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Weight & Balance

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dfmoeller

Joined: 19 Jun 2006
Posts: 60
Location: Austin, TX

Posted: Mon Jul 10, 2006 5:55 pm Post subject: Weight & Balance

Here's another question for you guys.



Does anyone have a good sample (meaning realistic) of a W&B sheet for a 

601XL with Rotax 912ULS?  And can you scan it and send to me?  I'm trying to 

get a sanity check on my numbers.



Thanks,



Doug

craig(at)craigandjean.com
Guest

Posted: Mon Jul 10, 2006 7:51 pm Post subject: Weight & Balance

I don't know if this will meet your needs:



www.zenithair.com/zodiac/xl/data/xl-w&b-new.pdf



Also look at this one if you have Excel:



www.ch601.org/resources/material/Wt&Bal-Your%20Plane.xls



-- Craig

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Fri Jul 28, 2006 9:11 pm Post subject: Re: Weight & Balance

My CG attached. Also attached spreadsheet to help work out CG scenarios. Rear baggage is a big problem if you have two good sized people in the plane. The wing lockers are a must in that type of scenario.



I don't care what anyone from Zenair says … the standard motor mount that you get for the 912 is flawed as far as CG is concerned. Hey, I can do the grade-school math as well as the next guy. 



To solve the problem, I had a special mount and cowling made by CZAW to move the 912 engine forward 4 additional inches from original design. The empty CG is now 12", which is so/so. It was more than 14" with the standard mount; which is awful. It aught to be more like 10” … but the nose would be too long and would interfere with visibility.



I’m toying with the idea of using the composite gear; which should improve the CG and useful load at the same time … but it’s a significant retrofit.



I've used this spreadsheet for my own calculations and I believe it to be correct, but in no way do I warranty the spreadsheet. Check the math. Use at your own risk.





 	  dfmoeller wrote: 	
		  Does anyone have a good sample (meaning realistic) of a W&B sheet for a 601XL with Rotax 912ULS?  And can you scan it and send to me?  I'm trying to get a sanity check on my numbers.

WB-601XL.xls

Description:

CG Scenarios Worksheet

Download

Filename:

WB-601XL.xls

Filesize:

43.5 KB

Downloaded:

873 Time(s)

xl-wb.pdf

Description:

Weight and Balance Sheet

Download

Filename:

xl-wb.pdf

Filesize:

40.75 KB

Downloaded:

3813 Time(s)

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

Last edited by David X on Sat Jul 29, 2006 8:12 am; edited 2 times in total

dfmoeller

Joined: 19 Jun 2006
Posts: 60
Location: Austin, TX

Posted: Sat Jul 29, 2006 5:49 am Post subject: Re: Weight & Balance

Excellent work.  Just what I was looking for.  thanks!



Doug



 	  David X wrote: 	
		  My CG attached. Also attached spreadsheet to help work out CG cenarios. Rear baggage is a big problem if you have two good sized people in the plane. The wing lockers are a must in that type of scenario.



I don't care what anyone from Zenair says … the standard motor mount that you get for the 912 is flawed as far as CG is concerned. Hey, I can do the grade-school math as well as the next guy. 



To solve the problem, I had a special mount and cowling made by CZAW to move the 912 engine forward 4 additional inches from original design. The empty CG is now 12", which is so/so. It was more than 14" with the standard mount; which is awful. It aught to be more like 10” … but the nose would be too long and would interfere with visibility.



I’m toying with the idea of using the composite gear; which should improve the CG and useful load at the same time.



 	  dfmoeller wrote: 	
		  Does anyone have a good sample (meaning realistic) of a W&B sheet for a 601XL with Rotax 912ULS?  And can you scan it and send to me?  I'm trying to get a sanity check on my numbers.

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Sat Jul 29, 2006 8:11 am Post subject: Re: Weight & Balance

I've used this spreadsheet for my own calculations and I believe it to be correct, but in no way do I warranty the spreadsheet. Check the math. Use at your own risk.

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Mon Jul 31, 2006 7:20 am Post subject: Re: Weight & Balance

Any way you could add a spot for weight in the wing lockers?

_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Mon Jul 31, 2006 8:28 am Post subject: Re: Weight & Balance

Attached is an updated version allowing for wing lockers in any given scenario. I never included wing lockers in the prior version because the arm is very close too but less than pilot/co-pilot; thus making it much less critical when trying to measure overall affect of people, fuel and baggage. It is interesting nonetheless to observe scenarios in which lockers are used as opposed to rear baggage. 



