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Cruise Deck Angle


Terry
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I have read many times that the Long-Ez cruises with about a 3 deg nose up attitude. Has anyone thought about increasing the wing and canard incidence by3 deg to compensate? However so slight, this would improve the over the nose visibility and slightly reduce the rotation speed. Any constructive thoughts are welcome. I know,I know, changes cost time and money. This would be my 3rd EZ the first 2 being Vari-eze's

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I have read many times that the Long-Ez cruises with about a 3 deg nose up attitude

I on the contary have read that the cruise AOA (measured against upper longeron) is in the range of 1.5º to 2.0º... :confused:

 

There is an article in the one of the CSA newsletters on it - some guy took a smartlevel on board and went flying. I'll look up the reference tonight.

 

Regards,

Henrik

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Marc Zeitlin was playing with this idea in some recent work he was doing to his plane. Last I heard, there was no appreciable differences noted.

 

Marc?

 

It would be interesting to know if there is any difference in the AOI within the canard designs (i.e. Vari/Long/Berkut/Velo/Cozy etc.)

I heard a criticism of the Berkut at one point due to the extra 12 inches between the canard and the wing (when compared to the Long-EZ) that the AOI should have changed as well but was the same.:confused:

I'm no engineer but I would find an opinion about the subject interesting.

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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I have read many times that the Long-Ez cruises with about a 3 deg nose up attitude. Has anyone thought about increasing the wing and canard incidence by3 deg to compensate? However so slight, this would improve the over the nose visibility and slightly reduce the rotation speed. Any constructive thoughts are welcome. I know,I know, changes cost time and money. This would be my 3rd EZ the first 2 being Vari-eze's

in flight the deck angle measured at the longeron is some what dependent on speed. it is really a non issue as it does not change enough that unless you are thinking about it you don't notice it. don't think conventional airplane here the ezes are not even close to the those angles. as for rotation speed it is not dependent on deck angle of the fuselage. while rolling on the ground it is dependent on the angle of attack of the wing relative to the level ground which is dependent on the gear leg lengths. increasing the angle of attack of the wing on the ground helps takeoff distance very little. if increased to much it just causes more drag and and has the reverse effect. a much bigger factor in take off distance is acceleration, getting to rotation speed. the biggest factor I have noticed is weight.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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  • 2 weeks later...

There is an article in the one of the CSA newsletters on it - some guy took a smartlevel on board and went flying. I'll look up the reference tonight.

 

Ever since I wrote that, I have been trying to find out just where I did read about this - and tonight, I quite by accident stumbled across it again. (The reason I could not find it was that the title of the write-up was different from what I thought it should be).

 

I'ts an very thorough article by Tom Staggs presented in CSA newsletter issue 73 page 25 (i.e January 2004) 'Wing Fence Effects'. His measuremenmts show a deck angle of 1.8º at 150 KIAS increasing to 4.1º at 110 KIAS. 3º is found at app. 130 KIAS - so you could be right depending on your cruise speed..

 

Hope this helps - I myself have bookmarked the CSA for doing main gear fairings...

 

Regards

Henrik

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  • 6 months later...

When building the VariEze i was fortunate to be able to confirm three significant considerations ahead of time with several knowledgeable EZ types. I wanted to extend the strakes forward, install the wings level, and lower the cruise angle of attack.

After consulting, I was confident in the extended strakes and level wings also because those were ‘improvements’ that had been included on the LongEZ. But I was kinda shooting in the dark on the cruise attitude.

Along the way I was able to talk alone with one person in particular. He is in fact the one that I would most want to talk to about these things. After discussing the other two mods, I mentioned that I wanted to raise the canard and main wing incidence one degree. He said that was what was done on the LongEZ to get a better cruise angle compared to the VariEze.

I had guessed right. That was valuable info and confirmation to me from one of the horses mouths, but of course it is only hearsay now from me. Each of us gets to do our own research to confirm the validity of internet statements :)

Mine is the only VariEze that I know of flying with the incidence mod. It is what I was after, about the same as the LongEZs I have flown, and about half that of the other VariEzes I have flown.

A carpenters level bubble hot glued on the fuselage wall is useful for a number of quick attitude measurements, like the effect of TE Fences. I have also used an attitude string on the side windows, and a string outside at eye level on the side the canopy. Could probably get some good change info with a string about half way up the inside of the winglet.

