Thanks GB, That battery up front is a simple and reliable solution for certain problamatical airplanes that I have used since the seventys. These three pictured are just my current ships using it with exception of the big Yak as thats just a weight box.

Interestingly enough I first tried it with one of my first electric over the wire throttle systems on a controlline airplane long ago in LA and there has been an occassional RC ship ever since that the forward battery has proved very usefull on.

It can make a hugh diff on many snub nose airplanes and your lovely F4B is a prime example a ship I would have used the nose battery from the start.

Folks have been telling me for years that it won,t work because of heat and vibration, well I proved them wrong. I beleve depending on how you build the box that there is no additional vibration and that the batterys run cooler than in more common heavily insulated locations.

I always put the battery where it needs to be. Heck I have one airplane with two .25's on it that the battery is located all the way in the rear under the leading edge of the stabilizer, and when I tow it up as a glider droping the engines off the battery is relocated to a spot all the way in the tippy tip of the nose and plugged into at waiting Y corded lead to the Rx.

John

Concerning the the weight box I used in that big Yak, I would like to express the reasoning here over the common method used by simply cementing lead or whatever into the insides of a removable glass cowl, using the box has a big advantage.

That advantage is the wear and tear of the cowling itself and its mounting holes, blocks and so on when a substancial weight is added to it. Even a simple nose up episode can cause considerable damage with all the added weight stress on the cowl itself.

John

First off I have never given the battery box any thought, it just never landed in the gray mater when I was doing that thinking stuff. I have used a lead box up front. When I was building the Boeing I measured where the designer had the CG marked using the 25% rule, it was way off. I mentioned this to my mentor and he said that Mr. Tanzer had built a bunch of these planes and would know wher the CG was so go to the plans. Not that the inker could have messed up or anything? Anyway, the plane came in right at the advertised weight of 12 pounds. Maiden day I still mentioned the CG to my mentor, he was doing the maiden. As the plane lifted off I heard my mentor swearing at a plane for the first time and noticed how the wings were rocking and the tail was way down. He got it landed then in the pits we CGed it at my marks with wrenches and tools sitting on the nose. When it balanced out he removed the wrenches and handed them to me, said there, you ned that much weight to set the CG. The wrenches weighed in at almost 3 pounds. The cowl I made is really thick glass and it mounts like no other so in this case the lead in the cowl worked out without cracking the glass or breaking the mount on a hard landing. If it was a store bought unit it would have been dead years ago.
Just for grins I may set the plane back up for flight again this summer and mount both Sub Cs like you showed. That should lighten it up a lot!! Getting them up front farther should also get the CG where I want it without all that lead. Maybe the plane wouldn't be such a slug if I could remove three extra pounds? Do you think???

"Folks have been telling me for years that it won,t work because of heat and vibration, well I proved them wrong. I beleve depending on how you build the box that there is no additional vibration and that the batterys run cooler than in more common heavily insulated locations." John,

I believe your method of mounting the battery without consideration to vibration (and probably to a lesser extent, cooling issues primarily with heat soak after running the engine) is a bit of a Russian roulette affair. You have not proven doubters wrong - you simply have been getting away with it up to this point. You may run out of luck on your next flight.

Our batteries, regardless of type, are not immune to vibration and can suffer shortened lives or (worse) sudden and catastrophic failure. Internal shorts across insulators can happen, solder joints can fail, and interconnection spot welds can break. If you lose your flight battery suddenly and completely, you have no chance of fail safe and will of course be completely out of control. This will obviously likely lead to complete destruction of the model under the most fortunate circumstance, and worse could lead to injury or worse to someone nearby. It is just not prudent and safe operation.

Any radio system instructions I have ever read have been careful about advising isolation of the battery and receiver from vibration. It is one of the first things newbies learn.

I found a good write-up from a battery seller sent as advice to a modeler who was doing the same thing as you have been doing. I refer you to the following link:
http://www.rcuniverse.com/forum/m_38...tm.htm#9173261 See posts 1289 and 1292.

I by no means intend to criticize or flame anyone, and appreciate the efficiency of keeping the model as light as possible, but I feel strongly about this being a safety issue and discourage anyone from mounting a battery in this manner.

littlera

Littlera - That link you posted chiefs complaint is fear of the Rx pack close to ignition interferance, please note There are no ignition systems on the two ships I posted with the forward battery and none in the past have had ignition systems either.

Please feel free to ignore the technique however I will continue to use where applicable in some airplanes where required as I have since that first controlline airplane with a four cell pack tucked up in next to the engine, and by my best reckoning I think five other RC aircraft before the two current ones.


John

Excerpts from Steve at http://www.hangtimes.com/ (battery supplier)
:

... high temps affect any battery system. When the pack is hot, impedance is impacted, voltage is depressed, ability to accept a charge reduced, useable capacity is reduced, etc. Also worthy of consideration, vibration can pop welds, break down internal insulators and lead to catastrophic failure. Quickly.
.....That is NOT a suitable location for an Rx/Servo pack... period. Ignition pack, maybe.. with some precautions as indicated above. But the Rx pack up there.... never. Too close to the ignition field, too hot, too much vibration. As an Ignition pack.. ignition failure; you are a glider. Rx pack failure.. you are a pile of sticks. Rule of thumb.. don't mount a battery pack where you would not mount a receiver.....

Yes, I see that he warns against the R/F problems associated with a gas engine, but would not characterize the thrust of his concerns as R/F. It is one of three, with vibration and heat being the other. Why would you not want to eliminate these threats to the safety of those around you, not to mention the security of your aircraft?

littlera

Do as you wish sir, I have proven it works just fine with a number of aircraft when installed as I have and you are free to stay inside your box if you like.

John