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Eric Page
05-25-2021, 03:59 PM
I'm zeroing in on an engine and propeller order, but I'm getting what I consider an unusual recommendation from the propeller vendor. He's telling me that most of the Kitfox builders he sells props to use a 250mm diameter spinner, and that he doesn't recommend anything larger than 260mm.

Thanks to AlexM's use of a round engine, I now have his Series 7 Rotax smooth cowl, which I plan to put over a 912iS. When I measure that cowling, the circle described by the upper forward curve of the top cowling is 280mm (11") in diameter (see photo, below). It seems logical to me that the spinner should match that diameter so that there isn't any flat surface uncovered around the circumference of the spinner, and the spinner leads air directly into the two intakes.

So, my question is this: what diameter spinners are y'all using on the Series 7 Rotax smooth cowl? Any photos of installed props that show the spinner-to-cowling interface would be especially helpful, whether they're identical in diameter or not.

Thanks!

28085

efwd
05-25-2021, 04:34 PM
For both 75" and 70" props, Kitfox sells 11.3" diameter spinners. It doesn't appear they have any other option.
You can see my plane on my post #1092. I would not recommend making the gap as little as I did. It works just fine but when trying to install the lower engine cowl I could use even just 1/2 inch gap. Im closer than that. Looks good to me though. I have hangar rash on the lower cowl from where my prop scrapes it as I bring the cowl up into place.

Maverick
05-25-2021, 07:01 PM
I have the same issue as Eddie with the lower cowling fit. Every time I take it off and put it back on, I scratch a little bit more. In fact, I spent the weekend doing touch-up on the cowling because of it. A nice tight fit is great for cooling and aesthetics but it's a pain when it comes to maintenance. I have to talk my wife into helping me put it on. That's not always convenient. :rolleyes: I bought my spinner from Murle Williams. I believe that it is 11.5" but it might be the same size that Kitfox sells.

Eric Page
05-25-2021, 07:37 PM
Thanks, guys. I had a feeling the spinners weren't as small as 9.8" (250mm).



You can see my plane on my post #1092.
Which part of the forum is that in, Eddie? I don't see a build thread with your name on it...

efwd
05-25-2021, 09:00 PM
clik on my EFWD above my Pic. over on the left. Then Clik "view forum posts".

Eric Page
05-26-2021, 12:54 PM
Hmmm, doing that brings up a search result with only 500 posts out of your 2k+, and none of them are numbered so finding #1092 is impossible. But, it did get me to your "EFWD Build" thread, where I found #1092 on page 28, and that had a good photo of your plane. Thank you!

I found a few other pictures as well and it looks to me, at least anecdotally, that most builders use spinners that match the diameter of the upper curve of the cowling...

jiott
05-26-2021, 07:10 PM
Yes Erik, the 11+" spinner is perfect for the SS7 smooth cowl. It matches the outer curve just like you would want it to.

efwd
05-26-2021, 08:51 PM
sorry Eric, I see what ya mean. That isn't what happened from the page I was at then. Anyhow, Glad you found it.