Kent's Long-EZ project

[Kent Ashton]

My prop drawing is coming along.  Here's my approach:

 

- See what props others have used.  For my 160 HP engine--a 65X79" chord pitch 2-blade seems about right.

 

- Figure out the airfoils and shape -  I am trying to make a Hertzler-style prop from pics found on the web (pics 1, 5).  Yes, this requires a lot of guesses  :-)  I copied the blade planform from a friend's prop and took some chord measurements and made some measurements on one of the pictures (pic 5).  I used airfoils that seem to match the web pictures.  At the tip, FX84W097, at Station 5 FS84W140, at Station 3 FX84W218.  The tip and Station 5 shapes are very close to the pics.  These airfoils have a maximum thickness about mid-span compared to the usual Clark-Y and RAF airfoils.  The bottoms are not quite as flat at the Clark-Y and RAF.  You can view them on airfoiltools.com.   

 

-Using a 79" pitch at 75% span, RPM and speed, I worked backwards to a chord angle and compared the angle to my friend's prop and the pics.  Using chord angle measurements from my friend's prop, I repitched those numbers to work with my new pitch at the 75% station.

 

-Knowing the chord angles at each station and the horizontal footprint of the chords from the planform drawing (pic 3), I trigged out the chord length at each station.  With the chord length at each station known and the airfoil ordinates for stations 10, 5, and 3, I made a spreadsheet that interpolated the ordinates for the other stations and scaled them up to the chord lengths.

 

-Then I imported each set of ordinates into a CAD program and printed out the airfoil at each station (pic 2 is an example)  Pic 4 shows the airfoils plotted at the desired angles.  Hey, it looks like a prop, eh?  Next step is to glue each airfoil to some wood and make jigs for the prop-carver machine.  Fun!

[Kent Ashton]

I see today that Wicks has a sale on Hartwell latches ($20!).  You might not think that a Hartwell latch on the side of an airplane would leak a whole lot of air but in the winter, it's enough to freeze my hand (pic 2).  I don't fly that much in cold weather so I made a velcro-bordered patch I put on the inside which stops most of the draft.

 

On the EZ, I cut out a wedged-shaped door that seals much better.  The door side with the hinge isn't tapered but some compressible foam seals it.  The door is held closed by the key latch or a simple inside latch.  The disadvantage is that firemen can't open the canopy easily as with the Hartwell.  Note to self: unlock before crashing.

 

I finally received my last prop materials--Weldwood Plastic Resin glue was highly recommended by some of the well-known builders--and will start gluing up boards shortly.

[Kent Ashton]

I discussed my own problems with winglet alignment earlier in this thread and thought I would post a couple pics and a DXF drawing of the alignment jig I used to check and correct the alignment.  By studying the plans and body lines, I established that the winglet chord is supposed to be parallel to the aircraft centerline.  I recommend you make one and use it when going through the plans method for winglet alignment.

 

Add the small triangle pieces top and bottom so you can flip it to use on the opposite winglet.

WingletAlignJig.dxf

[Voidhawk9]

By studying the plans and body lines, I established that the winglet chord is supposed to be parallel to the aircraft centerline.

That's a nice nugget of information, as is the alignment jig!

[TMann]

I would have thought a one degree incidence inboard.

Interesting.

 

I like the Jig Idea.

[Kent Ashton]

I would have thought a one degree incidence inboard.

 

Just to check, I drew it out with a CAD program using Cozy F.S./B.L stations.  (pic)  The plans result in a winglet chord just a touch (about .15") wider than the CAD program draws using the same stations but both chords are parallel to the fuselage.  As I recall, an EZ is also parallel.

[Kent Ashton]

Glass-reinforced RTV sheet:  I find several uses for this stuff.  Make it by taking a square foot or so of BID laid out on some plastic sheet, goop on high temp RTV from the home store, squeegee out the RTV with an old credit card, flip and make sure the other side of the BID is thoroughly wetted.  Put another piece of plastic over the mess and roller it flat with a rolling pin or piece of PVC pipe.

 

Uses I have found for it:

-to secure wires to the engine mount tubes, cut a 1" X 2" piece, sandwich the wires in it and tie-wrap to the mount tube.  Way easier than Adel clamps. (pic)

-engine baffles

-cut-to-shape baffles for around alternators and irregular curves of the engine case

-baffles around oil coolers

-to make protective wrap for firewall penetrations

 

Some pics of firewall penetrations here

http://www.jasonbeaver.com/rv7/2012/03/sealed-firewall-passthroughs.html

 

BTW, wet sheet can be cut to shape (make paper patterns, first) and used for cylinder baffles.  It sticks well to the fins.  For that sort of thing I use the aluminum-colored RTV from the hardware stores.  Blends with the engine paint a little better.  :-)

[macleodm3]

That looks very EZ.  What are the properties of the glass-reinforced RTV that make this worth doing?  Does is remain flexible for a long time?  Do you know what the upper temperature limits are for this?

