vbpiper

vbpiper

Well Known Member
I am building a -7A, Lyc O-360/Sensenich FP. Any problems with installing the prop prior to fitting the cowl and baffles? I would prefer not to monkey with the spacers if possible. A search of the archives did not turn up a clear answer.
Thanks in advance.
 
Monkey with the spacers. The prop itself adds nothing except being a big clunky obstacle. You will be pulling cowlings on and off for fit-up more times than in your first 1,000 hours of flight.

John Siebold
Boise, ID
 
Don't install the prop till all the engine work and cowlings are completed. It will just get in your way. It will also make putting the cowl on and off a royal pain.
 
I installed the spacer and put the prop back plate in place then lined up the cowl to that. Worked great.



I just wish I had allowed for more engine sag than I did. Who said these conical mounts don't sag?
 
fitting cowl-with or without prop?

Buy 4 hardware bolts(fine thread) 3" long x(7/16 ?)dia and cut 4 pcs pvc pipe( 1/2") for spacers (probably 2.25") same as prop spacer. Install spinner back plate with spacers behind, and fit cowling to that. Much easier than dealing with prop in place.
 
Thanks

Sounds unanimous. Spacers it is. Hardly the time to start cutting corners now.Thanks to all.
 
Spacers?

Ward,
Sorry for the ignorant question but... what spacers? I'm getting ready to install my engine and don't see any reference to spacers.
 
I think he's talking about the temporary spacers that you can make to simulate the thickness of the prop. These can be something as simple as a short lengths of PVC.
 
Spacers

Brian,
The spacers are cut equal to the thickness of the prop spacer (2 1/4" in my case) to position the rear spinner bulkhead to aid in placement of the cowl. Lengths of 1/2 inch PVC that fit between the ring gear and the rear spinner bulkhead. I used 1/2" hardware store bolts to temporarily affix the bulkhead, as Vance suggested.
I went ahead and made them tonight. Easy.
 
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On the Van's website in the "construction FAQ's. The there is a download titled "Simulating the propeller for fitting the cowl". This construction FAQ details the PVC spacers. Here is the Link

http://www.vansaircraft.com/public/confaq.htm

I used this method on a RV6. I have the newer cowling and Hartzell BA prop and made the PVC spacers 2 3/16 to allow for the spacer and washer installed between the prop hub and spinner backplate. Note: The construction FAQ has been updated since I originally used it. Also, I set the top of the cowl 1/8 inch higher than the spinner backplate on the assumption that the engine will sag based on comments from other builders but I am not flying yet so I can't confirm if it was necessary or not (it is probably dependent on the manufacturer/type engine mount rubber bushings are used).

your mileage may vary
 
I see many replies from the "spacer" crowd. However, most builders that I know, including myself had the prop in place to install the cowl. I didn't find it to be a problem.

L.Adamson
 
Thanks, L. Adamson

I guess the reason I asked the question in the first place was that I had read of some instances in which the cowl/bulkhead space changed when the PVC spacers were removed and the prop spacer installed. I thought it would be easier to just have the prop installed in the first place.
Thanks for the input!
 
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Okay, now that L. Adamson has said it, I will keep him company - I used the real thing as well. Me no trust no stinkin' spacers. Plus, I just liked looking at my prop on the engine. I really didnt find my 2-blade to be in the way, but I suppose it would be a little worse with a 3-blade.

erich
 
pvc spacers worked for me

I'm not flying yet, but have O-360, FP Sensenich setup and did the cowl fitting with the spacer installed and pvc piping to take up the prop hub space:

RV-6A(N731CK)093.JPG


I need to do some work to smooth the transition where the top & bottom cowlings meet at the front outboard areas, but the cowling to backplate spacing looks ok.

Other pictures of my cowl fitting process are at:

http://www.ckhand.com/RV6Aproject/FirewallForward/Cowling/cowling_pg_1.htm


Chris Hand
RV-6A, finishing.....
 
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Doing mine now, with the prop. The prop doesn't interfere with the cowling 1 iota. The difficulty and interference comes from the spinner backplate, which you will still experience with the spacer method. Plus the prop gives me something to steady myself with as I repeatedly install and remove the bottom cowl. YRMV.

Jekyll
 
Jekyll said:
.......The prop doesn't interfere with the cowling 1 iota........Jekyll
Click to expand...
I totally agree. Just prior to working on the cowls, I installed the spacers. I just did not feel comfortable with those spacers knowing from experience how minute differences on one end can magnify seemingly small errors by the time you get around to the other end. So I removed the spacers and installed the (constant speed) prop for TRUE reference prior to trimming the cowls. The blades are positioned horizontally 99% of the time anyway and is no big deal to work around. Even Van's recommends using the prop if you have one. The cowling fits so well that NO uneven gap exists.... most particularly the gap behind the backplate and cowl that might otherwise require filling and sanding etc. to account for engine offset.

Not only that but having the prop installed made it just that much easier to intentionally locate and trim the cowling to account for potential engine sag later.

 
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might have different ans for FP vs CS

If I was going with a constant speed prop then I agree, I'd put the prop on to fit the cowl. But for the FP setup I think installing the prop extension and the spinner backplate, then using the PVC spacers just to allow using the prop bolts to secure the extension and backplate should produce the same results as having the prop installed even if the PVC spacers are off slightly.

If the PVC spacer lengths are off slightly, it shouldn't make a difference in the final fit for a FP setup since they are forward of the spinner backplate. I don't think that's true for the CS setup (although I'm not putting a CS on so I'm not real sure of the exact setup, just assuming from the posted picture that the prop hub is installed in the CS installation where the extension piece installs in the FP setup??).

