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Weight & Balance for certification of Mark3x

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JRatcli256(at)aol.com
Guest

Posted: Tue Aug 04, 2009 6:47 am Post subject: Weight & Balance for certification of Mark3x

The plans for the Mark3x say the bottom of the wing should be at +9 deg.  when doing the W&B.

  

 The form that comes with the certification guide from EAA states the  aircraft should be weighted in level flight attitude.

  

 My question to those who've had their Mark3x inspected ------ What  attitude was used for your certification W&B ?

  

 And if it was level flight attitude, what is the level flight  attitude.

  

 John Ratcliffe

NeilsenRM(at)comcast.net
Guest

Posted: Tue Aug 04, 2009 7:41 am Post subject: Weight & Balance for certification of Mark3x

John

  

 The assumption is depending on your speed/density  altitude/weight, that is level flight.  



 My older MKIIIC W&B plans show the same thing. My plane was inspected  using that guideline. Also you don't show that information on your weight and  balance sheet.

  

 Rick Neilsen

 Redrive VW powered MKIIIC

  

  

 [quote]   ---

zeprep251(at)aol.com
Guest

Posted: Tue Aug 04, 2009 8:56 am Post subject: Weight & Balance for certification of Mark3x

John,

  Raise the tail until the horizontal is level.That should make the wings at 9 degrees,but I think the tail is the place to start.

 

   

 

   

 

 --

aslsa.rng(at)gmail.com
Guest

Posted: Tue Aug 04, 2009 11:13 am Post subject: Weight & Balance for certification of Mark3x

If you wanted to do some relatively simple math using the lift coefficient curve for a relatively thick flat bottomed air foil and the cruise speed of a Mk III you'd get the right result at an AOA of, wait for it, around 9 degrees. Set it just like the plans say, it works.

Rick Girard



On Tue, Aug 4, 2009 at 11:55 AM,  <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

 [quote]  John,

  Raise the tail until the horizontal is level.That should make the wings at 9 degrees,but I think the tail is the place to start.

 

   

 

   

 

 --

slyck(at)frontiernet.net
Guest

Posted: Tue Aug 04, 2009 1:35 pm Post subject: Weight & Balance for certification of Mark3x

The flat bottom doesn't necessarily dictate AOA at cruise.  Having many hours in an aeronca I can attest to the fact that itcruised on the step with the bottom of the wing pointed slightly down.  Of the features on the Kolb wing that prevents this

are:  the thickness max is more forward of the aeronca's NACA 4412 and the nose is much sharper at the bottom of the leading edge.

The piper J3 airfoil is closer with the max thickness position and the flight characteristics are more like the Kolb, high lift and draggy.

(albeit a delightful low speed craft)

If you want to pick up some cruise speed with very little sacrifice in other categories, build your Kolb wing with a much more blunt nose.

That will give you more symmetry and better airflow.  When you pull back and point upstairs the wind will take the easy way out and go underneath.

BB

as Ripley said, believe it or not



On 4, Aug 2009, at 3:12 PM, Richard Girard wrote:

[quote]If you wanted to do some relatively simple math using the lift coefficient curve for a relatively thick flat bottomed air foil and the cruise speed of a Mk III you'd get the right result at an AOA of, wait for it, around 9 degrees. Set it just like the plans say, it works.

Rick Girard



On Tue, Aug 4, 2009 at 11:55 AM,  <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

 [quote]  John,

  Raise the tail until the horizontal is level.That should make the wings at 9 degrees,but I think the tail is the place to start.

 

  

 

  

 

 --

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Wed Aug 05, 2009 3:26 pm Post subject: Re: Weight & Balance for certification of Mark3x

I don't have the book in front of me ,but how we did it to my m3x was  we put a level from the trailing edge of the wing (not the end of the flap) and brought the forword end of the level down 7 3/4 inches from the bottom of the leading edge of the wing,the raised the tail until the bubble was level.That was level flight.then dropped a plumb line down from the leading edge and that is where you measured from for all your stations.



chris ambrose

M3X/jab  43.3

N327cs

Possums

Joined: 03 Nov 2007
Posts: 247

Posted: Wed Aug 05, 2009 3:43 pm Post subject: Weight & Balance for certification of Mark3x

At 07:26 PM 8/5/2009, you wrote:

 	  Quote: 	
		  



I don't have the book in front of me ,but how we did it to my m3x 

was  we put a level from the trailing edge of the wing (not the end 

of the flap) and brought the forword end of the level down 7 3/4 

inches from the bottom of the leading edge of the wing,the raised 

the tail until the bubble was level.That was level flight.then 

dropped a plumb line down from the leading edge and that is where 

you measured from for all your stations.



chris ambrose

M3X/jab  43.3

N327cs




	


Here's how we used to do it.

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_________________
Possum

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Wed Aug 05, 2009 4:01 pm Post subject: Re: Weight & Balance for certification of Mark3x

That's it !  I couldn't remember exactly  if it was 7 1/2 or 7  3/4....but that is how I did it..



chris ambrose

JRatcli256(at)AOL.COM
Guest

Posted: Wed Aug 05, 2009 5:24 pm Post subject: Weight & Balance for certification of Mark3x

Photos of earlier models of the Mark3x show the bottom front of  the wing set above the tubing at the top of the windshield and the front top of  the horz. stabilizer at the top of the boom tube. What the angles are, I don't  know.

