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yellowbird1

Joined: 01 Nov 2012
Posts: 88

Posted: Sat Aug 31, 2013 5:30 pm Post subject: Kolb Xtra weight. & balance

I have recently purchased a Kolb Xtra and have installed a BRS on it. I had to jump through a few hurdles and have yet to fly it. Now that the BRS is installed I am unable to get the correct CG. 

According to the information I have the CG should between 11.5% and 35% of the chord of the wing, in my case the wing chord is 66inches. Which equates to a CG range of 7.5 - 23.1 inches aft datum. However, I'm getting about 28. 

I used bathroom scales to measure, but could only get one per wheel to work, I was unable to get two scales per main wheel to work. When I put a board across the two only one scale would notice the weight.



So my questions are:

Is the CG range and/or the %s used (11.5 and 35) correct ?



Could the weights be that far off?  

Could the bathroom scales be that much of POSs?

The total AF weight from the previous owner's W&B was 601lbs and mine came out to be  (on the last weighting as I have done at least 1/2 dozen) was 751lbs.  As far as I can tell the previous owner added tundra tires after his last W&B and the weight of the BRS is only 18.6 lbs (which may not include the mounting hardware. But I don't think that adds up to 150lbs.



Any help, suggestions, or comments would be greatly appreciated. 

I really to get in the air!



Brad Nation

Xtra N952DK

<pre><b><font size=2 color="#000000" face="courier new,courier">

_________________
Brad Nation,
Albuquerque, NM
MK3 Xtra

rowedenny

Joined: 09 Mar 2008
Posts: 338
Location: Western PA

Posted: Sat Aug 31, 2013 6:01 pm Post subject: Kolb Xtra weight. & balance

Without good scales you are pissing into the wind, both those weights sound high, my Mk3 weighs 475 pounds but I really built it light and have a light two stroke engine, I guess the Xtra have a lot more bells and whistles. I hope to add some weight to it in the form of a 912 engine someday.



Dennis "Skid" Rowe

Mk3, 690L-70, Leechburg, PA



On Aug 31, 2013, at 9:29 PM, <nationcap(at)comcast.net> wrote:



 	  Quote: 	
		   I have recently purchased a Kolb Xtra and have installed a BRS on it. I had to jump through a few hurdles and have yet to fly it. Now that the BRS is installed I am unable to get the correct CG. 

 According to the information I have the CG should between 11.5% and 35% of the chord of the wing, in my case the wing chord is 66inches. Which equates to a CG range of 7.5 - 23.1 inches aft datum. However, I'm getting about 28. 

 I used bathroom scales to measure, but could only get one per wheel to work, I was unable to get two scales per main wheel to work. When I put a board across the two only one scale would notice the weight.

 

 So my questions are:

 Is the CG range and/or the %s used (11.5 and 35) correct ?

 

 Could the weights be that far off?  

 Could the bathroom scales be that much of POSs?

 The total AF weight from the previous owner's W&B was 601lbs and mine came out to be  (on the last weighting as I have done at least 1/2 dozen) was 751lbs.  As far as I can tell the previous owner added tundra tires after his last W&B and the weight of the BRS is only 18.6 lbs (which may not include the mounting hardware. But I don't think that adds up to 150lbs.

 

 Any help, suggestions, or comments would be greatly appreciated. 

 I really to get in the air!

 

 Brad Nation

 Xtra N952DK

 <pre><b><font size=2 color="#000000" face="courier new,courier">

 

 

