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  #41  
Old 01-30-2012, 05:36 AM
Alschief Alschief is offline
 
Join Date: Jan 2005
Location: Anderson MO
Posts: 434
Default Airworthiness Concerns

This aircraft is in the making. It is not finished.
The inputs positive and negative are considered with an open mind.
I am aware of the robustness of the firewall attachment points and the unique challenges the design presents.
We will address the long term serviceability of the installation.
It is interesting that while we have almost exactly the same CG as the 85 HP Jabiru installation, I have not seen the concerns mentioned in this thread.
The initial W&B was done with every item to include the seat cushions.
The next time we do a W&B I will include a picture and a list of the equipment.

Please keep the comments, observations and advice coming as I value each and everyone.
__________________
AL & Brenda Smith
RV12, UL Power N495BA Flying
RV6 N495AB Sold
KEOS Neosho, MO
alsmith@olemac.net
alsmith@ulpower.com

Last edited by Alschief : 01-30-2012 at 06:03 AM.
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  #42  
Old 01-30-2012, 06:08 AM
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Geico266 Geico266 is offline
 
Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,862
Default

Keep up the good work Al. Take our comments with the grain of salt. Like Pete said, you are experimenting and put your work up for "review from the peanut gallery". We are gonna let you know about what we see and think, right or wrong. Sort it out, rework where you feel it is needed and move forward. Ultimately, it is your project and you are the decision maker.

Keep us posted.
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RV-7 : In the hangar
RV-10 : In the hangar
RV-12 : Built and sold
RV-44 : 4 place helicopter on order.
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  #43  
Old 01-30-2012, 10:48 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
Default

Quote:
Originally Posted by Alschief View Post
This aircraft is in the making. It is not finished.
The inputs positive and negative are considered with an open mind.
I am aware of the robustness of the firewall attachment points and the unique challenges the design presents.
We will address the long term serviceability of the installation.
It is interesting that while we have almost exactly the same CG as the 85 HP Jabiru installation, I have not seen the concerns mentioned in this thread.
The initial W&B was done with every item to include the seat cushions.
The next time we do a W&B I will include a picture and a list of the equipment.

Please keep the comments, observations and advice coming as I value each and everyone.
One RV-12 build I was involved with has a C.G position of 80.66 inches.
This was built exactly per plans, ready to fly with all fluids and misc. parts/screws installed but no exterior paint. Exterior paint will move the C G a bit further aft because of the influence of paint on the tail.
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  #44  
Old 01-30-2012, 11:30 AM
kmtck kmtck is offline
 
Join Date: Jan 2012
Location: Dallas
Posts: 10
Default CG of Jabiru vs UL

Al, I like what you are doing with the engine but please look at the CG numbers for Jabiru carefully. I am pretty new here...this being my second post on VAF but here is what I found about the Jabiru CG....

The kit plane article has the nosewheel weight as 160 lbs.
Katie has posted a weight of 705 lbs (not painted)

The arm from Vans W&B sheet are,
Nosewheel.... 29.75"
right & left main gear.......93.25"
Assuming the weight on both gear legs is same for now(which it is not), I calculated the empty CG as 78.8" that is outside the 80.49-85.39 in.

I have compiled a list of W&B of various Rv12 from the forum and most have an empty CG of >80"

Maybe Katie can jump in and correct my figures but I have used published numbers to get to the CG and it is well forward in the Jabiru 2200

Now we look at the Jabiru3300 from Oren using the same mount as 2200 but modifying it to accommodate the 3300's addition two cylinders and the CG becomes.......

Sorry about pitching in as a newbee. Everyone here is more knowledgeable than I am and I think the UL is a great engine and will work in the 12 with the right engineering but please e careful with how numbers will play games with you!.... Please be safe!
Rahul
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  #45  
Old 01-30-2012, 03:51 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
Default RV-12 Weight and Balance

Al said,
Quote:
The empty CG is calculated at about 80 inches with all available items less any fuel.
My RV-12 has an empty CG of 80.97" with autopilot, and no paint. The UL engine could be moved aft approximately 5" to move the aircraft CG 1" aft. I based that approximation on calculations done by an Excel spreadsheet. If anyone is interested in downloading this Excel spreadsheet for calculating weight and balance of their RV-12, see this post: http://www.vansairforce.com/communit...88&postcount=4
Joe Gores
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  #46  
Old 01-30-2012, 05:53 PM
Alschief Alschief is offline
 
