[NSRCA-discussion] Fwd: Electric Weight Proposal LogicandRationale

Thu Jun 21 12:54:46 AKDT 2007

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From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
DaveL322 at comcast.net
Sent: Thursday, June 21, 2007 4:31 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Fwd: Electric Weight Proposal
LogicandRationale

Fred,

And they have quit improving glow engines?

********Certainly glow continues to improve, but as a well established
medium, it is not improving at the same rate as electric.

Didn't they just come out with a 2.0 ci glow engine thats light enough to
stick on a Pattern plane?

********Yes.

Saying we can't  do something because technology wil advance means you must
want to go back to the days when the Sig King Kobra was a top of the line
plane.  Anything with higher performance than thhat had using 1975
technology is not allowed.

********That was not my statement.  My statement was that a rules change for
an intended purpose needs be additionally evaluated for unintended
consequences (pattern has a long history of unintended consequences from
short sighted rules).

Case in point IMAC.  :-)

Glow planes DO bennefit from carrying more weight... you can bolt on that
2.0 ci engine and carry a 30 oz fuel tank to feed it.... and because you
weigh empty you gain the bennefits of added power making the added fuel
weight inconsequential.  Glow can compensate for the higher fuel consumption
that comes with higher power and not blink.

********Fair enough.  However, the intended context/framework was the
comparison of additional weight in the form of fuel to a glow plane with no
other changes, and the addition of weight (in the form of battery) to an
electric plane with no other changes.  The intended context aside, there are
also several other complicating factors such as wingloading, noise,
structural considerations, etc.

The basic conclusions I made remain unchanged.

Regards,

Dave

----- Original Message ----- 

From: Davel322 at comcast.net 

To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>  

Sent: Thursday, June 21, 2007 12:09 PM

Subject: Re: [NSRCA-discussion] Fwd: Electric Weight Proposal Logic
andRationale

Not a good proposal.

The fatal flaw is this - Glow planes receive no benefit from carrying
additional weight.  Adding weight to glow reduces the power to weight ratio,
carrying un-needed fuel detracts from performance.  Adding more battery
weight to an electric could substantially increase the power output AND
power to weight ratio.

Additionally, the proposal fails to acknowledge the inherent benefits of
electrics over glow (reduced structure is possible with reduced vibration,
reduced finish is possible with lack of oil...and many more).

An additional flaw (conceptually) is that this idea is very shortsighted.
Electrics are still in their infancy.  The motors, batteries, and ESCs will
all get lighter and more efficient (and cheaper) with future develepment.
Airframes tailored for electric will continue to improve further reducing
weight.  Within the existing rules structure, a very solid arguement could
be made that electrics can already achieve equal performance to glow, and a
very solid arguement could also be made that a cutting edge electric has
better performance than a cutting edge glow.  Electrics do not need any
additional advantages at this time and will be dominant in the near future
within the existing rules structure.

An average flying weight for glow of 11.5 lbs assumes the average dry weight
is 11 lbs.  11 lbs is not the average dry weight.

The assumption that 20 fluid oz is the average tank size needed for
completion of a pattern flight assumes a Masters or FAI preliminary flight.
Not all flights are for Masters and FAI.  Substantially less fuel is needed
for Adv, Int, and Sportsman.  Further, the assumption would also seem to be
based on a glow engine with a very high fuel consumption ratio.  Plenty of
2C setups complete Masters and FAI on 12 oz.....well managed 4Cs do almost
as well.  Perhaps 14 fluid oz would be a better average (~11 oz actual
weight).

The past few years, I've been fortunate to be flying some very high quality
composite models (glow Vivats and electric Prestiges).  The Vivats were 9
lbs 14 oz + 12 oz of fuel (more than enough for the Webra 160MC to get
through 1.5 PO7s) for an average flight weight of 10 lbs 4 oz.  My electric
Prestige with TP5300s was 10 lbs even on the 2006 NATs scale.....current
configuration puts it at 10 lbs 3 oz.  At ~$1900 USD per copy, the Vivat and
Prestige are not cheap, but hardly the most expensive option.  On the lower
end of the price scale, there are plenty of options from UltraRC, Fliton,
etc, that can be well under weight electric or glow.  The Black Magic series
is among the biggest planes currently and recently available and can be
built at 10 lbs electric and well under 10 lbs glow.

