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Aft Battery

 
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Dan.Beadle(at)hq.inclines
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PostPosted: Fri May 26, 2006 6:31 am    Post subject: Aft Battery Reply with quote

I am going to mount the battery in my RV8 aft of the baggage area. Vans
wiring kit suggests airframe grounding. Bob Knuckles Z Diagrams
recommend a separate (but heavy) ground cable from the battery to the
engine mount. =20

=20

I am considering a separate ground run. I am also considering a
separate ground for accessories (strobes, Nav, landing lights, pitot,
etc.)=20

=20

Is this worth the extra weight? What are other builders doing?=20

=20

I was burned by the lack of a ground run in my StormScope installation
in another airplane, but don't intend to have one in this airplane. So
am I being overly cautious at the expense of precious payload?


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searle(at)mansfield.net.a
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PostPosted: Fri May 26, 2006 2:47 pm    Post subject: Aft Battery Reply with quote

Hi Dan,

On my almost completed RV8,I have the rear battery and have run a separate
ground cable to the firewall. My suggestion is to do the same, especially
if you intend to use a 17 AH battery like the oddessy.

Cheers ..... Alan Searle ..... Australia.



Dan Beadle writes:

Quote:


I am going to mount the battery in my RV8 aft of the baggage area. Vans
wiring kit suggests airframe grounding. Bob Knuckles Z Diagrams
recommend a separate (but heavy) ground cable from the battery to the
engine mount. =20

=20

I am considering a separate ground run. I am also considering a
separate ground for accessories (strobes, Nav, landing lights, pitot,
etc.)=20

=20

Is this worth the extra weight? What are other builders doing?=20

=20

I was burned by the lack of a ground run in my StormScope installation
in another airplane, but don't intend to have one in this airplane. So
am I being overly cautious at the expense of precious payload?
















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Michael Wynn



Joined: 10 Jan 2006
Posts: 148
Location: San Ramon, CA

PostPosted: Fri May 26, 2006 3:05 pm    Post subject: Aft Battery Reply with quote

Hey, Alan

What do you suppose the weight penalty is for the cable runs? I am building
an RV 8, was planning to use dual batteries and am trying to figure out
where to put them. I understand that RV 8's have a tendency to be nose heavy,
especially with a CS prop. It certainly looks like running a ground to the
engine would be a good idea. I suppose if you put both batteries behind the
back seat you could run one big ground and two hot lines. Just curious about
the weight penalty involved.

Regards.

Michael Wynn
RV 8 Wings (tanks)
San Ramon, CA


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Michael Wynn
RV 8
San Ramon, CA
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rickrv8(at)msn.com
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PostPosted: Fri May 26, 2006 5:32 pm    Post subject: Aft Battery Reply with quote

I designed my electrical system in my -8 based upon Bob's =
recommendations. I am using two Odyssey batteries mounted in the back =
primary for the dual electronic ignition. Contrary to Bob's advice to =
ground at the firewall, I grounded both batteries to the nearby =
longerons. Operationally, the electrical system has worked fine and I =
have experienced no noise in the communication radios or other avionics.

Rick McBride=20
---


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searle(at)mansfield.net.a
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PostPosted: Sat May 27, 2006 3:25 am    Post subject: Aft Battery Reply with quote

Michael,

I have not done any calculations on the weight penalty of the extra ground
cable. However I have considered the situation if I chose to put the
battery at the firewall. As I have a 200HP Lycoming with C/S prop, the
aircraft would be too nose heavy for solo flight and would require ballast
in the aft baggage area.

Therefore, in my case, with the battery at the rear, the extra weight is of
no consequence. (just the extra weight).

Cheers ..... Alan.







MLWynn(at)aol.com writes:

Quote:


Hey, Alan

What do you suppose the weight penalty is for the cable runs? I am building
an RV 8, was planning to use dual batteries and am trying to figure out
where to put them. I understand that RV 8's have a tendency to be nose heavy,
especially with a CS prop. It certainly looks like running a ground to the
engine would be a good idea. I suppose if you put both batteries behind the
back seat you could run one big ground and two hot lines. Just curious about
the weight penalty involved.

Regards.

Michael Wynn
RV 8 Wings (tanks)
San Ramon, CA















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luckymacy(at)comcast.net
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PostPosted: Sat May 27, 2006 6:04 am    Post subject: Aft Battery Reply with quote

Rick,
Where did you mount your strobe pack(s) and where/how did you ground them.

