What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fast RV-10

K

Kyle Boatright

Well Known Member
Many moons ago, I stumbled across a thread where a forum member did a substantial amount of under-cowl and airframe cleanup and had a significantly faster/more efficient airplane than stock.

But I can't find the thread for the life of me.

Does that ring a bell for anyone?
 
Vne has nothing to do with the engine and cowl. If you build something that can "go significantly faster than stock" aren't you running the risk of flutter / structural failure / littering roofs with airplane parts?

My understanding is that a stock RV-10 can achieve Vne probably in level flight, definitely in a dive. Why would you want to "go significantly faster than" that?

Give your plane more power for takeoffs, climb, etc, sure. But increase top speed? You better modify a lot more than just the engine.
 
maybe not a stock -10

A stock -10 probably wont get to those numbers but I can tell you that I typically cruise at about 172-174 KTAS and 200 KTAS can be easily reached in a descent...

Running a 290 hp Barrett EFII engine with CAI...
 
And that illustrates why reducing drag is more effective than adding ponies, just in case the math isn't convincing enough.
Normal cruise on my RV-10, 173kts TAS, stock 260hp Lycoming D4A5. (see attachment)
Just because you can doesn't mean you have to bust Vne in a descent, anticipate the speed buildup in a descent and power back.

Also be mindful of Vno (yellow arc) in the descent when necessary. (156kts indicated for the -10).

Btw, you don't necessarily have to go fast, reducing drag can save you a bunch of fuel.
 

Attachments

  • IMG_3914.jpg
    IMG_3914.jpg
    426.3 KB · Views: 289
Lenny Iszak said:
And that illustrates why reducing drag is more effective than adding ponies, just in case the math isn't convincing enough.
Normal cruise on my RV-10, 173kts TAS, stock 260hp Lycoming D4A5. (see attachment)
Just because you can doesn't mean you have to bust Vne in a descent, anticipate the speed buildup in a descent and power back.

Also be mindful of Vno (yellow arc) in the descent when necessary. (156kts indicated for the -10).

Btw, you don't necessarily have to go fast, reducing drag can save you a bunch of fuel.
Click to expand...

Do you have a reference of some of the drag reduction mods you have done on your -10? This is pertinent to my interests :)
 
1001001 said:
Do you have a reference of some of the drag reduction mods you have done on your -10? This is pertinent to my interests :)
Click to expand...

Haven't done any yet, just planning to. Not exactly stock RV-10 though, it has a James cowl and orange peely paint :D
All out at 8500ft it does 178kts. Minus about 0.6kts for static port error at that speed.

Lenny
 
Lenny Iszak said:
Haven't done any yet, just planning to. Not exactly stock RV-10 though, it has a James cowl and orange peely paint :D
All out at 8500ft it does 178kts. Minus about 0.6kts for static port error at that speed.

Lenny
Click to expand...

You also need to account for the difference in props…:rolleyes:
 
Lenny Iszak said:
Haven't done any yet, just planning to. Not exactly stock RV-10 though, it has a James cowl and orange peely paint :D
All out at 8500ft it does 178kts. Minus about 0.6kts for static port error at that speed.

Lenny
Click to expand...
178 KTS? That is mighty ambitious! I say more like a pitot static error. Also many builders have put their air temp probe too close to exhaust stack, which gives a falsely high air temp as well as falsely high TAS. I’m not saying you are pontificating, but I would love for you to verify these two points. If all checks out well, then I sure want to know your secret!
 
Chippster1 said:
178 KTS? That is mighty ambitious! I say more like a pitot static error. Also many builders have put their air temp probe too close to exhaust stack, which gives a falsely high air temp as well as falsely high TAS. I’m not saying you are pontificating, but I would love for you to verify these two points. If all checks out well, then I sure want to know your secret!
Click to expand...

Mine is that fast. Stock with the 2 blade blended airfoil prop and minor under cowl cleanup around the exit.
 
There really are too many variables.

Mine also 9:1 but with a SP cowl, CAI and a hartzell 3 blade. It’s maybe got 285hp
Best power and light I can easily get 178TAS at 8k. But that’s thirsty so I rarely do that. I assume the extra hp roughly offsets the extra blade.

