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JonathanMilbank

Joined: 14 Apr 2012
Posts: 388
Location: Aberdeen area

Posted: Sat Jan 14, 2017 2:41 pm Post subject: 1.5 degrees right?

I'm converting my Classic to XS firewall forward and the instructions for mounting the engine call for the 4 washers on each lord mount to be arranged so that the engine is angled 1.5 degrees to the right.



The Classic build manual didn't give this stipulation and so mine was pointing straight ahead. What effect will there likely be when I start flying in the new configuration. Up until now there has been a tendency for the aircraft to roll gently to the right in the cruise.



Will angling the engine to the right make the right roll tendency better or worse? Please give me the aerodynamic logic for this 1.5 degree offset.



Thanks.

Jonathan

dpark748(at)icloud.com
Guest

Posted: Sat Jan 14, 2017 2:52 pm Post subject: 1.5 degrees right?

Was the XS Fin offset?



Dave Park

 	  Quote: 	
		   On 14 Jan 2017, at 22:41, jonathanmilbank <jdmilbank(at)yahoo.co.uk> wrote:

 

 

 

 I'm converting my Classic to XS firewall forward and the instructions for mounting the engine call for the 4 washers on each lord mount to be arranged so that the engine is angled 1.5 degrees to the right.

 

 The Classic build manual didn't give this stipulation and so mine was pointing straight ahead. What effect will there likely be when I start flying in the new configuration. Up until now there has been a tendency for the aircraft to roll gently to the right in the cruise.

 

 Will angling the engine to the right make the right roll tendency better or worse? Please give me the aerodynamic logic for this 1.5 degree offset.

 

 Thanks.

 Jonathan

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=465078#465078

JonathanMilbank

Joined: 14 Apr 2012
Posts: 388
Location: Aberdeen area

Posted: Sat Jan 14, 2017 3:14 pm Post subject: Re: 1.5 degrees right?

Sorry but I don't know. Perhaps the esteemed Bud or another guru might know the answer to that.

spcialeffects

Joined: 29 Aug 2012
Posts: 306
Location: Kent

Posted: Sun Jan 15, 2017 1:06 am Post subject: Re: 1.5 degrees right?

Hello Jonathan, Frank Xuereb here. If you watch 'a plane is born' when he gets the engine delivered Mark gives quite a good explanation as to the reason for the offset. Basically on full throttle the wind wash created by the prop would hit the port side of the fin and give a tendency to push you to the left. This is of course easily corrected by right rudder input but to help reduce this effect the back of the engine is offset by 27mm but keeps the prop flange at 90 degrees.



Good luck, Frank kit 165

davidjoyce(at)doctors.org
Guest

Posted: Sun Jan 15, 2017 3:39 am Post subject: 1.5 degrees right?

Jonathan, I suspect you are dealing with two distinct effects here. The tendency to roll to the right suggests to me that you have slightly different effective angles of attack on the two wings, either because of how the wings were constructed or because of how they were attached to the fuselage. This seems to be very common and a small piece of triangular section wood, length adjusted for effect, under (in your case ) the port aileron will correct it. As previously stated the engine offset is there to correct the tendency for the clockwise spiral propwash around the fuselage impinging on the left side of the fin and tending to produce a left turn. This effect is most noticeable on take off (and probably also in monos) when at max power and lowish speed with limited rudder authority, when a significant amount of Right rudder is needed to keep in a straight line. It is also noticeable in a full power lowish speed climb. I believe that the amount of offset is designed to allow hands off balanced straight flight at typical cruise speeds/power, whilst also helping to maintain control authority on take off. Regards, David Joyce,GXSDJ 

   

 

On 2017-01-14 22:41, jonathanmilbank wrote:  	  Quote: 	
		    	  Quote: 	
		  --> Europa-List message posted by: "jonathanmilbank" <jdmilbank(at)yahoo.co.uk (jdmilbank(at)yahoo.co.uk)>



I'm converting my Classic to XS firewall forward and the instructions for mounting the engine call for the 4 washers on each lord mount to be arranged so that the engine is angled 1.5 degrees to the right.



The Classic build manual didn't give this stipulation and so mine was pointing straight ahead. What effect will there likely be when I start flying in the new configuration. Up until now there has been a tendency for the aircraft to roll gently to the right in the cruise.



Will angling the engine to the right make the right roll tendency better or worse? Please give me the aerodynamic logic for this 1.5 degree offset.



Thanks.

Jonathan

 Of how they are mounted on the fuselage. This is very common and can be readily corrected with a small trangular section of wood stuck under the (in your case)  port aileron



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=465078#465078

ttp://www.matronics.com/Navigator?Europa-List

ics.com

.com

.matronics.com/contribution

rogersheridan(at)mac.com
Guest

Posted: Sun Jan 15, 2017 3:52 am Post subject: 1.5 degrees right?

Further info here for bookworms!

https://dl.dropboxusercontent.com/u/246742/TailWheel1.pdf



 	  Quote: 	
		  On 15 Jan 2017, at 11:38, davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk) wrote:

 

Jonathan, I suspect you are dealing with two distinct effects here. The tendency to roll to the right suggests to me that you have slightly different effective angles of attack on the two wings, either because of how the wings were constructed or because of how they were attached to the fuselage. This seems to be very common and a small piece of triangular section wood, length adjusted for effect, under (in your case ) the port aileron will correct it. As previously stated the engine offset is there to correct the tendency for the clockwise spiral propwash around the fuselage impinging on the left side of the fin and tending to produce a left turn. This effect is most noticeable on take off (and probably also in monos) when at max power and lowish speed with limited rudder authority, when a significant amount of Right rudder is needed to keep in a straight line. It is also noticeable in a full power lowish speed climb. I believe that the amount of offset is designed to allow hands off balanced straight flight at typical cruise speeds/power, whilst also helping to maintain control authority on take off. Regards, David Joyce,GXSDJ 

  



On 2017-01-14 22:41, jonathanmilbank wrote:  	  Quote: 	
		    	  Quote: 	
		  --> Europa-List message posted by: "jonathanmilbank" <jdmilbank(at)yahoo.co.uk (jdmilbank(at)yahoo.co.uk)>



I'm converting my Classic to XS firewall forward and the instructions for mounting the engine call for the 4 washers on each lord mount to be arranged so that the engine is angled 1.5 degrees to the right.



The Classic build manual didn't give this stipulation and so mine was pointing straight ahead. What effect will there likely be when I start flying in the new configuration. Up until now there has been a tendency for the aircraft to roll gently to the right in the cruise.



Will angling the engine to the right make the right roll tendency better or worse? Please give me the aerodynamic logic for this 1.5 degree offset.



Thanks.

