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New E-Prop install


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6 hours ago, Jim Meade said:

The story I got was the 4mm screw was not quite to tolerance and they changed to a 5mm screw for whatever reason.

They're quite specific about not using Loctite or oil, etc.,  on the bolts that have a torque spec.

These are not long bolts that stretch under torque, which is what secures them, we are only talking about short spinner screws. I agree the prop mounting screws should never use Locktite. My screws are 5mm however few of the rivnuts used do not retain the screws well so I use 222 to secure the screw, I see no other option at this time. I have had no issue with this. Also trying to tighten screws too tight on carbon fiber is not good and will damage the spinner over time.

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I probably should not have repeated their admonition against using any kind of lubricant on a torque spec bolt as it seems to have confused the issue.  No one said the spinner bolts have a torque spec.

If I recall the instructions are to check the torqued bolts every 6 months - 12 months if they are titanium (I'm doing this from memory so don't someone start quoting me). My point is, the spinner is going to need to come off on a regular basis so I'll consider that when I decide how to secure the spinner bolts.  Some kind of washer seems worth considering along with the Loctite.  Of course, one can inspect the spinner fasteners at each pre-flight.

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36 minutes ago, Jim Meade said:

I probably should not have repeated their admonition against using any kind of lubricant on a torque spec bolt as it seems to have confused the issue.  No one said the spinner bolts have a torque spec.

If I recall the instructions are to check the torqued bolts every 6 months - 12 months if they are titanium (I'm doing this from memory so don't someone start quoting me). My point is, the spinner is going to need to come off on a regular basis so I'll consider that when I decide how to secure the spinner bolts.  Some kind of washer seems worth considering along with the Loctite.  Of course, one can inspect the spinner fasteners at each pre-flight.

The titanium bolts have a much longer retorque interval,  200 hrs or 12 months. Basically done at annual just like some other aircraft. If a screw comes out in flight it will most likely take a piece out of a blade like it did on my original V12 prop. I'll stick with 222 on any loose screws, it hasn't been an issue for me. The problem is in the rivnut thread retention . I do not, however like the slotted type of screw heads they use and will change them later. The reason they used that type is to be able to remove and install them with a coin ( their writing ). I however am able to afford a screwdriver. 

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I had one screw come out and it did no damage to the prop blade.  Two adjacent spinner bolts were loose and as a result the spinner wobbled and made a mark, but no abrasion, on two blades.  The other three screws were tight.  This was with 17 hours and I admit I should have inspected the spinner more carefully.  That would likely have revealed the loose screw.   I will make sure to inspect it before the first flight of each day now.

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I mentioned this issue to E-Props and they acknowledged my communication but did not offer anything else. I'm sure they are aware of this issue. I guess if you had to you could use a lock nut on the screw which protrudes from the rivnut, it's easy to access. 

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On 1/29/2021 at 8:19 PM, FlyingMonkey said:

I guess maybe my aerodynamic understanding is flawed.  Does it matter what the rpm in climb is?  I know a flatter pitch will turn faster for a given throttle setting, and that generally leads to better climb.  But doesn't RPM in a climb have nothing to do with anything except how hard the engine is loaded at that throttle setting (I assume we're talking WOT here)?  If you are turning 5400rpm in climb vs. 4800rpm,  why not pitch up more to load the engine and produce an even higher climb rate?

It sounds like what we're saying is that the engine has less load on it in a WOT climb, yet still climbs 300fpm more?  And yet the E-prop is loaded MORE in cruise (5600rpm  vs 5650rpm) at WOT?  Not sure how the prop is loaded both more and less than the Sensenich at a fixed pitch setting.  I suppose this is the "constant speed effect", but so far nobody can explain what that means.

Does anyone know what the ideal pitch angle is for the sensenich R68C on a 912 ULS.  Plane is typically on takeoff at field level 1000’ msl. 

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The pitch can vary depending on your flying needs and your average altitude. Set the static WOT pitch to get around 4700 ish. Then go fly at your average altitude. Shoot for a WOT rpm of around 5600 - 5650. After your test flight if you are too low an rpm flatten the pitch a tad and if your rpm is too high courses the pitch. It’s very easy to do. If you have any questions your welcome to call me.

p.s.
If I used a pitch here at my hanger and you did one at your hangar it can vary depending on a couple factors.

