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Old Oct 21, 2012, 12:33 PM
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Not As Off-Topic As You Think!

Just thought I would make a quick post that might be a little off-topic, but not entirely. For my birthday, my daughter and son-in-law gave me a J-3 Cub. They obviously don't know a whole lot about my hobby. They didn't realize when they ordered it, for instance, that it has a 6-foot span, that it didn't come with servos or a motor, or that it is a gasser - not electric! It is also a plywood, balsa, Monocoat build, with not a gram of foam. I haven't built a wood/Monocoat airplane in 30 years, and haven't ever done a gas-to-electric conversion. I was up for the challenge, though, and didn't want to offend my new son-in-law by asking where I could return it so...where to start?

Specs said it was supposed to weigh 5.8 lbs, and use a .45 to .60 2-cycle engine. I wasn't planning on doing 3D with this, and I didn't want to get a power setup that would require me buying a size of battery that isn't in my current inventory, especially some big $60-apiece, five or six cell. When I did my calculations for a .45 to .60, equivalent electric motors seemed too big, and used much larger props that I wanted. So I got to thinking... My Extra weighs nearly five pounds (4lb, 11 oz.), and with the Aerosky-standard motor and 15-inch prop, it produces 650 to 750 Watts, and generates around 6 lbs of static thrust, depending on which of my 4-cell batteries I use, and their state of charge is. I have no idea what the KV of the Extra's motor is, and trying to find an equivalent motor was going to be a crap-shoot, so I thought, why not? I'll just use the same power system as the Extra, and that should be good.

I ordered the motor and ESC from Nitroplanes, along with a couple of extra props, but there were two other strong desires I had for the Cub: It really needed a wood prop, just for looks, and it needed about a 1-inch smaller prop so that I wouldn't be constantly replacing broken props.

The Extra has a 15 X 7 prop, so it seemed like I needed something around a 13 X 9. I couldn't find anything like that, but Master Airscrew has a 13 X 8 that would look really good. My concern was that an 8-inch pitch wouldn't give me enough thrust. I went down to my LHS and picked one up, though, just to test. I reamed the prop hole to just almost fit over the machined-in spinner mount of the Extra and then forced it onto the Extra prop adapter, using the bolt and washer to press the prop over the spinner fitting. That made for a nice solid mount.

I grabbed the only charged-up 4-cell I had handy - an older 2650 mAH Turnigy that probably wasn't quite fully charged - and plugged in my Watt meter. With the 13 X 8, it pulled 521 Watts, 38 amps, and 5lb 4oz of static thrust at 13.8 Volts. The stock 15 X 7 prop pulled 641 Watts, 45.5 amps, and 6 lb 2 oz static thrust at 14.45 Volts. I figured if worse-came-to-worst, I could still use the 15 X 7, so I decided to press on with the Aerosky motor.

The end product is in the photos below. You can see that I even used the same motor mount! The Cub came out weighing right at 6 lbs. With the MAS 13 X 8 and a fully charged 4-cell, the power system drew 590 Watts, 40 amps, and produced 5 lb 13 oz on 15.1 volts. That comes out to 98 Watts/lb and pretty close to a 1.0 T/W. The plane cruises at a little over half-throttle, and will stay airborne 6 -7 minutes and still leave 3.8 volts per cell. It has plenty of power, but I probably need to put in a little more down-thrust. It flies a lot faster than I expected, and seems a lot more comfortable at the slightly-over-half-throttle setting.

Although it's not the plane I would have bought for myself, I am very pleased with the way it came out. Heck, I discovered my Monocoat skills haven't atrophied even over three decades of not being used! All that, and there is peace in the family - except for my wife, who isn't thrilled with having another 6-ft span airplane in the garage.

Sorry for wandering off topic a bit, but at least subscribers can pull out power data applicable to the Extra! And no. I didn't cannibalize my Extra for any parts!
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Old Nov 01, 2012, 06:42 PM
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Whups. Received my Aerosky Sbach today only to find my wings and horizontal stab all warped, wings not so much as the ailerons. Submitted a ticket with Nitroplanes.com, so we'll see where we go from there.

