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Engine alignment

J

Jackm

Well Known Member
Mounted engine last night....stood back and did one of those " now that is awesome.....wait its off center" then the measuring started....
Is it p factor that engine is not aligned with aircraft centerline? Is cowl compensated for angle to maintain parallel with spinner back plate?

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Thanks for your time.
 
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After much research, due to a flightsim thing (need some perfection, even for a computer)..............I've concluded that the offset is built in to reduce in-flight effects of torque. As we notice, we don't have a constant rolling effect once off the ground........unless it's too much power with low airspeed.

More than not, aircraft are built with this offset. When I spent years building R/C, they all had an offset too. One explanation is the increased airflow over the left wing, which increases/decreases with power/torque. Much better than a different incidence in wings or permanent trim tabs.

If anyone has more ideas on this subject, I'd like to hear them.

L.Adamson
 
Jackm said:
Mounted engine last night....stood back and did one of those " now that is awesome.....wait its off center" then the measuring started....
Is it p factor that engine is not aligned with aircraft centerline? Is cowl compensated for angle to maintain parallel with spinner back plate?

home


Thanks for your time.
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I would recommend you reference the plans for exact offset. Then adjust everything else as necessary after the engine is aligned.
 
Don't worry about it--the kit parts and instructions account for this to the point it's not even addressed, it's just built in to everything so there's nothing you have to do about it. I'm just finishing up my cowl right now-- believe me, just follow the plans and you won't have any issues.
 
paul330 said:
Yeah, just like the doors......... :D

But you are right, the offset is all transparent and just happens.
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I didn't say it would be easy! :eek::p:D Actually the biggest pain in the arse for me is I have been doing all of this solo (cabin top install, doors, wing install, engine hanging, prop hanging, cowl, etc). I spend as much time figuring out how to get things where I need them and hold them there as I do actually working on the parts.
 
It was one of those moments that I thought I had just past my 1001 mistake on the project....Mind you my mentor in Montana is trying to tell me I have the engine mounted on upside down and the prop is driven off the spare mag hole:)
It does intrique me though that Vans incorporated this into the engineering...kinda like the flap reflex, I appreciate the engineering that goes into these aircraft that probably contribute to them being a remarkable aircraft to fly! Good on you Vans!!

Does this mean my flight instructor that i used on my first flight in 172 wont be yelling at me "Right Rudder.Rudder RUDDER you idiot I said RUDDER"?

As of the doors....lots of work but walk in the park...only suggestion....do not use the two fore and aft dimple indicators! Doors will be mounted too low in fuse.

another question for you all....does anyone have a prop hub I can buy to mount my cowl with? Be easier than working around prop I would imagine
 
Jackm said:
Does this mean my flight instructor that i used on my first flight in 172 wont be yelling at me "Right Rudder.Rudder RUDDER you idiot I said RUDDER"?
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No. You still need to use rudder to counteract P-factor.

another question for you all....does anyone have a prop hub I can buy to mount my cowl with? Be easier than working around prop I would imagine
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Generally, people that do the cowl without the prop installed just make some PVC spacers to simulate the hub. There's a thread somewhere on here that talks to the right size the spacers need to be as IIRC, what Van's says to use is too short. http://www.vansaircraft.com/public/construction-faq.htm Anyway, I have my prop (2-blade Hartzell) installed and it doesn't get in the way. However, I can see if you have a 3-blade prop that it would be easier to do the cowl without the prop on.
 
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Lots of rudder.

Jackm said:
Does this mean my flight instructor that i used on my first flight in 172 wont be yelling at me "Right Rudder.Rudder RUDDER you idiot I said RUDDER"?
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You'll be using a boatload of right rudder on takeoff. The -10's vertical fin is not offset like the -7,-8 and -9.

Best,
 
Thanks for your input.
Interesting info out there on best performing angle. Also, I wondered if the variety of prop choices make a difference on this topic?

Any chance anyone has prop hub to sell?
 
Jack,

Might as well buy the prop now and lock the installation in. Using 'other parts' may give you mixed results. The PVC spacer method is not totally reliable and can also result in misfit if you are not really careful. There is quite a bit variation on prop hubs depending on what you are actually using in the end. Best to simply get your prop you are going to use on hand and then you know the fit will be correct. Remove the prop and store when you are done if you are space constrained.

Great visiting you guys last week!
 
Thanks Joe

We bought prop from Vans and have it in shop.....just trying to avoid scratching it and reduce the amount of times my head will contact it during cowling fit:)

Thanks to you and Trisha for coming to visit..the 10 is on its gear, engine on, tail closed and wired since you seen last......got a picture of the smoke show you did with your 6.....rare occation in Prosser!

Thanks again
 
Jackm said:
Does this mean my flight instructor that i used on my first flight in 172 wont be yelling at me "Right Rudder.Rudder RUDDER you idiot I said RUDDER"?
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To elaborate on what Todd and Pierre said, the offset is engineered for cruise flight - constant speed and no fast airspeed changes. During takeoff, you are accelerating which increases the torque effects and makes the nose veer to the left without rudder input. Similarly, I notice a slight veering tendency when I flare and the aircraft decelerates - though it's not nearly as abrupt as takeoff because the deceleration is less. Think of it as a cruise trim similar to and in conjunction with the rudder trim.
 
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