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Old Oct 04, 2012, 02:14 PM
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San Diego, CA
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I swapped out the stock motor and ESC for a new 3640-3900KV motor and 60A Hobbywing ESC last night. For luck, I hung a 3-blade 8x6 EMP propeller on it. And found that that combination totally overwhelmed the old Turnigy 3s 2200mAh battery I had been using. Spun it up slowly, and as I went to full throttle, voltage sagged down to like 7.5 volts, and current draw went briefly to 80 Amps (!!). The ESC got pretty hot in like 4 seconds, and I shut it down. Tried a single 2s 5000mAh GensAce battery (nominal 7.4V) from an R/C car, and voltage dropped to 6.8V and stayed there as current draw went to a fairly steady 75 Amps. Holy shiite.

Clearly that is far too much propeller for that motor, at least at the low voltages applied. Specs for the motor say it can handle a 4s LiPo battery. Haven't had time to rig the two-plug harness I will use for putting two of those R/C car batteries in series, so I didn't get a chance to try a 4s equivalent for 14.8V. If it doesn't spin up that propeller to MUCH higher speeds with 14.8V, I may have to go for a larger motor for the same prop. After all, I have a 3-blade 9x7 on order!

The plane is limited to a 9" prop, of course, if you don't modify the motor mount to raise the motor. So anyone who wants more thrust, must either turn it faster or use 3 blades instead of two. Or combinations thereof. It worked great on my regular SkySurfer and Easystar, with 2835-3900KV motors and 3-blade 6x4 Master Airscrew props. Jury's still out on this SSS setup, though, at least until I can get a solid 14.8V to it. I've noticed that most motors capable of 14.8V, draw less current with that, than when they are used with 11.1V.

To my surprise, the cross-shaped aluminum motor mount that came with the stock outrunner motor, fit the new 3640 inrunner motor perfectly (after a little filing to clear the cables). Even the old screws fit the thread of the holes in the new motor. So I was able to simply mount it exactly where the old motor had been, it literally bolted in.
_________________________________

See the Technical Info/FAQ page for the Super Sky Surfer at http://www.rcgroups.com/forums/showt...6#post22886340
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Old Oct 04, 2012, 02:48 PM
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Quote:
Originally Posted by Little-Acorn View Post
I swapped out the stock motor and ESC for a new 3640-3900KV motor and 60A Hobbywing ESC last night. For luck, I hung a 3-blade 8x6 EMP propeller on it. And found that that combination totally overwhelmed the old Turnigy 3s 2200mAh battery I had been using. Spun it up slowly, and as I went to full throttle, voltage sagged down to like 7.5 volts, and current draw went briefly to 80 Amps (!!). l]
It sounds like you are pretty much shooting in the dark without much in the way of engineering or analysis. What made you think you could run that prop on a 3900 kv motor?
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Old Oct 04, 2012, 02:54 PM
Argue for your limitations
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Lincoln, CA
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Originally Posted by kaptondave View Post
Here are a couple of other options. The Nanotechs are great batteries, and these are in stock in the US warehouse near Seattle.

http://www.hobbyking.com/hobbyking/s...dProduct=20551

http://www.hobbyking.com/hobbyking/s...dProduct=20737
Those won't work very well, if at all. Those are 2 cell batts.
AJ
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Old Oct 04, 2012, 02:58 PM
Argue for your limitations
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Lincoln, CA
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Originally Posted by kaptondave View Post
It sounds like you are pretty much shooting in the dark without much in the way of engineering or analysis. What made you think you could run that prop on a 3900 kv motor?
+1. He must not have a wattmeter. Or, he doesn't know how to use one??. I have that same motor and a 5x5 is about the max that I can use.
AJ
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Old Oct 04, 2012, 03:09 PM
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Originally Posted by ajbaker View Post
+1. He must not have a wattmeter. Or, he doesn't know how to use one??. I have that same motor and a 5x5 is about the max that I can use.
AJ
I'm turning a 6x4 3-blade prop at 21,000 RPM with a 2835-3900KV motor on 3s on my regular SkySurfer (and on an Easystar).

