Tips For Dressing a Prop???

One of the things that gives me the creeps when working on my RV is filing on the propeller. My 9a with that big Hartzell on the front seems to act like a vacumn cleaner and pick up stuff off the ramps and leave little nicks in the prop more than my Cherokee ever did so cleaning up the blades happens more frequently.

How do you dress your prop? Any tips, tricks, or special tools? Are there any veterans of propeller dressing out there that would like to share tips and techniques?

Recently somebody showed me how to clean up the prop without removing material, but having never seen anybody else do this I'm reluctant to do it on my airplane. Instead of filing out nicks he uses a smooth steel roller of sorts, such as a large punch and slides it up and down the blade with pressure applied. On the nicks he rolls the punch back and forth instead of just sliding it, and then once smoothed out he slides it back and forth. Over several minutes the blade is free of nicks and the shape of the airfoil appears to be original. For lack of a better term the nicks appear to be "Smooshed" back into place. The end product is beautiful, but I'm wondering if it does anything to prevent cracks or blade failure. It also seems like this method would work harden the affected area. This person is not an A&P, but is pretty crafty none the less. This method makes the prop pretty again, but it just doesn't seem to fix anything. ???

Another person locally has made a set of tools with varying grades of sandpaper adhered to them. The tools are made of some sort of nylon plastic material similar to the plastic that the slider canopy blocks are made from. These seem to work well.

Then of course there are small files and most of us have many of these to work with. Lastly there is the Dremel Tool on the work bench that yearns to be used, but surely must not be allowed to touch my beloved Hartzell. So, please share, how do you clean up nicks from your prop? Is there a right way?

EAA Tips for Homebuilders Series

EAA has a good video of a professional dressing a metal prop. http://eaa.org/video/homebuilders.html?videoId=3735936001

Avoiding damage

Capflyer, that was a good video. Thanks for posting.

I know that I will be sweating bullets the first time I have to drag a large file across the blade of my Hartzell.

To minimize nicks on the leading edge of the blade does anyone have any first hand experience using some protective tape, metal or otherwise?

I understand that you might have to sacrifice some performance by adding tape to the blade. For those who tried it, does it work and is it worth it?

Mike Draper
RV-8
TMX0360 CS
Finishing

The AC referenced in the video, 20-37E, has some interesting reading on the issue, though it largely covers the repair of larger nicks, and what sort of damage are unacceptable to repair.

Bryan Wood said:

One of the things that gives me the creeps when working on my RV is filing on the propeller.

Click to expand...

Hi Bryan,
Working on the prop scares me too. I do all of the maintenance on my RV except for the prop. As part of the periodic inspection I take my plane to the local LAME (Licensed Aircraft Maintenance Engineer) for a grease and dressing and possibly a dynamic balance and consider it money well spent. When my prop was only about 20 hrs old I got a ding on the leading edge that was more like a crater than a nick. It was the sort of thing that would make even an Australian man cry. I took it to my LAME to be dressed and cried again when I saw all that aluminum being filed away. Anyway, this convinced me that dressing the prop (especially for big nicks) is a job for the experts. I think this is especially applicable for our type of aircraft which are likely to have untested prop/engine combinations involving electronic ignition and higher compression.

Fin
9A Hartzell CS prop
..

First let's avoid the damage whenever possible.

I fly my RV off of gravel and never have a problem. In the early '70s I had a Mooney (9" of prop clearance) that I also flew off of a grave runway. The only nick I ever got was by the previous owner checking me out in the Mooney.
An airplane only accelerates so fast. Cramming the throttle full forward while sitting still is where the problem arises. Always get the airplane moving with as little throttle as possible. Once the airplane is moving maybe 2 airplane lengths, start to feed in the throttle smoothly. When the airplane is moving it doesn't pick up FOD.
I've done tests to check out the old adage of "full throttle and hold the brakes." On our little airplanes it gives no advantage. People who ride with me get nervous when I do this on my 1500' strip. But we get off at the same point as the people who firewall the throttle at the start. Except with a cleaner prop.
BTW, anytime you file a prop, use the same number of strokes on each blade.

Everyone has made good points, and I'm sure Mel will know what I'm talking about here. If you've been around airplanes (or working on them) for very long will have seen some ungodly and truly scary prop blade filing on old junkers. I only made this post to point out one I saw a year or two ago on an old Stinson 108. The prop has a "nick" filed out of it that I couldn't believe. I actually was able to almost hide an entire half of a nickle in the area that had been filed out - on one blade only. I asked the guy about it and he said he'd been flying it that way for a long time. Also, I did some work on a Luscombe some years ago, and after pulling the cowl noticed something a bit wonky. There were hardware store washers between the prop and crank hub (in varying stacks of thickness around the crank). Long story, but the short version is that this was the owners "solution" to a 'slightly' bent prop. He shimmed it up with washers until it tracked straight...then went flyin! Needless to say I walked away and never looked at that airplane again.

