Hartzell Composite Prop Spinner backplate

I purchased a Hartzell composite prop (G2YR/N7605W-2X) from Vans and while it is a thing of great beauty, the blade chord is very wide and I'm a little concerned about it interfering with the cowling when the pitch is coarsened up. It does have the extended G hub and while I note that it is not compatible with the Sam James cowling, I have the standard Vans cowling and I haven't heard of anyone having any problems with this after the move to the G hub. Anyway, I'm fitting the cowl at the moment and I'm wondering whether anyone has some guidance as to just how far back the spinner backplate should sit from the aft section of the hub. This of course will dictate the fore/aft position of the forward edge of the cowl with the stipulated 1/4" clearance. The Hartzell manual specifies a number of different spacer/washer combinations that are acceptable and at the moment I have fitted the single supplied spacer between the hub and the backplate. This is my first prop so my knowledge base is rather limited so I haven't tried twisting the blade to see as I'm not sure if you can do this sort of thing without damaging the prop. A very specific enquiry I know but does anyone have any information as to whether this will provide sufficient clearance from the cowl when the prop is at full coarse pitch? Any help would be much appreciated.

One experience.

The safe way is to bolt it to the flange and measure. I don't know if the Hartzell backplate/spinner floats axially on the piston housing, but if it does, then the gap can be adjusted, but not the distance of the blade.

Make yourself an adapter plate to fit on the governor adapter. This will allow you to pressurize the prop with air (less than 30 psi) and cause the blades to rotate. This is the safest way to ensure you will have clearance. I would not dare twist the blades mechanically. Be sure to check both sides of the cowl. The engine angles to the right and may be closer on that side unless the cowl is set back more to accommodate. I have 1/2" clearance on my RV7 with the james cowl. It has not touched.


Be warned that you can have all the power in the world and the blade angle will determine what speed/rpm you can fly. The typical lowest engine speed that you will get is about 2300 rpm at 160 ktas. As you go faster the lowest rpm will increase. I can back out my governor all the way, a cruise descent at 180 kts, and the lowest I can go is 2400 rpm. This is due to the blade angle stop collar in the prop. This is not necessarily a bad thing, I have found not found it to limit any condition except on powered descent. It is just surprising. I have a -7 with a stock 180 hp engine. If it was a 390 or 35 more hp, it might be different. It took a bunch of flight&mechanic hours and $$$ to learn this.

Spinner/prop

I have the same setup with my -8 and I understand what you are asking....

If you have the standard van's cowling, the prop will not be a factor with the supplied hub - plenty of clearance. Mounting the spinner backplate has nothing at all to do with prop movement, only spinner clearance to the forward edge of the cowling. Place/remove spacers and washers as necessary to get a nice 1/4" clearance and you will be done! The prop will move but the spinner remains the same.

Should be no problem

I've been running this prop/cowl combo for about 2 years with no issues. I had the same concern on cowl clearance. Hartzell has a measurement you can check at a specific station on the prop without going to course pitch. I don't recall the numbers but you should be good.
You made a great choice with the Hartzell prop the performance is incredible!

Kevin

Aerodynamic effects

Anyone that is using this prop on the -8 experiencing negative aerodynamic effects in the flare/touchdown? I've been struggling with this prop to have consistent landings. Seems like it is doing something to the tail and gets a little squirrely or drops out from me. I tested this theory by landing with the prop control full aft during glide testing. It completely removed any weird effect on the tail and landing was like I remembered in my previous RV-8.

I'm also seeing higher RPMs on final at idle throttle which I assume is due to the lighter composite blades. Initially I was seeing very high RPM at idle power in the air until speaking with Hartzell and getting the low pitch stop adjusted. Now I'm at the point where any further adjustment reduces my full power RPM which I don't want to do.

My previous RV-8 had the aluminum blended airfoil hartzell and I don't remember having any issues like this on landing with that prop. I'm considering switching to the BA prop but figured I'd see if anyone else had similar experiences.

Thanks!

Rob Arduini