Jonathan

 Of how they are mounted on the fuselage. This is very common and can be readily corrected with a small trangular section of wood stuck under the (in your case)  port aileron



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=465078#465078

ttp://www.matronics.com/Navigator?Europa-List

ics.com

.com

.matronics.com/contribution

nigel_graham(at)m-tecque.
Guest

Posted: Sun Jan 15, 2017 2:09 pm Post subject: 1.5 degrees right?

Jonathan,



I think you have provided the answer to your own question.



The fact that you have run your Classic with no engine offset and  

noticed no asymmetric flying characteristics speaks volumes.

The whole idea of canting an engine sideways and forcing the propeller  

disc through the air at anything other than normal to the oncoming  

airstream is daft.

The theory that canting the engine sideways will counter the yaw  

effect of the prop wash seems to be based on a misunderstanding of  

what is really happening and itâ€™s done because â€œthatâ€™s how itâ€™s always  

been doneâ€!



On your Classic, you sensibly mounted your engine head on to the wind  

and you set you propeller blades pitch to the recommended angle. Each  

time the blades rotate their angles of attack remain equal to each  

other and constant to the oncoming wind and each blade generates the  

same thrust throughout each revolution of the prop.



Now consider what happens when you follow the XS build instructions  

and cant the engine 1.5 degrees to the right.



If youâ€™re flying straight-and-level behind a right-hand tractor (Rotax  

912, 914), each time a blade passes over the top of the ark, its pitch  

is effectively reduced by 1.5 degrees and as it swings through the  

bottom of the ark, its effective pitch is increased by 1.5 degrees.   

This means that your propeller is producing significantly more thrust  

from the bottom half of the propeller disc than the top half â€“ and  

that produces a pitch up change in attitude â€“ and not the sideways  

thrust you had hoped to achieve by mounting the engine sideways.



â€œSo if thatâ€™s true, why has nobody noticed this pitch up attitude?â€ â€“  

a good question (even though I asked it myself).



All Europaâ€™s are fitted with a pitch trimmer â€“ so these effects are  

unconsciously trimmed out by the pilot during different phases of  

flight.



â€œAh, but what about the propensity to swing to the left on take-off?â€   

- Same thing, different plane.



The  Monowheel sits on the ground at a deck angle of (is it about 12  

degrees? I forget) so the engine is now canted up at the front by this  

amount. At the beginning of the take-off run, the upcoming blade on  

the left hand side has 12 degrees wound off its effective pitch, while  

the down going blade on the right has 12 degrees added to its pitch.  

This produces significantly more thrust on the right hand side of the  

disc than the left, resulting in a turning moment to the left. It's a  

potential problem with all tail-draggers



The Tri-Gear variant of course sits horizontally on the ground, so has  

none of this asymmetric thrust â€“ so is less prone to dive off to the  

left on take off; another reason why the Tri-Gear is perceived to be  

more benign than the Mono.



Canting an engine is a very crude way of addressing a relatively  

transient problem â€“ Fitting a rudder trimmer would be a far more  

elegant solution â€“ should it be necessary.



Hope that wasnâ€™t too long winded!



Nigel



PS the roll issue has nothing to do with engine position.





Quoting jonathanmilbank <jdmilbank(at)yahoo.co.uk>:



 	  Quote: 	
		   



 I'm converting my Classic to XS firewall forward and the  

 instructions for mounting the engine call for the 4 washers on each  

 lord mount to be arranged so that the engine is angled 1.5 degrees  

 to the right.



 The Classic build manual didn't give this stipulation and so mine  

 was pointing straight ahead. What effect will there likely be when I  

 start flying in the new configuration. Up until now there has been a  

 tendency for the aircraft to roll gently to the right in the cruise.



 Will angling the engine to the right make the right roll tendency  

 better or worse? Please give me the aerodynamic logic for this 1.5  

 degree offset.



 Thanks.

 Jonathan





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=465078#465078

JonathanMilbank

Joined: 14 Apr 2012
Posts: 388
Location: Aberdeen area

Posted: Sun Jan 15, 2017 3:03 pm Post subject: Re: 1.5 degrees right?

Wow and what a plethora of replies! Thanks very much to all of you.



Shortly after I posted this topic and before any replies came in, a fellow Europa pilot confirmed in advance much of what you guys have explained and your responses are excellent. 



He mentioned that when he let someone else have a go on the Europa's controls, the guy was caught out by the amount of left yaw during the go-around at low speed from a missed approach. My friend had to assist, so clearly some people would benefit from the engine being offset by 1.5 degrees.



I suppose that once anyone gets used to the aircraft, then applying right pedal when increasing power becomes instinctive.

rlborger(at)mac.com
Guest

Posted: Sun Jan 15, 2017 3:07 pm Post subject: 1.5 degrees right?

Nigel,

Thanks for the detailed description.  I have often wondered about the effectiveness of the offset.  It just didnâ€™t seem right to me.  At some point in the future Iâ€™ll have to unbolt the engine for something.  When I do, Iâ€™ll remove the offset and see what difference it makes.  



Blue skies & tailwinds,Bob BorgerEuropa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP3705 Lynchburg Dr.Corinth, TX  76208-5331Cel: 817-992-1117rlborger(at)mac.com (rlborger(at)mac.com)



On Jan 15, 2017, at 4:08 PM, nigel_graham(at)m-tecque.co.uk (nigel_graham(at)m-tecque.co.uk) wrote:

