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Hopping on the bush plane bandwagon

EraJomppa

RC Enthusiast
#1
I got myself a rare free weekend and even though I have couple of other RC projects in progress, I decided to make myself a bush-type plane from some spare parts I had laying around.

Here is the result:

2014-03-22 15.33.21.jpg
2014-03-22 15.33.27.jpg
2014-03-22 15.33.33.jpg
2014-03-22 15.33.40.jpg

Specs for those that are interested:
Weight: 300 grams
span: 900 mm
length: 700 mm (front of the prop to tail)
Rudder, elevator, ailerons and flaps. Flaps are bot behind one servo. Ailerons are separate channels so I can try to add differential or airbrakes (flaps + spoilerons).

Powersetup:
1100kv 25 gram outrunner (old motor, forgot brand...)
3s 500mAh LiPo
5x 9 gram servos (various brands)
10" prop
(cut down 11" prop, Im going to buy 9" and 10" props to try which is the best)
FrSky 7ch Rx

I need to glue some 3mm depron to the top of the frame so it wont be see-through, also I still need to buy BIGGER tires! these are way too little for a "bush" plane ;)

I did fly a maiden, but its was way too windy to say anything about the characteristics really. It flies, can maneuver in the air and flies quite slow. I just kinda eyeballed the CG and it turned out pretty well, I'm waiting for a calm weather to properly adjust it.

The landing gear got torn off on the last landing on the maiden, and I ran out of hot glue so I cant put it back on :( Well I would not be able to fly it anyway with the wind so I guess it doesn't matter.
 

Freaky_1

old headcase
#3
Nice!

Hope to have the next revision of my own in the blue sometime this week..... pending USPS and weather... and undoubtedly the one thing I forgot I'd need.

Here's hoping you have fair weather soon.
Frank
 

EraJomppa

RC Enthusiast
#4
Good looking foam!

What did you use for your landing gear, is it a custom or a spare part?
Thanks, it's custom. I bought some 0,5 mm aluminium and cut my own. It's really just a test to see what I can do with 0,5 mm aluminium and how much beating it can take. I can tell you it doesn't take much to bend it and I had to put some metal wire to help it keep it's shape. Also I need to get myself a proper cutters for this stuff... I might have destroyed a pair of scissors cutting this :D

I'v never really made any kind of landing gear and this is my debut on that department.

Oh btw, forgot to mention. it's made out of 6 mm depron. I'm gonna put some 3 mm to cover some of the holes in the structure.
 

EraJomppa

RC Enthusiast
#5
I think Ill buy some 1 mm aluminium next time. I just felt it might be too heavy for a plane this size, but I guess the 0.5 mm is too thin (by itself).
 

EraJomppa

RC Enthusiast
#7
Second time out with this plane. Still not the perfect weather but I found out couple of things:
-CG too far back, I had to put velcro to the vertical fuselage piece and attach the battery there to make it better, might need a bit more forward CG still.
-0,5 mm aluminium is way too thin.. :p The landing gear practically bends from torque of the motor when taxing. Ill soon buy some 1 mm aluminium but I might end up making the landing gear from pianowire, since I have that readily available.
-Wings are too flimsy. Just the balsa on the leading edge and hinge line isn't adequate. I'm adding 1,5 mm CF rods between the aileron servos and the ply piece I mount the landing gear. I was planning on adding those anyway for the looks, but it's now apparent that the plane really need them for support.
 

EraJomppa

RC Enthusiast
#8
Also a visual upgrade:

2014-03-23 18.54.17.jpg

I ended up using 2 mm balsa, since I ran out of 3 mm depron. I had some black depron-like-stuff (its awful stuff structurally, but this is just visual stuff) and used that to get a windscreen look. I think it looks really nice :cool:

I'm hoping to get my better half with me next time so I can get some video footage. I know it's boring to read about a plane and how wonderful it flies without actually SEEING it ;)
 

EraJomppa

RC Enthusiast
#9
It was a perfect day to fly! I went to school, and straight to the local hobbyshop to buy part for this plane, then back home to do the mods, and when I finally got ready to fly it was darn near dark! Grrr...
Well I did get few minutes flight until I wasn't able to see the orientation. Learned a couple of new things though. Can't wait to fly it in good conditions, during the daylight hours ;) so I could finally tune this baby in.

New mods include:
2014-03-24 21.05.48.jpg
-New more stand up look!

2014-03-24 21.05.58.jpg
-Switched the motor to tiny bit bigger and higher kv one. I would have preferred the old one, but I found out that it needs a new bearings... lost a prop finding that out.
-Put some 3 mm black depron stuff to cover the ESC hole, it created probably 50% of the total drag of the plane ;) It's held down with some masking tape, since its not really a final version yet.

2014-03-24 21.06.04.jpg
-Ditched the 0,5 mm aluminium landing gear and made one from 2 mm piano wire, works like a charm.
-New bigger 55 mm tires!
-Wing struts made out of 1,5 mm carbon fiber. Really stiffened up the wing, no problems from wing flex anymore.

2014-03-24 21.06.16.jpg
-Steerable tail wheel! I glued it on with hot glue and put some tape on to hold it down properly. I'm gonna probably take the tape off when I'm sure it will hold my less-than-perfect landings.

Also some minor issues that I fixed include redoing the tail pushrods, reducing rudder movement mechanically and some hot glue treatment to the wounds.

