Prop Diameter


Mark Ewart
 

Looking into an MT C/S prop for my project.  What is the real world (hard landing gear flex) maximum diameter prop that can be used on a Cozy MKIV?

Thanks,
Mark Ewart
Plans #1341


Marc J. Zeitlin
 

Mark Ewart wrote:

Looking into an MT C/S prop for my project.

Why?

What is the real world (hard landing gear flex) maximum diameter prop that can be used on a Cozy MKIV?

It will depend on your particular installation - some folks have (IMO, with poor judgement) cut their main gear legs shorter to increase deck angle on the ground, while some have 8" prop extensions and some have shorter extensions. Some have kept the nose strut as fabricated and not cut it per the plans (better solution to deck angle than cutting the main gear legs).

HOWEVER, per the back page of the plans, the maximum recommended prop diameter is 70". I don't know that I've ever seen a 70" prop on a COZY MKIV, although there probably are a few - the standard Catto and Hertzler props are 66" and 68" diameters, respectively, IIRC.
 
--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


Mark Ewart
 

Marc,

 

Thank you for your reply.

 

To fill in the blanks:

Nose gear leg left full length (to address deck angle) and assembly moved forward as dictated to maintain plans FS position of nose wheel axle when retracted.

 

Main gear legs per plan.

 

Planning for 8” prop extension for cleaner aerodynamics into prop.

 

As to WHY?

 

 

This is the limited data set I use to form my opinion:

My mission profile for the Cozy MKIV is 90% or more usage for long distance travel (>1000 miles) when my wife retires. We're gonna see as much of this country as we can. As a package deal that puts 420# in the front seat for the vast majority of use. My logic is to use weight to move the CG aft when justified by reducing weight forward of the CG and/or increasing weight aft of the CG. Aft CG (within limits) is a plus.

 

A C/S prop will move the CG aft and improve takeoff performance with the penalty of increased empty weight, complexity, and cost. The added cost (≈10% increase in the overall expense of building this project) and complexity have been deemed acceptable for us. The ramifications of increased empty weight is at this point too unquantifiable (is that a word?) to form an opinion.

 

For context, our Archer II (that I learned to fly in) is modified with a C/S prop and I like it. This is not an educated opinion because I have not flown anything else to compare to. Other PA28/C172 pilots invariably comment favorably on its performance compared to their own aircraft even with 1800 hours on the engine.

 

A longer prop extension will enhance this effect hence the current plan for an 8” extension. What are the undesirable effects of a longer extension?


DOH, I didn't think to scan the back cover when I digitized my plans.

 

Hope this provides additional information to use to educate me further.

 

Thanks Marc,

 

Mark Ewart

Plans #1371

 

 

 


ns1jab@...
 

Mark,

 

As someone who has a CS prop on a Cozy, I can tell you without any hesitation it is simply NOT worth the expense, both in upfront cost as well as maintenance.  The plans built, 180hp, fixed pitch Cozy that I fly next to all the time has ZERO problem climbing out of any airport I can get us in to.  That INCLUDES Leadville, CO on hot day, and he had a large passenger with him.  Build it light.  Build it simple.  Enjoy it forever.

 

-John Basol

N204TF

 

From: canard-aviators@canardzone.groups.io <canard-aviators@canardzone.groups.io> On Behalf Of Mark Ewart
Sent: Wednesday, July 14, 2021 4:26 PM
To: canard-aviators@canardzone.groups.io
Subject: Re: [c-a] Prop Diameter

 

Marc,

 

Thank you for your reply.

 

To fill in the blanks:

Nose gear leg left full length (to address deck angle) and assembly moved forward as dictated to maintain plans FS position of nose wheel axle when retracted.

 

Main gear legs per plan.

 

Planning for 8” prop extension for cleaner aerodynamics into prop.

 

As to WHY?

 

 

This is the limited data set I use to form my opinion:

My mission profile for the Cozy MKIV is 90% or more usage for long distance travel (>1000 miles) when my wife retires. We're gonna see as much of this country as we can. As a package deal that puts 420# in the front seat for the vast majority of use. My logic is to use weight to move the CG aft when justified by reducing weight forward of the CG and/or increasing weight aft of the CG. Aft CG (within limits) is a plus.