--> Europa-List message posted by: nigel_graham(at)m-tecque.co.uk (nigel_graham(at)m-tecque.co.uk)Jonathan,I think you have provided the answer to your own question.The fact that you have run your Classic with no engine offset and noticed no asymmetric flying characteristics speaks volumes.The whole idea of canting an engine sideways and forcing the propeller disc through the air at anything other than normal to the oncoming airstream is daft.The theory that canting the engine sideways will counter the yaw effect of the prop wash seems to be based on a misunderstanding of what is really happening and itâ€™s done because â€œthatâ€™s how itâ€™s always been doneâ€!On your Classic, you sensibly mounted your engine head on to the wind and you set you propeller blades pitch to the recommended angle. Each time the blades rotate their angles of attack remain equal to each other and constant to the oncoming wind and each blade generates the same thrust throughout each revolution of the prop.Now consider what happens when you follow the XS build instructions and cant the engine 1.5 degrees to the right.If youâ€™re flying straight-and-level behind a right-hand tractor (Rotax 912, 914), each time a blade passes over the top of the ark, its pitch is effectively reduced by 1.5 degrees and as it swings through the bottom of the ark, its effective pitch is increased by 1.5 degrees.  This means that your propeller is producing significantly more thrust from the bottom half of the propeller disc than the top half â€“ and that produces a pitch up change in attitude â€“ and not the sideways thrust you had hoped to achieve by mounting the engine sideways.â€œSo if thatâ€™s true, why has nobody noticed this pitch up attitude?â€ â€“ a good question (even though I asked it myself).All Europaâ€™s are fitted with a pitch trimmer â€“ so these effects are unconsciously trimmed out by the pilot during different phases of flight.â€œAh, but what about the propensity to swing to the left on take-off?â€  - Same thing, different plane.The  Monowheel sits on the ground at a deck angle of (is it about 12 degrees? I forget) so the engine is now canted up at the front by this amount. At the beginning of the take-off run, the upcoming blade on the left hand side has 12 degrees wound off its effective pitch, while the down going blade on the right has 12 degrees added to its pitch. This produces significantly more thrust on the right hand side of the disc than the left, resulting in a turning moment to the left. It's a potential problem with all tail-draggersThe Tri-Gear variant of course sits horizontally on the ground, so has none of this asymmetric thrust â€“ so is less prone to dive off to the left on take off; another reason why the Tri-Gear is perceived to be more benign than the Mono.Canting an engine is a very crude way of addressing a relatively transient problem â€“ Fitting a rudder trimmer would be a far more elegant solution â€“ should it be necessary.Hope that wasnâ€™t too long winded!NigelPS the roll issue has nothing to do with engine position.

pjeffers(at)talktalk.net
Guest

Posted: Mon Jan 16, 2017 1:34 am Post subject: 1.5 degrees right?

Hi all,

Just for the record.Â  In the early pre history build of the classic EuropaÂ  the instructions said that the correct setup for the engine would be achieved if the 'washers' were adjusted such that the spinner lined up with the cowling. That supposedly gave us the 1.5 degree right offset. Nothing further was said on this issue.Â  My only comment is that it was a bit crude but seemed to work.

A word of advice for Bob is that if you change your current setup for the engine mount then your spinner will not line up with your cowling. It is possible to address this misalignment but not simple.

Pete J

 

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Robert Borger

Sent: 15 January 2017 23:07

To: europa-list(at)matronics.com

Subject: Re: 1.5 degrees right?

 

Nigel,

 



Thanks for the detailed description.  I have often wondered about the effectiveness of the offset.  It just didnâ€™t seem right to me.  At some point in the future Iâ€™ll have to unbolt the engine for something.  When I do, Iâ€™ll remove the offset and see what difference it makes.  



 



Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

rlborger(at)mac.com (rlborger(at)mac.com)



 



On Jan 15, 2017, at 4:08 PM, nigel_graham(at)m-tecque.co.uk (nigel_graham(at)m-tecque.co.uk) wrote:



 

--> Europa-List message posted by: nigel_graham(at)m-tecque.co.uk (nigel_graham(at)m-tecque.co.uk)



Jonathan,



I think you have provided the answer to your own question.



The fact that you have run your Classic with no engine offset and noticed no asymmetric flying characteristics speaks volumes.

The whole idea of canting an engine sideways and forcing the propeller disc through the air at anything other than normal to the oncoming airstream is daft.

The theory that canting the engine sideways will counter the yaw effect of the prop wash seems to be based on a misunderstanding of what is really happening and itâ€™s done because â€œthatâ€™s how itâ€™s always been doneâ€!



On your Classic, you sensibly mounted your engine head on to the wind and you set you propeller blades pitch to the recommended angle. Each time the blades rotate their angles of attack remain equal to each other and constant to the oncoming wind and each blade generates the same thrust throughout each revolution of the prop.



Now consider what happens when you follow the XS build instructions and cant the engine 1.5 degrees to the right.



If youâ€™re flying straight-and-level behind a right-hand tractor (Rotax 912, 914), each time a blade passes over the top of the ark, its pitch is effectively reduced by 1.5 degrees and as it swings through the bottom of the ark, its effective pitch is increased by 1.5 degrees.  This means that your propeller is producing significantly more thrust from the bottom half of the propeller disc than the top half â€“ and that produces a pitch up change in attitude â€“ and not the sideways thrust you had hoped to achieve by mounting the engine sideways.



â€œSo if thatâ€™s true, why has nobody noticed this pitch up attitude?â€ â€“ a good question (even though I asked it myself).



All Europaâ€™s are fitted with a pitch trimmer â€“ so these effects are unconsciously trimmed out by the pilot during different phases of flight.



â€œAh, but what about the propensity to swing to the left on take-off?â€  - Same thing, different plane.



The  Monowheel sits on the ground at a deck angle of (is it about 12 degrees? I forget) so the engine is now canted up at the front by this amount. At the beginning of the take-off run, the upcoming blade on the left hand side has 12 degrees wound off its effective pitch, while the down going blade on the right has 12 degrees added to its pitch. This produces significantly more thrust on the right hand side of the disc than the left, resulting in a turning moment to the left. It's a potential problem with all tail-draggers



The Tri-Gear variant of course sits horizontally on the ground, so has none of this asymmetric thrust â€“ so is less prone to dive off to the left on take off; another reason why the Tri-Gear is perceived to be more benign than the Mono.



Canting an engine is a very crude way of addressing a relatively transient problem â€“ Fitting a rudder trimmer would be a far more elegant solution â€“ should it be necessary.



Hope that wasnâ€™t too long winded!



Nigel



PS the roll issue has nothing to do with engine position.





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JonSmith

Joined: 21 May 2010
Posts: 110

Posted: Mon Jan 16, 2017 1:58 am Post subject: Re: 1.5 degrees right?

Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset.



I remember quite well the famous diagram of the propeller slipstream helix spiralling around the fuselage and whacking the fin on one side or the other depending on direction of engine rotation - in our Rotax-Europa case the left side of the fin causing the nose to yaw more and more to the left with increasing power.  Certainly in my aircraft on the rare perfectly calm and smooth day with no other influencing factors I notice on take off that at the point of lift off a considerable amount of right rudder input is required at that point, nearly half I'd say.  



I suppose that aircraft design is always a compromise and there are various solutions to counter this problem, engine offsets, rudder trims (fixed and inflight adjustable), offset fins etc, all designed to help make life easier for the poor pilot who has to cope with the cacophony of forces his machine is constantly bombarded with!  Our Europa is as basic as you can get in it's standard form with the options of an offset engine mounting and/ or fixed rudder trim tab or nothing!  



I note and accept what you say about an engine offset causing inefficiencies and undesirable handling tendencies and that from a perfect performance point of view it would be absolutely the best for the engine to be mounted square on to the airflow but wouldn't the overall effect of the thrust vector being offset completely outweigh these minor undesirable tendencies and make life easier for the pilot?  My instinct tells me that the unwanted effects would be relatively insignificant but I genuinely don't know....!



