bgfireman

My Feedback: (13)

I have a mini ultra stick with a E-Flite 40A ESC, a great planes rimfire 28-30-950, a Thunder Power 3s Lipo, with a 10 X 4.75 slow fly prop on it. Would it mess anything up to put a 10 X 7 Elec. prop on it. It has to run almost wide open to stay airborn. I was wondering if a different prop size would help or hurt.
Thanks for any advice.
Alan

Matt Kirsch

My Feedback: (21)

Before you do that, we need to take a couple of things into consideration.

First, on a plane this size, I'd really recommend an APC Thin-Electric prop, not a slo flyer. Thin-Es are much more robust, and you're pushing the limits on RPMs with the slo fly prop anyway.

The motor has a limit as to how many Amps it can comfortably handle. In this case, that's 20A. Your ESC is good to go, but is your battery? "3S Thunderpower" could be any of several batteries, some that will work, some that will be overloaded. 2000-2250mAh is a good size for a plane this size.

Do you know how many Amps your current setup is drawing? If it's near 20A now, then a bigger prop will overload it. I'm confident that you aren't anywhere near 20A right now just by the fact that you're running full throttle to keep this plane in the air. Still you need to be careful to avoid overloading the motor or battery.

It's going to be borderline even with a bigger prop. The motor you're using is actually meant to power much smaller airplanes. Maximum input is only 155W, much of which will be going into making heat instead of thrust. You're trying to fly a ~25oz airplane on about 100W of useful power, and the motor won't last long running at full capacity like that

Dr Kiwi

May I suggest you take a look here: http://www.rcgroups.com/forums/showthread.php?t=739722

You'll see that a 10x6 GWS HD is good on the 28-30-950. That 10x4.7 APC SF is pushing the limits of continuous operation (14A). I fear a 10x7 APC E might be too much.

As Matt says - you really need a bigger motor for an aircraft this size - something which can manage 200W-250W comfortably would be better than thrashing a 120W-140W motor. The 35-30-1250 (which is only 17g heavier) with a 10x6 GWS HD gets you:

10.7v, 23.60A, 251W, 9540rpm, 54.2mph, 1226g, 43.17oz, 4.88g/W

A 10x7 APC E only gets you an ounce more thrust at 6mph higher pitch speed, but needs an extra 65W (25% more) to get it for you! [28.4A/316W]

bgfireman

My Feedback: (13)

So I quess what I am hearing is I need a bigger motor? I am thinking about the E-Flite park 480 brushless. How does the miliamps of a battery affect my set up? I thought that was like a gas tank on a gas burner. It holds a certain amount of flight time. Please keep it simple with your teminology. I like the KISS method. I have no idea how many amps I am drawing. I don't have a amp meter. What is a good inexpensive one.

patnchris

Keeping it simple.....If you put a Park 480 on the MUS you will have plenty of motor and ESC. I have this plane and have flown it with the Park 480 and thePark 450. I find it plenty fast with plenty of power with the Park 450 running a Thunderpower 3s 2100 15C battery. I've used both a APC 10X7 Slo Flyer and the APC 10X7 thin electric. The Slo-Flyer draws a little more juice, but not enough to give you problems. There are those people that will tell you you need more power. If you're one of them, The Park 480 is for you. The Park 480 will give you more power than you know what to do with and will easilly spin an 11X7 Slo-Flyer. I have even spun a 12X6 on a couple of my other planes. Your ESC is way over kill, so no problems there. Running the PArk 480, the weak link will be your batteries. You will need a 20C battery or better (Like the ThunderPower Extreme) I'm assuming that if you chose to fly the 480 that you will be flying it close to the point where the wing would yield and therefore you would definately be over amping the 3S 2100 Pro Lite.....Pat

bgfireman

My Feedback: (13)

I don't know that I will be flying it wide open all the time, but will it cause a problem if it is only a 16c, 910 Mah battery? I thought it would just have less flight time. I read some where on here that if you had a bigger motor and ESC you could run at less throttle and have more flight time. Would this be correct? As I can't afford a motor and battery, which would be of more importance?
Thanks for all the help. Alan

patnchris

That battery is way too small. I'm now flying mine with the Park 450 and using a 1320 ma. A 10 minute flight will suck it dry, and that is using a LOT of throttle management. I'm not sure that little battery will even run a Park 480

bgfireman

My Feedback: (13)