 

A C/S prop will move the CG aft and improve takeoff performance with the penalty of increased empty weight, complexity, and cost. The added cost (≈10% increase in the overall expense of building this project) and complexity have been deemed acceptable for us. The ramifications of increased empty weight is at this point too unquantifiable (is that a word?) to form an opinion.

 

For context, our Archer II (that I learned to fly in) is modified with a C/S prop and I like it. This is not an educated opinion because I have not flown anything else to compare to. Other PA28/C172 pilots invariably comment favorably on its performance compared to their own aircraft even with 1800 hours on the engine.

 

A longer prop extension will enhance this effect hence the current plan for an 8” extension. What are the undesirable effects of a longer extension?


DOH, I didn't think to scan the back cover when I digitized my plans.

 

Hope this provides additional information to use to educate me further.

 

Thanks Marc,

 

Mark Ewart

Plans #1371

 

 

 


Marc J. Zeitlin
 

Mark Ewart wrote: 

My mission profile for the Cozy MKIV is ... A C/S prop will ...


So all of your logic is sound - wanting more weight aft to balance the two larger folks in the front seat is ONE method for achieving your goal. However, as John Basol points out, the C/S prop, unless you have some extremely specific need that only a C/S prop will fill, is not cost or maintenance effective on our planes.

Here's what I'LL tell you to do in order to deal with the larger front seat weight - leave your canard with the larger, original span (147" vs. 141" as modified) and move your main axles forward by 1", as well as moving your CG RANGE forward by 1.5" (96" to 100.5"). This will put you more toward the center of the CG range when fully loaded in the front seat, meaning that you'll need a fair amount more ballast when solo, but will save substantial weight (the difference between the C/S and fixed prop) and complexity/cost/maintenance. The axles being 1" further forward will make rotation easier when at forward CG's and will ease nose "slap-down" on landing in the same configuration.

WAY simpler, cheaper, lighter, and less work.

A longer prop extension will enhance this effect hence the current plan for an 8” extension. What are the undesirable effects of a longer extension?


If it's too long (and it's not clear what "too long" is, but the longest I've seen on any canard that isn't a race plane is 8") is that the concentricity/runout of the engine/extension/prop can get difficult to achieve, and the prop tips get that much closer to the ground on rotation/landing.

So if what you are actually after is a CG range change and more front seat weight capacity, a C/S prop isn't the optimal way to achieve that, IMO.

--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


Mark Ewart
 

John & Marc,

Thank you for your wisdom.  It's good to have real world input.

Marc,

    ...leave your canard with the larger, original span...
    ...as well as moving your CG RANGE forward by 1.5" (96" to 100.5").

Fairly straightforward, just cut and paste outboard of the spar caps I presume? Do I leave the elevators at plans length or extend them also?

    ...move your main axles forward by 1"...

Definitely not so straightforward. That shift is ≈ 2.2° and a shift of ≈ 0.350” at the ends of the threaded shafts going through the attach tabs. Grinding the tabs off and redoing is possible, but highly undesirable especially considering I already have molded the gear leg fairings around the gear legs. Moving the bulkhead mounting points would leave them not parallel (misaligned by said ≈ 2.2°) to the bulkheads. Also doable but undesirable.

What do you think about building up the leading edge of the gear leg with wing spar roving (parallel to the gear leg axis and extending up onto the gear leg some appropriate distance) as required to form a solid base for moving the axle forward 1” and then rewrapping the area with the plans gear wrap schedule?

Any other suggestions?

Mark Ewart

Plans #1371


Mark Ewart
 

John & Marc,

Thank you for your wisdom.  It's good to have real world input.

Marc,

    ...leave your canard with the larger, original span...
    ...as well as moving your CG RANGE forward by 1.5" (96" to 100.5").

Fairly straightforward, just cut and paste outboard of the spar caps I presume? Do I leave the elevators at plans length or extend them also?

    ...move your main axles forward by 1"...

