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Engine angle on the airframe mounts on a MKIII

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jason(at)trek-tech.com
Guest

Posted: Thu May 07, 2009 7:07 am Post subject: Engine angle on the airframe mounts on a MKIII

Hello All,  

   

I have checked the archives extensively and found some useful information but I would like to take a poll.  

   

In reference to the engine mounts on the airframe of a MKIIIC, what angle does your engine sit at.  Does the engine sit flat (parallel) on the mounts?  Are there any spacers or engine mount holes that make the front of the engine sit higher or lower on the airframe mount.  I Know the effect that engine angle has on yaw trim, I just wanted to see where other people landed on the engine mount.  

   

Jason  

MKIIIC  

BMW engine  

       [quote][b]

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John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu May 07, 2009 7:49 am Post subject: Engine angle on the airframe mounts on a MKIII

Jason:

  

 Over the years I have experimented with changing  engine attitude in pitch and yaw.  I did this with my FS and  MKIIIc.

  

 Results indicated it was not worth the effort of  screwing up good engine mounts.

  

 I believe the stock engine position is as good as  it gets.

  

 I have also experimented with off setting the  leading edge of the upper vertical stabilizer in order to help control adverse  yaw.  Again, was not worth the holes I had to drill in the tailboom to  conduct my experiment.  I found the best solution was to use the  appropriate size rudder trim tab set at the correct angle.

  

 Interesting to note, the new Kolb MKIIIx I tested  last year ended up with an identical size and shape rudder trim tab as on my  much older MKIIIc.

  

 I do like to get the engine as low in the mounts as  I can to help offset some of the adverse pitch down caused by a high thrust line  on a pusher.

  

 The leading edge of my horizontal stabilizer is  somewhat lower than what the plans called for.  Where I have mine set now  is where my mkIII flies best.  Up or down from this position causes the  mkIII to act like it is trying to balance on a ball.  Was difficult to keep  it in a good cruise attitude.  Nose would either want to drop or  climb.  Would be hard to fly all day in that condition.

  

 john h

 mkIII

  

  

 [quote]    In reference to the engine mounts on the    airframe of a MKIIIC, what angle does your engine sit at.  Does the    engine sit flat (parallel) on the mounts?  Are there any spacers or    engine mount holes that make the front of the engine sit higher or lower on    the airframe mount.  I Know the effect that engine angle has on yaw trim,    I just wanted to see where other people landed on the engine    mount.

      

    

Jason   

 

[b]

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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Jason Omelchuck

Joined: 07 May 2009
Posts: 120
Location: Portland Oregon

Posted: Thu May 07, 2009 9:01 am Post subject: Re: Engine angle on the airframe mounts on a MKIII

Thanks John,



Can you tell me if the "stock" position is with the engine parallel (or the prop perpendicular) to the mounts on the airframe or does "stock" mean that the front of the engine is raised or lowered some per the factory instructions.



Jason

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John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu May 07, 2009 9:08 am Post subject: Engine angle on the airframe mounts on a MKIII

> Can you tell me if the "stock" position is with the engine parallel (or 

the prop perpendicular) to the mounts on the airframe or does "stock" mean 

that the front of the engine is raised or lowered some per the factory 

instructions.

 	  Quote: 	
		  

 Jason


	




Jason:



On my mkIII the line of thrust is parallel with the stock engine mounts, and 

as low as I could get the 912 and still have a little clearance to keep from 

hitting the large root tube during flight.



john h

mkIII

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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

NeilsenRM(at)comcast.net
Guest

Posted: Thu May 07, 2009 9:51 am Post subject: Engine angle on the airframe mounts on a MKIII

Jason



I have played around a bit on engine positions and I agree with John, it 

doesn't seem to make any difference. From a purely theoretical view it would 

seem the best thrust line would be having the line of thrust pushing 

straight forward in cruise. Allowing for a few degrees of angle of attack 

for the wing to maintain altitude, I set my line of thrust 2-4 degrees down 

from parallel with the bottom line of the wing. Or 2-4 degrees prop up, 

front of engine down. I had to do this because I had cut to stock engine 

mount off the airframe to be able to lower the engine. Yes the lower the 

thrust line the better. This makes a real big difference.



Rick Neilsen

Redrive VW powered MKIIIC



---

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by0ung(at)brigham.net
Guest

Posted: Sat May 09, 2009 4:45 am Post subject: Engine angle on the airframe mounts on a MKIII

In reference to the engine mounts on the airframe of a MKIIIC, what angle does your engine sit at.  Does the engine sit flat (parallel) on the mounts?  Are there any spacers or engine mount holes that make the front of the engine sit higher or lower on the airframe mount.  I Know the effect that engine angle has on yaw trim, I just wanted to see where other people landed on the engine mount.  

   

Jason  

MKIIIC  

BMW engine  

   

 	  Quote: 	
		  >>>>>>>>>>>>>>.  

   
	


Parallel on the mounts for me.  

   

Boyd Young  

MKIIIC  

Utah  

   

       [quote][b]

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