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Author Topic: Balancing props  (Read 1503 times)

Offline Allan Perret

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Balancing props
« on: February 23, 2009, 03:32:15 PM »
What do you think about this?
Instead of sanding on the heavy side, spray coats of clear lacquer to add weight on the light side.  I've done this only with wood props so far, but think it would work on other materials also.
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Allan Perret
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Slidell, Louisiana

Offline Brett Buck

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Re: Balancing props
« Reply #1 on: February 23, 2009, 09:11:19 PM »
Quote from: Allan Perret on February 23, 2009, 03:32:15 PM
What do you think about this?
Instead of sanding on the heavy side, spray coats of clear lacquer to add weight on the light side.  I've done this only with wood props so far, but think it would work on other materials also.

     It works, and I have done it, but it only works when it's already very close, and, if you use dope/lacquer you have to wait about a week to see how it turned out!

     I finish wood props with thin Hot Stuff - it gasses off to final weight in minutes, and makes for a very good finish. It's adequately fuel-proof.

     Brett
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Offline Robert Zambelli

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Re: Balancing props
« Reply #2 on: February 23, 2009, 09:19:53 PM »
I've used Brett's method and it works perfectly.
But, here's something to consider. When properly balanced, a propeller will remain stationary at any position (I use one of those magnetic balancers). I have gotten props to where they balance perfectly with the blades horizontal. Then, when placed vertically, they will flop to a horizontal position. In most cases, it's due to an off-center hole.

Bob Z.
« Last Edit: February 24, 2009, 04:27:52 AM by Robert Zambelli »
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Offline Steve Helmick

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Re: Balancing props
« Reply #3 on: February 23, 2009, 09:22:22 PM »
I've got doubts about a lacquer working over whatever Zinger uses. It is very gummy stuff, even on props that have been drying in my basement for a year or more. I wish they would leave them bare, actually. It seems to me that it might be a polyurethane or something awful like that. Paint stripper should make them sandable, tho. I've been meaning to email Tony Zinger and ask what their awful finish.  R%%%% Steve  
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Offline Andrew Hathaway

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Re: Balancing props
« Reply #4 on: February 23, 2009, 09:46:21 PM »
Acetone will take the finish off Zinger props fairly easily.  A real chemical stripper would probably work faster. 
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Offline Brett Buck

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Re: Balancing props
« Reply #5 on: February 24, 2009, 01:37:54 AM »
Quote from: Steve Helmick on February 23, 2009, 09:22:22 PM
I've got doubts about a lacquer working over whatever Zinger uses. It is very gummy stuff, even on props that have been drying in my basement for a year or more. I wish they would leave them bare, actually. It seems to me that it might be a polyurethane or something awful like that. Paint stripper should make them sandable, tho. I've been meaning to email Tony Zinger and ask what their awful finish.  R%%%% Steve  

    I strip the finish by wrapping a paper towel around the prop, and then pouring lacquer thinner over the whole thing. Squeeze it down onto the surface, hold it all for about a minute, then just wipe the finish off. If it seems a little reticent, repeat, but wrap it tightly in aluminum foil (to keep the lacquer thinner from evaporating) and leave it overnight. That will take it off, no matter what is on it. Zingers are a little tougher because its pretty thick, but it always worked for me in the past. Rev-ups take about 15 seconds and it comes out completely bare.

     Brett
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Offline Allan Perret

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Re: Balancing props
« Reply #6 on: February 24, 2009, 07:16:57 AM »
Quote from: Brett Buck on February 23, 2009, 09:11:19 PM
     It works, and I have done it, but it only works when it's already very close, and, if you use dope/lacquer you have to wait about a week to see how it turned out!
     Brett

I know that dope/lacquer continues to dry for weeks,  but I would have thought that 90+% of the solvents would gas off within 5~10 minutes allowing a good enough read on the balance ??
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Allan Perret
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Slidell, Louisiana

Offline Brett Buck

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Re: Balancing props
« Reply #7 on: February 25, 2009, 10:41:19 AM »
Quote from: Ty Marcucci on February 24, 2009, 10:06:12 PM
A light sanding of the stuff and the props balance. Then if it will not stay in any position, like Bob Z says, it is off center. TOSS it. Or use it to stir paint, But don't mount it on an engine, not even a FOX. LL~

      I would also caution that with some of the better balancers (like the High Point/overlapping wheel type or the magnetic suspension type like the Top Flite) you have to draw the line somewhere, and know when to stop. They are so sensitive that you may never get it to stay at any particular orientation. No matter what you do or how you do it, it's *always* out of balance, off-center, etc. - you can never get it perfect. It's a matter of judgement about how quickly it accelerates from a position. If it just sort of drifts slowly away, it's probably close enough.

      Brett
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Offline Kim Mortimore

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Re: Balancing props
« Reply #8 on: February 25, 2009, 12:26:13 PM »
Quote from: Brett Buck on February 25, 2009, 10:41:19 AM
      I would also caution that with some of the better balancers (like the High Point/overlapping wheel type or the magnetic suspension type like the Top Flite) you have to draw the line somewhere, and know when to stop. They are so sensitive that you may never get it to stay at any particular orientation. No matter what you do or how you do it, it's *always* out of balance, off-center, etc. - you can never get it perfect. It's a matter of judgement about how quickly it accelerates from a position. If it just sort of drifts slowly away, it's probably close enough.

      Brett

What about the claim that since a single-cylinder engine can never be fully balanced itself, attempts to fine-tune prop balance do not improve overall balance?  Or further, that a slightly out-of-balance 2-blade prop with the heavier blade pointing up at TDC on an inverted engine produces less vibration than a balanced prop?   Any merit here, or are these SMTRTD's (Stunt Myths That Refuse To Die)? 

Kim Mortimore
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Kim Mortimore
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