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» 2019 Llanfair TH Village Fete
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Saturday 7/7/18

2018-07-07, 21:07 by Gary M Jones

I was at the field today between 14:00 & 15:00 all on my own , good flying too. There is a dead sheep along the fence line towards the gate from the pits, I saw the farmer so reported this to her. I hope no one had plans for a BBQ Smile .

Farmer …

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Post by Stubbsy 2011-04-12, 21:33

Quick question - built a really small lightweight gliding wing and want to know what is more important, C of G or weight.
Glider is light weight anyway and im already over. I was aiming for about 220g but now weighs in at 250ish. Problem is C of G is about 3cm out to the plan and everything is pushed as far forward as it can be. No way of lightening up the back end im afraid to push C of G forward, so two choices, either add more lead to the nose, or chuck it and see if I can trim it out in flight. What do you reckon? scratch
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Post by melfyn 2011-04-12, 21:45

The chuck it and see is a sure fire way to a broken model, believe me I've been there and done that. If you really can't achieve the correct balance by shifting things around then you may have to resort to adding weight as necessary. Neutral
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Post by Rich 2011-04-12, 21:50

3cm is a fair bit behind, if it was forward of the CoG then it would sink without much elevator control, but behind then it's going onthe deck straight away, unless the plan is wrong of course, if it's conventional then 25%-30% of the cord at the root is somewhere near, if it's a delta/flying wing type it's a slightly different calculation, search google for a CoG calculator, in the meantime here's one

http://fwcg.3dzone.dk/

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Post by Allan Patrick 2011-04-12, 22:59

Hi Stubbsy, Melfyn & Rich are both quite right. A rearward cg is fatal! A heavy model is generally undesirable but not fatal for a small model. Therefore you have no option but to add lead.... But make it easy to remove and in small pieces as sometimes the CG shown is overly conservative and some can be removed after test flights. But only a small amount, or piece, at a time

Depending on the design of the model the lead can just be taped onto the outside temporarily with masking tape until the model is trimmed, then moved to its final position but ensure the cg position found by test glides is unchanged by this operation

Btw, seeing its a 250gm glider, I suggest a flat calm day and long grass would be good

Good luck Very Happy
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Post by Guest 2011-04-13, 08:55

Ben suggest you leave it where it is or move it back.Then you will have an excuse. Twisted Evil

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