Well I went out and bought the 450 today. It was all they had in the hobby shop. It is the 890 Kv version if that makes a difference.
I have a 1500Mah/11.1v/15c battery on the way. Do you think this will be ok with a 10x7E APC prop. I had it all hooked up tonight and it will spin the prop good enough to try and lift the tail with my 910Mah battery.
Thanks for all the help.
Alan

patnchris

That set up will work fine with throttle management.....You will be able to do bursts at wide open and sustain it for a couple of minutes, then back off and let it cool for a few.....I usually fly several circuits at higher throttle and do my loops and rolls, etc. then fly several circuits at 1/2 or less.....This will get you 10 minutes and still have a little in reserve for landing.....Start slowly, at first using high throttle to take off and then 1/2 throttle for 10 min. Then check your battery temp....Warm to the touch is ok.....Hot is bad....Very bad!!!.......After a few flights at increasing throttle settings, you will be able to gage how much high throttle can be tolerated. It sounds like this will be a new adventure for you, so I'll give you a little friendly advice...Put Velcro on the bottom on the battery tray and glue the other half to the battery. Also use the supplied strap....Both are necessary. Check the screw protrusion of the motor mounting screws...If they stick out past the end on the T-nut, trim tem off flush. These two items will keep you from destroying a battery on a less than perfect landing. The velcro on the battery tray will help keep the battery from sliding back and forth and trimming the screws off will insure that if the battery should slide, the protruding screws won't punch a hole in it....Position the battery as far as possible for your first flights. This will generate a slightly nose heavy condition (very desirable for first flights) as you gain more experience you can start to move it rearward adjusting the CG. Slightly nose heavy will make the plane easier to fly, especially if you're flying at reduced control surface rates. As you get better and feel more comfortable start moving the battery rearward. You will fnd the aerobatic abilities increase exponentially as the CG (battery position) moves to the rear...Lastly, have fun with it. If you crash resist the urge to buy replacement parts . If you can't repair it, possibly seek help from someone who can help....If the broken parts are too far gone for repair. Consider buying a whole new plane. It is only around $70 vs $45 for a fuselage, or $39 for a wing...Use the parts you need and keep the rest for spares.....I don't think you need to ask me how I know this stuff....LOL.....Pat

bgfireman

My Feedback: (13)

Yeah been there done that too!!! I have flown nitro in the past. This is however my first adventure in Elec. I love how easy it is to clean up when I am through. The only thing I don't like is how long it takes to charge batteries.
Thanks for all of your advice.
Alan

bgfireman

My Feedback: (13)

I put the 450 outrunner on my MUS on Thursday. I got to fly it today. I flew it for about 5 minutes with only using 475Mahs. I think that is pretty good on a 910mah battery. I flew it at about 1/3 throttle. The battery lasted longer with a 10x7E than with a 10x4.5sf. I like the 10x7E better than the other.

Dr Kiwi

Yes, you will find that APC SF props suck a LOT of amps, and with poor pitch speed, I'll bet you had to have the throttle wider open with the 10x4.7 SF than with the 10x7 E. I would be concerned that you are going to be pushing that 910mAh pack way too hard. Capacity (mAh) IS important in obtaining decent amp draw and current flow - a 10C 910mAh pack is only good for 9.1A max - if you motor WANTS to draw more than that (say 12-15A) you are in trouble - a 10C 2100 is capable of 21A, so if you need 12-15A for example, it will deliver that easily.

An E-flite 450 is rated at 14A continuous/18A burst, so you may well not be getting the most out of it with that tiny pack. I see that you were only using 1/3 throttle so that is why you are okay - but if you go to WOT with a 10x7 E I'll bet the voltage under load will drop so far that you'll hit LVC very quickly.

bgfireman

My Feedback: (13)

I got a 1500Mah 15C pack in today for my mus. Do you think that will be good? I could run the 910Mah 16C wot for take off and a couple of times in vertical flight, but I never pushed it far.
Thanks Alan (Still learning this elec. stuff)

Dr Kiwi

Now you are talking: with the potential capability of delivering 22.5A, that pack is going to be very happy when you ask it for only 15A or so! Rule of thumb says draw only 80% of continuous current capability, for only 80% of the pack capacity, and you'll get far better life from your Lipo's.