I have heard questions about lowering the cruise attitude on the LongEZ, but certainly am not commenting on that.

In the 80s I heard of at least one winglet that was installed upside down. Makes a guy think twice about mods, doesn’t it.

Bill James, Fort Worth VariEze

Downdraft Plenums

Quickcowls

There was supposed to be Anhedral???

http://www.ezchronicles.com/blogger.html

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  • 2 months later...

Prior to modifying the gear legs on my Varieze, I checked the AOA at cruise. It was 1.5 deg using a small level below the right side longeron. I expect that the AOA may be a bit lower than some other Variezes since I installed LongEz type lower winglets a number of years ago. I believe that the lower winglets provided more lift at the very rear most of the plane and thus a lower angle in flight. My ability to see over the nose at minimum touchdown speed was also much improved. They also greatly stabilized a slow 80 mph final approach.

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Prior to modifying the gear legs on my Varieze, I checked the AOA at cruise. It was 1.5 deg using a small level below the right side longeron. I expect that the AOA may be a bit lower than some other Variezes since I installed LongEz type lower winglets a number of years ago. I believe that the lower winglets provided more lift at the very rear most of the plane and thus a lower angle in flight. My ability to see over the nose at minimum touchdown speed was also much improved. They also greatly stabilized a slow 80 mph final approach.

Interesting. So let me ask these:

 

Does the lower winglet reduce wingtip vortice, thus increasing lift?

 

if so, then, for those folks that use a blended winglet, or omit the lower winglet, would it have a lower lift wing, increasing the AOA?

 

If so then I would think the higher AOA would result in greater drag.

 

So then, does the lower winglet make for a faster craft?

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I believe that the lower winglet does decrease the vortice, but possibly at the expense of speed. It seems that the lower winglet would create an air dam and thus higher pressure at the lower side of the swept wing.

Yes, I feel that the cruise AOA would be greater without a lower winglet, but since the racers take it off I expect they have found their speed greater.

Looks like there is a trade-off ......lower AOA vs cleaner design.

There is probably more variables involved, but since I only have one aircraft I can only comment on my situation....and my main desire all along has been to lower my take-off and landing speeds and distances. I have made quite a few changes in my Varieze since built and first flown in 1981 that were not documented very well and I may have a lower top end than years ago. I did modify my original prop back in the 80's per Gary Hertzler that increased my top end about 8 mph, later installed an almost constant speed wood prop (Performance Prop that lowered my top rpm and top speed but increased my static rpm), changed the bottom cowling and inlet, ram air box,etc.....so anyone interested in modifying their aircraft has that choice to experiment.

Of course I have looked for extra speed, but with a C-85 I am quite happy to fly at 150 mph cruise and burn 4 gph (without leaning past max EGT) and also a touchdown at below 70 mph.....and turning off the runway at the first intersection at 1800 ft.

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Prior to modifying the gear legs on my Varieze, I checked the AOA at cruise. It was 1.5 deg using a small level below the right side longeron.

Let's make sure that we all use the right terminology. What you measured was the INCIDENCE angle of the fuselage to the flight path. "Cruise" is a grey term - unless you know that IAS, weight, and CG of the aircraft when you measured that incidence angle, it doesn't tell you a whole lot.

AOA is the "Angle of Attack", and is an arbitrary angle formed between the chord line of a lifting body and the flight path. Knowing an incidence angle tells you nothing about the AOA unless you know that airfoil shape and the mounting incidence angle of the airfoil.

I expect that the AOA may be a bit lower than some other Variezes since I installed LongEz type lower winglets a number of years ago. I believe that the lower winglets provided more lift at the very rear most of the plane and thus a lower angle in flight.

There is no evidence from folks that have flown aircraft with and without lower winglets that they have any noticeable effect at cruise speeds, on LE's, COZY's or VE's. They neither increase nor decrease measured airspeeds, nor change the flight incidence angles (or AOA's) in cruise.

My ability to see over the nose at minimum touchdown speed was also much improved. They also greatly stabilized a slow 80 mph final approach.

