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Old Jul 09, 2011, 11:19 PM
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Hobby King PBY

After having lots of problems with wings warping on the Electrifly PBY, I ordered the $80 from Hobby King. http://www.hobbyking.com/hobbyking/s...dProduct=17382

For $80, you get a plane that is just fun to build.



Specs:
Wingspan: 1380mm
Length: 880mm
Flying Weight: 850g
Motor: Brushless Outrunner 1300kv x 2
ESC: 25A w/BEC x 2
Servo: 9g x 4

Includes:
All hardware
Servo Extension Leads & Y-Leads
Tools
Glue
4 x Propeller
Instruction Book
Water-slide Decal Set

Requires:
Your Own 4 Channel TX/RX
1000Mah 3s ~ 2200mAh 3s Lipoly

In some ways, it is a bit of a hack as you have to carve wires into the underneath of the foam wing. But, the price is right.

Mine hasn't hit the water yet, but so far I have got it built. I used 6 channels so I can have individual aileron control and individual differential thrust on the motors.

More to come, but I thought I would start this thread in case anyone else has built one up.

Mike
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Old Jul 10, 2011, 07:20 AM
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Cougar429's Avatar
Canada, ON, Windsor
Joined Apr 2008
958 Posts
There have already been several threads here on the Hobby King/Nitro Planes/Guanli PBY that you can wade through for ideas, upgrades and solutions to problems. Here is the most recent I could find:

http://www.rcgroups.com/forums/showt...&highlight=pby

My own led me to the conclusion there were several key weak points. First was the extremely brittle foam and tendency for even slight contact to cause permanent damage. This was particularly endemic to the bottom when working from land and forced me to add 2 layers of 1/2 oz cloth. This also solved one of the other primary problems of fuselage: leaks when doing water work.

Another upgrade was the spanwise addition of C/F tape to the bottom of the wing as the afforementioned foam seemed to have little or no "Give", (allowable flex) before failure. I was pretty leery of the wing panel(s) separating outboard of their incredibly flexible wire struts.

A couple of additional suggestions concern the power system. The motor pylons currently have little or no exit area. This is critical for cooling air flow or it will stagnate around the motors and cause problems. You may also find the motors lugging down. Even with the cooling issue dealt with, if the motors are excessively warm or hot to the touch at the end of a flight you may want to look at other props. I found many manufacturers are too aggressive in their prop recommendations, causing the motors to load down too much. This affects motor performance, as well as excessive current draw on the battery and ESC and the resultant shortened flight times. My best performance came from a pair of M/A 8/6 nitro props.

Having the ESC's and battery buried in the fuselage where there is no opportunity for cooling air you might find some heating problems. Luckily they give you large enough ESC capacities to help that way, (25A each is good as mine pulled 17-19A total at full throttle). Just try to avoid long, high power runs or short durations between successive flights.
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Last edited by Cougar429; Jul 22, 2011 at 07:07 PM.
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Old Jul 10, 2011, 10:28 AM
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Thanks for the update. I will have to have a look at the wings, etc.

I mounted the ESCs in the cowlings after I water proofed them.

Thanks for the pointer on the thread.

mike
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Old Jul 16, 2011, 02:51 PM
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Thomas B's Avatar
United States, TX, Fort Worth
Joined Jun 2000
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Even though the Great Planes PBY hs a few small issues (mostly motor mounts, although the wings are fairly lightly built), I think the Great Planes model is much the better of the two.

The local owners of the foam PBYs have had a number of different structural issues, as mentioned above...more even than the GP model has shown. The foam fuse is quite weak at the hatch cutout, back close to the wing. This and other issues can easily be put right with decent builder that is not afraid to do a few mods.

The model is actually made by Guanli and Hobby King simply sells it, as does Nitroplanes and a number of other ARF dealers here and abroad.
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Old Jul 17, 2011, 08:03 AM
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Canada, ON, Windsor
Joined Apr 2008
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va3mw, be very careful extending the battery supply side wires on any ESC. It is possible, but in some cases requires the installation of extra capacitors identical to the ones likely already mounted near to or on the ESC.