Pilot was also dislodged and broken in the 340 cockpit, but I was going to use the 342 cockpit without a pilot anyway. Otherwise the plane is in good order, rudder and vertical stab looked good and all electronics work good. Fuselage was good and motor's solid.

Hopefully they'll just own up and send replacements. That was a definite buying factor, having access to a full line of replacement parts.

We'll see what happens.

Regards...
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Old Nov 04, 2012, 09:13 AM
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Whups. Received my Aerosky Sbach today only to find my wings and horizontal stab all warped, wings not so much as the ailerons. Submitted a ticket with Nitroplanes.com, so we'll see where we go from there.

Pilot was also dislodged and broken in the 340 cockpit, but I was going to use the 342 cockpit without a pilot anyway. Otherwise the plane is in good order, rudder and vertical stab looked good and all electronics work good. Fuselage was good and motor's solid.

Hopefully they'll just own up and send replacements. That was a definite buying factor, having access to a full line of replacement parts.

We'll see what happens.

Regards...
Your warpage looks typical, though probably a little worse than most. My first Extra 330 had really warped ailerons. I glued a carbon fiber strip to the trailing edge to pull them back into shape. My second one was warped, too, but not as bad. I just left them because I'm lazy. The right wing was slightly warped as well. It flies all right, but doesn't trim out very well. The trim requirements change slightly with airspeed, which makes aerobatics a little sloppy looking.

I've found NP to be pretty good about sending replacement parts, if they have them in stock. If they put them on back order, you may never get them, even when they come back in stock. They sent me a replacement for a warped Dynam SR Trainer right away when I needed that (I had to send photos to Michael Raiden to get it authorized, though). They put me on back order for some other part, though (I don't remember what it was now) and after a couple of months I noticed the part listed on their web site. I had to call them to tell them they had it back in stock. They sent it right away after that, so that's good. I've been waiting a couple of months now for a promised replacement set of servoless retracts for my Dynam Grand Cruiser. Their website still shows them out of stock, but I keep lookin' and hopin'...
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Old Nov 05, 2012, 05:34 AM
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They were pretty quick to say they'd send replacements but they don't have the same color wings in stock, so now I'm debating whether I should just get them and paint them or if I should ship the whole thing back for an exchange for the Orange/Black model. Depend on how much shipping I'd have to pay, already paid $58 shipping to get it here in Canada.
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Old Nov 05, 2012, 04:10 PM
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Originally Posted by teknokraze View Post
Whups. Received my Aerosky Sbach today only to find my wings and horizontal stab all warped, wings not so much as the ailerons. Submitted a ticket with Nitroplanes.com, so we'll see where we go from there.

Pilot was also dislodged and broken in the 340 cockpit, but I was going to use the 342 cockpit without a pilot anyway. Otherwise the plane is in good order, rudder and vertical stab looked good and all electronics work good. Fuselage was good and motor's solid.

Hopefully they'll just own up and send replacements. That was a definite buying factor, having access to a full line of replacement parts.

We'll see what happens.

Regards...
It looks like you have just a bit of bow, as opposed to a menacing twist. You should be able to massage that out with a bit of counterflexing and worst case scenario the hot water treatment.

Good Luck,

-Cub
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Old Nov 13, 2012, 01:16 AM
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Thanks Cub. I'll see what I can do. They're already sending new appendages albeit different color so I'd have to paint the whole model, so we'll see which way I go. If I can straighten them then I'll have extras.

I'm fairly pleased, they're sending new wings and horizontal stab, not requiring me to return anything and giving me a 15% refund because they couldn't send wings the proper color for my model. I got the white/blue/orange model and they're sending the wings for the orange/black model. (Not sure why they can't just open a box and send parts from that, they'd easily be able to sell off the remaining parts from the open box model).

However, I'm not adverse to painting the thing and making it unique.