Most of us have lots of little leftover scraps of BID.  Thanks!

[Kent Ashton]

That looks very EZ.  What are the properties of the glass-reinforced RTV that make this worth doing?  Does is remain flexible for a long time?  Do you know what the upper temperature limits are for this?

Most of us have lots of little leftover scraps of BID.  Thanks!

 

Used as a wrap, it'll remain flexible indefinitely.    The homestore aluminum-colored RTV does not seem to deteriorate on the cylinders so I conclude all the RTVs are pretty heat resistant.  I have used some of the store-bought red silicone baffle material up against exhaust pipes where they exit the baffles.  It eventually deteriorates but it lasts for a long time.

[Kent Ashton]

I did not clearcoat my Cozy Zolatone and it does not wear well and gets dirty.  On the EZ, I used a regular clearcoat that is shiny and doesn't look as good either.  Sigh.  A chap from the Cozylist showed me this matte clearcoat.  Good to know about.

 

Cozy: Nat recommended a removable instrument cover top in the plans but I had another idea that turned out to be not-so-bright.  It has really hindered work behind the panel.  I am finally installing an electric nose lift and decided to make the cover.   It's going to be a little problematic getting the cover matched with front of the canopy but I have some ideas.  The rest of it should be easy.

 

Here is an idea for a leather seal around the nose gear lift.  I am already working on the 2nd iteration but you get the idea.

[Kent Ashton]

I did not clearcoat my Cozy Zolatone and it does not wear well and gets dirty.  On the EZ, I used a regular clearcoat that is shiny and doesn't look as good either.  Sigh.  A chap from the Cozylist showed me this matte clearcoat.  Good to know about.

 

Cozy: Nat recommended a removable instrument cover top in the plans but I had another idea that turned out to be not-so-bright.  It has really hindered work behind the panel.  I am finally installing an electric nose lift and decided to make the cover.   It's going to be a little problematic getting the cover matched with front of the canopy but I have some ideas.  The rest of it should be easy.

 

Here is an idea for a leather seal around the nose gear lift.  I am already working on the 2nd iteration but you get the idea.

[Kent Ashton]

I am making a removable instrument cover for the Cozy.  I wish I had done this when I built it; it would have been a piece of cake then.  To refit it afterwards is taking about 15 trips to the airport!  It sure will be nice to be able to pull two pins and work on wiring, though.

[Jon Matcho]

I'll have to make a note to incorporate this modification (or is it part of the Cozy IV plans?)

 

To refit it afterwards is taking about 15 trips to the airport!

I'm repairing another composite door for a Glasair at an airport 45 minutes away. I've forgotten basic tools the last two trips there. I don't know how anyone works on an airplane in most hangars.

[Kent Ashton]

I'll have to make a note to incorporate this modification (or is it part of the Cozy IV plans?)

 

 

I'm repairing another composite door for a Glasair at an airport 45 minutes away. I've forgotten basic tools the last two trips there. I don't know how anyone works on an airplane in most hangars.

 

Yep, the cover was in the Cozy plans.  I don't think EZ plans show a cover but it's definitely a help to have one.  I know what you mean about forgetting tools.  I have ridden my bike to the airport (30 min trip) and forgotten my hangar key on the car key-ring.  :-(

[Jon Matcho]

I have ridden my bike to the airport (30 min trip) and forgotten my hangar key on the car key-ring.  :-(

Ha! Yesterday I only forgot one item, but since I brought the 2 items I forgot from last time I was at least able to make some progress.

[Kent Ashton]

Pitch trim:  Here is a Cozy/EZ pitch trim system using spring wire.  (Cozy- 1/8" wires. EZ 3/32" wires).  The wires are adjusted by a welded-up nut on a threaded rod.  The rod is secured on a bracket on F-22.  In operation, the wires are always pulled forward to give down-elevator trim.  The wires are held in the nut by small retainers, not shown.  It is pretty easy to remove the canard with this setup: unscrew the wire retainers, lift the canard and trim wires out of the nut.

 

Gear down switches:  I put a homemade electric nose lift in the Cozy which did not incorporate switches for a "gear down" and "gear unsafe" warning.  No room to add them to the nose lift so here is what I came up with.  I like the comfort of having a positive "gear down" light.  It is something you can check quickly on final.

[macleodm3]

Pitch trim:  Here is a Cozy/EZ pitch trim system using spring wire.  (Cozy- 1/8" wires. EZ 3/32" wires).  The wires are adjusted by a welded-up nut on a threaded rod.  The rod is secured on a bracket on F-22.  In operation, the wires are always pulled forward to give down-elevator trim.  The wires are held in the nut by small retainers, not shown.  It is pretty easy to remove the canard with this setup: unscrew the wire retainers, lift the canard and trim wires out of the nut.