I was hoping the results would "scale up".

When I see what this 3640-3900KV does on 14.8V, I'll know if I guessed right.

Without any charts of power curves for any of these motors, or wind-tunnel data for the props, guessing is about all I can do.

As I've said, you never know till you try.
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Old Oct 04, 2012, 03:40 PM
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My rule of thum ( my brother taught) is the higher the Kv's "usually" , the smaller the prop. Well, it was kinda expounded by AJ on the Anx/ clouds fly thread...
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Old Oct 04, 2012, 03:40 PM
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Originally Posted by Little-Acorn View Post
I just swapped out the motor and ESC on mine, and am now looking to put two 2s 5000mAh GensAce LiPos in series, into the nose of my SSS. The two 3s 2200mAh's I had in there, barely fit (and the plane was still tailheavy), I'm sure I'll have to do some carving to get the bigguns in.
Will it fly under 2s power?

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Originally Posted by Little-Acorn View Post
Have you checked out www.hobbypartz.com for LiPos? I like their quality and their prices, and they have a great variety (alas some out of stock at times). And if you order $50 or more, shipping is free.
Considered it, but.. I hemmed and hawed all through Wed.. which is the cutoff for ordering from Nitro if you want it delivered in the same week.

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Originally Posted by Little-Acorn View Post
You're welcome.
I got lucky when I did that, two hours flat from San Diego to Irwindale, ZERO traffic jams, don't ask me why.
Nice lol.. not sure how you pulled that one off. Just lucky I guess.

I'm 28 miles away, but.. i'm on the west side of downtown LA. When I add up all the junctions..it's a scary thought. 110/10, 10/5, 10/605 between 1:30 and 3:30 on a Friday...

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BTW, after you turn from Irwindale Rd. onto Tapia St., go to the third driveway on your right. BH's building is right there on the corner. (Google Maps marks it wrong.) No sign, but the address number is above the door... and behind a tree.

And when you pick it up, check to see if there are four bolts for each control horn (if you get an ARF). Every control horn in mine, was packaged with only three bolts. Not a big deal, but as long as you are there....
Thanks for the heads up! I need this trip to go as quickly as possible lol!
My ARF also came with the decals not applied, which is actually how I prefer it. I think the pure-white plane is gorgeous. Decals were on their separate sheet, in the box. If you want, maybe ask them if they have another like that.

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Originally Posted by Little-Acorn View Post
I'm planning to mount a #16 keychain cam on two servos (the one for panning is a 180-degree servo from HobbyKing), with the camera poking up inside that big canopy. Might even hinge the canopy. I believe it'll fit... but you never know till you try.


Kewel. Break a leg!
wow. I need to pick up one of those.. running either a crappy cmos, or a 600tvl(if I get around to doing some wiring) this weekend.

Hoping to fly just off the coast of Vandenberg at Surf Beach.. if you hear about some RC modeler who got his plane shot down by the military next week.. that was me.

J/k lol... if there's a problem, I'm sure i'll never even get it launched. You can't see THEM, but.. they are definitely watching you at that beach. By the time you can get your dog down to the water.. you'll have a MP standing next to you. Damned Snowy Plover..
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Old Oct 04, 2012, 04:03 PM
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Originally Posted by shutterspeed View Post
Will it fly under 2s power?
Wow, I really doubt it. Remember the restriction on prop size - anything over 9" diameter will hit the fuselage unless you raise the motor somehow. I just tried a 2s 5000mAh battery to see if there was something wrong with the new motor, see whether it was soaking up all available power plus more. It didn't, quite. I would have tried two of them in series, as I said, but I didn't have the harness made up and it was 11:00 at night.

Quote:
Hoping to fly just off the coast of Vandenberg at Surf Beach.. if you hear about some RC modeler who got his plane shot down by the military next week.. that was me.

