Rubber engine mount reversal

[jeff beckley]

On my RV7A when we mounted the engine I thought we payed close attention as to which mounts go where. Soft verses Hard. We then proceeded to install the engine cowl allowing for 1/8" sag. We did notice that there was a slight difference in the gap between the top of the spinner and the bottom in relation to the cowl. 1/8" wider at the bottom. I planed on laying up some filler on the cowl to even this out before I painted.
The other day I made a comment to an experienced builder about the gap and he suggested that I may have reversed the mounts. Says I should go check them. Well to my surprise I did in fact have them reversed.
Now what to do?
If I go in and switch them around will my position change in relation to the prop?
I now have the soft mounts behind the cup at the top and the hard in front against the engine.
If I do nothing at all will that cause a problem? Additional sag latter on?
It seems that the geometry will change if the mounts are of difference thickness. If so, can a couple of washers strategically placed bring the center line of the prop back? I cant reposition the cowl as it is installed.
Is the thrust angle up or down changed if the mounts are wrong?

[dan]

Fiberglass is cheap. Do it right.

[jeff beckley]

No question as to if we are going to do it right. I want to know if the alignment of the engine will change if we were to change the mounts around. I cant see a hole new cowl assembly would be that cheep and adding the countless time fitting and modifications that were done around the inlets and the custom fitted front leg fairings. All that would have to be redone if the front of the cowl had to be lowered. I don't mind if I have to just back fill behind the spinner. Thats easy and cheep!

[dan]

First get the biscuits in there the correct way, and then see how the alignment is. I suspect the alignment will be off a fair amount.

No need to buy a new cowl. I'd just see where you stand and then "patch" (not the right word, but you get my drift) the aft cowl edges to get it all lined up right.

[Mel]

Dan is right,
Get the mounts correct first. Then work on the cowling. With the mounts reversed, your engine will definitely sag more and more.