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rickbarnes(at)highlandden
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 Posted: Wed Jan 09, 2008 10:15 am Post subject: 2 or 3 blade props |
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Let’s get back to the building of RV10’s. I’ve seen some 10’s with 2 blade and a few with 3 blade props. I’ve heard many differing ideas on which to use. Why have some chosen going with a 2 and some with 3 blades? I know 3’s are sexier and smoother running, but some of us are too old to care about that.
Rick
[quote][b]
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recapen(at)earthlink.net
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| Posted: Wed Jan 09, 2008 10:59 am Post subject: 2 or 3 blade props |
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I'm going with a MT three blade on my 6A along with counterweighted crank as suggested by MT.....for the smoothness - we've added a set of Vetterman exhausts with mufflers for quietness. My wife and I are planning on a lot of cross country flying and don't want to arrive with a body buzz
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carlosh(at)sec-engr.com
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| Posted: Wed Jan 09, 2008 11:25 am Post subject: 2 or 3 blade props |
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Money difference is my first consideration...that said, if you feel to
old to care about it the only benefit I see for you is comfort. The
three blade is smoother therefore less likely to rattle your bones. Just
playing!
Carlos in AZ -7A
Going with a Catto 3-blade until I can afford the C/S prop
Do not archive
Rick Barnes wrote:
| Quote: |
Let’s get back to the building of RV10’s. I’ve seen some 10’s with 2
blade and a few with 3 blade props. I’ve heard many differing ideas on
which to use. Why have some chosen going with a 2 and some with 3
blades? I know 3’s are sexier and smoother running, but some of us are
too old to care about that.
Rick
*
*
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Carlos Hernandez <carlosh(at)sec-engr.com>
Structural Engineers Company
2963 W. Elliot Rd. - Suite 3
Chandler, AZ 85224
Phone: 480.968.8600
Fax: 480.968.8608
www.sec-engr.com
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This email is intended to be reviewed by only the individual or
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its attachments, if any, or the information contained herein is
prohibited. If you havereceived this email in error, please
immediately notify the sender by return email and delete this email
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klwerner(at)comcast.net
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| Posted: Wed Jan 09, 2008 11:55 am Post subject: 2 or 3 blade props |
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Rick
2 Blades are normally more efficient in terms of top speed (less drag), don't know if that is also true about climb thrust though...
3 Blades are normally smoother as the balance out the power pulses better. Theoretically, they can absorb more engine power.
I never had sex with either a 2- or 3 blade prop, so I shouldn't really comment on the "sexier" part between the two 
do not archive
[quote] ---
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AV8ORJWC
Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"
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| Posted: Wed Jan 09, 2008 12:13 pm Post subject: 2 or 3 blade props |
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Back to the Building –
The Negatives are:
1. Additional empty weight, difficulty in removing the lower cowl,
2. Need for more real hp to turn the 3 blades and
3. Greater disc drag
The Positives are, as you have said.
1. Sexy
2. Then comes to mind, more bite to climb to cruise faster than any two blade.
3. And the most important is the smoothing out of the combustion vibration events through the airframe. Six cylinders divided in 720 degrees of blade rotation with three blades is better math than two blades
As the avionics/electronics percentage of the completed kit has gone north of 25% (the old steam gauge rule), as we RV-10 builders embrace EFIS cockpits and show GA what can be done with an Owner Built Kit Aircraft, the avionics percentage tends to get near 50%. Vibration takes its toll on old pilots, cash frugal pilots, metal degradation (which has memory) and obviously the increased need to visit your local Avionics Retailer more frequently to replace or repair the consequence of vibration.
The question remains, would a builder chose to sacrifice 3% faster cruise (with a two blade) to cut their long term avionics investment? And how long were they going to amortize that investment. Climb is an important mission statement in choosing the RV-10 in the Pacific NW.
More than 20% of the builders who have completed and are flying RV-10s, quickly put them on the market for sale. There are many compelling and enlightening reasons as to why.
And NO, it is not due to a design or performance flaw. Had Hartzell not offered the Scimitar two blade, the choice would have been even easier.
Oh and by the way, no 2 blade pilot has publically challenged an equally powered 3 blade to a time to climb, cruise flight over fixed timed interval and fuel restriction to see what the numbers are. Maybe someday this year we will get some color commentary on this great builder challenge. I had hopes that Tim and Vic would duke it out but then I was dreaming at the time.
I’m going 3 Blade and willing to sacrifice 3% cruise in LOP operations (Oh yeh, and drag reduction features can overcome that 3% to level the playing field even more) Borrowing on my retirement fund to put even more into electronics. Been to the avionics shop often enough to know that was one of the reasons to give up Certified GA for Kit Built and to build your own wiring and design your own panel …ala Tim Olson and the RV-10 University site.