Regards...
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Old Nov 13, 2012, 08:40 AM
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Ordered the red 330SC V2 yesterday w/spare prop & fixed parts (not realizing the fixed parts were oos). I'm just a bit paranoid that with the screws seeming to be so proprietary, that missing 1-2 would halt the build completely. Seems to be a widespread lipo shortage or something, so I ordered a couple 35C Nano 2650s from HK. The spec sheet claims 291g, but the listing says that they are 383g... Either way, I hope I can work out the CG w/o hacking (have a GP CG machine that I'll finally be able to use).

tekno: Glad to hear that they are working with you - wish I could do something about the fact that the Extra that I ordered last night is ~$14 cheaper this morning >=/
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Old Nov 17, 2012, 12:14 AM
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Seems to be a widespread lipo shortage or something, so I ordered a couple 35C Nano 2650s from HK. The spec sheet claims 291g, but the listing says that they are 383g... Either way, I hope I can work out the CG w/o hacking (have a GP CG machine that I'll finally be able to use).

>=/
I've noticed that kind of contradictory weight data on several batteries I've looked at on the Hobby King site. My Extra doesn't seem overly sensitive to C.G. changes due to batteries. I fly with 40C Zippy 2650's at 315.5g and 40/50C 3000's at 364.7g, and there's not much noticeable difference in flying characteristics between the two. 383g sounds pretty high for the Nano battery. I'm in the market for some more 4S2650's, so I'd like to hear what the actual weight is once you get it.
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Old Nov 17, 2012, 01:01 AM
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383g is their "shipping weight." 291g is the battery weight.
Charles
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Old Nov 17, 2012, 06:29 AM
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I've noticed that kind of contradictory weight data on several batteries I've looked at on the Hobby King site. My Extra doesn't seem overly sensitive to C.G. changes due to batteries. I fly with 40C Zippy 2650's at 315.5g and 40/50C 3000's at 364.7g, and there's not much noticeable difference in flying characteristics between the two. 383g sounds pretty high for the Nano battery. I'm in the market for some more 4S2650's, so I'd like to hear what the actual weight is once you get it.
ccpdx is correct - I hadn't noticed the discrepancy on HK batteries before as they were for things like a Supercub or 1S packs for my UM planes.

Actual shipping wieght:
Nano-tech 4S 35-70c 2650: 284.4g
Individual boxes: 24.8g ea.
USPS box+bubble wrap: 95.1g

In comparison, the Sky lipo 4S 2650 40c is listed at 330g - I hope you are right about the Extra not being overly finicky about CG, Nanos are light! One thing that concerned me about the Nano 2650s - their 'height' is 45mm. Hopefully I won't have to dremel the heck out of the battery compartment to jam them in.

DriverRX8 - have you had any issues with the canopy coming loose, and have you tried 5S yet? Also - are the wings a pain in the rear to remove/replace for travel to the field?
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Old Nov 19, 2012, 11:25 PM
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DriverRX8 - have you had any issues with the canopy coming loose, and have you tried 5S yet? Also - are the wings a pain in the rear to remove/replace for travel to the field?
See post #33. I had the transparency blow off, with dramatic effect. I have also had the entire canopy come off - several times, actually. It would pop loose and sometimes fly off if I had a hard landing. A couple of times, it came off in flight. I ended up putting just a sliver of Velcro on the back of the canopy assembly behind the pilot's head, where it meets up with the turtle deck. I haven't had any problems since.

The wings come off pretty easily. Just un-do the screws and the aileron connections and pull - just the reverse of assembly. If that's what you have to do to transport it, it's not really that big a deal. Fortunately for me, I can just squeeze the plane into the back of my crossover without taking the wings off.

