On 5/15/2004 Eric Jones wrote to the Aero-Electric List offering some observations on weight reduction:

a tidbit from the original thread . . . .

>The wire I have found is 0.24 ounces per foot (35% of the weight of standard
>RG142). Furthermore it has improved characteristics--50% better VSWR, 22%
>lower insertion loss, reduce phase and attenuation drift, etc. Making even
>much lighter cable is quite possible.

Eric Jones:

The real question is what is losing a pound worth? Here's my rough estimate:

Lets say your aircraft is worth $100,000 and weighs 2,000 pounds. Does this
mean your airplane is worth $50/pound? Maybe.

A better way to estimate the savings is to look at the total operating cost
for the life of the aircraft. In this case lets imagine the aircraft will
go 10,000 hours and costs $75 per hour to fly. Thats $750,000. At the end
of this time we assume the aircraft will be valueless. So thats
$750,000/2000 pounds; or $350/pound.

Lets apply the reasonableness test to this: Does $350/pound mean that your
old tin barf-bird sitting on the ramp is worth $350/pound? No. This figure
says that the cost of moving a pound of airplane all over the sky for 10,000
hours (50 years at 200 hours per year for example) is $350. Thats perfectly
reasonable.

So how much should you pay to avoid the $350/pound expense? If you invested
$35 compounded annually at 8% return with an inflation rate of 3.1%, you
would have the $350 in 50 years. So the answer could be $35.

(This simple example does not include the increased value in having an
airplane that goes a little faster, etc.)

(I would like aeroelectric listers opinions on this!).

So in summary I really don't know. If the cable costs even nearly the same,
certainly get the better and lighter cable.
But there are certainly other factors---

A couple weeks ago there was a lister who thought my Super-2-CCA copper clad
aluminum FatWire (available in two weeks) was too expensive for the weight
saved. I honestly don't know how best to calculate such a thing. I once flew
from Van Nuys, Ca to Winslow, Az in a Cessna150 and landed with a pound of
usable fuel remaining. I would have paid plenty for that pound of fuel
instead of a extra pound of wire.

Regards,
Eric M. Jones

Bob Nuckolls:

    Excellent points. I can expand on those ideas with the following
    anecdotes from my own experience. In 1964 when I was a tech writer
    for Cessna, a number commonly circulated around the
    engineering department suggested "For every pound of empty weight
    added to our airplanes, it will cost the owner(s) of that airplane
    $100 to buy the pound of stuff, maintain it, and purchase fuel
    to carry it around over the lifetime of the airplane.

    When I worked at Lear on the Gates-Piaggio GP-180 program in 1981, I asked
    my management how much bonus I could offer suppliers for weight
    reduction. That got me a bunch of surprise looks. "Shucks Nuckolls,
    beat 'em up for every ounce you can get . . . but why should we
    offer a 'bonus'? I told them about my experience at Cessna. They
    went off into a huddle and a few days later came back with a figure
    of $300. I was skeptical that it was truly so low a number . . . but it
    did mark a milestone in the way my management thought about the
    economics of designing, building and operating our products. The
    fact that they would offer ANY substantial number in dollars for
    weight reduction was pretty cool.

    A few days ago, I meet one of RAC's upper engineering management
    folks in the Denver airport. He had been visiting kids in the Denver
    area and I was coming back from a consulting trip in Idaho. I bemoaned
    the state of an important system in one of our products that was
    too complicated (astounding parts count), too heavy (about 50-60
    pounds), terrible service history (been in the #1 trouble reports
    slot on the airplane since day-one), and about 1.5 to 2x more expensive
    than more attractive options. I proposed RAC consider of a system
    that was at least 50 pounds lighter with a demonstrated
    zero faults performance record for many hours on a flight test
    aircraft.

    I asked him what it was worth for weight reduction on this
    airplane?  He didn't think long before he came up with the number
    of $2,000 per pound. I described my proposal for replacing
    the system and suggested that if we can carve out 50 pounds plus,
    reduce cost of hardware by about $20,000 per shipset, elminate
    95% of the installation labor and offer a system with an impeccable
    track record. One would think that with $100,000 weight-cost savings
    to the customer (in ADDITION to good will generated by eliminating a
    troublesome system), that changing over to the new system was
    essentially "free" . . . yes, there are some up-front costs on the
    order of a $million but this would amortize out VERY quickly.

    He didn't argue with me. The discussion went to other topics
    but it will be interesting to see what his reaction and support
    is when I bring this solution up in an upcoming meeting.

    Eric's observations are accurate and right on point. There
    are economies of operation, financing, fabrication and
    parts selection that can argue most energetically with
    each other. During Voyager's design and construction
    phases we were told that it takes 5# of fuel to carry
    1# of airplane around the world. This means that every
    pound of empty-weight elevates take-off weight by 6 pounds.

    Here the economies of operation held sway and every effort
    was made to carve grams out of the airplane sometimes at
    great expense on an airplane that had a lifetime of a
    few hundred hours! Each of you needs to make your own decisions
    as to which economy drives various decisions for purchase and
    assembly of parts. 

    I've oft used the term "cost of ownership" in discussions where
    the long term benefit from a larger investment up front
    pays off. I've also championed the notion of parts-count-reduction
    where the economies of reliability are perceived as most
    important. If one can bring multiple benefits to bear
    (lower parts count, lower weight, lower cost of ownership)
    while improving performance . . . then I'll suggest this
    is the very ESSENCE of the OBAM aircraft fabrication philosophy
    that will never be fully realized in the certified world.

    While OBAM aircraft have published gross weight limits, I
    think we can agree that those limits can be pushed under
    certain conditions (cool air, c.g. well inside limits,
    etc) and certain times when they cannot. It seems that
    spending lots of time and dollars on weight reduction for
    weight reduction's sake may not be the same overpowering
    economy in OBAM aircraft that it is in certified ships.

    I'll join Eric in offering the notion that the simple-ideas
    underlying the really elegant decision are easily obscured by
    a lot of ol' pilot's tales and hangar wisdom. Bringing
    questions out to the List is the best place to filter
    the various ideas in search of the elegant solution.

    'Lectric Bob . . .
	
Gary Casey:

I'll add my bit to the discussion.  The other comments were very
appropriate, but here is how I calculated it:  My current airplane is worth
about $60,000 and carries about 600 pounds.  $100 per pound.  I don't carry
all 600 pounds very often, but when I do an extra pound would be valuable.
The important thing is that once you set a value use the discipline to stick
to it.  I've set it at $100 and so far have paid for things that cost
$50/pound, like throwing away all the nylon locknuts that came with the kit
and buying all-metal locking nuts - average of $48/pound.

One of our customers related that for a military aircraft project they were
giving an incentive of $1,000/pound.  For cars I've heard of $1/pound.  I
think anything from $50 on up would make sense.  Just don't do what some of
the OEM's do and worry about the airframe for hours, but when the time comes
to add the last 10% of the stuff they seem to figure "oh, well, what's an
extra pound?"  Just from the few things they buy from us they could save
maybe a pound for very little effort, but they don't seem to be interested.

Gary Casey