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Getting more Knots

D

ddnebert

Well Known Member
I have had my RV-10 flying for a year now (150 hours!) and will soon do my condition inspection. I don't have the wheelpants finished/on, but I am reliably seeing only 138-145 Kts TAS at cruise (8500 feet, full throttle, 2400RPM). My plane is a little different than most - I have a carbureted O-540 with a traditional prop (same hub with two F8487A-3R 81" blades). Hartzell engineers assured me that there is only a 6% efficiency decrease on this prop as compared to the vans prop, but I am thinking that the bite on the blade was simply designed for 135Kts cruise, which is what its original installations (Cherokee 235, Maule M7) liked to do. Changing the pitch stops probably won't help, though a prop shop said they'd do that.

The engine burns 11-12gph reliably averaging all phases of flight.
I'm looking for ideas on how to get more speed (fuel efficiency) from the existing system. I've been told that the wheelpants can help up to 9-10Kts by reducing drag, but what other suggestions to you builders have for checking, debugging, and enhancing the plane's performance? I'd sure like to find the extra 30Kts that even the Continental 210HP factory plane has...

Doug.
 
ddnebert said:
I have had my RV-10 flying for a year now (150 hours!) and will soon do my condition inspection. I don't have the wheelpants finished/on, but I am reliably seeing only 138-145 Kts TAS at cruise (8500 feet, full throttle, 2400RPM). My plane is a little different than most - I have a carbureted O-540 with a traditional prop (same hub with two F8487A-3R 81" blades). Hartzell engineers assured me that there is only a 6% efficiency decrease on this prop as compared to the vans prop, but I am thinking that the bite on the blade was simply designed for 135Kts cruise, which is what its original installations (Cherokee 235, Maule M7) liked to do. Changing the pitch stops probably won't help, though a prop shop said they'd do that.

The engine burns 11-12gph reliably averaging all phases of flight.
I'm looking for ideas on how to get more speed (fuel efficiency) from the existing system. I've been told that the wheelpants can help up to 9-10Kts by reducing drag, but what other suggestions to you builders have for checking, debugging, and enhancing the plane's performance? I'd sure like to find the extra 30Kts that even the Continental 210HP factory plane has...

Doug.
Click to expand...

Start with all pants and fairings. I think you'll be shocked.
 
I had no Idea!

That is an awesome video. I had no idea that the difference would be that dramatic.
 
I think you'll find on a -10 that the gear leg fairings and wheel fairings combined add 15+ knots. Sounds shocking but it's been proven multiple times. As I recall when Van's switched from the straight blade to the blended airfoil prop for the -10 it was good for about 5 knots.

Another thing to confirm is flap and aileron rigging. If not quite right it will cost a few knots as well. The reflex position is good for about 3-4 knots over 0 degree position.

Bob
 
mkjprice said:
That is an awesome video. I had no idea that the difference would be that dramatic.
Click to expand...

Think about the low pressure area created on the back side of the gear leg... over the total length of the gear, multiplied by two or three gear legs.

That's a significant amount of surface area!:eek:
 
Fly a GPS box and verify your static is truly the correct static pressure.

I had installed those lovely machined static ports you can get from Spruce, turned out even with the fairings and spats on I had the slowest RV10 in the world, and then I flew a GPS box and I found I was reading IAS -9knots.:eek:

I tried gluing a rivet head over the face of the static port, like the one that Vans supplies. Now I had the fastest! :D IAS was now reading +6knots.

After some mucking around with different things the picture below was what we ended up with almost by accident.

20072010001.jpg


Get your spats and fairings done and do the GPS TAS test. Good luck!
 
Reflex speed

bcondrey said:
I think you'll find on a -10 that the gear leg fairings and wheel fairings combined add 15+ knots. Sounds shocking but it's been proven multiple times. As I recall when Van's switched from the straight blade to the blended airfoil prop for the -10 it was good for about 5 knots.

Another thing to confirm is flap and aileron rigging. If not quite right it will cost a few knots as well. The reflex position is good for about 3-4 knots over 0 degree position.

Bob
Click to expand...

Are you saying that 'reflex' will gain 3-4 kts? Interesting. Hartzell's assessment (by the engineering calculations) was about 3Kts difference.

OK, so I'll get those wheel pants done! :rolleyes:

Doug.
 
Yes, the proper setting of full up flaps "reflex" and ailerons will help the speed.

Dont know what Hartzell has to do with flap rigging:confused:
 
don't feel bad

You are far from the slowest- 10. With about 40 hours on mine and all fairings installed 23 MP and 2400 RPM at 4,000 PA I am unable to get above 147 kts TAS.