J/k lol... if there's a problem, I'm sure i'll never even get it launched. You can't see THEM, but.. they are definitely watching you at that beach. By the time you can get your dog down to the water.. you'll have a MP standing next to you. Damned Snowy Plover..
I hear that.

After 9/11/2001, recall that all flying was prohibited. Don't know if models were included, but nobody around here wanted to find out.

Then some 3 weeks (I think) after The Day, I heard on the radio that flying was finally permitted again. I went down the the ultralight field at Barona (R.I.P.) and found a bunch of the guys who had heard the same thing. Some had already flown to Lake Wohlford and back for breakfast.

As I was preflighting the Minimax, a police helicopter appeared, and landed at the field, raising a huge cloud of dust. The cop got out and spoke to us, asking if anyone had been flying. We told our stories, and the cop pointed out that flying was permitted for commercial aircraft ONLY, with individual positive control every step of the way, required - basically IFR all the way though it was a clear, sunny day.

The reason the cops had come to our ultralight field, is because an ***Aegis cruiser*** patrolling off the coast of California had detected the ultralights going to Wohlford on its megawatt phased-array radar, and had been tracking them every minute with their combat systems, with all guns and missiles trained out and hot. But they figured that these targets might be ultralights who weren't receiving the demands and orders being broadcast on SoCal Control, or even model airplanes, due to their small signature and low speeds, and so held fire and asked the local cops to check it out instead.

Whew......

(not kidding)
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Old Oct 04, 2012, 04:12 PM
Argue for your limitations
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Lincoln, CA
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Why wattmeters are necessary

Quote:
Originally Posted by Little-Acorn View Post
I'm turning a 6x4 3-blade prop at 21,000 RPM with a 2835-3900KV motor on 3s on my regular SkySurfer (and on an Easystar).

I was hoping the results would "scale up".

When I see what this 3640-3900KV does on 14.8V, I'll know if I guessed right.

Without any charts of power curves for any of these motors, or wind-tunnel data for the props, guessing is about all I can do.

As I've said, you never know till you try.
Everyone that understands power trains does not "try". All of us use a wattmeter. Better to know before burning up motors, ESC's, LiPo's. Even if you do "try", you can do a great deal of damage without knowing it. If I change even one size of prop, I Always use a wattmeter to "know" for a certainty what the electronic results are. Guessing is a very bad practice unless, of course, you don't change any of the stock parts.
AJ
Case in point->
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Old Oct 04, 2012, 04:23 PM
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beating the drum (again)

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Originally Posted by G-LO View Post
My rule of thum ( my brother taught) is the higher the Kv's "usually" , the smaller the prop. Well, it was kinda expounded by AJ on the Anx/ clouds fly thread...
I believe that is "generally" true (of course, someone will find an exception). The starting point is the max wattage rating of the motor. Utimately, we all are slaves to Ohm's law. If we violate it, bad things WILL happen. IMHO, anyone who changes a Prop, LiPo, ESC, Motor would be well advised to use a wattmeter to see the results.
BTW-Please tell me that you have one?
AJ
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Old Oct 04, 2012, 04:36 PM
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Originally Posted by ajbaker View Post
Everyone that understands power trains does not "try".
Everyone?

Quote:
All of us use a wattmeter.
(sigh)
http://www.rcgroups.com/forums/showt...2#post22912887

Quote:
Even if you do "try", you can do a great deal of damage without knowing it.
I can do that just by pushing a transmitter stick the wrong way. And not necessarily the throttle stick. Or button, back in my day. I've done it before, more times than I like to remember. I suspect I'm not alone, too... right?

But, you know, it's a hobby, remember? We're allowed to screw around and try stuff.

