Pre-fitting RV-7 Cowling

I?m planning to fit / finish the cowling on my RV-7 project ahead of the acquisition of the engine & prop. I have a lead on a loaner "tooling engine" as I'm currently saving $$$$$$s for the IO-360-M1B and Hartzell CS Prop (part number from vans catalog --> Compact hub Constant-speed prop for (I)O-360 (180/200hp) 72" PROP C2YR-1BFP/F74972).

There is already some great info in this thread: http://www.vansairforce.com/community/showthread.php?t=77035

I have a couple of specific questions :
- Does anyone know the dimensions of the prop hub (i.e. thickness from the forward face of the starter ring gear to the back of the spinner) for this prop? I need this to make up the appropriate spacers to hold the spinner in place. (note: I checked with flyboy accessories. They rent a tool for this purpose, but it is unavailable and I guess I would still need the dimension...)
- IF I end up going with an FP prop, is there any prop (wood or metal) that cannot be re-positioned with the appropriate spacer ?

General question:
- To those who have done this before, any gotchas you can share would be appreciated.

Thanks in advance!

You can obtain specific drawings from Hartzell as to prop/hub dimensions. I had to do this with my MT prop due to a lengthy lead time. I used the Flyboys alignment tool and when the prop did arrive it was a perfect fit.

- Josh

I have the same propeller and am currently fitting my cowling.

From the face of the ring gear to the back of the spinner / rear mounting plate I get 1-11/16".

The rear spinner plate is mounted with only the spacers included with the prop (no extra washers).

Hopefully others will provide dimensions as well so you will be able to compare.

No extra washers? There is a call for an additional standard washer when using the Hartzell prop unless something has changed is in the plans? The extra washer gives proper distance between the prop and rear bulkhead when fully cycled.

efitzgerald said:

The rear spinner plate is mounted with only the spacers included with the prop (no extra washers).

Click to expand...

Larco said:

No extra washers? There is a call for an additional standard washer when using the Hartzell prop unless something has changed is in the plans? The extra washer gives proper distance between the prop and rear bulkhead when fully cycled.

Click to expand...

Larry is correct.

If you do a clearance check with blades rotated to full course pitch I think you will find that the blades contact the spinner aft bulkhead.

I am using a Cummins Aluminum spinner. Some people have had problems with the front plate not allowing the spinner to line up with the rear plate.

I checked the gap between the rear plate and there was plenty of clearance at full course pitch. I was going to modify the front plate if needed.

I mentioned the lack of washers so the OP wasn't getting bad information. I would still suggest getting more feedback on the measurement requested.

The Mothership has some notes here (found this as I?m getting close to doing the same):

https://www.vansaircraft.com/simulating-propeller-for-fitting-the-cowl/

That link mentions a 2.125 spacer with the ring gear/?flywheel? installed, for constant-speed props.

It would be nice to have a definitive number; I could hang my prop temporarily but I?d rather just leave it in the box right now...

I used 2 7/16" spacer tubes between the prop flange and the back of the spinner bulkhead when I fit my cowl before I had the M1B engine.

This ultimately gave me about 3/16" between the finished cowl and the back of the Vans spinner for the Hartzell blended airfoil constant speed prop.

If I ever go through this process again I'll be using 2 1/2" spacers to make it easier to remove and install the cowl

Thanks for the great info.

The info here is applicable to models other than the 7-----so I have moved it to "RV Building Tips/Techniques" for easier finding in the future.

Great info, and pretty good timing for our S-21 project, as the same techniques will apply to it, and other kit planes as well.

Thanks

Folks - thanks for taking the time to share your experiences and pictures. I will reach out to Hartzell for the hub drawings and puzzle over the info you all shared and move forward with my plans.

Follow-up

I have a follow-up question and figured I’d learn how to post some pictures too - might help someone in the future.

I borrowed an O-320 from a local engine shop and was able to scrounge an unairworthy Hartzell compact hub for this mock-up / cowl fitting exercise.




The prop flange on this borrowed O-320 is 0.280” thick. The engine shop person said an O-360 should have a prop flange thickness of 0.440”. Question – can someone with an O-360-M1B confirm this 0.440” prop flange thickness dimension?

I’ve made up the appropriate thickness spacer using washers and scraps left over from the spinner bulkhead to build up the ‘skinny’ flange (0.280”) up to what I think is full thickness (0.440”).



Also, on the prop hub / spinner assembly I’m simulating the ¼” thick spacer called out on drawing C4 with hardware store nuts that happens to be exactly ¼” thick and added the AN960-416 extra washers shown on the drawing and mentioned by one of the previous posters. This should get me a true full blown mock-up with all thicknesses correct. Anybody see any flaw in this plan?







Someday, when the real engine arrives, it should be a simple bolt-on exercise.




Thanks Again,
Josh

kovacjd said:

The prop flange on this borrowed O-320 is 0.280? thick. The engine shop person said an O-360 should have a prop flange thickness of 0.440?.

I?ve made up the appropriate thickness spacer using washers and scraps left over from the spinner bulkhead to build up the ?skinny? flange (0.280?) up to what I think is full thickness (0.440?).


Thanks Again,
Josh

Click to expand...

Have you confirmed the extra 0.160" is forward of the prop flange face?

Valid point.

The back of the prop flange has a nice radius onto the crankshaft.

The front of the prop flange is ground flat, except for the extension which plugs into the prop hub.

I had a bunch of pics showing the various stages of the assembly (using Flickr)...they didn't make it onto the post. :-(

Trying again with the pictures from Flickr:

Try #3 for pictures

RE-POSTING WITH PICTURES WORKING.....

I have a follow-up question and figured I?d learn how to post some pictures too - might help someone in the future.

I borrowed an O-320 from a local engine shop and was able to scrounge an unairworthy Hartzell compact hub for this mock-up / cowl fitting exercise.




The prop flange on this borrowed O-320 is 0.280? thick. The engine shop person said an O-360 should have a prop flange thickness of 0.440?. Question ? can someone with an O-360-M1B confirm this 0.440? prop flange thickness dimension?

I?ve made up the appropriate thickness spacer using washers and scraps left over from the spinner bulkhead to build up the ?skinny? flange (0.280?) up to what I think is full thickness (0.440?).



Also, on the prop hub / spinner assembly I?m simulating the ?? thick spacer called out on drawing C4 with hardware store nuts that happens to be exactly ?? thick and added the AN960-416 extra washers shown on the drawing and mentioned by one of the previous posters. This should get me a true full blown mock-up with all thicknesses correct. Anybody see any flaw in this plan?







Someday, when the real engine arrives, it should be a simple bolt-on exercise.

Consider dropping the top cowl down 1/4? or so. The engine will only sag, so starting with the top of the cowl in about a straight line with the top of the spinner mitigates that sag.

Carl

^^^^^This

I used a junk engine case for fitting my cowl and wish I would have figured in more engine sag.