Anyway, props can be scary things - especially for someone who's had their hand in a running one and am now a digit "short" to prove it, but maintaining them shouldn't be that scary. Just be meticulous and you'll be fine. It's not as much voodoo as you might think and is much like maintaining the rest of your plane. Filing nicks is standard procedure and has been for a long time. I just needs to be done right and within specs.

It's amazing that Mel is ALWAYS right! I too have had my RV off of gravel many times and it lives on grass. Never been a problem other than lots of bug guts.

My 2 cents as usual.

Cheers,
Steinc

Mel, do you think the nosedraggers are more prone to nicks on the prop?

Bryan Wood said:

How do you dress your prop? Any tips, tricks, or special tools? Are there any veterans of propeller dressing out there that would like to share tips and techniques?

Click to expand...

A 10x magnifier and a bright light, round and half round files, 220grit paper, 400grit paper, emery paper, crocus cloth, clean it, alodine it, spot-prime & paint it. Remove as little material as possible... but leave no sharp corners - gentle radii are your friend. Remove as much material from the opposing blade, in the same place, as you removed on the damaged blade.

Recently somebody showed me how to clean up the prop without removing material, but having never seen anybody else do this I'm reluctant to do it on my airplane. Instead of filing out nicks he uses a smooth steel roller of sorts, such as a large punch and slides it up and down the blade with pressure applied. On the nicks he rolls the punch back and forth instead of just sliding it, and then once smoothed out he slides it back and forth. Over several minutes the blade is free of nicks and the shape of the airfoil appears to be original. For lack of a better term the nicks appear to be "Smooshed" back into place. The end product is beautiful, but I'm wondering if it does anything to prevent cracks or blade failure. It also seems like this method would work harden the affected area. This person is not an A&P, but is pretty crafty none the less. This method makes the prop pretty again, but it just doesn't seem to fix anything. ???

Click to expand...

Sounds similar to "burnishing". A couple other phrases that pop into my head while reading that are "stress riser" and "stress corrosion cracking". I don't recall burnishing being taught in A&P school as an acceptable method of repairing a nicked prop blade. In fact, now that you've got me thinking... AC 43.13-1B para. 8-73 says:
"However, it is not permissible in any case to peen down the edges of any injury wherein the operation will lap metal over the injury."
My personal opinion of anyone doing that to a prop?
Run far, run fast.

Another person locally has made a set of tools with varying grades of sandpaper adhered to them. The tools are made of some sort of nylon plastic material similar to the plastic that the slider canopy blocks are made from. These seem to work well.

Click to expand...

Awesome idea. I've used pencils, pens, drill bits, and other objects as expedient mandrels for sanding nicks out of prop, turbine, and rotor blades...

Then of course there are small files and most of us have many of these to work with. Lastly there is the Dremel Tool on the work bench that yearns to be used, but surely must not be allowed to touch my beloved Hartzell. So, please share, how do you clean up nicks from your prop? Is there a right way?

Click to expand...

You can get away with a Dremel and a fine-grit sanding drum, but it's easy to take too much material off.
There is a right way - Hartzell prop blade repair and AC 43.13-1B, Chapter 8.

Bryan Wood said:

Mel, do you think the nosedraggers are more prone to nicks on the prop?

Click to expand...

Bryan, no comparison. Next time you are at an RV gathering, look at the back sides of props TD vs TG, and you will see a large difference in the sheen of the black paint. The TG's props sit only about 10" above the ground, while the TD's are perhaps twice that.

I always accelerate the engine slowly to get the plane rolling long before reaching full power.

Around here, in the winter, they will put some sand at the end zones of the runways (nice). While that doesn't nick the props, it does dull down the back sides cosmetically, and will rough up the leading edges of it. I take some 400 grit paper on a little maple block to clean that up.

Bryan Wood said:

Mel, do you think the nosedraggers are more prone to nicks on the prop?

Click to expand...

Obviously the less ground clearance you have, the more susceptible to damage, but again, if you are careful, it shouldn't be a problem.

Prop Dressing Errosion

One thing I could never figure out is the frequency of cleaning up the leading edge. Dressing removes material-even if only several thousands. If one would theoretically dress the prop after each sign of erosion or minute pitting, one would remove a finite amount of material equal to the depth of each imperfection removed. This would add up quickly. So then that brings up the question: How long can these minor erosion pits remain before needing to be addressed. Note that I am only talking about the erosion type roughness and not a noticeable singular rock ding which should be addressed immediately. My concern has been changing the original blade profile by dressing too often.

I watched it done, too.

I'm referring to "wiping" the prop leading edge with another harder object. In this case the tool was a big heavy Craftsman screwdriver. The mechanic gripped the tool by the handle and the pointy end and proceded to draw the shank of the screwdriver along the prop blade leading edge, moving from root to tip. Someone else held the opposite (RH) prop blade while he reshaped the area around the rock chip. He used that brand of tool because of the non-chromed shank.