Upper cowl alignment for engine sag

Camillo · #1 11-22-2009, 10:05 AM

Hi. I'm about to reach the non returning point with cowl and was wondering how much engine will sag, in order to match as close as possible the final profile.
Manual says to align "upper cowl up end below spinner" to tak into account for engine sag.
Since I'm italian and I cannot catch every meaning, it seems to me - after having read a few posts on the subject - that I have to centralize the front round ring and then adjusting it slightly below because of the engine will sit slightly after few hours working. But the "up end" is still 6/32'' ABOVE spinner edge. It sound very strange it should be placed BELOW the edge: I guess it is nearly impossible that engine will sag so much (approx. 1'')
But, the question is: how much will I have to go down? Now, looking at the external ring, I have approx. 6/32'' up and 10/32'' down, from its edges. Some other builder wrote he went with 0,5 cm. below the ideal position, but it is not stated if this was enough or too much after flying.
I understand that modifying cowl position after installation would be really tough...
Thanks

pierre smith · #2 11-22-2009, 11:57 AM

...Camillo. Don't overthink this section of your build. My recommendation is to level the cowl with the top edge of the spinner backplate and expect a 1/4" sag in about a year...18 months and it will be nearly centered on the cowl.

Best,

Camillo · #3 11-22-2009, 04:04 PM

Thank-you, Pierre.
So, I have to lower it a little bit more.
Tomorrow morning I will fix it and go on...
Thanks.
Camillo

Radomir · #4 11-22-2009, 05:25 PM

If you use those crappy VI engine mounts, then bad sagging is expected... Lord mounts don't sag nowhere near as much... mine didn't sag at all until I put a heavy Hartzell on.. and then it sagged 1/32" or so.. hard to tell...

Bavafa · #5 11-22-2009, 06:28 PM

I was contemplating the same thing when I was finishing my cowl. After much researched, I end up setting it up almost perfectly all around and crossed my fingers for the best. I just checked it last night as I was waxing the cowl and after six months and 130 hours, it seems it is about 1 or 2/32" lower and possibly a bit to the right but it is very hard to tell.

I have the Lord mounts and CS Harzell.

Good luck
Mehrdad
RV7A - IO360M1B

Doug · #6 11-22-2009, 11:51 PM

Quote:

Originally Posted by Radomir

If you use those crappy VI engine mounts....

Hey Radomir,
What brand are the 'VI' mounts? I hope you don't mean Barry.
Doug

Now answering my own question!!! - VIP mounts are 'Vibration Isolation Products' brand not to be confused with the Barry or Lord brands.

Camillo · #7 11-23-2009, 01:17 AM

I have Lord mounts on a Dyna1 mount with O320 and Hartzell c/s propeller. All new bought from Van's one year ago.