BTW: One of the surprising impacts on total useful load and CG in particular is paint! Between 2 and 3 gallons of primer and paint are needed (depending on number of coats) at approximately 12 lbs per gallon. You could easily have 30 lbs of paint and primer on the aircraft with as much as 6 lbs of it on the rudder, horizontal stabilizer and tail section where the CG impact is most extreme. The net CG affect of painting your aircraft is to move the CG rearward approximately 1 inch; which is a lot when you consider the entire CG range (between 20% and 30% of MAC) spans only 6 inches ... not to mention reducing useful load by 30 lbs. On the other hand, I hear that maintaining the polish on bare aluminum is pretty labor intensive.



I in no way warranty the spreadsheet. Check the math. Use at your own risk. 



 	  Gig Giacona wrote: 	
		  Any way you could add a spot for weight in the wing lockers?

WB-601XL.xls

Description:

W&B 601XL (with wing lockers)

Download

Filename:

WB-601XL.xls

Filesize:

47.5 KB

Downloaded:

366 Time(s)

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

dredmoody(at)cox.net
Guest

Posted: Mon Jul 31, 2006 11:00 am Post subject: Weight & Balance

Are you considering the residual weight of paint on the airplane to be similar to the wet paint weight in the can?  If so, I think you are over-estimating the dry weight of the paint. Does anyone have a reliable figure on the dry weight of a gallon of paint on the airplane? Also, are you sure about the 12 pounds per gallon weight of the wet paint? Water is only 8 pounds per gallon and a specific gravity of 1.5 for wet paint sounds high to me.



Ed Moody II



---- David X <dxj(at)comcast.net> wrote: 

 

lockers are used as apposed to rear baggage. 

 	  Quote: 	
		   

 BTW: One of the surprising impacts on total useful load and CG in particular is paint! Between 2 and 3 gallons of primer and paint is needed (depending on number of coats) at approximately 12 lbs per gallon. You could easily have 30 lbs of paint and primer on the aircraft with as much as 6 lbs of it on the rudder, horizontal stabilizer and tail section where the CG impact is most extreme.

Daniel Vandenberg

Joined: 16 Apr 2006
Posts: 22

Posted: Mon Jul 31, 2006 11:48 am Post subject: Weight & Balance

Obviously, when primer or paint dries the moisture is mostly gone...and the dried primer/paint left behind must weigh much less than it did in the can. 

   

  Does anybody know what percentage of weight is left in paint/primer after it dries?

   

  DJV



David X <dxj(at)comcast.net> wrote:

  [quote]--> Zenith-List message posted by: "David X" 



Attached is an updated version allowing for wing lockers in any given scenario. I never included it prior because the arm is very close too but less than pilot/co-pilot; thus making it much less critical when trying to measure overall affect of people, fuel and baggage. It is interesting nonetheless to observe scenarios in which lockers are used as apposed to rear baggage. 



BTW: One of the surprising impacts on total  useful load and CG in particular is paint! Between 2 and 3 gallons of primer and paint is needed (depending on number of coats) at approximately 12 lbs per gallon. You could easily have 30 lbs of paint and primer on the aircraft with as much as 6 lbs of it on the rudder, horizontal stabilizer and tail section where the CG impact is most extreme. The net affect is to move the CG rearward approximately 1 inch; which is a lot when you consider the entire CG range (between 20% and 30%) of MAC spans only 6 inches.



I in no way do I warranty the spreadsheet. Check the math. Use at your own risk. 





Gig Giacona wrote:

 	  Quote: 	
		   Any way you could add a spot for weight in the wing lockers?


	




--------

Zodiac 601 XL - CZAW Built - Rotax 912S

DO NOT ARCHIVE





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=51047#51047





Attachments:

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Mon Jul 31, 2006 12:29 pm Post subject: Re: Weight & Balance

You brought up a good point about dry paint weighing less than wet paint ... a point I didn't think about. I did a little research ...



A urethane primer weighs about 12 lbs per gallon wet and contains about 80% solids (pigments, binders etc) ... so approximately 20% of the primer weight is lost in drying. Dry primer would therefore weigh about 9.5 lbs/gallon.



