VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 11-09-2021, 04:19 PM
claycookiemonster's Avatar
claycookiemonster claycookiemonster is offline
 
Join Date: Oct 2007
Location: Midway, UT
Posts: 461
Default Prop extensions?

Both the Showplanes and James cowls require a prop extension. I've been going back and forth between Aerosport Power and Whirlwind to make sure everyone is ok with this. Now, Whirlwind is balking a bit at mounting their new 3-blade prop on an extension. I contacted the manufacturer of the extension, Sabre Manufacturing, and they said they make a 3" extension used in Red Bull races with 60lb props pulling 10 G's. They don't think this is any problem for me.

I understand manufacturers being hesitant to endorse ANYTHING GOES, but is this a real road block, or just the reality of Experimental airplanes and new combinations? I'm not EVER going to do anything close to the Red Bull guys, so I can talk myself into this. On the other hand, I have no desire to really approach the edge of safety and wisdom.

Anyone with prop extension experience have any perspective on this?
__________________
Clay "Cookiemonster" Cook
USAF: T-38, F-111F
American Airlines: 727, MD80, 757, 767, 737
RV8 #81751 project sold
RV8 #81651 project acquired
https://theonceandfutureflyer.wordpress.com/
Donations up to date thru December 2015

"...serenity...courage...and wisdom..."
Reply With Quote
  #2  
Old 11-09-2021, 04:23 PM
00Dan 00Dan is online now
 
Join Date: Nov 2016
Location: Atlanta, GA
Posts: 274
Default

Donít the current Vanís cowls also require an extension? I know my old fixed pitched Vanís cowl on my -4 requires a 4Ē extension, and I think the CS cowl required a 2.25Ē extension.
Reply With Quote
  #3  
Old 11-09-2021, 04:40 PM
BillL's Avatar
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,739
Default

You should define what specifications are wanted for an extension. The cranks are the real issue. Are you building a 9?
__________________
Bill
RV-7
Reply With Quote
  #4  
Old 11-09-2021, 07:13 PM
claycookiemonster's Avatar
claycookiemonster claycookiemonster is offline
 
Join Date: Oct 2007
Location: Midway, UT
Posts: 461
Default

Building a taildragger 8. Trying to make sure everyone is on board with the engine room before I make serious plans. Either the James or Showplane cowls require a prop extension, though they don't specify how long of an extension. I believe they need 2.5"

Yes, I understand the stresses in this. I do not want to underestimate them.

Just trying to understand the cautious reply from Whirlwind, which was not actually a, "It's forbidden!" Aerosport power is fine with this. So, their bearings must be up to it.
__________________
Clay "Cookiemonster" Cook
USAF: T-38, F-111F
American Airlines: 727, MD80, 757, 767, 737
RV8 #81751 project sold
RV8 #81651 project acquired
https://theonceandfutureflyer.wordpress.com/
Donations up to date thru December 2015

"...serenity...courage...and wisdom..."
Reply With Quote
  #5  
Old 11-09-2021, 07:21 PM
KatanaPilot KatanaPilot is offline
 
Join Date: Feb 2015
Location: Locust Grove, GA
Posts: 852
Default

Have you considered the extended hub Hartzell props? I believe Team AeroDynamix has used them in the past. You could reach out to them for their opinions.
__________________
Krea Ellis

Locust Grove, GA
DA20-A1 "Princess Amelia" - gone home to Amelia Island
RV-7A Phase 2 (Honored to be Van's "Miss July" 2021)
RV-10ER officially an airplane as of 4/5/22!
Reply With Quote
  #6  
Old 11-10-2021, 07:18 AM
rmarshall234 rmarshall234 is offline
 
Join Date: Jun 2008
Location: San Diego, CA
Posts: 400
Default

The prop extension we used on Miss B Haven - the Formula One Racer at Reno - was comically long. Like 12 inches. A different application for sure, and a light weight CF prop at the end, but the biggest challenge was balancing the prop well enough since it was so far out there in space. I tried to post a photo but the size is too large and don't want to spend the time figuring out how to shrink it. PM me an email address if you want to see something that should put your concerns to rest.
Reply With Quote
  #7  
Old 11-10-2021, 10:15 AM
BillL's Avatar
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,739
Exclamation

Quote:
Originally Posted by claycookiemonster View Post
Building a taildragger 8. Trying to make sure everyone is on board with the engine room before I make serious plans. Either the James or Showplane cowls require a prop extension, though they don't specify how long of an extension. I believe they need 2.5"

Yes, I understand the stresses in this. I do not want to underestimate them.

Just trying to understand the cautious reply from Whirlwind, which was not actually a, "It's forbidden!" Aerosport power is fine with this. So, their bearings must be up to it.
Check your sources - - James recommended 2.25"

If you understand the stresses, what do bearings have to do with it?

Aerobatic cranks have the same bearings, just a thicker flange.

You had better assume that your aerobatic limit is 4 G's, maybe 5. Quantify the stresses.

Krea, I asked Hartzell long ago about that hub for aero and they said 4 G. i.e. it was the same as standard with a saber 2.5"extension. That was 6-7 yrs ago and may have changed.

Through private conversations, Hartzell and calculations, I was convinced my M1B, Hartzell composite and 2.5" Saber was good for the a "mild aerobatic" range. Any rapid axis change at high RPM is forbidden. Today I would use the extended hub. This is not an endorsement . . YMMV

Just keep in mind that Earl Findlay endorsed an RV9A for for 230 MPH airspeed (30 mph higher than Vans limit -lesson: be careful trusting your life to critical information provided without corroboration)
__________________
Bill
RV-7

Last edited by BillL : 11-10-2021 at 04:06 PM.
Reply With Quote
  #8  
Old 11-10-2021, 12:18 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
Posts: 2,441
Default

Quote:
Originally Posted by BillL View Post

Just keep in mind that Earl Findlay endorsed an RV9A for for 230 MPH airspeed.
For those who dont follow these forums,, this is a joke. RV9a is not approved for this high of speed.
__________________
John S

WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

Dues paid 2022, worth every penny

RV9A- Status:
98% done, 2% left to go
Structure done (less gear)
Electrical/Panel done
Firewall Forward 95% done less baffles and airbox
Fiberglass 95%
www.pilotjohnsrv9.blogspot.com
Reply With Quote
  #9  
Old 11-12-2021, 10:44 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,917
Default

Quote:
Originally Posted by 00Dan View Post
Donít the current Vanís cowls also require an extension? I know my old fixed pitched Vanís cowl on my -4 requires a 4Ē extension, and I think the CS cowl required a 2.25Ē extension.
The standard kit supplied cowls are designed for use with the Hartzell compact hub propellers.
When a fixed pitch propeller is used instead, a 2.25" extension (actually spacer) is required.
Prior to developing a cowl designed for use with the Hartzell compact hub prop., the cowls required a 4" spacer be used with a fixed pitch prop, or the use of the extended hub version (approx. 1.75" longer than the compact hub) of the Hartzell propeller.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop
FAA/DAR
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #10  
Old 06-06-2022, 07:42 PM
AlphaCharlieBravo AlphaCharlieBravo is offline
 
Join Date: Nov 2008
Location: Olympia,WA
Posts: 243
Default Saber Manufacturing

Just received my 4" Saber Prop Extension for my extended James Cowl and Lycoming A1A engine and it is a work of art. Beautiful!

Going with a three blade Catto prop. Spoke to Nicole the other day and getting that order in this week.

Arnie
__________________
Arnie Barros
VAF #1401
(N89269) reserved
"Seek to understand before trying to be understood"
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:51 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.