I have a situation where as soon as I fire up all the electronics and the Strobes and the first time my radio receives a transmission after startup, I go from wonderful silence in my headsets to faint pulse noise that coincides with the strobes firing off.

lucky

-------------- Original message --------------
From: "Richard McBride" <rickrv8(at)msn.com>

[quote]

I designed my electrical system in my -8 based upon Bob's =
recommendations. I am using two Odyssey batteries mounted in the back =
primary for the dual electronic ignition. Contrary to Bob's advice to =
ground at the firewall, I grounded both batteries to the nearby =
longerons. Operationally, the electrical system has worked fine and I =
have experienced no noise in the communication radios or other avionics.

Rick McBride=20
---


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flyeyes(at)mac.com
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PostPosted: Sat May 27, 2006 6:09 am    Post subject: Aft Battery Reply with quote

I thought I'd add my $.02 here...

I'm flying a 200HP angle-valved RV-8 with a CS prop, and firewall
mounted battery. Because I used a very lightweight prop (Whirlwind
151) my CG is fine, even with the forward mounted battery.

You can look on Dan Checkoway's site for his W&B database
(rvproject.com), mine is N9TN with an empty CG at about 78.5" aft of
datum. I don't have to ballast for solo flight, and in general have
a very forgiving CG range. Many 180 hp/Hartzell equipped RV-8s have
a heavier firewall forward than mine, and a more forward CG.

Also, Eric Jones sells lightweight copper-clad aluminum wire that is
ideal for these longish runs for an aft battery. I haven't used it
myself, but would if I needed an aft battery (www.Periheliondesign.com)

James Freeman
On May 27, 2006, at 6:21 AM, Searle, Alan wrote:

Quote:

<searle(at)mansfield.net.au>

Michael,

I have not done any calculations on the weight penalty of the extra
ground
cable. However I have considered the situation if I chose to put the
battery at the firewall. As I have a 200HP Lycoming with C/S prop, the
aircraft would be too nose heavy for solo flight and would require
ballast
in the aft baggage area.

Therefore, in my case, with the battery at the rear, the extra
weight is of
no consequence. (just the extra weight).

Cheers ..... Alan.

MLWynn(at)aol.com writes:

>
>
> Hey, Alan
>
> What do you suppose the weight penalty is for the cable runs? I
> am building
> an RV 8, was planning to use dual batteries and am trying to
> figure out
> where to put them. I understand that RV 8's have a tendency to be
> nose heavy,
> especially with a CS prop.(snip)
>


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rickrv8(at)msn.com
Guest





PostPosted: Sat May 27, 2006 8:28 am    Post subject: Aft Battery Reply with quote

Lucky,

I have the Whelen strobe power pack mounted in the tail just behind the =
rear baggage bulkhead. I did run the strobe ground wire back to my =
common grounding bus that is located near the instrument panel. I don't =
have any strobe noise. I'm familiar with the pulse noise you're =
describing. I used to get the same noise in my old RV-6.

Rick McBride
---


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Speedy11(at)aol.com
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PostPosted: Sat May 27, 2006 5:10 pm    Post subject: Aft Battery Reply with quote

Dan,
Here's another idea for you. There is a longeron that extends the length of
the fuselage. It passes slightly above where your battery will be in the
back. Ground your battery to that longeron and take a ground cable from that same
longeron near the firewall and connect it to your grounding block. Not much
better grounding cable than solid metal front to back and it saves a
bucketload of weight (opps, that's one of those undefined terms that Bob frowns on).
If you're worried about drilling too many holes in the longerons, you could
drill out one or more rivets at the front gusset and rerivet the grounding cable
to the longeron at the gusset (you'd have to devise an attachment to the cable
to would be large enough to rivet).
Stan Sutterfield
www.rv-8a.net
I am going to mount the battery in my RV8 aft of the baggage area. Vans
wiring kit suggests airframe grounding. Bob Knuckles Z Diagrams recommend a
separate (but heavy) ground cable from the battery to the engine mount.

I am considering a separate ground run. I am also considering a
separate ground for accessories (strobes, Nav, landing lights, pitot,
etc.)

Is this worth the extra weight? What are other builders doing?

I was burned by the lack of a ground run in my StormScope installation
in another airplane, but don't intend to have one in this airplane. So
am I being overly cautious at the expense of precious payload?


