AJ1202

Green the confusion comes in when you compare SD Cub to other knock-offs, not that all the knock-offs are bad but A Shun Da direct drive plane will come with a 6X3 prop, some of the others will come with a 7X4, The Shun Da geared motor set up uses a 8X4 prop. Now I found the cub will barely fly with the 6X3 prop and unless you are experienced and truley can FLY the plane and not just control it (that was me when I first got mine ) then the 6X3 is going to cause certain failure. I opted to go with the 7X4 and just take a chance on my motor not lasting as long as normal, the motors are 6.00 to replace or you can go brushless for 9.00 and take the meak little Cub into balistic mode with the right set up. I had mine set up to where I could ROG inside of 2ft and go vertical to 100ft in about 4 sec. I could get 20 min flights.
It took me almost 2 years to try a lipo and then 4 more months to go brushless, I have never looked back
Be patient and learn to fly then make your next step,
I would suggest, if your sure your plane is toast trying a kit to move your stuff into, I put SD tronics into a few different planes while learning, first was the GWS Beaver, then the GWS E-Starter which I still have to this day and fly on a regular basis, I have of coarse converted it to brushless, it's in my models if you want to take a peek, very nice flying plane, very stable and floats nicley.

vega2614

Yeah, I definitely agree about the brushless/lipo route. AJ told me to try them out a long time ago and I hesitated, mostly due to the price tag. But when I found the cheap deals at United Hobbies, I couldn't resist. Now I'll definitely never go back to brushed/NiMH. I enjoy having a plane that's adequately powered, even enough to handle what I guess to be 15mph wind gusts (not just steady wind).

I flew last night at around midnight in a parking lot that was lit with some lights. I also had an LED attached to each wingtip. It was difficult to fly to say the least. I'd frequently lose track of directional information, and all I'd see is a red dot. The light-polluted overcast skies of the Chicago suburbs didn't help, because the yellow cub body blended with the sky. The cub also looked like it was flying a lot faster than I think it was. Some guy stopped by and started watching. I got sort of freaked out because I didn't know what he was going to do at first. It turned out that he frequently comes to that place to drive his nitro RC car.

akdude47

Just a quick note, but the Cubs I have both came with 7" props, but they were very flimsy. The APC 7x4 was much better even though it was the same size

enricong

switching to 7x4 just stresses the motor and battery more and reduces the MTBF. However, my motor did not have any problems until I nosed in a few times and had it hit directly on the shaft. The prop saver will most likely save the prop in almost every circumstance. If installed very close to the motor, it will probably save the shaft too.

I dont know how experienced you are, but if you are new, I'd just spend more time flying than trying to modify. At least the plane will fly relatively the same way everytime.

Either way, I'd wouldnt both reusing the electronics if I was going to build another plane. I might consider reusing a motor if the plane was smaller.

I thought about flying in the dark before, but its seems too hard. I figured LED's on the wingtip wouldnt be enough. I'd need a way to know if its coming towards me and if its upside down. maybe a light pointing forward.
I think the best thing would be to some how light up the outline of the fuse and wings. Neon lamps would be best but you prob can't fit a transformer on the plane. maybe several lines of LEDs.

OR, get a friend to come with you with one of those cheapo 2Million candle power flash lights and have him follow the plane.

GreenAce92

Hey Vega thats cool to hear that you get some audience while you fly your plane. When i take my Pkz J3 Cub up in the air people watch me too sometimes as i do my low level loops and barrel rolls. I think for this plane's electronics i will just leave it as it is. If i wanted a lipo and brushless setup i think i will just buy a nice optic 6 transmitter and go from there. I just bought this plane as a fun little plane so that when i couldnt take my PKz Cub up i could use this one. I am going to build a beaver out of Polystyrene. Im scraping the warbird for now. And AJ i have the SDM piper cub but i figured since i already have a pipercub why not built another plane thats stable. I am building another piper cub for the other SDM cub becuase i did that 2 deal for 80$. I guess i can consider myself an intermediate pilot as long as i have a good plane but the first time i took my SDM up i got her to fly its just when i thought i could fly the plane at half throttel is where i went wrong.

