Sky_surfer15

HiCan anyone possibly recommend a motor that could replace the stock motor on the Blitz RC Super Sky Surfer by banana hobby? The stock motor is a 1250kv and the flying weight is about 2kg. The propeller description is not displayed. Some forums say that a 1500kv might be nice with a 3S Setup with a 9" prop. and some say that 500 watts is required at least. Can you recommend a good motor upgrade that is close to or if not higher and/or better than the 1250kv I specified taking into consideration the flying weight of 2kg and prop type + ESC? I will be using this plane for FPV soon as it is a huge glider with a wingspan of 2.4m I am trying to keep the power to levels which are more than adequate but keep the plane as light as possible. Can you also recommend me a good battery type as well?Thanks

BMatthews

I'll bite, why do you feel the need to alter the motor?

You say you want to keep the overall model as light as possible. Being an ARF the model weight is pretty much set when you buy it. How much weight for the FPV system are you expecting to add?

There's another way to get more power with the stock or smaller prop, whatever it may be. Just switch to a 4S pack. Then use a wattmeter to check on the power draw. If it threatens to get to high switch to a lower pitch and/or smaller diameter to produce more but a tolerable rise in power over the stock setup. And modifying the motor area to promote some cooling airflow thru the motor to better aid it in dealing with the extra power.

Sky_surfer15

With the 2kg flying weight I plan to add another 2-4 hundred grams, Are there any other motors out there that are better than the stock 1250KV? Honestly Speaking, I dont trust the stock motors that come with planes especially the stock motor on the Super Sky Surfer as there is no brand name type or model.

crashwilson

I to am concerned about the motor that is with this plane. I weighed my Sky surfer this morning with a GoPro&FPV camera with pan&tilt and a 4000 11.1 volt battery in the nose.Not including that heavy wing spar that weighs in at 10 ounces(hoping to find a carbon fiber for it).Anyway this thing weighted over four pounds.put a watt meter to it and the most I can get is 320 to 340 watts at full power.With a 9x5 APC prop. Thought if I went back to a 8x6(like Pete suggested on his build video)I got even less yet. Can somebody with more experience then me with electric stuff help ease my mind on this set up? Thanks craswilson,

BMatthews

To get MORE power from the model you need to load down the motor with bigger props. Your shift from a 9x5 to an 8x6 is actually more or less equivalent for motor load. But the smaller diameter combined with the higher pitch pulls the focus from the climbing aspect and would try to push the model at a faster airspeed when in level flight.

Instead you want to keep the 5 inch pitch and go up to a 10 inch prop if there is room for the bigger diameter.

But if you're getting 330 watts at the wattmeter already that equates to 330/4= 82.5 watts per lb. Which SHOULD BE LOTS! It won't achieve a rocket like climb but it should climb with at a good solid and fairly speedy 45 degree angle without any trouble at all.

A 10oz spar? ! ? ! ? ! What is the rod made from? Even if it's steel I can barely imagine it being that heavy! ! ! !

crashwilson

Thanks BMattews for your quick response to my questions.if I put a 10x5 prop on this motor,your saying that it will not harm the1250kv?I was worried because I thought that you needed 100watts per pound of airplane to fly,and more for aerobatic's. but I still get confused over these motors,ESC's and battery size.I'am afraid of burning up a motor by increasing from stock sugguestion of 3600 and going up to 40003s.I'am just starting FPV and I purchased the starter kit from HobbyPartz. So you can tell I want to set this thing up right.And that wing spar is some kind of composite material and like Pete from Banna hobby said he did'nt know what it is to.(His build video even tells you to try and find a lighter spar)But he also said that the 10ounce wing spar would work fine.With all my GoPro and Sony camera's and a 4000 3s battery and that spar, the plane weight is 5lbs or maybe a tad over. Think she'll Fly???

BMatthews

There is simply no way we NEED 100 watts per lb. That's something that has come about with the new brushless motors and Lipo packs that make reaching this figure so ridiculously easy these days.

Also that 100 watts per lb you read about? That strong a power to weight ratio will produce a near vertical climb on that Super Sky Surfer. Folks that I've managed to convince that they simply do not NEED 100 watts per lb and set their models up for around 70 watts per lb have come back and reported that they are getting a 45 degree climb angle at a good speed.

Back in the early to mid 90's when it was all about brush motors and heavy NiCd packs folks were happy to fly with 40 watts per lb. And 60 to 70 watts per lb was considered a hotrod.

I've got a 6 foot sailplane like old timer and a 2 meter glider that started out in the early 90's with the 05 brushed "can" motors. They flew just fine on a whopping great 38 and 41 watts/lb. They would reach 500'ish feet with about a 90 second motor run. Lazy? Perhaps. And especially so by today's standards. But it was a solid climb angle of around 20 degrees for the old timer and more like 30 degrees with the 2 meter and these models did this reliably for many years.

