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buzzywph

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Any completed RV8 fliers out there with an IO-360 (180) hp glass cockpit and a constant speed prop give me any direction on where I should plan to put the battery (fwd or aft) based on CG considerations? Thanks, Bill N159WP.
 
As a wild guess, I would say it depends on:
and a constant speed prop
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i.e. which one? A Hartzell = almost certainly in the rear, a lightweight MT/Whirlwind it might be either...

Other factors might be what sort of battery, ignition, engine "extras" (e.g. inverted system), and whether you will worry about the aft aeros limit?
 
Rv8 bat location

Plan to use a Hartzell cs prop no inverted system with the concord 25rg battery. Thanks for your input. Most people I've talked with say the airplane is nose heavy with the battery upfront.
 
battery

Put it in the back. I ended up moving mine to the back. Glass panel and constant speed Hartzell.
 
Rv8 battery location

Ok, thanks that's what I thought. Did you end up using the Concord (23.5 lbs or the Odyssey 14.5 lbs) in back or something else?
 
battery choice

The Odessey is light enough that it doesn't matter nearly so much where you put it.
If you use the Concorde, you should definitely put it in the back. You can always switch to the Odyssey later with relatively little implications.
 
RV8 batt loc

Thanks Steve, that helps. As I will have a back up bat for the efis, I think the smaller bat in back makes overall sense for weight and CG.
 
My RV-8 has an 0-360 and Hartzel Constant Speed. It has the battery in the back. When flying solo or with a light weight person in the back, I keep my tool bag, survival kit and CLAW etc. in the back. The RV-8 lands a lot easier, in my opinon, with the CG towards the rear instead of on the front limits, as it would solo with no weight in the back. Put it in the back!
 
Tom Schad said:
My RV-8 has an 0-360 and Hartzel Constant Speed. It has the battery in the back. When flying solo or with a light weight person in the back, I keep my tool bag, survival kit and CLAW etc. in the back. The RV-8 lands a lot easier, in my opinon, with the CG towards the rear instead of on the front limits, as it would solo with no weight in the back. Put it in the back!
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I agree with Tom. My -8 has an O-360 with a Whirlwind 200C prop and the lightweight Oddessy battery in the FRONT.

My empty weight is about 1,050 #, and flying solo it's a little nose heavy. No issues landing-wise, but pitch forces get a little heavy when doing acro.

Next time I'd put the battery in the back.

FWIW
 
Battery Location

-8A with Aerosport 180 HP IO-360, Hartzell CSP and AFS 4500/Garmin 496/TruTrak ADI2 and Oddessey (SP?) forward mounted battery. Empty weight 1122 lbs.

Have an in-limits forward CG that I counteract with 50 lbs of lead shot ballast in the aft baggage compartment. Decided to accept forward CG rather than run battery wires through the cockpit - and deal with aft-mounted access issues.

Agree that forward CG is harder to land. Have determined there is no way I can exceed aft CG limits - even with King Kong in the back. Wife won't fly so I'm mostly solo.
 
Put it in the back

Us old heads that have been flying the RV-8 for over a decade have repeatedly told builders to put the battery in the back. Still builders continue to put them in the front and rationalize their choice. I can't see putting lead shot in the back to offset a nose heavy RV-8 that has the battery mounted on the firewall. Does it not stand to reason that if you are going to put lead in the tail to control the CG, that it should generate electrical power for you? What is in a battery that makes it so heavy? That's right...lead!

I met an RV-8A builder who told me he put 40 lbs of lead in the tail in-order to balance his RV-8A. I said, let me guess........you put the battery on the firewall right? Duh!

There is another active thread about 3 point landings vs wheel landings in the RV-8. Most guys say that the 8 will three point easier with a passenger in the rear. I wonder why? Could the RV-8 flown solo be nose heavy making it difficult to full stall? Just a thought!

Rear battery access is easy with the installation of a door over the battery in the rear shelf. I can pull the Doll's battery faster than if I had to remove the cowling to get to it. Another plus for a rear mounted battery is that they last years longer since they are not in the heat of the engine compartment. Just another thought!
 
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battery

Danny, I met ya at Oshkosh last year and took a bunch of pictures of your 8. You were very helpful answering my questions, and yes my battery is in back thanks to you. Just wanted to say thanks for your time.

Mike McKelvey
 
Danny King said:
Us old heads that have been flying the RV-8 for over a decade have repeatedly told builders to put the battery in the back. Still builders continue to put them in the front and rationalize their choice. I can't see putting lead shot in the back to offset a nose heavy RV-8 that has the battery mounted on the firewall. Does it not stand to reason that if you are going to put lead in the tail to control the CG, that it should generate electrical power for you? What is in a battery that makes it so heavy? That's right...lead!

I met an RV-8A builder who told me he put 40 lbs of lead in the tail in-order to balance his RV-8A. I said, let me guess........you put the battery on the firewall right? Duh!

There is another active thread about 3 point landings vs wheel landings in the RV-8. Most guys say that the 8 will three points easier with a passenger in the rear. I wonder why? Could the RV-8 flown solo be nose heavy making it difficult to full stall? Just a thought!

