Hi All

I was wanting some advice on propellers and have couple of queries:

1) I have a grey 11 x 6 prop made of plastic (of some composite description I don't know). I was wanting to get the tips painted as the propeller is invisible when in operation and I tend to think a danger you can't see is a bit of a danger! Can anyone tell me how to go about painting the tips (simple enough)? That is, what paint to use (cheapest preferrably) and application? Is paper white out suitable? If so this would be practical as I could probably nab some from the office rather than having to buy a tin of something that I am only going to use a tea spoon of. Obvious criteria is something that will stick and isn't going to comprimise the integrity of the prop itself (that is weaken).

Also is the weight of the paint enough to significantly alter the balance if you just do the ends?

2) How critical is prop balancing, and what is the best way to go about it? The hobby shop rep showed me a $A50 dollar prop balancer, but I really can't justify spending this kind of money to balance a prop that is only worth only a few dollars. For that price I could buy probably 10 props and most likely a couple would be perfectly balanced straight from the factory.

There is a cheap finger tip balancer but he (the shop assistant) said it isn't effective. But perhaps there is some tricks to getting some reasonable results out of these cheaper ones? The store person said something about setting it up on a couple of old rasor blades but I am not sure exactly what setup he is proposing. Can anyone advise further? Perhaps this finger tip balancer isn't ideal but it should provide an indication if the prop is out of whack. My existing one may already be out because looks like one end has hit the runway with a hard landing.

Then, once you have identifed whether or not its balanced, how do you recommend balancing it? I have heard some comments about sanding down the heavier end, but I would find this a hassle. I have read another comment about simply sticking tape on the lighter end.

Experts please weigh in!!!

Thanks in advance...

Da Meister!!!

I paint my tips then balance....you aren't buying a 50 buck prop balancer for the prop....your buying a 50 buck prop balancer to protect your engine....
I rough up a 1/2 inch or so of prop tip with sand paper, clean with alcohol, and let dry. tape off the edge...prime using Krylon primer, once dry I paint it yellow using Krylon...once that is dry a clear coat using once again Krylon clear.. light coats are the way to go to keep paint from leetching under the tape....
when I balance I sand the trailing edge of the heavy blade....you don't have to buy a 50 dollar balancer the finger one will due.....or perhaps you can find something around the office to hold the prop but will still rotate in your hand......I'll let someone else tell you about balancing the prop hub

I use the paint on the tips to balance the prop, more coats on the lighter tip, this kills two birds with one stone, so to speak.

If you have an expensive prop balancer, you are going to notice the hub of the prop is out of balance also

I have read some posts about this topic, some guys stated that balance is not that critical on small props (less than 13" I guess) but I think you can always try to balance them as much as you can without spending lots of money... here is a post about how to make a good magnetic balancer

http://www.rcuniverse.com/forum/m_8522036/tm.htm

I hope it helps

If you use scotch tape to mask the tips with, the paint will not leach up under the tape. Masking tape is basically paper, and can soak up paint if not applied correctly.

when I paint prop tips I just make a mark where the painted part ends on the prop so you have equal sized tips.

then I do the dip and spin, dip the prop in the paint,to the line,give it a little shake, do the other side, I like using the small can 1/2 pint size of De-Rust-O because it is resistant to fuel, and spin it lightly, out where some drops of paint can fly off harmlessly, then let it sit to dry.

you don't need to spin it hard just enough to get the extra paint off the ends, if you messure acurately its surprising how little the paint afects the balance of the prop after first checking the balance and then dipping the tips the balance was still right on,spinning the tips helps keep the weight even.

if you were to brush on something like liquid paper, which I don't know if its fuel proof or not, your going to get inconsistant ammounts of material and I would want to check the balance of the prop.

a note I hardly ever check the balance of my props if there smaller than 14" I will when there new and leave it at that,the only other time is when I have a prop strike and have nicked one side so I could reuse the prop I make sure its balanced out before using it again in a pinch.

