R

roee

Well Known Member
My question pertains NOT to the gap between the aft edge of the spinner to the forward edge of the cowling. Rather it pertains to the gap on the inside between the conical part of the spinner backplate and the corresponding conical flange of the cowling. I'm wondering how wide does that gap need to be in order to prevent possible contact with up/down/side-to-side tilting of the engine due to its own vibration and/or flight loads?

How much does the engine move around up/down/side-to-side at the spinner?

I appreciate any informed opinions. And would especially like to hear the relevant experience of others with a WW prop (I understand Hartzell and others don't have a conically shaped spinner backplate like WW).

Thanks,
-Roee

20111107_16_annotated.jpg
 
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It's tight

I have a rv7 with an IO360 smooth bottom cowl, and I went through several iterations to relieve cowling area on the lower half for clearance. It is tight. I did layups on the underside, and sanded off material on the inside a bit at a time until I stopped seeing evidence of rubbing. After I was finished, I thought of this: glue some 100 grit to the rear spinner plate, run the engine awhile. Remove cowling...
Ymmv,
 
Ben,

How much clearance did you end up with when it was no longer rubbing?

Thanks,
-Roee
 
I've read your question about 10 times and I still can't visualize what problem your having. I made my cowling so that it is about 3/16" behind my WW200RV spinner, with the diameters approximately matching. No part of my cowl projects into the conical bowl of the spinner backplate. Is this what you are doing?
 
Bolts rubbing

I put a WW200 on my already flying plane. They were great in working with me to adjust the cowl/spinner distancees. They had to move the backing plate forward and made some adjustments so it was about 3/16 in farther forward to clear my cowl.

I did have to trim the bolts that hold the backing plate halves together because they rubbed on the inside of the cowl lip where your red arrows are. In my installation I have bolts that actually go in the gap where your red arrows are..

I fly pretty agressively routinely pulling 4 g's and the engine moves enough that I had marks on the inside of my cowl until I shortened the bolts.
 
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Ahh. The photo clarifies it.

I just got lucky. I didn't sweat that gap and have no rubbing. I'll see what the gap is next time I have the cowl off.

Guy
 
If anyone has some more pics of their WW200RV installation I would like to see them. Especially this critical area around the conical cowl area.
I am considering a WW200RV installation on my 7 and was wondering about the cowl clearance.
 
I have an RV 200 on my 6. Never measured that distance so can't tell you what it is.

I did have some very minor rubbing there after 250 hrs where the screws on the spinner back plate joining tabs touched the cowl at some point.

I would say it is not a big worry.
 
depends on how much you pull...

If your not rubbing your are not pulling hard enough!

Your gap looks a bit tight though... I could not find a photo as a comparison but will take one when I have a chance.

The engine moves around an amazing amount when you load up the G... as my engine settled in and the rubber mounts have been fully stressed I have slowly increased the kiss wear at this point. Recently I shimmed the lower engine mount points to the fuselage out .020 to regain clearance under high G. I have refinished the wear on the cowling and will test this weekend.

One of my aerobatic buddies who is also an RV guru suggested just lopping the offending section of fiberglass... I might but chose to initially make a minor adjustment with the engine mount.

Here is a shot of the mount shim
img3430l.jpg


The resulting spinner / cowling position (spinner now a smidgen higher than cowl)
img3421f.jpg


A shot of touching up the wear from the interference (all sanded smooth now)
img3436ii.jpg
 
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I have an IO360 and WW200. I had the same rub problem and initially futzed around with sanding and grinding. I was a bit puzzled at how much movement there was - I didn't think about g loading.
Eventually I added washers to the lower engine mount- the hard way.
I hadn't thought of cutting out the side of the washers to make it possible to slip them in without removing the bolts.
My spinner now sits slightly high but in no longer rubs.
 
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