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  #31  
Old 02-18-2017, 01:34 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
and the increased fuel burn of the RV-14 over the RV-7, the RV-7 shines as the better value
I guess higher fuel burn is going to be a myth that the IO-390 will never be able to shake.....

See my previous post.... fuel burn isn't necessarily any higher than for an angle valve 200HP.
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RV-6A (aka "Junkyard Special ")
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  #32  
Old 02-19-2017, 10:32 AM
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Default Apples to apples

Scott,

For the taildraggers, Van's #'s with the same engine/altitude/power (and presumably fuel flow) shows the -7 is 10mph faster. Has that matched your experience? Have you guys tested an IO-360 powered -14A yet?

Fuel burn is really a cost issue anyway, so not all that applicable to this thread .

That said, the -14 is an incredible aircraft. Cost not an issue, I'd go with the -14. Just playing devil's advocate here.

But all things equal, the -7 is a better performing aircraft.

Last edited by Chattin35 : 02-19-2017 at 11:30 AM. Reason: Typo
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  #33  
Old 02-19-2017, 11:20 AM
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Quote:
Originally Posted by rvbuilder2002 View Post
I guess higher fuel burn is going to be a myth that the IO-390 will never be able to shake.....

See my previous post.... fuel burn isn't necessarily any higher than for an angle valve 200HP.
Not to beat a dead horse - but I offer an RV-7 with a 180hp parallel Lycoming will burn less fuel than an RV-14 at the same cruise speed.

The single data point I'm using is talking with a new RV-14A builder that is now about 30 hours into his 40 hour test period. He has an IO-390 with CS prop and is burning 12 gph (ROP) at 24" and 2400 RPM. This is about the same fuel burn I had in the RV-10 (LOP) at the same speed. Perhaps when he starts his LOP test period fuel burn performance will improve. Shoot fire - for the same speed I was burning 7.8gph in the RV-8A (180hp CS prop).

So eyes wide open - the RV-14 is a very nice plane, has a boatload of room, handles like an RV and does everything you want it to do. It will, compared to any RV other than the RV-10, cost more to build and operate. As I said before for not much more money (but a lot more work) you can have an RV-10 (in my opinion the best value in an RV).

Carl
Working the RV-8 slow build gas tanks
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  #34  
Old 02-19-2017, 01:07 PM
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Quote:
Originally Posted by Carl Froehlich View Post
Not to beat a dead horse - but I offer an RV-7 with a 180hp parallel Lycoming will burn less fuel than an RV-14 at the same cruise speed.

The single data point I'm using is talking with a new RV-14A builder that is now about 30 hours into his 40 hour test period. He has an IO-390 with CS prop and is burning 12 gph (ROP) at 24" and 2400 RPM. This is about the same fuel burn I had in the RV-10 (LOP) at the same speed. Perhaps when he starts his LOP test period fuel burn performance will improve. Shoot fire - for the same speed I was burning 7.8gph in the RV-8A (180hp CS prop).

So eyes wide open - the RV-14 is a very nice plane, has a boatload of room, handles like an RV and does everything you want it to do. It will, compared to any RV other than the RV-10, cost more to build and operate. As I said before for not much more money (but a lot more work) you can have an RV-10 (in my opinion the best value in an RV).

Carl
Working the RV-8 slow build gas tanks
Carl,
It is common mistake here in the forums, but quoting performance comparisons at just one specific altitude is not going to be valid for all altitudes when the two airplanes being compared are of different configurations (totally different airfoil and higher aspect ration on the RV-14). It is false to assume that configurations the delta is linear with altitude change.

Example - An O-320/CS RV-9A will run away from an O-320/CS RV-7A at high altitude (12,500) with both at WOT and same RPM. The RV-7A will likely be faster down low. So it is not valid to talk in generalities when talking about performance. If you want to say such and such model will be faster leaned to best power at such and such altitude fine, but it wont necessarily be correct in all situations.
Also, making comparisons to a brand new airplane is not a valid benchmark in my opinion. Particularly comparing it to an RV-8A. If there wasn't an advantage to the 8A, everyone would/should be telling you that there is something wrong with your airplane. With the airplane so new to the owner and being broken in, it is fully possible that the rich of peak power setting was no where near best power, so random details are not of much value for comparison purposes.

I have already posted in this thread (and many other threads) what I have personally gotten for performance in the RV-14's traveling cross country.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #35  
Old 02-19-2017, 01:18 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Chattin35 View Post
Scott,

For the taildraggers, Van's #'s with the same engine/altitude/power (and presumably fuel flow) shows the -7 is 10mph faster. Has that matched your experience? Have you guys tested an IO-360 powered -14A yet?

Fuel burn is really a cost issue anyway, so not all that applicable to this thread .

That said, the -14 is an incredible aircraft. Cost not an issue, I'd go with the -14. Just playing devil's advocate here.

But all things equal, the -7 is a better performing aircraft.
See my post # 34......

At 8K feet, the perf. #'s posted on the web site are valid comparisons between a 7 and a 14. As the airplanes go higher than 8K, the differences begin to shrink (though the 7 will always be a bit faster... laws of physics.....)

We only have a tail dragger with the IO-360 (200HP), and the older version (non-blended airfoil prop.).
The trigear has the IO-390 (210HP) and the blended airfoil prop.
The two airplanes are nearly dead equal in speed if the same power setting is used on both (the tail dragger about 2 MPH faster) so a tail dragger with an IO-390 and blended airfoil prop, should be even faster.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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