[Webb]

After reading some of the post on speeds, I'm starting to think that when it comes to speeds, RVer's are telling bigger whoppers than fisherman.

I read the measured speeds from airracers, and they seem to be less than some pleasure fliers out there and the racers are pushing their planes to the max.

I've got an ideal. Since Van's posts speed numbers for their planes with different horsepower, I think we should set parameters for a 4 way gps reported test at a specific altitude, specific MP if CS, and RPM. Someone who likes to do spreadsheets and the math, could put the data down for the different models and HP they are rated at. With as many planes here, we could post actual averages for speed on a link once the results are in. It would be interesting to see how we compare to what the Mothership posts.

I recommend 8,000 feet like Van's does, and 75% power.

What about it?

 

[pierre smith]

I'm in..

....Just sitting here bored anyway Would you like us to get started now?

Regards,

 

[Rick6a]

Uh Huh

.......RVer's are telling bigger whoppers than fisherman......

Webb,

I agree with your proposal....in principle. However....and this is a very big however..... what makes you think those who are prone to exaggerate performance claims (among other things) are suddenly going to get religion and honestly report how their RV truly performs? You are essentially inviting the perennial "story teller" to shoot craps over the telephone. Don't bet on it.

 

[Bryan Wood]

Great thread Webb

Webb,

I've flown my 9A with 2 identically powered RV-6's several times and one I can stay up with and one I can't by a long way. I think there is something to the claims of some of the folks who built truly straight and light airplanes. The fairings, wheelpants, aileron and flap rigging, horizontal stab incidence, all seem to add up. Engine baffling seems to be huge and even the exit area from the bottom of the cowl can affect drag greatly from what the racers are claiming. I've read one well known RV'er several times claiming that his speed runs were with the fresh air vents closed because the plane flys faster. Others use ballest to get an aft cg for increased speed. These are all things we do to our planes as individuals and there are a lot of really clever people on this list. I'm humbled often by what I thought I knew prior to one of these folks joining in and fixing my understanding. I even read an article years ago about a once very popular paint design on the wings causing a disruption of airflow and a speed loss. I'm sure everybody has seen it where the leading edges are a different color than the rest of the wing. The paints sharp edge on the top of the wing has been shown to affect the flow with the use of tufting?. Because that article along with its supporting pictures my paint ideas specifically left that out on all the ideas we were considering. Then there are folks who choose to cut their wheel pants so that the clearance to the ground is minimal for increased speed, and others that look like Cherokee pants. There really are a lot of variables that could explain some of the claims. There are the taildraggers with skateboard type tailwheels, and then somebody comes along later and makes a fairing for the skateboard wheel for even less drag. I remember seeing pictures from the old Yahoo Groups days of VAF of people machining parts to streamline them and thinking about how I hoped that I can just finish my plane. It always amazed me how some of these buiders can go off on these tangents and ever finish their plane, but they did so over and over. Props are a big player in all of this also. I know somebody who dumped his Sensinich metal prop for a pricey MT and lost 11 mph in cruise. Then the whirlwinds and Catto's came along for later builders. They are remarkable. It just keeps getting better and better for the builders these days.

In a related, but different concept... Is a plane that is hand flown on a 4 way speed test have as high of an average speed as one that is flown by coupled GPS with altitude hold engaged?

 

[osxuser]

I think that's pilots in general. We had a guy that claimed he could cruise at 300mph in a 180hp Glasair I RG...

 

[John Clark]

Procedures

You are essentially inviting the perennial "story teller" to shoot craps over the telephone. Don't bet on it.

Great line, Rick!

But I'm in anyway. If we had a sizable database of rational numbers it might keep the bravado to a minimum. What we need is a simple set of standard procedures for the "test."

John Clark
RV8 N18U "Sunshine"
KSBA

 

[Mel]

I even read an article years ago about a once very popular paint design on the wings causing a disruption of airflow and a speed loss. I'm sure everybody has seen it where the leading edges are a different color than the rest of the wing. The paints sharp edge on the top of the wing has been shown to affect the flow with the use of tufting?.

This phenomena shows up mostly on laminar flow airfoils. The paint edge trips the laminar flow causing the airplane to fly at a higher AOA. It has very little effect on turbulent airfoils like the ones used on RVs.

 

[N941WR]

What is 75% power?

This is like when I was racing and instructing. Some people would never use the entire power range and wonder why some cars are so much faster than theirs. The answer was the fast drivers knew exactly where the rev limiter was and weren't afraid to bounce off of it.

Back to planes, to get 75% at 8000? DA most people will have to push the throttle full in and run right at the redline. This is normal and acceptable but many pilots do not fill comfortable spinning their engines that fast.

So you will have some people reporting much higher speeds simply because they are running 75% power while others are simply think they are at 75% and are running slower.

