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Old Sep 17, 2012, 04:00 PM
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South Florida
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Originally Posted by peterswolf View Post
Sorry to hear about your crash, but glad it was easy to fix. How did you fix the ESC issue? I haven't maidened mine yet, but unsure how to sync the ESCs, what needs to be done? thanks!
Just turn on the transmitter, then move throttle to full HIGH.

Turn on the plane and wait for ESC tones.

Then lower throttle to full OFF, wait for the 'happy' ESC beep sounds, and you should be good to go.

Made all the difference in the world on mine.

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Old Sep 17, 2012, 05:44 PM
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Houston, TX
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Just for the sake of safety, you should take the prop off when you sync the ESC. Too many stories of people getting cut up by run away planes.
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Old Sep 17, 2012, 05:50 PM
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Grand Rapids, MI
Joined Jun 2005
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Anyone have some tips on getting the ESCs to arm? They used to work fine, but now I have to site and wait and wait or unplug/replug the battery multiple times to get it to arm. The throttle trim is down and the Rx is binding. And, sometimes when the ESC finally do beep, I only have about half throttle until I unplug/replug the battery again.
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Old Sep 17, 2012, 11:57 PM
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Monahans TX
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Small world, tracknoob!
If you've got an extra channel, program differential thrust into your JPower.
That first flight might have had a completely different ending if you could have synched up the two motors with the rudder.
BTW, that weird effect that makes the props look crazy is from the rolling shutter of the video camera.
It also lets you see how the two motors aren't synched up towards the end...
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Old Sep 19, 2012, 08:46 AM
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So I got to maiden my P-38 this morning. Maiden flight was pretty nice, needed a fair bit of trim to keep from dipping to the right but other than that it was a nice flight. Landing was a breeze she glides right onto the runway. I bought this plane used and replaced the landing gear all around with servoless retracts and some nice cushioned dubro tires. After doing some manual adjustments on the ground took her up for second flight, flew around 5 minutes and then landed perfectly again. I had been flying strictly elevator and aileron up to this point. I had one battery left and 30 minutes still before work, so took her up a third time, doing some coordinated turns using lots of rudder she turned nicely, however after about a minute of doing that she suddenly banked hard right and did slow spiral to the ground, she was about 60 to 80 feet up and hit the ground pretty hard, although it was in some pretty tall grass just on the other side of our runway. I broke one prop blade clean off, there was no sign of signal loss, receiver was still solid orange (AR600 DSMX), some scrapes on the nose and the left motor is loose (whole plane vibrates upon powering up. I checked with flight logger and no connection issues reported. That's when I noticed that the entire left tail section had popped off the boom! Now I can only assume as I have no video or didn't notice, but perhaps during flight this came apart, it would certanily explain the sudden drop and slow spiral down to the earth. As it nosed in, there is no damage anywhere else on the plane and as far as I can see no other part of the tail hit anything (I'm sure I'd see other damage if the tail broke off due to impact). So I guess I'll have to get the left tail section reattached to the boom and then sort out the loose motor. I think I'll take this opportunity to upgrade to MAS counter rotating props as well. Hopefully there s not too much damage inside the motor areas I'd like to be flying by the weekend again. Hopefully I'm right about the issue being the left tail section coming loose in mid air, otherwise I can't explain it at all...
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Old Sep 19, 2012, 09:44 AM
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Cape Coral, Fl
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Quote:
Originally Posted by peterswolf View Post
So I got to maiden my P-38 this morning. Maiden flight was pretty nice, needed a fair bit of trim to keep from dipping to the right but other than that it was a nice flight. Landing was a breeze she glides right onto the runway. I bought this plane used and replaced the landing gear all around with servoless retracts and some nice cushioned dubro tires. After doing some manual adjustments on the ground took her up for second flight, flew around 5 minutes and then landed perfectly again. I had been flying strictly elevator and aileron up to this point. I had one battery left and 30 minutes still before work, so took her up a third time, doing some coordinated turns using lots of rudder she turned nicely, however after about a minute of doing that she suddenly banked hard right and did slow spiral to the ground, she was about 60 to 80 feet up and hit the ground pretty hard, although it was in some pretty tall grass just on the other side of our runway. I broke one prop blade clean off, there was no sign of signal loss, receiver was still solid orange (AR600 DSMX), some scrapes on the nose and the left motor is loose (whole plane vibrates upon powering up. I checked with flight logger and no connection issues reported. That's when I noticed that the entire left tail section had popped off the boom! Now I can only assume as I have no video or didn't notice, but perhaps during flight this came apart, it would certanily explain the sudden drop and slow spiral down to the earth. As it nosed in, there is no damage anywhere else on the plane and as far as I can see no other part of the tail hit anything (I'm sure I'd see other damage if the tail broke off due to impact). So I guess I'll have to get the left tail section reattached to the boom and then sort out the loose motor. I think I'll take this opportunity to upgrade to MAS counter rotating props as well. Hopefully there s not too much damage inside the motor areas I'd like to be flying by the weekend again. Hopefully I'm right about the issue being the left tail section coming loose in mid air, otherwise I can't explain it at all...
I think a few of us CF the boom to the tail for insurance. MAy want to do that in your case for the next flight.
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Old Sep 19, 2012, 09:47 AM
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United States, FL, St Petersburg
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Originally Posted by Hink64 View Post
I think a few of us CF the boom to the tail for insurance. MAy want to do that in your case for the next flight.
Ya I must say looking at the way it seperated, it's a super clean break, with only a tiny foam piece the seems to stick into the boom, it looks like as if the glue holding it together just let go. I have some CF rods at home, I'll be sure to put in there during my repair, I might go ahead and pull apart the other side to do the same as well thanks for the tip!
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Old Sep 19, 2012, 10:17 AM
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Canada, ON, Hamilton
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Here's what I used for the stab.
page 259 post 3883

