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02-11-2009, 06:41 AM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by C-GRVT
In deciding on a prop, how important is weight as a factor? A Hartzell is clearly a heavy choice compared to a Whirlwind. At every opportunity, Van suggests light is better. Effort is made to reduce airframe weight at every opportunity - a few grams here and there, lightening hole in the battery box, corners shaved off brake pedal angles, lightweight seats......
Why not the same concern about 20 lbs or so of weight in the prop? Why isn't that a huge deal, or is it? Some posters refer to different handling characteristics, but never having flown as RV, light or heavy, is that just an observation, or a criticism of the flying qualities of a heavy prop RV? I realize this is perhaps a subjective thing, but thoughts of those that have experienced both would be valuable.
I notice as well that Van's is now (wihout any fanfare) offering a Hartzell composite prop for the O-360. Anyone have any thoughts about that prop? I assume that it is lighter in weight (definitely heavier in the wallet) than the Hartzell aluminum prop.
Bill Brooks
Ottawa, Canada
RV-6A in progress
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I've flown a lighter weight RV6A that had an 0320 & a Sensitch (spelling?) fixed pitch prop. Mine has the 0360 & Hartzell constant speed. You'd really have to think hard to observe any real differences in handling while in flight.
The big difference, is that mine goes like a bat out of h*** on takeoff & climb, and easily slows down for landing. I'll take the C/S anytime, and the original owner of the F/P plane...............always wanted a C/S too. His engine just wouldn't allow for it, as it didn't have the hollow crank.
Thinking "light" is one thing. But my plane performs more like a mini-fighter, than a gentle Cub. I like it!
L.Adamson --- RV6A
P.S. --- Landing speeds in the 6A are about 10 mph over the longer winged 9 models.
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02-11-2009, 07:21 AM
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Join Date: Jan 2005
Location: Houston, Texas
Posts: 469
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Best of both worlds
There you go - WW 200RV - lighter weight, constant speed, and doesn't give anything on the top end. I've already sent in my deposit on the group buy. 
__________________
William Slaughter
Houston, TX
RV-8QB
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02-11-2009, 08:21 AM
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Join Date: Feb 2005
Location: Minneapolis
Posts: 2,473
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Yes...but, here's the deal.
Most TW RV's have a tendency towards being tail heavy - especially with a 320/360 and a FP prop. So, C/S hartzell will put most of the TD's right in the CG sweet spot, and the WW would leave them well aft.
It's the opposite story with the Nosedraggers - where the WW would be a good thing.
Not debating anything, just saying that losing a lot of weight on the nose of most TD's isn't necessarily what you want...within reason.
Cheers,
Stein
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02-11-2009, 08:46 AM
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Join Date: Aug 2005
Location: OKC, OK
Posts: 687
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IMHO, propeller weight matters more with the tandem RV's than with the side by side models. This is simply a function of how the airplane was designed in the first place.
Consider the tandem models must balance even with a passenger in the back. That means the RV8 has to be pretty far forward in the CG envelope when the airplane is solo. In fact, the RV8 balances near the forward CG limit when solo and equipped with a CS prop. When you add the back seat passenger, and some baggage, the airplane tends to run near its aft limit. From a design standpoint, the side by side models balance more easily simply because they don't have the constraint of trying to balance with a back seat pax and a baggage area thats 46 inches behind the pilot.
In the real world, the RV8's tend to run a bit too nose heavy. As an example, an RV8 with an IO360 angle valve engine, a Hartzell CS prop, the battery up front (per plans), full fuel and solo will balance at about 27.5" aft of datum. And the forward limit is 27" aft of datum, so in this case we're only 1/2" from the forward limit. Put a 180# passenger in this same airplane, and 50# of baggage in the back and the CG moves to 32.9" which is only 1.9" from the aft limit at 34.8". Now you can see why the tandem RV's must run nose heavy when solo.