 </b></font></pre>

colin.scott.hudson(at)gma
Guest

Posted: Sun Sep 01, 2013 6:47 pm Post subject: Kolb Xtra weight. & balance

Brad I got my builders manual for my Mark 3 X-tra out and your numbers are a little off, close but off.  Your mixing your % and inches.  This is what my manual states.  The chord of an airfoil is the straight line distance from the leading edge to the trailing edge.  Our wings have a flat bottom surface so the chord is measured along it.  The average wing chord is 58"  (You stated yours was 66", quite a difference.)  and the airplane will be safe to fly if the center of gravity is between 20% and 35% of the wing chord as measured from datum (the leading edge).  20% chord is 11.6" aft of the leading edge and 35% chord is 20.3".  The airplane is in balance if the CG falls between 11.6 and 20.3" aft of the leading edge of the wing.  For reference the mounting tab on the wing root for the main spar is 18" aft of the leading edge.  You said your empty weight came out to be 751.  My Mark3Xtra with a Jabiru engine and canister BRS has an empty weight of 567 lbs.  The canister system weight may be a little more than the VLS, it weighs 21 lbs 4 oz.  Here's what my manual says about weighing your aircraft: The weight and balance can be done in one weighing if you have two high capacity scales and a bathroom scale or five bathroom scales (two for each main wheel and one for the tail).  This is the easiest and you are less likely to make a mistake.  When using two scales for each main wheel, bridge them with a board and pace the wheel in the center.  Add both scale readins together and subtract the weight of the board from your totals.  If you are limited to three scales or less, block up the wheel(s) not on the scales as needed to level the airplane and read the weight one wheel at a time.  

 The basis weight and balance equation is Weight X Distance = Moment

1. Weigh each wheel

2.  Multiply each wheel weight by its distance from the datum point.

3.  Add the three resulting moments together.

 4,  Divide the resultant moment by the total empty weigh (the sum of the readings of all scales.)  This will give the distance of the center of gravity (CG) from the datum.

I know this is a little lengthy, but hope it helps you some.

Colin

Colin S. Hudson

A&P/ ATP

N424AL

On Sat, Aug 31, 2013 at 9:00 PM, Dennis Rowe <rowedenny(at)windstream.net (rowedenny(at)windstream.net)> wrote:

 [quote]--> Kolb-List message posted by: Dennis Rowe <rowedenny(at)windstream.net (rowedenny(at)windstream.net)>

 Without good scales you are pissing into the wind, both those weights sound high, my Mk3 weighs 475 pounds but I really built it light and have a light two stroke engine, I guess the Xtra have a lot more bells and whistles. I hope to add some weight to it in the form of a 912 engine someday.

 Dennis "Skid" Rowe

 Mk3, 690L-70, Leechburg, PA

 On Aug 31, 2013, at 9:29 PM, <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

 > I have recently purchased a Kolb Xtra and have installed a BRS on it. I had to jump through a few hurdles and have yet to fly it. Now that the BRS is installed I am unable to get the correct CG.

 > According to the information I have the CG should between 11.5% and 35% of the chord of the wing, in my case the wing chord is 66inches. Which equates to a CG range of 7.5 - 23.1 inches aft datum. However, I'm getting about 28.

  > I used bathroom scales to measure, but could only get one per wheel to work, I was unable to get two scales per main wheel to work. When I put a board across the two only one scale would notice the weight.

 >

 > So my questions are:

 > Is the CG range and/or the %s used (11.5 and 35) correct ?

 >

 > Could the weights be that far off?

 > Could the bathroom scales be that much of POSs?

 > The total AF weight from the previous owner's W&B was 601lbs and mine came out to be  (on the last weighting as I have done at least 1/2 dozen) was 751lbs.  As far as I can tell the previous owner added tundra tires after his last W&B and the weight of the BRS is only 18.6 lbs (which may not include the mounting hardware. But I don't think that adds up to 150lbs.

  >

 > Any help, suggestions, or comments would be greatly appreciated.

 > I really to get in the air!

 >

 > Brad Nation

 > Xtra N952DK

 > <pre><b><font size=2 color="#000000" face="courier new,courier">

 >

 >

 > </b></font></pre>

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rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sun Sep 01, 2013 7:08 pm Post subject: Kolb Xtra weight. & balance

Brad, First, did you put the airplane into the proper configuration when you weighed and measured. The bottom of the wing S/B at 9 degrees. While not having it set properly won't throw off the weight too much, it will throw off your measurements. 635 to 650 lb. is in range for an "X", 750 is not. If you must weigh with one scale, use a block under the other main while you weigh first one, then the other. Otherwise take it to you're nearest FBO or check with your local EAA chapter.