Definitely not so straightforward. That shift is ≈ 2.2° and a shift of ≈ 0.350” at the ends of the threaded shafts going through the attach tabs. Grinding the tabs off and redoing is possible, but highly undesirable especially considering I already have molded the gear leg fairings around the gear legs. Moving the bulkhead mounting points would leave them not parallel (misaligned by said ≈ 2.2°) to the bulkheads. Also doable but undesirable.

What do you think about building up the leading edge of the gear leg with wing spar roving (parallel to the gear leg axis and extending up onto the gear leg some appropriate distance) as required to form a solid base for moving the axle forward 1” and then rewrapping the area with the plans gear wrap schedule?

Any other suggestions?

Mark Ewart

Plans #1371


Marc J. Zeitlin
 

Mark Ewart wrote:
 
    ...leave your canard with the larger, original span...
    ...as well as moving your CG RANGE forward by 1.5" (96" to 100.5").

Fairly straightforward, just cut and paste outboard of the spar caps I presume?

Yep. Scarf on an extra 3" between the constant chord section and the shaped tip. Chapter 10, Page 1, Figure 1 - you can see that Nat changed the original 11" outboard section to 8" after the span reduction - just increase that back to 11".
 
Do I leave the elevators at plans length or extend them also?

If you extend them, they'll be slightly more effective, so unless it's a nightmare to do so, I'd extend them 3" as well.
 
    ...move your main axles forward by 1"...

Definitely not so straightforward...

And not as critical - the takeoff roll will be slightly longer if you don't do this, and it'll be harder to hold the nose up off the ground on landing. But this is not a critical issue from a flight safety standpoint, as long as you recognize the takeoff roll question (which you'll have tested during Phase I in any case).

What do you think about building up the leading edge of the gear leg with wing spar roving (parallel to the gear leg axis and extending up onto the gear leg some appropriate distance) as required to form a solid base for moving the axle forward 1” and then rewrapping the area with the plans gear wrap schedule?

That's a very interesting idea, and could probably work. If you have the distance to do that below the existing gear leg fairing and you can make a gradual transition. 1" is not a whole lot.

--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


Ryszard Zadow
 

I believe the original post was about adding an constant speed MT.. 

<It's good to have real world input.>

Allow me to add some "real world" input. For the past few years RAFE has been flying a Speed Canard with a constant speed prop. I've got about 150 hours in it now. The difference in take off and climb performance is DRAMATIC, and translates directly to SAFETY. All of us EZ people want to brag about how fast we go and therefore we compromise our take off and climb performance in preference to better cruise speeds. Some to the point that watching them take off and climb makes me cringe! Ever seen Klaus depart in his Varieze,

Flying the SC with an MT on the back has made me a believer and we're on the hunt for an MT for the RAFE Viggen, and aircraft that really needs better takeoff and climb., In fact if I can find one for one of our LongEZ's we'd put it on that one too. 

Surprisingly the CS MT also helps in landing performance. The SC doesn't have a speed brake. When you push the prop control forward you can actually feel the aircraft decelerate when the blades go flat. It will fly the tightest, steepest approach you'll ever see in a tandem seat canard. I demonstrate this to our students just because it's fun, but have to remind them their EZ will not do that. We fly our patterns with 10-12 inches of manifold pressure to simulate the longer, flatter approach of a EZ . 

The only downside is cost , maintenance and the threat of FOD. We spent $5K getting ours overhauled and repaired after a FOD strike about a year ago.  Anything that comes off a pusher goes through the prop therefore you have to be very cognizant of your fasteners. The SC has mostly camlocs but it was not a camloc that cause the FOD. We see camloc damage to props a lot but every notice camlocs aren't falling off standard category aircraft much? My Baron has camlocs. I've never lost one. For some reason people don't go through the trouble to properly fit and install camlocs on their EZs and then blame the camloc when they fall out and strike their prop. 