Old enough to care –
John Cox - #40600
A&P with IA
And EAA Tech Advisor
Your results may vary
Do not Archive
From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Rick Barnes
Sent: Wednesday, January 09, 2008 8:42 AM
To: rv-list(at)matronics.com
Subject: 2 or 3 blade props
Let’s get back to the building of RV10’s. I’ve seen some 10’s with 2 blade and a few with 3 blade props. I’ve heard many differing ideas on which to use. Why have some chosen going with a 2 and some with 3 blades? I know 3’s are sexier and smoother running, but some of us are too old to care about that.
Rick [quote] [b]
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dougpflyrv(at)AOL.COM
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| Posted: Wed Jan 09, 2008 1:36 pm Post subject: 2 or 3 blade props |
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RICK, I THINK COST IS A BIGGY.
DOUG
DO NOT ARCHIVE
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jhstarn(at)verizon.net
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| Posted: Wed Jan 09, 2008 3:50 pm Post subject: 2 or 3 blade props |
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And then there is a four bladed MT prop. Sexy ? you bet, smoooother than a baby's backside, as close to "hummmmmmm" as I've seen. Harder to remove the lower cowl ? Maybe a tad. Without the upper gear fairings...sameo sameo. Why yes we have flown with 2, 3 and 4 bladed props on this same airplane. We still have the four blade on it, guess which one we like..... HRII IO540 N561FS KABONG
| Quote: | From: "John W. Cox" <johnwcox(at)pacificnw.com>
Date: 2008/01/09 Wed PM 02:05:32 CST
To: rv-list(at)matronics.com
Subject: RE: 2 or 3 blade props
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| Quote: |
Back to the Building –
The Negatives are:
ÂÂÂ
1.      Additional empty  weight,difficulty in removing the lower cowl,
2.      Need for more real hp toturn the 3 blades and
3.      Greater disc drag
ÂÂÂ
The Positives are, as you have said.ÂÂÂ
1.      Sexy
2.      Then comes to mind, morebite to climb to cruise faster than any two blade.
3.      And the most important isthe smoothing out of the combustion vibration events through the airframe. Six cylinders divided in 720 degrees of blade rotation with three blades isbetter math than two blades
ÂÂÂ
As the avionics/electronics percentage ofthe completed kit has gone north of 25% (the old steam gauge rule), as we RV-10builders embrace EFIS cockpits and show GA what can be done with an Owner BuiltKit Aircraft, the avionics percentage tends to get near 50%. Vibrationtakes its toll on old pilots, cash frugal pilots, metal degradation (which hasmemory) and obviously the increased need to visit your local Avionics Retailer morefrequently to replace or repair the consequence of vibration.
ÂÂÂ
The question remains, would a builder choseto sacrifice 3% faster cruise (with a two blade) to cut their long termavionics investment? And how long were they going to amortize thatinvestment. Climb is an important mission statement in choosing the RV-10in the Pacific NW.
ÂÂÂ
More than 20% of the builders who havecompleted and are flying RV-10s, quickly put them on the market for sale.  Thereare many compelling and enlightening reasons as to why.
ÂÂÂ
And NO, it is not due to a design orperformance flaw.  Had Hartzell not offered the Scimitar two blade, thechoice would have been even easier.
ÂÂÂ
Oh and by the way, no 2 blade pilot has publicallychallenged an equally powered 3 blade to a time to climb, cruise flight over fixedtimed interval and fuel restriction to see what the numbers are. Maybesomeday this year we will get some color commentary on this great builderchallenge. I had hopes that Tim and Vic would duke it out but then I wasdreaming at the time.
ÂÂÂ
I’m going 3 Blade and willing tosacrifice 3% cruise in LOP operations (Oh yeh, and drag reduction features canovercome that 3% to level the playing field even more) Borrowing on myretirement  fund to put even more into electronics.  Been to theavionics shop often enough to know that was one of the reasons to give upCertified GA for Kit Built and to build your own wiring and design your ownpanel …ala Tim Olson and the RV-10 University site.
ÂÂÂ
Old enough to care –
John Cox - #40600
A&P with IA
And EAA Tech Advisor
ÂÂÂ
Your results may vary
ÂÂÂ
Do not Archive
ÂÂÂ
From:owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Rick Barnes
Sent: Wednesday, January 09, 20088:42 AM
To: rv-list(at)matronics.com
Subject: 2 or 3 bladeprops
ÂÂÂ
Let’s get back to the buildingof RV10’s. I’ve seen some 10’s with 2 blade and a fewwith 3 blade props. I’ve heard many differing ideas on which touse. Why have some chosen going with a 2 and some with 3 blades? Iknow 3’s are sexier and smoother running, but some of us are too old tocare about that.
