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C of G and a heavy nose...

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pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Tue Jan 19, 2010 4:21 pm Post subject: C of G and a heavy nose...

Hi all,

I brought a 701 with a EA81 engine 6 months ago. I've done about 100 hours in it so far but I'm still struggling with the weight and balance. When I brought it, it was forward CG, to the point of being dangerous, when I cut the throttle, just myself onboard, it would drop like a stone (think helicopter autorotation..) I thought.. some weight in the tail... 5kg's... and suddenly it had a glide ratio. I now have 8kg's in the tail (I know it's alot) and it handles well. Too much more weight in the tail and it gets a bit wobbly, not aft CG, but too much weight on a long arm. What I'm trying to achieve is being able to hold my nose off on touchdown, as JG was talking about in a previous post, with power off, which is what I can do with other well balanced aircraft. Whilst I understand that if I put a rotax in I would probably solve the weight and balance problem, I don't really want to spend the $$$ involved in that. The EA81 goes well, apart from the weight problem. I have a warp drive prop. Any comments and suggestions would be useful.. 



Cheers

Ross

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Tue Jan 19, 2010 5:07 pm Post subject: Re: C of G and a heavy nose...

It's hard to keep the nose off the ground consistently with slats. The nose either wants to go up or down with little stick movement. Take the slats off and put on vortex generators and it will be much easier to flare and keep the nose wheel off and steady.

_________________
Ron Lee
Tucson, Arizona

arno7452(at)bellsouth.net
Guest

Posted: Tue Jan 19, 2010 5:08 pm Post subject: C of G and a heavy nose...

Ross,

I suggest you sell this thing.  But, there are still 2 cycle replacement 

engines around that are cheap and light weight.

Ken



do not archive



---

lvuman(at)gmail.com
Guest

Posted: Tue Jan 19, 2010 5:22 pm Post subject: C of G and a heavy nose...

The trailing edge of the elevator is bent slightly up to compensate for the lighter designed weight (80HP) of the 701.  Bend the trailing edge down "slightly" and it will make a huge difference on keeping the nose off longer on landing and give you more authority in back trim on landing approach.  Simple solution.  Jim

 

On Tue, Jan 19, 2010 at 5:21 PM, pipross <pipross(at)xtra.co.nz (pipross(at)xtra.co.nz)> wrote:

[quote] --> Zenith701801-List message posted by: "pipross" <pipross(at)xtra.co.nz (pipross(at)xtra.co.nz)>

 

 Hi all,

 I brought a 701 with a EA81 engine 6 months ago. I've done about 100 hours in it so far but I'm still struggling with the weight and balance. When I brought it, it was forward CG, to the point of being dangerous, when I cut the throttle, just myself onboard, it would drop like a stone (think helicopter autorotation..) I thought.. some weight in the tail... 5kg's... and suddenly it had a glide ratio. I now have 8kg's in the tail (I know it's alot) and it handles well. Too much more weight in the tail and it gets a bit wobbly, not aft CG, but too much weight on a long arm. What I'm trying to achieve is being able to hold my nose off on touchdown, with power off, which is what I can do with other well balanced aircraft. Whilst I understand that if I put a rotax in I would probably solve the weight and balance problem, I don't really want to spend the $$$ involved in that. The EA81 goes well, apart from the weight problem. I have a warp drive prop. Any comments and suggestions w!

   ould be useful..

 

 Cheers

 Ross

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=282338#282338

 

 

 

 

 

 

 

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larry(at)macsmachine.com
Guest

Posted: Tue Jan 19, 2010 5:44 pm Post subject: C of G and a heavy nose...

Hi Ross,

Not sure of your configuration, but you might put the radiator back 

under the belly a ways and move the 18 lbs or so that far to improve 

your center of gravity.

I've attached a picture of an installation that does exactly that, tho 

he's not using a Subaru, the installation is clearly the same for 601 or 

701 with an EA-81.

