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  #41  
Old 09-15-2016, 06:04 PM
mturnerb mturnerb is offline
 
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Location: Ponte Vedra, FL
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Originally Posted by Aussieflyer View Post
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
This is interesting - your description of the control issue sounds like a forward CG but the RV-14A seems to have more of an aft CG tendency. Using your numbers, with two pilots @ 360lbs, half fuel as you describe I calculate an arm of 84.6 - right in the envelope. I'm interested if others have had similar experiences with elevator authority. (I'm starting a -14A build so a definite personal interest)
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  #42  
Old 09-16-2016, 01:06 AM
Aussieflyer Aussieflyer is offline
 
Join Date: Jan 2015
Location: Redcliffe, Queensland, Australia
Posts: 44
Default 14A flight tests with Weight & Balance issues

My buddy 4 hangars down has a RV10 and when he flew my 14A he said that it was very similar to his. He says a light loading in his RV10 produces a forward C of G and the elevator starts to run out on landing. He uses rear ballast in the RV10 on light loadings. Seeing the RV10 and RV14 share the same wings perhaps this is not surprising.
I can't give you any mathematical advice on the C of G, I can only tell you how it flies. Hope this is helpful. Alan
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  #43  
Old 09-16-2016, 09:09 AM
TimO TimO is offline
 
Join Date: Feb 2005
Location: Wisconsin
Posts: 341
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I have both an RV10 and and RV14, and I think they both are nearly identical in the way they fly and land. If you have time in one, it will feel about the same in the other. The RV-14 does hunt a little more when trimming at higher speeds, and seems a little less pitch stable while accelerating. Once in cruise and trimmed they are very similar with the RV-14 having maybe a slightly more pitch sensitive elevator, and of course a slightly quicker roll rate. Otherwise, the 2 planes are so much alike that it's hard to find differences.

The RV-10, when I did a factory demo flight, took up all of the elevator trim that I had. Everyone worried about it "running out of trim" with how much nose up trim it took. People talk the same about the RV10. "I keep 20lbs of tools in the back....", or "When flying alone I fill an X gallon jug with water but when I pick up people I just dump the water." To me, I think it's a non-issue.
When I did my first flights in the RV-10, I had something in the rear because of the worry. But as time went on, I've flown the plane in pretty much every configuration imagineable, and I haven't found anything that requires any compensation. Sure, you'll use up most of the trim if you leave the back end bare. Maybe if you took all the seat cushions out in back and stripped it all to bare aluminum walls, you could actually run out. But who does that in an RV10? On the flip side, if you fill the plane up with 4 people and 4 sets of SCUBA gear as I've done before, and you're towards the very aft end of CG, the plane is very pitch sensitive on landing and you have to be sure not to pull too hard when you flare. But, it's certainly not hard to deal with. You can tell when you're near that aft CG when you step on the step getting in/out. If you're nearing the aft the plane will be nose light and you have to be careful not to put more than one person on the step area at a time.

In the RV-14, I did my first flight with just the standard interior. Nothing special. I think I left the copilot seat cushions in, but I also had baggage area carpeting...I think it was like 3lbs worth...4 max. I've flown it that way many many times. I've also taken a trip now for 17 hours of flying where I was loaded up pretty much at or near gross and it flies fine that way too. It has most of the same tendencies as the RV-10. But I find that there really is no need to do anything at all to compensate for the design of the plane. Both of my planes have 2 blade hartzell props, and the normal recommended engines, with the batteries located in the normal places as well. Maybe if you get a light prop, you will have to compensate by moving something else around. But with absolute certainty I will will say say this: Doing ANYTHING to PURPOSELY try to make your RV10 or RV14 less nose heavy by building it with different components (propellers, etc..) or component locations (moving batteries, etc..) solely for the idea of making it less nose heavy is a big mistake. The planes get their utility by having the CG towards the front limit, allowing you to load them up and use them as people do. It keeps the RV-14 safer for aerobatics that way also. So don't build an RV-14 with the goal to try to "fix" the noseheavy problem. You would be better off trying to make it MORE noseheavy if anything, as both planes can be loaded out of aft CG if someone tries hard enough...but Van's did good with the CG location as built, so I recommend sticking with it.

If you feel the need to have tail weight, I think a basic small tool kit would be plenty. And after having a couple of tire issues over the years, I will always carry tools when not flying right in the local area.
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RV-10 N104CD - Flying 2/2006 - 1300+ hours http://www.MyRV10.com
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  #44  
Old 09-16-2016, 09:33 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by TimO View Post
Doing ANYTHING to PURPOSELY try to make your RV10 or RV14 less nose heavy by building it with different components (propellers, etc..) or component locations (moving batteries, etc..) solely for the idea of making it less nose heavy is a big mistake. The planes get their utility by having the CG towards the front limit, allowing you to load them up and use them as people do. It keeps the RV-14 safer for aerobatics that way also. So don't build an RV-14 with the goal to try to "fix" the noseheavy problem. You would be better off trying to make it MORE noseheavy if anything, as both planes can be loaded out of aft CG if someone tries hard enough...but Van's did good with the CG location as built, so I recommend sticking with it.
I can't add anything additional of value.... Tim pretty much nailed it.

