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Vanessa c.g. Rig: How to.

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Vanessa c.g. Rig: How to.

Old 01-24-2008, 01:14 PM
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Default RE: Vanessa c.g. Rig: How to.

Thank for this fast reply. Funny is only 4 centimetres off..I flew this model several time last year, rock solid and feel comfortable. I will try to move the CG back a little first.
Amazing gadget.
I build the Vanessa to find the perfect CG on a BMV Electra a 10 pounds jet.
Old 01-24-2008, 01:31 PM
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Default RE: Vanessa c.g. Rig: How to.

I am seeking information here, not being critical. The CG equipment described here will determine the CG of the mass of the components of the airframe. This will not determine the aerodynamic requirements of the airplane, such as aerodynamic balance point and/or at the correct decelage angles if any.

Or does it?

Ed S
Old 01-24-2008, 01:34 PM
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Default RE: Vanessa c.g. Rig: How to.

You are correct. The rig does not tell you what a good CG should be for a particular model, it only tells you where the actual center of mass is.
Old 02-28-2008, 12:14 AM
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Default RE: Vanessa c.g. Rig: How to.

does it matter how far you hang the sling , can you hang in from like the fire wall and the tail ? would this give the same results? and whats the best way to use this way on a bipe?

jason,
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Old 02-28-2008, 03:56 AM
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Default RE: Vanessa c.g. Rig: How to.


ORIGINAL: flyjay77

does it matter how far you hang the sling , can you hang in from like the fire wall and the tail ? would this give the same results? and whats the best way to use this way on a bipe?

jason,
I usually connect just behind the prop and to the prop shaft. On the rear I would connect to the tail wheel allowing the front edge of the horizontal stabilizer to support the sling. The location is relatively unimportant but should be convenient and not damage the airplane.

Bill
Old 02-28-2008, 07:10 AM
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Default RE: Vanessa c.g. Rig: How to.

Use the atached diagram to determine the MAC of a swept wing. Looking at the pictures I would agree with Majortom. Project the pointer position out to the MAC and it looks about right.

Ed S
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Old 12-12-2008, 06:19 PM
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Default RE: Vanessa c.g. Rig: How to.

There's a big difference between the MAC and the CG.

I don't believe I would ever trust that device.

Charles
Old 12-17-2008, 07:23 PM
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Default RE: Vanessa c.g. Rig: How to.

been using the vanessa for years now on my giant scale and havnt had a problem yet, lots of bipes........
Old 01-16-2009, 12:29 AM
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Default RE: Vanessa c.g. Rig: How to.

hi, I think this CG device is amazing. I cannot wait to make one. It took me a while to understand how it worked. Is there such a device to balance side to side? One question. If the plane is level and the plumb bob is at the planes suggested CG point, then the planes CG has been validated? thanks
Old 01-16-2009, 10:30 AM
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Default RE: Vanessa c.g. Rig: How to.

That is correct.

Les
Old 01-26-2009, 08:01 AM
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Default RE: Vanessa c.g. Rig: How to.

Hey guys I have a question, I'm trying to be certain that I am properly setting the C.G. on this KMP Corsair that I have just completed, I need opinions please (help!) My concern is that I may be off and wonder if you would suggest a vanessa for this job. The manual calls for C.G. at 130mm aft of the leading edge. I have always balanced my planes with the two dowel method so by going with what i'm used to, I made an amped up version to try and balance this Corsair at the curve of the gull wing. I have it sitting inverted such that when the model is on its called for factory c.g. point, the chord of the horizontal stab will be at 0 degrees to the floor or that is parallel with the floor. What feels disconcerting to me is that when I look at the model balanced on its called for C.G. and the Hori. Stab flat with the floor the fueslage in general appears as if its tail heavy(tail low). Perhaps this is just due to the shape and geometry of the Corsair but its enough to have me concerned. Here are images of how it looks on its factory called for 130mm cg and notice the overall appearance of the fuse relative to the surface of the table (appears tail low). I'm just worried if i'm possibly missing something here and have possibly a tail heavy condition. Any help and input will help me out a lot and I thank you in advance.
Louis

BTW: I measured the Main wing chord length at the root and got roughly 400 MM. So with the factory specified 130 MM c.g. point that I set the balancing line with on the tape, this came out to a 32.5% of max chord length. is this acceptable?

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Old 01-27-2009, 09:51 AM
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Default RE: Vanessa c.g. Rig: How to.

Louis,

I think you are being deceived by the shape of the fuselage. The Wing, Stab and thrust line of the plane all appear to be level. I would think that plane is about right.
Old 06-03-2009, 10:22 AM
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Default RE: Vanessa c.g. Rig: How to.

In post #4, the figures D and F in the drawing showthe string on the right side of the dowel is obviously wound in the opposite direction to the one on the left side. Explanation please, as later in the thread (post #12and #13) they are shown wound in the same direction, or am I missing something?

ORIGINAL: TigreST

This is the last of Jims Archers drawings related to Vanessa.
Old 06-03-2009, 02:55 PM
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Default RE: Vanessa c.g. Rig: How to.

