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Engine thrust angle

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Posted

I am putting in a Yamaha into my Mk4. I understand you want 3-4 degrees to port , but what about up or down? Where is the water line on a mk4? Fire wall is guite a bit diff than bottom of fuse

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Posted (edited)

I am putting in a Yamaha into my Mk4. I understand you want 3-4 degrees to port , but what about up or down? Where is the water line on a mk4? Fire wall is guite a bit diff than bottom of fuse

Now you got me scratching my head - Why would you set a right-turning prop to port side, when you are giving it right rudder to counteract turning in that direction with power applied?  My Ercoupe engine was offset one way or the other, and slightly down, but that was a different bird.  I learned about "Precession" in school, but that was long-long ago.  The more you offset your engine, the more the cowl don't fit.   Unless I had definitive numbers, I would put it straight ahead.   Right rudder will hold it straight.   EDMO

Edited by EDMO

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Posted

 Does the Yamaha prop turn the same as the Rotax 912?  (right hand)  If it does, I would think copying where a 912 mount puts the prop would probably be a good place to start.   JImChuk

 

 

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Posted (edited)

 Does the Yamaha prop turn the same as the Rotax 912?  (right hand)  If it does, I would think copying where a 912 mount puts the prop would probably be a good place to start.   JImChuk

 

 

The Vertical Stabilizer is easier to offset than the engine.  I don't know if your Avid VS was built offset for a left-turning 582 engine or VS set straight.  EDMO

Edited by EDMO

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Posted

The MK IV VS is straight.  I remember John Miller talking about when he put a Jabiru  (right hand prop) on a B model Avid.   The B model VS was off set for a Rotax 2 stroke engine   (left turning prop)  He put a trim tab on his rudder to make the plane fly straight.  Doesn't seem like it was that big a deal if my memory is correct.   JImChuk

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Posted (edited)

The MK IV VS is straight.  I remember John Miller talking about when he put a Jabiru  (right hand prop) on a B model Avid.   The B model VS was off set for a Rotax 2 stroke engine   (left turning prop)  He put a trim tab on his rudder to make the plane fly straight.  Doesn't seem like it was that big a deal if my memory is correct.   JImChuk

Nothing is going to be perfect at all speeds and power settings - Only an adjustable VS or adjustable trim tab on rudder might help.  That's why larger planes have them.   Engine offset wont.  I just set my Soob straight - Not enough $$$$$ or wind tunnels to make that kind of Engineering decision.   EDMO

Edited by EDMO

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Posted (edited)

Yamaha with c box is left turning, like a 582 c box.

So opposite of 912.

So jared i think a little left is correct.

Avid experts, the question remains on up/down tilt.

Go perpendiculal to firewall?

(That was my KF5 answer)

Edited by Yamma-Fox

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Posted (edited)

Yamaha with c box is left turning, like a 582 c box.

So opposite of 912.

So jared i think a little left is correct.

Avid experts, the question remains on up/down tilt.

Go perpendiculal to firewall?

(That was my KF5 answer)

Agree - still nothing is perfect.  I think Fred Wieck put the down angle on the Ercoupe engine to keep pressure on the steerable nose wheel on the ground - there were no individual rudder pedals - You still put down pressure on the elevator for positive steering until ready to rotate.   EDMO

Edited by EDMO

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Posted

I'm wondering if the thrust angel should be figured more off the incidence of the wing.  You raise the tail to a specific place to do a weight and balance.  Up/down angel of thrust maybe should be figured from that place.  Firewall could be at any angel, and different from one aircraft type to the next.   JImChuk

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Posted (edited)

I don't know how far it is from firewall to prop flange on the SnoGo engine, but figuring .017" offset per degree of angle per inch - If it is say, 26" and you want 4 degrees offset, then the prop flange would be 1.768" to left of center line on firewall.   Easy to figure offsets.  EDMO

Edited by EDMO

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Posted

Leni,  if you are following any of this thread, where did you locate the prop hub on  the Avid 912 motor mount you built a few months back?  Any flight reports for that mount?  JImChuk

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Posted

I would move the back of the motor and leave the prop centered in the cowling cut out. Do the avids fly tail down our level? Can somebody check the prop flange to fire wall with either 582 912 or soob. This is a measurement I should have taken before selling my 582. To night I sat the motor in the rough location, it looks like if I cut two tubes out of the way and reroute I could move the motor back 3.5 inches is this worth 5 hrs work? I know my time is not worth shit but I do want to be done and flying someday, you guys are great.