It is much easier to extend the ESC/Motor wires without causing issues, although when I have the need to do this I either twist or braid the three phase wires to reduce RF generation.
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Old Jul 18, 2011, 05:45 PM
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Actually, I didn't have to extend the battery wires so to speak. That is how they sent it, fully designed to mount the ESCs in the engine pods. I can't see how they would have done it any other way with the wiring harness they sent.

I have no trouble adding extra capacitance to the battery leads if required, but I am not sure if it really needs it. Also, it does not have to be the same exact value of capacitor, as long is the voltage rating is greater than the battery you are using, it has to be an electrolytic capacitor and it wouldn't hurt to be somewhat the same value. Again, not critical.

I noticed that when I finished mine, that the angle of attack on the wing and the angle of attack on the elevator are vastly different.

Is this normal?

Mike
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Old Jul 19, 2011, 08:41 PM
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There are a number of reasons to like this over the GP PBY.

My thoughts.

It is a great bird if you are new to water birds. As it is foam, the wings don't warp, you don't loose the hatch cover on a hard landing and if you do, the the hatch cover doesn't sink like the GP one does.

The pontoons are a lot more forgiving than the GP one. You can still rip one of these off, but it doesn't rip the bottom of the wing off like can happen on the GP PBY.

I've flown about a dozen flights today. At least 10 of the awesome and I won't talk about the other 2. Having the differential thrust does mean that you don't really need the water rudder at all.

Again, for the price, this one isn't perfect, but it does help with the over all fun factor.

Mike
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Old Jul 20, 2011, 05:27 PM
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Having the differential thrust does mean that you don't really need the water rudder at all.


Mike[/QUOTE]

Hi Mike

Differential thrust! I like it. Trying the same on a CL-415 at the moment and have a PBY on order to do the same but having some difficulty! I'm using a DX6i and have gotten it OK with mix1 and mix2 utilised, but every so often, one engine refuses to operate - even when the mix is switched off, so I'm not willing to fly at the moment.
I also used a v tail mixer but that only operated one engine at a time! Not sure what I did wrong but managed to set it up so that at no throttle on the transmitter, one engine was running max and the other not spinning, and at full throttle, the second engine would run full but the first one stop. Good eh??Any ideas?
Luke
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Old Jul 20, 2011, 08:12 PM
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Quote:
Originally Posted by Luke2000 View Post
Having the differential thrust does mean that you don't really need the water rudder at all.


Mike
Hi Mike

Differential thrust! I like it. Trying the same on a CL-415 at the moment and have a PBY on order to do the same but having some difficulty! I'm using a DX6i and have gotten it OK with mix1 and mix2 utilised, but every so often, one engine refuses to operate - even when the mix is switched off, so I'm not willing to fly at the moment.
I also used a v tail mixer but that only operated one engine at a time! Not sure what I did wrong but managed to set it up so that at no throttle on the transmitter, one engine was running max and the other not spinning, and at full throttle, the second engine would run full but the first one stop. Good eh??Any ideas?
Luke[/QUOTE]

Luke

I just followed the instructions on the differential mixing. Look on that thread in this forum I think and someone did describe how to do with with a Spectrum radio.

Sorry, I don't a Spectrum to test with.

Mike
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Old Jul 21, 2011, 10:42 AM
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Orion Pax's Avatar
Shreveport Louisiana
Joined Dec 2006
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Differential Thrust Setup on a DX7

[PROG.MIX1]
THRO -> AUX2 ON
RATE: +100%
0%
SW:ON
OFFSET: -100

[PROG.MIX2]
RUDD -> AUX2 ON
RATE: +25%
RATE: +25%

SW: ON
OFFSET: 0

[PROG.MIX3]
RUDD -> THRO ON
RATE: -25%
RATE: -25%

SW: ON
OFFSET: 0


You can see that you need 3 mixes and I think the DX6i only has 2. You probably wont be successful using Differential Thrust on a DX6i.

