[NSRCA-discussion] Fwd: Electric Weight Proposal Logic and Rationale

[Stuart Chale]

Increasing the weight limit for electrics has always made some sense
especially now that most people do not see a perceived advantage to them.
Initially when many saw electric as an unfair advantage it seemed
appropriate to place some limits on the aircraft.  Even with the current
limits, builders and airframe producers have found ways to keep the plane
under the 5 kilo limit.  The cost is lighter more expensive batteries (more
expensive, especially if they are less likely to last as many cycles as a
more robust cell, which may or may not be fact), lighter airframe structures
and often more expensive construction materials and components to meet that
weight.

 

The only question I would ask is if un-limiting the weight to 11.5 pounds
might provide a change to allow electrics to have the distinct advantage.
Remember most of the prior changes have caused an evolution in airplane
design.  Many rule changes were simply made to level the field but they
ended up changing what we fly.  For instance, the allowal of 4 cycle engines
up to 1.2 cubic inch.  The first 1.2 four cycles were barely able to keep up
with a 60 2 cycle.  That changed and so did our aircraft.

 

Stuart Chale

 

  _____  

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Ron Van Putte
Sent: Thursday, June 21, 2007 12:09 PM
To: NSRCA Mailing List
Subject: [NSRCA-discussion] Fwd: Electric Weight Proposal Logic and
Rationale

 

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 planes 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. 

Today's 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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