 Good luck

Rick Girard

do not archive



On Sat, Aug 31, 2013 at 8:29 PM,  <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

  	  Quote: 	
		  I have recently purchased a Kolb Xtra and have installed a BRS on it. I had to jump through a few hurdles and have yet to fly it. Now that the BRS is installed I am unable to get the correct CG.

  According to the information I have the CG should between 11.5% and 35% of the chord of the wing, in my case the wing chord is 66inches. Which equates to a CG range of 7.5 - 23.1 inches aft datum. However, I'm getting about 28.

  I used bathroom scales to measure, but could only get one per wheel to work, I was unable to get two scales per main wheel to work. When I put a board across the two only one scale would notice the weight.

 

 So my questions are:

 Is the CG range and/or the %s used (11.5 and 35) correct ?

 

 Could the weights be that far off?

 Could the bathroom scales be that much of POSs?

 The total AF weight from the previous owner's W&B was 601lbs and mine came out to be  (on the last weighting as I have done at least 1/2 dozen) was 751lbs.  As far as I can tell the previous owner added tundra tires after his last W&B and the weight of the BRS is only 18.6 lbs (which may not include the mounting hardware. But I don't think that adds up to 150lbs.

  

 Any help, suggestions, or comments would be greatly appreciated.

 I really to get in the air!

 

 Brad Nation

 Xtra N952DK

 <pre><b><font size=2 color="#000000" face="courier new,courier">

 

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-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx

 

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_________________
The smallest miracle right in front of you is enough to make you happy....

colin.scott.hudson(at)gma
Guest

Posted: Sun Sep 01, 2013 7:59 pm Post subject: Kolb Xtra weight. & balance

Brad something else I forgot to mention earlier.  I've used bathroom scales in the past and you have to find their pressure points.  You can't just lay a board across them.  Put a chunk of 2x4 on the spot where the scales read accurate then run you board across the two scales.  Just remember to subtract you total board weight, this is known as Tare weight.

Colin Hudson 

N424AL

Mark3Xtra

Sent from my iPhone

On Aug 31, 2013, at 9:00 PM, Dennis Rowe <rowedenny(at)windstream.net> wrote:

 	  Quote: 	

 Without good scales you are pissing into the wind, both those weights sound high, my Mk3 weighs 475 pounds but I really built it light and have a light two stroke engine, I guess the Xtra have a lot more bells and whistles. I hope to add some weight to it in the form of a 912 engine someday.

 Dennis "Skid" Rowe

 Mk3, 690L-70, Leechburg, PA

 On Aug 31, 2013, at 9:29 PM, <nationcap(at)comcast.net> wrote:

> I have recently purchased a Kolb Xtra and have installed a BRS on it. I had to jump through a few hurdles and have yet to fly it. Now that the BRS is installed I am unable to get the correct CG. 

> According to the information I have the CG should between 11.5% and 35% of the chord of the wing, in my case the wing chord is 66inches. Which equates to a CG range of 7.5 - 23.1 inches aft datum. However, I'm getting about 28. 

> I used bathroom scales to measure, but could only get one per wheel to work, I was unable to get two scales per main wheel to work. When I put a board across the two only one scale would notice the weight.

> 

> So my questions are:

> Is the CG range and/or the %s used (11.5 and 35) correct ?

> 

> Could the weights be that far off?  

> Could the bathroom scales be that much of POSs?

> The total AF weight from the previous owner's W&B was 601lbs and mine came out to be  (on the last weighting as I have done at least 1/2 dozen) was 751lbs.  As far as I can tell the previous owner added tundra tires after his last W&B and the weight of the BRS is only 18.6 lbs (which may not include the mounting hardware. But I don't think that adds up to 150lbs.

> 

> Any help, suggestions, or comments would be greatly appreciated. 

> I really to get in the air!

> 

> Brad Nation

> Xtra N952DK

> <pre><b><font size=2 color="#000000" face="courier new,courier">

> 

> 

> </b></font></pre>

racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Mon Sep 02, 2013 6:30 am Post subject: Re: Kolb Xtra weight. & balance

Oh; remember to put your ass in seat before weighing.  I am afraid that you will need someone else to read the scales.  With my lighter Firestar II, I purchased 3 flat top $10 bath scales from Walmart and had no trouble at all with weighing.  