Take a look at what the builders here are doing to alleviate this. We're putting our batteries in the back (many of us are anyway). Although the airplane will fly OK with a heavy nose, its much nicer when the CG isn't at the forward edge of the envelope.
My opinion on flying qualities: I like a well balanced airplane. I also like to "boom and zoom", but those two desires tend to fight against each other. Getting a well balanced airplane means keeping the nose light (I'm building an 8); "boom and zoom" calls for a CS prop. (I also like the efficiency of the CS propeller in cruise) And finally, for what ever reason, more folks tend to build the 8 as a tail dragger and the 7 as a nose dragger. And as Stein pointed out, that nose gear does weigh more than the tail wheel it replaces.
With those things in mind, IMHO you get the best of overall package with a light weight CS prop and as much horsepower as you can stuff under the hood.
Edit: I'm putting in my deposit on the WW group buy today.
__________________
?The important thing in aeroplanes is that they shall be speedy.?
- Baron Manfred von Richthofen
RV8 under construction
RV4 - Sold
United B777 FO, Chicago
Aero Engineer
RV8
Last edited by Bill Wightman : 02-11-2009 at 09:34 AM.
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02-11-2009, 09:33 AM
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Join Date: Jan 2005
Location: Houston, Texas
Posts: 469
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Quote:
Originally Posted by SteinAir
Yes...but, here's the deal.
Most TW RV's have a tendency towards being tail heavy - especially with a 320/360 and a FP prop.
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Most TW side-by-side RV's might have that tendency, but the 8's, not so much. Probably should have noted that distinction in my prior post. Having a modified parallel valve motor, I'm locked in to the composite prop in any case, and with the group buy in progress, I do have an ulterior motive. 
__________________
William Slaughter
Houston, TX
RV-8QB
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02-11-2009, 10:04 AM
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Join Date: Aug 2005
Location: OKC, OK
Posts: 687
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CS propeller in cruise (Vans comments)
After reading through this thread, there is a major point that I don't think has been pointed out: The CS propeller has an advantage in cruise flight that cannot be had with a FP prop.
The explanation is for this comes directly from the RV8 builders manual, page 11-8 (thank God for OCR software):
" Cruise: This is the flight condition at which we feel the CS prop offers the greatest advantage to an RV. Most Rvs will spend the majority of their flight time in cruise, so any benefit gained will be of greater value. Though the FP prop is operating at its best in the cruise condition, it is still a compromise. But, there are a wide variety of conditions which occur under the general heading of "Cruise"; anything from full throttle & RPM (at altitude), to just enough power to maintain minimum power flight. "Rated Cruise Speed" for production aircraft is quoted for conditions under which the maximum permissible continuous speed can be achieved. This combination produces about 75% of maximum rated power. Under this condition, the CS prop will offer little advantage over the FP prop. other than what little it may gain from better blade efficiency.
The CS prop offers its main cruise advantage under reduced power cruise conditions. Engines operate at peak efficiency when the throttle is full open. This is because the air flow control vane in the carb or injector throttle body is completely open and offering the least resistance to airflow. This reduces what is known as "pumping losses" within the engine. There are two primary means (from the pilots vantage point) of reducing power output of an engine. One is to reduce the RPM of the engine and the other is to reduce the manifold pressure. With a fixed pitch prop, the only means of reducing RPM is to retard the throttle setting. In so doing, the control vane (butterfly) in the carb partially closes, manifold pressure is reduced, and engine efficiency drops. With a variable pitch (CS) prop, the RPM can be controlled through adjusting the blade angle, and thus the propeller load on the engine. The throttle can be left full open (in its most efficient position) and the power output can be reduced by lowering the RPM. This reduced RPM, full throttle condition achieves both reduced engine friction because of the lower RPM,
and minimum pumping losses. Fuel efficiency will be improved, but speeds will drop because less than full cruise power is being used. Above we mentioned 8,000 ft. as the optimum cruise altitude. This is because it s the lowest altitude at which an engine will develop no more than 75% power at rated RPM. With a variable pitch prop, selecting low ?RPM can cause the engine power output to be 75% or less at altitudes of less than 8,000', making it possible to utilize the efficiency of a continuous full throttle opening
at altitudes well below 8,000'. Just leave the throttle wide open and pull the RPM back to a number which, according to the Lycoming manual, produces 75% power or less. "
If you FP flyers get steamed from reading this, you can kindly direct your flaming arrows to Vans Aircraft.... 