I don't want to say that the creator of the device drew it wrong, but, the photos are correct. If the cord is wound as shown in the drawing, they will not wind correctly when you twist the dowel. If they are wrapped as they are in the photo, you will be simply tilting the planes nose up or down as you twist.. The other way it will rotate at an odd angle that will not help the process at all.
Old 06-16-2009, 08:35 AM
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Default RE: Vanessa c.g. Rig: How to.

I finally got around to finishing a mustang that I partially built 12 years back.the plans are gone and not available so I dont know where the CG really is. are you saying if I make the vanessa device the plumb bob will give me a accurate point of where the CG actually is? or do I use the complicated math formula?
Old 06-16-2009, 09:19 AM
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Default RE: Vanessa c.g. Rig: How to.

It will tell you where the center of balance (aka CG) is, but not where it belongs.

Les
Old 06-16-2009, 10:50 AM
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Default RE: Vanessa c.g. Rig: How to.

so it means that I would have to likely take 25 to 30 percent of the CG line ??
Old 06-17-2009, 09:15 AM
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Default RE: Vanessa c.g. Rig: How to.

Go here first.<a href="http://www.palosrc.com/instructors/cg.htm">

http://www.palosrc.com/instructors/cg.htm</a>

Les
Old 06-24-2009, 12:36 PM
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Default RE: Vanessa c.g. Rig: How to.

I have made and used the Vanessa jig for a few months now and find it works. It also served to get me interested in some kind of jig that I could just set a plane in and check the balance. I am probably being excessive. I first made a 2 "U" shaped pcs. from some 3/8's ply with one leg of the U about a 3rd of the other and then connected the two pcs with dowel and hung it from a string and set my electric model on it after balancing the jig and marking the cg of the jig. It appeared to work. So then I purchase some 3/4" pvc and some fittings and started cutting and glueing etc. etc. until I came up with this jig.
The first pic is of the jig on my mobile bench with the back legs and safety uprights on, the back uprights are removable and are to keep the plane from sliding off, they are removed to place the plane in the jig. I have marked the same point "cg" of suspension on both lower legs and for the purpose of trying it out one inch forward of this to accommodate my old bipe. The next pic is the jig by itself balanced by itself with the lower legs lined up with a level horizontal surface and then the third is with an old Aeromaster bipe with the front edge of the lower wing placed on the one inch mark and a string tied over the aft part of the fuse to hold it in proper flying attitude. The jig flexes, when suspended. as expected in the fourth picture but I think this is of little importance and something I could fix if it is. I originally determined to use larger dia. pvc to avoid this but it was not available. My intention is to put a leveling bubble on the horizontal leg for accuracy.
The whole thing with the plane installed and suspended seems very stable and appears to work although I question whether it is sensitive enough. It doesn't compare to the Vanessa rig for cost and ease of storage but the ability to place a plane in it and hang it and then add weight to see the results is interesting. I can see hanging a plumb bob for more accuracy from the upper support.
I'm really looking for feed back about the design and logic used. It has been fun and interesting so far and accommodates my one giant scale gas as well. The dimensions are approximately: width 15" height 20" without the legs [img][/img]and length 20".
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Old 06-26-2009, 04:59 PM
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Default RE: Vanessa c.g. Rig: How to.

I think the rig is great.balancing a plane can never be excessive .I have learned after several decades of flying that even the most complex plane flies rather easily if properly balanced .I balance both foward and lateral.my last maiden flight required 2 clicks of up and thats it.I also use the mac formula to find the CG but your jig would be a backsaver especially with big planes.
Old 06-26-2009, 08:11 PM
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Default RE: Vanessa c.g. Rig: How to.

I built one of these and it works great for me. The only thing I changed on mine is the plumb bob. Instead of a Nail set, I used an old Dodge van key. Heavey enough to do the job, but won't poke thru the covering if it slips.
Old 06-29-2009, 04:12 PM
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Default RE: Vanessa c.g. Rig: How to.

think its time to build one thanks folks
Old 07-13-2009, 11:43 PM
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Default RE: Vanessa c.g. Rig: How to.

Hi Guys, Just finished building a vanessa and i don,t really know how i guessed this stuff for so long. i tried it on all of my stuff and found one that i thought was right but never flew right. it was out of cg by 3/4 of an inch aft. like mikey sez " try it, you'll like it"
Old 07-14-2009, 05:41 PM
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Default RE: Vanessa c.g. Rig: How to.

ORIGINAL: luning1
'' try it, you'll like it''
I agree. I made one of these several weeks ago after reading this thread. I cannot believe how much some of my planes were off. I am almost done building a Dumas Big Swamp Buggy boat and intend to use the Vanessa rig to set the COG on that also.

Bob
Old 10-12-2009, 09:25 AM
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Default RE: Vanessa c.g. Rig: How to.

How does it allow the plane to rotate for or aft? Seems like the rod in the wood block would be to much friction to get an accurate reading? Actually i'm studying the diagrams seeing the dowel is locked in placeand usage of the plumb bob but it's not making sense yet.

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