Steve

Have you tried your new prop yet?

Collin

I have made only two flights with the new prop, but the difference is quite pronounced. The 53/33 inch prop gives 2,900 RPM static, the rate of climb seems about the same as with the Hoffman, but cruise flight is where I really see a difference.

The Hoffman prop made the Fournier feel like it was stuck in 3rd gear. Too many RPM, not enough speed. In aerobatics I was constantly having to reduce power, often when I needed it most, to keep the RPM down.

The Culver makes the RF4 feel more like it is in the right gear. I see 110 mph at 3200 RPM, which is 5 mph more that the Hoffmann provided and the tendency to over-rev during aerobatics is very much reduced.

So far, I like this prop very much. Thank you for the advice!

Steve

The Culver prop sure is interesting, it even looks good and I´ve heard some positive responce from RV-people too.

I still cling to the not so shabby take off performance of the standard Hoffman prop, I use less than 200 m (short, dry grass) untill airborne. Did you notice any change in take-off performance?

May the 4´s be with you/ Jörgen

Also, the prop was just under US$400. Not too bad. People spend a lot more than that to go 5% faster

Steve

110 mph @ 3200 is that at full throttle?

Collin

You probably all know that I'm using a very coarse Australian prop, to keep down the tip speed and noise levels in full-throttle aerobatics.
You will see details elsewhere on this forum.
What really interests me is that I have seen very little discernable change in take-off performance with any of the props I have used, either off grass or tarmac/bitumen.
To make valid comparisons, I fly with one prop immediately after removing the other, so readings are usually within one hour of each other, so that the ambient conditions can't change too much.

Here, on our short British airstrip (less than 400 metres), the take-off run is often downwind and getting over the hedge is vital, but I cannot measure any performance difference with the short, fine-pitched prop against the longer, coarser one.
I can only think the 1400cc VW has a very flat torque curve.
Anybody else out there have any other ideas?

Yours, Bob

When we took off, the air was still and the temperature about 70 degrees F. My static max RPM showed 2850. Joe's 1200 CC/Hofmann RF4 and my 1400 CC/Culver RF4 took the runway side by side and took off as a flight of two. We observed no difference in take off or climb.

In cruise flight, things got interesting. I usually lag behind Joe and often have to ask him to reduce power a little to allow me to catch up without my engine getting too warm. This time the tables were turned - to the tune of 300 rpm. In other words, to allow Joe to keep up with me, I had to reduce RPM by 300 compared to the setting I usually use, and the setting he was using. Joe ran 3,400 RPM, I used 3,100. This difference in performance was consistent throughout the flight.

I experimented with a brief run at full power. I saw 3450 RPM and an indicated airspeed of 118.

This prop has done wonders for the RF4, I think Collin was right on the money though when he suggested that a 32 inch pitch would be better. 33 inches is just a little too much. - I ordered 33" because the prop can always be re-pitched to a lower setting, but not higher. - I may do that, but probably not. It really works pretty well as it is.

Steve

I'm going to order a Culver prop for my RF4D.

You guys had good success with the Culver 53x33 but you mention that a 53x32 would be a bit better?

I have the 1400cc engine and I will be installing the better ratio rockers that Colin sent me that might up the power slightly.

What do you recommend?

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

On the other hand, if take-off and climb were more of a priority, if I operated from a grass airport or frequented short strips, I would definitely go with the 32" pitch prop.

I believe Mira recently ordered a prop from Culver too, so they must be in practice by now.

Steve

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

If your crush plate is the same, you might send it to Culver to make double sure.

Steve

Overall I think the 33" pitch is fine. Flying from Lake Elsinore being dirt and 1200" elevation and very hot in the summer, I would think 32" would be best.

See you next month in Minden and I will be in Lake Elsinore late August.

Collin

I took stock of the work I still need to do before Minden and also schedule an Annual and I just dont think I'm going to be finished in time.

I'd rather not rush so that I can stay focused and do a good job on everything.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

They give us great takeoff performance out of our 400-yard strip (see the YouTube footage, search for FournierBob).
Climb rate is 500 to 600 fpm at max weight (depending on temperature).
They give us excellent aerobatic performance but are much quieter than any other props we have run.
They also give us good cruise performance at 3050rpm, burning 12 litres per hour.

This is all because of the Rectimo's very flat power and torque curves.
See my other posting under engines, or search for 'power curve', or 'torque'.

And don't worry about exceeding 3,600rpm, ore even 4,000rpm.
Road-going VWs rev much higher than that and at that rpm you're just polishing, not wearing the internals.
And yes, the magneto's fine too.

I've spent most of my aerobatic time at over 3,600 rpm, and often over 4,000, sometimes with no oil pressure, although of course I'm using molybdenum disulphide oil additive.

Pick a prop and love it!

Yours, Bob

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Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

It does not seem to be as "Scimitar like" as Colin's prop from Culver below.

[Edit by jb92563 on Tuesday, June 21, 2011 @ 10:06 AM]

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Steve did your prop look like mine or Ray's.

I was planing on having Props Inc copy my prop. They are only a 60 miles (100km) south. I will let you all know when they are ready to make more.

Collin

Steve

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

I send a detail of the bolt circle and spacing, and told them its not a standard pattern and they should use my dimensions.

They got it perfect!

Here is what I sent:

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org