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C of G measuring

Anything to do with gliders & gliding.
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Phill Tadman
Posts: 397
Joined: 18 Aug 2015, 20:38
Location: South Cambs

C of G measuring

Post by Phill Tadman »

Hi all,

How and what do you use to check C of G on large scale models?

Thanks,

Phill

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RobbieB
Posts: 579
Joined: 07 Mar 2015, 22:22
Location: North West

Re: C of G measuring

Post by RobbieB »

A simple balance Phil with a graduated scale which indicates the position of the CG behind the leading edge. Very sensitive and more than accurate enough.

Doesn't take long to put together and you only have to make it once.

There is a 'hanging from the ceiling harness and plumb line' method but I found that a bit of a faff.

cg_balance.jpg

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Max Wright
Posts: 56
Joined: 10 Mar 2020, 19:57
Location: Clayton Bay South Australia

Re: C of G measuring

Post by Max Wright »

[There is a 'hanging from the ceiling harness and plumb line' method but I found that a bit of a faff.
[/quote]

It's called a Vanessa rig, Robbie. It's good for heavy warbirds et. al.
Max

Phill Tadman
Posts: 397
Joined: 18 Aug 2015, 20:38
Location: South Cambs

Re: C of G measuring

Post by Phill Tadman »

Thanks chaps,

I will have a go at making both, although the engineer in me wants to have a go at making something using load cells like this http://mahmoudi-modellsport.eu/glidercg-15kg

Phill

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terry white
Posts: 573
Joined: 18 Mar 2015, 21:08
Location: wareham,dorset.england

Re: C of G measuring

Post by terry white »

Phill, spend your time and money on the model and build the one shown by Robbie. Most of us have one and it does us proud. :) :)

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Peter Balcombe
Posts: 1141
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: C of G measuring

Post by Peter Balcombe »

Phil,
T9HobbySport do the 4Kg & 8Kg Max. units for approx. £103 each.
I built a similar function load cell type unit a few years ago & use it for smaller models.
My main concern with the electronic units is that all of the model weight is taken on 2 relatively small pads under each wing - the pads need to be small to measure loads at defined distances from a reference point for the overall CoG calc.

Robbie’s unit looks simple to make & easy to use - just doesn’t measure AUW at the same time.
Peter.

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RobbieB
Posts: 579
Joined: 07 Mar 2015, 22:22
Location: North West

Re: C of G measuring

Post by RobbieB »

terry white wrote:
03 Sep 2020, 11:06
Phill, spend your time and money on the model and build the one shown by Robbie. Most of us have one and it does us proud. :) :)
Yep, saw one on here (Brian's I think) and just built it - so easy and cheap, less than a tenner plus some scrap if I recall.

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Noël Rumers
Posts: 270
Joined: 20 Mar 2015, 10:29
Location: Hoboken Antwerp

Re: C of G measuring

Post by Noël Rumers »

Hi Phill,
I did see this one with a rather big plane on...
I build it and works fine.
Noël
Attachments
Febr 20130004Stipulation of the C.G..JPG
Febr 20130028Stipulation of the C.G..JPG
Febr 20130029Stipulation of the C.G..JPG
Febr 20130030Stipulation of the C.G..JPG
2016 09 150002CG position sorted.JPG
2016 09 150006CG position sorted.JPG

SP250
Posts: 146
Joined: 18 Mar 2015, 06:19
Location: North Shropshire

Re: C of G measuring

Post by SP250 »

MPX balancing rig - about £20 when I bought mine decades ago and it will handle up to 16kg because I did my Let Ash 26 on it for the maiden.
About £40 now, or pence if you copy Robbie's in scrap wood.

John M

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