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Heavy engine and Horiz. stab

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grant.corriveau(at)TELUS.
Guest

Posted: Thu Nov 13, 2008 7:18 am Post subject: Heavy engine and Horiz. stab

I'm confused by the comments regarding the engine mass and the  

horizontal stab installed angle.



Isn't the engine mass counter-balanced during the construction by  

final placement of the battery(s) to maintain the Weight & Balance  

inside the acceptable envelope?  Once this is accomplished there is  

no need to consider "adjusting" the horizontal stab to account for  

the engine weight, is there?



Curious in Canada

Grant

601 HDS / CAM100 (heavy but worth it)

ideaz1(at)sbcglobal.net
Guest

Posted: Thu Nov 13, 2008 7:42 am Post subject: Heavy engine and Horiz. stab

Yup, you are on the right track here. the horiz stab is used to change pitch 

angle. If you are nose heavy it must be counteracted by down force on the 

horiz stab/ elevator, efectively doubling the weight that is off balance. In 

a perfect world there would be 0lbs. of downforce in straight and level 

flight. Our job is to come as close as we can by balancing the weight before 

flight.

Dirk

---

notsew_evets(at)frontiern
Guest

Posted: Thu Nov 13, 2008 8:20 am Post subject: Heavy engine and Horiz. stab

But, But, but what about flying wings ?  These dont have a horizontal 

stablizer....

My son has a EZE that doest have a H.S.  It has two flying surfaces.  So 

does the flying flea from the 1930s....

---

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Nov 13, 2008 9:17 am Post subject: Heavy engine and Horiz. stab

In the real world, you need a certain amount of down force on the tail  

for adequate pitch stability. The correct amount of down force will  

cause the airplane to return straight and level flight at the trimmed  

airspeed in about two oscillations after a disturbance. That would be  

pretty hard to achieve with zero down force. On the other hand,  

depending on the mission of the airplane, you might want more or less  

pitch stability



Ideally, in straight and level flight at cruising speed the trim tab  

and elevator should be in their neutral position and the angle of  

incidence of the stabilizer should provide enough down force for  

acceptable pitch stability.



On Nov 13, 2008, at 10:41 AM, Dirk Zahtilla wrote:



[quote] 

 >



 Yup, you are on the right track here. the horiz stab is used to  

 change pitch angle. If you are nose heavy it must be counteracted by  

 down force on the horiz stab/ elevator, efectively doubling the  

 weight that is off balance. In a perfect world there would be 0lbs.  

 of downforce in straight and level flight. Our job is to come as  

 close as we can by balancing the weight before flight.

 Dirk

 ---

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Nov 13, 2008 9:32 am Post subject: Heavy engine and Horiz. stab

These are home built aircraft, every one is unique. No matter how  

carefully you follow the plans there will be variations from one plane  

to the next. With my airplane, after I completed it and determined  

that the CG was within the acceptable range, I still could not trim  

the airplane for hands off flight during my first few test flights. I  

corrected the problem by bringing the leading edge of the stabilizer  

down about half an inch. Now I fly with the trim tab near neutral  

position most of the time.



On Nov 13, 2008, at 10:17 AM, Grant Corriveau wrote:



 	  Quote: 	
		   

 >



 I'm confused by the comments regarding the engine mass and the  

 horizontal stab installed angle.



 Isn't the engine mass counter-balanced during the construction by  

 final placement of the battery(s) to maintain the Weight & Balance  

 inside the acceptable envelope?  Once this is accomplished there is  

 no need to consider "adjusting" the horizontal stab to account for  

 the engine weight, is there?



 Curious in Canada

 Grant

 601 HDS / CAM100 (heavy but worth it)




	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

psm(at)att.net
Guest

Posted: Thu Nov 13, 2008 9:54 am Post subject: Heavy engine and Horiz. stab

Hi Grant,



What a great question!



After scratching my head for a while and reading a half dozen or so 

responses, I have to come down on the side that a heavy engine does 

indeed require more down force from the elevator rigging.



