[NSRCA-discussion] Weight
Gray E Fowler
gfowler at raytheon.com
Wed Jun 3 10:19:33 AKDT 2009
Eventually I think pattern will be all electric, but this is still a ways
off. Electric car development will utilize battery technology that we can
eventually use. This will be billions in development-good thing the US car
industry has such an efficient, reliable finance partner.
Changing the rules like Dave says will quickly be behind the curve.
Besides, eliminating the weight limit will result in Biplanes going to
Triplanes. Everyone knows that Triplanes score better than Biplanes. Then
comes Quadwings, on and on.
Gray Fowler
Senior Principal Chemical Engineer
Radomes and Specialty Apertures
Technical Staff Composites Engineering
Raytheon
"Dave" <DaveL322 at comcast.net>
Sent by: nsrca-discussion-bounces at lists.nsrca.org
06/03/2009 12:51 PM
Please respond to
General pattern discussion <nsrca-discussion at lists.nsrca.org>
To
<verne at twmi.rr.com>, "'General pattern discussion'"
<nsrca-discussion at lists.nsrca.org>
cc
Subject
Re: [NSRCA-discussion] Weight
Verne,
You probably want to keep the mah limit at 5300....because at a 5S
configuration, that is the maximum size allowed by TSA for airline travel
(based on watts, equivalent lithium content, etc.....5s5300 works out to
be
98.5% of what is allowed, based on nominal voltage of 3.7 per cell).
The price of motors and batteries is rapidly dropping....by the time you
would get a rule proposal completed, approved, and in place, technology
will
have solved the problem. What will not change is the price of the top end
electric and glow setups - they will always be expensive, as that is the
nature of the latest/greatest/best.
Regards,
Dave
-----Original Message-----
From: verne at twmi.rr.com [mailto:verne at twmi.rr.com]
Sent: Wednesday, June 03, 2009 12:59 PM
To: General pattern discussion
Cc: Dave
Subject: Re: [NSRCA-discussion] Weight
Yes, the goal is to make it cheaper. What I'm trying to do is take the
weight of the batteries out of the equation just like fuel is. With rare
exception, cheaper batteries equals more weight. The reason for including
a
mah restriction (probably 6000mah as rated by the mfg) is to keep things
under control and avoid someone taking advantage with larger batteries.
What
I'm hearing out of my district is guys wanting to try electric and getting
scared off with the high cost of kits, batteries, and motors that will
make
weight. I'm well aware that the Prestige, Spark, Integral, and a few
others
can make weight with the right batteries and motor. I'm also aware of what
that costs. My goal is to make it possible for someone to build a Black
Magic without the building skills of Zen that'll make weight with an Axi
and
Zippy packs.
Verne
---- Dave <DaveL322 at comcast.net> wrote:
> Verne,
>
> If you goal is to make pattern cheaper, I'm all for that (and the most
> expensive setup right now is a YS CDI setup), but I can't see how a
proposal
> based on your description can effectively accomplish that.
>
> Is the goal to reduce cost of the electric (which I can argue is cheaper
> than glow at the top levels of each) or to make electric and glow
airplanes
> have the same cost for equal performance? As electric technology
rapidly
> advances, any proposal based on current day planes will be obsolete by
the
> time it in place.
>
> Limits on pack mah will certainly add to the complexity of tech
inspections
> of planes....to say nothing of the fact that all "20C" lipos do not
weigh
> the same thing, and all batteries of a marked capacity are not the same
> either - the door will be wide open for "creative" labeling of mah
capacity
> on batteries.
>
> Just as there are examples of overweight glow planes (I do hope you are
> getting weights on glow planes as well during your surveys???), there
are
> overweight examples of electrics - neither should be accommodated by a
> change in the rules. Each competitor should evaluate the rules, and
prepare
> to compete with whatever setup best suits there budget, time, resources,
and
> is within the RULES.
>
> Electric may cost more upfront, but it is rapidly getting cheaper (and
glow
> is getting more expensive). The big hurdle for electric right now is
that
> all the costs are upfront, making it expensive to enter.
>
> Regards,
>
> Dave
>
> -----Original Message-----
> From: nsrca-discussion-bounces at lists.nsrca.org
> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
> verne at twmi.rr.com
> Sent: Wednesday, June 03, 2009 10:52 AM
> To: General pattern discussion
> Subject: Re: [NSRCA-discussion] Weight
>
> 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> 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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