http://www.rcgroups.com/forums/showt...nav8r&page=259
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Old Sep 19, 2012, 02:39 PM
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United States, FL, St Petersburg
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Thanks for the tips guys, I managed to get everything back together today. The motor just had a loose grub screw, so that was easy to take care of, and while I was in there I installed two new MAS props, pusher on the pilot's right hand side and reversed the motor, so now it's counter-rotating. I removed the whole tail section, put in CF on both sides and put it back together, already seems stronger than before. So now just wait until everything sets and I'll be back in business. She'll just need a bit of touch paint and then all done.
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Old Sep 19, 2012, 05:39 PM
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South Florida
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Originally Posted by peterswolf View Post
I removed the whole tail section, put in CF on both sides and put it back together, already seems stronger than before.
Yup!

This morning at the field, I was taking the plane out of the car, and I'll be darned if I didn't knock the tail against my head liner. I thought it was a light little knock, but once I got the plane on the stand, the left boom was broken off at that very weak section at the tail. I thought I would spritz a bit of CA on it, and be good to go, but when I disconnected the control rods to let me pull it apart far enough to get the CA in there good, the *other* side just popped off!

Wow. Tail totally off, and as big as the horiz and vert stab and elevator is, just those tiny two points holding it all together. What a terrible weak point.

Luckily, I had a foot or so of CF rod stock in my box, so I just cut it into two rods leaving a bias to be sharp on the point, then skewered each boom end, and then hit it with CA and kicker as I carefully lined the tail assembly up and pushed it back on. I think it's now much stronger than stock, even as an emergency field repair.

Here is the post-repair flight -- seems to be mighty fine to me.

Carbon rod reinforcement of that area should be listed on the 'out of box must-do things' for this plane, if it is not already.

j power v1 1400mm p38 flight 3 (4 min 19 sec)
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Old Sep 20, 2012, 07:35 AM
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United States, FL, St Petersburg
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Flew mine this morning after the fixes, and it flew perfect!!! Thanks again for the tips guys.

As for converting to counter rotating props, it felt like it had a little more speed but I didn't notice any other difference in it really. Turns may be a little smoother but that might have more to do with fixing the tail boom I was flying in 1mph wind this morning, as calm as it gets really, and I was still able to float in on landing with no power, what a great plane! (V1 from HK)
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Old Sep 20, 2012, 03:46 PM
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Houston, TX
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I think the advantages of counter rotating is minimal and probably not noticeable. With the weight of motors and structures further out in the wing, the roll tendency is suppressed somewhat. It's the old ice skater spinning with arms out or in kind of effect.

I did a twin with counter rotating but it ended up being for coolness effect. On my second twin, I went with simplicity and rotated both the same direction.
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Old Sep 20, 2012, 06:59 PM
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Monahans TX
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I may have posted something similar to this in the past, but it's worth bringing back up for anyone that missed it...

