Sport The Behemoth Yak gets a Behemoth Brother/129" Pilot Yak (2)

Hey Rob,

Don't feel bad about being too pooped to do anything. You are not alone. . . .

I plan to try out that fuel tubing trick for the tail wheel steering at some point. I got lucky on my PAU Sukhoi and got the springs setup perfect on my first try but whenever they give up the ghost it will be converted to the fuel tubing trick.

BalsaDust said:

I plan to try out that fuel tubing trick for the tail wheel steering at some point. I got lucky on my PAU Sukhoi and got the springs setup perfect on my first try but whenever they give up the ghost it will be converted to the fuel tubing trick.

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I was never so lucky. No matter what I did, the springs took a flyin' leap and 86'd themselves. I gave up. Lol

Rob, those Fromeco cells have a rated 2C continuous discharge rate. That means that the 5200's are rated at a massive........

10.4 amps continuous discharge. Times 2 and you're at 20.8 amps continuous current capability from those LiIons. LiIon and LiPo have similar discharge rates so if you compare a 5200 LiPo with a 2C discharge rate then both the LiPo and LiIon cells will show an identical discharge rate at a given load. This is the main reason I switched to higher C rated LiPo cells, the Pulse 2s 5000 rx packs are rated at 15C which is 75 amps continuous per pack- 150 amps total with 2 packs. The way I fly I could immediately notice a difference in performance when I switched from the Fromeco LiIons to the Pulse LiPo's.

The biggest difference is LiIons don't have high discharge capabilities like LiPo's do. The Fromeco packs work for a lot of people so there's no reason to really get rid of them, the way you fly I doubt you're pushing those monster servos near their capabilities so why change your setup? It wouldn't make sense.

Xpress said:

Rob, those Fromeco cells have a rated 2C continuous discharge rate. That means that the 5200's are rated at a massive........

10.4 amps continuous discharge. Times 2 and you're at 20.8 amps continuous current capability from those LiIons. LiIon and LiPo have similar discharge rates so if you compare a 5200 LiPo with a 2C discharge rate then both the LiPo and LiIon cells will show an identical discharge rate at a given load. This is the main reason I switched to higher C rated LiPo cells, the Pulse 2s 5000 rx packs are rated at 15C which is 75 amps continuous per pack- 150 amps total with 2 packs. The way I fly I could immediately notice a difference in performance when I switched from the Fromeco LiIons to the Pulse LiPo's.

The biggest difference is LiIons don't have high discharge capabilities like LiPo's do. The Fromeco packs work for a lot of people so there's no reason to really get rid of them, the way you fly I doubt you're pushing those monster servos near their capabilities so why change your setup? It wouldn't make sense.

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All very good information. But a couple of things here. First, I highly doubt anyone is going to risk hammering 75-150 amps through a Futaba/JR connector. Not to mention the servo leads from the servos. They just can not take it. The quandary was, Are the Fromeco LiIons powerful enough to drive a HV setup with numerous servos? Absolutely is the answer. Been doing it for years. The second thing is this... On most of my flying I do, I reckon I don't strain my systems, batteries or servos as hard as some. But there are times that I really give those planes a work out. Full power aileron roll dives into a full down (52 degrees) elevator blender, time and again. Full (WOT) powered knife edge snaps from one wing tip on top to the opposite wing tip on top and back again. The Behemoth Yak does awesome rolling harriers and rolling harrier circles. Those two 7990's are slammed back and forth and back and forth and back and forth. Hmm, I have an onboard video of my Sukhoi in a constant rolling harrier. Sometimes I wonder (putting the strain on the servos to the side,) how my Pilot Edges have stayed together. Those darn 54's (HS 7954) are just about one of the best servos I have ever purchased. Anyway, Yes you are correct Tanner on the power differences of Lipo vs. LiIon. But as you said, if a LiIon is performing well with no problems, why change it out right? The real kicker for me is this. Though I have not had not one issue with a Lipo in any plane I have had...The new Jtec Pitts included, I still get a little sketch when charging them. But I charge them exactly like my LiIons.

I'm that way with LiPo's at times too. When I built my fuel jug, I needed around 11 volts to run the pump. I had a brand new in the box 3s LiPo that would have been perfect, but I just couldn't strap that on a fuel jug. I bought a 8 cell nimh instead.

All that I have to say to this subject is that the system will pull the amount of amps it requires not the size of battery. And the connectors being used are useless and good for 5 amps if you lucky.
Just a note I was lucky enough to be at JoeNall early enough to come across Jase the Ace while he and his dad was assembling his aircraft and you must admit that nobody and mean nobody flyers harder than him and he flies with 2 1300 mAh battery packs in his plane.

Snoopy1 said:

All that I have to say to this subject is that the system will pull the amount of amps it requires not the size of battery. And the connectors being used are useless and good for 5 amps if you lucky.
Just a note I was lucky enough to be at JoeNall early enough to come across Jase the Ace while he and his dad was assembling his aircraft and you must admit that nobody and mean nobody flyers harder than him and he flies with 2 1300 mAh battery packs in his plane.

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I do wonder how many flights he gets before a swap out or recharge. If I can go to a smaller battery and still insure the safety of my planes and bystanders, I would be so in!

stangflyer said:

All very good information. But a couple of things here. First, I highly doubt anyone is going to risk hammering 75-150 amps through a Futaba/JR connector. Not to mention the servo leads from the servos.

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You just hit on the most important part of your pondering. Most ION packs only have a feed line to the plane of those little 20g wires, and then if you use a non power safe switch you are choking it again. It does not take a lot to get huge AMP spikes in your system and if you feed the system with tiny wires the batteries simply can't feed the need. LiPo's will give a more consistent feed to the system through typically larger wires.

If your system is pulling 75-150 amps your individual servos are pulling much less so the connectors are not stressed like your feed wires.

stangflyer said:

Yes, I do know the two chemistries discharge in completely different ways. If memory serves correctly, a Lipo will hold...hold....hold, then drop off suddenly.

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You're thinking of A123's / LiFe. LiPo operate just like Ion but with higher discharge rates.

For your question on how many flights, my PAU Edge is similar size with 126" span. I fly with an AR12120 power safe RX, dual Pulse 5000mah packs (no ignition battery), dual MKS777's on each aileron, one MKS380 on each elevator and dual MKS380's on the larger (modified) rudder. 5 flights brings the batteries down to about 45% remaining capacity, 40% is the must charge capacity remaining to keep the LiPo's happy and safe.