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FlyingMonkey

Prop Issue -- Cosmetic or Serious?

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1 hour ago, FlyingMonkey said:

 

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.

Andy, I know that your setting was a starting point. I am not saying the information you gave is not valid. What I am saying is it may only be a good starting point for your airplane sitting in your hangar. What I am saying is that unless you are measuring an angle compared to the prop hub, that the angle the airplane is sitting will effect the number. A low nose tire, oversized tires on the main gear, bent gear legs on a CTSW will all throw the angle off.

I have set the prop pitch on many different airplanes. I have my own homemade fixture for setting prop pitch. I can get the pitch within 1/10th of a degree between blades. that uses a digital level along with a bubble level to position the prop balde.

prop.jpg

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1 hour 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.

From when the airplane was introduced at Sebring 2008 it was my understanding that the hinge is Kevlar.

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39 minutes ago, Roger Lee said:

 

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

Agreed that starting the engine is the only way to find out where you are, but I am sure you measure the blade angles before you start the engine. You will want to make sure they are in the ballpark, and all reasonably close to the same angle.

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25 minutes ago, Roger Lee said:

When you get a Sensenich they come with blade setting angle pins. Use #3 and off you go.

The pins may be good enough for a start, but it has been my experience that using the pins does not get the blade angles matched as closely as I would like.

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To me the pins are only good enough to get you in the ballpark. You must set them by hand after that. Even Sensenich agrees and does theirs by hand. They say the pins look good on paper though. 

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I was surprised at how bad the paint was chipped up on the back side of a Sensenich with 150 hours. 2011 CTLS. The Nueforms always look like new.

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:hi-1082:Mine has some minor surface cracks in coating. Not a question just letting you

know  your not the only one with surface stress marks or cracks.

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9 minutes ago, procharger said:

Mine has some minor surface cracks in coating?

Is that a question?  Because if you don’t know, we certainly don’t either...  :giggle-3307:

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Tip, it doesn't seem that there should be surface chipping.  Reading the installation manual, there is an area where surface refinishing is addressed but, personally,  I would be disappointed if this condition occurred on my prop, especially on a low hour prop.  I guess Sensenich paints the props where Neuform has a gel coating?  Wonder if this was a unique situation or if this is found on all Sensenich composite props?

Sensenich Installation Instructions-3 Blade.pdf

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I am not sure what Tip was seeing, but the chipping of the paint on the Sensenich props I have seen was on the face of the prop, (the flat surface on the rear of the prop), on the leading edge. I think it was more of a paint adhesion problem on the stainless material than anything else. Still unsightly none the less.

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It’s not my plane, but one that I saw. Tom’s right. What most people call the back is actually the “face”. The side you see from the cockpit.

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23 minutes ago, Tip said:

It’s not my plane, but one that I saw. Tom’s right. What most people call the back is actually the “face”. The side you see from the cockpit.

I vividly remember from A&P school the instructor would drill one of the students on the terms of the propeller. The Back is in front, and the face is in back. The student would get so flustered.

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1 hour ago, Tom Baker said:

I vividly remember from A&P school the instructor would drill one of the students on the terms of the propeller. The Back is in front, and the face is in back. The student would get so flustered.

Sounds to me like you never got over it. . . .:giggle-3307:

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23 minutes ago, WmInce said:

Sounds to me like you never got over it. . . .:giggle-3307:

It wasn't me, but I felt sorry for the kid. Back in my youth if I heard it once I remembered it, at least long enough to pass the test.

 

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2 hours ago, Tom Baker said:

Back in my youth if I heard it once I remembered it, at least long enough to pass the test.

Age brings change.

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On 4/23/2018 at 9:42 AM, CTMI said:

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.  

In the uncured stage, it is highly hygroscopic due to the polar charges present in the resin.

In cured epoxies, the ester bonds are vulnerable to water intrusion, depending on the type of hardener used. More specifically, the research is in the hardener to make the final the cross-linked product chemical and water resistant.

It is also possible, and proven through research, that water has the capability to diffuse through epoxy and collect in microvoids in the cured resin and has a detrimental effect on strength.

To say there isn't a difference is completely and utterly false. However, I admit that there are many systems out there and the above probably only applies to some systems and not others. There are many types of epoxies, what makes it an epoxy is if it has an epoxide group in the molecular structure. Similar in concept to how a molecule is an organic molecule if it has a carbon chain or ring, even though the similarities pretty much end there.

That said, epoxies marketed towards marine are far more likely to have those hardeners that make them water resistant. There might not be a difference in some of the epoxies used between aviation and marine, but this won't be universally applicable.

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On 4/24/2018 at 9:39 AM, Tom Baker said:

It wasn't me, but I felt sorry for the kid. Back in my youth if I heard it once I remembered it, at least long enough to pass the test.

 

Nothing is confirmed until officially denied!!:giggle-3307:

  • Upvote 1

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On 4/25/2018 at 12:18 PM, Anticept said:

In the uncured stage, it is highly hygroscopic due to the polar charges present in the resin.

In cured epoxies, the ester bonds are vulnerable to water intrusion, depending on the type of hardener used. More specifically, the research is in the hardener to make the final the cross-linked product chemical and water resistant.

It is also possible, and proven through research, that water has the capability to diffuse through epoxy and collect in microvoids in the cured resin and has a detrimental effect on strength.

To say there isn't a difference is completely and utterly false. However, I admit that there are many systems out there and the above probably only applies to some systems and not others. There are many types of epoxies, what makes it an epoxy is if it has an epoxide group in the molecular structure. Similar in concept to how a molecule is an organic molecule if it has a carbon chain or ring, even though the similarities pretty much end there.

That said, epoxies marketed towards marine are far more likely to have those hardeners that make them water resistant. There might not be a difference in some of the epoxies used between aviation and marine, but this won't be universally applicable.

well, agree to disagree. I think our painted, carbon airplanes, if maintained, will outlast us all. 

cheers!

 

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1 hour ago, CTMI said:

well, agree to disagree. I think our painted, carbon airplanes, if maintained, will outlast us all. 

cheers!

 

That's what I hope! I'm not saying they won't, I'm saying we still need to see.

There's a lot of homebuilts made with polyester built in the 70's that still fly. Not a whole lot of epoxy built aircraft with age even close to that however, and quite a few even professionally built ones that failed miserably. That said though, we might be alright in the long run, CT's are definitely past that initial pioneering... but there are still ghosts of the past we need to be careful of that can pop up again.

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