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RV-14 C.G. / weight & balance sample

rvbuilder2002

Legacy Member
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A (sample) document containing W & B data for the RV-14 and RV-14A prototypes can be found HERE

RV-14 C.G. quick reference chart HERE
And RV-14A C.G. quick reference chart HERE

(It would be great if a mod. would sticky this thread.....)
 
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Just weighed N914VA the other day. 1246 lbs. empty, w/o paint. Empty C.G came out at 81.38".

Will reweigh after paint next month.
 
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I don't know if it would account for all of the difference, but Garmin G3X components are a bit heavier than Skyview.
 
It's most probably the Garmin panel. It's pretty complete with dual G3X's, GTN750, GMA 240 audio panel, GMC 307 AP controller, a GTR200R comm, GDL 39, remote GTX 330 xpndr, and all the attendant modules that go with supporting these devices. And there are a bunch of them.

Plus I have good solid carpet in the front an rear from Flightline Interiors along with leather seats and armrests.

It all adds up. I will reweigh it after paint and see where we are then.
 
It's most probably the Garmin panel. It's pretty complete with dual G3X's, GTN750, GMA 240 audio panel, GMC 307 AP controller, a GTR200R comm, GDL 39, remote GTX 330 xpndr, and all the attendant modules that go with supporting these devices. And there are a bunch of them.

Plus I have good solid carpet in the front an rear from Flightline Interiors along with leather seats and armrests.

It all adds up. I will reweigh it after paint and see where we are then.

Leather! You got real Leather????
 
Mitch, I will be passing through Waldorf next Thursday or Friday. Is it ok if I stop by and see your -14?
 
Yeah Scott. A big box arrived unannounced and voila! A leather interior.

Apparently, it's been a closely guarded secret, but I knew it would have to come out sometime. :)
 
Weight Gain

If my 14 gets close to this, my wife an me can gain a lot of weight and still fly with full tanks and max luggage... not sure if that is a good thing :eek:

Yes, but not sure if you will be able to get in and out. :) I am telling my wife "we" need to lose some weight and get in shape to get in and out of the plane easily.
 
Interesting...

Just weighed N914VA the other day. 1246 lbs. empty, w/o paint. Empty C.G came out at 81.38".

Will reweigh after paint next month.

Scott & Mitch, thanks for posting this info. A few comments/questions:

It's interesting that Mitch's -14A has a CG that is further aft (81.38) compared to the original prototype RV-14A (which came out at 80.61). I would have expected the opposite. Most significantly, Mitch's plane is unpainted...paint moves the CG aft, so an unpainted airplane should have a further forward CG. If the avionics in the panel area are heavier in Mitch's plane, that would move the CG slightly further forward. The G3X pitch servo is lighter than Dynon's, which would again move the CG forward. Something doesn't add up, unless the leather seats & bag compt upholstery weighs an extra 50 lbs or so. Is there anything else mounted in the aft fuselage on Mitch's plane (transponder, magnetometer, yaw damper servo)?

As a side note, the empty weight of the proto -14A on the https://www.vansaircraft.com/pdf/RV-14&RV-14A_SampleW&B.pdf worksheet doesn't equal the sum of the three wheel weights. 436 + 364 + 435 = 1235 lb (not 1239 as shown). I'm not trying to nitpick, just wondering if the discrepancy indicates any errors in the original data (which might explain the CG differences as well?).

The reason it matters is because if I use the data from the original -14A, I can put a Whirlwind prop on it and stay within aft CG with two average adults, full baggage, and minimum fuel. Using Mitch's numbers, I'll have to stick with the Hartzell otherwise I run out of aft CG unless I limit myself to less baggage or lighter than average pilot/passenger. And it'll only get worse after painting.

Thanks,
 
Mark,
I agree with your assessment and can't explain the difference. It should be closer than the current data shows. The weight discrepancies (I will look into where the error got introduced) of N214VA are not enough to influence the C.G. position much at all.
N214VA has been weighed on digital calibrated scales a number of times in the past couple years. Each time there has been no surprise as to the result.

I am not sure what Mitch used for scales, whether the tanks were completely empty so that no compensation had to be done, etc...., but I would have expected N914VA to have been much closer to N214VA than it is. We will have to look into it, but my gut feeling at the moment is that there is possibly an error in the data for N914VA (it's C.G. is a small bit further aft than what the RV-14 tail dragger is).
So until further information is provided, consider the values for N214VA and N144VA to be the official examples.
 
As a side note, the empty weight of the proto -14A on the https://www.vansaircraft.com/pdf/RV-14&RV-14A_SampleW&B.pdf worksheet doesn't equal the sum of the three wheel weights. 436 + 364 + 435 = 1235 lb (not 1239 as shown). I'm not trying to nitpick, just wondering if the discrepancy indicates any errors in the original data (which might explain the CG differences as well?).

,

Errors in the posted document have been corrected.

Because the airplane has evolved a bit since new, there was some minor weight additions and subtractions that are part of the aircraft document that were deleted to reduce confusion. When the deletions were made, the weight and moment data wasn't listed correctly.

These are the official samples based on data from the two prototypes.
Still looking into why Mitch's computed C.G. is actually aft of the taildragger prototypes.
 