Chill, dude! Let people have some fun....
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Old Oct 04, 2012, 04:57 PM
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Lincoln, CA
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Maiden - Soon

Well, I finished the beast last night. It is RTF. I ended up using a 4000mah LiPo (3600mah was recommended). I could fly it today. But, my wife is out of town and she INSISTED that she come along for the maiden. Of course, that means she is going to bring her plane (Sky Surfer V2) and fly with me.
Besides, I like to have a time/dated picture of the SSS to verify exactly when it was built, that I really own one, and that I have NOT flown one yet. So, any posts that I put up earlier should be run through that filter in case they sound like gospel truth. The only one that I can think of is my 2S LiPo posting earlier. I really have NO idea if the plane will fly on a 2S. A couple of things come from experience and other folks (you guys) opinions/experiences. i.e. generally, most of you are saying that the stock stuff is adequate to fly this plane. Well, given that actual experience, I doubt that the SSS will fly on a 2S for 2 reasons.
1. It simply does not have enough power to drive the stock prop fast enough for sustained flight.
2. The size prop that would be required to fly it would be at a minimum a 10x8 (motocalc) - which won't clear the fuselage.
Still, that is all theory. As always, I reserve the right to be wrong and I look forward to seeing someone fly this 4lb.+ plane on a 2S. Oh. BTW - mine is exactly 5 lbs. 0 oz. I had to use 4.9 oz. of ballast to be able to get the 100mm CG. After the first flights, I will get rid of the ballast and put in a gyro, Then, the CG range will be about 100mm to 175mm from LE. You guys that have used gyros know what is going on with them.
Wish me luck on my maiden (This Sat. morning-I hope). Of course, I WILL have a video to share whenever it is maidened.
AJ
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Old Oct 04, 2012, 05:05 PM
Argue for your limitations
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Originally Posted by Little-Acorn View Post
Everyone?


(sigh)
http://www.rcgroups.com/forums/showt...2#post22912887


I can do that just by pushing a transmitter stick the wrong way. And not necessarily the throttle stick. Or button, back in my day. I've done it before, more times than I like to remember. I suspect I'm not alone, too... right?

But, you know, it's a hobby, remember? We're allowed to screw around and try stuff.

Chill, dude! Let people have some fun....
Everyone? YES. You need to read the rest of the sentence - "that understands power trains". The folks that don't may not use/own a wattmeter. I am pleased that you have one. Your recent posts suggest that you do not own one or do not use it. Your posts might be clearer.
As far as bumping the throttle inadvertenly, I had always thought that I was the king in that department. I rewired all of my transmitters to have an on/off switch. Since then, I have not had even one accidental motor start. Oh, BTW. the Turnigy 9x has a way to use an existing switch for a motor on/off. If anyone has one and wants the instructions on how to program it, ask me (it is not immediately obvious how to do it.)

I agree. If you are rich or don't care, you can have fun to your hearts desire. I just have a problem with suggesting that other readers can "try" things without mentioning that there could be unfavorable consequences.
AJ
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Old Oct 04, 2012, 05:05 PM
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Originally Posted by Little-Acorn View Post
Everyone?

But, you know, it's a hobby, remember? We're allowed to screw around and try stuff.

Chill, dude! Let people have some fun....
Let's practice some basic common sense and safety precautions while we are having fun. Reckless actions get people hurt, or cause fires that sometime result is getting model flying fields shut down as happened recently in the Ojai area.

And you are using your Technical Info and FAQs page to advise newcomers on how to build and modify the SSS? I hope you include a link to Post #931 to show what NOT to do.
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Old Oct 04, 2012, 05:44 PM
Argue for your limitations
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Lincoln, CA
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Originally Posted by kaptondave View Post
Let's practice some basic common sense and safety precautions while we are having fun. Reckless actions get people hurt, or cause fires that sometime result is getting model flying fields shut down as happened recently in the Ojai area.

And you are using your Technical Info and FAQs page to advise newcomers on how to build and modify the SSS? I hope you include a link to Post #931 to show what NOT to do.
+1. Well said.
AJ
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