Today's Message Index:
----------------------
1. 01:00 PM - Weight of RG142 ()
2. 03:54 PM - Re: Weight of RG142 (Eric M. Jones)
3. 05:57 PM - Batterys (Boddicker)
4. 06:46 PM - Re: Batterys (James E. Clark)
5. 09:52 PM - 6A gear weldment fit in a QB kit (thomas a. sargent)
Message 1
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--> AeroElectric-List message posted by: <bakerocb@cox.net>
AeroElectric-List message previously posted by: "Eric M. Jones"
<emjones@charter.net>
<<If RG142 is the only coax that is used in an airplane--about how much isused
per airplane? (Now please don't say it depends...). I am trying to find out how
much weight can be saved by changing to something else,and if
RG142 ONLY can be used for everything coaxial.
Offline is best: Email: emjones@charter.net Regards,
Eric M. Jones>>
5/12/2004
Hello Eric, Forgive me -- I am going to disregard your requests to respond off
line and to not say "It depends".
But I will try to put some numbers in my answer.
1) My airplane uses 9 antennas: 2 VHF NAV, 2 VHF COMM, 1 GLIDE SLOPE (not connected),
1 MARKER BEACON, 1 GPS, 1 ELT, and 1 TRANSPONDER.
2) Assume that each box requires 5 feet of coax going to its respective antenna.
This is over kill I know -- many of the coax runs are very short. This would
be a total of 45 feet of coax (9X5=45).
3) The Belden catalog says that RG 142 weighs 4.3 pounds (68.8 ounces) per 100
feet. Or .688 ounces per foot.
4) 45 feet of coax times .688 ounces per foot gives a total of 30.96 ounces or
1.935 pounds.
5) I don't know of any 50 ohm RG type coax that is significantly lighter than RG142
(which has a solid steel core), but there may be some. There are some versions
of RG 58 that are lighter -- and some heavier than RG142.
6) But even if you were to find a 50 ohm RG cable that was only half the weight
of RG142 (unlikely) and used that in an airpane like mine you would be saving
.9675 pounds. Not a trivial weight saving number, but not one that I would spend
hours on trying to accomplish.
OC
PS: I don't have any weight figure for RG 400, a copper stranded core coax of comparable
quality to RG 142. It may be a bit lighter.
One can discuss the merits of solid core versus stranded core with some valid arguments
on both sides. I've got both in my airplane.
PPS: If I were limited to using only one type of RG for everything it would be
RG 142.
Message 2
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| Subject: | Re: Weight of RG142 |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
Thanks OC,
--> AeroElectric-List message posted by: <bakerocb@cox.net>
>>AeroElectric-List message previously posted by: "Eric M. Jones"
<emjones@charter.net>
>>If RG142 is the only coax that is used in an airplane--about how much is
used
per airplane? (Now please don't say it depends...). I am trying to find out
how
much weight can be saved by changing to something else, and if
RG142 ONLY can be used for everything coaxial.
> The Belden catalog says that RG 142 weighs 4.3 pounds (68.8 ounces) per
100
feet. Or .688 ounces per foot.
>5) I don't know of any 50 ohm RG type coax that is significantly lighter
than RG142
(which has a solid steel core), but there may be some. There are some
versions
of RG 58 that are lighter -- and some heavier than RG142.
>6) But even if you were to find a 50 ohm RG cable that was only half the
weight
of RG142 (unlikely) and used that in an airplane like mine you would be
saving
.9675 pounds. Not a trivial weight saving number, but not one that I would
spend
hours on trying to accomplish.
>OC
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.
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
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
Message 3
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--> AeroElectric-List message posted by: Boddicker <trumanst@netins.net>
Listers, and Bob,
I know I have read about RG batterys on the list. Searched the archives for
an hour and was not rewarded.
Will a 17AH panasonic, or the like, turn over an 0-200?
It will be wired per Z-11.
I think I know the answer, but want confirmation before I order.
Thanks,
Kevin Boddicker
Message 4
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--> AeroElectric-List message posted by: "James E. Clark" <james@nextupventures.com>
The **Odessey PC680" <sp??> (17AH) turns O-320's and O-360's with no
problem. Thus I suspect that an O-200 can be handled.
James
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of
> Boddicker
> Sent: Saturday, May 15, 2004 8:50 PM
> To: Aeroelectric list
> Subject: AeroElectric-List: Batterys
>
>
> --> AeroElectric-List message posted by: Boddicker <trumanst@netins.net>
>
> Listers, and Bob,
> I know I have read about RG batterys on the list. Searched the
> archives for
> an hour and was not rewarded.
> Will a 17AH panasonic, or the like, turn over an 0-200?
> It will be wired per Z-11.
> I think I know the answer, but want confirmation before I order.
> Thanks,
> Kevin Boddicker
>
>
Message 5
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| Subject: | 6A gear weldment fit in a QB kit |
--> AeroElectric-List message posted by: "thomas a. sargent" <sarg314@earthlink.net>
I have a 6A quick build. In the QB kit the main gear weldment comes
pre-drilled AND the fuselage has been pre-drilled. The problem is the
holes in the two parts don't line up very well.
How can this be, you say, wasn't it all drilled in place in the fuselage
to start with? Apparently not. Bruce at vans tells me that they drill
the gear weldment to the spar, but they don't match drill it to the
fuselage. They drill those holes in the weldment on the bench somehow.
The holes in the gear weldment that lie along the wing spar, look like
they match the spar pretty well. But the group of 4 that penetrate the
fuselage just forward of the spar appear to be off by at least 1/8"
upward. My theory at the moment is that the forward piece that screws
to the side of the fuselage (those 2 holes line up rather well) is
actually about 1/8" too low. That raises the whole outboard end of the
weldment 1/8".
I gather many QB builders have similar problems with the gear weldment.
What have other people done about it?
Thanks,
---
Tom Sargent, RV-6A QB
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