<WAY simpler, cheaper, lighter, and less work>

After reading about all the suggested work to modify the original posters airplane,  it might seem cheaper, definitely lighter but he does need the weight back there anyway, A lot less work? My thought is it would be whole lot less work to bolt a CS MT prop, governor and controls than do all that. It won't make you faster but your EZ will climb like an airplane should and that makes the difference in clearing that obstacle or not. Getting into that shorter field or not (Rough River) and getting you the power to get out of the slow, high sink rate spot you got yourself into trying to get into the shorter field or steeper approach. Not to mention it gets you higher into more comfortable cooler air faster where you can level off and cruise at the high speeds you brag about. 

If you don't believe me come out and take a flight in RAFE's Speed Canard.

RyZ 
 

On Monday, July 19, 2021, 11:06:39 AM CDT, Marc J. Zeitlin <marc.j.zeitlin@...> wrote:


Mark Ewart wrote:
 
    ...leave your canard with the larger, original span...
    ...as well as moving your CG RANGE forward by 1.5" (96" to 100.5").

Fairly straightforward, just cut and paste outboard of the spar caps I presume?

Yep. Scarf on an extra 3" between the constant chord section and the shaped tip. Chapter 10, Page 1, Figure 1 - you can see that Nat changed the original 11" outboard section to 8" after the span reduction - just increase that back to 11".
 
Do I leave the elevators at plans length or extend them also?

If you extend them, they'll be slightly more effective, so unless it's a nightmare to do so, I'd extend them 3" as well.
 
    ...move your main axles forward by 1"...

Definitely not so straightforward...

And not as critical - the takeoff roll will be slightly longer if you don't do this, and it'll be harder to hold the nose up off the ground on landing. But this is not a critical issue from a flight safety standpoint, as long as you recognize the takeoff roll question (which you'll have tested during Phase I in any case).

What do you think about building up the leading edge of the gear leg with wing spar roving (parallel to the gear leg axis and extending up onto the gear leg some appropriate distance) as required to form a solid base for moving the axle forward 1” and then rewrapping the area with the plans gear wrap schedule?

That's a very interesting idea, and could probably work. If you have the distance to do that below the existing gear leg fairing and you can make a gradual transition. 1" is not a whole lot.

--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


skovbjerg
 

Obviously, results vary but I do not think that  the SC data point should reflect on LEZ judgement calls. The SC is a canard, but speedy it is not and if the lack of speed translates to lack of T/o performance as well, I see why you would want a c/s prop on it. 
See, if I fly solo in my CozyIII I can clear the 50’ fence in less than 2,000 ft on a standard day. That is less than I will need to land…. This should be comparable to LEZ performance. All that I heard of with c/s props on LEZ is that there is a loss of top end speed. 
Jay

On Jul 19, 2021, at 11:38, Ryszard Zadow <ryszardzadow@...> wrote:


I believe the original post was about adding an constant speed MT.. 

<It's good to have real world input.>

Allow me to add some "real world" input. For the past few years RAFE has been flying a Speed Canard with a constant speed prop. I've got about 150 hours in it now. The difference in take off and climb performance is DRAMATIC, and translates directly to SAFETY. All of us EZ people want to brag about how fast we go and therefore we compromise our take off and climb performance in preference to better cruise speeds. Some to the point that watching them take off and climb makes me cringe! Ever seen Klaus depart in his Varieze,

Flying the SC with an MT on the back has made me a believer and we're on the hunt for an MT for the RAFE Viggen, and aircraft that really needs better takeoff and climb., In fact if I can find one for one of our LongEZ's we'd put it on that one too. 

Surprisingly the CS MT also helps in landing performance. The SC doesn't have a speed brake. When you push the prop control forward you can actually feel the aircraft decelerate when the blades go flat. It will fly the tightest, steepest approach you'll ever see in a tandem seat canard. I demonstrate this to our students just because it's fun, but have to remind them their EZ will not do that. We fly our patterns with 10-12 inches of manifold pressure to simulate the longer, flatter approach of a EZ . 

The only downside is cost , maintenance and the threat of FOD. We spent $5K getting ours overhauled and repaired after a FOD strike about a year ago.  Anything that comes off a pusher goes through the prop therefore you have to be very cognizant of your fasteners. The SC has mostly camlocs but it was not a camloc that cause the FOD. We see camloc damage to props a lot but every notice camlocs aren't falling off standard category aircraft much? My Baron has camlocs. I've never lost one. For some reason people don't go through the trouble to properly fit and install camlocs on their EZs and then blame the camloc when they fall out and strike their prop. 