BTW, this doesn?t take into account those who have ported engines, electronic ignition, tuned fuel injection, etc.; all of which increases power.

 

[zspivey]

RVer's tell whoppers?

After reading some of the post on speeds, I'm starting to think that when it comes to speeds, RVer's are telling bigger whoppers than fisherman.

I read the measured speeds from airracers, and they seem to be less than some pleasure fliers out there and the racers are pushing their planes to the max.

Surely not. Remember we are the most honorable people around; we are pilots.

Now let me tell you about the last trip I took. I was at 8,500 feet, full throttle with the prop set a t 2400 RPM. I ran my carbureted engine 50 LOP. I was able to get 200 knots while only burning 6.5 gallons per hour.

 

[Mike S]

Surely not. Remember we are the most honorable people around; we are pilots.

Now let me tell you about the last trip I took. I was at 8,500 feet, full throttle with the prop set a t 2400 RPM. I ran my carbureted engine 50 LOP. I was able to get 200 knots while only burning 6.5 gallons per hour.

And, that is ground speed into a 50kt headwind, correct???

 

[f1rocket]

I think some of it is a result of most builders not calibrating their airspeed indicator. Most builder/flier don't really know how fast or slow their airplane truly is. Just flying with the buds have uncovered as much at 5-7 kts difference in our collective indicated speeds.

 

[lostpilot28]

Back to planes, to get 75% at 8000? DA most people will have to push the throttle full in and run right at the redline. This is normal and acceptable but many pilots do not fill comfortable spinning their engines that fast.

Hey Bill...this is a great point, but I think if you standardize the data then who cares if you're running at 75% or 90%? Basically, I would say that each pilot has to record RPM & MP & GPS speed for each of the 4-legged course at 8,000 Density Altitude.

It would also be great to have aircraft weight for the test flight, what engine, prop and model RV it is.

 

[Christopher Murphy]

This is exactly what we are talkin about

Surely not. Remember we are the most honorable people around; we are pilots.

Now let me tell you about the last trip I took. I was at 8,500 feet, full throttle with the prop set a t 2400 RPM. I ran my carbureted engine 50 LOP. I was able to get 200 knots while only burning 6.5 gallons per hour.

This post has no useful information to compare speeds. Maybe thats your point? I like the guys who take pictures of their EFIS and use that to prove their speed.

 

[zspivey]

RVer's tell bigger stories than fishermen

This post has no useful information to compare speeds. Maybe thats your point? I like the guys who take pictures of their EFIS and use that to prove their speed.

As an earlier poster corrected my statement. The 200 knots was ground speed into a 50 knot headwind.

Remember, the first liar never stands a chance.

 

[Kahuna]

I dont think this will work cause most people just dont care.
Their speed is what it is.
Most don't even bother to calibrate anything. They post numbers and they dont know what they are doing.

We have enough test data running around to guess your speed +- a few knots anyway. There are lots of good data capture guys who are really into it, it takes real work, time, and avgas money.

Some bogus data gets posted and we call BS. We dont see them back. When this happens, the system is working as designed. Coming to the forum with your info, it better be right, cause we can call you on it if the numbers dont add up. And we do. Simple formulas and graphs get us very close to reality.

The real useful stuff comes from the folks who do actual flight testing and make changes/improvements. Folks do actually find that interesting, as they should.

Bottom line, to make it worth while, takes many many many hours of testing, calibration, logging, plotting, and publishing. Most are not up for the task. Heck even something as simple as weight we find is bogus. Folks weighing before paint, or w/o fairings, or without cross testing scales, or what ever.

Anyway, you get my point.

 

[SteinAir]

This is a good thread. Often times people ask me what I cruise at in the RV....my answer is always "7.5 or 8 gallons per hour". Whatever that equals in speed on that trip is what it is, I rarely pay attention. I shove the black knob in all the way, then play with the blue and red knobs to get what I want. I mess around until I get my 7.5 or 8 gph and there I am! Now, if someone else is paying for the gas, I might let that speed creep up to 9 or 10 gph!

The funny thing is that no matter how fast you think you are, there is always likely someone faster. With my old RV6 years ago, I never spent a lot of time doing all sorts of testing and calibrations to figure out exactly how fast it was. What I do know is that I could beat almost every RV around here when we were all leveled out and wide open (sometimes barely, but mostly I could). There were some faster than me, which I never took offense to - I look up to those guys! Of course I had a pitched up FP prop, and a good strong injected engine pulling a really light and straight airframe to help.

In the end it just doesn't matter that much. It's nice to see people get the planes done, get them in the air and go fly. I don't know if my current project is going to be faster or slower than I anticipate; I really don't care. I'm making the plane the way I want. Luckily I know none of my planes are the fastest, lightest, best looking RV's out there so I don't have much to worry about. I figure mine are better than a lot of planes, but not as good as some....which is the case for almost all of us (except for Rick Gray, Lyle Hefel and a few others)!

