[NSRCA-discussion] Long - RE: Weight

[Chad Northeast]

Hi Ron

Yes there are setups that are up at that power level, granted not 
everyone is.  I have ran setups that were that powerful, but I would 
make and educated guess that most are around 250-275 today.  This is 
statically, in flight is another matter altogether.  I went up a little 
on estimation because as model size and weight increases the W/lb rule 
increases as well, its not a linear rule.  Many speak to 150 W/lb for 3D 
performance, thats fine on a foamy, but anemic on a 2 meter model, and 
downright sad for anything significantly bigger.  I think the 40% guys 
are up to 400+ W/lb.  So if you are 250 W/lb on a 10.75 lb airplane you 
will feel less performance out of 275 W/lb on a 14 lb airplane.

My main point was that to increase the weight limit by any significant 
amount without changing the voltage rules would effectively negate what 
we have today, at least at the top level stuff as Dave was mentioning.

Chad

Ron Van Putte wrote:
> Whoa!  300 watts per pound?  I am currently flying a 10 lb  19.8 oz 
> (yeah!) E-Genesis with a Dualsky 6360-12T motor, which puts out 2450 
> watts.  The power/weight ratio is 218 watts per pound and, even though 
> it doesn't seem lacking in power, it is on a weight reduction program.
>
> Ron
>
> On Jun 4, 2009, at 3:35 PM, Chad Northeast wrote:
>
>> Dave is spot on IMO.
>>
>> Also I think one important fact may have not received enough 
>> attention.  That is that the current legal voltage limit on batteries 
>> in FAI is 42V.  Increasing the weight and therefore required power of 
>> an electric model requires that you play within that rule.  To 
>> generate the necessary static 300 W/lb that most current competitive 
>> F3A models demand today but at a new weight of say even 6 kg (13.2 
>> lbs), using an optimistic value of 35V under load you are beyond 100A 
>> setups.
>
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-- 
Chad

www.chadnortheast.ca