Cruise for me is more like 172 LOP.
At gross you can knock 3-4 kts off both those TAS. Higher is better.

I’ve no doubt Vans numbers are achievable with a stock engine and prop setup. The key is reducing drag. So a plane that is rigged as straight as possible - with as little as possible hanging off it.

Things I did to reduce drag: I have a blade comdat to get rid of the GPS antenna, a blade transponder antenna. A nice tight 1/8 spinner/cowl gap, SP cowl with the nose gear/exhaust fairing under the cowl and a plenum.
It’s hard to quantify what difference each of these make - if any - but I believe it’s definitely a game of incremental gains.

IMG_2655.jpeg

This is 50 ROP. In a hurry with a nice tailwind.
 
Last edited:
Richard Connell said:
There really are too many variables.

Mine also 9:1 but with a SP cowl, CAI and a hartzell 3 blade. It’s maybe got 285hp
Best power and light I can easily get 178TAS at 8k. But that’s thirsty so I rarely do that. I assume the extra hp roughly offsets the extra blade.

Cruise for me is more like 172 LOP.
At gross you can knock 3-4 kts off both those TAS. Higher is better.

I’ve no doubt Vans numbers are achievable with a stock engine and prop setup. The key is reducing drag. So a plane that is rigged as straight as possible - with as little as possible hanging off it.

Things I did to reduce drag: I have a blade comdat to get rid of the GPS antenna, a blade transponder antenna. A nice tight 1/8 spinner/cowl gap, SP cowl with the nose gear/exhaust fairing under the cowl and a plenum.
It’s hard to quantify what difference each of these make - if any - but I believe it’s definitely a game of incremental gains.

View attachment 70611

This is 50 ROP. In a hurry with a nice tailwind.
Click to expand...


Like Rich said, there are truly tons of variables, but I'll give you a completely different setup to reference. Mine is a Standard Cowl, with a custom plenum up top for cooling. The engine is an old 260Hp, with stock compression ratio, but I am running SDS EFI with a fleshed out tune. This is for efficiency, not just speed. Like many, I concentrated on gaps. I also played attention to cooling drag, which for me was Antisplatt cowl flaps (closed in cruise), down by the cowl exit, and closeable wye diverters for heat muff excess air prior to the firewall heat valves pumped down to the cowl exit. I did not remove the steps, I have two com antenna under the rear seats, two transponder blade antenna (one ads recieve) on the belly for and aft, a garmin gps antenna up top just aft the fiberglass top transition, and a top mounted elt about a foot in front of the vert stab. I have standard vans wingtips. A WW hrt375 on the front. I did increase the size of the vans airbox vertically by an inch, so I get the slightest bit more air, but I haven't measured for actual ram increases, it's there, but it's minimal. I should mention that paint have me an extra 3-4 kts even with the extra 50lbs! (A nice surprise.)

AS you see in my Pic, the plane loves to run between 168-175 KTAS LOP with the prop pulled back a bit. I usually run around at 2200rpm below 8500 and 23ish above up to 2500 above 12.5k. ROP gets me around 182 KTAS above 10k, but at an extra 3 or so gallons an hour. I mention this because I've found that this amazing machine is just happy as a clam and very efficient LOP running in the low 170 KTAS region anywhere between 9.7gph to 11 gph, altitude dependent. That nets a nice 15-17 nm/g at around 200 mph! You can go a little faster for a lot less efficiency. I use SFC calculation for leaning, so i don't have exact LOP or ROP temps for you. For mine, altitude wise is happiest between 8 and 13k, below or above are doable but with tradeoffs. And yes my static system was painstakingly dynamically calibrated within 10 ft at 195KIAS, so the measurements should be pretty accurate. Your mileage may vary.

The Pic below shows 175 ktas at 10.5k LOP, rpm 2350, and 10.5 gph at 34 deg F. That was a good day, probably 2 knots faster than "normal." I was solo, 50 lb bag of shot in the back and an overnight bag, so around 2200lbs. Would run about 168 at gross in this configuration.

Roy
 

Attachments

  • Screenshot_20240922_011534_Photos.jpg
    Screenshot_20240922_011534_Photos.jpg
    415.9 KB · Views: 26
You must log in or register to reply here.
Back
Top