Rear battery access is easy with the installation of a door over the battery in the rear shelf. I can pull the Doll's battery faster than if I had to remove the cowling to get to it. Another plus for a rear mounted battery is that they last years longer since they are not in the heat of the engine compartment. Just another thought!
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Could not have said it better Danny, I guess I am also one of those old heads who started flying the 8 over 10 years ago. I think I copied your rear shelf access door among other things and yes it is easier than the firewall.
 
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As usual Danny has it right but from painful experience let me emphasize that you need to put a BIG access door back there to get to the battery and master contactor. Mine has a small door that allows me to get to a battery charging plug. Bad choice.

Pulling the rear baggage floor is a PITA.
 
Fixed pitch?

Just wondering about the battery placement myself and I'll be going fixed pitch.

Will placing the battery in the rear with a fixed pitch setup be an issue?

Thanks

Don
 
Im building my RV light. No primer, basic instruments, lightweight starter/generator, electronic ignition, Catto 2 blade, O-360 ellison carb.. I have a small odyssey on the firewall. My plan is to have a small weight to bolt on to the tailwheel IF needed for aerobatics...:confused:
 
Don, I just did a little experiment that may help you. My plane has an empty CG of 77.8. Solo and full fuel I'm at 80.4. If I were to have the Odessey battery aft, my solo + full fuel CG would be at 81.2

For reference, the RV-8 CG envelop is 78.8 to 86.82
 
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Light airplane battery placement

Don Patrick said:
Just wondering about the battery placement myself and I'll be going fixed pitch.

Will placing the battery in the rear with a fixed pitch setup be an issue?

Thanks

Don
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Don,
If you are going light with and 0320 and a wood or composite prop, you could get by with a light Odyssey battery on the firewall.
Most builders fly solo most of the time. We're talking 90% plus here! It's nice to have your plane fly best, the way you fly it the most.

The big tradeoff is the Bubba factor. The heavier the engine and prop, the larger the Bubba you can carry in the rear seat. I have carried a 260 pound passenger in the Doll and still been within limits. She was plenty light in pitch but still stable. My battery is a full 25 amp aircraft battery, with the starter and battery relay mounted on the battery tray.

If I had an 0360/Hartzell instead of my I0360A1B6/Hartzell then my limit would probably be more like 220 lbs. If I had an 0320/composite prop then maybe 200 would be my limit. You get the picture.

If you can put lead in rear cargo compartment to move the CG aft, then you can put it in the forward cargo compartment to move the CG forward. The best course of action is to set your 8 up to fly great when you are solo as that will be your primary mission.
 
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Thanks

Thanks folks,

I'll be putting a IO-360 in with the fixed pitch, and I have a few bubba's that will probably try to squeeze in someday.

For the most part, I plan on lots of x-country with the boss in the back, and of course the occasional solo aero flights.

Thanks gents.

Don
 
LiFePO4 batteries weigh 20% of the equivalent Lead Acid type.
Some builders / fliers are discussing and / or using them in RVs. They have been well received in other powersport equipment, and have a good safety record. (unlike previous LiPO types used in RC gear)
So I put the PC680 in the back of my RV-8 with the solonoid and the strobe power pak attached to the battery holder to save weight via multi-tasking.
If I need to reduce the weight in the tail, I could drop about 10.5 pounds by switching to a Shorai LFX36A3-BS12 LiFePO4 battery.
My initial W&B tuned out well, so I'll continue to Get-er-done. Maybe later I'll fine tune the W&B if it becomes an issue. Right now I'm glad I went with the sage advise given here.
 
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Danny sums it up pretty well. And in my own experience, every pilot complaining about landing issues with the RV, when asked, put his battery on the firewall. Regardless of what type of battery you are going to use, there seems to be few truly rational reasons to mount it forward. The benefits do not seem to outweigh the downsides. Conversely, other than the extra bit of expenditure in Battery Cable, there seems to be no real downside to mounting it after of the baggage. The RV-8 responds well to this location. it IS a nose heavy aircraft and any weight you can move aft is good. Put the ELT and the Battery behind the baggage. Like Dan said in a kinder and gentler way, putting lead weight back their is simply not logical.
 
Some numbers of PC680 in front vs rear

My RV-8 weighs 1112 empty and has its CG at 77.77. If I put 230 litres of fuel in, plus me at 200 lbs, total weight is 1542lb. If I burn off the fuel down to 30 litres the CG moves from 79.922 to 79.91 inches. The permitted range is 78.7-86.82, so it's well forward in the envelope. I have a Superior IO-360 and Hartzell c/s prop, plus PC680 battery IN THE BACK.

A PC680 weighs 14.6lbs, its lever in the firewall position is about 50 inches; in the rear position it must be about 140 inches (plane in hangar, me at work). So I reckon moving the battery from the rear to the front would move the CG from 77.77 to 79.07 at the start of the flight and 78.93 at the end - gonna be fun trying to 3-point that baby!

With the same amount of fuel and 260lbs of passenger in the back seat, the total weight is at the maximum, CG still in limits tho well aft (85.31 to 86.27).

Hope that helps some.

Chris
 
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