My site shows the installation of this radiator on my engine page.

See attached image too.



Larry McFarland 601HDS at www.macsmachine.com



pipross wrote:

 	  Quote: 	
		   



 Hi all,

 I brought a 701 with a EA81 engine 6 months ago. I've done about 100 hours in it so far but I'm still struggling with the weight and balance. When I brought it, it was forward CG, to the point of being dangerous, when I cut the throttle, just myself onboard, it would drop like a stone (think helicopter autorotation..)  The EA81 goes well, apart from the weight problem. 



 Cheers

 Ross





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 82338#282338

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lgold(at)quantum-associat
Guest

Posted: Tue Jan 19, 2010 6:02 pm Post subject: C of G and a heavy nose...

This sounds like a bad idea to me. If slats bring the center of lift forward

somewhat taking them off will exacerbate the balance problem.



--

pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Tue Jan 19, 2010 7:58 pm Post subject: Re: C of G and a heavy nose...

Thanks for your replys... I forgot to mention it was built without slats (with VG's), I'm not a fan of two strokes particularly, I used to fly trikes and was not comfortable over bush or water hoping my two stroke would keep cycling, the radiator idea is pretty good, i'll attach a photo showing the current setup if I can find a side on one

pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Tue Jan 19, 2010 8:02 pm Post subject: Re: C of G and a heavy nose...

Like this too, when you say bend, are we talking about cable adjustments, or something a little more agricultural??...



Ross



[quote="lvuman(at)gmail.com"]The trailing edge of the elevator is bent slightly up to compensate for the lighter designed weight (80HP) of the 701.ï¿½ Bend the trailing edge down "slightly" and it will make a huge difference on keeping the nose off longer on landing and give you more authority in back trim on landing approach.ï¿½ Simple solution.ï¿½ Jim

johndread(at)aol.com
Guest

Posted: Tue Jan 19, 2010 8:13 pm Post subject: C of G and a heavy nose...

Hi Ross;

             There  was  a post a year or so ago that was OK'd by the factory. The problem was  that the elevator trim did not have much authority in one direction. The  solution was to bend the rear of the elevator up so it was inline with the LE of  the elevator. This should also help the hold the nose off. 

  

 John  Read

CH701 - Elbert CO - Jabiru 3300



Phone: 303-648-3261

Fax:  303-648-3262

Cell: 719-494-4567   

  In a message dated 1/19/2010 9:04:31 P.M. Mountain Standard Time,  pipross(at)xtra.co.nz writes:

  	  Quote: 	
		  -->    Zenith701801-List message posted by: "pipross"    <pipross(at)xtra.co.nz>



Like this too, when you say bend, are we    talking about cable adjustments, or something a little more    agricultural??...



Ross



[quote="lvuman(at)gmail.com"]The trailing    edge of the elevator is bent slightly up to compensate for the lighter    designed weight (80HP) of the 701.ï¿½ Bend the trailing edge down "slightly"    and it will make a huge difference on keeping the nose off longer on landing    and give you more authority in back trim on landing approach.ï¿½ Simple    solution.ï¿½ Jim





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  [quote][b]

pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Tue Jan 19, 2010 8:18 pm Post subject: Re: C of G and a heavy nose...

Some pre painting photos that'll show the layout... Thanks for the elevator info John..

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pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Tue Jan 19, 2010 8:19 pm Post subject: Re: C of G and a heavy nose...

and some more....

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pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Tue Jan 19, 2010 8:21 pm Post subject: Re: C of G and a heavy nose...

and now

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vgstol(at)bigpond.net.au
Guest

Posted: Tue Jan 19, 2010 8:40 pm Post subject: C of G and a heavy nose...

The slats don't bring the center of lift forward.  A bit surprising I know, but tested over and over again, that removing the slats caused no change in trim.  See the testing and results at www.stolspeed.com   There's a whole new set of tests there, comparing the performance with slats/no slats.