A polyurethane top coat would weigh about 10 lbs per gallon wet and contain about 65% solids. Dry weight would therefore be about 6.5 lbs per gallon for the top coat. 



A clear coat would be about 8 lbs/gallon with 60% solids, leaving about 5 lbs/gallon dry weight.



Assuming that the aircraft has approximately 350 sq feet of surface, and that there would be about 6 coats of paint (two coats primer, two top coats and two clear coats) and assuming that you would be using about 1 gallon per 775 sq feet ... then you would be using a little under 1 gallon of each type of paint (nearly 3 gallons total).



All in all, you'd be adding perhaps 21 lbs of dry paint weight as opposed to the 30 lbs of wet paint quoted previously. That's 4.5 pounds of dry paint on the tail (as opposed to the 6 lbs quoted before). The total CG affect would be .8 inches rearward instead of the 1 inch quoted before. Not as significant as previously estimated, but still pretty significant on a light plane such as the 601XL.



For reference: http://www.performancecoatings.dupont.com/dpc/en/us/html/prodinfo/aviation/techavi.html



 	  Daniel Vandenberg wrote: 	
		  Obviously, when primer or paint dries the moisture is mostly gone...and the dried primer/paint left behind must weigh much less than it did in the can.

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

dredmoody(at)cox.net
Guest

Posted: Mon Jul 31, 2006 2:13 pm Post subject: Weight & Balance

My reasearch on the DuPont site showed that Imron AF730 topcoat weighed 8.5 pounds per gallon and once dry it weighed only 3.8 pounds from that original gallon. That's way different from what you found for polyurethane. I wonder if maybe less urethane would cover more airplane?



Ed Moody II



---- David X <dxj(at)comcast.net> wrote: 

 	  Quote: 	
		   

 

 You brought up a good point about dry paint weighing less than wet paint ... a point I didn't think about. I did a little research ...

p.mulwitz(at)worldnet.att
Guest

Posted: Mon Jul 31, 2006 2:57 pm Post subject: Weight & Balance

Just a guess:  The solvent weighs about the same as gasoline - 6 pounds per gallon.  Perhaps there is as much as a quart or two of solvent in a gallon.  If the can weighs 12 pounds as suggested by the earlier poster, then there might be around 9 pounds of solids in the gallon.



 Paul

 XL fuselage

 do not archive



 At 12:46 PM 7/31/2006, you wrote:

  	  Quote: 	
		  Obviously, when primer or paint dries the moisture is mostly gone...and the dried primer/paint left behind must weigh much less than it did in the can. 

  

 Does anybody know what percentage of weight is left in paint/primer after it dries?

  

 DJV



 D

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Mon Jul 31, 2006 3:15 pm Post subject: Re: Weight & Balance

It's amazing how two people can read the same damned thing and get something different out of it when trying to support an argument.



You're quoting clear-coat at 56% solids by weight (ready to spray); which means you would expect the dry paint to be 56% of the weight of the wet paint ... or about 4.76 lbs/gallon (according to Spock).  :roll: 



You plan on using just clear-coat? Might look really cool, but not sure if it sticks to bare aluminum very well.



What the hell do I know, anyway. It was just a thought ... that paint actaully weighs something ... and therefore affects CG. Everyone else can live in denial for all I care.



Anyway, hope the CG spreadsheet helps somebody out.



 	  dredmoody(at)cox.net wrote: 	
		  My reasearch on the DuPont site showed that Imron AF730 topcoat weighed 8.5 pounds per gallon and once dry it weighed only 3.8 pounds from that original gallon. That's way different from what you found for polyurethane. I wonder if maybe less urethane would cover more airplane?

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

gboothe(at)calply.com
Guest

Posted: Mon Jul 31, 2006 4:15 pm Post subject: Weight & Balance

David,  

   

Don't be offended. If your every word was not dissected and examined you would think you posted to the wrong list. I'm sure the silent majority will find your spreadsheet quite useful, as is. I do.  

   

Now, what color scotchbrite pad do you recommend?  

   

Gary Boothe  

Cool, CA  

601 HDSTD, WW Conversion  

Tail done, working on wings....  

Do Not Archive  

   

   

--> Zenith-List message posted by: "David X" <dxj(at)comcast.net>  

   

It's amazing how two people can read the same damned thing and get something different out of it when trying to support an argument...  

