Spacing--Spinner backplate too cowl??
 

On my 80" Extra, I have 1/8" spacing between the spinner backplate and the fiberglass cowl.

Is this okay?--or does it need to be more-- or less??

I'm not usually the kind of person who builds a beautiful scale model-- but this one is nice and I don't want it to look out of place. I have minimal--(actually; NONE)--experience with spinners and glass cowls. :confused: :eek:

Thanks

Spacing--Spinner backplate too cowl??
 

I have seen plans call for 1/8" to 3/8".

In my opinion, 3/8 is too much for just about anything. What you want is enough clearance so that as the cowl vibrates/bounces around, it doesn't hit the spinner. This clearance is really determined by the mounting system for the cowl. If the cowl is mounted such that it moves quite a bit, then you need more clearance.

Spacing--Spinner backplate too cowl??
 

What is the negative effect of too much clearance?

Spacing--Spinner backplate too cowl??
 

I'm not aware of any negative effect except that it make look odd.

Cowl mounting
 

My cowl is mounted internally. I glassed a 1/4" plywood ring inside the cowl and installed 10-24 blind nuts. I drilled holes in F-2 former and mounted with nylon bolts. The cowl overlaps the fuselage by about 3/4".

I'm using a 3.5" spinner. I cut a 3" hole in the cowl where the prop hub exits. So, I have about 1/4" undersized hole all around behind the spinner.

I don't know how much my engine will shake on the plane yet. I just got some aluminum standoffs for it and installed tonight. I would think that with such a sturdy and flex-free mount that the whole plane will shake uniformly-- not just the cowl by itself. We'll see how it does when I run the engine for testing purposes.

Hopefully my 1/8" gap will work out. Thanks for the help.

Spacing--Spinner backplate too cowl??
 

i have the same problem. my cowl is a bit out of shape, and i have a bit of spacing between spinner and cowl. in order to get the front of the cowl lined up with the spinner, the cowl points a bit to the left, so on one side of the spinner i have 1/4 clearance and on the other side i have 1/8. the cowl is centered on the plane. how can i fix this?