Dynaflite 3 Meter BOT Elevator Servo Recommendations

[Vulture]

I'm assembling a Dynaflite 3 meter BOT. And one thing I'm probably worrying about a little too much, is the elevator servo. I've seen recommendations that run the gamut from a sub-micro servo and up. I was thinking of putting the lightest servo that would have the "at least 15 oz of torque" recommended in the building instructions. I have some D47s that I've been using in DLGs. Very light and 15.2 oz of torque. With the mindset of building light for flying, not heavy to withstand a crash. Or possibly a D60, just a few grams heavyer and 20-24 oz of torque depending apon what chart you read.

This is my first large glider and I was wondering if some of you more experienced flyers might offer your thoughts on the right servo to put in the tail.

Thanks,
Vulture

[Stan_in_AR]

However, I wouldn't put it in the tail as this will require about 2.5 oz in the nose, this might not be too bad as the BoT can handle weight pretty well. It seems to me that the Dynaflite model is fairly "porky" so any weight you can save is worth saving.

I'd put the servo up front and run a carbon rod back to the elevator control horn.

Don't worry about a 15oz servo for each spoiler

Stan






I'm assembling a Dynaflite 3 meter BOT. And one thing I'm probably worrying about a little too much, is the elevator servo. I've seen recommendations that run the gamut from a sub-micro servo and up. I was thinking of putting the lightest servo that would have the "at least 15 oz of torque" recommended in the building instructions. I have some D47s that I've been using in DLGs. Very light and 15.2 oz of torque. With the mindset of building light for flying, not heavy to withstand a crash. Or possibly a D60, just a few grams heavyer and 20-24 oz of torque depending apon what chart you read.

This is my first large glider and I was wondering if some of you more experienced flyers might offer your thoughts on the right servo to put in the tail.

Thanks,
Vulture

[O.L. Adcock]

Vulture, I put a Futaba S3114 in my wife's BOT, works fine. Stan, The geometry in a BOT won't allow a straight push rod. I'm afraid by the time you ran a push rod to a bellcrank, then up to the flying stab, you'd wind up with the same or more weight then using the servo alone....O.L.

[Vulture]

The Dynaflite BOT doesn't have spoilers, only a rudder and elevator. And with the elevator servo mounted in the tail. I wanted to keep it as light as possible so that I didn't have to add weight to the nose. Maybe just a larger battery. :p O.L. that Futaba looks like a good choice, just under 8 grams and a little more torque that the D47. And cheaper :D , except that I already have the D47. ;)

The next question is, what size servo wire. Do we go for light here again, say 26 gauge? Or is that a problem with the length of the servo wire. Looks to be over 30" if I mount the RX in the nose.

And this all looked so simple when I started! :rolleyes: When I was a kid I didn't worry about any of this stuff. :eek:

Thanks again guys,
Vulture

[O.L. Adcock]

Vulture, The current draw is so small wire gauge isn't critical. Yes, you will have to extend it. I think we had to add about 1-2 ounces to the nose and that's very reasonable and cound be made up for with the battery. You aren't going to notice 6 ounces one way or another on a ship that big....O.L.

[Andy W]

I would use an HS-56 or D-60, or the new HS-65. The 4.7 is too small, in my opinion. Also, I would use 24 or 22ga wire, current draw is low but the length is significant, which could result in low voltage at the servo.

I use 22ga twisted wire for long runs to ailerons and tail servos. I have two 5125's (digitals) in the tail of my AVA, and also have a decoupling capacitor in the end of the boom to help smooth out the voltage. Overkill, perhaps, but the voltage at the servos is steady..
..a

[StevenatorLTFO]

I put a Futaba S3101 (35oz of torque I think) in the tail of mine, I wanted a halfway beefy servo back there.

I had to open up the hole slightly, and I gooped the servo in. Its a little thick, so I can't use the rear cover, so I just covered the access hole with clear tape.

The downside if you go this route, is that you will have to have your servo right the first time, it would be very hard to make any further adjustments.

After the first weekend of flying, I decided to add spoilers, so I cut a spoiler bay into the wing, three rib bays wide, and I am driving the spoilers with a couple of cheapie park flyer servos in the wings. I have put 12 flights on it since I added the spoilers, and it was worth the effort in my opinion, its helped me get a handle on getting the BOT much closer to the target on landing.

So far, I'm pleased with this bird, I've launched 8 times off of a 12 volt winch, and 12 times with a rather mild high start.

Steve

[StevenatorLTFO]

I might add, that with this servo in the back, I didn't have to add any nose weight at all, in fact, even with the receiver (an Electron 6) under the wing, I would be inclined to shift the CG back a touch to suit my tastes.

SS

[Stan_in_AR]

We may need to describe the word "bellcrank" I used the setup that Dave Thornburg used in his original plans. Mounted an aileron bellcrank so one leg was just below where the fin attaches to the fuse. In Dave's original plans he used a square piece of brass tubing about 1.5" long that was attached to one end of the aileron bellcrank and the brass tubing attached to the adjacent horn with a hole drilled in that end to accept the forward stab wire. With my last BoT I used a threaded rod with two metal clevises instead of the brass tubing.

Trust me, a carbon rod will go from the servo mounted under the canopy to the bellcrank with NO binding of any kind.






Vulture, I put a Futaba S3114 in my wife's BOT, works fine. Stan, The geometry in a BOT won't allow a straight push rod. I'm afraid by the time you ran a push rod to a bellcrank, then up to the flying stab, you'd wind up with the same or more weight then using the servo alone....O.L.

[O.L. Adcock]

Yep Stan, That's what I said. :) A bellcrank of some type would have to be used. The best straight line that will provide clearance falls a good 2" below the stabilizer....O.L.

[seanpcola]

I seriously bashed and modded a DF BOT that a friend destroyed on the second flight. One of the things I did was to move the elevator servo forward and ran a bellcrank (home made CF) and a CF .070 rod. In my case, compared to the servo the original owner installed out back, I was able to remove about 1.5 oz. of nose weight.