Those effects are due to the lower winglet acting as an end plate and reducing span-wise flow, which also increases the effectivity of the ailerons (as do the flow fences, especially on VE's with the larger sweep angle). This effect would only be seen at low IAS's - not in cruise (unless you're cruising at 25K ft.).

Does the lower winglet reduce wingtip vortice, thus increasing lift?

The singular of vortices is "vortex". And the answer is that with true "Whitcomb" winglets, the strength of the vortex IS reduced, but that doesn't affect lift directly - it affects drag (well, it will increase the slope of the lift curve too, by giving a higher effective aspect ratio, but the effect is very small, and any AOA difference due to this will be very small and probably not measurable on our aircraft).

 

The strength of the vortex is a measure of the INDUCED drag of the airfoil (a 2D airfoil - infinitely long - has no induced drag - short stubby wings with low aspect ratios have higher induced drag). The winglets reduce drag in the same manner that making the airfoil longer would, but without increasing wing area and without needing stronger structure due to longer moment arms.

 

So no, the lower winglet isn't reducing the vortex strength - the combination of upper and lower winglets is, at low IAS's (high AOA's), and it mostly affects the drag, not the lift.

 

Remember also that in unaccelerated flight (constant vertical speed, whether positive, zero, or negative) the lift always equals the weight, so you don't "increase lift" or "decrease lift" with changes, although you may effect the point on the lift curve slope where you're operating.

 

if so, then, for those folks that use a blended winglet, or omit the lower winglet, would it have a lower lift wing, increasing the AOA?

No, since the previous postulate is incorrect. While the upper winglet isn't as effective as it might be at reducing drag at high AOA's if the lower winglet were there, it's still doing something to reduce the vortex strength a bit, although at cruise the vortex isn't strong anyway. The major effect of the lower winglet, as stated above, is to reduce spanwise flow at low IAS's (high AOA's) and reduce deep stall susceptibility while increasing aileron effectiveness.

 

If so then I would think the higher AOA would result in greater drag.

Again, since the previous postulates were incorrect, any conclusions flowing from them are incorrect.

 

So then, does the lower winglet make for a faster craft?

No. As stated, no one has ever noticed a measurable speed difference in either direction when removing lower winglets.

 

The lower winglets are on our aircraft to help low speed aileron effectiveness, stability, and reduced deep stall susceptibility. That's it.

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Mark, Thanks for the insights....

 

The major effect of the lower winglet, as stated above, is to reduce spanwise flow at low IAS's (high AOA's) and reduce deep stall susceptibility while increasing aileron effectiveness.

So is that not the same function as the vortilons in the canard plans?

 

Also now that you mention deep stall I am reminded of a conversation a while back that I had with an old pilot friend. When I mentioned that I was building a Long-EZ he said that that design had a problem with deep stalls. Now I have not heard that, or ready anything about that in the CPs. It is my understanding that the Long-EZ is supposed to be stall resistant.

 

I do seem to recall reading something about a mandatory change for the Varieze calling for installation of vortilons on the main wing. Is that perhaps what he was thinking about?

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So is that not the same function as the vortilons in the canard plans?

They are certainly related. Both are there to reduce spanwise flow, but obviously in a different manner, given their placement. Both have been tested and shown to help at high AOA's (low IAS's).

 

... When I mentioned that I was building a Long-EZ he said that that design had a problem with deep stalls. Now I have not heard that, or ready anything about that in the CPs. It is my understanding that the Long-EZ is supposed to be stall resistant.

Where to start. There is no plane that will not stall if a high enough AOA is reached. A deep stall in any airplane will occur when the CG is too far aft and the stall "locks in", and it becomes exceedingly difficult (if not impossible) for power or control inputs to get the aircraft out of the stall. The LE (and VE, and COZY, and Velocity, etc.) are all stall resistant, in the sense that the canard stalls first and the main wing never stalls. BUT THIS IS ALL DEPENDENT UPON THE CG POSITION (first order), the installation of the vortilons (second order) and lower winglet (third order).

 

If the CG is too far aft, any of these canard aircraft can enter a deep stall, and many have.

