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FlyingMonkey

Prop Issue -- Cosmetic or Serious?

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BTW, I took the time to measure and mark everything before removing my Neuform.  For those who might still be struggling with getting a good pitch on their props, I have an excellent setting on mine that works very well at "flatlander" cruise altitudes of 2000-5000ft.

If you level the prop on the top at the apex of the prop curve, mark the prop at 6" from the end and put your protractor there.  Pitch the prop at 21 degrees and that should get you pretty close to a good setting, though you might have to tweak it a little due to slight differences in airplanes or how you measure.  The protractor goes on the back and the top of the blade should be farther forward than the bottom.  21 degrees the other way won't work nearly as well...

 

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I'm going to be calling FD tomorrow, but it's looking more like a Sensenich will be in my future, if FD is going to hit me for over $1000 anyway.  I'd rather spend a bit more and get a prop with metal leading edge that I have a bit more confidence in and is made in the USA.

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23 minutes ago, DJ Todd B said:

Since you have had both props, does the Sensenich prop perform better than the Neuform prop?

Close enough to the same you probably couldn't tell the difference. The Neuform is a 64" and the Sensenich a 68" I would give the edge to the Sensenich for climb. Cruise is about the same.

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28 minutes ago, Roger Lee said:

Close enough to the same you probably couldn't tell the difference. The Neuform is a 64" and the Sensenich a 68" I would give the edge to the Sensenich for climb. Cruise is about the same.

Roger,

The Sensenich prop you are referring to, is it fully adjustable or notched?

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Fully ground adjustable. I had one on my CTSW and FD put them on LS's for a while. This particular prop is on several LSA and works quite well.

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1 hour ago, FlyingMonkey said:

BTW, I took the time to measure and mark everything before removing my Neuform.  For those who might still be struggling with getting a good pitch on their props, I have an excellent setting on mine that works very well at "flatlander" cruise altitudes of 2000-5000ft.

If you level the prop on the top at the apex of the prop curve, mark the prop at 6" from the end and put your protractor there.  Pitch the prop at 21 degrees and that should get you pretty close to a good setting, though you might have to tweak it a little due to slight differences in airplanes or how you measure.  The protractor goes on the back and the top of the blade should be farther forward than the bottom.  21 degrees the other way won't work nearly as well...

 

You would also need to know the level of the airplane longitudinally. Your numbers will get you close, but could be off by a degree or more depending on how the airplane is sitting.

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You won't need any degree settings. Just set the static rpm on the ground to around 4700-4750 and go fly it. Go WOT in level flight and make the final adjustment for your WOT rpm in flight.

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Your Experimental Operating Limitations probably require your geographical FSDO to provide written approval of the "Major Change", prior to flight, if you replace the Neuform.

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2 hours ago, Roger Lee said:

You won't need any degree settings. Just set the static rpm on the ground to around 4700-4750 and go fly it. Go WOT in level flight and make the final adjustment for your WOT rpm in flight.

And how do you get to that 4700-4750 on the ground setting?

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6 hours ago, Tom Baker said:

You would also need to know the level of the airplane longitudinally. Your numbers will get you close, but could be off by a degree or more depending on how the airplane is sitting.

I posted that procedure to get people who have never done it into the ballpark.  As I said, tweaking might be needed.  If you are starting from scratch with no static runup rpm or prop pitch information, I think what I wrote will be a good starting point.

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36 minutes ago, FlyingMonkey said:

I posted that procedure to get people who have never done it into the ballpark.  As I said, tweaking might be needed.  If you are starting from scratch with no static runup rpm or prop pitch information, I think what I wrote will be a good starting point.

What are you measuring your 21° against, the front of the prop hub, from level, or from vertical?

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4 hours ago, Tom Baker said:

What are you measuring your 21° against, the front of the prop hub, from level, or from vertical?

JMO, but I believe it is the angle of attack from flat pitch (0°).

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7 hours ago, Tom Baker said:

And how do you get to that 4700-4750 on the ground setting?

By starting the engine of course. :rolleyes:

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someone said composite aircraft won’t age as well as aluminum. I think  composite aircraft can last as long if not longer than aluminum  provided the composite structure is properly designed, used, and maintained.

I remember reading somewhere that aluminum weakens with enough routine loading for long enough, something about the flexure modulus or something of that nature. At the same time carbon and Kevlar can be loaded and unloaded within spec infinitely with no property changes. 

I have a friend who builds 50ft+ carbon racing yachts. He said carbon will last forever and ever if it’s maintained. The trade off is, if carbon is loaded beyond spec, it fails spectacularly. It basically explodes apart. 

Anywho, I think the issue is aluminum is more receptive to abuse, but if a composite aircraft isn’t abused and maintained it should last forever. 

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9 hours ago, WmInce said:

JMO, but I believe it is the angle of attack from flat pitch (0°).

Correct.  The procedure is as described on this forum numerous times by Roger and others.  Put the plane on a level surface (my hangar floor is very good, and reads within 0.05° at any point it's measured in any direction), level the blade so it's parallel with the floor, put the protractor on it, and measure from 0° as described in the protractor docs.  As long as all blades are leveled the same and the protractor is put in the some position on each prop blade (e.g. distance from the tip) you should get the same values.  Again, my post was not meant to get you dead on results, but if you use the values I posted and the same procedure, it should put you in the ballpark, and then you can tweak to taste.

BTW, I wrote a pretty detailed explanation of the entire process of pitching a Neuform prop with pictures for another member of this forum.  If anybody wants a copy, PM me your email address and I will send it to you.