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Posted (edited)

I would move the back of the motor and leave the prop centered in the cowling cut out. Do the avids fly tail down our level? Can somebody check the prop flange to fire wall with either 582 912 or soob. This is a measurement I should have taken before selling my 582. To night I sat the motor in the rough location, it looks like if I cut two tubes out of the way and reroute I could move the motor back 3.5 inches is this worth 5 hrs work? I know my time is not worth shit but I do want to be done and flying someday, you guys are great.

IMO, The farther back you can get that engine is worth the trouble with a short fuselage - You are going to have a problem getting your CG back anyway.  My Soob is so close to the firewall that I need to put a dent in the firewall to get the alternator belt on.  Sorry, I am not able to go measure anything for you.  The Soob is probably different than yours will be with the C-drive on it anyway.   EDMO

Edited by EDMO

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Posted

I would move the back of the motor and leave the prop centered in the cowling cut out. Do the avids fly tail down our level? Can somebody check the prop flange to fire wall with either 582 912 or soob. This is a measurement I should have taken before selling my 582. To night I sat the motor in the rough location, it looks like if I cut two tubes out of the way and reroute I could move the motor back 3.5 inches is this worth 5 hrs work? I know my time is not worth shit but I do want to be done and flying someday, you guys are great.

IMO, The farther back you can get that engine is worth the trouble with a short fuselage - You are going to have a problem getting your CG back anyway.  My Soob is so close to the firewall that I need to put a dent in the firewall to get the alternator belt on.  Sorry, I am not able to go measure anything for you.  The Soob is probably different than yours will be with the C-drive on it anyway.   EDMO

I would lengthen the fuse if I could find out where to cut. It looks like a lot of work with the rudder cables replace  elevator trim cable  replace and realigning the elevator pushrod tube.

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Posted (edited)

I would move the back of the motor and leave the prop centered in the cowling cut out. Do the avids fly tail down our level? Can somebody check the prop flange to fire wall with either 582 912 or soob. This is a measurement I should have taken before selling my 582. To night I sat the motor in the rough location, it looks like if I cut two tubes out of the way and reroute I could move the motor back 3.5 inches is this worth 5 hrs work? I know my time is not worth shit but I do want to be done and flying someday, you guys are great.

IMO, The farther back you can get that engine is worth the trouble with a short fuselage - You are going to have a problem getting your CG back anyway.  My Soob is so close to the firewall that I need to put a dent in the firewall to get the alternator belt on.  Sorry, I am not able to go measure anything for you.  The Soob is probably different than yours will be with the C-drive on it anyway.   EDMO

I would lengthen the fuse if I could find out where to cut. It looks like a lot of work with the rudder cables replace  elevator trim cable  replace and realigning the elevator pushrod tube.

Even with a long fuselage, I would try to set that engine back as far as possible.  I think you will appreciate the effort someday.   The Airdale was stretched, and they put the Soob as far back as mine is.   EDMO

Edited by EDMO

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Posted

Setting it back farther might save some cowl rework time too?

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Posted

Setting it back farther might save some cowl rework time too?

exactly. in length but not height . Received motor mount material and exhaust material today. am going to catch you:BC: Was thinking of naming my wife's plane  shock and awe. Awe for when it breaks.   

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Posted

So - Suberavid had 6.5 degrees down on his engine, and it was supposed to be 1.5 - Looks like anything with a fan on it will fly - just maybe not the same!   My nosedragger starts out level, compared to the engines on taildraggers  which would point upward more unless angled down - That is why my engine is level instead of down - and the Pelican mount was built that way.  Will it fly?  Yes.  How will it fly?  Only flying will tell.   EDMO

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