[NSRCA-discussion] Fwd: Electric Weight Proposal LogicandRationale
Richard Strickland
richard.s at allied-callaway.com
Thu Jun 21 12:11:08 AKDT 2007
Dave,
I may be arguing just for the sake of arguing--but: They made an exception
to the take-off weight of 5kg for fuel-so why not for batteries? If the
rule is 5kg--then it should be that for everyone. OK, OK, I know (sort of)
why--but I don't necessarily agree with it...bitch, moan, grumble....
Richard
-----Original Message-----
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 2:27 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Fwd: Electric Weight Proposal
LogicandRationale
Richard.
I agree with all your points in theory/concept.
As has been discussed many a time on this list, a guy doing exactly what
you suggest (using an existing airframe for electric, being a couple ounces
over the weight limit, and not gaining a competive advantage by being
slightly overweight) is not going to draw attention and be DQ'd from
anything other than the finals at the US NATs. So practically, the 11.1 lb
conversion is not an issue.
I tend to think the durability of electric planes themselves is not as a
big a problem as thought - I think most of the problems tend to come from
glow conversions which end up some signifigant compromises to reduce weight
(which would have been absent if initially electric). I really don't think
durability of the electric plane itself is a problem - purpose built
electrics are likely more durable as they don't have to endure vibration.
The Abbra (I built one to use as an electric testbed) kit is no different
glow/electric - same weight glass, CF, foam, paint, etc. Mine is right at
10 lbs 10 oz w/ TP5000s and I did nothing special to save weight. It is
very easy to get an electric heavy if care is not taken selecting
components, but that is really just a learning curve (not unlike glow), and
much of what can be done to keep an electric light is limited when
converting from glow.
Dave
-------------- Original message --------------
From: "Richard Strickland" <richard.s at allied-callaway.com>
For most guys, myself included, just want to use the existing airframes
and not have to sweat being super-light and it costing up the wazoo to get
there. Plus the very light airframes don't stand up to much abuse to where
one little prang puts you over the limit. You certainly have a good point
about the unintended consequences of a change--but how many guys would go
for it?--you don't see that many bipes out there now primarily because they
are a pain in the ass to deal with when in heavy practice mode for a guy
after work...
Richard
-----Original Message-----
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 12:36 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Fwd: Electric Weight Proposal Logic
andRationale
Richard,
I think in many respects trying to compare electric / glow is like
comparing apples and oranges.....so having a blanket set of rules that is
absolutely equal (and fair) for both is not going to happen.
The "most fair" methods are going to be too complex - ie, calculate
average power loading and wingloading for average electric and glow models
over the course of an average flight...and then structure the rules to
ensure equality of the averages for glow and electric. And as technology
and equipment changes....the rules would have to continually change to
maintain parity.
My electric Prestige is 7.5 lbs without batteries.....for another 2.5
lbs of airframe, .5 lb of motor, and .5 lb of radio gear, I could easily
build a bigger (but still 2M) plane with performance that would absolutely
obsolete any of the current day 2M stuff (and probably double the pricetag
as well).
Dave
-------------- Original message --------------
From: "Richard Strickland" <richard.s at allied-callaway.com>
I know I sound like a broken record, but: The IC airplanes are
weighed without fuel--the electrics should be weighed with out their fuel.
Give or take a little for the tank and not splitting hairs--but it simply is
not fair the way it is set up now. I'd still like to know how that decision
was made--so they could just un-make it...seemed pretty arbitrary to me...no
rule change involved--it appears someone just said this is so. Somebody
straighten me out, please.
Richard Strickland
-----Original Message-----
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 11:09 AM
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 yo! ! u put s ome 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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