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46 minutes ago, CTMI said:

someone said composite aircraft won’t age as well as aluminum. I think  composite aircraft can last as long if not longer than aluminum  provided the composite structure is properly designed, used, and maintained.

I remember reading somewhere that aluminum weakens with enough routine loading for long enough, something about the flexure modulus or something of that nature. At the same time carbon and Kevlar can be loaded and unloaded within spec infinitely with no property changes. 

I have a friend who builds 50ft+ carbon racing yachts. He said carbon will last forever and ever if it’s maintained. The trade off is, if carbon is loaded beyond spec, it fails spectacularly. It basically explodes apart. 

Anywho, I think the issue is aluminum is more receptive to abuse, but if a composite aircraft isn’t abused and maintained it should last forever. 

Endurance limits, in metallurgy is the limit at which, when loaded below it, no fatigue occurs.

It is steel and titanium alloys that hold that honor.

Carbon composites have a very high fatigue cycle before failure, but they do fail eventually.

Anyways, it's the binding agent, the epoxy, that is the problem. Epoxy actually has a weakness to water, even moisture in the air. Water resistant epoxies are in use in the marine industry but it's not foolproof.

We're still seeing the technology rapidly developing. 30 years ago, epoxy formulations were quite terrible. Other resins were preferred such as polyesters.

We're still in relatively uncharted territory, I certainly hope today's epoxies can outlive me, but we'll see.

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I raced a sailboat class called E-scows for over a decade. The boat is 30 feet long, 7 feet wide and only about 18 inches deep. (it even kind of looks like a wing) They made a batch of epoxy boats in the 90s instead of the standard vinylester/polyester used for the rest of the fleet. Those boats are still stiffer and lighter than the brand new ones being made. They are absolutely bulletproof. 

Epoxy does not have a weakness to water, and certainly and absolutely is not affected by moisture in the air. You’re thinking core materials. And even core materials are not all susceptible. Divynicell, keracell and similar products for instance, are a closed cell structure that is highly resistant to water. On the other hand, aviation cores like the rohacell used in our planes are much less resistant to water and chemicals. Water intrusion can happen with nomex Kevlar cores as well though it’s bonding that’s the major difficulty with honeycombs, which is why the bulk of those layups are prepreg bagged and autoclaved.

There isn’t a different chemical property to aviation composite epoxy than is used in the marine industry, with the exception of high heat epoxy formulations used around jet engines.  

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Actually the big weakness of epoxy is not water it’s sun. Epoxy is not UV stable, which is why we need to take good care of our paint! 

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When my friend Phil got his 2008 CTLS, I was amazed that the stabilator's trim tab used the graphite skin for a "living" hinge.  I thought I wasn't seeing the big picture and there must be hinges I didn't see.  Nope, just the parent graphite skin being used.   I am amazed that this is how this area is designed but I feel FD would not have done this if there was any doubt on their part about the longevity of this.  Since the trim tab articulates with the stabilator, it goes thru many thousands of flex cycles.  Sure wouldn't be the way I would have designed it but I don't know squat about composites.

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8 hours ago, Roger Lee said:

By starting the engine of course. :rolleyes:

Starting the engine does not give you the setting, it shows you the results of the setting. You said you don't need a degree setting to start with, but I would bet dollars to doughnuts that when you set up a prop that you have a starting blade angle that you use before you check the static RPM.

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Runtoeat: That’s interesting! One of the biggest misunderstanding about carbon/Kevlar is the difference between strength and stiffness. Carbon is STRONG but it isn’t really stiff. Stiffness comes from the core. In fact if you do a flat layup of 4 layers of 12k 4x4, it will bend like a piece of paper. There’s YouTube videos that show it.

now take that same layup but put 2 layers on either side of a 1/4” core and you can stand on it and it won’t bend. 

Such cool stuff. 

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16 minutes ago, Runtoeat said:

When my friend Phil got his 2008 CTLS, I was amazed that the stabilator's trim tab used the graphite skin for a "living" hinge.  I thought I wasn't seeing the big picture and there must be hinges I didn't see.  Nope, just the parent graphite skin being used.   I am amazed that this is how this area is designed but I feel FD would not have done this if there was any doubt on their part about the longevity of this.  Since the trim tab articulates with the stabilator, it goes thru many thousands of flex cycles.  Sure wouldn't be the way I would have designed it but I don't know squat about composites.

The original Zenith 601 Zodiac design uses the same thing on the ailerons...no hinge, just the upper aluminum skin extended down as the top of the aileron and allowed to flex.  Most since then have been build with piano hinges because the skin flex thing weirds people out, but there there are still some flying like that and have never had an issue AFAIK.  

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Believe it or not most props are in the same ballpark for degree settings. Yes they are different, but close enough to set and get a static run setup. When I did my big prop research project they were all close enough for a good starting point. The only real difference was two blade static vs 3 blade static. When I use the 3 blade static rpm to set a two blade for a flight run I was under pitched and ran right up to and could have been over the 5800 max. Setting a prop pitch is quite easy and straight forward.

So if Andy uses the settings off the Neuform and applies it to a Sensenich he will be in the ballpark for a good static run up.

So my answer still stands. Start the engine is the only way to take a look and see where you are.

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I'm still getting some clarification, but Arian wrote me back this morning and said these cracks are not uncommon and are just gelcoat cracks and cosmetic only.  $400-500 if I want them to refinish it and rebalance.  I think I will leave them as they are and save that money to start preparing to buy a Sensenich.  I have to admit I'm disappointed in Neuform that a hangared and cared for prop should have issues, even cosmetic, at 600 hours.

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