I know there's been a million threads on prop balancing, but I always question whether I'm doing it right (also the search just keeps hanging). So, I thought I'd post and see if somebody can confirm or correct my method.

I usually use clear nail polish on the light end of the prop. My question is, should I be applying the nail polish to the tip or base of the blade? The back or the face? Also, which is which? I can never seem to remember.

Another related question while we're talking props. I have an electric plane that I bought a master airscrew k-series prop for. Is there going to be an issue with using the k-series on an electric? If I remember correct, isn't it the other way around? Using an electric prop on an ICE is bad? Just want to be safe.

Thanks for the help.

The back is always the concave part.

Another ? if you don't mind. When sanding I have heard to sand the back. Is this correct? It doesn't seem right because that is the side that bites the air.

I use a spray can of clear polyurethane and spray the lite blade. if I get a little to much I just sand a little off.


Buzz.

When balancing a prop I think sanding the front or back is irrelevant as long as balance is the important factor. I would not add more weight to the opposite side as the whole objective is efficiency.

I appreciate the answers I've gotten so far, but I still have a few unanswered, so I'm bumping this thread.

I'm no expert. I will take a stab at ? 1 and 2 as well.

If a lot of weight is needed applying it out at the tip is going to mean a lot more per gram. It probably doesn't matter , but I also agree with jw to remove weight rather than add it. I have taken the approach that IF I had to write on my prop I would add weight with a marker , but if not then I will sand weight off. I imagine it is so insignificant that it doesn't matter. Also my ? isn't really answered either , but jw is probably right about that as well. It may not matter. I was concerned about roughing up the biting face of the prop.

sorry I can't even guess about the other ? you have. Again, I'm no expert, but the few props I've worked with have me convinced that getting the prop on straight without runout is as important if not more important than the actual balance. Some of mine aren't too good though. The cheap models I have are poor quality.

I used to remove material, but I read in a number of places that it's better to add material because removing material can affect the structural integrity of the blade. Whether I'd be removing enough material to make that true, I don't know, but I figured better safe than sorry. As far as efficiency goes, I'm not sure if that's exactly what I'm trying to get out of a balanced prop. I usually do it as a preventative measure to keep the prop from vibrating the airframe or destroying motor bearings. I've never had any of those things happen, but then again, I've always balanced my props in one way or another.

If you just sand the the finish off until the prop balances there is no structural issues. However, if you find yourself sandind the blade down then maybe it's time to switch brands. Xoar is an awesome prop that requires little to no balancing. Yes, you will pay more however it means more airtime and less time on the ground.

Do you sand the face or the back when you balance your props? Also, what grit sand paper do you usually use.

I found a decent answer to my k-series prop question. It's perfectly alright to use k-series props on electric motors, but because of their weight it's recommended that you reprogram the esc for a soft start.

Generally I'll sand the back with 100 grit. Then if necessary I'll sand the front till it's balanced.

Running an IC prop on electric is perfectly safe (as long as you stay within its rev limit) but IC props have to be much stronger to withstand the huge torque changes as the engine fires so the inner 1/3 of the blade is a bit thicker (and thus heavier) than aerodynamically necessary.
An electric motor on the other hand provides an almost constant torque so the prop can be designed to better suite aerodynamic needs.

So when running an IC prop on electric it will work fine but some of the precious electric is being wasted. A suitable e prop will generate the same thrust but require a bit less current to do it

"Slow fly" props take this even further with very thin blades and very small bosses. Still more efficient but fragile and strictly rev limited.

Personally I always sand the front face of a prop to balance it but only at the tip and make sure I keep the blade profile.
If required it is always possible to restore the origianl surface finish with progressively finer 'wet and dry' sand papers.

I run Xoar on my EF Extra 300 and I have to say that it's a very conservative prop. I'm running 8s5000 packs with a Castle Ice 100 on a 320kv. motor swinging an 18X8 Xoar. 1649watts@50amps and comes down cold. Vertical is more than enough.

Normally I do use e props on my electrics, but this plane is quite a bit larger than my others, and my LHS didn't carry large enough e props, so I settled for an IC prop. I may order some large e props online at some point if the need arises.

On a somewhat related note, I was having a bear of a time trying to balance this particular prop. After rebalancing the blades like three times, I finally figured out that the blades are actually fairly well balanced, and that the hub was the out of balance culprit. I think this is the first time I've ever had to balance the hub of a prop. I have it pretty well balanced now, so all that's left is to throw it on the plane and test it out.

Never had that happen before. Glade you found it.[8D]

I try not to deal with my LHS because I found that I could get the same battery online for $5 and he was charging $23.