Especially when using bathroom scales, you need to take care not to side load the scales or it will distort readings.  What I did was pick up one main wheel and gently lay it back down on the scale.  This keeps a toe error from causing a side load when rolling on to the scales (changing distance between main wheels).  



I am sure you can get one of your local stock car guys interested enough in your project to pay a visit and bring along their digital scales; the scales are very portable and easily set up.  A cold case of beer can work wonders with racers; just make sure it comes out afterwards.

_________________
Jerry King

yellowbird1

Joined: 01 Nov 2012
Posts: 88

Posted: Mon Sep 02, 2013 8:45 am Post subject: Kolb Xtra weight. & balance

If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.



I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.



Thanks shine for all the input.



Brad



Sent from Xfinity Connect Mobile App so there may be some typos.



--

_________________
Brad Nation,
Albuquerque, NM
MK3 Xtra

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Mon Sep 02, 2013 12:49 pm Post subject: Kolb Xtra weight. & balance

Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process. You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range. Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

Rick Girard

 



On Mon, Sep 2, 2013 at 11:45 AM,  <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

[quote] If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

  

 I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

 At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

 So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

 

 Thanks shine for all the input.

 

 Brad

 

 Sent from Xfinity Connect Mobile App so there may be some typos.

 

 --

_________________
The smallest miracle right in front of you is enough to make you happy....

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Mon Sep 02, 2013 1:00 pm Post subject: Kolb Xtra weight. & balance

Dang it, hit return before I was ready. Attached is the spread sheet for an Xtra. Put 0 into pilot weight in the last section and you'll see the CG is too far aft. You must figure in the pilot weight at some minimum to get the CG into range. 



Rick



On Mon, Sep 2, 2013 at 3:49 PM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

 [quote]Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process.  You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range.  Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

Rick Girard

  



On Mon, Sep 2, 2013 at 11:45 AM,  <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

 [quote] If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

   

 I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

 At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

 So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

 

 Thanks shine for all the input.

 

 Brad

 

 Sent from Xfinity Connect Mobile App so there may be some typos.

 

 --

Mark_IIIX_W_and_B.xlsx

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Mark_IIIX_W_and_B.xlsx

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_________________
The smallest miracle right in front of you is enough to make you happy....

yellowbird1

Joined: 01 Nov 2012
Posts: 88

Posted: Sun Sep 08, 2013 6:12 pm Post subject: Kolb Xtra weight. & balance

I guess I didn't understand the process. I crunched some numbers using my weight as the pilot weight and indeed it brought the CG within range. As I didn't have the correct ARM I'll be heading out to the hanger to get the real measurements and go from there.

Thanks for the visual aid spread sheet.

I measured the bottom of the wing including the flap to be 66", w/o flap, 50". I looked at the builder's notes and his wing measurements are the same. Looking back at my post yes I did mix up the inches and %. (Probably didn't help doing the typing on my iPhone. )

My Xtra has a Rotax 912 80 hp, BRS VLS ( it weights 18.6 lbs), tundra tires, basic instruments, nothing out of the ordinary, as far as I can tell from my limited experience with Xtras, so I agree that the weight is high. The question is why, we're the scales crappy, was I maxing out the scales, did I weigh it incorrectly, or does it really weigh that much.

When I weighed it I raised the tail so that the wing trailing edge was 7.5 inches lower than he leading edge. I lowered the wheels onto the scales vs. rolling onto them. I repeated the process for each wheel at least 4 times until I got a couple consistent weights on each wheel.

It seems that I need to go and remeasure and get an accurate higher capacity set of scales.

Sent from my iPad

Brad

On Sep 2, 2013, at 15:00, Richard Girard <aslsa.rng(at)gmail.com> wrote:

[quote] Dang it, hit return before I was ready. Attached is the spread sheet for an Xtra. Put 0 into pilot weight in the last section and you'll see the CG is too far aft. You must figure in the pilot weight at some minimum to get the CG into range.