Orion

PS. Just in case you want to see another thread based on this plane you should check out the link.
http://www.rcgroups.com/forums/showthread.php?t=1120564
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Old Jul 21, 2011, 12:39 PM
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Hi guys

Thanks for the replies. I got it from Dakrat on another thread (many thanks again Dakrat). Here it is if anyone else needs it:
"On a DX6i, the two mixes I have are as follows:

Mix 1:
Thro -> Flap
Rate D -100% U -100%

Mix 2:
Rudd -> Flap
Rate D +30% U +30%

If you go into the Monitor mode you can see how the mixes affect the channel outputs. The left motor ESC goes into the throttle channel, and the right motor ESC goes into the Flap/Aux channel. This is important; if you plug the ESC's in reverse your differential throttle will be backwards.

The first mix makes the flap channel parallel the throttle channel for throttle control, and the second mix causes the flap channel to vary depending on rudder position. Changing the rate on mix #2 will affect how much differential throttle you get while turning - Season to taste"

What I found also is that when starting up, the sequence needs to be TX on with mix switched on (if it is set switchable in mix 2), then connect the ESCs to the battery. When I do it without the mix on, only 1 motor spins up!

Luke

Oops. Just did a test flight with the new setup. I had the mixing off nut after 2 minutes, the plane refused to turn right and needed full rudder to keep straight. Eventually went into a spin and bang!. So not sure what happened there but I'm suspicious that the differential thrust may have something to do with it.
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Last edited by Luke2000; Jul 21, 2011 at 04:18 PM.
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Old Jul 24, 2011, 08:11 PM
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Ouch, that is too bad.

BTW, the bottom of the HK PBY isn't that strong.

Today, after many flight and 1 hard landing, I was having a great time and a great landing.

Then, she starting sinking very fast. Like it was shot with a torpedo.

When I got it out of the water, there was a 3" diameter hole where the bottom just fell out!

I found the missing piece, but before I glued it back in place, I reinforced the bottom with some balsa. Much stronger now. It was about a 10 minute fix.
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Old Jul 25, 2011, 02:47 PM
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Think I'll do the same with the bottom so.

I noticed earlier that you and Cougar429 were discussing caps and lengthening the ESC cables. I've run the 3 cables to each pod through a "hole" I made in the wings, leaving the ESCs in the fuselage. Should I have twisted the three wires to the motors or sheathed them?

Luke
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Old Jul 25, 2011, 02:47 PM
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Also

How hot do ESCs/motors get? I've been running them for maybe 4 or 5 mins at half and full throttle and I wouldn't go as far as to say that they would cause a skin burn, but the ESCs really are hot, motors also but not quite so hot. Should I have put them in the nacelles and if so, where is the problem with lengthening the battery feed wires? Voltage drop? Couldn't figure the earlier conversation either about capacitors. Could I trouble someone and ask them to explain
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Last edited by Luke2000; Jul 25, 2011 at 03:03 PM.
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Old Jul 25, 2011, 10:06 PM
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Quote:
Originally Posted by Luke2000 View Post
Also

How hot do ESCs/motors get? I've been running them for maybe 4 or 5 mins at half and full throttle and I wouldn't go as far as to say that they would cause a skin burn, but the ESCs really are hot, motors also but not quite so hot. Should I have put them in the nacelles and if so, where is the problem with lengthening the battery feed wires? Voltage drop? Couldn't figure the earlier conversation either about capacitors. Could I trouble someone and ask them to explain
You know, I've never checked at all when it comes to heat. I just fly it.

I didn't add the extra caps. I just mounted the ESC's in the nascels and they have worked fine. This isn't a full 3D type of plane, so I wouldn't worry about it at all for the time being. If you see motor failures, than I would be concerned.
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