jzinckgra

My Feedback: (11)

I have a DC F20 Tigershark that I built ~6 years ago. I am finally thinking of taking her out of the closet to fly her, but can't decide what to do about the battery pack (s). The plane has mechanical retracts (hobbico) and from what I've read here, they tend to bend easily, which could potentially drain thr Rx battery. I came across 2 threads that stated how one can hook up 2 battery packs:

1) plug one pack into the "bat" slot and the 2nd pack into an aux. slot. From my understanding, if the primary pack drops below a certain voltage, the 2nd pack takes over. This is fine and dandy, but what if my retracts jammed and caused the draining of both packs? My flights are generally short (usually no longer than 5 minutes or so/flight), so is it even possible for both packs to be drained if the gear got jammed. I should mention that I generally use 4.8V, 700maH packs and this plane has two retract servos + throttle, aileron, elevator and rudder.

2) Another thread briefly described a way to get just one of the packs completely dedicated to the retracts. Something about cutting the red wire here and splicing the white wire there. I'm not very good with electronics, so a better description would be helpful. I like this setup better because even if the retracts get jammed and drain the battery, at least I still have control of the plane. The worst case scenario, I belly land the plane.

Finally, my only other concern in using 2 NiCd packs is the weight. PLane should still fly ok, but would rather keep it as light as possible. I thought about NiMH packs in this case.
Also, what about just going with one large capacity NiMH and just hope that if the gear jams, it won't drain the battery. Plus I would get some benefit in weight savings. Thanks for your help/advice.

Campy

My Feedback: (1)

Instead of 2 packs, keep it simple. Use ONE NIMH pack of 1200 mah (or larger ). It will most likely weigh less than 2 packs and it will provide you with more than enough power for several flights. If the retract servo does "jam", you will have plenty of reserve to be able to land it.

If the present pack is 6 years old, I STRONGLY suggest you cycle the pack SEVERAL times and make sure it is going to hold a charge before putting it in ANY plane. I am not saying the pack is bad, but after 6 years I would be leary of it until it proved itself.

For your retracts, make sure the push rod/wire from the servo has a straight run. Also make sure there is no binding and if you can run the push rod/wire in a supported tube that also minimizes any bending. The bending MOST people are refering to is with the struts. The struts are probably 5/32" (MAYBE even 1/8" because of the age ). Check the retract unit. Many of them can be drilled out to accept 3/16" struts.

Hope this helps.

VACATION OFFICIALLY STARTS AT MIDNIGHT !!!

Stick Jammer

Well, this is how two battery packs of the same voltage (same number of cells) can be used for redundancy but they will both drain equally, not one at a time. If you want true isolation of a separate battery for your retracts just cut the red wire on the retract servo lead and tie it directly to the red wire from the switch lead that would normally plug into the receiver. The servo lead and the battery lead from the switch will still be plugged into the receiver but without the red wires. This will supply separate power to the retract servo but the negative and signal wires are still attached to the receiver. Any bending of the retracts usually happens on landing. If you check them out after each landing you can usually catch a potential problem before the next flight.