 Rick

 On Mon, Sep 2, 2013 at 3:49 PM, Richard Girard <aslsa.rng(at)gmail.com> wrote:

> Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process. 

> You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range.

> Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

> 

> Rick Girard

> 

> 

> On Mon, Sep 2, 2013 at 11:45 AM, <nationcap(at)comcast.net> wrote:

>> If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

>> 

>> I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

>> At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

>> So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

>> 

>> Thanks shine for all the input.

>> 

>> Brad

>> 

>> Sent from Xfinity Connect Mobile App so there may be some typos.

>> 

>> --

_________________
Brad Nation,
Albuquerque, NM
MK3 Xtra

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Mon Sep 09, 2013 8:32 am Post subject: Kolb Xtra weight. & balance

Brad, When I was working on 125KP Travis told me that the average "X" came in at an empty weight of 650 lb. As I recall 125KP was 655 lb. when I put it on a weight reduction plan and I was able to get it down to 615. That was a 582 powered airplane. Add 35 to 40 lb. for the 912 and you're back up in the 660 lb weight range. The wing chord includes the flaps, i.e. it is 66".

Rick



On Tue, Sep 3, 2013 at 7:37 PM, Brad Nation <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

 [quote]I guess I didn't understand the process. I crunched some numbers using my weight as the pilot weight and indeed it brought the CG within range. As I didn't have the correct ARM I'll be heading out to the hanger to get the real measurements and go from there.

 



Thanks for the visual aid spread sheet.



I measured the bottom of the wing including the flap to be 66", w/o flap, 50". I looked at the builder's notes and his wing measurements are the same. Looking back at my post yes I did mix up the inches and %. (Probably didn't help doing the typing on my iPhone. )

 My Xtra has a Rotax 912 80 hp, BRS VLS ( it weights 18.6 lbs), tundra tires, basic instruments, nothing out of the ordinary, as far as I can tell from my limited experience with Xtras, so I agree that the weight is high. The question is why, we're the scales crappy, was I maxing out the scales, did I weigh it incorrectly, or does it really weigh that much.

 When I weighed it I raised the tail so that the wing trailing edge was 7.5 inches lower than he leading edge. I lowered the wheels onto the scales vs. rolling onto them. I repeated the process for each wheel at least 4 times until I got a couple consistent weights on each wheel.

 



It seems that I need to go and remeasure and get an accurate higher capacity set of scales.

Sent from my iPad



Brad

On Sep 2, 2013, at 15:00, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

 



[quote]Dang it, hit return before I was ready. Attached is the spread sheet for an Xtra. Put 0 into pilot weight in the last section and you'll see the CG is too far aft. You must figure in the pilot weight at some minimum to get the CG into range.  



Rick



On Mon, Sep 2, 2013 at 3:49 PM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

  [quote]Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process.   You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range.   Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

Rick Girard

   



On Mon, Sep 2, 2013 at 11:45 AM,  <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

  [quote] If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

    

 I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

 At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

 So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

 

 Thanks shine for all the input.

 

 Brad

 

 Sent from Xfinity Connect Mobile App so there may be some typos.

 

 --

_________________
The smallest miracle right in front of you is enough to make you happy....

yellowbird1

Joined: 01 Nov 2012
Posts: 88

Posted: Tue Sep 10, 2013 5:25 pm Post subject: Kolb Xtra weight. & balance

Rick,

That weight of 660 lb seems about what it should be,  I'm thinking/hoping that the 751 lb that it weighted out on the last measuring is incorrect as I was getting such a large range of weights that I think the scales I was using were not accurate. At 750 lb doesn't leave me much caring capacity for passengers, fuel, or baggage. So I'm trying to acquire a set of military rolling stock scales or some certified scales and re-weigh it.



Im not ignoring all the help from the the Kolb forum, I'm just in a holding pattern until I get some better scales and get a more accurate weight, then I'll update the forum.



