Cowl to spinner fit due to engine sag?

[az_gila]

Originally Posted by swisseagle

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Would be interesting to know what Piper or Cessna do on there planes.

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They call up a Lord washer in their parts manual, and define the quantity needed with an "AS REQUIRED" note.

http://www.aeroinstock.com/products/...ail/index.html

[Geico266]

Somewhere I read a 1/16" washer will raise the aft end of the spinner 1/8". That measurement seems to be very accurate. Thanks to who ever figured that out, you saved me a ton of guess worth. Took care of 3/8" engine sag (after 300 hours) with 3 each of a 1/16" think x 2" washer this afternoon. Don't forget, you will need longer bolts. AN7-46 is what I ended up with using 3/16" thick of 2" spaces.

[Tom Martin]

Not all engines sag with time. Most of the ones I have dealt with have not. It is easy to slide a washer under the lower mounts if required.
Every one seems to worry about how the spinner and cowling line up on the ground. I am more concerned with how they line up in flight. I want a smooth line, in flight between the cowling and the spinner.
On the ground the engine is hanging from the motor mount. In the air the engine is pulling the airplane, thus the spinner goes UP in flight, I have noted 1/4" on one of my rockets. Thus if your engine does happen to be a bit low you can say that you planned it that way!

[jimbo]

Assuming you do want to shim the engine up to match the spinner with the cowl is it acceptable to cut a U in the washer to slip the washer in place without having to pull the bolts? It seems to me that what could slide in could also slide out given heat and vibration.

Don't like the idea of having to pull out the bolts to put in uncut washers but definitely want to be on the safe side.

Jim
RV9a flying

[GeneL]

Congrats Tom, someone that finally gets it!!

[lr172]

Originally Posted by Loman

Somehow my cowl turned out a little high. Either that or the 0-320 engine with Cato 3 blade prop already sagged 3/16 or so since it was mounted six months ago on Lords mounts supplied by Vans.

At only 3/16, I could have left it but any (further) sag will make it worse so I set about leveling it.

I tried some washers similar to the ones that came with the Lord mounts but not quite as thick. However, now the spinner was too high.

Being a Sunday, I had to work with what I had on hands and I found that a scrap of 063 aluminum give me a perfect result.

Question is: can I make permanent shims out of aluminum? Presumably they have to be steel.

It is not structural or at least not performing any holding force, so aluminum is fine for a shim. At least I would be comfortable with an aluminum shim there.

Larry

[kyle Lee]

Hi all. Does anybody have any experience or thoughts regarding sag with the RV-12, standard mounts from VANS, standard Rotax 912ULS? My issue is that the engine/spinner is high by about 3/16" on the ground. Everything else looks good with a nice 3/16" gap between the spinner and cowling. Personally, I am hoping for a bit of sag but am concerned after reading Tom's comments. Any thoughts would be appreciated.

Kyle

[lrdrvr]

Originally Posted by jimbo

Assuming you do want to shim the engine up to match the spinner with the cowl is it acceptable to cut a U in the washer to slip the washer in place without having to pull the bolts? It seems to me that what could slide in could also slide out given heat and vibration.

Don't like the idea of having to pull out the bolts to put in uncut washers but definitely want to be on the safe side.

Jim
RV9a flying

I'm curious about this as well...

Anybody?

[jetjok]

Cutting the washer to allow installation without pulling the bolt is a great time saver. But, (IMHO) a really bad idea. There is no way that one could expect the engine not to move reducing the pressure holding the washer. I am sure that there will be replies stating how many hours of inverted flight at 9G's they have with the slotted washers. But, as I said it is only my humble opinion...and not my plane!
It is not that hard of a job to level the plane as needed, and rig your engine hoist to provide the necessary lifting geometry. As has already been stated, chances are you are going to need longer bolts anyway!

[MikeyDale]

I fitted the cowl low with anticipation of the engine sagging but I later wanted the cowl and spinner level just because it looks right. After researching on this forum, I made slotted aluminum washers out of various thicknesses and simply loosened the two top engine mount bolts between the engine mount and firewall. Slipped the washer between the mount and firewall and after a couple of tries, found the right thickness. In about an hour, I had my spinner perfect and the nuts torqued back up and cotter pins installed! I have 50 hours on the plane now and when the engine sags a little, I will just replace the slotted washer with a thinner one or remove it. I have checked the washers and they haven't moved at all and I'm confident they will not with all the torque on the bolts.