The reason is only partly because of the heavy engine.  You are 

correct that the balance issue is resolved by repositioning the 

battery and other equipment.  Still, a heavier engine means a heavier 

empty weight.  If you hold the rest of the plane to the same weight 

(a crazy idea, but I don't know how to handle any other 

assumption)  then the lift must be more to fly level and the elevator 

must cause a higher angle of attack to get this.



Paul

XL getting close



At 07:17 AM 11/13/2008, you wrote:



 	  Quote: 	
		  I'm confused by the comments regarding the engine mass and the

horizontal stab installed angle.



Isn't the engine mass counter-balanced during the construction by

final placement of the battery(s) to maintain the Weight & Balance

inside the acceptable envelope?  Once this is accomplished there is

no need to consider "adjusting" the horizontal stab to account for

the engine weight, is there?



Curious in Canada

Grant

601 HDS / CAM100 (heavy but worth it)

hills(at)sunflower.com
Guest

Posted: Thu Nov 13, 2008 4:18 pm Post subject: Heavy engine and Horiz. stab

Ya, I know this perfect world, and they all fly canards.



Roger

--

frankroskind(at)HOTMAIL.C
Guest

Posted: Thu Nov 13, 2008 6:07 pm Post subject: Heavy engine and Horiz. stab

A heavy engine does not require more down force on the elevator if the plane is balanced correctly..  A properly balanced standard configuration airplane needs a center of mass ahead of the center of lift C which would produce a nose down pitching force if there were no force applied from the horizontal stabilizer and elevator.  The Horizontal empennage surfaces provide a downward force in order to keep rotational forces in balance.  When that force is diminished the nose pitches downward C which is what happens to a stable airplane in a stall.  The center of mass should always be in a range relataive to the datum which keeps the Center of Mass in front of the center of lift by a small margin. Too great a margin will mean that the plane will be difficult to fly and may not even rotate for takeoff.  Further C the stall speed is raised as the Center of Mass moves forward C because the lifting surface must offset the downward force at the tail.

 You need to build your airplane so the Center of Mass is within the designer's specs.  You can do that by moving the engine closer to the firewall C if possible C or by putting wieghts in the rear of the aircraft.  It is better that the weight come from equipment C but the weight could also come from mere ballast.  If you move your engine back C you may need to add some kind of spacer for the propeller for better handling and performance.

 In my opinion it would be dangerous for a non-expert simply to make the tail surfaces larger C or to pitch them at a steeper downward angle C to offset the weight of an engine.  If you intend to do something like that please consult with Zenith first C for your own safety.

 	  Quote: 	
		   Date: Thu C 13 Nov 2008 09:54:09 -0800

 To: zenith-list(at)matronics.com

 From: psm(at)att.net

 Subject: Re: Heavy engine and Horiz. stab

 --> Zenith-List message posted by: Paul Mulwitz <psm(at)att.net>

 Hi Grant C

 What a great question!

 After scratching my head for a while and reading a half dozen or so 

 responses C I have to come down on the side that a heavy engine does 

 indeed require more down force from the elevator rigging.

 The reason is only partly because of the heavy engine. You are 

 correct that the balance issue is resolved by repositioning the 

 battery and other equipment. Still C a heavier engine means a heavier 

 empty weight. If you hold the rest of the plane to the same weight 

 (a crazy idea C but I don't know how to handle any other 

 assumption) then the lift must be more to fly level and the elevator 

 must cause a higher angle of attack to get this.

 Paul

 XL getting close

 At 07:17 AM 11/13/2008 C you wrote:

 >I'm confused by the comments regarding the engine mass and the

 >horizontal stab installed angle.

 >

 >Isn't the engine mass counter-balanced during the construction by

 >final placement of the battery(s) to maintain the Weight & Balance

 >inside the acceptable envelope? Once this is accomplished there is

 >no need to consider "adjusting" the horizontal stab to account for

 >the engine weight C is there?