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martin(at)gbonline.com
Guest





PostPosted: Sat May 27, 2006 6:20 pm    Post subject: Aft Battery Reply with quote

Dan,
I experienced a very difficultproblem when I built my RV8 6 years ago. I
installed the battery aft of the elevator bellcrank which satisfied the
balance problem caused by the IO390 engine. I unwittingly attached the
ground cable to the airframe near the battery in the aft section of the
fuselage. By doing this I created what is known as a "ground loop" in
electronics jargon. It caused me no end of "electronic" problems primarily
with the autopilot and avionics problems. After doing everything possible
to cure the problem, I was advised that I probably had a ground loop that
was causing my avionics problems. I promptly rewired my electrical system
by changing the ground cable from the battery to the fuselage to a cable
ran parallel with the power cable to the firewall and on to the engine .
This eliminated the ground loop and also elimated all of the electronic
problems that I was experiencing. I hope that this helps all of you.
Dick Martin
RV8 N233M
the fast one

---


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Nic(at)skyhi.flyer.co.uk
Guest





PostPosted: Sun May 28, 2006 3:31 am    Post subject: Aft Battery Reply with quote

Quote:
Is this worth the extra weight? What are other builders doing?=20

Hi, A forward battery goes against current thinking, but for what its
worth, here is my experience.

Even with the rear placement of your battery the CofG issue is not
satisfactorily resolved and you will still usually require rearward ballast
to counter the problems with heavy stick forces and handling, particularly
if you have a C/s prop.

In deciding on the battery location I used electronic car rally scales and
Kevin's great Excel spreadsheet, we tried all the different options and
looked at the change in CofG. In the end I decided to install the battery in
the recess in the front baggage bay. One great advantage is that the cable
runs are short and no problems with earthling through the longerons, and
this allows for a lightweight, compact battery, and probably saved several
pounds.

Being close to the engine, but rear of the firewall seems a great
compromise.

As for Cof G, If I am flying alone I use two sail bags in the rear luggage
locker which fill the space and cant move when doing aeros.

If I have a passenger then I remove the sail bags and my Cof G is perfect.
Compare this with a long cable run, which adds weight particularly when
used in conjunction with a big battery. My build came out at 1112 lbs with
a full Christen inverted system and MT C/s prop which is not the lightest,
but reasonable.

Best Rgds, Nic


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chasm711(at)msn.com
Guest





PostPosted: Sun May 28, 2006 9:58 am    Post subject: Aft Battery Reply with quote

I agree with Nic

My setup is with the battery aft, MT prop heavy engine, extensive avionics,
grove gear and otherwise standard airplane. My weight came out at 1170 lbs
and CG slightly aft. I can carry a 220 lb person in the back but no more
and no aft baggage if that person is on board. Works ok for me and my wife
(she doesn't weigh near 220 but makes up for it with luggage Smile I would
have been happier with the battery forward in the well in the forward
baggage compartment. Shorter wire runs, less wire weight and better
balance. I am considering using a smaller battery aft but so far the
current setup works ok. It's hard to change things that work when flying is
more fun.

Paul Schattauer
RV8 808PS

Quote:
From: "Nic" <Nic(at)skyhi.flyer.co.uk>
Reply-To: rv8-list(at)matronics.com
To: <rv8-list(at)matronics.com>
Subject: Aft Battery
Date: Sun, 28 May 2006 12:24:05 +0100



> Is this worth the extra weight? What are other builders doing?=20

Hi, A forward battery goes against current thinking, but for what its
worth, here is my experience.

Even with the rear placement of your battery the CofG issue is not
satisfactorily resolved and you will still usually require rearward ballast
to counter the problems with heavy stick forces and handling, particularly
if you have a C/s prop.

In deciding on the battery location I used electronic car rally scales and
Kevin's great Excel spreadsheet, we tried all the different options and
looked at the change in CofG. In the end I decided to install the battery
in
the recess in the front baggage bay. One great advantage is that the cable
runs are short and no problems with earthling through the longerons, and
this allows for a lightweight, compact battery, and probably saved several
pounds.

Being close to the engine, but rear of the firewall seems a great
compromise.

As for Cof G, If I am flying alone I use two sail bags in the rear luggage
locker which fill the space and cant move when doing aeros.

If I have a passenger then I remove the sail bags and my Cof G is perfect.
Compare this with a long cable run, which adds weight particularly when
used in conjunction with a big battery. My build came out at 1112 lbs with
a full Christen inverted system and MT C/s prop which is not the lightest,
but reasonable.

Best Rgds, Nic



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