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  #31  
Old 08-16-2016, 01:52 AM
Aussieflyer Aussieflyer is offline
 
Join Date: Jan 2015
Location: Redcliffe, Queensland, Australia
Posts: 44
Smile 14A Weight & Balance done

Just had my weight and balance done. Aircraft is painted, instruments (G3X @ 2, GTN 650, TCW backup battery, mini Ipad, 2 x garmin AP Servo's) in, seats carpets and fuselage linings in. Empty weight 1288.6 lbs Arm is 80.9 inches. FYI
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  #32  
Old 09-13-2016, 10:30 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,143
Default RV-14A W&B

This is a repeat of another post as was requested.

This RV-14A has a new from Van's IO-390 engine and a custom composite two blade CS prop (uses a Hartzell hub). The plane is built to plans, has a full dual EFIS IFR panel, and not yet painted (I suspect the paint will aggravate the nose light issue as the majority of the paint weight will be aft of CG). Seven qts of oil in the sump. The one battery (PC-680) is mounted on the firewall per the plans. As I previously mentioned, I suspect we'll end up putting another PC-680 battery on the firewall to help the CG issue and to address the woefully inadequate battery reserve offered by the single battery.

Here are the numbers. Plug them into the Van's W&B spreadsheet:
Right wheel: 434.5
Left wheel: 425.5
Nose wheel: 352.0

Here is the problem. At full 2050 pound gross (219 pound pilot and passenger, 100 pounds of baggage and full fuel) the CG is at 89.6" (aft limit is 88.24").

Carl
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  #33  
Old 09-13-2016, 12:07 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,065
Default

Quote:
Originally Posted by Carl Froehlich View Post
This is a repeat of another post as was requested.

This RV-14A has a new from Van's IO-390 engine and a custom composite two blade CS prop (uses a Hartzell hub). The plane is built to plans, has a full dual EFIS IFR panel, and not yet painted (I suspect the paint will aggravate the nose light issue as the majority of the paint weight will be aft of CG). Seven qts of oil in the sump. The one battery (PC-680) is mounted on the firewall per the plans. As I previously mentioned, I suspect we'll end up putting another PC-680 battery on the firewall to help the CG issue and to address the woefully inadequate battery reserve offered by the single battery.

Here are the numbers. Plug them into the Van's W&B spreadsheet:
Right wheel: 434.5
Left wheel: 425.5
Nose wheel: 352.0

Here is the problem. At full 2050 pound gross (219 pound pilot and passenger, 100 pounds of baggage and full fuel) the CG is at 89.6" (aft limit is 88.24").

Carl
Carl,
You are probably already aware, but the problem is even bigger than you describe.
As fuel is burned off the CG moves even farther aft, so the worst case situation for C.G. position will always be at minimum fuel.
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RV-6A (aka "Junkyard Special ")
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  #34  
Old 09-13-2016, 01:32 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,143
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Originally Posted by rvbuilder2002 View Post
Carl,
You are probably already aware, but the problem is even bigger than you describe.
As fuel is burned off the CG moves even farther aft, so the worst case situation for C.G. position will always be at minimum fuel.
Yep - so until we add some weight forward we'll limit the baggage. I looked at adding a harmonic balancer to offset the light prop, but that would be "no value added other than CG" weight so we're back to the second PC-680 on the firewall option.

Carl
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  #35  
Old 09-13-2016, 05:42 PM
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czechsix czechsix is offline
 
Join Date: Mar 2006
Location: Spring Hill, KS
Posts: 254
Default

Quote:
Originally Posted by Carl Froehlich View Post
This is a repeat of another post as was requested.

This RV-14A has a new from Van's IO-390 engine and a custom composite two blade CS prop (uses a Hartzell hub). The plane is built to plans, has a full dual EFIS IFR panel, and not yet painted (I suspect the paint will aggravate the nose light issue as the majority of the paint weight will be aft of CG). Seven qts of oil in the sump. The one battery (PC-680) is mounted on the firewall per the plans. As I previously mentioned, I suspect we'll end up putting another PC-680 battery on the firewall to help the CG issue and to address the woefully inadequate battery reserve offered by the single battery.

Here are the numbers. Plug them into the Van's W&B spreadsheet:
Right wheel: 434.5
Left wheel: 425.5
Nose wheel: 352.0

Here is the problem. At full 2050 pound gross (219 pound pilot and passenger, 100 pounds of baggage and full fuel) the CG is at 89.6" (aft limit is 88.24").