I've always considered that aircraft compromised by simplicity would in the ideal world be set up to fly perfectly straight and balanced with hands and feet off in the cruise as that's what we spend most of the time doing.  Thus in a perfect aircraft with the engine correctly offset this should be achieved without any extra trim tabs, assuming the designer got his sums correct with the offset!  (I'm lucky I think because my aircraft seems to achieve this quite nicely!).  I also note that you believe a rudder trim tab to be a better solution than an engine offset.  Do you consider that having the rudder permanently offset into the airflow to keep the aircraft balanced to be more efficient than the minor unwanted propeller blade effects caused by having an engine offset?  Again I'm only asking the question because I genuinely don't know..!



I believe that a correctly offset engine will assist the pilot during take off by reducing the amount of right rudder deflection required throughout.  Without any offset to help, surely more right rudder deflection would be needed to keep straight thus effectively reducing the maximum crosswind component from the left that the aircraft itself could cope with?  A rudder trim would not help this situation of course - it might make reduce the load on the pilot's leg but the actual rudder deflection is still required.



As I say, an interesting post, I'm very open minded but am yet to be convinced that I have made a mistake by following the manual and building mine WITH the quoted 1.5 degree offset....!

_________________
G-TERN
Classic Mono

JonSmith

Joined: 21 May 2010
Posts: 110

Posted: Mon Jan 16, 2017 2:22 am Post subject: Re: 1.5 degrees right?

NIGEL - Doh - I'm very sorry to get your name the wrong way round in my post above.   I woke up early and it was still far too early when I wrote it.....!  That plus old age!

Cheers, Jon

_________________
G-TERN
Classic Mono

davidjoyce(at)doctors.org
Guest

Posted: Mon Jan 16, 2017 2:45 am Post subject: 1.5 degrees right?

Nigel, following on from this, I am most reluctant to believe that Ivan Shaw and Don Dykins (one of the outstanding aerodynamicists of our time!) got it wrong, or for that matter generations of designers of Spitfire/Hurricane era aircraft - which I believe al had engine offset and  fin offset incorporated, but even so were close to unmanageable if full power was used on take off. Performance then was very much a matter of life and death and an immense amount of research went into optimising performance - I certainly don't buy the notion that folk have always done it because  someone did it back in the dark ages and no-one has thought rationally about it since! 

    Offsetting the engine 1.5 degrees makes negligible difference to forward thrust - actually reduces it by just 0.03%, but using permanent right rudder induces extra drag which must be  an appreciably greater amount. 

    Regards, David Joyce, GXSDJ 

   

 

On 2017-01-16 09:58, JonSmith wrote:  	  Quote: 	
		    	  Quote: 	
		  --> Europa-List message posted by: "JonSmith" <jonsmitheuropa(at)tiscali.co.uk (jonsmitheuropa(at)tiscali.co.uk)>



Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset.



I remember quite well the famous diagram of the propeller slipstream helix spiralling around the fuselage and whacking the fin on one side or the other depending on direction of engine rotation - in our Rotax-Europa case the left side of the fin causing the nose to yaw more and more to the left with increasing power.  Certainly in my aircraft on the rare perfectly calm and smooth day with no other influencing factors I notice on take off that at the point of lift off a considerable amount of right rudder input is required at that point, nearly half I'd say.  



I suppose that aircraft design is always a compromise and there are various solutions to counter this problem, engine offsets, rudder trims (fixed and inflight adjustable), offset fins etc, all designed to help make life easier for the poor pilot who has to cope with the cacophony of forces his machine is constantly bombarded with!  Our Europa is as basic as you can get in it's standard form with the options of an offset engine mounting and/ or fixed rudder trim tab or nothing!  



I note and accept what you say about an engine offset causing inefficiencies and undesirable handling tendencies and that from a perfect performance point of view it would be absolutely the best for the engine to be mounted square on to the airflow but wouldn't the overall effect of the thrust vector being offset completely outweigh these minor undesirable tendencies and make life easier for the pilot?  My instinct tells me that the unwanted effects would be relatively insignificant but I genuinely don't know....!



I've always considered that aircraft compromised by simplicity would in the ideal world be set up to fly perfectly straight and balanced with hands and feet off in the cruise as that's what we spend most of the time doing.  Thus in a perfect aircraft with the engine correctly offset this should be achieved without any extra trim tabs, assuming the designer got his sums correct with the offset!  (I'm lucky I think because my aircraft seems to achieve this quite nicely!).  I also note that you believe a rudder trim tab to be a better solution than an engine offset.  Do you consider that having the rudder permanently offset into the airflow to keep the aircraft balanced to be more efficient than the minor unwanted propeller blade effects caused by having an engine offset?  Again I'm only asking the question because I genuinely don't know..!



I believe that a correctly offset engine will assist the pilot during take off by reducing the amount of right rudder deflection required throughout.  Without any offset to help, surely more right rudder deflection would be needed to keep straight thus effectively reducing the maximum crosswind component from the left that the aircraft itself could cope with?  A rudder trim would not help this situation of course - it might make reduce the load on the pilot's leg but the actual rudder deflection is still required.



As I say, an interesting post, I'm very open minded but am yet to be convinced that I have made a mistake by following the manual and building mine WITH the quoted 1.5 degree offset....!



--------

G-TERN

Classic Mono





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http://forums.matronics.com/viewtopic.php?p=465129#465129

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.com

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ptag.dev(at)talktalk.net
Guest

Posted: Mon Jan 16, 2017 6:23 am Post subject: 1.5 degrees right?

Hi! PeteÂ  and in response to all .....and when all is done and said donâ€™t forget to allow for â€œprop-washâ€ when doing all your theorising .

The mono would be uncontrolled in a â€œfull chatâ€ turbo wide open takeoff situation with my CS Woodcomp Â selected Â in â€œtake offâ€ .Even in trike configuration it requires full Rudder to remain straight ahead. Then add a considerable cross wind and you are set for a ground loop immediately the rear wheel brakes clear of the runway. Without differential braking the Fin and rudder donâ€™t have adequate authority .......IMHO ! Having said that I have landed at Marehamn against a 35 Knot wind from the Port side with rotor effect from trees 200 yards to the port side. Thank the lord for trike differential braking in that event.

Regards to all 

Bob HarrisonÂ  G-PTAG.

 

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Peter Jeffers

Sent: 16 January 2017 09:34

To: europa-list(at)matronics.com

Subject: RE: 1.5 degrees right?

 

Hi all,

Just for the record.  In the early pre history build of the classic Europa  the instructions said that the correct setup for the engine would be achieved if the 'washers' were adjusted such that the spinner lined up with the cowling. That supposedly gave us the 1.5 degree right offset. Nothing further was said on this issue.  My only comment is that it was a bit crude but seemed to work.

