[Guest]

Originally Posted by davidmc36

I would be careful about what I read there, as with anybody's site that is just their personal opiniions and the like, take with a grain of salt and search out multiple sources.

On a quick browse for about half a minute I found him recommending sanding or scraping the sharp trailing edge of a prop so you can use your fingers to start a glo-engine. Several things wrong with that advice!!!!!

Blunting the trailing edge of a prop is a safety matter (prop kicks back when hand-propping) as well as the easiest way of removing material when balancing a prop and not affecgting the airfoil of the prop itself.

I learned from the get-go the correct method of hand-propping, which is to rest the fingers of the flipping (left) hand against the front face of the prop, with the popint of solid compression being at the 2PM position, flipping through the vertical position and transitioning the propping hand across your body and into your armpit.

The use of a chickenstick makes things even safer since your hand is now about six inches in pront of the prop.

An electric starter is by far the safest of the methods but you have to avoid hydro-lock.

Of course, now that I fly electrics, I have a differnt set of safety procedures to follow but the prop gets balanced the same old way -- remove it from the back edge of the prop, working from the tip backwards (law of levers in balancing).

[davidmc36]

I don't see why u would go to the trailing edge first. Yo will get more effective weight change by taking off the tip and never effect the airfoil. Blunting the trailing edge will for sure affect the airflow. I only go to the TE if the balancer tells me it is still off in that direction and when finished I make the TE the original shape.

[aspeed]

Taking a stone to the back corners of the bandsaw blade can help backing the blade out easier and turn a corner better. It is funny that cleaning up the trailing edge of the propeller is construed as unsafe. We fly control line .25 size racing and combat and are restricted to hand starting engines for pit stops. The MAAC, AMA and FAI rules stipulate this, and even allow deburring the prop edges as the only modification allowed to the prop as well as balancing. It is considered standard practise to deburr the trailing edge of the prop. Most pitmen use a glove or finger guard on the right hand.

[davidmc36]

Originally Posted by aspeed

It is considered standard practise to deburr the trailing edge of the prop. Most pitmen use a glove or finger guard on the right hand.

If you are talking about taking off the mold flash when you say de-burring, of course that is neccessary. What byrocat was saying about "blunting" the TE sounds like something completely different, something that changes the original shape of the airfoil. A sharp departure at the TE is desired to reduce turbulence and drag.

[CafeenMan]

Hi,

I'm the webmaster of Airfield Models. David emailed me the exact same concern. I replied that I was strictly speaking about removing the flash for a matter of safety as the flash is a defect. He then replied back by stating he removes the sharp edge too by using 400 paper. And now it appears he is back to saying leave it alone.

As several people have noted here and I will stand by, you should absolutely remove the razor sharp flash from the trailing edge of fiberglass or fiberglass/nylon propellers. It's clearly your choice to do it or not but it's good advice.

[davidmc36]

Originally Posted by CafeenMan

Hi,

I'm the webmaster of Airfield Models. David emailed me the exact same concern. I replied that I was strictly speaking about removing the flash for a matter of safety as the flash is a defect. He then replied back by stating he removes the sharp edge too by using 400 paper. And now it appears he is back to saying leave it alone.

As several people have noted here and I will stand by, you should absolutely remove the razor sharp flash from the trailing edge of fiberglass or fiberglass/nylon propellers. It's clearly your choice to do it or not but it's good advice.

You are totally wrong about what I am trying to say here. And I am still saying the same thing, don't try to make it sound like some flip-flop.

The point is that your advice and byrocats seem to say "blunting" or "sanding down" the TE beyond removing the flash. If you remove the TE flash properly, it leaves a razor sharp edge, the way the prop was designed.Quote from your site: "Caution! Some propellers have extremely sharp edges. For your own safety scrape and sand this edge down. If you try to flip the propeller by hand you will get a nasty razor cut."

If you remove the flash properly, all props have a razor sharp trainling edge. I have not changed my position one iota. You should not remove this designed sharp edge, that is completely different than removing mold defects (which by the way I often find to be big blunt squared off gobs of plastic.)

One of the cardinal rules of dressing damage on props on "real" airplanes (which I have been educated in and worked on for nearly 30 years) is that you return the edge to its original shape. Retain the radius on the LE and keep the sharp departure on the TE.

Your advice should simply be clarified so people do not think you are talking about making the TE blunt, which it is not supposed to be.

And where do you get from the previous post that I was " back to saying leave it alone". That is opposite to what I said.

I too will stand by what I say because it is correct.

I will also stand by my comments in post #10. Your site would do well with some additions, clarifications, and improvements.

[CafeenMan]

David, you are the only one who has ever come to that conclusion. That comment on my site has been there for years unchanged. I'm not trying to say you flip-flopped. I'm saying that you said you do the exact same thing that I'm saying to do.

Frankly, I don't think there is a pilot alive who could even tell the difference. And since the flash is a defect you don't know that leaving it on the propeller isn't making the propeller worse. Since you're claiming that my advice causes the propeller to be worse than it was upon purchase I would like to see you data backing that claim using actual model aircraft propellers.

[davidmc36]

Originally Posted by CafeenMan

David, you are the only one who has ever come to that conclusion. That comment on my site has been there for years unchanged. I'm not trying to say you flip-flopped. I'm saying that you said you do the exact same thing that I'm saying to do.

Frankly, I don't think there is a pilot alive who could even tell the difference. And since the flash is a defect you don't know that leaving it on the propeller isn't making the propeller worse. Since you're claiming that my advice causes the propeller to be worse than it was upon purchase I would like to see you data backing that claim using actual model aircraft propellers.

To argue with a person who has renounced the use of reason is like administering medicine to the dead.

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[Guest]

Hey you two, cool it and take this off-the-thread!

Model aircraft props and full-size props are different beasts, |Reynolds numbers tell the story. Removing material from the trailing edge of the prop does not affect its properties and the total amount removed is minimal. I was taught to work from the outside (tip) in, which is effective and can be done easily with a kjnife at the field. Removing material from the tip itself is possible but I was taught "trailing edge" and we're talking 9-12 inch props.

Beyond a certain point, removing too much material will affect the prop. If it is that out of balance that you've removed a significangt material (more than 1/8th of an inch), ditch the prop.

Let's get back to the original quesrtion and stick to it!

[Cross Check]

Hi Byrocat,

My average bandsaw blade is 6TPI.
I go up or down, depending on what I am cutting...
Blade tension/feed rate are the keys...
If you let the teeth do the cutting, you will have no problems.

Bandsaws are Great.
(I have a special 'relationship' with mine !)
And a 'bazillion' linear miles of cutting distance experience...

Every job, I imagine cutting it by hand saw.

Then, let my machine do the work....

Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 7437
Unabashed Combat Team