Eric Kallio
 
fairings

Some time ago, I don't remember who - perhaps they will speak up - mentioned that the alignment of the fairings has a big impact on their performance. You need to adjust their alignment through a series of iterations/flight tests. You may be able to tuft them. Check the history of similar discussions in the forum.
Sometimes cooling drag can make a difference if you have leaks up front.
 
All RV-10 speeds in SARL Sanctioned races

RV-10s are just starting to show up in SARL Sanctioned races and I found only six records in the race flight statistics. For these and any other aircraft that have raced and accumulated 1036 data records as of the Indy race on 8-13-11, you can go to www.sportairrace.org, click on "Records and Stats", click on "League Statistics", and finally click on "All Speeds by Aircraft Type" and the Excel file sorted by aircraft type in alphabetic order then by speed from fastest to slowest will be downloaded to your computer. The list below shows the speed in knots only since that is what you are interested in but both kts and mph are included in the file.

RV-10 Nafsinger, Nick 191.47
RV-10 Schmidt, Scott 184.14
RV-10 Strasburg, Sean 183.43
RV-10 Arter, Warren 182.18
RV-10 Dawson-Townsend, Tim 159.89
RV-10 Kristensen, Ivan 150.09

This is Nick's RV-10 in the fuel line at Taylor, TX in November 2010, after he completed his 191.47 kt (220+mph) race flight. He has his fairings installed.
IMG_4706-1.jpg


At the site indicated above there are also files sorted by race and speed, speed only, class and speed as well as pilot and speed which include all 1036 race flights completed to date. I have the duty of maintaining them so if you run across some errors, let me know.

Bob Axsom
 
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Mike S said:
Yes, the proper setting of full up flaps "reflex" and ailerons will help the speed.

Dont know what Hartzell has to do with flap rigging:confused:
Click to expand...

Two subjects:
1. On prop comparison, Hartzell said I should be 3 kts slower.
2. By 'reflex' you mean fully 'up' (-3degrees) should get 2-3 kts over takeoff (0deg) position.
 
ddnebert said:
2. By 'reflex' you mean fully 'up' (-3degrees) should get 2-3 kts over takeoff (0deg) position.
Click to expand...

Yes, and the ailerons too, the entire trailing edge should be a straight line from the wing tip to the wing tip.

Dihedral, and fuselage exempted, of course:rolleyes:
 
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Fly higher

eric.kallio said:
You are far from the slowest- 10. With about 40 hours on mine and all fairings installed 23 MP and 2400 RPM at 4,000 PA I am unable to get above 147 kts TAS.

Eric Kallio
Click to expand...

The plane is not very efficient down low. I am always amazed at how much differently the plane flys at lower altitudes. For one the MPG goes way down for a higher aispeed at the lower altitudes. The plane needs the thinners air for efficiency.
 
Finish before re-rigging

Just a suggestion finish building your airplane by installing the fairings perfectly inline with the centerline of the airplane and test the speed using a standard procedure at a specific density altitude using three or 4 different direction legs and process the results with the NTPS.xls file (spreadsheet) and get a baseline speed before you start rerigging and buying new parts.

Van's test results and mine concur with what Hartzell told you. The BA is 3 kts.
Faster.

Bob Axsom
 
Don't know when the speed results for Ivan were posted but we talked at OSH this year and he confirmed that the wheel pants and gear leg fairings made a huge difference in his speed once installed. I suspect the numbers shown were prior to him installing them (he just recently did it).

Bob
 
30 Knots

What if there really is a 30 knot speed mod? From racing sailplanes as well as my aerospace career, I've been involved in a number of drag reduction projects. However, it's interesting to share a fresh approach.

A few years ago, NASA conducted personal air vehicle research that focused on door-to-door trip speeds. What?s really slowing us down? While our airplanes are very fast, NASA found that inter-modal delays (example; picking up a rental car) and driving times are cutting our overall trip speeds in half. They went on to conclude that, ?strategies addressing delay are more attractive than the traditional approach of increasing cruise speed.?

What does this mean for an RV-10? Below, we can see a typical 200nm cross-country in an RV-10. After accounting for inter-modal delays and ground commute, the door-to-door trips speed is only 98.6 knots. In the second column, we can see that a conventional 5-knot speed mod has very little effect on the overall trip speed.

Speed.jpg


How can I get there even faster? MotoPOD LLC developed a patent-pending motorcycle carrier to provide pilots with immediate ground transportation at any airport. After landing, it takes around 90 seconds to remove the motorcycle, unfold the handlebars and ride away. This drastically improves trip speed in two ways:

1)Inter-modal delays: The average time spent in a rental car office is 21.5 minutes? not including the time spent making a reservation or returning the car. By comparison, bringing a street-legal motorcycle allows the pilot to transition from flying to riding in as little as 90 seconds.