Once i get my foam which should be tomorrow ill start my builds. Ill make a build log on here and wattflyer. Well maybe ill just show pics to you guys.

Thanks.
One more question. If i hook up the 6x3 prop on the stock direct drive motor will it produce the same thrust as it did with the 7in prop it originally came with?

walkermsg

I've seen the nightime setup for small planes. They are small current draw LED's . I'll try to get the URL for you. I know they are just like they use on boats, a white LED for the tail and red for the left wingtip and green for the right wingtip. That way you can tell exactly which way the plane is going or coming.

vega2614

A 6x3 prop shouldn't produce as much thrust as a 7x4, but there are many factors to consider, including motor efficiency and rigidity of the prop. I've seen prop data that show a larger prop actually yielding less thrust, but typically, the opposite is true. That's usually in the case where the amp draw is approaching max amps of the motor, so a prop that's too large for the motor. I definitely saw an increase in thrust using an 8x3.8 prop over the stock 7x#.

Night flying was difficult, but it definitely helped to have the parking lot lights. When the cub got far away from the lights, it was pretty difficult to see. Like I said before, I saw 1 or 2 red dots in the sky, depending on which way the plane was facing. I don't think it would really be possible to fly like I did without a stable plane like the cub. The cub is rarely inverted, unless I'm really trying for that to happen. In terms of which way its facing, you can tell by motion of the plane from the side. As far as whether it's flying towards or away, just watch what happens. I wasn't really doing any crazy stunts besides some loops (low altitude so I could see it with the lot lights), so I pretty much knew where it was facing/heading all the time. One of the hardest parts though was distance judging, because it was just a dot in the sky at times. I think that's why it looked like it was flying faster than during the day.

GreenAce92

Ok i have just finished my plans for the Beaver so im working on getting some foam right now. Has anyone replaced the prop nut and the prop holder. I lost the tiny little nut that goes on top of the prop to hold it down. Also if i use the 6x3 can that still produce enough thrust to fly?

Thanks.

vega2614

Green, go here for an idea of whether your plane will fly: http://adamone.rchomepage.com/calc_motor.htm . I'm not sure what you'll input for the motor, but maybe if you search around the net you can find info on a direct drive 380 motor (at, I'm assuming, 8.4V). But, the only true test is to actually try flying it.

I don't think you ever told us the weight of your new plane. Again, the thrust to weight ratio is critical in determining whether the plane will fly or not. Your motor could have half the thrust with a new prop, but if the weight of the new plane is significantly less than the stock cub, then it could fly. Also, I'm assuming your plane's aerodynamics are good.

I'm using a PROP SAVER instead of the prop nut.

GreenAce92

I still havent gotten the pink foam yet but its ruffly around 14-16 oz. But i will have a semi thick airfoil so i can get a significant amount of lift. The direct drive 380 brushed motor's shaft is 2.3mm right? Ok i will try that link you gave me. Has anyone ever used the 6x3 prop? How much thrust did it produce?

Thanks.

vega2614

I'm guessing the plane will be underpowered at 16oz with a 6x3 prop. That's a little less than the cub, and the cub has problems flying with a small prop like a 6x3. I can't tell you what thrust you will be getting though.

Yeah, if I remember correctly, the 380 motor has a 2.3mm shaft. Measure it to make sure though.

GreenAce92

It sounds like it the way you put it, im hoping its not. I guess i will find out when i get the props. I will probably get a weebit larger prop just in case.

vega2614

Yeah, good idea. Good luck.

vega2614

Wow, I just installed that 2409-12T motor on a pusher plane a friend gave me with a custom cut 6x3.8 prop (from an 8x3.8). I get probably about >400g of thrust at 50% throttle. I didn't want to go WOT until I have a good prop on there. I'm definitely excited about using it. Makes me want to get a Stryker. Now I just have to hook up the servo pushrods...

enricong

Just went out, had a nice flight. I still had the same issue with the nose up and roll issue.
As long as I kept the speed slow I was able to fly ok. I was taking onboard video so I wasnt trying to do anything facy anyways. Its been posted on youtube.

