Hartzell composite on RV-4 with SJ cowling

[TR182]

Has anyone strapped the Hartzell N7605W-2X composite blades onto an RV-4 that has a Sam James cowling?

I have sifted through several threads of great experiences with these blades on RV-7’s and -8’s, some with Vans cowlings and some with Sam James cowlings (“short” and “long”) using either the “G” hub (1.00” longer than the “C” hub) on Vans cowlings or the “M” hub (+2.563” longer than the “C” hub) on SJ cowlings. My -4 came with a late 1990’s SJ cowling, HC-C2YR hub with F7666A-2 blades bolted to a Lyc O-360. I understand most SJ cowlings using the “C” hub also have prop spacers of around 2.5”. Mine does not, however the cowling seems to be fitted as far aft as possible which makes the cooling inlets a bit shorter than what might be optimal.

I fly formation and light aerobatics from a high desert airport which can have DA’s over 10K in the summer. From what I have been reading the Hartzell (or WW) prop should perform much better than the F7666A blades.

The cord of the N7605W blades is almost 2x that of the F7666A blades. From a conversation with Hartzell when using the G2YR hub the trailing edge of the blade at station 12” is 2.32” forward of the crankshaft flange when at low pitch and 1.16” at high pitch (34 deg). My SJ cowling front surface is 1.25” forward of the crankshaft flange so by my math (1.16 – 1.25 = -.11”) the trailing edge of the prop at full pitch will hit the cowling. Hartzell suggested using their “I” hub which is 1.0” longer than the “G” hub (which is 1” longer than the “C” hub I have now).

Questions:

Does anyone else have a Hartzell HC-G2YR hub on a -4 with SJ cowling?

If so, what is the distance from the crankshaft flange to the front of your cowling?

Has anyone run a 74” prop on an RV-4? Vans recommends 72” max on their taildraggers, 74” on the -A models. I currently have a 72” but it doesn’t seem like a 74” would be a problem, even with wheel landings.

If I go with the “I” hub I believe I will end up with a 2.00” gap from the back of the spinner to the front of the cowling. Hartzell said there is some (up to ½”) adjustment via washers but at best that is still 1.5” of gap.

What have others done to close the gap?

Any RV-4’s with SJ cowling + composite prop setups out their? I also looked into the WW-74HRT but that hub is really short and would require at least a 2.5” extension.


Thanks!

[BillL]

Mike, I can not answer all your questions but did have similar issues with SJ cowl (long) and the standard hub with composite blades.

The issue is that the far aft position of the blade is much different than aluminum blades relative to the hub flange. That means you can space it out, but aft edge of the spinner is always relative to the hub flange and if spaced for blades, you have to either get a special spinner or extend the cowl nose.

If you can get a spinner that fixes the math (you can run the numbers) then it is easier than extending the cowl nose. I extended my nose and used the Vans spinner. I left about 1/2" clearance at full pitch.

In the end, your 4 is likely less drag than my 7. I hit the max pitch stop at about 2300 rpm, 175 kts, 8000 ft DA - so the RPM just wont go lower. Since this is a little ROP, I have not felt any pain from it, but have no long X-CTY yet to really know. Just sayin' . . . be informed.

I love the prop, and with a little extra pitch it would be perfect. I can get 183KIAS at 2400RPM easily. It seems to like 24-2600.

The SJ cowl is unique (on the 7 compared to the Vans) in that the face under the spinner and the cooling inlets are all in the same plane. (edit: the 4 is apparently not so-see below)


EDIT: ok i have a question. You only want to replace your blades? Or are you going to get a new prop? The reason I ask is that my box stock with the HC-C2YR hub is pitched for a maximum of 27.5 deg. I am wondering if H quoted you the new prop max pitch or 34 deg for your hub and max pitch spacer.

[AX-O]

Originally Posted by TR182

I also looked into the WW-74HRT but that hub is really short and would require at least a 2.5? extension.

Thanks!

I have been dealing with this on my -4 for the WW 200RV (uses same hub as the 74HRT i belive as my bud had his blades just swapped form 200 to the HRT).

I had a 4 inch extension for my fixed pitched prop. Originally I bought an extension that was 2.5 inches. That put the spinner almost 1 inch in front of the cowl.

I then purchased another extension which was 3/4 of an inch shorter (now 1 3/4 inch). This one placed the spinner approx .2 inches away from the cowl. The blade is different than the HRT so this part wont help you with blade clearence. I ended up with approx half inch clearence.

Originally Posted by BillL

The SJ is unique in that the face under the spinner and the cooling inlets are all in the same plane.

That maybe in your case but not in mine. I placed the fuel injection intake flush with the nose of the cowling. So my engine cooling intakes are not on the same plane. Thay are further aft.

[TR182]

Bill,

I plan to sell the current "C" hub and aluminum blades. I was asking Hartzell for help with the "G" hub plus spacer and longer studs (Sabre will sell the spacer but doesn't sell the studs). Hartzell didn't like the idea of any 3rd party spacer and suggested the "I" hub which is 1" longer.

They said the standard pitch for the composite blades on 180-210 HP is in the range of 9 to 15 degrees minimum pitch and 25 to 34 degrees max pitch.

[TR182]

Axel,

What is the distance from your crankcase flange to the front of the cowling most forward point? Mine is 1.25".

[AX-O]

Originally Posted by TR182

Axel,

What is the distance from your crankcase flange to the front of the cowling most forward point? Mine is 1.25".

Will have to measure but I believe it is close to 4 inches.

[TR182]

Update:

I would like to thank Axel and Cipher for the information and advice they gave me at the Madera FFI BBQ this Spring. I ordered the 74? Hartzell composite propeller through Van?s, N7605W-2X blades in an HC-I2YR-1NWX hub. The one inch longer ?I? hub was needed on my plane due to the Sam James cowling which is farther forward at the cooling inlets than the standard Van?s cowling which usually uses the "G" hub.

The propeller arrived a few weeks ago and is now bolted onto my RV-4. The blades have +0.8 inch clearance from the cowling when at high pitch (34 degrees) which is more than needed but better than the alternative -0.2 inches with the ?G? hub Van?s generally sells with this prop. The worst part is that even when using washers to space the spinner back as far as possible there is about 1.25? between the spinner back and cowling nose front. For now I cut a donut out of 1? pink foam and used white duct tape to attach it to the cowling. It looks like it will work, so now I will need to get out the West System epoxy and make a permanent fix.

I must say it is an amazing prop, just as Cipher said it would be. Acceleration is much better and most notable the slower I am going. Take-off and initial climbs are very impressive, even from our +8,000? density altitude airport. Deacceleration is also much quicker. Pull the throttle back quickly and you best have the shoulder straps snug. Top speed seems to be within a knot or two faster than the metal blade Hartzell. It is so hot in New Mexico now that the lowest altitude speed runs I can try without hitting anything is at DA 10,000 feet, I look forward to flying it closer to sea level on a cool day. Cruising at 10K DA I was able to pull the rpm back to 1700 however it sure seems to like 2500 to 2600 and set there it is awesome when flying in a formation.


https://drive.google.com/open?id=1Ml...OK0Pz0Lh_gUbfH

https://drive.google.com/open?id=1pJ...EOGUM6BfjfJBNp


Zap

[BillL]

Originally Posted by TR182

Cruising at 10K DA I was able to pull the rpm back to 1700 . . . . .

Beautiful monster!

I am jealous of speed regulation down to 1700 though.