A word of advice for Bob is that if you change your current setup for the engine mount then your spinner will not line up with your cowling. It is possible to address this misalignment but not simple.

Pete J

 

From: owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com) [mailto:owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com)] On Behalf Of Robert Borger

Sent: 15 January 2017 23:07

To: europa-list(at)matronics.com (europa-list(at)matronics.com)

Subject: Re: 1.5 degrees right?

 

Nigel,

 



Thanks for the detailed description.  I have often wondered about the effectiveness of the offset.  It just didnâ€™t seem right to me.  At some point in the future Iâ€™ll have to unbolt the engine for something.  When I do, Iâ€™ll remove the offset and see what difference it makes.  



 



Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

rlborger(at)mac.com (rlborger(at)mac.com)



 



On Jan 15, 2017, at 4:08 PM, nigel_graham(at)m-tecque.co.uk (nigel_graham(at)m-tecque.co.uk) wrote:



 

--> Europa-List message posted by: nigel_graham(at)m-tecque.co.uk (nigel_graham(at)m-tecque.co.uk)



Jonathan,



I think you have provided the answer to your own question.



The fact that you have run your Classic with no engine offset and noticed no asymmetric flying characteristics speaks volumes.

The whole idea of canting an engine sideways and forcing the propeller disc through the air at anything other than normal to the oncoming airstream is daft.

The theory that canting the engine sideways will counter the yaw effect of the prop wash seems to be based on a misunderstanding of what is really happening and itâ€™s done because â€œthatâ€™s how itâ€™s always been doneâ€!



On your Classic, you sensibly mounted your engine head on to the wind and you set you propeller blades pitch to the recommended angle. Each time the blades rotate their angles of attack remain equal to each other and constant to the oncoming wind and each blade generates the same thrust throughout each revolution of the prop.



Now consider what happens when you follow the XS build instructions and cant the engine 1.5 degrees to the right.



If youâ€™re flying straight-and-level behind a right-hand tractor (Rotax 912, 914), each time a blade passes over the top of the ark, its pitch is effectively reduced by 1.5 degrees and as it swings through the bottom of the ark, its effective pitch is increased by 1.5 degrees.  This means that your propeller is producing significantly more thrust from the bottom half of the propeller disc than the top half â€“ and that produces a pitch up change in attitude â€“ and not the sideways thrust you had hoped to achieve by mounting the engine sideways.



â€œSo if thatâ€™s true, why has nobody noticed this pitch up attitude?â€ â€“ a good question (even though I asked it myself).



All Europaâ€™s are fitted with a pitch trimmer â€“ so these effects are unconsciously trimmed out by the pilot during different phases of flight.



â€œAh, but what about the propensity to swing to the left on take-off?â€  - Same thing, different plane.



The  Monowheel sits on the ground at a deck angle of (is it about 12 degrees? I forget) so the engine is now canted up at the front by this amount. At the beginning of the take-off run, the upcoming blade on the left hand side has 12 degrees wound off its effective pitch, while the down going blade on the right has 12 degrees added to its pitch. This produces significantly more thrust on the right hand side of the disc than the left, resulting in a turning moment to the left. It's a potential problem with all tail-draggers



The Tri-Gear variant of course sits horizontally on the ground, so has none of this asymmetric thrust â€“ so is less prone to dive off to the left on take off; another reason why the Tri-Gear is perceived to be more benign than the Mono.



Canting an engine is a very crude way of addressing a relatively transient problem â€“ Fitting a rudder trimmer would be a far more elegant solution â€“ should it be necessary.



Hope that wasnâ€™t too long winded!



Nigel



PS the roll issue has nothing to do with engine position.





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budyerly(at)msn.com
Guest

Posted: Mon Jan 16, 2017 7:35 am Post subject: 1.5 degrees right?

To All, 

An airplane is 20,000 compromises flying in close formation.  Each change we make affects others, and some are necessary to fine tune the aircraft for normal  operations. 

  

Off the very empty top of my head: 

From an aero standpoint, fuselage squareness, tail squareness, wing incidence differences in construction, etc. cause most of our trim problems at cruise in  the Europa. 

As for rudder/fin offset vs. engine offset to correct for P factor, drag due to tail area for an offset to counteract the slipstream and P factor affect is  small at cruise for each.  However, in a full power 914 with Airmaster on takeoff and climb out, the rudder required to  hold yaw in check is reduced with offset.  Interesting to note is in propeller testing, if you trim a plane for perfect ball with a fixed  pitch, then put on a constant speed, a touch more right rudder is required to hold the wings level and the ball solidly in the center.  Reduce power on the Constant Speed prop and suddenly left rudder is needed.  I prefer engine offset myself as the offset  is really small (a degree or so) to accommodate P factor and slipstream yaw.  Offsetting the rudder/fin on a short fuselage and induced drag becomes a factor.  A one degree offset of the rudder is .01 Cd which is not much drag or about 5 pounds per degree  on a 15 sq ft fin/rudder, but it is drag, whereas prop offset drag is nill and the loss of thrust is nill also at such low angles.  I agree with the Europa designers, as does David and others, drag is drag.  On Classics in my shop, the offset on an 80HP fat  nosed Classic was very little.  Letâ€™s face it, the instructions said align the engine with the cowl.  If you cut the cowl, who knows what you have without measuring.  But on the Classic, that was not mentioned.  Oh well, progress was made with the XS. 

  

The light propeller aircraft is trimmed for one airspeed and power setting.  Change speed, weight (angle of attack), propeller length or pitch, or power setting  and the trim in pitch and roll due to yaw changes.  Since the fuselage longitudinal axis and engine are at the same pitch setting, the small yaw offset of the engine is not going to be much, nor is a yaw due to fin trim.  Normally, the 1 and 1/16 inch offset  is fine and if not, I decrease the length of the right/left rudder cable about Â½ inch to spring the rudder over a bit on some aircraft to trim the ball.  However, for any roll and yaw combined problem, I would look at a droopy flap.  Somehow flaps sometimes  get leaned on and just a 1/16 of an inch flap droop is quite a bit of roll and yaw.  Whereas changing the engine offset will be very little yaw (and small roll). 

  

Fly the plane and center the ball.  If it is still rolling it is most likely your wing trim.  Either a flap is drooping, or somehow spring has been built into  your ailerons.  (Spring in the ailerons is seen when the stick does not stay exactly where it is put on the ground.  Some builders build in problems that cause the aileron to spring one direction or the other.)  Also look at your wing drag covers, and pants  on a Trigear for alignment.  A droopy wheel pant due to rough field operations is quite a bit of drag as are the wing flap bracket covers if misaligned. 