Thanks for all the input from everyone who weighed in with help. (pun intended)



Sent from my iPad



Brad



On Sep 9, 2013, at 10:32, Richard Girard <aslsa.rng(at)gmail.com> wrote:



[quote] Brad, When I was working on 125KP Travis told me that the average "X" came in at an empty weight of 650 lb. As I recall 125KP was 655 lb. when I put it on a weight reduction plan and I was able to get it down to 615. That was a 582 powered airplane. Add 35 to 40 lb. for the 912 and you're back up in the 660 lb weight range.

 The wing chord includes the flaps, i.e. it is 66".

 

 Rick

 

 

 On Tue, Sep 3, 2013 at 7:37 PM, Brad Nation <nationcap(at)comcast.net> wrote:

> I guess I didn't understand the process. I crunched some numbers using my weight as the pilot weight and indeed it brought the CG within range. As I didn't have the correct ARM I'll be heading out to the hanger to get the real measurements and go from there.

> 

> Thanks for the visual aid spread sheet.

> 

> I measured the bottom of the wing including the flap to be 66", w/o flap, 50". I looked at the builder's notes and his wing measurements are the same. Looking back at my post yes I did mix up the inches and %. (Probably didn't help doing the typing on my iPhone. )

> My Xtra has a Rotax 912 80 hp, BRS VLS ( it weights 18.6 lbs), tundra tires, basic instruments, nothing out of the ordinary, as far as I can tell from my limited experience with Xtras, so I agree that the weight is high. The question is why, we're the scales crappy, was I maxing out the scales, did I weigh it incorrectly, or does it really weigh that much.

> When I weighed it I raised the tail so that the wing trailing edge was 7.5 inches lower than he leading edge. I lowered the wheels onto the scales vs. rolling onto them. I repeated the process for each wheel at least 4 times until I got a couple consistent weights on each wheel.

> 

> It seems that I need to go and remeasure and get an accurate higher capacity set of scales.

> 

> Sent from my iPad

> 

> Brad

> 

> On Sep 2, 2013, at 15:00, Richard Girard <aslsa.rng(at)gmail.com> wrote:

> 

>> Dang it, hit return before I was ready. Attached is the spread sheet for an Xtra. Put 0 into pilot weight in the last section and you'll see the CG is too far aft. You must figure in the pilot weight at some minimum to get the CG into range.

>> 

>> Rick

>> 

>> 

>> On Mon, Sep 2, 2013 at 3:49 PM, Richard Girard <aslsa.rng(at)gmail.com> wrote:

>>> Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process. 

>>> You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range.

>>> Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

>>> 

>>> Rick Girard

>>> 

>>> 

>>> On Mon, Sep 2, 2013 at 11:45 AM, <nationcap(at)comcast.net> wrote:

>>>> If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

>>>> 

>>>> I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

>>>> At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

>>>> So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

>>>> 

>>>> Thanks shine for all the input.

>>>> 

>>>> Brad

>>>> 

>>>> Sent from Xfinity Connect Mobile App so there may be some typos.

>>>> 

>>>> --

_________________
Brad Nation,
Albuquerque, NM
MK3 Xtra

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Wed Sep 11, 2013 5:26 pm Post subject: Kolb Xtra weight. & balance

Brad, Do you have a local EAA Chapter? Ask around at the airport, someone has to have a set of scales. I bought a set of go kart racing scales that can handle up to 500 lb. each.



Rick

 

On Tue, Sep 10, 2013 at 8:24 PM, Brad Nation <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

 [quote]Rick,

That weight of 660 lb seems about what it should be,  I'm thinking/hoping that the 751 lb that it weighted out on the last measuring is incorrect as I was getting such a large range of weights that I think the scales I was using were not accurate. At 750 lb doesn't leave me much caring capacity for passengers, fuel, or baggage. So I'm trying to acquire a set of military rolling stock scales or some certified scales and re-weigh it.

 



Im not ignoring all the help from the the Kolb forum, I'm just in a holding pattern until I get some better scales and get a more accurate weight, then I'll update the forum.