First of all, Mark, thanks for pointing the CG discrepancy out. It really got me thinking. Yesterday, I measured the moment arms for the landing gear again. Got different results than the first go around. Don't know why. Perhaps me or someone else bumped the airplane after it was set. Maybe it shifted somehow. Who knows. Anyway, with the new measurements, the empty CG is located 80.75" aft of datum. That is .17" further aft of the prototype 14A. Problem solved.
 
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I think the plan is for N214VA and N144VA to be the official examples.
Since N914VA is very close to matching N214VA, I am not sure what value it would have, but if that is what you wanted you can easily move a little bit of weight in the data set from the main wheels to the nose wheel until you get the C.G. position that Mitch quoted and that should be pretty close.
 
W&B Done

Errors in the posted document have been corrected.

These are the official samples based on data from the two prototypes.
Still looking into why Mitch's computed C.G. is actually aft of the taildragger prototypes.

Had a W&B done yesterday. Weight is 1229.5, CG is 80.54. Here's where it gets interesting. The arm on the tail for me is 255.5 and Van's lists N144VA as 230.38, a full 25 inches difference. They also show the weight on the tail is 75 and mine is 57, 18 lbs difference. So something is amiss there. We had 3 people double check the measurements, then totally redid it and still came up with the same number. We had the datum 72" in front of the leading edge of the wing, the plane level in flying attitude, per the instructions. Also, why would their tail be that much more weight? I do have the ELT back there like they do. Possibly the difference with the tail could be paint, mine has not been painted, but was drained of all gas. All work was done on professional digital scales by a very experienced A&P.
 
Stoney,

As explained in the response to your PM I sent to you over the weekend, the aft arm position on the sample form got inadvertently labeled tail wheel. The actual position used for weighing was the bolt that attaches the tail spring to the fuselage. A short threaded standoff can be made to thread onto the stub end of the bolt and then the tail supported with a jack stand set up on the scale pad. The tail has to be raised quite high and be carefully adjusted so that the airplane is exactly level. The hydr. jack stand makes this simple.

So, I think if you measure you will find that the distance between the tail spring attach bolt and the tail wheel axle bolt is probably the difference you see.
The sample form will be updated to reflect the difference.

The different CG position for your airplane when compared to N144VA is not really a surprise considering it is only 5 pounds lighter, and it is not painted. A paint job will add more than 5 pounds (8-15+ is common) so that means your airplane is already slightly heavier (at least will be once it is painted) than N144VA. Depending on where that extra weight is located, and then factoring in the shift aft that the C.G will make when it gets painted. As you mentioned, weight on the tail from paint or other objects like an ELT will have a strong influence because of the large moment as a result of the long moment arm.

Based on this information, I think your calculated CG position is probably about what would be expected.
 
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Stoney,

As explained in the response to your PM I sent to you over the weekend, the aft arm position on the sample form got inadvertently labeled tail wheel. The actual position used for weighing was the bolt that attaches the tail spring to the fuselage. A short threaded standoff can be made to thread onto the stub end of the bolt and then the tail supported with a jack stand set up on the scale pad. The tail has to be raised quite high and be carefully adjusted so that the airplane is exactly level. The hydr. jack stand makes this simple.

So, I think if you measure you will find that the distance between the tail spring attach bolt and the tail wheel axle bolt is probably the difference you see.
The sample form will be updated to reflect the difference.

The different CG position for your airplane when compared to N144VA is not really a surprise considering it is only 5 pounds lighter, and it is not painted. A paint job will add more than 5 pounds (8-15+ is common) so that means your airplane is already slightly heavier (at least will be once it is painted) than N144VA. Depending on where that extra weight is located, and then factoring in the shift aft that the C.G will make when it gets painted. As you mentioned, weight on the tail from paint or other objects like an ELT will have a strong influence because of the large moment as a result of the long moment arm.

Based on this information, I think your calculated CG position is probably about what would be expected.

Scott,

I apologize, I didn't see the PM. Normally it notifies me, my bad. O.K., so I will go with what I have, then once I get it painted and redo the W&B, I'll see what it comes up with. Thanks for the response.
 
Update on Mitch's -14A W&B?

Mitch, now that you've got paint on N914VA, did you get a chance to redo the W&B? I'm very interested to see where the final numbers for empty weight and CG ended up with paint on it...

Thanks,
 
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
 
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
 
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.
 
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
 
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...
 
RV-14A W&B - mistake found

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
 
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. :D 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...
 
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
 
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
 
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)
 
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
 
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.
 
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.
 
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.
 
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?
 
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.
 
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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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).
 
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.
 
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.

The tailwheel has about the longest moment arm on the airplane, so that's a good place to save a few ounces if you can. Also if you use a light coat of primer on the empennage and single stage paint (instead of base/clear) those things all add up. Another thing some people do is to add fiberglass to cover the gap between the empennage tip fairings and the aluminum structure. That plus several layers of high build primer to blend the tips seamlessly into the rest of the structure also adds weight (and time). IMHO a nice clean joint where the fiberglass tips meet the aluminum looks nice and it's easier and lighter weight too.
 
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