MT 15" spinner clearance

Previously I measured and posted the distances from the spinner to the crank flange for the MT-12-B. The issue with the previous post was that I had assumed that the MT-12-B came with a 15" spinner to fit my showplanes cowl. Once I started to fit things I noticed that the diameters did not add up and the mistake was that the "default" when you order a 12-B prop is that it comes with a P-469-1 spinner. The correct part number for the 15" spinner is P-285-1-A. Also, because I special ordered mine as Matte Black, this is a no-stock item. :(

The difference is significant!


The new clearance measurement are inline with the trusty internet posts.
 

I have my starter ring gear off for the cowl fit/installation and I also took the spinner to cowl gap out of the mockup plate distance rather than putting spacers on the cowl. For my records here is my horrible hand writing tracking the crank flange to spinner distance. I may increase this gap to more than 1/8" but for now here is my mockup target number:

MTV-12-B Spinner

I was making a spinner template last night so that I could start fitting my cowling. I didn't really think about it last night, but as I was laying out the board I had an issue with fitment. (don't mind the non-concentric circles, in the quasi-center of those dots are the real layout points)

The issue I had is that I started with the outer circle (15").

Thinking that I was just mis-remembering the spinner diameter I grabbed the spinner and laid out another line.

That went fine and everything bolted right up to where it should have been. But something still did not feel right. I went over to the show planes website and low and behold, the cowling is designed for a 15" spinner. So that is a bummer. I am not sure where the mix up was, but I think it all started with me assuming that all MTV-12-B spinners were 15".

I guess I have my first parts mix-up.

MTV-12-B Dimensions

One of the weekend tasks is creating a jig for the cowl fit up to take the place of the prop and spinner. I read a while back on the reliable internet that the distance between the spinner plate and the hub flange was 40mm. I did not want fit my cowling based on some internet numbers so I waited for my prop to arrive so I could take the measurements myself.

The first measurement I made was to the aft spinner cap. This looked to be 1.9". At this point I was completely assuming that the spinner itself was going to end flush with the aft plate.


Going to the manual, you will see that this is not a good assumption. When you fit the spinner onto the assembly you see that the spinner extends beyond the aft plate. With the spinner installed, there is ~1.55" between the aft most part of the hub flange and the spinner. I would really like all these numbers to add up, but having triple checked my setup, 1.54" (39mm) is the number.