 Thanks for all the input from everyone who weighed in with help. (pun intended)



Sent from my iPad



Brad



On Sep 9, 2013, at 10:32, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

 



[quote]Brad, When I was working on 125KP Travis told me that the average "X" came in at an empty weight of 650 lb. As I recall 125KP was 655 lb. when I put it on a weight reduction plan and I was able to get it down to 615. That was a 582 powered airplane. Add 35 to 40 lb. for the 912 and you're back up in the 660 lb weight range.  The wing chord includes the flaps, i.e. it is 66".

Rick



On Tue, Sep 3, 2013 at 7:37 PM, Brad Nation <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

  



[quote] I guess I didn't understand the process. I crunched some numbers using my weight as the pilot weight and indeed it brought the CG within range. As I didn't have the correct ARM I'll be heading out to the hanger to get the real measurements and go from there.

  



Thanks for the visual aid spread sheet.



I measured the bottom of the wing including the flap to be 66", w/o flap, 50". I looked at the builder's notes and his wing measurements are the same. Looking back at my post yes I did mix up the inches and %. (Probably didn't help doing the typing on my iPhone. )

  My Xtra has a Rotax 912 80 hp, BRS VLS ( it weights 18.6 lbs), tundra tires, basic instruments, nothing out of the ordinary, as far as I can tell from my limited experience with Xtras, so I agree that the weight is high. The question is why, we're the scales crappy, was I maxing out the scales, did I weigh it incorrectly, or does it really weigh that much.

  When I weighed it I raised the tail so that the wing trailing edge was 7.5 inches lower than he leading edge. I lowered the wheels onto the scales vs. rolling onto them. I repeated the process for each wheel at least 4 times until I got a couple consistent weights on each wheel.

  



It seems that I need to go and remeasure and get an accurate higher capacity set of scales.

Sent from my iPad



Brad

On Sep 2, 2013, at 15:00, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

  



[quote]Dang it, hit return before I was ready. Attached is the spread sheet for an Xtra. Put 0 into pilot weight in the last section and you'll see the CG is too far aft. You must figure in the pilot weight at some minimum to get the CG into range.   



Rick



On Mon, Sep 2, 2013 at 3:49 PM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

   [quote]Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process.    You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range.    Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

Rick Girard

    



On Mon, Sep 2, 2013 at 11:45 AM,  <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

   [quote] If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

     

 I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

 At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

 So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

 

 Thanks shine for all the input.

 

 Brad

 

 Sent from Xfinity Connect Mobile App so there may be some typos.

 

 --

_________________
The smallest miracle right in front of you is enough to make you happy....

neilsenrm(at)gmail.com
Guest

Posted: Wed Sep 11, 2013 6:40 pm Post subject: Kolb Xtra weight. & balance

Hey guys try this. I used three cheep bathroom scales to weigh my plane but first I calibrated them. I used a high quality balance beam scale to weigh me. It seems like I even put so weight on the scale to increase my weight a bit. Then I got on two of the scales that I would use as the main gear scales and made sure they showed the same weight. You need to step on and off the scales a few times to make sure that it will return to the calibrated weight each time. For the tail wheel I used a known weight closer to the estimated tail weight. With the plane in the hanger with the doors closed I put the plane on the scales and lifted the tail on boxes to get it at the correct height for the required weighing position and slid the tail wheel scale in place. Cheep and fairly accurate. I used the instructions that came with the kit for balance of the pilot and passenger weight to figure minimum and maximum weight to stay in the CG limits. 



My empty weight is now 598LBS. I was real careful to limit washers, no more than three threads showing on any bolt, anything not necessary got cut off and drilling hundreds of holes in non structural parts. 

 



Rick Neilsen

1st Redrive VW Powered MKIIIC



On Wed, Sep 11, 2013 at 9:26 PM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

 [quote]Brad, Do you have a local EAA Chapter? Ask around at the airport, someone has to have a set of scales. I bought a set of go kart racing scales that can handle up to 500 lb. each. 



Rick

 

On Tue, Sep 10, 2013 at 8:24 PM, Brad Nation <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

  



[quote]Rick,

That weight of 660 lb seems about what it should be,  I'm thinking/hoping that the 751 lb that it weighted out on the last measuring is incorrect as I was getting such a large range of weights that I think the scales I was using were not accurate. At 750 lb doesn't leave me much caring capacity for passengers, fuel, or baggage. So I'm trying to acquire a set of military rolling stock scales or some certified scales and re-weigh it.