If you are building with a light weight prop (or some other change that will influence CG more than a small amount), it would be a good idea to do something else to compensate if you want to maintain the maximum utility and handling qualities that are available with the RV-14.
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  #45  
Old 09-16-2016, 03:11 PM
MED MED is offline
 
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Location: Aiken, SC
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Does anyone know if the composite Hartzell prop is light enough to cause a CG problem? It looks really nice on Carl and Rafael's plane and I am inclined to follow their lead, but they haven't done the W&B yet. Sorry, I don't know the weight vs. the aluminum Hartzell.
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  #46  
Old 09-19-2016, 06:06 PM
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czechsix czechsix is offline
 
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Location: Spring Hill, KS
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Originally Posted by MED View Post
Does anyone know if the composite Hartzell prop is light enough to cause a CG problem? It looks really nice on Carl and Rafael's plane and I am inclined to follow their lead, but they haven't done the W&B yet. Sorry, I don't know the weight vs. the aluminum Hartzell.
Mark,

I’ve done W&B calculations using data from three flying RV-14As equipped with IO-390s and Hartzell aluminum CS props. In each example I reduced the weight on the nose to represent a Whirlwind composite CS prop (200RV or 74RV which weigh 41 lb and 42 lbs respectively including the spinner according to http://www.whirlwindaviation.com/props/rvseries.asp). You can load the airplane up with full fuel, 100 lbs of baggage, and then select pilot/pax weights that bring you up to full gross weight, and then assume you burn fuel down to an 8 gal minimum. This puts you right at aft CG with min fuel. You can get the specs from Hartzell for their composite prop and compare them to the WW prop weights but I expect they will be very similar in weight, so I think you should be ok using a composite Hartzell.

If you go this route I’d recommend doing everything possible to minimize weight in the tail…use a light coat of primer on the inside, single stage paint (in lieu of base/clear) on the outside, don’t mount any avionics boxes or antennas back there, etc. Another idea I’m thinking about is moving the ELT to the baggage compartment…Vans mounts it way back in the tail, but the antenna is in the baggage compartment, so if the fuselage gets ripped in half or the cabin area is damaged severely (fire, etc) the ELT isn’t going to be sending out a signal anyway. Moving the ELT forward helps a bit with CG and has the added benefit of being more easily accessible for maintenance or after a survivable emergency landing.

If you want the flexibility to load more than the recommended 100 lbs in the baggage compartment or if you make other significant changes to your RV-14 that move the CG aft it would probably be better to plan on the aluminum Hartzell. The aluminum Hartzell is also much less expensive and performs just as well (according to one pilot I talked to at Oshkosh who had “upgraded” from the metal blended airfoil Hartzell to composite Hartzell, the metal prop actually had better performance by 2-3 kts). YMMV…
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  #47  
Old 09-20-2016, 09:48 AM
MED MED is offline
 
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Mark
Thanks for the research. I still have some time before I have to make my decision - probably by next Oshkosh. However, my hanger neighbors have already made the decision and are currently hoping it will be ok. I will pass along your comments and will wait to see how things work out for them.
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  #48  
Old 11-11-2016, 01:54 AM
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Av8rRob Av8rRob is offline
 
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Default Earth x battery?

As a guy who's making his add/delete list for my fuselage order I was thinking about buying the new earth x 680c battery,........but this thread gives me pause. Since the battery box is in the fuselage kit I though now would be the time to replace the std one. Losing 11 lbs is great but at the firewall, that might be a problem. Has anyone else done this on a -14. I guess I could wire two batteries for a aux? Another similar issue is that it appears going for the beringer wheel/brakes package would cause the same issue as the mains on the taildragger are slightly ahead of the c.g. This also saves about 11 lbs. Any input is appreciated

Thanks


Rob
Rv-14 emp
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Last edited by Av8rRob : 11-11-2016 at 02:05 PM.
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  #49  
Old 11-12-2016, 11:46 PM
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czechsix czechsix is offline
 
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Location: Spring Hill, KS
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Quote:
Originally Posted by Av8rRob View Post
As a guy who's making his add/delete list for my fuselage order I was thinking about buying the new earth x 680c battery,........but this thread gives me pause. Since the battery box is in the fuselage kit I though now would be the time to replace the std one. Losing 11 lbs is great but at the firewall, that might be a problem. Has anyone else done this on a -14. I guess I could wire two batteries for a aux? Another similar issue is that it appears going for the beringer wheel/brakes package would cause the same issue as the mains on the taildragger are slightly ahead of the c.g. This also saves about 11 lbs. Any input is appreciated
Rob,

The Beringer wheels & brakes are going to have very minimal impact on CG because they are so close to the CG...I wouldn't worry much about that one.

The EarthX battery should be fine if you're using a Hartzell metal prop. If you want to put on a composite prop AND use the EarthX battery you might run into aft CG issues when loading up the aft baggage compartment. Moving the ELT forward to the baggage compartment may be enough to offset the lighter battery on the firewall, but you'd have to play around with W&B numbers to see. If I recall correctly I think the EarthX battery might not fit in the standard PC680 battery box that comes with the -14 kit, but if you use the EarthX battery box I believe you will be able to install either a PC680 or EarthX battery. I would check with EarthX to confirm, but if this is true you could install the EarthX battery box and then wait until the very end to decide which battery to install based on where your final CG comes out. If you do this think about the battery leads to make sure they can fit either battery (the terminals are not in exactly the same place, but close).
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RV-8A N2D #80583 - built/flew/sold
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  #50  
Old 11-13-2016, 10:52 AM
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Av8rRob Av8rRob is offline
 
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Good info thanks. I will delete the vans battery box and use the convertible one from earth x to give options. Besides moving the elt, another possibility available is buying a lighter weight tailwheel.
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