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J3 cub build log

Started by girishsarwal, July 24, 2012, 12:15:01 PM

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girishsarwal

Here is another J3 cub build log, we've recently had two builds, here comes another one done over the weekend.

Day 1 - Cut out horiz stab abd vert stab. Completed sanding of both fins.
- Tried it multiple ways of cutting neat curves. http://www.rcindia.org/tools-materials-and-building-techniques/cut-coroplast-with-smooth-edges/msg109310/#msg109310


Day 1 - Completed basic fuselage structure. Some basic decals done. Added a landing gear made of 3mm GI Wire
- Don't like the way the rear gear has come out. Needs a change
- Decals done using black vinyl sheet.
- fuselage has a boxed design. the inner box is used to stow all electronics in place

gs

girishsarwal

Day 2 - Completed the wing structure.
- I used a PVC round pipe for the spar; Slightly curved due to storage. I wanted a straight wing so thought sticking to coroplast should ensure its straightened out but pvc wins here and what i got was a ~2 deg dihedral, although a little curved. Let's see how that helps/bothers the flight.

Day 2 - covered the main landing gear with coroplast
- Wasn't enjoying the exposed GI Wire of the main gear.
- Still got to do something about the rear landing gear, it looks a little stupid sticking out like that

I did not have a smaller rear wheel atm so used the same front wheel. Guys, recommendations on how that would affect the flying chars.
gs

abhay

can share the plans and specs
I can take off and fly well. Its landing which sucks :banghead::banghead:

girishsarwal

Day 3 - fixed the rear landing gear.
- Moved the landing gear a little backwards (only worried about cg a little now  :-\)
- Left the original coro piece where it was, might serve as additional vert stab. comments/recommendations?
- Attached the landing gear directly to the rudder via a single bend in the wire. Its is now stronger and easily bears the weight without the coro collapsing. Earlier it would sway with the faintest rustle of air
- had to cut coro after gluing it, so the results are not very neat, but the compromise between looks/functionality was worthy I guess.
- Also, do not like the two pieces of coro stuck later on to the rudder. will add to drag :(. Plan to camber the TE of the wing to compensate for a slightly slower speed. Still need to cut out the ailerons.
- added collars to the wheel. The collar ring being much bigger than the wire, used some plastic tubing on the wire.

gs

girishsarwal

- Plans attached. Same as those bhavesh used recently. Credit to bhavesh for the getting hold of them.

- Specs:
Estimated AUW - 850g
Coro - 3mm (CA glued)
Motor: 1400 KV Mystery 2210
LiPo - 2200mah 3s Mystery 25C
ESC - Mystery 40A
Servos - 9g
Rx - Flysky 8ch
Wheels - 30mm from THS
Control horns - pvc
Gear wire - 3mm GI
gs

girishsarwal

got some time yesterday...added to the build...

- Electronics incorporated in the fuselage former- Flysky 8CH Receiver
- Servos assembly completed on servo tray and wing bottoms (dorsal) - @VC - I'm falling in love with this term now
- Added struts for tail assembly - the vert fin was fluttering mad otherwise.
- strengthened the empennage using alloy wires (I've used alloy wires instead of GI, found them to be lighter and tighter). Got them from electric stores, its the same wire used for pulling other wires when electricians wire up via conduits. Realized they have better torsion and do not break easily on bends. Same for control rods
- Independent servo on the wings
- Landing gear is ready, needs to be affixed
- CG lies on spar and all seems balanced till now with everything up

Next Modifications:
- I have not yet decided on the prop, this one is only for display, I might go in for a slow flyer prop based on the flying characteristics on the field (provided it flies :D)
- Need to add zip ties from the fuselage former to the fuselage. The last time I spinned the prop full throttle, the fuselage former flew out of the fuselage  :giggle: :giggle:. It was fun watching.
- change the wing receptacle to plywood (both front and aft where the wing screws in), coro will give away soon.
- front cover and cowling
gs

girishsarwal

With wings
gs

PankajC

Spektrum DX6i | EP Pusher Trainer | EP CUB |

girishsarwal

Thanks Pankaj,
The cub had a crash after launch, launched it like a noob, stalled and came down. So I went home and practiced a couple of projectiles which ended up bullying the fuselage. It's back to the workbench and I should soon be giving it a new fuse.
gs