 >

 >Curious in Canada

 >Grant

 >601 HDS / CAM100 (h==============

See how Windows® connects the people C informationgo/119463819/direct/01/' target='_new'>Click here  [quote][b]

JohnDRead(at)aol.com
Guest

Posted: Thu Nov 13, 2008 7:04 pm Post subject: Heavy engine and Horiz. stab

Flying wings normally have a reflexed airfoil to  counteract the rotating moment of the airfoil. One of the flying surfaces  of an airplane such as the flying flea provides this.

  

     Balance is a different issue altogether. Moving the  angle of the stab to counterbalance an out of balance airplane is not possible.  The airframe has to be balanced statically about the CG, by balancing the mass  of the airframe, this is typically at 30% chord on a parallel chord such as the  CH701. If the wings have taper then the CG is typically at the Mean Aerodynamic  Chord point. This is how the CG of a flying wing would be calculated.

  

 John  Read



Phone: 303-648-3261

Fax: 303-648-3262

Cell: 719-494-4567   

  In a message dated 11/13/2008 9:20:48 A.M. Mountain Standard Time,  notsew_evets(at)frontiernet.net writes:

 [quote]-->    Zenith-List message posted by: "steve"    <notsew_evets(at)frontiernet.net>



But, But, but what about flying    wings ?  These dont have a horizontal 

stablizer....

My son has a    EZE that doest have a H.S.  It has two flying surfaces.  So 

does    the flying flea from the 1930s....

---

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Nov 14, 2008 8:34 am Post subject: Heavy engine and Horiz. stab

I agree with you on all counts but, the airplane also has to be built with the proper decalage between the wing and stabilizer. In my case, the CG was within the acceptable range and I still could not trim it out. With the CG near the aft limit I was just able to trim it with full tab deflection. With my aerospace engineering education, I determined that the solution to this situation was to re-pitch the stabilizer. I had somehow got the decalage slightly off during construction. It worked and my test flights after the correction showed the airplane had adequate pitch stability.



If we were all building our airplanes in identical rigging fixtures they would all be rigged the same. Since each one is hand built by a different individual, you can expect slight differences in the final product. It should be no surprise that the need for some small corrections might be found during the phase 1 testing.



On Nov 13, 2008, at 9:05 PM, Frank Roskind wrote:

 	  Quote: 	
		  A heavy engine does not require more down force on the elevator if the plane is balanced correctly..  A properly balanced standard configuration airplane needs a center of mass ahead of the center of lift, which would produce a nose down pitching force if there were no force applied from the horizontal stabilizer and elevator.  The Horizontal empennage surfaces provide a downward force in order to keep rotational forces in balance.  When that force is diminished the nose pitches downward, which is what happens to a stable airplane in a stall.  The center of mass should always be in a range relataive to the datum which keeps the Center of Mass in front of the center of lift by a small margin. Too great a margin will mean that the plane will be difficult to fly and may not even rotate for takeoff.  Further, the stall speed is raised as the Center of Mass moves forward, because the lifting surface must offset the downward force at the tail.

 

You need to build your airplane so the Center of Mass is within the designer's specs.  You can do that by moving the engine closer to the firewall, if possible, or by putting wieghts in the rear of the aircraft.  It is better that the weight come from equipment, but the weight could also come from mere ballast.  If you move your engine back, you may need to add some kind of spacer for the propeller for better handling and performance.

 

In my opinion it would be dangerous for a non-expert simply to make the tail surfaces larger, or to pitch them at a steeper downward angle, to offset the weight of an engine.  If you intend to do something like that please consult with Zenith first, for your own safety.

	




 -- 

Bryan Martin

N61BM, CH 601 XL, 

RAM Subaru, Stratus redrive.