  

When the ball can be centered and all roll stops (pat yourself on the back for well trimmed wings) your problem is most likely P factor.  Shorten the cable  on the side of the rudder is depressed will normally fix it.  If that is not enough, then a tab (or stronger spring) is necessary on that side.  Keeping a plane well trimmed out is a constant problem.  Every 5 years, look hard at the plane as due to wear and  tear, things get out of alignment.  Any change from your original fly off trim settings must be investigated, as something has changed. 

  

Just my thoughts. 

  

Bud Yerly 

Iâ€™m pulling in 12AY soon for Sun n Fun prep.  Join us this year in Lakeland and meet up with Club members and Europafiles alike at site N-55 again this year  and get away from the winter doldrums.  Our display emphasis this year will be on the Airmaster propeller which was a game changer for transforming the Europa and many other aircraft into efficient cruising airplanes. 

    

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of davidjoyce(at)doctors.org.uk

 Sent: Monday, January 16, 2017 5:42 AM

 To: europa-list(at)matronics.com

 Subject: Re: Europa-List: Re: 1.5 degrees right? 

 

 

  

Nigel, following on from this, I am most reluctant to believe that Ivan Shaw and Don Dykins (one of the outstanding aerodynamicists of our time!) got it wrong, or for that matter generations  of designers of Spitfire/Hurricane era aircraft - which I believe al had engine offset and  fin offset incorporated, but even so were close to unmanageable if full power was used on take off. Performance then was very much a matter of life and death and an  immense amount of research went into optimising performance - I certainly don't buy the notion that folk have always done it because  someone did it back in the dark ages and no-one has thought rationally about it since! 

    Offsetting the engine 1.5 degrees makes negligible difference to forward thrust - actually reduces it by just 0.03%, but using permanent right rudder induces extra drag which must be   an appreciably greater amount. 

    Regards, David Joyce, GXSDJ 

   

  

 

On 2017-01-16 09:58, JonSmith wrote:  	  Quote: 	
		    	  Quote: 	
		  --> Europa-List message posted by: "JonSmith" <jonsmitheuropa(at)tiscali.co.uk (jonsmitheuropa(at)tiscali.co.uk)> Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. I remember quite well the famous diagram of the propeller slipstream helix spiralling around the fuselage and whacking the fin on one side or the other depending on direction of engine rotation - in our Rotax-Europa case the left side of the fin causing the nose to yaw more and more to the left with increasing power.  Certainly in my aircraft on the rare perfectly calm and smooth day with no other influencing factors I notice on take off that at the point of lift off a considerable amount of right rudder input is required at that point, nearly half I'd say.   I suppose that aircraft design is always a compromise and there are various solutions to counter this problem, engine offsets, rudder trims (fixed and inflight adjustable), offset fins etc, all designed to help make life easier for the poor pilot who has to cope with the cacophony of forces his machine is constantly bombarded with!  Our Europa is as basic as you can get in it's standard form with the options of an offset engine mounting and/ or fixed rudder trim tab or nothing!   I note and accept what you say about an engine offset causing inefficiencies and undesirable handling tendencies and that from a perfect performance point of view it would be absolutely the best for the engine to be mounted square on to the airflow but wouldn't the overall effect of the thrust vector being offset completely outweigh these minor undesirable tendencies and make life easier for the pilot?  My instinct tells me that the unwanted effects would be relatively insignificant but I genuinely don't know....!   	
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		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
0  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
1  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
2  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
3  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
4  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
5  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
6  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
7  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
8  	  Quote: 	
		  Hi Graham, I found your posting most interesting and thought provoking.  You go beyond my old "pilot book"!   We are all familiar to a certain extent with the old classic theories of propeller effects; torque, asymmetric blade, gyroscopic etc but I'd never considered detrimental effects caused by an engine offset. 	
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nigel_graham(at)m-tecque.
Guest

Posted: Tue Jan 17, 2017 6:04 am Post subject: 1.5 degrees right?

Hi Bud,



Another gem of a post that will be copied into my burgeoning "Bud's  

Tips" folder.



I agree with nearly all of what you say but as is always the case; a  

good explanation prompts another question.



You have discussed the aerodynamic pros and cons, but of equal  

importance is the mechanical consequence of an offset engine.



The apparent pitch difference of blade rotating around an offset  

engine will be double the engine offset.  A blade will experience a  

change from -1.5 to +1.5 â€“ so a delta of 3 degrees. Now if a customer  

of yours came to you with a fixed pitch Warpdrive, and you discovered  

he had set one blade 3 degrees coarser than the rest â€“ Iâ€™m pretty sure  

you would send him away with a flee in his ear and tell him to correct  

it. But we seem quite happy to accept the same degree of blade  

variance if we offset our engine â€“ without question.



The constantly fluctuating angle of attack introduces cyclic loading  

and unloading of the blades which can produce torsional vibration.

This is then transmitted to the swash plate and drive pins of the  

constant speed unit â€“ which is not a good thing.



A good buddy of mine (and one of your fellow countrymen) has a  

successful business designing and building custom propellers and wings  

for the Formula 1 Reno boys. He showed me a picture of one of his  

custom two-blade fixed pitch props that had failed catastrophically  

during a race. It was unusual in that it had split from tip to root.  

All calculations indicated that it should have been more than strong  

enough to absorb the power; however the prop had failed due to extreme  

torsional oscillation along the blade length.  By working closely with  

the owner, he was able to establish that the plane builder had offset  

the engine.  A new (identical) prop was made, the engine offset zeroed  

out â€“ and the racer went on to win gold â€“ with no further problems. It  

was during one of our â€œsitting by the pool drinking beer and talking  

planesâ€ sessions that he first asked what I was going to do regarding  

the offset of my then new Europa. â€¦â€¦ it got me thinking.



Now with regard to the suggestion of fitting a rudder trimmer (purely  

hypothetical as I have no plans to take a saw to my fin), I was a  

little surprised by the strength of reaction to this suggestion on the  

grounds of increased drag. I am also curious as to why our attitude to  

controlling yaw trim is so different to the way we control pitch trim.



The pitch control system uses an all flying tailplane with a (very  

good) trim system. According to Don Dykins book, during the cruise,  

the tailplane is constantly â€œflyingâ€ the rear of the aircraft  

downwards to maintain level flight. This will be generating drag too â€“  

but we accept this without question!



When considered against the cumulative drag created by the nose wheel  

, main gear, outriggers tailwheel, flap hinges, GPS antenna fuel  

vents, strobes and door handles, surely, the extra drag of a rudder  

trimmer would pail into insignificance but surely make life so much  

easier in the climb out or cruise.