 

 

Very interesting!  A torsion bar trim spring....   Your spring wire is so long that is does not crack, break, or permanently deform (like the fiberglass trim springs do in some installations).

So... how do you like it?  

 

1.)  Are you able to get full elevator deflection (up and down) with the trim set at full up and down settings?

2.)  Do you have any photos of the actuating mechanism (which I assume is a handle or knob in the IP).

3.)  Any problems with your retainers out at the end of the springs?

4.)  Does this system affect the balance of your elevators?  You've added some weight to the system... does this make the elevators tail heavy?

 

Thanks for sharing your designs.

Edited April 27, 2017 by Andrew Anunson

[Kent Ashton]

I like it pretty well.  I'll add a couple more photos later.  On the EZ i used a small electric motor to actuate the trim (See post #90 in this thread) but it's over-designed.  On the Cozy I have a 1.25"D knob to turn the threaded rod and barely use it once or twice a flight.  These airplanes do not need much trimming compared to say, a CE-172.

 

I can override the springs in any direction.  In the canards I've flown, the trim forces almost always pull the elevator down--or maybe neutral.  There is no case where you need to trim to hold the elevator up.

 

I haven't noticed any ill effects.  In the EZ, I used a different method for mounting the trim springs (See post #73).  It works just as well but acts more like the Davenport fiberglass spring.  That one is probably easier to make with a bit of welding.

Edited April 27, 2017 by Jon Matcho

[Marc Zeitlin]

There is no case where you need to trim to hold the elevator up...

You have obviously not flown an O-540 powered Berkut. They not only can run out of full up trim, but can run out of full up ELEVATOR and still be climbing, depending upon DA and power output :-).

[Kent Ashton]

Getting to work on my prop:  Found some nice maple at a local lumberyard.  Hard maple was desired; I am not sure I got the hard stuff, still, it seems pretty hard.   Glued with Weldwood Plastic glue which the Yahoo prop group seems to like.  Drilled the hub on the mill after trammeling the mill to get it squared up.

 

The bandsaw cut through the blank pretty easily with a 4-TPI blade.  The trickiest part so far is cutting away the excess on the diagonal without botching what will become the blade.  It is easy to get confused about where to cut--you can see where I marked it wrong once (5th pic).  I even glued back a piece I thought I had cut on the wrong side, studied it again and determined that I had cut off the correct side so I had to cut that piece off twice!  Duh.  Fortunately there was enough left to allow that.

 

Waiting for a burr to start with the router table.

[Jon Matcho]

Impressive Kent! I know you've done the research, but I wonder why they favor "plastic glue" versus epoxy.

 

Luckily your brainfart was didn't cost anything. :-)

[Kent Ashton]

Now you might think with one of those prop copier devices, you would go zip, zip, carve away everything that is not a prop and bingo--Your Very Own Prop.  However, I am not sure I will get a prop out of this exercise.  My blades are planned very thin.  I tried to cut them fat with the router to leave room for adjustment but not sure at this point whether I allowed enough.  I'm going to glass them so that'll help.  The question is: test fly it before glassing or just glass it and hope it works? Maybe I will glass the cambered side.  Or maybe the first attempt will be firewood.  It looks very rough at this stage.

 

If I get one good blade out of it, that might allow me to rout a new blank, taking a little more care.

[Jon Matcho]

The question is: test fly it before glassing or just glass it and hope it works? Maybe I will glass the cambered side.  Or maybe the first attempt will be firewood.  It looks very rough at this stage.

 

If I get one good blade out of it, that might allow me to rout a new blank, taking a little more care.

I'm sure you're asking a prop-making forum, but I'll offer that wood to make another is far less expensive than other scenarios...

 

I am thoroughly impressed by all of this nonetheless!

[macleodm3]

Kent,

Well.... you've got your hands full... I'll give you that!  

I may someday enjoy overhauling my Lycoming by myself, but I really don't think I'll ever build my own prop.  If you get good at this, people may buy them from you... isn't this how Catto got started?

 

My Savier prop has birch laminates that are only about 1/6" thick... Klaus also used maple that was 1/4" thick.

What are the advantages / disadvantages of using thick or thin laminates?

[Kent Ashton]

My Savier prop has birch laminates that are only about 1/6" thick... Klaus also used maple that was 1/4" thick.

What are the advantages / disadvantages of using thick or thin laminates?

 

 

Beats me.  I expect the thin laminates are dimensionally more stable.   I did not think about buying 1/4" birch plywood and laminating it until just now.  :-(    I bet that would make a good core.  My Performance Prop 3-blade was plenty stiff even without the glass.  However, from what I read, the core is not too critical for a glassed prop--could maybe even be balsa.   With a little sectioning in the CAD profile, I could use less wood with the birch plywood, too.  Anyway, it appears I'll be able to use this core.  It is getting pretty close on the back side.