JG



On Wed, Jan 20, 2010 at 11:50 AM, Les Goldner <lgold(at)quantum-associates.com (lgold(at)quantum-associates.com)> wrote:

 [quote]--> Zenith701801-List message posted by: "Les Goldner" <lgold(at)quantum-associates.com (lgold(at)quantum-associates.com)>

  

 

This sounds like a bad idea to me. If slats bring the center of lift forward

 somewhat taking them off will exacerbate the balance problem.

 

 --

mksoucy(at)yahoo.com
Guest

Posted: Wed Jan 20, 2010 2:13 am Post subject: C of G and a heavy nose...

What about an Aero Vee engine. 



Sent from my iPod



On Jan 19, 2010, at 7:21 PM, "pipross" <pipross(at)xtra.co.nz> wrote:






Hi all,

I brought a 701 with a EA81 engine 6 months ago. I've done about 100 hours in it so far but I'm still struggling with the weight and balance. When I brought it, it was forward CG, to the point of being dangerous, when I cut the throttle, just myself onboard, it would drop like a stone (think helicopter autorotation..) I thought.. some weight in the tail... 5kg's... and suddenly it had a glide ratio. I now have 8kg's in the tail (I know it's alot) and it handles well. Too much more weight in the tail and it gets a bit wobbly, not aft CG, but too much weight on a long arm. What I'm trying to achieve is being able to hold my nose off on touchdown, with power off, which is what I can do with other well balanced aircraft. Whilst I understand that if I put a rotax in I would probably solve the weight and balance problem, I don't really want to spend the $$$ involved in that. The EA81 goes well, apart from the weight problem. I have a warp drive prop. Any

 comments and suggestions w!

ould be useful.. 



Cheers

Ross





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 82338#282338

blackmore(at)platinum.ca
Guest

Posted: Sat Jan 23, 2010 6:51 am Post subject: C of G and a heavy nose...

I was just wondering if anyone has tried to put a jack screw like the ones found on the pa 18 , Navion and others, it sounds like a slick way to trim the tail, I know I shall be needing the weight back there anyway

 Chris

  

  [i]----

vgstol(at)bigpond.net.au
Guest

Posted: Sat Jan 23, 2010 12:10 pm Post subject: C of G and a heavy nose...

Changing the incidence of the horizontal stab works for trimming at cruise speeds, but loses effectiveness at the very slow landing speeds of these aircraft.  So, the nose will still come down heavily on touch down, or even before, when the weight and balance overcomes the diminishing aerodynamic forces.....   JG



On Sun, Jan 24, 2010 at 12:51 AM, Chris Blackmore <blackmore(at)platinum.ca (blackmore(at)platinum.ca)> wrote:

[quote]             I was just wondering if anyone has tried to put a jack screw like the ones found on the pa 18 , Navion and others, it sounds like a slick way to trim the tail, I know I shall be needing the weight back there anyway

  Chris

  

  [i]----

blackmore(at)platinum.ca
Guest

Posted: Sat Jan 23, 2010 12:24 pm Post subject: C of G and a heavy nose...

Thanks, just learning!!, and still looking for an orphaned  fuselage .

  

  [i]----

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Sat Jan 23, 2010 12:46 pm Post subject: Re: C of G and a heavy nose...

Ross:



Notwithstanding my opinion that the most important thing is to ensure the weight/balance is within design limits for TC 10141E compliance, and a "701" without the slats is NOT, you may get sufficient elevator authority with power off by installing the elevator VG kit from Zenair.



They have some videos of a set being trialled which is quite impressive.



Ralph

_________________
Ralph - CH701 / 2200a

pipross

Joined: 28 Nov 2009
Posts: 12

Posted: Sat Jan 23, 2010 3:53 pm Post subject: Re: C of G and a heavy nose...

Thanks Ralph, I already have VG's on the wings and the elevator



Ross

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