Applicable to this proposal (and others past, current, future) is that the
proposal should be evaluated from the perspective of a competitor looking
for a competitive advantage - ie, not how the proposal will effect current
equipment/desigsn, but what higher levels of performance could potentially
be achieved by a competitor looking to exploit the new rules.  Historically,
any increase in size, weight, or displacement has resulted in larger and
more expensive airframes.

Regards,

Dave Lockhart

DaveL322 at comcast.net

-------------- Original message -------------- 
From: Ron Van Putte <vanputte at cox.net> 
I got the following from John Fuqua. He is going to submit a proposal to
increase the weight limit for electric-powered airplanes to 11.5 lbs. I
suggested to him that he "float" his rationale by the NSRCA Discussion List,
to get some feedback. Here is his response. 

Ron Van Putte

Begin forwarded message:

Date: June 21, 2007 10:40:36 AM CDT

To: "Ron Van Putte" <vanputte at cox.net>

Subject: Electric Weight Proposal Logic and Rationale

Now that I am flying electrics I have come to realize the penalty that
electric planes have when being built that gas planes to not have. That
building penalty is significant under the current rules. Electrics must be
built lighter, to include paranoid attention to everything used - wood,
paint, fittings, etc., - all to make weight. Much more of a concern than gas
planes. Also I remember many instances at the NATs when we were weighing
airplanes, when the contestant was doing all he could do to meet weight with
a gas plane to include cleaning the fuel residue inside and out. A lot of
gas planes were weighing in at 10lb 11oz, 10lb 11.9 oz, even one that was
only a few grams under 5 kilos. Then they get to add a minimum of 16 to 20
ozs of weight by fueling up (and there is no limit to fuel capacity).
Takeoff weights are 12 lbs or more. This situation seems bizarre and
illogical when you put some thought into it. Electrics have a finite weight
and gas! ! plane s are open ended at Takeoff. Even though the 2005 NSRCA
survey did not support an electric weight increase it occurred to me that
the survey did not offer any logic or rationale as to why some increase
would be justified or not. I have attempted below to come up with a
reasonable compromise on electric weight allowance. I believe the rationale
supports an increase but it would be nice to have NSRCA membership look at
it to find the fatal flaw in the rationale before it gets submitted. The two
paras below are taken from the proposed change. Lets put it out and see what
the discussion list comes up with.

John 

Change paragraph 4.3 Weight and Size page RCA-2 to read: No model may weigh
more than 5 kilograms (11 pounds) gross, but excluding fuel, ready for
takeoff. Electric models are weighed with batteries and are allowed an
additional 8 ounces for a total of 11.5 pounds ready for takeoff. No model
may have a wingspan or total length longer than two (2) meters (78.74
inches).

Logic behind proposed change, including alleged shortcomings of the present
rules. State intent for future reference. 

Todays 2 meter RC Aerobatics fuel powered aircraft typically use fuel tanks
with a 20 fluid ounce capacity. A 20 fluid ounce Crank Tank containing 25%
Cool Power Pro Pattern fuel was tested. The fuel weighed 17.3 ounces.
Allowing for variation in tank sizes and fuel type a conservative weight of
16 ounces of fuel on average seems appropriate. This means that an allowable
takeoff weight for fuel powered aircraft is at least 12 pounds. Assuming
that all fuel is consumed during the flight, the average weight for the
aircraft is 11.5 pounds. By restricting electric powered aircraft to the
takeoff weight of unfueled aircraft an unfair weight penalty is being
arbitrarily imposed against the electric model. By allowing electric
aircraft an AVERAGE flying weight of the fuel powered aircraft, flying
weight equity is restored.

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