I don't know how much the prop would or would not have increased the hassle of the multiple remove/install cowling steps for me, but I was also considering the fact that my garage/shop doubles as a high traffic area for kid's bikes, storage area, freezer access, etc so was trying to avoid possibility of inadvertent "garage rash" damage to the prop.

Chris
RV-6A
 
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I use spacers and a piece of plywood to simulate the rear spinner plate. The reason for the plywood disk is so that I can cleco the cowling to the plywood for perfect spacing and the right height. It hold the cowling in place while measuring the cowling for trimming. With the plywood disk the same diameter as the back plate it makes it easy to adjust the height as well of the cowling. Seems to work well without any hassles for me.
 
prop spacer

A spacer is a spacer. The only important thing is that the distance is correct. I would rather have my prop(especially if CS) out of harms way. The spacer, whether pvc pipe, wood, or your prop spacer, just needs to be the same length. :)
 
spacers didn't work for me!

I did the spacer trick. It was great until I got the prop. With the actual prop on the space between the cowl and the spinner backing plate disappeared! I talked to Van's about this and they didn't seem surprised. There solution was to fill in some of the nose of the cowl with epoxy flox mixture then sand the cowl back until I had the required clearance plus 1 washer under the motor mounts at the firewall to push the engine out. My setup before the prop was beautiful, now it is just okay. The lines are definately not as good as before. If I was doing it again I would have the prop on for the initial fitting then remove it for the next thousand times you will take the cowl on and off.
 
To add to my previous post, I have a Hartzell. Don't know about FP prop method.

I thought about using the spacer method but I had too many occurances of measure twice, cut once then get more materiel and repeat. I had real angst about encountering just the situation Andrew found himself in and ruining a good (and expensive) cowling or being faced with significant surgery to make adjustments. As it is, I've spent the last 4 days flocking the front of my cowlings to close the space behind the spiner due to irregularities of my cowlings. I did find another good reason for hanging the prop now, I've been able to complete the spinner assembly during the glass work stage. Glass a bit, spin a bit, sand a bit etc. If I had used a spacer, my spinner would still be a sub-kit, not a spinner. (what a nightmare trying to find the equidistant spacing of the 6 screws on the front plate, is it "2 pi r" or "pi r squared"?:D). My wife will ask someday about the epoxy on her cloth tape measure.:eek:

Jekyll
 
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Adjustment for cowl sag

James_RV60436

I am just about to install my top cowl and was reading your post on cowl installation and noted that you said you positioned the cowl 1/8 inch above the spinner to accommodate future engine sag. ..."....I set the top of the cowl 1/8 inch higher than the spinner backplate ..."

To plan for engine sag I think you need to install the cowl below the spinner, not above. The cowl is fixed and will not move once installed. If the engine sags, the spinner will move downward while the cowl remains fixed. Hopefully they will align.

Mike Draper
RV-8
N468RV
Finish
Bridgewater, MA
 
Jekyll said:
........ I thought about using the spacer method but I had too many occurances of measure twice......what a nightmare trying to find the equidistant spacing of the 6 screws on the front plate, is it "2 pi r" or "pi r squared Jekyll
Click to expand...
Yea, I agree. Sure, a spacer is a spacer but cutting each to the precise length......therein lies the rub.

To prevent future nightmares.....finding equal spaces on anything round (like the spinner screw spacing) is a very easy problem to solve.....almost a no brainer really......especially for the mathmatically challenged like me. :)

http://www.vansairforce.com/community/showthread.php?t=16846
 
Rick:

Thought of that but the spinner is a cone shape which means the paper will be curved. I calculated the perimeter at the front plate to validate the cloth tape distance, did the division and tweaked the results to make it fit.

In retrospect, a string layed abroung the spinner at the plate might have been easier.

Jekyll
 
Depends on the spinner

drill_and_buck said:
James_RV60436

I am just about to install my top cowl and was reading your post on cowl installation and noted that you said you positioned the cowl 1/8 inch above the spinner to accommodate future engine sag. ..."....I set the top of the cowl 1/8 inch higher than the spinner backplate ..."

To plan for engine sag I think you need to install the cowl below the spinner, not above. The cowl is fixed and will not move once installed. If the engine sags, the spinner will move downward while the cowl remains fixed. Hopefully they will align.

Mike Draper
RV-8
N468RV
Finish
Bridgewater, MA
Click to expand...

What you are trying to achieve is a pleasing transition from your spinner to your cowling as well as equal spacing between back of spinner to the cowling, with adequate space to get the cowl off. There is no fixed measurement due to cowling variances.
I set mine exactly even with the top of the cowling, when it fully sagged, the lines from the spinner profile to the top of the cowling met up perfectly, even though the spinner is actually a bit below the top of the cowling, it is also 3/16th" in front. If it was lined up with the top of the cowling, it would not have the same "smooth" transition of that arc.
Frankly, I have never walked the line and seen one that looked so bad it was obvious to me, so as long as you anticipate the sag, and "eye ball it" when you position the cowling, it will probably come out just fine.
 
The easiest way to find the proper distance between the screws is to take a piece of masking tape. Wrap it around the cone where the backing plates are mark a line where the tape end meets the other end. Remove the tape and divide it into equal spaces according to the number of screws you are going to use. Re-install the tape and drill the holes on the markings allowing for proper edge distance. Couldn't be easier in my opinion.
 
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