2)Drive Time: Only 1/3 of public airports have ground transportation services. A motorcycle allows pilots to utilize 300% more airports and land closer to the final destination. The average drive is 11 minutes shorter.

In the third column, you can see how the motorcycle affects door-to-door speed. By addressing the weakest links in our trip, the door-to-door trip speeds are boosted by just over 30 knots! No other speed mod comes close! Furthermore, it?s probably the cheapest speed mod. A fancy prop or engine upgrade can cost upwards of $10,000/knot (trip speed). At around $15,000, the motorcycle and carrier are less than $500/knot.

When people first see my belly pod, they often ask, ?How much does that slow you down?? While this would be a relevant concern to a pylon racer, it really shows a narrow focus. As far as reaching my everyday destinations, nothing else will get me to grandma?s house faster. According to my calculations, I should be competitive against multi-million dollar jets on a typical 200nm trip.

Several of my friends have much faster airplanes and I once tried to arrange a simple race. My proposal was to select a random restaurant from a phone book and see who gets there first. The loser would pay for lunch. Unfortunately, I never found any takers. Not only were they concerned about losing the race, but they also felt that it wasn?t very fun or convenient to visit an off-airport restaurant. Perhaps more than speed, this illustrates the benefit that I enjoy most. With immediate ground transportation at every airport, I?ve enjoyed flying to new places, exploring destinations and traveling more conveniently than before.

 
My set-up

IO-540 w/Lightspeed and 1 slick mag and the standard Hartzell 2-blade prop. James cowl (this is where I contribute much of my problem to with cooling drag). Pants and fairings are on and aligned. Flaps are set with the reflex and there is no aileron droop. Until recently the ceilings have been solid overcast with strong storms on the weekend. Clear blue skies though as I sit in my office or in the helicopters. I would expect to see about 160+ as I get up to and above 8,000 feet. I have been tweaking the CG in my recent flights to get as close to neutral elevator trim position in flight to even reduce the drag from the tab (adding weight in the baggage compartment to shift the MAC closer to center of the range has improved the in-fllight attitude and I saw 8 KTAS from this). Each little thing gets a little more speed. After my upcoming deployment I am going to tackle cooling drag and plenum issues with the James cowl to see if I can't wring out a little more with a more efficient flow through the plenum. I am never going to win any races, but I dare not say I am unhappy. Love the plane, even if I am the last one to the party.

Eric

Phil said:
Details Eric!!

What are you running?

Phil
Click to expand...
 
And that wasn't a straight line speed

That was on an over 100 mile course with seven legs and seven sharp turns. Most were around 90 degrees and two nearer 180 degrees. One turn of more than 90 degrees was at the start line - hence equal number of legs and turns. It was an impressive performance.

Bob Axsom
 
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Yeah but...

aerhed said:
If I could get mine to a hunnerd&ninety knots I'd be up for more than a sandwich for sure.
Click to expand...

Did you notice his funky air exit flap? Looks like an adjustable exit which he can close at speed for even less drag.

Notice the tape around all joints in the cowl, gear leg fairings and tail fairing.

He also has the fresh air vents closed and taped....no telling what under-hood mods he has too.

Mine will run 186 Knots down low, WOT with none of the above! The fit and finish and attention to detail by the guys in Big Fork, Montana, who built her, makes a big difference in beating Van's posted numbers for the -10.

Best,
 
Pierre

How is it you get that and what is your instrument error............not that I am racing you.....:rolleyes:........... but I am keen to know your secret for altitude, fuel flow (leaned for best power etc.

I have seen 181 knots at 1000' straight and level....maybe I need some speed mods ;)
 
Reflex

I know that flaps have been reflexed successfully on many different aircraft. However, it is important to make sure the stall/spin characteristics are not harmed. The stock wing is designed to begin stalling at the wing root and reflexing the flaps too much can result in tip stalls. Make sure you evaluate this part of the flight envelope.
 
A coupla things

RV10inOz said:
Pierre

How is it you get that and what is your instrument error............not that I am racing you.....:rolleyes:........... but I am keen to know your secret for altitude, fuel flow (leaned for best power etc.

I have seen 181 knots at 1000' straight and level....maybe I need some speed mods ;)
Click to expand...

Hi Oz,
One secret is to run the revs back a little from 2700 (Suggested by Alan Barret of Barret Precision Engine fame)...I picked up 3 MPH doing that while watching the Dynon 100 read my TAS. I also have the Hartzell blended airfoil prop...supposedly the fastest of props for the -10. I was solo with the back seats and cushions out and nothing in the baggage area. I also leaned a little, watching CHT's and EGT's carefully but still burning over 20 GPH.