 



 [quote][b]

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

grant.corriveau(at)telus.
Guest

Posted: Sat Nov 15, 2008 7:40 am Post subject: Heavy engine and Horiz. stab

Ah! Thanks, Sabrina,



I had to stop and research my aeronautical lexicon for 'decalage'   

but wikki came through (for anyone else who needs to refresh their  

theory of flight brain cells as well - http://en.wikipedia.org/wiki/ 

Decalage)



Now your discussion on the topic makes perfect sense.  Thanks again,



Happy Spaceship building,

Grant

grant.corriveau(at)TELUS.
Guest

Posted: Sat Nov 15, 2008 7:52 am Post subject: Heavy engine and Horiz. stab

Thanks Bryan,



Your discussion of this adjustment makes more sense to me now.  I  

found that the final setting of the ailerons to be very ambiguous as  

well, and I wonder if that also contributes to the differences in  

individual aircraft.  I originally found my aircraft flew a little  

nose-high in cruise.  I tweaked both my ailerons down a degree or two  

(barely noticeable visually) and it improved the situation.  My stall  

speed is now pretty close to the 'book' value as well.



All this gets me thinking of ways to further improve the STOL  

performance of my 601 (it'll never be a speed Queen and that's not  

what I bought it for anyway.)  So I might as well tweak the STOL end  

of the envelope.  I'll soon be adding the VGs as recorded in the  

online videos by Viktor (search youtube for this video: 0TPLa50Dvzg)



Happy testing

Grant

Joe Kidd

Joined: 01 Aug 2008
Posts: 15
Location: TN

Posted: Sat Nov 15, 2008 9:53 am Post subject: Heavy engine and Horiz. stab

Hah! I had to do the same thing myself as I couldn¢t remember what it meant either.  Undoubtedly we¢ll all be building away on a project a few years from now and be interrupted by a news story of some young aeronautical engineer¢s flight testing of a new design ground to orbit shuttle craft.  

JWS



 

   From: Grant Corriveau <grant.corriveau(at)telus.net>

To: zenith-list(at)matronics.com

Sent: Saturday, November 15, 2008 9:39:40 AM

Subject: Re: Zenith-List: Heavy engine and Horiz. stab



--> Zenith-List message posted by: Grant Corriveau <grant.corriveau(at)telus.net (grant.corriveau(at)telus.net)>



Ah! Thanks, Sabrina,



I had to stop and research my aeronautical lexicon for 'decalage'  but wikki came through (for anyone else who needs to refresh their theory of flight brain cells as well - http://en.wikipedia.org/wiki/Decalage)



Now your discussion on the topic makes perfect sense.  Thanks  again,



Happy Spaceship building,

Grant



         [quote][b]

ggower_99(at)yahoo.com
Guest

Posted: Sun Nov 16, 2008 5:33 pm Post subject: Heavy engine and Horiz. stab

Hi Steve,

 

When the 601 XL airplane beguined to have "the accidents"  inmediate I remembered the Flying Flea,  Now  that you mentioned the Flying Fleas from the 30's...   

 

They (the Flying Flea) are remembered not because of the great airplane they are, but because of the "ban" in England in 1936.

The stability problem was solved in 2 weeks of wind tunnel test,  Since then, is considered the safest airplane, but the harm was already done.  The problem were basically 2:  the change of C of G with a heavier engine (Carden-Ford similar to the model A)  and that the elevator actuator had only a pull (cable) movement and no push. later changed to a rod.  

 

The Flying Fleas are still made in modern versions,  but also are something impresive to learn about.   Their stability and stall proof design is one of a kind.  Nothing similar with 3 axis airplanes...  I am flying  one and building a two seater modern one.

 

Well. sorry list for this is really something out of theme... Could start in this list a discussion larger than the one of the green scotchbrite 

Please dont comment in the list, I will hate to start someting big not Zenith related.

Just rermembered about the "ban"...

 

Saludos

Gary Gower

Builder and flyer of "La Bamba" Ladder Pou.

Building a 601 XL Jab 3300.

PLEASE!  Do not Archive.

 



--- On Thu, 11/13/08, steve <notsew_evets(at)frontiernet.net> wrote:



From: steve <notsew_evets(at)frontiernet.net>

Subject: Re: Heavy engine and Horiz. stab

To: zenith-list(at)matronics.com

Date: Thursday, November 13, 2008, 11:01 AM




<notsew_evets(at)frontiernet.net>



But, But, but what about flying wings ?  These dont have a horizontal

stablizer....

My son has a EZE that doest have a H.S.  It has two flying surfaces.  So does

the flying flea from the 1930s....

---

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