  

 For that reason, what attitude that puts the aircraft in when the wing is  at 9 deg. for W&B calculations, I don't know. It may be in level  flight attitude. Also the horz. stabilizer may be level ???  Can  someone supply the angles for reference ?

  

 My Mark3x, with the engine mount level --- Wing incidence is +2.8 deg.  (Front bottom of wing is about 3" below the top of the windshield  tubing bow), the  horz stabilizer is at -4.8 deg. ( the bottom of the  front tube of the stabilizer 1/4" above centerline of the boom tube). I think  these changes were made to help alleviate the problem of "Kolb Quit"

  

 When I position the aircraft at 9 deg. for W&B calculations, the  attitude appears to me, to be in a three point landing attitude with the tail  wheel about 5" above the floor.

 Surely this isn't level flight attitude.

  

 If I put the horz. stabilizer level, that puts the bottom of the wing  at -2 deg.

  

 Because of the change in wing and horz. stabilizer incidences, wouldn't  that change the angle of the wing for W&B  calculations ?

  

 Again your thoughts ???

  

 John Ratcliffe

 

  [quote][b]

russ(at)rkiphoto.com
Guest

Posted: Wed Aug 05, 2009 5:40 pm Post subject: Weight & Balance for certification of Mark3x

Chris

How long was your level?



On Aug 5, 2009, at 7:26 PM, ces308 wrote:



 	  Quote: 	
		   



 I don't have the book in front of me ,but how we did it to my m3x  

 was  we put a level from the trailing edge of the wing (not the end  

 of the flap) and brought the forword end of the level down 7 3/4  

 inches from the bottom of the leading edge of the wing,the raised  

 the tail until the bubble was level.That was level flight.then  

 dropped a plumb line down from the leading edge and that is where  

 you measured from for all your stations.



 chris ambrose

 M3X/jab  43.3

 N327cs





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 56248#256248

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Wed Aug 05, 2009 5:49 pm Post subject: Re: Weight & Balance for certification of Mark3x

It was a 4 feet level....it went from the wing trailing edge to the leading edge.  I would not go buy the horz stab....do the wing thing...my tali wheel was up quite a ways...



chris ambrose

slyck(at)frontiernet.net
Guest

Posted: Wed Aug 05, 2009 6:40 pm Post subject: Weight & Balance for certification of Mark3x

On 5, Aug 2009, at 9:23 PM, JRatcli256(at)aol.com (JRatcli256(at)aol.com) wrote:

 	  Quote: 	
		   

When I position the aircraft at 9 deg. for W&B calculations, the attitude appears to me, to be in a three point landing attitude with the tail wheel about 5" above the floor.

Surely this isn't level flight attitude.

 

	




Wouldn't this position be close to a normal attitude near stall?   That's what W&B is all about.

BB

 [quote][b]

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Wed Aug 05, 2009 6:59 pm Post subject: Re: Weight & Balance for certification of Mark3x

you will never full stall land that airplane....atleast not without  slamming the mains on the ground....don't second guess the instruction manual...



chris ambrose

mdnanwelch7(at)hotmail.co
Guest

Posted: Thu Aug 06, 2009 8:43 am Post subject: Weight & Balance for certification of Mark3x

John C

  

   I have done some research on this subject C and have some thoughts C too.  They will have to wait till this evening C tho C when I have more time......I've just came in for a work break (from building my house).

  

   More later....

  

 Mike Welch

 MkIII

 

  From: JRatcli256(at)aol.com

Date: Wed C 5 Aug 2009 21:23:44 -0400

Subject: Re: Weight & Balance for certification of Mark3x

To: kolb-list(at)matronics.com



 Photos of earlier models of the Mark3x show the bottom front of the wing set above the tubing at the top of the windshield and the front top of the horz. stabilizer at the top of the boom tube. What the angles are C I don't know.

  

 For that reason C what attitude that puts the aircraft in when the wing is at 9 deg. for W&B calculations C I don't know. It may be in level flight attitude. Also the horz. stabilizer may be level ???  Can someone supply the angles for reference ?

  

 My Mark3x C with the engine mount level --- Wing incidence is +2.8 deg. (Front bottom of wing is about 3" below the top of the windshield tubing bow) C the  horz stabilizer is at -4.8 deg. ( the bottom of the front tube of the stabilizer 1/4" above centerline of the boom tube). I think these changes were made to help alleviate the problem of "Kolb Quit"

  

 When I position the aircraft at 9 deg. for W&B calculations C the attitude appears to me C to be in a three point landing attitude with the tail wheel about 5" above the floor.

 Surely this isn't level flight attitude.

  

 If I put the horz. stabilizer level C that puts the bottom of the wing at -2 deg.

  

 Because of the change in wing and horz. stabilizer incidences C wouldn't that change the angle of the wing for W&B  calculations ?

  

 Again your thoughts ???

  

 John Ratcliffe

 

  

 	  Quote: 	
		  



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