Join Date: Jan 2005
Location: Anderson MO
Posts: 434
Default Engine Mount Upper Firewall Distance

Quote:
Originally Posted by Alschief View Post
We have done an initial mounting of the engine on a first generation mount.
We will be weighing the RV this week to to verify the installation.
It appears that we may be able to move the engine 6" to 8" closer to the firewall, if so we may be able to adapt the Rotax Supplied Cowl.
We had ordered the materials lasr week.
I just received the materials to construct a modified Mount that
is 5 1/4" shorter than the initially designed mount.
We will report the results when available.

Regards
__________________
AL & Brenda Smith
RV12, UL Power N495BA Flying
RV6 N495AB Sold
KEOS Neosho, MO
alsmith@olemac.net
alsmith@ulpower.com
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  #47  
Old 01-30-2012, 07:23 PM
splitty splitty is offline
 
Join Date: Dec 2007
Location: Hervey Bay Queensland Australia
Posts: 205
Thumbs up UL Mount

Quote:
Originally Posted by Alschief View Post
We had ordered the materials lasr week.
I just received the materials to construct a modified Mount that
is 5 1/4" shorter than the initially designed mount.
We will report the results when available.

Regards
Hi Al a new mount sounds the way to go I was a bit duvious about that Far Forward Engine mounting & COG Questions..! Appreciate all the Working & Investigations you are doing to get this Installation up and running Safely Buddy!
Cheers from Oz.

Last edited by splitty : 01-31-2012 at 05:49 PM.
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  #48  
Old 02-01-2012, 08:15 PM
orenjr orenjr is offline
 
Join Date: Apr 2011
Location: Dayton, VA
Posts: 53
Default Quote from Rahul

Quote (Assuming the weight on both gear legs is same for now(which it is not), I calculated the empty CG as 78.8" that is outside the 80.49-85.39 in.

I have compiled a list of W&B of various Rv12 from the forum and most have an empty CG of >80"

Maybe Katie can jump in and correct my figures but I have used published numbers to get to the CG and it is well forward in the Jabiru 2200

Now we look at the Jabiru3300 from Oren using the same mount as 2200 but modifying it to accommodate the 3300's addition two cylinders and the CG becomes.......
Rahul

Rahul
The 3300 has a shorter engine mount placing the intake close to the firewall. Also the Battery is located in the tail cone to correct the weight and balance.Will wait to do final weight and balance when the cowl is on and it is painted. I also have servos and wheelpants that will also help the W&B.
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  #49  
Old 02-01-2012, 08:24 PM
tim walter tim walter is offline
 
Join Date: Apr 2011
Location: san rafael
Posts: 110
Default

Quote:
Originally Posted by orenjr View Post
Battery is located in the tail cone
won't that require running extra large gauge wires the full length to avoid current loss?
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KDVO
http://rv-12-tim-walter.blogspot.com
kit# 120528
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  #50  
Old 02-01-2012, 10:52 PM
kmtck kmtck is offline
 
Join Date: Jan 2012
Location: Dallas
Posts: 10
Default

Oren, I hope that it works out. I think most of us are eager to find the final answer and everyone wants you to be safe and successful in your experimental.

Just FYI, the Jabiru2200 RV12 in the current form is "NOSE HEAVY" with a 200lb pilot and 5 gallon of fuel (CG is @ 79.9"). It takes 9 gallon of fuel in the tank to get the CG within Van's limit(between 80.49"-85.39"). The CG with 9 gallon fuel & 200 lbs pilot is 80.6".

You can run the numbers yourself(& most likely have run them) but to me the jabiru 2200 is way too nose heavy. Imagine only flying with 11 gallons of fuel(including reserve) to be safe
Please be safe!

Quote:
Originally Posted by orenjr View Post
Quote

Rahul
The 3300 has a shorter engine mount placing the intake close to the firewall. Also the Battery is located in the tail cone to correct the weight and balance.Will wait to do final weight and balance when the cowl is on and it is painted. I also have servos and wheelpants that will also help the W&B.
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