Battery Position Options

[Andy Young]

Hello,

First, let me say that I am NOT looking to move my battery to the firewall, or under the passenger seat. For various reasons, I prefer to keep it in the tail. I do want to move it from its present position, to accommodate a ski tube along the right side.

I’m curious as to what the various locations are that have been used by the factory. Mine is along the right wall, about 27” aft of the cargo area rear bulkhead (27” from bulkhead to center of battery).

I’ve also seen them on the left side, right behind the bulkhead.

Have they ever been placed on the left side, about the same distance aft that mine is on the right? Figure if I use a position that has been previously used by the factory, the paperwork is that much easier.

[Otis]

I'm interested in moving my battery from behind the bulkhead to under the front right seat on my M5-235C. I'm recovering the aircraft so there are a lot of unknowns on fabric weight savings and the subsequent CG shift, but my rough calculations show that moving the battery puts me at the forward CG limit. Does anyone have any experience with how their aircraft handles with a significantly forward CG?

[Andy Young]

My M-6-235 is right at the forward limit with just me in it with no cargo. I rarely fly it that empty, but when I have, it’s flown just fine. I’ve never run out of elevator in the flair, which I have heard some people mention experiencing, but I think that may be down to technique: I don’t approach super slow; I’m typically keeping it at around 50-55 mph on short final. I am also carrying a little bit of power right until touchdown, so the prop blast over the tail helps. And I always wheel land.

[gbarrier]

Sounds like our M6s are a lot alike. With the three blade Hartzel we were pretty much there. When we installed the Odyssey battery in stock location we installed the 7 # ballast in the tail and maintained that CG. We recently put the old girl on a diet by installing the two blade MT prop. That moved things back a couple inches. Then we removed the tail ballast and put things back about where it was. Kind of like the way it flies like that. If the feds ever get around to approving the Earth X battery we will loose a few more pounds but should still be on CG.

[Otis]

Thx for the responses. Moving the battery will allow me to go to max gross weight without having to put part of the cargo strapped in the front seat. I’m going to also put the ballast weight bracket in the tail just in case. Thx again.

[gbarrier]

Ballast weight is Maule part number 1322B. Drawing is also 1322B. Installation instructions is drawing number 1301b Rev. B.

[Otis]

Thanks for the reference part and drawing numbers. I’ve found the hardest part of a repair/improvement is finding the correct drawing in the Veryon Publications App. I’ve looked for a search function, but I haven’t found one yet.
Having said that, the Maule team has been really helpful when I have a question or when the manuals are lacking.
Thx again

[Otis]

Before I started welding the fwd battery bracket in, I decided to doublecheck the wt and balance numbers. The fabric weight savings remains a big unknown. To try to quantify it, I cut a square foot of the original Razorback and Oratex. The Razorback weighed 3.6 oz, and the Oratex .5 oz. After doing a rough area calculation of the fuselage without the tail feathers, the weights were 28lbs versus 4lbs. The question is what that does the weight savings do to the GG? Decisions, decisions…!

[Andy Young]

Maybe weld the new battery bracket in, and hold off on removing the old battery bracket. Once the re-cover is done, you can then weigh the plane, calculate the CG, and decide whether to install a battery in the new location, or keep it in the old one. All you lose is the cost of installing the bracket, and the (minimal) added weight of the redundant bracket (which you could possibly remove later if you wanted to).

[asa]

I wish I had welded the under pax seat battery bracket in during my re-cover. With modern lightweight batteries, lightweight props, etc, it gives you more options for future changes and as Andy mentioned, the steel doesn’t weigh much. I’d like to have both

[Otis]

I really appreciate the inputs. I had talked myself out of it, but I have the new battery bracket and seat release latch, so there is no reason not to install it. Thanks again for the great ideas.