Carl
Carl, thanks for posting this information. Thus far I’ve collected empty weight and CG information for three RV-14As that are finished with paint, IO-390s, and Hartzell props. Two of the three have IFR panels but this isn’t a huge factor because panel equipment isn’t far from the CG. All three of them have an empty CG between 80.6 and 80.96. If you run the numbers to fill them up with gas, 100 lbs of baggage, and big people to bring them up to gross weight, and then burn off the fuel down to 8 gallons, you end up (worst case) at 87.47” which is well within the aft limit.

Now suppose I replace the metal Hartzell blades with composite. I’m not sure how much the weight change would be but I can’t imagine it’s more than a 20 lbs reduction (a Whirlwind would be a 16 lb reduction). If I remove 20 lb from the nose (around the 17” station) on the above three example aircraft, the worst case after burning down to min fuel is 88.38”…just a hair beyond the 88.24” limit. An unpainted -14A should move the CG measurably further forward. And if you go back to to the full fuel condition that you defined it will move the CG forward another .7 inches. I can’t see how you’re ending up at 89.6” in an unpainted -14A with full fuel…you’d almost have to remove the prop entirely, or install a lead brick in the tail.

As another sanity check, I tried plugging in the weights for your three wheels using the measured arms from the other three -14As. With 219 lb pax & pilot, 100 lb baggage, and full fuel this calculates out to a CG of between 87” and 87.5” (well forward of your 89.6” number). Of course I don’t know the actual arms on the subject -14A…they should be carefully measured with the aircraft in a perfectly level attitude. The nosegear is articulated so the measurement will vary somewhat from one -14A to the next. But I can’t imagine it moving enough to result in such a large discrepancy from the other flying examples.

Adding another PC680 is a big weight penalty so I’d take a very close look at your W&B to make sure you’ve got it right before adding ballast to the FWF area...
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Mark Navratil
Spring Hill, KS
RV-8A N2D #80583 - built/flew/sold
RV-14A #140017 - wings complete, empacone in progress...
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  #36  
Old 09-13-2016, 08:50 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,143
Default RV-14A W&B - mistake found

Quote:
Originally Posted by czechsix View Post
Carl, thanks for posting this information. Thus far I’ve collected empty weight and CG information for three RV-14As that are finished with paint, IO-390s, and Hartzell props. Two of the three have IFR panels but this isn’t a huge factor because panel equipment isn’t far from the CG. All three of them have an empty CG between 80.6 and 80.96. If you run the numbers to fill them up with gas, 100 lbs of baggage, and big people to bring them up to gross weight, and then burn off the fuel down to 8 gallons, you end up (worst case) at 87.47” which is well within the aft limit.

Now suppose I replace the metal Hartzell blades with composite. I’m not sure how much the weight change would be but I can’t imagine it’s more than a 20 lbs reduction (a Whirlwind would be a 16 lb reduction). If I remove 20 lb from the nose (around the 17” station) on the above three example aircraft, the worst case after burning down to min fuel is 88.38”…just a hair beyond the 88.24” limit. An unpainted -14A should move the CG measurably further forward. And if you go back to to the full fuel condition that you defined it will move the CG forward another .7 inches. I can’t see how you’re ending up at 89.6” in an unpainted -14A with full fuel…you’d almost have to remove the prop entirely, or install a lead brick in the tail.

As another sanity check, I tried plugging in the weights for your three wheels using the measured arms from the other three -14As. With 219 lb pax & pilot, 100 lb baggage, and full fuel this calculates out to a CG of between 87” and 87.5” (well forward of your 89.6” number). Of course I don’t know the actual arms on the subject -14A…they should be carefully measured with the aircraft in a perfectly level attitude. The nosegear is articulated so the measurement will vary somewhat from one -14A to the next. But I can’t imagine it moving enough to result in such a large discrepancy from the other flying examples.

Adding another PC680 is a big weight penalty so I’d take a very close look at your W&B to make sure you’ve got it right before adding ballast to the FWF area...
Thanks Mark. You got me to redo the W&B spreadsheet. It seems I carried over the baggage arm from the RV-10 - that really screwed up the numbers.

So at 2050 gross and 100 pounds in the baggage compartment, I now have a CG of 87.45" - inside the aft limit.