  



Im not ignoring all the help from the the Kolb forum, I'm just in a holding pattern until I get some better scales and get a more accurate weight, then I'll update the forum.

  Thanks for all the input from everyone who weighed in with help. (pun intended)



Sent from my iPad



Brad



On Sep 9, 2013, at 10:32, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

  



[quote]Brad, When I was working on 125KP Travis told me that the average "X" came in at an empty weight of 650 lb. As I recall 125KP was 655 lb. when I put it on a weight reduction plan and I was able to get it down to 615. That was a 582 powered airplane. Add 35 to 40 lb. for the 912 and you're back up in the 660 lb weight range.   The wing chord includes the flaps, i.e. it is 66".

Rick



On Tue, Sep 3, 2013 at 7:37 PM, Brad Nation <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

   



[quote]  I guess I didn't understand the process. I crunched some numbers using my weight as the pilot weight and indeed it brought the CG within range. As I didn't have the correct ARM I'll be heading out to the hanger to get the real measurements and go from there.

   



Thanks for the visual aid spread sheet.



I measured the bottom of the wing including the flap to be 66", w/o flap, 50". I looked at the builder's notes and his wing measurements are the same. Looking back at my post yes I did mix up the inches and %. (Probably didn't help doing the typing on my iPhone. )

   My Xtra has a Rotax 912 80 hp, BRS VLS ( it weights 18.6 lbs), tundra tires, basic instruments, nothing out of the ordinary, as far as I can tell from my limited experience with Xtras, so I agree that the weight is high. The question is why, we're the scales crappy, was I maxing out the scales, did I weigh it incorrectly, or does it really weigh that much.

   When I weighed it I raised the tail so that the wing trailing edge was 7.5 inches lower than he leading edge. I lowered the wheels onto the scales vs. rolling onto them. I repeated the process for each wheel at least 4 times until I got a couple consistent weights on each wheel.

   



It seems that I need to go and remeasure and get an accurate higher capacity set of scales.

Sent from my iPad



Brad

On Sep 2, 2013, at 15:00, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

   



[quote]Dang it, hit return before I was ready. Attached is the spread sheet for an Xtra. Put 0 into pilot weight in the last section and you'll see the CG is too far aft. You must figure in the pilot weight at some minimum to get the CG into range.    



Rick



On Mon, Sep 2, 2013 at 3:49 PM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

    [quote]Brad, Okay, I don't understand what you're saying here. Are you worried that the empty CG is too far aft? If that's the case you don't understand the process.     You HAVE to know the arm to the pilot seat. With that info you can then calculate the minimum pilot weight, in order to get the CG into the aft end of it's range, and maximum pilot and passenger weight to keep the CG from running out the forward end of the range.     Consider the Blanik L-13 sailplane. It's empty CG is at 78% of chord. Put a 150 lb pilot into the front seat and the loaded CG comes into the aft end of the range.

Rick Girard

     



On Mon, Sep 2, 2013 at 11:45 AM,  <nationcap(at)comcast.net (nationcap(at)comcast.net)> wrote:

    [quote] If I add me to the weight then I'm not calculating the empty weight and the CG be off, even though it's not within range now which is the problem. I haven't measured the arm for the seats so I don't know how much off it will be. But just looking at it it looks like the seats are pretty close to the datum point.

      

 I tried to using regular scales but they were very inaccurate ,  I lastly used two digital bathroom scales with a 2x6 but I could only get one of the scales to register.

 At first I rolled onto the scales but I wasn't confident in the reading that I started over and lowered the wheels onto the scales. But even then I was getting inconsistent readings.

 So for now the weight seems heavy with an aft out of range CG.  As for adding the pilot to the basic equation, I'll crunch some numbers and see if that might  make a difference.

 

 Thanks shine for all the input.

 

 Brad

 

 Sent from Xfinity Connect Mobile App so there may be some typos.

 

 --

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