<WAY simpler, cheaper, lighter, and less work>

After reading about all the suggested work to modify the original posters airplane,  it might seem cheaper, definitely lighter but he does need the weight back there anyway, A lot less work? My thought is it would be whole lot less work to bolt a CS MT prop, governor and controls than do all that. It won't make you faster but your EZ will climb like an airplane should and that makes the difference in clearing that obstacle or not. Getting into that shorter field or not (Rough River) and getting you the power to get out of the slow, high sink rate spot you got yourself into trying to get into the shorter field or steeper approach. Not to mention it gets you higher into more comfortable cooler air faster where you can level off and cruise at the high speeds you brag about. 

If you don't believe me come out and take a flight in RAFE's Speed Canard.

RyZ 
 
On Monday, July 19, 2021, 11:06:39 AM CDT, Marc J. Zeitlin <marc.j.zeitlin@...> wrote:


Mark Ewart wrote:
 
    ...leave your canard with the larger, original span...
    ...as well as moving your CG RANGE forward by 1.5" (96" to 100.5").

Fairly straightforward, just cut and paste outboard of the spar caps I presume?

Yep. Scarf on an extra 3" between the constant chord section and the shaped tip. Chapter 10, Page 1, Figure 1 - you can see that Nat changed the original 11" outboard section to 8" after the span reduction - just increase that back to 11".
 
Do I leave the elevators at plans length or extend them also?

If you extend them, they'll be slightly more effective, so unless it's a nightmare to do so, I'd extend them 3" as well.
 
    ...move your main axles forward by 1"...

Definitely not so straightforward...

And not as critical - the takeoff roll will be slightly longer if you don't do this, and it'll be harder to hold the nose up off the ground on landing. But this is not a critical issue from a flight safety standpoint, as long as you recognize the takeoff roll question (which you'll have tested during Phase I in any case).

What do you think about building up the leading edge of the gear leg with wing spar roving (parallel to the gear leg axis and extending up onto the gear leg some appropriate distance) as required to form a solid base for moving the axle forward 1” and then rewrapping the area with the plans gear wrap schedule?

That's a very interesting idea, and could probably work. If you have the distance to do that below the existing gear leg fairing and you can make a gradual transition. 1" is not a whole lot.

--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


Ryszard Zadow
 

Exceptions don’t change the rule and there’s always that one nay-sayer. 

As I said, if you don’t believe it come fly the aircraft. 

RZ 

On Jul 19, 2021, at 20:24, skovbjerg <skovbjerg@...> wrote:


Obviously, results vary but I do not think that  the SC data point should reflect on LEZ judgement calls. The SC is a canard, but speedy it is not and if the lack of speed translates to lack of T/o performance as well, I see why you would want a c/s prop on it. 
See, if I fly solo in my CozyIII I can clear the 50’ fence in less than 2,000 ft on a standard day. That is less than I will need to land…. This should be comparable to LEZ performance. All that I heard of with c/s props on LEZ is that there is a loss of top end speed. 
Jay

On Jul 19, 2021, at 11:38, Ryszard Zadow <ryszardzadow@...> wrote:


I believe the original post was about adding an constant speed MT.. 

<It's good to have real world input.>

Allow me to add some "real world" input. For the past few years RAFE has been flying a Speed Canard with a constant speed prop. I've got about 150 hours in it now. The difference in take off and climb performance is DRAMATIC, and translates directly to SAFETY. All of us EZ people want to brag about how fast we go and therefore we compromise our take off and climb performance in preference to better cruise speeds. Some to the point that watching them take off and climb makes me cringe! Ever seen Klaus depart in his Varieze,

Flying the SC with an MT on the back has made me a believer and we're on the hunt for an MT for the RAFE Viggen, and aircraft that really needs better takeoff and climb., In fact if I can find one for one of our LongEZ's we'd put it on that one too. 