GreenAce92

Well heres the fuselage i just built im abandoning the beaver idea im just going to build a plane. I am going to trim the stuff for prop clearance.

vega2614

My friend makes planes out of that same pink material. He reinforces it with wooden rods throughout the fuselage and wings. He also covers the entire thing with packing tape. The products are virtually indestructible. I think I mentioned it before, but he even crashed it into a tree once at 35mph and no damage. He attaches the wing to the fuselage using rubber bands connected to rods sticking out directly below the wing. That way, the wing doesn't break during a crash and just pops off, working sort of like a prop saver.

vega2614

My LHS has pushrods but they are way overpriced ($6 for two, but includes servo linkages). Unfortunately, UH doesn't sell pushrods yet. I know this is hardcore unsafe, but I made pushrods by soldering and then hot glue gun gluing two straightened paper clips together, and then taped them to a thin stick of balsa wood for reinforcement (I noticed they were bending a lot). I've done extensive testing on the ground to make sure they don't snap or bend, but we'll see how it works in the air. My bigger fear is that the servos will fail. I'm using my old stock cub Rx/Tx for this custom built pusher plane, and one time I was doing a test and suddenly the rudder servo went full left rudder and stayed there while I was messing with it. I had to cycle the power to get it working again. I don't really care about the plane body, but I do care about the lipo, servos, motor, and ESC inside the plane.

GreenAce92

Well im going to get my props or should be tommorrow and propsavers. Also i will continue my build. Also let me know how your pusher plane goes hope those pushrods work for ya. Couldnt you make your plane where its positively stable and it will level itself off if you go in to a dive so you can just control the plane by your throttle?

vega2614

Yeah, that's how 2-channel planes work. Usually they fly level at half throttle, and increase altitude at full throttle.


I gave it a try today. The 2409-12 was providing an insane amount of thrust, but I think the plane was balanced poorly. It flew for about 200m in a half circle before stalling and crashing. I somehow broke the prop. Not too surprising, since I wasn't using a prop saver (I can't because the location of the servos interfere with the prop when a saver is used). It was very responsive. I think I'm going to use one of my old stock cub props, since those seem to fit. The plane is pretty tail-heavy, but I don't really know how to fix that without adding a lot of weight to the nose. Right now the CG is about 2/5 from the leading edge of the wing. The plane probably weighs about 500g now, at least.

GreenAce92

Hmmm is it like a Delta? Or no does it still have tailwings. Well sorry to hear your flight didnt work that well. At least you were able to get some air time you should be able to fix it. Hope your next flight works better. Could you post a pic of your plane?I wasnt able to get the props today so i guess i will just work on the wing.

GreenAce92

Well heres the plane or i should say thing the only thing that makes it look like a plane are the wings and the rudder+tailwing.
If you have any comments feel free to say them.

akdude47

Looks great! Are you going to spray paint it or anything? How does it balance? What kind of prop is on that?

GreenAce92

IT FLIES!!!!! IT FLIES!!!!!

Well sorta.


Im not sure if any of my spray paint is foam safe. I have to work on getting it not to veer off to the left after it takes off of the road. Umm how hot should the batt and the engine get? Its 95 degrees here where i live and the battery and motor are both hot enough to burn you like if you touched the tip of your toaster for 1 sec. The prop is homemade im using it for now because i wasnt able to go to the hobbyshop and get some props and a propsaver. It flies on about 2/3 power when you take off of the road. Its about 1.3in back from the leading edge of my wing.

akdude47

The battery should not get that hot, if it could burn you. IF so, you are over propped, but a trip to the LHS will fix that.