I've got the Dubro Tru-Spin Prop Balancer http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD712 $32 that helps an engine run smoother, with less vibration and ultimately could save your plane. So they tell us. When I was flying rubber powered Free Flight and making my own props, it was imperative to have a balanced prop in order to get as much efficiency out of the prop. What I notice about using the Dubro balancer is that it can almost drive you nuts because it will show the smallest out of balance condition. Heavy blade or heavy hub. Sometimes I wonder if just the house HVAC system with the slight movement of air is affecting the process. So I've come to the conclusion there is a point where with any prop, I get to a point that I have to accept. Some props are easier than others.

My method. First determine which blade is heavier and which side of the hub is heavier. Use a sharpie to mark them. Test to see if you've really identified them correctly. Then I like to take some 100 grit sandpaper and start going over the whole prop. They're too sharp right from the manufacturer. Check to see if the heavier blade still shows, if it does, I will just take the light end and dip into a jar of butyrate dope. Making sure it dries uniformly, by turning it so drips and runs don't happen. Sometimes this step can take up to 3 tries, but if you make that blade too heavy, then sanding should even it out. The next thing that usually shows is one side of the hub is heavier, this one seems to be harder to correct. I'll try sanding the heavier side, especially if there is any seam from the mold that I can remove, but sometimes it takes adding some weight to the lighter side. I use a nice glob of 5 min epoxy on the lighter side, again watching that it doesn't run. Later if too much has been added, I will then sand some off. A balanced prop should hold 10:00, 2:00, 4:00 and 8:00, without dropping a particular side. Whew! And to think I could break it on the first flight. Seems that the more props I do, the better I get at it. I know when to quit and go on to the next prop. Once balanced, I like to wrap in syran wrap or plastic so that in my extra Prop bag, I know which have been balanced.

Hi All

Thanks for your feedback so far. My prop is 11 x 6 - what do these numbers mean? I assume the first number is the length? So for this size prop balancing isn't quite so imperative?

First number is the Diameter, the second number is the Pitch.

Can someone explain how one knows if the blade is heavier or if it's the hub?

Jack

the prop will always balance with both blades horizontal, but with the same side of the hub always down, one side of the hub is heavier

if you can put a prop horizontal, both sides of the hub, you're close to balanced

I just balanced a wood prop last night using shiny clear coat spray for wood. A couple little spritzes and it was done.

yeah, sometimes I get lucky. Just a good cleanup with some sandpaper and that's all I need. About 25% of the time I'm guessing.

I feel all props should be checked for imbalance. Some people have a certain size, above which they feel they should be balanced. It takes so little effort to do, I just go ahead and check them all. I really don't pay attention to the hub as it is so close to center, I feel the imbalance here is negligible, unless really out of whack. How are you guys balancing the hub, you certainly do not want to remove materail?

Oh Geez, what was I thinking!

Thanks!

jack

I think APC props have a groove on the back of the hub. You could paint on fingernail polish like some do, a dab of epoxy, dab of ca, and it would not effect the way the hub fits against the engine plate. I am like you though, I just balance the blades.

I balance all my props. Fine sand paper to the back side of the heavy end so I don't scuff the most visible parts. My Hobby shop sells paint pens. Just about any color for a couple bucks. Paint first, let dry, then balance. It may seem like minor engine vibration, but it keeps some things from comming loose.

I'll try to sand the hub between the blades, the side that is heavier. I've never had a prop failure at the hub, always a blade break. But if it doesn't seem to be improving I'll just add a good size glob of 5 minute epoxy to the light side. By adding material, you can sand if you added too much. The way the Dubro Tru-Spin Prop Balance is designed, it has extremely low friction so the heavy side is always detected.

the hub has to be checked. we've all seen props with off centered holes, and with that it will cause undue vibration.

I have not found many hubs where the hole was off center. I visually check the hole location when I buy and like I said I balance every prop.

Jet60, Next time I will quote you, so you will not be able to retract your FLAMING posts!

wow, sorry i even posted.