__________________
?The important thing in aeroplanes is that they shall be speedy.?
- Baron Manfred von Richthofen
RV8 under construction
RV4 - Sold
United B777 FO, Chicago
Aero Engineer
RV8
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02-11-2009, 10:29 AM
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Join Date: Jan 2005
Location: Houston, Texas
Posts: 469
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Quote:
Originally Posted by Bill Wightman
If you FP flyers get steamed from reading this, you can kindly direct your flaming arrows to Vans Aircraft.... 
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As Joe Friday might have said, "Just the facts, ma'am". 
__________________
William Slaughter
Houston, TX
RV-8QB
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02-16-2009, 12:58 PM
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Join Date: Jan 2006
Location: Belgium
Posts: 645
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Paid deposit on group buy today! Let us know if you did also!
Today I sent in my order for the 200RV prop group buy. Strange, but now I am told that I am #12 paying his deposit, as for last week there were already 13 sold??
I suggest everybody who has already made a deposit, or is going to, let us know on this thread, to motivate others and allow us to keep track.
BTW I was also told that there is another 6 "on the fence", so only those and two more necessary to get to 20+ and we are at $ 7.300,-
Regards,
Tonny.
__________________
"Pilottonny"
Tonny Tromp
Lanaken, Belgium (EU)
RV9A, Registration: PH-VAN
ECI-Titan IOX-320 with dual EI, turning a Whirlwind 200RV CS prop.
Sold
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02-16-2009, 10:08 PM
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Join Date: Oct 2007
Location: Mission Viejo, CA
Posts: 212
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One more 200RV sold
I spoke with Kevin @ American Propeller today and placed my order for a Whirlwind 200RV. He told me a few things about the group buy that I didn't recall reading in any of the threads so I thought I'd share them.
1. Because the warranty starts when it is shipped, they can hold off shipping it until as late as December but the balance has to be paid in full by April 6th when the group buy closes.
2. If you buy the 200RV you can also get the PCU5000 governor for $1150, a $200 discount.
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02-17-2009, 09:14 AM
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Join Date: Aug 2005
Location: OKC, OK
Posts: 687
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Group Buy: More info
I put the money down a few days ago for the GB.
In the call with Bob, he felt pretty sure that we'd reach the 30+ goal needed to reach the minimum price floor. He didn't share how many they had in the buy at that time.
Also having relevance, Bob said they'd put deliveries into three groups:
1) Need it now. Plane will be ready to fly, minus prop.
2) Need it soon. Plane will be ready to fly in a few months.
3) Can wait. Participating in GB to get the price discount.
And, finally I asked about custom paint. Bob told me that Whirlwind ships the props to American Propeller in an unfinished state. American does all the finishing. So they can do a custom paint job if you want. I didn't ask about details of just exactly how they'd do the paint job - but - they can do it. Bob didn't make any mention of extra cost but that doesn't mean its free.
By the way. This group buy thing is REALLY great. I'm grateful to Doug Reeves for putting it together. I will save $695.00 as a result. This would never have happened without VAF and American Propeller working together for our benefit. As a thank-you to Doug, I am going to return 10% of my savings to VAF. Call it the VAF Tithe
Thanks Doug!
__________________
?The important thing in aeroplanes is that they shall be speedy.?
- Baron Manfred von Richthofen
RV8 under construction
RV4 - Sold
United B777 FO, Chicago
Aero Engineer
RV8
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