I don't believe that I have much, if any airspeed error since both the Garmin 496 and 430 W agree with the D-100 on a calm day....plus, I set top-time-of-day for two years running in the Race to Ridgeland (South Carolina), beating a Corvette-powered -10 and a -6 and -7 as I recall, and this year also did the cross-country portion just a tad quicker than a retractable IO-360 Lancair...by 45 seconds according to the timers:)

The airplane was washed and chamois dried, not waxed..no bugs anywhere on the wings.

Best,
 
I also leaned a little, watching CHT's and EGT's carefully but still burning over 20 GPH.
Ah Ha! I can't shovel in that much energy at this altitude. Plus I really only got about 3 hours with the fairings before I took them back off (sage stumps). I saw the tape, but I missed the cowl flap thingy.
Any new word on Larry's exit fairing? Curious minds want to know.
Click to expand...
Click to expand...
 
Nothing like twice the fuel flow for another 20 knots! :D:D

Did I say twice the fuel flow..:eek:

I wonder what the optimum RPM is for climb with the Hartzel, I always climb at full rpmwhich displays as 2670-2680, but as you have noted the slight reduction seems to get less blade drag losses. Maybe 2600 is the sweet spot?

What do you think?

Cheers

David
 
Science project

I'd be interested if someone would spread dirty oil on the plane and take in flight pictures. I am curious if there are any seperation bubbles on the wings or tail outboard of the prop wash. Seems to me there should be some boundary layer trip strips on the lower side of the wing outboard of the prop wash.
 
You're in Oz but I'm here

RV10inOz said:
. Maybe 2600 is the sweet spot?

What do you think?

Cheers

David
Click to expand...

I'm not gonna divulge my revs during the race but it was a bit over 2600. You just have to go experiment:)...and it's sooo fun outrunning Bonanzas and 210's with fixed gear!:D

Best,
 
Here is my data on power required with and without wheel fairings. Other data for drag is on my web page under flight testing.

power.jpg
 
Here is a comparison of thrust required for level flight with and without wheel fairings. (The previous post was power required for level flight). The wheel fairing reduced minimum drag from 257 lbs to 231 lbs at best glide airspeed.

Without wheel and leg fairings
thrust.jpg



With wheel and leg fairings
thrust_fair.jpg
 
A year or two ago I remember seeing a post about someone that was making after market main gear wheel pants for the -10. Not sure if it was on this forum or somewhere else. Anybody know the status of that project?
 
pierre smith said:
Did you notice his funky air exit flap? Looks like an adjustable exit which he can close at speed for even less drag.

Notice the tape around all joints in the cowl, gear leg fairings and tail fairing.

He also has the fresh air vents closed and taped....no telling what under-hood mods he has too.

Mine will run 186 Knots down low, WOT with none of the above! The fit and finish and attention to detail by the guys in Big Fork, Montana, who built her, makes a big difference in beating Van's posted numbers for the -10.

Best,
Click to expand...

Sorry I'm so late to the party guys, I just saw this thread.

A little history on this particular -10 and my race speed.


The funky air exits, they are just that. Cowl flaps. Fully functional, open for TO, closed for cruse. Been there since HR 0. No other under cowl mods (at that time.....) Race prep included all seams taped, steps removed, and vents sealed. I also turned the prop up to 2750 for the race. Verdict is still out on if the prop speed helped or not, Bob A has done more research on that one.

The speeds that I've seen Pierre post, I'd venture to say we are almost identical. One day I'd like to go toe to toe and find out.


Real life numbers, 177 knts @ 8500ft @14 GPH.


What I've learned about the 10 in nearly 200 hrs. She does not like to be down low. You "can" go fast low, but you are going to burn a LOT of gas. Go to at least 8000 ft and let her run.
 
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Like mine.

Hi Nick,
My numbers pretty well match yours at 7,500 or so. Funny thing...I went 178 K TAS last week, at 75% power but I had a 140 lb. PT-6 gearbox in the back seat, so I had an ideal CG with only me in the front.

FYI, last May I did Top-time-of the day, running 188K TAS at 1200', WOT and burning near 23 GPH! during the Race-to-Ridgeland...a 145 mile 4 waypoint cross-country.

I'll let you in on my discovery...2630 RPM was 3 knots faster than last year's speed. These numbers from my Dynon 100 and the time calculated by individual stop watches at the finish line.

Best of luck,
 
Nick said:
The funky air exits, they are just that. Cowl flaps. Fully functional, open for TO, closed for cruse.
Click to expand...

Nick, any chance of more details on this, like photos, and how it affects CHT's etc??

Thanks in advance.
 
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