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This discussion should really be split.  We've been talking about E-PROPS and now are changing to Sensinich.  Apples and oranges.  The E-PROPS is set for 5500 +-50 level flight WOT and the company can explain why.  I'm posting this just so we don't start getting pitch settings confused between the two types of props.

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  • 1 month later...

Interesting change when doing my 5 year rubber change. When reinstalling the engine to the airframe I repositioned the E Prop to center the spinner with the cowling with about a 1/8 inch overlap,  a pita but worked out. On the first flight I had to reset the rudder trim a fair amount. However after that I got a 5 knot increase in TAS consistently in the 1 hour flight. All variables were the same since the previous flight (temp 90°F+, altitude,  fuel load, etc). Apparently the E Prop spinner is designed to fit over the cowl. 123kts at 5400, 115kts at 5000 static is tight.

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It's not published in the maintenance manual, but there are two thrust angles.

The first is to the right at 2.6 degrees, plus or minus 0.2.

The second is down from the parallel to the fore and act wing bushings in the fuselage. 3.4 degrees +- 0.2

If the cowling is your original from the factory and undamaged, then centering in it is acceptable.

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6 hours ago, Anticept said:

It's not published in the maintenance manual, but there are two thrust angles.

The first is to the right at 2.6 degrees, plus or minus 0.2.

The second is down from the parallel to the fore and act wing bushings in the fuselage. 3.4 degrees +- 0.2

If the cowling is your original from the factory and undamaged, then centering in it is acceptable.

If it's not in the maintenance manual then it's not significant. Sometimes you you have to try it and fly it.

 

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The one I have installed required quite a bit of shimming to get the spinner centered. As you move the motor mount out it causes the rudder cables to loosen. I had to make a fairly big adjustment to tighten the cables back up. I'll be installing an other E-Prop soon, and this airplane is already centered on the cowling.

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1 hour ago, Tom Baker said:

The one I have installed required quite a bit of shimming to get the spinner centered. As you move the motor mount out it causes the rudder cables to loosen. I had to make a fairly big adjustment to tighten the cables back up. I'll be installing an other E-Prop soon, and this airplane is already centered on the cowling.

My e-Props spinner is slightly off center and pretty close to the cowl on the right side.  But it's not rubbing or causing any issues so I left it alone and keep an eye on it to make sure it doesn't get any closer to the cowl.

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4 hours ago, Madhatter said:

If it's not in the maintenance manual then it's not significant. Sometimes you you have to try it and fly it.

 

It's not in the maintenance manual because the old flight design didn't want just anybody taking the engine off the airplane and doing any related work to that. That's why you can't find torque values for the bolts either, but I doubt you would say torque is insignificant too.

I don't understand why they did it that way, but that was their belief. You have to ask for this info and it really grinds my gears when this stuff is withheld from the manuals.

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11 minutes ago, Anticept said:

It's not in the maintenance manual because the old flight design didn't want just anybody taking the engine off the airplane and doing any related work to that. That's why you can't find torque values for the bolts either, but I doubt you would say torque is insignificant too.

I don't understand why they did it that way, but that was their belief. You have to ask for this info and it really grinds my gears when this stuff is withheld from the manuals.

Torque on bolts is an SAE standard for bolt size, metal alloy and thread type, coating, etc.  If you under torque it or over torque it you will most likely have a failure. The CT refers to standard torque values unless otherwise noted. It is the stretch on the bolt that holds it which is directly related to the torque. If the manuals don't give all the information to maintaining an aircraft , that is stupid and libel for the manufacturer.  Unqualified incompetent people are always working on their aircraft,  I see them every day (literally).

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I am sorry, when I rewrote part of my post I mistakenly left out the important bit: I meant to say find torque values for the engine mount bolts to the firewall. They go through composite structure and it SHOULD give anyone pause before just tightening to standard spec. This is a spec not in the manual, you have to ask FD (thought the spec they gave me is in fact just standard spec, just making a point).