I have re-read my original response to Jonathan and I stand by  

everything I said. I think the explanation of the aerodynamics is  

accurate (certainly nobody has challenged it) and my advice that â€œif  

it ain broke, donâ€™t fix itâ€ also stands.



For every pilot happily flying a Classic with no engine offset and  

reporting no problems, there seems to be another flying an XS with  

offset experiencing problems. I suspect that the real explanation is  

muscle memory. Experienced feet will move by themselves without the  

owner even being aware. Those with slower feet will find themselves  

â€œbehind the curveâ€.



Keep the thoughts coming.



Nigel

-----------------------------------------------------------



Quoting Bud Yerly <budyerly(at)msn.com>:



 	  Quote: 	
		   To All,

 An airplane is 20,000 compromises flying in close formation.  Each  

 change we make affects others, and some are necessary to fine tune  

 the aircraft for normal operations.



 Off the very empty top of my head:

 From an aero standpoint, fuselage squareness, tail squareness, wing  

 incidence differences in construction, etc. cause most of our trim  

 problems at cruise in the Europa.

 As for rudder/fin offset vs. engine offset to correct for P factor,  

 drag due to tail area for an offset to counteract the slipstream and  

 P factor affect is small at cruise for each.  However, in a full  

 power 914 with Airmaster on takeoff and climb out, the rudder  

 required to  hold yaw in check is reduced with offset.  Interesting  

 to note is in propeller testing, if you trim a plane for perfect  

 ball with a fixed pitch, then put on a constant speed, a touch more  

 right rudder is required to hold the wings level and the ball  

 solidly in the center.  Reduce power on the Constant Speed prop and  

 suddenly left rudder is needed.  I prefer engine offset myself as  

 the offset is really small (a degree or so) to accommodate P factor  

 and slipstream yaw.  Offsetting the rudder/fin on a short fuselage  

 and induced drag becomes a factor.  A one degree offset of the  

 rudder is .01 Cd which is not much drag or about 5 pounds per degree  

 on a 15 sq ft fin/rudder, but it is drag, whereas prop offset drag  

 is nill and the loss of thrust is nill also at such low angles.  I  

 agree with the Europa designers, as does David and others, drag is  

 drag.  On Classics in my shop, the offset on an 80HP fat nosed  

 Classic was very little.  Letâ€™s face it, the instructions said align  

 the engine with the cowl.  If you cut the cowl, who knows what you  

 have without measuring.  But on the Classic, that was not mentioned.  

  Oh well, progress was made with the XS.



 The light propeller aircraft is trimmed for one airspeed and power  

 setting.  Change speed, weight (angle of attack), propeller length  

 or pitch, or power setting and the trim in pitch and roll due to yaw  

 changes.  Since the fuselage longitudinal axis and engine are at the  

 same pitch setting, the small yaw offset of the engine is not going  

 to be much, nor is a yaw due to fin trim.  Normally, the 1 and 1/16  

 inch offset is fine and if not, I decrease the length of the  

 right/left rudder cable about Â½ inch to spring the rudder over a bit  

 on some aircraft to trim the ball.  However, for any roll and yaw  

 combined problem, I would look at a droopy flap.  Somehow flaps  

 sometimes get leaned on and just a 1/16 of an inch flap droop is  

 quite a bit of roll and yaw.  Whereas changing the engine offset  

 will be very little yaw (and small roll).



 Fly the plane and center the ball.  If it is still rolling it is  

 most likely your wing trim.  Either a flap is drooping, or somehow  

 spring has been built into your ailerons.  (Spring in the ailerons  

 is seen when the stick does not stay exactly where it is put on the  

 ground.  Some builders build in problems that cause the aileron to  

 spring one direction or the other.)  Also look at your wing drag  

 covers, and pants on a Trigear for alignment.  A droopy wheel pant  

 due to rough field operations is quite a bit of drag as are the wing  

 flap bracket covers if misaligned.



 When the ball can be centered and all roll stops (pat yourself on  

 the back for well trimmed wings) your problem is most likely P  

 factor.  Shorten the cable on the side of the rudder is depressed  

 will normally fix it.  If that is not enough, then a tab (or  

 stronger spring) is necessary on that side.  Keeping a plane well  

 trimmed out is a constant problem.  Every 5 years, look hard at the  

 plane as due to wear and tear, things get out of alignment.  Any  

 change from your original fly off trim settings must be  

 investigated, as something has changed.



 Just my thoughts.



 Bud Yerly

 Iâ€™m pulling in 12AY soon for Sun n Fun prep.  Join us this year in  

 Lakeland and meet up with Club members and Europafiles alike at site  

 N-55 again this year and get away from the winter doldrums.  Our  

 display emphasis this year will be on the Airmaster propeller which  

 was a game changer for transforming the Europa and many other  

 aircraft into efficient cruising airplanes.



 From: owner-europa-list-server(at)matronics.com  

 [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of  

 davidjoyce(at)doctors.org.uk

 Sent: Monday, January 16, 2017 5:42 AM

 To: europa-list(at)matronics.com

 Subject: Re: Re: 1.5 degrees right?

 Nigel, following on from this, I am most reluctant to believe that  

 Ivan Shaw and Don Dykins (one of the outstanding aerodynamicists of  

 our time!) got it wrong, or for that matter generations of designers  

 of Spitfire/Hurricane era aircraft - which I believe al had engine  

 offset and  fin offset incorporated, but even so were close to  

 unmanageable if full power was used on take off. Performance then  

 was very much a matter of life and death and an immense amount of  

 research went into optimising performance - I certainly don't buy  

 the notion that folk have always done it because  someone did it  

 back in the dark ages and no-one has thought rationally about it  

 since!



     Offsetting the engine 1.5 degrees makes negligible difference to  

 forward thrust - actually reduces it by just 0.03%, but using  

 permanent right rudder induces extra drag which must be  an  

 appreciably greater amount.



     Regards, David Joyce, GXSDJ





 On 2017-01-16 09:58, JonSmith wrote:



 

 <jonsmitheuropa(at)tiscali.co.uk<mailto:jonsmitheuropa(at)tiscali.co.uk>>



 Hi Graham, I found your posting most interesting and thought  

 provoking.  You go beyond my old "pilot book"!   We are all familiar  

 to a certain extent with the old classic theories of propeller  

 effects; torque, asymmetric blade, gyroscopic etc but I'd never  

 considered detrimental effects caused by an engine offset.



