[NSRCA-discussion] Weight

Wed Jun 3 11:57:27 AKDT 2009

Judging from the amount of email I have, I'm clearly late to this party.  Verne and I have talked at length, and while I'm NOT a fan of rule changes, I do think we have a flawed system in NOT weighing TAKEOFF weight.  I leave the ground at 12lbs 8oz...and I'm legal.  (yeah, I fly with a 24oz fuel tank).    Point is that we would not be favoring a technology if we had a limit on take off weight rather than what we use now.  That appears to be were the Heli group went.

5.5Kg is probably a good number (though I'd have to shrink my tank!)

From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Derek Koopowitz
Sent: Wednesday, June 03, 2009 12:53 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Weight

Verne,

When I was at the CIAM meeting in March one of the proposals which was passed by the helicopter guys (F3C) was to modify the weight limit for their helicopters effective 1/1/2010.  Here is the new wording:

a) WEIGHT: The weight of the model aircraft (with fuel or batteries) must not exceed 6.5 kg.

Unanimously approved by the Plenary Meeting. Effective 01/01/10.
I'm going to feel out the rest of the F3A sub-committee members to see if there is interest in raising the F3A weight limit to 5.5kg.  What does everyone think about this?

-Derek
On Wed, Jun 3, 2009 at 7:51 AM, <verne at twmi.rr.com<mailto:verne at twmi.rr.com>> wrote:
Bill,
I've been working up an AMA rules proposal to address that very issue. Unfortunately, it won't be up for vote by the contest board anytime soon. In the meantime, there's one area you didn't mention in the glow to electric comparison and that's that an electric plane doesn't need as much internal reinforcement because there's virtually no vibrational effects to contend with that you do with glow. That equates to lighter airframes being acceptable as well as small, light, lipo packs to power the Rx and servos. An 8 minute e-flight typically uses about 50 mah. The same flight in glow is typically 200+ mah. All that aside, most electric pilots will tell you that making weight in electric is generally a pretty expensive proposition with a limited number of 2 meter planes available that are usually vacuum-bagged composite affairs. In addition, your best chances for making weight will also necessitate the lightest and generally most expensive motors and batteries. There are exceptio
 ns, and I'm sure we're about to hear about most of them, but I'll be able to point to just as many examples of guys that fly overweight at local contests where they know they won't be weighed and the only thing they're really guilty of is not spending the extra money that the lightest batteries and motors cost. In every other way, the planes they're flying are the same as the ones they're competing against. The proposal I'm working on is not self-serving because my planes make weight, but getting there is both too expensive and unreasonable, in my opinion. My proposal won't be to allow electric planes to weigh more, it'll require that they weigh less, but without the "fuel". The proposal will take into account that electric motors are inherently lighter than their glow counterparts as well as the reduced structural requirements. It will limit the mah of permissible packs to control that end of the equation and there's already a voltage limit on the books which is fine as it
 stands. I'm currently doing survey work at the contests I go to to see where everybody is at weight-wise and will post my proposal on this list soon. After that, it's up to all concerned to voice their opinions to their respective Contest Board reps.

Verne Koester
AMA District 7
Contest Board
---- Bill's Email <wemodels at cox.net<mailto:wemodels at cox.net>> wrote:
>  I am certain this has been beaten to death while I was off doing other
> things, but can anyone explain this:
>
>
> Rule 4.3: Weight and Size. No model may weigh more than five (5)
> kilograms (11 pounds) gross, but excluding fuel, ready for takeoff.
> Electric models are weighed with batteries.
>
> Why can't an electric "deduct" the equivalent of 16 ounces of fuel??  Is
> a plane without fuel rally "ready for takeoff"??
>
> I know it is likely a direct copy of the FAI rule, but it makes no
> logical sense. IC powered planes are weighed without fuel and can weigh
> right at 11 pounds. Add fuel and it could add another 10 to 12 ounces of
> weight. That's OK. But if an electric with batteries weight
> 11.0000000000000001 pounds it is overweight by the rules.
>
> Put another way, what does a YS and full fuel weigh compared to a
> motor+ESC+batteries?
>
> Hacker C50 14XL = 18.2 ounces
> Hacker Spin 99 ESC = 3.7 ounces
> 10S packs = +/- 43 to 46 ounces
>
> Weight w/o batteries = 21.9
> AUW w/batteries = 66.9 ounces
>
> YS 1.70 = 33.6 ounces (955 grams)
> AUW with tank and fuel = 45 ounces +/-
>
>  So I can see an argument that the electrics have a weight advantage
> when it comes to just the motor and ESC. But with "fuel" electric is at
> a 20 ounce disadvantage.
>
> So if I build a plane for electric I need to build it 20 plus ounces
> lighter than if I was going to put a nitro motor in it. How does that
> make sense. I know I am missing something important here, so educate me.
>
>
>
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