Cowl - Spinner Alignment

lr172 · #1 08-19-2014, 03:06 PM

I just hung the O-320 on the RV-6A yesterday and am now fitting the cowl. I am wondering if folks make a perfect alignment between the cowl and the spinner at this point or do they leave the spinner up a bit to allow for the engine mounts to compress and drop the front of the engine a bit. I used Lord Mounts from Vans. I have no experience to determine whether or not the mounts will compress over time.

I appreciate any guidance that can be provided here.

Thanks,

Larry

lostpilot28 · #2 08-19-2014, 03:12 PM

I set my spinner higher by 3/16 of an inch. After flying for 5 years, it's just barely below "level" with the cowl...maybe 1/8 inch. I think it's smart to set the spinner higher...but by how much is the question.

BTW, I used the standard mounts that came with the FWF kit.

MikeyDale · #3 08-19-2014, 06:41 PM

I set mine 3/16 high and now I'm kinda worried because I'm reading that some didn't sag much. May be better to set it perfect and shim the engine up if it sags. But, almost all the RV's I saw at Airventure was sagging some.

crabandy · #4 08-19-2014, 10:00 PM

I believe it depends on engine/prop/acro combo. I built my cowling 1/8 inch high to my spinner, after 65+hours it seems to have dropped 1/8 inch with The Lord mounts/o-360/Catto prop/acro.

edsong · #5 08-20-2014, 06:02 AM

Where is the best place to shim. Firewall or Engine?

MikeyDale · #6 08-20-2014, 07:01 AM

I believe the best place to shim is the engine.

ChiefPilot · #7 08-20-2014, 07:08 AM

I lined mine up exactly, and after 22 months/310 hours, it doesn't appear to have moved *at all*. Lots of acro/rat racing, with up to +4.5G on a regular basis.

I think one difference might be that the engine hung on the mount for almost two years before I fit the cowl. I wonder if any sag that would have happened took place over that time.

lr172 · #8 08-20-2014, 07:33 AM

Quote:

Originally Posted by ChiefPilot

I think one difference might be that the engine hung on the mount for almost two years before I fit the cowl. I wonder if any sag that would have happened took place over that time.

I am guessing that the compression is a matter of time and weight. I suspect vibration can accelerate the compression, but time and weight are the key factors. This may explain why some don't report a dropping nose; It happened before mounting the cowl

Larry

Rupester · #9 08-20-2014, 09:17 PM

On the advice of others, I set mine 1/4" high to allow for sag. That was 4 yrs ago, and it's still nearly as high as the day I set it. I used the standard Lord mounts from Vans ... have had almost no sag.
One variable I never considered 4 yrs ago is the type of prop. I think my no-sag installation is partially due to the negligible weight of my Catto prop. I suspect a metal Sensenich would have sagged more.

crabandy · #10 08-20-2014, 10:47 PM

Rv7 O-360 with Catto prop with Lord mounts, I built the cowl to spinner interface 1/8 inch high. After 65ish hours and a decent bit of aero it has moved perfectly inline ( I noticed a little movement after the first several engine runs and the rest after the G testing). Perhaps it will move more after some more time, it's going to have to take a lot of looking to find 1/8 inch difference.....it's going to take more than an 1/8 for me to shim anything.