J

John Cardiff

Member
Hi Everybody

I am new to the forum and this is my first post.

I am halfway through the fuselage and planning the electrical system and looking for feedback on the location of the battery and its affect on CG.

I am planning on an IO 360 M1B and a constant speed prop. Let me know if you had to do it over again where would you put your battery and why.

Thanks in advance for your help.
 
John,

There is much written on this forum about battery location and the general consensus for the 8 is somewhere in the back rather than the front for the constant speed prop.
Go to the search key at the top of the screen and look for battery location rv8. You see all the reasons why.

Best

Matt Hurley
RV8 Finish/Engine/Avionics
Hobe Sound FL
 
tonyjohnson said:
Put the battery in the back.
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Absolutely, put the battery in back. I have mine in back, and I have an IO-360-A3B6D with a Catto prop. My CG is just a bit on the nose heavy side solo. My buddy has an O-360-A1A and a FP Sensenich with the battery in front and he is VERY nose heavy. In fact, when he is solo, he normally puts a bag of gravel in the back seat. I'm not sure if he really needs it, but he says the airplane handles much better with it there.

Cheers
 
Thanks for the input.

I had talked with an RV-8 owner who felt with the battery in the back and a passenger his CG was to far to the rear. On landing he was using foward stick to control the flare.

I'll plan on a rear battery, on that note any comment on types of battery to use.
 
I agree that it's almost certainly better to mount the battery in the rear with the IO-360 and a C/S prop.

When listening to reports of how one configuration vs another works, you need to consider the fact that older planes almost all used the heavy Concorde battery, and almost all planes today are using the much lighter Odyssey. This would amount to about a 10 lb difference, which is fairly significant in the aft position.

FWIW, my friend and I each built RV-8's about 6 years ago. Both were O-360 engines, but he had a C/S prop, and I had a FP Sensenich, which is only about 10 lbs lighter than the C/S. He mounted his Concorde battery on the firewall, and I put mine in the aft location.

My plane was much better to fly solo, as he can run out of up trim on final. My plane was also a bit faster, which I think was due to the more aft CG. On the other hand, I had to limit rear passenger weight much more than he did, but if there's any baggage involved, the front compartment can even out the score.

My current RV-8 is nearing completion, and it has an O-360, and C/S prop. This time around, I chose to mount an Odyssey battery on the firewall. I'll mount my permanent tool kit, tie downs, canopy cover, etc in the rear of the aft baggage compartment, rather than in the front compartment like I did before.

Bottom line, everything is a compromise. Nose heavy is better for large passengers and baggage, but being neutral is better for solo flying.

Cheers,
Rusty
 
John Cardiff said:
Thanks for the input.

I had talked with an RV-8 owner who felt with the battery in the back and a passenger his CG was to far to the rear. On landing he was using foward stick to control the flare.
QUOTE]

I haven't flown an RV-8 yet, and have heard similar things a couple times. Is forward stick needed in the flare because the trim limit is farther nose-up than needed with that CG position (so more forward trim would eliminate the problem)? I would imagine it's not some sort of instability region in which higher pitch requires more down elevator to maintain, right?

Brad
No RV yet
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We are planning on XP-(IO)360 and Hartzell C/S. Figures seem to suggest can get out of Fwd CG Limit Solo with Fwd Battery - let alone how it feels. Moving 23lb battery to rear moves basic CG ~2".

Compromise we're going for is allowing for either config. 2nd Battery Tray is $15.60. Will see where basic CG ends up, and even how it feels. 1 conduit from rear locaton to front and you can choose / change your mind. Even more, if you were to need ballast you have a location to just bolt a duf battery :D
 
You definitely want it in the back. I have an O-360-A1A with Hartzell CS prop. It is nose heavy when flying solo (I'm 165 lbs.) It just gets worse with heavier engines as any of IO-360 guys will tell you. When I was building I considered putting the battery up front like Van suggests but every -8 pilot I spoke to urged me to put it in back. I'm glad I listened.

Chris
 
RV8 Battery

I have built two RV8's, the first with an IO360 CS and the second with an 0360 CS. Both are nose heavy solo even with the battery in the back. From my experience there is only one option on the 8 and that is in the back. Also I have tried both the concord and odyssee battery's. Odysee is the best choice in my opinion. With the Odysee you can modify the battery tray by reducing its depth to match the Odysee. This will allow the fwd edge of the tray to remain in the location identified by the plans and allows the aft edge to come forward which moves the cables and battery further fwd of the elevator bell crank. Also you should purchase the Odysee box and permanantly attach it to the tray. This makes a much cleaner and safer installation.

Pat Stewart
N184PS
 
I agree with the others, put it in the back IF you are going with any of the Hartzells. With either of the Whirlwind models you can put it forward (best behind the firewall in the bottom of the fwd baggage compartment) and it works out nicely. The effect of taking 20-30 lbs off the nose is NOT subtle. Don't worry, you will still have plenty of CG window for bubba and his baggage if you put it in the back. See the comments toward the bottom of this page on weight and the effect on the plane...
http://www.romeolima.com/RV8/Prop.htm
 
Grove gear effect on CG

In addition to battery in the back, would the lightweight Grove gear induce a substantially favorable effect on the the slightly nose heavy CG? What about the weight of the nose gear in an 8A?
 
I've heard that the 8a's are not as prone to being nose heavy since there are no gear boxes and the mains are behind the CG. Is this truly the case?
 
Ok new question about the same subject. I have a 0-320 FP, most flying will be solo, I am 220 lbs. should I put the battery in the back to forgo the "bag of gravel" to make it fly good solo? Also has anyone put in a 28vdc battery? Seems that finding radios and things are easyer if you have a 28vdc system.

Jeremy
finish kit
N282RV
 
8A Nose Heavy

Guy Prevost said:
I've heard that the 8a's are not as prone to being nose heavy since there are no gear boxes and the mains are behind the CG. Is this truly the case?
Click to expand...
My second RV8 is an 8A, just as nose heavy as the 8.
 
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