It's tough to say that the motor will survive or not with the 10 inch prop. If you ground run the setup for a solid minute at full throttle and then shut it down are the motor or battery pack too warm to hold for more than a moment? In the case of the motor the final temperature will take 30 to 40 seconds to be reached as the heat has to conduct out from the armature to the outer bell. So keep testing the temperature for a solid minute after you shut it off. If it's too warm to hold onto steadily then it's likely too warm to try the 10 inch prop. But if it's not at all close to the edge of needing to let go of the motor then you should be just fine with a 10 inch prop.... if it'll fit without carving its own clearance notch in the back of the fuselage....

With a high thrust line like the Sky Surfer pusher design do be careful of what you wish for. Too much power will produce too strong a nose down pitching force and even with the high up thrust angle it may not be able to compensate at the whole speed range. You may find it trying to bury the nose if you're flying at slow speed and jam the throttle to high from off. You'll want to test all of this a good classic 3.5 mistakes high...

crashwilson

O.K BMatthews, I'am convinced thourly that you know way more about this stuff than myself. I will take her out to the club flield and give her a tose!! First I will run it for one minute full throddle and see if she gets hot.(with the 10x5).if it does I'll drop down to the 8x6 and try that.Thank you for your help and I'll let you know the results of the maiden flight.

crashwilson

BMatthews, crashwilson here again and I know I have a problem,I charged a new 3s 4000mah battery,with the 10x5 prop I put my watt meter on and proceeded to run the motor for one minute, after 30seconds(299-300watts full power)the motor started to drop very fast like a dead battery(went down to 100 watts and I shut it off.I checked my battery and each cell, cell 1 was at3.97, cell2 3.4(68%),cell33.9v(66%). I checked the ESC,Battery, and motor and none of them were hot. In fact they were not even warm!!! What do think this could be.I noticed the when I first ran the motor with the 8x6 prop on it, so I don;t think the prop is whats causing this problem.Sorry to keep bugging you, but before I complain to BH I need some advice. Thanks again for your time.

crashwilson

crash is back, This thing puzzles me, I put an 8x6 prop on and then I tried it with a 2200 3s battery, the thing held 255 watts for 1 min, without the motor bogging down like it did with the 3s 4000( these 4000 battery I have are new). So I put the 4000 back in after charging, and the motor did the same thing, started to drop after seconds!!!!!!

BMatthews

What is the "C" rating for the two different packs? If the 4000 pack has a low C rating it might be running out of ability to convert the chemical power storage to actual current. And when that happens the output voltage will sag badly. And that will result in a big drop in watts. But this is a short term sort of thing and the voltage will recover within a couple of seconds after you turn off the motor. The trick is to see what the wattmeter says for voltage while monitoring the watts/power. Or if your wattmeter does not give you the pack voltage put a meter across the pack and monitor the pack voltage along with the watts.

If it's a brand new pack it may also require a couple of cycles to get up to speed. Or if it's really old stock then it may be quite old even though you just bought it. I understand that Lipo packs have a life span of only a couple or three years regardless of being used or not.

stanordave

I have a the 2400mm SSS with DL Tx, 1.3 TX, OSD, Camera, GoPro, CF spar, 1300ma Rx pack, 10,000ma 3s flight pack, landing gear, tailwheel, Dragon Commander Bluetooth module, 80 esc and 10A BEC. With stock motor and an APC 9.6 SF prop, took off at 30% throttle and had zero problems inflight w/power.

What's it weigh? no clue but just over 4#s is probably close. Haven't got any inflight amp draws, etc and won't until the winds die down but the stock motor has enough power.

PS, I don't frequent this thread very often so may not reply for awhile..

crashwilson

I have tried the 4000 3s on the SSS stock motor(ran full throddle for 30 seconds and the motor drops from 275watts to 150)thought it might be the battery so I tried another 4000 3s which by the way have no more than 45 minutes flight time on them.I put them in a cub toghter and they flew it with no problem. So I had a 60amp ESC with a external Ubec and I put it on a Prop Drive motor, with a 40003s.That motor did the same thing.22003s runs both motors without dropping.(all the time I tried this neither motor,esc,or battery got hot!! Could it be you just can't run these electric motors full throddle unless they are in the air???When I put those two 40003s back in my cub and tried to run full throddle, they dropped that motor down to! I would like to put one of those 4000 in this Sky Surfer , I have not flown it yet but I have FPV set up on it and I don't want to lose her on the first flight.I know you don't have to use full throddle on take off so think I should give it a try??I even thought maybe my watt meter is dragging these things down!!