Cowl Alignment- Yak

[RyanW]

As I am working on the GP Yak 54, I am either really dense this evening or this cowl just will not line up with the prop shaft. GP includes a handy little jig that should make this an absolute snap, but the cowl is way off in one of two ways. First- if you have the front of the cowl flush with the mounting ring, which makes the front flange of the cowl perpendicular to the prop shaft (meaning prop is same distance from the cowl through the entire revolution), then it is not centered with the prop shaft when looking at it from the front. This is really funny looking because the spinner is set off to one side- not cool. Second- if you get the cowl centered exactly upon the prop shaft, then it isn't perpendicular to the axis and the prop is close to one side through a revolution and spaced far away from the other side. I know it sounds crazy, but if you have had this problem you would completely understand!

So, I am looking at errors that I have either done with the assembly of the jig or in my failed attempts at putting this thing together. I mean it's so easy a caveman could do it. (sorry Geico dudes!)

If you guys/gals have any pointers, please let me know.
Thanks!
-Ryan

[RyanW]

Here is a sketch of what I am talking about- angles are exaggerated to show discrepancies.

-Ryan

[krashmaster81]

dang, that alingment is WAY off . . . oooh, angles exagerated to show . . .should have read the fine print.

so, how close are you to the reccomended depth, drivewasher - firewall distance? i'd guess that if you were off here it line up with the pre-set right thrust angle... just a thought. would locating the cowl further aft help any? more space between prop and front of cowl...

[RyanW]

I am at the recommended 6 3/4" distance. Moving the cowl further back only makes it worse. Reason being- the material overlapping the fuselage is preventing it from being installed at the correct angle.
-Ryan

Oh- I fixed your avatar...


-Ryan

[SleepyC]

Some times with cowls that are "open" in the front like a YAK..
Theres not much you can do.

The right thrust is going to move the motor over to the right aout 1/4 inch.

Let me ask you, when you mounted your motor did you accomidate for right thrust?
Most of the time you want to move the motor about 1/4" over to the right (of the center line) to make the motor shaft actually position itself in the center of the cowl. (this accomidates for the right thrust of the motor.)

If it came pre-mounted than it will just be off a bit.

Good luck.

[RyanW]

Thanks SleepyC, it looks like that is exactly what I need to do. Unfortunately the spacer for the engine is epoxied to the firewall. This is going to be a fun one!
-Ryan

ps- there aren't any thrust angle correction things on the helis, we just create thrust where ever the heck we want it

[SleepyC]

One Thing I learned a while back is if you have the room (In your case its only 1/4")
Fill the holes you drilled with a tight fitting dowel rod, and set them with epoxie or Goriilla glue. Let dry and then drill the appropriate holes next to the old ones... seen many of planes have this done when swaping motors... works perfectly!

Good luck!

[GremlinX]

What sleepy said to do.. I did this on my Funtana years ago

[taco]

Thats a very very easy fix!!! Come on now!~!!!