Wingtip to Wingtip - Family Racing!

Ironflight · #1 01-11-2010, 12:26 PM

Louise and I were formatting on the way home from lunch yesterday, and since the air was smooth and clear, and we?ve both been thinking that her RV-6 gained quite a bit of speed with the new style wheel pants, we thought a little wing-tip to wingtip speed comparison was in order. I have often remarked that ?Mikey? is one pretty fast ?stock? RV-6, and was interested to see just how it did. (Bob Axsom needs not worry - neither of our airplanes ahs any speed mods or particular clean-ups. This is really a comparison of ?stock? machines.)

I slid out from the wing position and lined up even, we gave a count, and both went full-forward on the power at the same time. At 2700 RPM and full throttle, I was indicating about 95% power in the cold air at 3500?. Initially, the RV-8 pulled away - slightly better acceleration - but it didn?t take long before the opening rate was slowed to a very slow crawl. With the autopilot on, I stabilized at TAS of 182 knots (as computed on the EFIS) in the -8, and I?d guess that Louise was about 2 knots slower, call it 180. She was showing about 4 knots higher than that, but hasn?t done an airspeed calibration since she bought the plane. My phase 1 testing showed my airspeed system to be within 1.5 knots at top speed, but that hasn?t been rechecked in the 4 years since.

The intention was not to get absolute speeds, but to compare the 2, and I must say I am very impressed with RV-6, Kit #4, with the Pressure Recovery pants! Van?s quotes a top speed of 182 knots for the RV-6 on the web site, and 185 for the RV-8 (solo weights). Since we weren?t at Sea Level, and the systems weren?t recently calibrated, I?d say that we are getting pretty close to book values on both (within the accuracy of this unscientific test). When I did my Phase 1 speed run ?on the deck?, I got 186 knots if I recall correctly.

I guess I?m not going to be able to use the ?let?s take the -8 on the next trip, because it?s significantly faster? excuse anymore?..

Paul

n5lp · #2 01-11-2010, 01:07 PM

And I have a couple of questions.

You said that your RPM was 2700. Was Louise's the same? If I remember correctly her governor sometimes won't allow 2700.

Don't you have a blended airfoil prop and doesn't Louise have an older design?

Ironflight · #3 01-11-2010, 02:08 PM

Quote:

Originally Posted by n5lp

And I have a couple of questions.

You said that your RPM was 2700. Was Louise's the same? If I remember correctly her governor sometimes won't allow 2700.

Don't you have a blended airfoil prop and doesn't Louise have an older design?

Yes, I should have said we both ran 2700 RPM (her governor is actually running 2750 - I need to adjust that someday....) and yes, if she starts asking for a BA prop, I'll be in real trouble...

RFazio · #4 01-11-2010, 03:03 PM

So how much difference do you think you got with the new pants? I have the old style pants also. I've been thinking of changing them, but how much can I really expect?

Ironflight · #5 01-11-2010, 03:45 PM

Quote:

Originally Posted by RFazio

So how much difference do you think you got with the new pants? I have the old style pants also. I've been thinking of changing them, but how much can I really expect?

I'd have to go look that up in a post we made last year wen they were changed, but I think it was on the order of 4-5 knots for the new style pants and all new fairings.

Paul

Mikey · #6 01-12-2010, 06:46 AM

Paul,
You didn't mention that I had those draggy tie-down rings on and the Val was clean. I'm sure that slowed me AT LEAST 2 knots!

dabney · #7 01-12-2010, 10:23 AM

I bought a RV6A second hand and am not aware of any airspeed calibration that may have been performed by the builder. How do you do that??

Ironflight · #8 01-12-2010, 10:45 AM

Quote:

Originally Posted by dabney

I bought a RV6A second hand and am not aware of any airspeed calibration that may have been performed by the builder. How do you do that??

If you are going to do any meaningful testing, the first thing you probably need to do is figure out if your instrumentation is accurate. Kevin Horton is the real expert here on that stuff - here's a page from his web site with several good methods:

http://www.kilohotel.com/rv8/phplinks/index.php?&PID=49

Paul

rvmills · #9 01-13-2010, 12:29 AM

Quote:

Originally Posted by Mikey

Paul,
You didn't mention that I had those draggy tie-down rings on and the Val was clean. I'm sure that slowed me AT LEAST 2 knots!

Mikey,

Me thinks your pilot is a SARL racer in disguise...comments like this are oft-heard among racers!

Sure hope you'll bring her out to a race soon...and when you do, get your hangar-mate to bring her hubby along too!

Cheers,
Bob

Louise Hose · #10 01-13-2010, 09:10 AM

Quote:

Originally Posted by rvmills

Sure hope you'll bring her out to a race soon...and when you do, get your hangar-mate to bring her hubby along too!

Cheers,
Bob

Or, are you suggesting that he makes me sleep in the hangar?