In the end, the first post was right though. There are some whoppers told here once and awhile - and it's easy to see right through them if you've been around the block once or twice.

My 2 cents as usual,
Stein

PS, ditto on what Mike said!

 

[allbee]

I like to add that I love my RV. I was more interested in getting close to published speeds than anything else. I'm happy to say that I am. and the fuel burn is an extra as well. With fill ups that record 7.5 to 8 gal per hour. with speeds from 150kts to 160kts generally recorded from my 696 on ground speed.

I get the most kick out of passing a cessna on take off, we have two parrallel runways. Or even passing a cessna that took off ahead of me like it was standing still. I generally here the tower saying to the cessna that an RV is passing on the right, with a "I know" sarcastic in response. I really get a kick when it's one of my hangar neighbors that doesn't like experimentals. That really gets me feeling good.

No matter what we do. There is always somebody that stretches things a bit to make them feel better. I guess it's called hangar flying.

I also have to say that I, like Stein, don't care to much about the looks of my airplane, as long as it gives me a bunch of fun factor. It's built to MY specs.


have a nice day.

 

[L.Adamson]

I also have to say that I, like Stein, don't care to much about the looks of my airplane, as long as it gives me a bunch of fun factor. It's built to MY specs.

I care; at least to five feet away. Beyond that, mine won't look like some of the spit polished fiberglass/ airbrushed/ 10 coats of clear.. jobs we see.

However----------All RV's look like "crud" until they're painted! Only a builder can love them without paint.....

L.Adamson --- RV6A (flying/with paint)

 

[Christopher Murphy]

Right on!

I feel the same way about my -4. No pre-punched, quick build, professional paint job here. Good solid workmanship, nothing fancy, learned enough to do it better next time but still gets compliments. Performs good enough on stock engine to win a few SARL races and the AVC twice. How fast will it go... don't know exactly but fast enough.

Chris M. RACE34

 

[plehrke]

In the end it just doesn't matter that much. It's nice to see people get the planes done, get them in the air and go fly.Stein

The best thing is that there are over 6000 people who have finished their plane, we have a VAF forum to "hanger talk" across the world, and the info on RVs is more documented and verified then any other experimental.

I will listen to anybodies claim of speed or weight but do not have to believe it (unless you believe what I am telling you about my RV). Hanger flying is 90% of being a pilot. Only numbers that matter are Van's, CAFE, the guys/gals flying in the air races, and the guys/gals that spend the time to do the testing correctly. If you want your numbers to be believed then you need to fit into one of those 4 catagories.

I built my RV and love flying it; That makes it the fastest, best looking RV out there.

 

[Steve]

I love it when the tower refers to me as "a fast-mover inbound from the north".

Slower than some, faster than others, still unpainted,
Steve

 

[allbee]

I love it when the tower refers to me as "a fast-mover inbound from the north".

Slower than some, faster than others, still unpainted,
Steve

I had something happen the other day. We had an event going on at the field so things were a bit busy. I called in at 8 miles to the west-north west, was told to enter base for 21R. I was going top speed, ok over 170kts, decending mind you. I was into the base lickety split. When I called in I was greeted with a, you just busted class D airspace. I said, no way, I just talked to you twice. He came back with a, Oh ya you're the one I had troubles getting the tail no. right. SOOORRY. I said not a problem, I'll take 21L, he said cleared for 21L.

I felt bad for him because he was taking care of all the 60square airplanes all morning. Biplane show.

 

[hevansrv7a]

75% and 8000 feet

Van's is defining 75% as 8000' density altitude in the belief that you can't get more than 75% at that density. I believe Van's is both accurate and truthful in reporting what their airplanes will do. Some examples do better. That said, here are some problems that I've become aware of through the generous expertise of people such as Paul Lipps and Kevin Horton. I don't know to what extent Van's deals with this in their measurements.

1. If you haven't used GPS and a good 3 or 4 leg analysis then you don't really know how fast you are going. Airspeed indicators are not accurate.

2. In order to measure density altitude you need OAT. See Paul's article on how that measurement is subject to error. If your OAT is reading high at higher speeds then you are in denser air than you think you are and you are getting more power than you think.

3. The 8000' number is commonly accepted as 75% for factory airplanes with factory induction systems. Many of us are getting either less MP loss or even a gain due to speed. I have measured more than 1" of MP gain as my airplane accelerates while holding 8000' or higher DA. The standard air density at 8000' is 78.6% of standard sea level density. Therefore with a good induction system you could be getting maybe 80% at that altitude.

4. Using air density as the limiter on percent power ignores RPM. Some folks run their engines beyond the nominal red line. If your Lycoming is rated at 2700 and you are turning 2900 then you are using more HP than the air alone would imply.