Surprisingly the CS MT also helps in landing performance. The SC doesn't have a speed brake. When you push the prop control forward you can actually feel the aircraft decelerate when the blades go flat. It will fly the tightest, steepest approach you'll ever see in a tandem seat canard. I demonstrate this to our students just because it's fun, but have to remind them their EZ will not do that. We fly our patterns with 10-12 inches of manifold pressure to simulate the longer, flatter approach of a EZ . 

The only downside is cost , maintenance and the threat of FOD. We spent $5K getting ours overhauled and repaired after a FOD strike about a year ago.  Anything that comes off a pusher goes through the prop therefore you have to be very cognizant of your fasteners. The SC has mostly camlocs but it was not a camloc that cause the FOD. We see camloc damage to props a lot but every notice camlocs aren't falling off standard category aircraft much? My Baron has camlocs. I've never lost one. For some reason people don't go through the trouble to properly fit and install camlocs on their EZs and then blame the camloc when they fall out and strike their prop. 

<WAY simpler, cheaper, lighter, and less work>

After reading about all the suggested work to modify the original posters airplane,  it might seem cheaper, definitely lighter but he does need the weight back there anyway, A lot less work? My thought is it would be whole lot less work to bolt a CS MT prop, governor and controls than do all that. It won't make you faster but your EZ will climb like an airplane should and that makes the difference in clearing that obstacle or not. Getting into that shorter field or not (Rough River) and getting you the power to get out of the slow, high sink rate spot you got yourself into trying to get into the shorter field or steeper approach. Not to mention it gets you higher into more comfortable cooler air faster where you can level off and cruise at the high speeds you brag about. 

If you don't believe me come out and take a flight in RAFE's Speed Canard.

RyZ 
 
On Monday, July 19, 2021, 11:06:39 AM CDT, Marc J. Zeitlin <marc.j.zeitlin@...> wrote:


Mark Ewart wrote:
 
    ...leave your canard with the larger, original span...
    ...as well as moving your CG RANGE forward by 1.5" (96" to 100.5").

Fairly straightforward, just cut and paste outboard of the spar caps I presume?

Yep. Scarf on an extra 3" between the constant chord section and the shaped tip. Chapter 10, Page 1, Figure 1 - you can see that Nat changed the original 11" outboard section to 8" after the span reduction - just increase that back to 11".
 
Do I leave the elevators at plans length or extend them also?

If you extend them, they'll be slightly more effective, so unless it's a nightmare to do so, I'd extend them 3" as well.
 
    ...move your main axles forward by 1"...

Definitely not so straightforward...

And not as critical - the takeoff roll will be slightly longer if you don't do this, and it'll be harder to hold the nose up off the ground on landing. But this is not a critical issue from a flight safety standpoint, as long as you recognize the takeoff roll question (which you'll have tested during Phase I in any case).

What do you think about building up the leading edge of the gear leg with wing spar roving (parallel to the gear leg axis and extending up onto the gear leg some appropriate distance) as required to form a solid base for moving the axle forward 1” and then rewrapping the area with the plans gear wrap schedule?

That's a very interesting idea, and could probably work. If you have the distance to do that below the existing gear leg fairing and you can make a gradual transition. 1" is not a whole lot.

--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


Marc J. Zeitlin
 

Ryszard Zadow wrote:

Exceptions don’t change the rule and there’s always that one nay-sayer.

Not surprisingly, I'm with Cookie on this one. While I agree that if the C/S prop is designed correctly for the aircraft in question (and I've flown two canards - a Berkut and a COZY MKIV - where they were, and one - a COZY MKIV where it wasn't) that the takeoff performance will be somewhat better than the SAME aircraft with a fixed pitch, middle design (not climb, not cruise, but in-between) propeller, the top end is almost always worse, and sometimes substantially worse. Also, the one prop on the COZY MKIV that wasn't tuned correctly for the plane was a total POS, and it was an MT electric prop. I don't extrapolate to all MT props.