   

...What the hell do I know, anyway. It was just a thought ... that paint actaully weighs something ... and therefore affects CG. Everyone else can live in denial for all I care.  

   

Anyway, hope the CG spreadsheet helps somebody out.  

   

   

dredmoody(at)cox.net wrote:  

 	  Quote: 	
		   My reasearch on the DuPont site showed that Imron AF730 topcoat weighed 8.5 pounds per gallon and once dry it weighed only 3.8 pounds from that original gallon. That's way different from what you found for polyurethane. I wonder if maybe less urethane would cover more airplane?  

   
	


   

--------  

Zodiac 601 XL - CZAW Built - Rotax 912S  

DO NOT ARCHIVE  

   

   

   

   

Read this topic online here:  

   

http://forums.matronics.com/viewtopic.php?p=51233#51233

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Jul 31, 2006 7:07 pm Post subject: Weight & Balance

Because airplanes very by many different factors the best thing to do is

weigh it and then calculate the W&B.  I've seen AC43 mentioned several times

on this list.....  It has all the procedures and math ( grade 4 level)

required to produce your custom W&B sheet for conventional and tri gear

planes.

Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

admin(at)arachnidrobotics
Guest

Posted: Mon Jul 31, 2006 8:54 pm Post subject: Weight & Balance

Everyone knows blue scotchbrite is the best.  I don't see why we discuss it so much on this list!  Now where did I put that purple aluminum magnet and the box of bend deductions???



Gary Boothe <gboothe(at)calply.com> wrote: 	  Quote: 	
		                David,

   

  Don't be offended. If your every word was not dissected and examined you would think you posted to the wrong list. I'm sure the silent majority will find your spreadsheet quite useful, as is. I do.

   

  Now, what color scotchbrite pad  do you recommend?

   

  Gary Boothe

  Cool, CA

  601 HDSTD, WW Conversion

  Tail done, working on wings....

  Do Not Archive

   

   

  --> Zenith-List message posted by: "David X" <dxj(at)comcast.net>

   

  It's amazing how two people can read the same damned thing and get something different out of it when trying to support an argument...

   

  ...What the hell do I know, anyway. It was just a thought ... that paint actaully weighs something ... and therefore affects CG. Everyone else can live in denial for all I care.

   

  Anyway, hope the CG spreadsheet helps somebody out.

   

   

  dredmoody(at)cox.net wrote:

  > My reasearch on the DuPont site showed that Imron AF730 topcoat weighed 8.5 pounds per gallon and once dry it weighed only 3.8 pounds from that original gallon. That's way different from what you found for polyurethane. I wonder if maybe less urethane would cover more airplane?

   

   

  --------

  Zodiac 601 XL - CZAW Built - Rotax 912S

  DO NOT ARCHIVE

   

   

   

   

  Read this topic online here:

   

  http://forums.matronics.com/viewtopic.php?p=51233#51233

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Tue Aug 01, 2006 2:32 pm Post subject: Re: Weight & Balance

For anyone trying to thumbnail the CG on an unpainted 601XL, you should plan to put the CG a little more forward of where you want it to ultimately be when the aircraft is painted and trimmed. It sounds trivial, but it's not all that trivial on this particular aircraft.



As far as calculators to figure out your W&B ... by all means use one to test my math, please! The advantage of the spreadsheet, however, is that you can see the entire range of CG throughout the entire fuel burn ... not just one slice in a point in time for a particular scenario. 



Most aircraft will stay in CG range throughout the flight so long as you start below gross and are in CG range at the beginning of the flight. This is not true of the Zodiac using the stock mount from Zenair for the 912S (unless they changed it since).



This is how I discovered that it is possible to take off in the 601XL at max gross with two big guys, half tanks and end up too far rear of CG after just 30 minutes of flight. This prompted me to move my engine forward 4 inches, even though it meant reworking all the wiring and hoses and throttle cable and cowling etc.



So maybe I don't know jack shine about the weight of paint ... but I've learned more than I care to know about the W&B on the 601XL using the stock 912S motor mount from Zenair. 



 	  gboothe(at)calply.com wrote: 	
		  Don't be offended. If your every word was not dissected and examined you would think you posted to the wrong list. I'm sure the silent majority will find your spreadsheet quite useful, as is. I do.

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

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