Which Prop

Rob Hanberg · #1 08-07-2006, 08:01 PM

I have a RV7A IO360 Forward facing Sump, 180hp, AeroSport Engine. I'm ready to purchase a prop. I'm trying to decide between the 72" C2YK-1BF/F7666A4 that Dan has on his plane OR the C2YR-1BF/F7496-2 blended air foil. There is about $150 difference in Vans prices. Does anyone have any experience with both? Dan seems to have a fast plane with his.
Thanks.....Rob

rickmellor · #2 08-07-2006, 08:20 PM

It's not one of your options ... but my choice is one of these plastic dealies.

http://www.whirlwindaviation.com/series200rv.php

dan · #3 08-08-2006, 12:18 AM

Didn't Van's run tests and determine the BA to be a few mph faster? I'd personally go with the blended airfoil for a parallel valve 360.

Somewhat unrelated rant...

Hartzell recently came out with a new BA blade, the 7497, which is approved for use with the angle valve IO-360 (at least some models...read on). Lately I've been saying that if I had to get a new prop today, I would go with the BA if it was available.

However! I looked carefully at the TCDS and found that the 7497 is actually not approved (yet?) for my IO-360-A1B6 engine. It's approved for the IO-360-A1A, among other non-counterweighted angle valve models, but not the -A1B6.

And what's interesting is that the 7497 does have the following placarded RPM restriction:

Quote:

Continuous operation is prohibited above 24 inches manifold pressure between 2350 and 2550 RPM

...whereas the F7666 blade which I have currently has an unlimited RPM range, no restrictions whatsoever, with my particular engine. I do cruise between 2100 and 2300 fairly frequently these days.

So I take back what I've been saying. Until/unless the 7497 (or another BA blade) is approved for the IO-360-A1B6 with no RPM restrictions, I would not be interested in upgrading.

However, for a 180hp parallel valve 360, where you're gonna have a placarded RPM "avoid continuous operation" range regardless of BA 7496 vs. non-BA 7666, I'd go with the BA.

Ironflight · #4 08-08-2006, 07:04 AM

Wasn't it Randy Lervold that did some of this testing Dan? I know I read an excellent write-up, but it isn't on his site - maybe it's in the compilation of the Rvator?

At any rate, it proved to me that if you're trying to decide between the BA and older style Hartzell's, the price difference for th extra knots was negligible. People pay thousands of dollars per knot when trying to clean up aircraft, and here you get several knots for a couple hundred dollars.

Captain_John · #5 08-08-2006, 09:06 AM

Not to hijack a thread, but to hijack a thread...

I really like the Hartzell BA but really like the IO-390. Really, really like it.

I understand the BA not to have any restrictions with the counterweighted IO-360 and am hoping the same would be true with the IO-390.

I am not certain that anyone has done any testing on this combination. If so, are there any restrictions?

Anyone?

CJ

dan · #6 08-08-2006, 09:10 AM

Quote:

Originally Posted by Ironflight

Wasn't it Randy Lervold that did some of this testing Dan? I know I read an excellent write-up, but it isn't on his site - maybe it's in the compilation of the Rvator?

Yes and no. Randy did a terrific comparison of some props, but the BA wasn't around then. His comparison was mostly between the Hartzell F7666 and at least two Whirlwind props. http://www.romeolima.com/RV8/Prop.htm

Quote:

Originally Posted by Captain_John

I understand the BA not to have any restrictions with the counterweighted IO-360

Please re-read my reply. The BA (7496 or 7497) is not approved for the counterweighted IO-360.

Captain_John · #7 08-08-2006, 09:20 AM

Ahhhhh, I see! I scanned too quickly and misinterpreted what you wrote.

Of course, there is no information regarding the 390 on that FAA hyperlink you posted, a prudent man would follow the recommendations of the comparable IO-360 until more testing has been done or go with another manufacturer.

Agreed?

CJ

osxuser · #8 08-08-2006, 09:11 PM

I feel (and this is just me) that the rpm restrictions are somewhat arbitrary in nature. Yes there are harmonics that happen between certain RPM ranges. I know the Cardinal I fly is placarded "Avoid continous operation between 2100 and 2300 RPM", and just a smidge under 2350, I can start to feel the harmonics, and it goes away long before 2100, it seems that Hartzell has to take into account possible tach errors when they set their harmonic ranges, so the ranges end up a lot bigger for certified aircraft than it should be. I'd guess the harmonic range is actually 50 RPM or so buried in the middle of what they say to stay away from.

For my money, it's an experimental, so if you want the BA to go faster, get it, install it, feel where the vibes are, and avoid those ranges. IO-360, IO-390 shouldn't matter much...

Just my 2?

Ironflight · #9 08-08-2006, 09:40 PM

OK, I found the article I thought I'd remembered....it was in the 2003, fifth issue of the RVator - first article.They did test the BA prop and compared it to the standard Hartzell and some of the composites.

I knew I'd read the test results somewhere!

Paul

N941WR · #10 08-09-2006, 06:37 AM

Quote:

Originally Posted by osxuser

IFor my money, it's an experimental, so if you want the BA to go faster, get it, install it, feel where the vibes are, and avoid those ranges. IO-360, IO-390 shouldn't matter much...

Just my 2?

Just be careful! Maybe add a safety cable to your engine like the racers are required to do.

Here is a picture of a friend's WACO UPF-7 after he lost 17" from one blade. He was out over the water at 900' and the parking lot is an empty Staten Island Ferry lot. Notice the weeds on the right gear. He picked that up from bouncing it off the berm in the background so he could make the lot. Also note the light pole he swerved around on roll-out. Man, that guy is good and lucky! Oh, and he said it didn't glide very well w/ the engine hanging down like that.