I checked the CTSW manual, same thing, not only is thrust angle not mentioned at all, but neither are any instructions regarding the T-Mount or torque on the bolts. Plus there's this tidbit about the engine replacement:

image.png.25fe457527b3161d43fa453c7b60304b.png

Anyways Madhatter, you're a respected person around this forum. So please understand my concern that when you say something like "If it's not in the maintenance manual then it's not significant." That's a potentially dangerous phrase that can be taken out of context by others who read and respect what you have to share, and you incorrectly assume that Flight Design is giving us everything we need to know to maintain their aircraft. They're not. Just like Rotax won't give us their overhaul manuals and some parts will not be sold to you by their distributors without current training. Whatever reasons they may have, the fact is, they're not fully forthcoming. This isn't the standard airworthiness world, and speaking from how I came from other industries... I was DUMBFOUNDED with how much technical data the manufacturers in aircraft are willing to put out.

It absolutely pisses me off when manufacturers withhold, but it's not like this isn't unheard of. Car manufacturers have been going this direction for a while now too (try performing ECU diagnostics if you aren't one of BMW's approved service centers!). Hell, everyone knows how John Deere is too...

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12 minutes ago, Anticept said:

I am sorry, when I rewrote part of my post I mistakenly left out the important bit: I meant to say find torque values for the engine mount bolts to the firewall. They go through composite structure and it SHOULD give anyone pause before just tightening to standard spec. This is a spec not in the manual, you have to ask FD (thought the spec they gave me is in fact just standard spec, just making a point).

I checked the CTSW manual, same thing, not only is thrust angle not mentioned at all, but neither are any instructions regarding the T-Mount or torque on the bolts. Plus there's this tidbit about the engine replacement:

image.png.25fe457527b3161d43fa453c7b60304b.png

Anyways Madhatter, you're a respected person around this forum. So please understand my concern that when you say something like "If it's not in the maintenance manual then it's not significant." That's a potentially dangerous phrase that can be taken out of context by others who read and respect what you have to share, and you incorrectly assume that Flight Design is giving us everything we need to know to maintain their aircraft. They're not. Just like Rotax won't give us their overhaul manuals and some parts will not be sold to you by their distributors without current training. Whatever reasons they may have, the fact is, they're not fully forthcoming. This isn't the standard airworthiness world, and speaking from how I came from other industries... I was DUMBFOUNDED with how much technical data the manufacturers in aircraft are willing to put out.

It absolutely pisses me off when manufacturers withhold, but it's not like this isn't unheard of. Car manufacturers have been going this direction for a while now too (try performing ECU diagnostics if you aren't one of BMW's approved service centers!). Hell, everyone knows how John Deere is too...

I was referring to the engine angle position only, not anything else.

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The bolts through the firewalls are one of those areas that I wouldn't use a typical toque chart without very clear instruction to do so, because of the level of vibration and the criticality of the assembly. With the fact flight design's manual also doesn't say anything about the engine mounting operation and the line about "service centers only", I went and asked in case it was different.

But yes, you use the values in that chart.

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  • 1 month later...

New E prop about a month ago.

It needs to be torqued a few times after installation and a few runs.

Mine runs 5600 WOT, initial climb 5400 with improved climb rate, cruise climb 5200-5300.

I think the "constant speed" effect is not the blades flexing (they are much stiffer than the Neuform) but rather the washout in the blades near the hub.  I think that during climb the center portion of the prop is stalled, and less of it is stalled in cruise.

I was hoping it would run cooler in the climb with the higher rpms, but if anything it runs hotter, making more power in the climb.

Cruise at several rpm choices are very similar to the Neuform, but on a recent trip to the fly-in at Page, my fuel burn was 4.2 instead of 4.6 gph with the Neuform at about the same true airspeeds.

WF

 

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3 hours ago, 207WF said:

I think the "constant speed" effect is not the blades flexing (they are much stiffer than the Neuform) but rather the washout in the blades near the hub.  I think that during climb the center portion of the prop is stalled, and less of it is stalled in cruise.

This was the only thing I could think of, also.  It would be nice to hear what happens from an aerodynamicist as I am not one.  

I can't wait to get my plane back from annual!

 

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