Lot's of hot glue, lot's of zip ties and lot's of love. The perfect formula!

I still need to tinker with the CG. I found that my CG was this time way to forward. It was very very near impossible to land, since when you cut the throttle, the nose dipped. And when you applied throttle the plane went too fast for a smooth landing on a muddy yard with poor visibility. I realized that most of the rocking and twitching was caused by WAY overkill control surface movements. I adjusted everything to 40% of what they were before and it flew much better. Need more tinkering as I mentioned.

Also I didn't get any video, since it was too dark and my betrothed had gone to the exercising thing.. that she goes to ( :confused: insufficient vocabulary ).

Well batteries are recharging and my friend is coming to visit tomorrow and then I'm guessing we can get some footage, provided the weather stays calm :cool:
 
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EraJomppa

RC Enthusiast
#11
Unfortunately aluminium (of this size) would need the piano wire with it to provide strength. For the looks I really liked the aluminium, but for practical purposes the wire landing gear is the way to go. And right now I'm not really trying to improve the looks :) Maybe later.
 

EraJomppa

RC Enthusiast
#12
Carebears: I need your help!

Okay, I'v got this problem here. I'm not sure how to put this, but I'm not sure whether the plane is tail heavy or nose heavy... or is it either?

Lets start with the control surfaces. All other are flat (ailerons and flaps), but depending on the position of the battery, the elevator is in various angles OF DOWN. I'v always had to trim the elevator down, otherwise the plane would climb with throttle. The wings are flat (no incidence), the motor is directly in the longitudinal CG line (how high or low CG is) and has NO up/down thrust vectoring.

Now I have done few tests to discover the nature of the CG, 45 degree dive, glide test and full throttle behavior. I usually just fly around and try out the different battery locations and determine which is best. But here when I moved the CG forward, I utterly lost the ability to land (without flaps), when I cut the throttle the nose went down and didn't rise no matter how much I pulled the elevator up until I gave throttle. When I moved it backwards I found that I had to trim the elevator considerably down to compensate the plane's urge to pull up when I gave any throttle. Also the plane got very sensitive in the pitch department.

I did the 45 degree dive test, where you cut throttle and dive in 45 degree angle down (if it pulls up, nose heavy [trimmed up], if it dives further, its tail heavy [trimmed down]). I found that in both cases, forward and backward battery placement, the plane acted like it was really TAIL HEAVY. It wanted to pitch up always! and when I moved the battery so far back that it kept the dive straight, I had A LOT of down elevator trimmed in...? that's not how it should go is it?

Then I did the glide test, which for me is just cutting the throttle and gliding it around and seeing how it behaves. The plane flies with minimal throttle and very slow, but when you cut it... it noses down. No matter how far forward I put the battery, the nose dropped a lot and I was not able to glide it properly. I would try to dive it a bit to gather momentum to be able to raise the nose up for a landing, but all I managed to achieve was more speed. The nose stayed down and it kept descending very fast. Normally even a plane like this should be able to glide some, but this just wont do it. felt like a seriously nose heavy plane.

Full throttle gave me some gray hair too. Even when moving the battery forward the plane nosed up in throttle, I had to compensate with down elevator. Then when you trimmed the elevator down, it would get really sensitive to any input and any wind that happened to blow, causing some unintentional dives at low altitude... I kept it a bit more trimmed up and put some down elevator myself when I wanted to get the plane fly straight...

I also tried harriers. I doesn't really harrier, more like it just slows the plane down, much the same effect as when I put down the flaps. The nose stays down, no wing rocking or anything, the nose just stays down and the plane slows down. I'm not sure, but I understand that nose heavy planes don't do harrier well right?



I made some my own conclusions, but I want to hear more from you guys before I go on trying anything. I feel like I got the hang of this plane and when I apply'd the flaps I actually go some decent landing in today and walked home with no damage to the plane at all which felt really good, since I did flip it many times trying to get the landings right.

But what I thought is:
I got some issues with the elevator.
-too much elevator compared to the stabilizer? I wanted to make the tail a bit "3D capable", but that might have caused that the plane to become more jumpy.
-It might be too small? that would explain why it can't harrier? I could try to increase the size easily enough, but I'm not sure whether to increase the size of the stabilized or the elevator and in what manner? (longer? wider?)
-It might be too close to the main wing? It might cause the pitch sensitivity when I go for more tail heavy CG and it really wants to keep the CG forward to maintain the stability? I'm not sure how I would go about correcting that or how to cope with it?
-Overall it might be "this kind of plane". Since I wanted to give this plane more wingspan to make it more typical "bush plane" it might cause some kind of problems like this?


ANY feedback would be appreciated. I know some people gave up seeing how long of a post I wrote :eek: so thanks to anyone who has read this far and wants to help me out :)
 

EraJomppa

RC Enthusiast
#13
Ill risk posting this after the long one, but I hope somebody reads the post above :p

So here are some video clips from one of the earlier test flights. I decided to give the youtube video editor's stabilization a try, since my betrothed is not so very steady with my phone ;) Same video, the other one is the stabilized one if you are interested in comparing the two.




Since there were kids nearby and not very large space to fly in anyway I couldn't try inverted or loops or anything, just basic flying and testing and TRYING to land :p Afterwards I got the hang of it with full flaps and little bit of throttle though.