 

I'm exceedingly surprised that you claim to have found no reference to deep stalls in the CP's, since a cursory text search of the on-line versions finds references, explanations, test results, and more for deep stalls in relation to canard aircraft in at least these CP's:

 

15, 37, 46, 55, 68, 69, 71, 76, 82

 

Please read them. Burt, et. al. did extensive deep stall testing of a full scale Long-EZ mounted on a truck, as well as extensive analysis of a number of deep stall accidents. They are directly applicable to anyone building or flying a canard aircraft.

 

I do seem to recall reading something about a mandatory change for the Varieze calling for installation of vortilons on the main wing. Is that perhaps what he was thinking about?

I don't know who the "he" is that you're referring to, or in relation to what. The VE first tried wing cuffs and then eventually went to the vortilons for low speed issues.

 

And your point is ?

Geez, I don't know - maybe just a bit of education? So people don't do stupid things based on misconceptions of how these aircraft work?
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- maybe just a bit of education? So people don't do stupid things based on misconceptions of how these aircraft work?

More like a ton of education, Marc! :thumbsup:

I've learned a lot through your posts.

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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They are certainly related. Both are there to reduce spanwise flow, but obviously in a different manner, given their placement. Both have been tested and shown to help at high AOA's (low IAS's).

 

Where to start. There is no plane that will not stall if a high enough AOA is reached. A deep stall in any airplane will occur when the CG is too far aft and the stall "locks in", and it becomes exceedingly difficult (if not impossible) for power or control inputs to get the aircraft out of the stall. The LE (and VE, and COZY, and Velocity, etc.) are all stall resistant, in the sense that the canard stalls first and the main wing never stalls. BUT THIS IS ALL DEPENDENT UPON THE CG POSITION (first order), the installation of the vortilons (second order) and lower winglet (third order).

 

If the CG is too far aft, any of these canard aircraft can enter a deep stall, and many have.

 

I'm exceedingly surprised that you claim to have found no reference to deep stalls in the CP's, since a cursory text search of the on-line versions finds references, explanations, test results, and more for deep stalls in relation to canard aircraft in at least these CP's:

 

15, 37, 46, 55, 68, 69, 71, 76, 82

 

Please read them. Burt, et. al. did extensive deep stall testing of a full scale Long-EZ mounted on a truck, as well as extensive analysis of a number of deep stall accidents. They are directly applicable to anyone building or flying a canard aircraft.

 

I don't know who the "he" is that you're referring to, or in relation to what. The VE first tried wing cuffs and then eventually went to the vortilons for low speed issues.

 

Geez, I don't know - maybe just a bit of education? So people don't do stupid things based on misconceptions of how these aircraft work?

If I recall correctlly, Dick Rutan test flew the Vari but most likely the Long in a hazardous severe rear CG position. I expect that was covered in an old CP. The Varieze pilot handbook covers the first flight box with the CG towards the front....for a reason. Of course the Velocity had a deep stall situation and did a splash in the water many years ago. Seriously,since there are so many non-builders involved today maybe someone that has apparently all the info may want to write a book or manual on canard aircraft. Probably, all the info is out there somewhere in the plans, CP's, etc. but a some of new owners are doing without.

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Seriously,since there are so many non-builders involved today maybe someone that has apparently all the info may want to write a book or manual on canard aircraft. Probably, all the info is out there somewhere in the plans, CP's, etc. but a some of new owners are doing without.

I was a non-builder Longez owner----and now a non-builder Cozy owner. I have read and cateloged all the CPs and Cozy Newsletters. I have read and cateloged the CSA newsletters ever since I became a member. I have also extensively studied both the Longez and Cozy plans.

 

I have been the sole maintainer----and have done extensive modifications and repairs to both airplanes---with the most extensive modification involving switching to downdraft cooling on my Longez with all the modifications involved with also hanging a larger engine.

 

My point is that I think that it is irresponsible to do anything less (being intimately familiar with all the documentation) as a non-builder. Congratulations to the non-builders (including me) for skipping many hard years of work---but what makes you think that you can skip knowing about your aircraft? Who do you think is going to inspect and know everything that needs to be known about your aircraft? Your local A&P?----Guess again. Your A&P will give you a nice sign off on your engine---and will do an ok look at your airframe----but seriously----what does he know in this regard? Unless you are living next to a canard guru who knows what he is doing, YOU are the expert. And if you are not comfortable with that aspect, you should not be owning one of these machines.