ÂÂÂ
Rick  <span
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Mark Phillips in TN
Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN
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| Posted: Wed Jan 09, 2008 9:24 pm Post subject: 2 or 3 blade props |
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In a message dated 01/09/2008 2:16:02 PM Central Standard Time, johnwcox(at)pacificnw.com writes:
| Quote: |
The Negatives are:
1. Additional empty weight, difficulty in removing the lower cowl,
2. Need for more real hp to turn the 3 blades and
3. Greater disc drag |
>>>
Uh, and one more blade to scrub the bugs off of...
From The PossumWorks in TN,
Mark Phillips, RV-6A "Mojo" with a Catto 3-blade nose-job
http://websites.expercraft.com/n51pw/
do not archive
Start the year off right. Easy ways to stay in shape in the new year.
[quote][b]
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_________________
From The PossumWorks... |
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Vanremog(at)aol.com
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| Posted: Wed Jan 09, 2008 9:50 pm Post subject: 2 or 3 blade props |
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In a message dated 1/9/2008 11:04:52 A.M. Pacific Standard Time, recapen(at)earthlink.net writes:
| Quote: | My wife and I are planning on a lot of cross country flying and don't want to arrive with a body buzz
|
==========================
My wife liked the Kitfox for the opposite reason ;o)
-GV
Start the year off right. Easy ways to stay in shape in the new year.
[quote][b]
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gmcjetpilot
Joined: 04 Nov 2006
Posts: 170
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| Posted: Thu Jan 10, 2008 9:45 am Post subject: 2 or 3 blade props |
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The best value, performance, customer support by far is
a BA (blended airfoil) from Vans. A three blade hartzell
is going to be heavy.
Short answer is buy a BA Harzell from Van and be
done.
The other choice is a MT prop. They are fine but will be
significantly slower (6 mph at least, some report 9 mph
or more). It will cost more to buy a MT, repair and
overhaul. It will be way more expensive and time
consuming, because you have to ship it to Germany for
major repair. Also a small thing like a nick or erosion
shield de-bonding, coming loose, means removal of the
prop and shipping it, ie big BUCKS.
A nick on a metal prop like a Hartzell might mean 5
minutes on the ramp with a super fine spoon file to
blend the little nick out.
If you want a WHITE prop get a Hartzell and paint it
white and put pretty stripes on it if you want.
I CANT OVER emphasize how much better Hartzell's
service support will be. There are prop shops all over
the US. You can even fly into Hartzell (Ohio) and they
will repair your prop while you wait or overnight. You
can call Hartzell and talk to an engineer or service
expert in English, any work day of the week. MT? They
speak German and the America centers tend to be
staffed with sales people or technicians, not engineers.
Van had the choice to overhaul a MT on one of his
demo planes. The DOWN time was going to be long (a
few weeks) and cost was going to be the better part of a
new Hartzell. So they overhauled a Hartzell they had
laying around the shop and had it back in a few days for
less than $2k. This was in the RVator, so no hate mail,
its Van saying this.
MT is a good company, but it's a foreign company, a
small boutique prop company. They are getting better,
adding service centers, but chances are you will be far
away from one. Composites and bonding is a wonderful
thing but cost more and not easily ramp repaired.
Last is performance. There is no debate. The fair and
balanced unbiased tests have shown consistently the
MT wood blade props are slower. That is to be
expected. Wood blades are thicker and therefore lose
efficiency at high speed. It's NOT a put down just
aerodynamic facts and reality. Now the plus side is they
are "smoother". Well I have flown metal blades and if
balanced (with a balanced engine) and good engine
mounts metal blades are plenty smooth. There is no
doubt wood has its own natural dampening
characteristics. Also a MT prop will be lighter. Here are
some good links to Prop info.
http://img82.imageshack.us/img82/9791/prop200415me.jpg
http://img82.imageshack.us/img82/4741/prop200559zw.jpg
http://www.romeolima.com/RV8/Prop.htm
http://www.lazy8.net/proptest.htm
Enjoy, its a personal choice but a very expensive one. George
***************
>From: "Rick Barnes" <rickbarnes(at)highlanddental.com (rickbarnes(at)highlanddental.com)>
| Quote: | Subject: 2 or 3 blade props
|
>Let's get back to the building of RV10's. I've seen some 10's with 2 blade
>and a few with 3 blade props. I've heard many differing ideas on which to
>use. Why have some chosen going with a 2 and some with 3 blades? I know
>3's are sexier and smoother running, but some of us are too old to care
>about that. Rick
[quote][b]
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