I don't have any 5S batteries in my inventory. I always fly with either a 4S2650 or 3000 pack. I get six minutes flight time and still have 3.7V per cell after flying fairly aggressively, and the performance is acceptable, so I've never had a reason to try a larger pack. I would expect a 5 cell to weigh a little more than a 4 cell for a given mah capacity, so you might have to position the battery a little further back than a 4 cell, depending on how many mah it has. Since there is absolutely no documentation or specs to be had for the motor (that I can find, at least), I'd keep an eye on motor temperature, and also make sure your ESC can handle a 5 cell pack. The NP website says the ESC is 45-amps, but I believe it is a 60 amp. The power system pulls too many amps for a 45 amp ESC to survive very long. It's also physically the size of a 60 or 65 amp'er. Neither the assembly instructions nor the box say anything about the size of the ESC - at least that was the case with my Extra.
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Old Nov 20, 2012, 05:10 PM
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Well - the red Extra looks gorgeous out of the box, and so far I haven't found any visible warping. However - only ONE of the 4 screws that secure the halves of the wheelpants are the correct size! Just a few steps in, and already missing the correct hardware. I tried to order an extra 'fixed parts' kit with the plane to prepare for just this eventuality, but they were out of stock (apparently for good reason). 3 of the included screws' have a diameter that just floats in the holes, while the 4th feels like it will bite and thread itself if used.

Any ideas for a fix that won't involve duct tape or epoxying the halves together? I don't want to have to drive out to Lowe's or Home Depot after work tomorrow just to search for a few screws that fit. I was really hoping to maiden this on Thanksgiving at the field (my ONLY day off), as it will be 60F and almost windless in Pittsburgh - probably the last time for a LONG time.
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Old Nov 21, 2012, 08:08 AM
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UPDATE: For the tail servos, there is a free-spinning attachment on the servo arm that the pushrod is supposed to connect to somehow. From what I understand, the pushrod need to be positioned through this 'knob' on the servo arm - and tightened down with a set screw. When looking through the holes on that 'knob', they appear to be already blocked by a black screw that I CAN NOT find a way to adjust. I have gripped the 'thumbwheel' with pliers, and tried to spin the part on the opposite side of the servo arm, but it won't move.

I bound my Orange receiver and tested all servos/throttle and everything appears to be electrically intact. Aside from the missing wheelpant screws, setting these pushrods in place is the last issue to tackle before I can hopefully maiden her tomorrow.

Is anyone familiar with this servo arm attachment/pushrod issue on the Extra, and if so - could you please help?

Thanks,

Jay
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Old Nov 21, 2012, 09:58 AM
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From what I understand, the pushrod need to be positioned through this 'knob' on the servo arm - and tightened down with a set screw. When looking through the holes on that 'knob', they appear to be already blocked by a black screw that I CAN NOT find a way to adjust. I have gripped the 'thumbwheel' with pliers, and tried to spin the part on the opposite side of the servo arm, but it won't move.
That sounds about right. I think you just need a metric allan wrench set. Unscrew the black setscrew from the top part way out and you should be able to push the pushrod through the hole. You don't want the knob/thumbwheel/thumb-nut on the other side to be loose - that's keeping the whole assembly on the servo arm.

Not quite the same thing, especially since this one doesn't have a nut on the back, but here's basically what you're dealing with:

http://www3.towerhobbies.com/cgi-bin...&I=LXAHE6&P=ML


Charles
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Old Nov 21, 2012, 10:48 AM
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That sounds about right. I think you just need a metric allan wrench set. Unscrew the black setscrew from the top part way out and you should be able to push the pushrod through the hole. You don't want the knob/thumbwheel/thumb-nut on the other side to be loose - that's keeping the whole assembly on the servo arm.

Not quite the same thing, especially since this one doesn't have a nut on the back, but here's basically what you're dealing with:

http://www3.towerhobbies.com/cgi-bin...&I=LXAHE6&P=ML


Charles
Thank you for the help, Charles! I guess I hadn't realized that the screw could have already been really 'counter-sunk'. The need for a hex wrench would also explain why I couldn't find a 'driver-ready' head when I peered into the threaded hole. I may leave work a bit early to head home and try that out, and hopefully have enough time to shop around for the wheelpants screws.

I really appreciate your help and info. Thanks again!

Jay
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