Your gentle prodding avoided sending the DAR a bad W&B - thanks.
Carl
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  #37  
Old 09-13-2016, 10:35 PM
czechsix's Avatar
czechsix czechsix is offline
 
Join Date: Mar 2006
Location: Spring Hill, KS
Posts: 254
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Quote:
Originally Posted by Carl Froehlich View Post
Thanks Mark. You got me to redo the W&B spreadsheet. It seems I carried over the baggage arm from the RV-10 - that really screwed up the numbers.

So at 2050 gross and 100 pounds in the baggage compartment, I now have a CG of 87.45" - inside the aft limit.

Your gentle prodding avoided sending the DAR a bad W&B - thanks.
Carl
No problem, sounds like an easy fix. My second-guessing you was somewhat selfishly motivated as I'd like to use a composite CS prop on my -14A, so I was dismayed when I saw your numbers. I had the blended airfoil Hartzell on my -8A and it is a great performing prop, but after flying with a friend who has a Whirlwind I was surprised how much the composite blades reduced vibration. The weight savings is great too--as long as the CG still works out. Looks like I should be ok in that regard...
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Spring Hill, KS
RV-8A N2D #80583 - built/flew/sold
RV-14A #140017 - wings complete, empacone in progress...
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  #38  
Old 09-14-2016, 06:29 AM
SabreFlyr SabreFlyr is offline
 
Join Date: Sep 2015
Location: Marion, IN
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Quote:
Originally Posted by Carl Froehlich View Post
So at 2050 gross and 100 pounds in the baggage compartment, I now have a CG of 87.45" - inside the aft limit.
Carl
Carl, is that with full fuel?

Edit: You do say "at 2050 gross." What is it at 8 gallons?
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LJ45 driver
RV-14 QB #140212
VS done (by previous builder)
Rudder finished & elevators almost done
2017 DUES PAID
Marion, IN MZZ

Last edited by SabreFlyr : 09-14-2016 at 06:31 AM.
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  #39  
Old 09-14-2016, 08:44 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,143
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Quote:
Originally Posted by SabreFlyr View Post
Carl, is that with full fuel?

Edit: You do say "at 2050 gross." What is it at 8 gallons?
The at gross, 2050 pounds, is with full fuel. At 8 gallons but everything else the same (219 pound pilot and passenger, 100 pounds of baggage), the CG is 88.2" -right at the aft limit.

The other extreme is 5 gallons of gas, 100 pound pilot, no passenger and no bags (1342 pounds) the CG is at 82.3", aft of the forward 82.08" limit.

Now plug in a more reasonable 200 pound pilot, no passenger, 5 gallons and no baggage and the CG is at 83.52".

Note - the plane is not yet painted (helps explain the 1212 pound empty weight). I suspect the CG to move aft a little after paint.

Carl
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  #40  
Old 09-15-2016, 05:44 PM
Aussieflyer Aussieflyer is offline
 
Join Date: Jan 2015
Location: Redcliffe, Queensland, Australia
Posts: 44
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I am not an expert in this W & B area. I paid a professional to do my W & B. As stated previously my empty weight is 1288.6lbs and arm 80.9 inches. The aircraft is painted (inside & out) YIO 390 & 74 inch Hartzell and Garmin dual G3X, remote Garmin Transponder, VPX and GTN 650.

On first flight with half tanks we found that we were running out of elevator control on the flair to land. A little more speed (75kts) and a little more power fixed this. I then tried quarter tanks and full tanks in landing configuration, the results remained fairly similar to the first landing. 45lbs of weight (drummed water) was then added to the baggage area. Much better elevator authority on landing.
Another 45 lbs of water was added, now a total of 90 lbs of weight in the baggage area. Two pilots 360lbs and quarter tanks the aircraft handled just superbly with much improved elevator authority on landing. The next flight was with full tanks, 90lbs in the baggage area and 360lbs in the front two seats. Once again landing was conducted with elevator authority. A series of landings from short field, flapless and flapped landings, no issues.
It appears to me that the ballast in the baggage compartment is going to be the norm for everyday flying operations. With further testing I'm positive the baggage capacity will well exceed the 100lbs as stated by Van's. It appears on paper that my wife and I (300lbs) can carry 130lbs of baggage and remain within the envelope. FYI Alan
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