So the issue here is not "do you get better takeoff performance with a good C/S prop over a good fixed pitch prop" (which I certainly grant that you do), but "is the marginally takeoff and climb better performance worth the huge increase in initial and ongoing cost, as well as downtime for additional maintenance". In no way was the better takeoff/climb performance in either the Berkut or COZY MKIV (somewhat noticeable, but not breathtaking, by any stretch of the imagination) worth it, in my opinion. Obviously, opinions can vary on this subject, as there are folks that have installed C/S props.

I also agree that the C/S prop acts as a barn door for approaches, and is excellent for steepening the approach angle to allow for better touchdown point control. But good airspeed control, dual rudder usage, landing brake usage and slips provide exactly the same capability, and they're all free and require no maintenance, either.

As I said, if you don’t believe it come fly the aircraft.

Unless you have another Speed Canard with exactly the same engine and a correctly designed fixed pitch prop, flying it will tell us exactly nothing, as there's nothing to compare it to.

--
Marc J. Zeitlin                      marc_zeitlin@...
                                            http://www.cozybuilders.org/
Copyright © 2021                     Burnside Aerospace


Ryszard Zadow
 

< the takeoff performance will be somewhat better than the SAME aircraft with a fixed pitch, middle design (not climb, not cruise, but in-between) >

This comparison is inadequate because people don’t have those kinds of props. They have cruise props thus their takeoff and climb are anemic compared to that of the same aircraft with the horsepower a CS prop would give it. You can’t say the takeoff and climb would only be marginally better if the fixed pitch prop is marginal for takeoff and climb to begin with. Let’s compare apples to apples please and not twist things to fit your argument. In almost 40 years of Canard flying Ive yet to meet an EZ driver that brags about his climb prop, lol.

There are only 5 Speed Canards in the US. One is Standard Category (ours) the rest are Experimental category. I’ve tracked them all down looking for parts. All have the same engine. Keep in mind despite being Exp Cat they came out of a factory therefore extremely similar. Three of the Exp Cat SC still have their MTs. The other one was reluctant (read too cheap) to pay for overhauling his MT so he installed a Catto. He YEARNS for his MT back because of the terrible takeoff and climb he now gets. (Yes that only adds up to four, the last one is wrecked)

< Unless you have another Speed Canard with exactly the same engine and a correctly designed fixed pitch prop, flying it will tell us exactly nothing, as there's nothing to compare it to.>

Now you’re bring a hypocrite. Did the Berkut and Cozy you flew have “correctly designed” fixed pitch props you could compare against? My guess is not but this sounds good on a forum post. What is a “correctly designed” prop anyway? Are you implying some prop makers are designing props incorrectly? Ivo maybe..but I wouldnt say he’s designing them incorrectly, it’s just I haven’t had good experiences with them but lots of people like them and that’s ok for them amd most people, unless you’re on this forum. Then, anything that doesn’t align with one or two individuals “expert” opinion is wrong.

I do a lot of the test flying on stuff that comes out of the Jetguys shop and others. I have the privilege of flying more different EZs than most people. I do almost all the instructing in the Speed Canard. That’s not pontificating on a keyboard, that’s actually doing it!

A canard with a MT makes a great airplane even better. But go ahead and live in y’all’s little world. It’s safer in there. No more time to type. Im headed to OSH… in an airplane.. that actually flies. It amazes me how blessed I am that I get to fly something …every … day. hardly a day goes by that i’m not flying something. One day maybe someone will consider that real world experience. :)

RyZ

On Jul 19, 2021, at 20:57, Marc J. Zeitlin <marc.j.zeitlin@gmail.com> wrote:

the takeoff performance will be somewhat better than the SAME aircraft with a fixed pitch, middle design (not climb, not cruise, but in-between)


Marc J. Zeitlin
 

Ryszard Zadow wrote:

They have cruise props thus their takeoff and climb are anemic compared to that of the same aircraft with the horsepower a CS prop would give it.

Having worked on approximately 75 - 90 individual canards via Pre-Buys, Condition Inspections, or other work, and having flown somewhere around 15 of them, I can tell you that most of the canards have props intermediate between cruise and climb (75%, maybe), a very few have climb props (5%), and the rest (20% or so) have cruise props. This may or may not be by the choice of the builder/owner, but it's about what I've seen and measured.

