Spinner/rear bulkhead flushness

[Paul Eastham]

Hi,
I've got a simple spinner question for you guys. I am currently trying to position the cowl for the proper gap between cowl and spinner.

My fiberglass spinner is slightly larger than the spinner rear bulkhead, leading to an extra 1/8-1/16" flange of fiberglass that extends aft past the rear bulkhead. The plans don't show any flange, but don't mention trimming it off either. (these are all stock Van's parts, for a fixed-pitch prop, 9A)

Are you guys trimming the two to match up perfectly? This will affect the size of the cowl-spinner gap, of course.

Thanks,
Paul

[RV_7A]

Paul,

Absolutely do not trim this surface. It is the onlt true reference on the aft end of the spinner. 1/8" overhang is perfect and as long as its unifrom all the way around, it will spin true.

See my page ...

http://www.jeffsrv-7a.com/PROPS/06-06-17.htm

-Jeff

[rvbuilder2002]

Originally Posted by RV_7A

Paul,

Absolutely do not trim this surface.
-Jeff

I totally disagree. It is not supplied in a final size and there is nothing difficult about trimming it and finishing it to a true/straight edge. 80 grit sandpaper glued to a 12" long sanding block wil do it in minutes

Install the cowl using the back plate as a reference. Then install the spinner (without the cowl in place).

Use the edge of the spinner backplate flange to mark a line around the inside of the spinner and trim to the line.

A side note... it is important that the spinner be installed with it fitting tight to the back plate. Otherwise you will be sucking it tight to the back plate with the screws. This will cause puckers in the spinner between the screws. This will just get worse with time.
Typically the front bulkhead holds the spinner a little to far fwd to allow it to fit the rear bulkhead tightly (primarily on a C.S. prop.) This can be corrected by grabbing the already mounted front bulkhead with your hands and pushing it aft slightly (grab at 3 & 9 Oclock and then 12 & 6 Oclock).
The bulkhead is made of soft aluminum and can be moved quite easily on a constant speed prop because it is supported by a small area on the prop hub dome so go easy and recheck the spinner fit often while you adjust.

[RV_7A]

Paul-
I was looking over your site (nice site!) and saw your fire sleeve you were going to tie off on your gascolator. Well I saw them doing this on Rockets and thought I would share it. I liked it OK...

-Jeff

[Paul Eastham]

Thanks Jeff,
I came across the idea of safetywiring firesleeve in Nuckolls' FWF book last night, but he was just using a single loop. This looks much sturdier.

(BTW for other readers, I purchased the proper firesleeve clamps as well, but could not figure out how to tighten them without damaging the soft aluminum tubing I have underneath)

Paul

[rvbuilder2002]

As a final detail it is good to seal the end of the fire sleave with a filet of high temp RTV so that it can not soak up any oil, etc. It gives it a more finished look and prevents any danger of burning at the ends in a fire because of any soaked up oil.
Even better is to use the liquid dip that you can buy but the RTV works just as well.

[RV_7A]

Yeah good idea. I can see how that would act like a wick and burn easily.

-Jeff