 

The 100 ways document is a good intro paper---but does not replace actually reading the CPs (Rutan) or Cozy newsletters. How do you even know what to be scared of if you don't even read the documentation? And there is stuff to be scared of if you don't heed the warnings.

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... maybe someone that has apparently all the info may want to write a book or manual on canard aircraft....

Terry Yake has long since done just that. See:

 

http://www.ez.org/articles.htm

 

and look for:

 

Terry Yake's extensive "Resource Guide for Nonbuilder Owners of Canard Composite Aircraft"

 

Drew is exactly right that all canard builders, flyers and owners should read all the CP's, CSA newsletters, and COZY newsletters (for COZY builders). Not to mention Terry's documents, and anything else they can find on the ez.org website and the canard-aviator's mailing list (and COZY mailing list).

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Terry Yake has long since done just that. See:

 

http://www.ez.org/articles.htm

 

and look for:

 

Terry Yake's extensive "Resource Guide for Nonbuilder Owners of Canard Composite Aircraft"

 

Drew is exactly right that all canard builders, flyers and owners should read all the CP's, CSA newsletters, and COZY newsletters (for COZY builders). Not to mention Terry's documents, and anything else they can find on the ez.org website and the canard-aviator's mailing list (and COZY mailing list).

Since the price of many canard aircraft is so low compared to other aircraft, eg. Variezes in the $10 to $15k and Longs another $10k or so higher ...there are new owners that have gotten into the game on the cheap and are playing accordingly. I feel one way to stop or slow this down is to quit selling these canard aircraft at such a low price ....or not at all. Or screening the buyer to the max vs "Great, I unloaded it and now it's not my problem."

Even building a plane does not prevent ignorant moves by a too anxious builder to get flyiing let alone the buyer who does not have any interest in at least reviewing the plans, etc.

I must admit that today I would have at least stayed near or above the airport at Corona Calif. on my first flight vs heading out 25 miles away. (My rational was that it was out toward the desert away from homes). However, twenty-seven years ago I was obviously younger, a low time pilot and anxious to get airborne. Today, there are many more newbies doing the same and much worse.

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I'm exceedingly surprised that you claim to have found no reference to deep stalls in the CP's, since a cursory text search of the on-line versions finds references, explanations, test results, and more for deep stalls in relation to canard aircraft in at least these CP's:

 

15, 37, 46, 55, 68, 69, 71, 76, 82

 

 

Please read them. Burt, et. al. did extensive deep stall testing of a full scale Long-EZ mounted on a truck, as well as extensive analysis of a number of deep stall accidents. They are directly applicable to anyone building or flying a canard aircraft.

 

 

Ok, first of all, I wish to thank you for your assistance in helping me and others understand these issues. Your insights are deeply appreciated.

 

It was not my intention to claim that the CP's do not address the deep stall issue, rather that at this time of my post yesterday, I did not recall reading anything that might address what my friend mentioned, that the Long-EZ was susceptible to Deep Stall. I have gone through all the CPs on the TERF CD, albeit rather rapidly. Reading PDFs on a PC is far from ideal for me. I intend to print them in there entirety and go through them more thoroughly. I will read through the CPs you listed tonight to get on top of the subject.

 

My friends comment to me about the Long-EZ was directed at the design of the aircraft. Indeed, he was telling me that there was, or is, a major design problem with the Long-EZ in particular, that makes the Long-EZ susceptible to a deep stall and perhaps required a major design change, ie main wing airfoil etc. It was that statement that surprised me, or rather I was skeptical about because I do not recall any such major design change to the Long-EZ in the CPs, or even in this forum for that matter. That point is really moot because I do not know really what he was referring to and I regret even bringing the subject up here without more specifics (I don't think he really knew what he was talking about).

 

QUOTE=Marc Zeitlin]I don't know who the "he" is that you're referring to, or in relation to what. The VE first tried wing cuffs and then eventually went to the vortilons for low speed issues.

 

The "he" I was referring to was my friend,.

 

Geez, I don't know - maybe just a bit of education? So people don't do stupid things based on misconceptions of how these aircraft work?

 

I will submit that perhaps I have said something stupid here, however if you know of anything stupid I have done with my aircraft, please let me know right away. I admit that I am a novice at this and therefore I am building my plane as close to plans as I can.

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