 I remember quite well the famous diagram of the propeller slipstream  

 helix spiralling around the fuselage and whacking the fin on one  

 side or the other depending on direction of engine rotation - in our  

 Rotax-Europa case the left side of the fin causing the nose to yaw  

 more and more to the left with increasing power.  Certainly in my  

 aircraft on the rare perfectly calm and smooth day with no other  

 influencing factors I notice on take off that at the point of lift  

 off a considerable amount of right rudder input is required at that  

 point, nearly half I'd say.



 I suppose that aircraft design is always a compromise and there are  

 various solutions to counter this problem, engine offsets, rudder  

 trims (fixed and inflight adjustable), offset fins etc, all designed  

 to help make life easier for the poor pilot who has to cope with the  

 cacophony of forces his machine is constantly bombarded with!  Our  

 Europa is as basic as you can get in it's standard form with the  

 options of an offset engine mounting and/ or fixed rudder trim tab  

 or nothing!



 I note and accept what you say about an engine offset causing  

 inefficiencies and undesirable handling tendencies and that from a  

 perfect performance point of view it would be absolutely the best  

 for the engine to be mounted square on to the airflow but wouldn't  

 the overall effect of the thrust vector being offset completely  

 outweigh these minor undesirable tendencies and make life easier for  

 the pilot?  My instinct tells me that the unwanted effects would be  

 relatively insignificant but I genuinely don't know....!



 I've always considered that aircraft compromised by simplicity would  

 in the ideal world be set up to fly perfectly straight and balanced  

 with hands and feet off in the cruise as that's what we spend most  

 of the time doing.  Thus in a perfect aircraft with the engine  

 correctly offset this should be achieved without any extra trim  

 tabs, assuming the designer got his sums correct with the offset!   

 (I'm lucky I think because my aircraft seems to achieve this quite  

 nicely!).  I also note that you believe a rudder trim tab to be a  

 better solution than an engine offset.  Do you consider that having  

 the rudder permanently offset into the airflow to keep the aircraft  

 balanced to be more efficient than the minor unwanted propeller  

 blade effects caused by having an engine offset?  Again I'm only  

 asking the question because I genuinely don't know..!



 I believe that a correctly offset engine will assist the pilot  

 during take off by reducing the amount of right rudder deflection  

 required throughout.  Without any offset to help, surely more right  

 rudder deflection would be needed to keep straight thus effectively  

 reducing the maximum crosswind component from the left that the  

 aircraft itself could cope with?  A rudder trim would not help this  

 situation of course - it might make reduce the load on the pilot's  

 leg but the actual rudder deflection is still required.



 As I say, an interesting post, I'm very open minded but am yet to be  

 convinced that I have made a mistake by following the manual and  

 building mine WITH the quoted 1.5 degree offset....!



 --------



 G-TERN



 Classic Mono



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pjeffers(at)talktalk.net
Guest

Posted: Tue Jan 17, 2017 7:26 am Post subject: 1.5 degrees right?

Hi Nigel,

You obviously did not read either my message or the Classic build manual which states that the engine offset on the classic is achieved by adjusting the washers in order to align the prop with the cowlings.  Inference is that the cowlings had the offset built into them.

Pete



--

nigel_graham(at)m-tecque.
Guest

Posted: Tue Jan 17, 2017 8:58 am Post subject: 1.5 degrees right?

Hi Pete,



I have read both.

I've also seen cowlings that have had their firewall face trimmed to  

allow the aperture to align with the propeller hub.

As you say "it was a bit crude but seemed to work".

Nigel

Quoting Peter Jeffers <pjeffers(at)talktalk.net>:



 	  Quote: 	
		   



 Hi Nigel,

 You obviously did not read either my message or the Classic build  

 manual which states that the engine offset on the classic is  

 achieved by adjusting the washers in order to align the prop with  

 the cowlings.  Inference is that the cowlings had the offset built  

 into them.

 Pete

JonathanMilbank

Joined: 14 Apr 2012
Posts: 388
Location: Aberdeen area

Posted: Tue Jan 17, 2017 1:13 pm Post subject: Re: 1.5 degrees right?

I've read and re-read all of your comments with much interest and there's one observation I'd like to make. I'm fairly sure that the early Classic Europas had no engine offset and that the designers might have thought it unnecessary with only 80hp from a 912UL. The 912S wasn't available then.



My reasons for thinking this are that the topic never got mentioned by anyone at any time. The brilliant Don Dykins makes no mention of it to my knowledge in his paper "Understanding the Aerodynamics of your Europa".



Furthermore when I was building my aircraft over 20 years ago, the cowls needed at least as much trimming and fettling as do the XS cowls to get them to match the fuselage, which makes it seem unlikely that the cowls on the Classic were serving as datum for correct engine/propeller alignment.



My final reason is of the "proof of the pudding" variety, in that my Classic has a very pronounced swing to the left when applying power at low speed. Not that I noticed it, but someone else who was unfamiliar with my Europa definitely did notice.

dpark748(at)icloud.com
Guest

Posted: Tue Jan 17, 2017 1:50 pm Post subject: 1.5 degrees right?

This is from the Rotax Installation Manual.

Dave  



The engine mounting frame has been designed with the engine offset to the right by 1.5Â°. To check

that this offset is correct, clamp a straight edge to the propeller flange horizontally and mark a point

51 cm (20") each side of the engine centre line. Measure the distance from these points, parallel to the

aircraft centre line, to the firewall. The difference between the two readings should be 26 mm

(1 1/16"). If any correction is found necessary, shim between the landing gear frame and the

appropriate cup washer using AN960-516L washers. In order to ensure that the split pin is correctly

positioned relative to the castellated nut it will be necessary to use a total of at least 4 washers on each

bolt. Any washers that are not needed to act as positioning shims should be placed immediately

under the nut. Make a note of where and how many shim washers are used for later reference.



Dave Park

 	  Quote: 	
		   On 17 Jan 2017, at 21:13, jonathanmilbank <jdmilbank(at)yahoo.co.uk> wrote:

 

 

 

 I've read and re-read all of your comments with much interest and there's one observation I'd like to make. I'm fairly sure that the early Classic Europas had no engine offset and that the designers might have thought it unnecessary with only 80hp from a 912UL.

 

 My reasons for thinking this are that the topic never got mentioned by anyone at any time. The brilliant Don Dykins makes no mention of it to my knowledge in his paper "Understandings the aerodynamics of your Europa".

 

 Furthermore when I was building my aircraft over 20 years ago, the cowls needed at least as much trimming and fettling as do the XS cowls to get them to match the fuselage, which makes it seem unlikely that the cowls on the Classic were serving as datum for correct engine/propeller alignment.

 

 My final reason is of the "proof of the pudding" variety, in that my Classic has a very pronounced swing to the left when applying power at low speed. Not that I noticed it, but someone else who was unfamiliar with my Europa definitely did notice.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=465169#465169

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