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  #11  
Old 10-13-2008, 04:32 AM
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carguy614 carguy614 is offline
 
Join Date: Aug 2007
Location: Shallotte NC
Posts: 594
Default Think light

Mel is right. My 9A is chubby at 1141. Having flown a lighter ship, I can tell you the difference is astounding in the way the lighter plane flys and handles. One thing I am not sorry about are the seats. Get comfortable at any weight penalty. Install only the gadgets that you really need, and keep your primer coats light on the inner structure. My next plane will be a RV9, and I will pay way more attention to how much it will weigh when complete. That being said, I love my plane and will make no effort to lighten it up.
The "grin" is weightless!!

Regards...Chris
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Chris Schmitt
Shallotte, NC
RV9A 90970 N614RV
Sold to nice folks in Texas and badly missed.
RV9 in progress
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  #12  
Old 10-13-2008, 05:53 AM
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Rick6a Rick6a is offline
 
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Location: Lake St. Louis, MO.
Posts: 2,346
Default Weighty Subject

The thing about weight claims: I am naturally suspicious of empty weight claims because there can be huge errors in weighing equipment. For instance Ruggles scales...cheap and widely available are little more than bathroom scales modified with arms to multiply the indicated weight. So inaccurate, I had to pull my -6A on and off Ruggles scales 10 separate times.....each event offering a different reading. The lowest indicated weight came in at 1065 pounds! In the end, I simply averaged numbers that fluctuated all over the place and finally settled upon 1098 for W&B purposes.

Because mine was not the only sour experience with those scales, our EAA Chapter 32 voted for and invested in a much better alternative. This time around, I used our digital race car scales to weigh the -8 project with and they seem to be far more accurate. I could not get the indicated weight to vary by so much as a pound.


Still, the most reliable numbers would be had by using certified scales and I seriously doubt most RV builders have used certified scales to establish the true empty weight.
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Rick Galati
RV6A N307R"Darla!"
RV-8 N308R "LuLu"
EAA Technical Counselor

Last edited by Rick6a : 10-13-2008 at 02:22 PM.
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  #13  
Old 10-13-2008, 06:59 AM
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Mel Mel is offline
 
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Location: Dallas area
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Quote:
Originally Posted by Rick6a View Post
The thing about weight claims: I am naturally suspicious of empty weight claims because there can be huge errors in weighing equipment.
Still, the most reliable numbers would be had by using certified scales and I seriously doubt most RV builders have used certified scales to establish the true empty weight with.
BTW, My 1031 lbs. is with paint and on certified scales.
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Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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  #14  
Old 10-13-2008, 07:37 AM
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L.Adamson L.Adamson is offline
 
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Location: KSLC
Posts: 4,021
Default C/S versus fixed -- weight

Many of the "lighter" planes, use a fixed pitch prop. Personally, I wouldn't want one if it was given to me. That's an opinion shared by myself and apparently "all" the other C/S RV flyers that operate out of our 4600' msl airport.

And yes, some composite C/S props are lighter than my Hartzell, but at a higher cost.

L.Adamson -- RV6A
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  #15  
Old 10-13-2008, 08:12 AM
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Mel Mel is offline
 
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Location: Dallas area
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Default Fixed pitch is fine.

If you want a constant speed prop, great. Then by all means get one. They are very nice. But don't think you HAVE to have one. There are literally thousands of RVs flying with fixed pitch. I have flown my -6 out of Leadville, CO (9926' msl) with a tired 150 hp engine and a wood F/P prop in the summer with no problems.
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Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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  #16  
Old 10-13-2008, 03:37 PM
hohocc hohocc is offline
 
Join Date: Sep 2008
Location: Christchurch, New Zealand
Posts: 187
Default

Here in New Zealand there are very few airfields I'd expect to use that are higher than about 1500'amsl, so in my opinion at least an 0320 with fixed pitch wood prop (or possibly fixed metal if it helped the c of g situation) is the way I expect to go at this VERY early stage. In a few years I may feel differently, but in all the flying I've done up to now the most enjoyable has been in simple aeroplanes like cubs and tiger moths which are probably basic to the point of being archaic!
Keep the posts coming, I'm lapping them up!
Cheers, Craig Clapham
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  #17  
Old 10-13-2008, 05:56 PM
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L.Adamson L.Adamson is offline
 
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Quote:
Originally Posted by Mel View Post
If you want a constant speed prop, great. Then by all means get one. They are very nice. But don't think you HAVE to have one.
Oh..............I HAVE to have one. I'd have gaven up numerous items before doing away with the C/S! Besides, nearly every plane I've flown for the last 15 years has had one...

L.Adamson
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  #18  
Old 10-13-2008, 08:14 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by L.Adamson View Post
Many of the "lighter" planes, use a fixed pitch prop. Personally, I wouldn't want one if it was given to me. That's an opinion shared by myself and apparently "all" the other C/S RV flyers that operate out of our 4600' msl airport.

And yes, some composite C/S props are lighter than my Hartzell, but at a higher cost.

L.Adamson -- RV6A
It's true that a fixed pitch prop. is lighter than a constant speed but not by as much as you might expect. It is a big solid hunk of aluminum and it uses a steel prop extension and six long 1/2 bolts (assuming an O-360).
I don't know the exact amount but I believe it is inside of 10 pounds. The other factors are no prop. gov., control cable, or gov. drive (if it has been removed).
I think the weight difference between a fixed pitch and constant speed is no more than about 15 lbs total.
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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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  #19  
Old 10-13-2008, 08:40 PM
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N941WR N941WR is offline
 
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Location: SC
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Quote:
Originally Posted by rvbuilder2002 View Post
...
I think the weight difference between a fixed pitch and constant speed is no more than about 15 lbs total.
Unless you use a composite (wood) prop. My Catto is 9 lbs vs. 40 lbs for a metal FP prop.

The numbers presented on the Van's web site are a good tell. The RV-9 numbers are all for FP prop whereas the RV-7 numbers are all for CS props.

The GW climb for a FP O-320 RV-9 is 1400 FPM and the GW climb for a CS O-320 RV-7 is 1400 FPM. (1650 FPM / 180 HP & 1900 FPM / 200 HP)

When you look at the GW cruise speeds for the two different planes, again the -9 has a FP prop and the -7 has a CS prop and both having O-320's, it makes me wonder why anyone would want a CS prop.

RV-7: 192 MPH
RV-9: 189 MPH

Other than doing acro or formation work, I have to wonder if the CS prop is worth the cost, maintenance, and weight.

Before anyone jumps in how their 180 HP RV-6/7/8 trounces 160 HP RV-9's, the differences is more the engine than the airframe or prop.

The question comes back to, how much climb rate is good enough for your mission? A Cessna climbs at maybe 750 FPM at GW, so going up at 1400 FPM with a "low powered" FP RV is just outstanding!
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RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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  #20  
Old 10-13-2008, 08:56 PM
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L.Adamson L.Adamson is offline
 
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Location: KSLC
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Quote:
Originally Posted by N941WR View Post
When you look at the GW cruise speeds for the two different planes, again the -9 has a FP prop and the -7 has a CS prop and both having O-320's, it makes me wonder why anyone would want a CS prop.
Perhaps it's where we live and fly. See included pic. We fly down this canyon, and up it too! If you think a C/S doesn't make a difference, believe me.... it does!

I know of NO ONE around here, who has owned an RV with a C/S................that would be willing to go back to a fixed pitch. We discuss this fact quite regularly, including EAA chapter meetings, when the question comes up. Naturally, I scream and yell, until the prospective prop buyer is convinced!



L.Adamson -- RV6A
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