You can’t say the takeoff and climb would only be marginally better if the fixed pitch prop is marginal for takeoff and climb to begin with.

Since your supposition of marginal takeoff and climb with fixed pitch props is incorrect, at least with respect to the population selection of canards on which I've worked, then your conclusion will be incorrect as well. So anything that follows FROM that conclusion will be incorrect.
 
He YEARNS for his MT back because of the terrible takeoff and climb he now gets.

It would be a good experiment to measure the length of the takeoff roll for each, as well as the climb rates. And it would be good to determine whether or not the Catto prop on the SC with the fixed pitch prop is, in fact, a cruise, climb, or in-between prop. What the owner years for is immaterial - it's the #'s that matter.
 
Now you’re bring a hypocrite. Did the Berkut and Cozy you flew have “correctly designed” fixed pitch props you could compare against?

I can't say for the Berkut, because I haven't flown enough of them, but its performance, taking off out of Meadowlake in Colorado Springs was not substantially better than my COZY MKIV taking off out of Meadowlake, with the same O-360 engine. With respect to the COZY MKIV with the C/S prop in which I've flown that had a decent engine/prop combination, the takeoff/climb performance out of Compton, near LA, was a bit better than my COZY MKIV with a Hertzler fixed pitch prop that's in between climb/cruise, but not eye-poppingly so. And the same plane, taking off out of Tehachapi, at 4000 ft. MSL, was also not substantially better than my plane taking off out of Tehachapi - maybe a 10% shorter takeoff roll. Climb performance, maybe 10% - 20% better.

What is a “correctly designed” prop anyway?

One that fulfills the requirements of the owner of the plane. If one wants a cruise prop and gets one, then it's "correctly designed". If one wants an intermediate prop, and gets one, then it's correctly designed. If one wants a climb prop, and gets one, then it's correctly designed. If one wants something and DOESN'T get it, then it doesn't meet its design criteria.

I have a Hertzler Silver Bullet prop on my COZY MKIV. It will turn about 2400 - 2450 RPM static, about 2500 RPM in the climb, and about 2750 - 2780 at max power at altitude (8500 ft. or so). I can climb out at over 1000 fpm when at MGW at SL, which is more than adequate for any airport I've ever wanted to fly into, and I can fly into and out of 2000 ft. paved strips (and do). For me, this is a correctly designed prop, being a very good compromise between climb, cruise, cost, and maintenance needs.

As I have said previously, there's no "right answer" here - there's only the tradeoff between slightly better takeoff/climb performance and cost/maintenance. Everyone gets to decide for themselves if they want to purchase a 16 lb. prop that costs $2K, will last 5 - 10 years without needing an overhaul and when it does, it will cost $400 and take a week or two to get back, or whether they want to spend $15K for a prop that weighs 2X - 3X as much, spend $5K per blade for repairs, will need maintenance on a regular basis, and will be slower at the top end, where we spend most of our time.

Some folks will choose one - 95% or more of the canard population (at least VE/LE/COZY/E-Racer/Berkut - not Velocity) will choose a fixed pitch prop, but for the 5% that want the advantage that the C/S prop gives and are willing to pay for it - fine - I'm not claiming their wrong - just that they have different criteria than I do, and I was pointing out some options for the OP so that he could consider them.

Are you implying some prop makers are designing props incorrectly?

Well, sure - some props are a lot better than others, from a performance standpoint - that's the objective reality. Hertzler and Catto are at the top of the game. There are a few others that are good as well, and a bunch that are sub-optimal for canards.

I do a lot of the test flying on stuff that comes out of the Jetguys shop and others. I have the privilege of flying more different EZs than most people. I do almost all the instructing in the Speed Canard. That’s not pontificating on a keyboard, that’s actually doing it!

Bully for you. Your point is what? That you know what prop is best for everyone, whatever their mission or needs may be? That because YOU are willing to spend the extra money and time to maintain a C/S prop, that everyone should be?

All I did was give the OP options. They can then choose the path that's right for them.

--
Marc J. Zeitlin                      marc_zeitlin@...
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