one year, i've done it. not as perfect as NiteStick, but it can fly as high as NiteStick.
this is my new SimpleStick for night flying. im using the original calculation from this post and with the same building method and added 7" span on each side of the wing with 1.5" dihedral. so i can use rudder only to turn.
BLM : 1000kv + 1047
bty : 1300mah 20C
max auw : 500g
updated 4/29/09:
My SimpleStick become a sport plane.
updated 5/13/09:
Modified from my previous SimpleStick because i wanted something slow for night flying at BMNF. Using the same flat wing measument (38") i added 7" on each tip with 2" dihedral making it 42" span. so called tip dihedral wing help me control the plane just by using elevator n rudder.
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