Plenty of old FS twins that used identical rotation on both engines.
The problem with those was that you have a critical engine, and it occurs on the engine that swings a blade downward on the outside of the nacelle.
In other words, if you have CW rotation engines as viewed from the rear, the critical engine is on the RH side.
When you have positive AOA, the downward blade gets more of a bite and produces the majority of the thrust.
Since this downward blade is farthest from centerline, you get more adverse yaw when the LH engine quits than you would if it was the other way around.
Sometimes it's not a big problem, sometimes it's a very dicey situation.
That's the reason for so many twins to have opposing rotation engines, to eliminate a critical engine issue.
Quite a few twins out there that would be ridiculously unsafe if it weren't for counter rotating engines, so there's definitely a reason for it.

For the JPower, it's not an issue to be concerned with because you're pretty much screwed if EITHER engine quits LOL
I've had engines quit on both sides and I couldn't tell the difference in handling between the two...your only option is to cut throttle and hope you have some airspeed or altitude to play with.
Programming differential thrust only reinforced my idea that counter rotating props make very little to zero difference at this scale (or perhaps it's just this model?).
Reversing the mix on the diff. thrust so that the rudder works correctly and the motors work counter productively (ie left rudder normally spins up the right motor, but now it spins the left) had given me a great idea how much more overpowering the thrust from the motors was in comparison to the effectiveness of the rudders.
It was like the rudder was dumbed down to 50% rates, favoring thrust instead of rudder.
To make a long story short, if you lose a motor on the JPower and attempt to maintain level flight with full rudder deflection, it'll be like flying with 50% opposite rudder input until you chop power.

So, is there any advantage to having counter rotating props?
Sure, it's actually more efficient in both theory and practice.
You might not notice it, but the airframe is actually trimmed somewhat to mask the P-factor.
Eliminate the very slight deflections on the control surfaces and the airframe will be somewhat cleaner aerodynamically.
You'll also notice that there is some P-factor on takeoff, but not nearly as much as a single engine taildragger.
Imagine jamming the throttle from a standstill and not veering off even the tiniest bit, not favoring a wing during a powered stall, or rotating while attempting to hang it on the prop...there's an advantage to that as well.

All in all, there are advantages to counter rotation, but you have to weigh them against finding a scale prop to match or going with a non scale prop (which eliminates the scale advantage).

I was happy with mine just the way it was, but if I could find the same prop in opposite rotation just as easily I'd probably go that route instead.
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Old Sep 24, 2012, 08:09 AM
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I can't wipe the grin off my face today. Got another 2 flights (2 Lipos) after work today just before getting dark. On the second battery I actually landed before the time was up because it was almost dark and the plane was becoming a silhouette against the buildings and trees. Otherwise I have 8min set on the timer and with a 3S 2200 30C I use up less than 50%, so I'll be increasing to 10 min. and porbably stay there.

But it was sooooo nice. It flys great, and easy, and smooth with no bad habits. Very nice long scale take offs with just enough elevator for a nice climb into the skys, play around with it up there, stall turns, scale turns, stalls, slow fly bys at eye level, fast fly bys about 2 meters away from my face, it just makes you smile. And at the end nice controlled landings with a nice flare. I always land with some power on, but it gets slow enough to just ease it in and do necessacry corrections just before touch down, and then let it roll down the runway like the real thing.

I have had 6 flights in all - the first 2 were grass belly landings, the other 4 were on the runway with retracts. Until now no failures or damages. The tail shows no sign of coming off at the end of the booms, and the stock under carriage is holding. One Servo on one of the mains sometimes hung before the last flight, and just buzzed and would not retract. a light push and it would retract. After take off, maybe because of the wind pressure in flight, it retracted fine, and the landing showed no problems. Maybe the first sign of failure for the stock retracts. Let's see. Just have to fly it more.

In reaction to the last few posts above, I didn't notice any P Factor or torque effect from the engines or props. It just runs straight down the runway and pulls up in a straight flight path. With all the advantages of counter rotating props that there are, and there are, I just don't think this plane needs them. Maybe it's the scale or just because of the design, it is super stable with the stock props IMO.

The only mods I have are a shut down of the nose steering when the U/C is retracted, there's a post here explaining the mixes, and the ailerons slightly raised as well as aileron differential. Right now I'm very happy with it, maybe at a later point I'll reduce the spoileron effect or differential to see if there are any improvements in other areas.

Have to find someone to go with me to take some picture to post. Films are out because Youtube is blocked here in China so wouldn't be able to post....
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Old Sep 24, 2012, 10:59 AM
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Gadorey, Is yours stock? v1 or v2? I have stock v1 and use 3s 2300mah packs and a 7 minute flight would be pushing it. As is, some of my packs get puffy if I'm WOT too much. Failing to see how you're going to get a 10 min flight!
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