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Old Mar 05, 2013, 10:05 AM
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I'm using stock esc/fan combo which has a 30A esc- so I'm guessing it's drawing more than 25A and probably about 30A?

I'll order some decent spec 1300mah 3S, though I also have a load of Turnigy 2200mah 3S 25C and a couple Turnigy Nano-Tech 2200mah 3S 25-50C which will be suitable too, so may do the mod - but haven't seen much on flight time? Anyone know what sort of flight time I'd get?

And ty for the calculations, didn't realise that's how it was calculated


edit; Funnily enough - doesn't that make the batteries they suggest a bit weird too? They suggest 1300mah 3S 20C which is 26A draw, only 1 Amp more than mine!
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Old Mar 05, 2013, 10:32 AM
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Originally Posted by Add1ct3dd View Post
I'm using stock esc/fan combo which has a 30A esc- so I'm guessing it's drawing more than 25A and probably about 30A?

I'll order some decent spec 1300mah 3S, though I also have a load of Turnigy 2200mah 3S 25C and a couple Turnigy Nano-Tech 2200mah 3S 25-50C which will be suitable too, so may do the mod - but haven't seen much on flight time? Anyone know what sort of flight time I'd get?

And ty for the calculations, didn't realise that's how it was calculated


edit; Funnily enough - doesn't that make the batteries they suggest a bit weird too? They suggest 1300mah 3S 20C which is 26A draw, only 1 Amp more than mine!
Remember, bigger is better. Yes, they will be heavier - but all that will mean is a little faster landing speed required, and you will figure that out easy and quick.

And yes, again - their recommended batts are goofy. Nuthin new with that, they have their agendas too; their choice probably centered on where they intended batt to go, and what space was available there. Had nothing to do with what the plane realistically required.

Your guess on draw likely correct, and the batt is prob. not of the best quality, so it heats up fast. Flight time with the bigger batts will be dependent on how heavy a throttle hand you have - but you will probably get upwards of 4-1/2 to 5 minutes out of the 2200's, so long as you only use WOT for short bursts (like, 4 to 5 seconds at a time). Easiest way to find our how long you can get out of them is to set the timer for 3 minutes; go fly normally; recharge the batt and see how much charge is put back in (mAh total put back). If you put back, say, 600mAh into a 2200mAh batt after 3 minutes, then you know that you're using around 200mAh per minute. Using 80% of batt capacity as your safe limit of use, that means you can run out around 1600 to 1700 mAh of charge - or around 8 minutes total flight time. This will vary, of course, but will be good as a ruff estimate until you verify just how much power gets consumed during your normal flights.
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Old Mar 05, 2013, 11:16 AM
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Ok yep - so the idea is to go buy mAh put back in rather than voltage? I tend to fly around 3.6v (per cell), and I believe the cut off is 3.3v (give myself enough just in case I get into a sticky situation).

Also - what sort of throttle input do you give then? I was flying WOT (not sure what it stands for but know its full throttle) the whole time as there's not that much power from the model? I guess I need to figure out where I'm safe with the throttle (didn't have chance to on this first flight as I was ensuring trim was ok) to fly slow enough but not stall.
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Old Mar 05, 2013, 11:29 AM
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You have the idea...

Either voltage or mAh will work - generally easier to use mAh as that way you won't be so likely to run into dead-stick landings - tends to keep some zap in the batt for that extra go-around sometimes needed.

WOT means Wide Open Throttle - same thing you thought it did. If the motor in there doesn't have enough oomph to keep the plane airborne with less than wide-open all the time, then you really will need decent batts to keep it up there without killing the batts. Or....you could change the motor out for something with more guts. There are lots of choices here, and should be studied a little before jumping to something.
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Old Mar 05, 2013, 04:33 PM
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Either voltage or mAh will work - generally easier to use mAh as that way you won't be so likely to run into dead-stick landings - tends to keep some zap in the batt for that extra go-around sometimes needed.

WOT means Wide Open Throttle - same thing you thought it did. If the motor in there doesn't have enough oomph to keep the plane airborne with less than wide-open all the time, then you really will need decent batts to keep it up there without killing the batts. Or....you could change the motor out for something with more guts. There are lots of choices here, and should be studied a little before jumping to something.
I'm thinking because the battery was being overworked it couldn't handle the motor @ full, so if I do this 2200 battery compartment mod I solve this issue, and already have 5 or 6 batteries without having to buy any more

I'll go through the mod & see what it's like , I'll need to find some hinges though for the door!
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Old Mar 05, 2013, 04:40 PM
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I'll go through the mod & see what it's like , I'll need to find some hinges though for the door!
Magnets. That's all you need. Carefully cut the hatch out, maintaining a snug fit - then just a couple magnets will keep it in place.
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Old Mar 06, 2013, 03:02 AM
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Ok cheers, thanks for all the help I'll research over the mod today and probably cut it tomorrow (we've got some bad weather here now so no flying for a few days, plus maybe upgrading from dx6i to dx8 after some radio issues over the past couple of weeks!)
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Old Mar 13, 2013, 05:30 AM
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Hey guys, this will be my second F18, I wasn't quite ready for the first one i got a couple of years ago

I've modded one of the elevator servos so that i don't have to use that crooked reversing pushrod, as i noticed when bench testing that i wasn't getting even throws on both elevators. So i've now got two straight pushrods and a servo reversing lead, which has the throws looking identical.

I was just wondering if anyone on here remembers what flight times they were getting on the 1300mah 3S, so i can plug that in my timer! I know most of you are using 2200mah, but i'd like to stick with the 1300mah's for now.

Thanks.
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Old Mar 13, 2013, 06:17 PM
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Originally Posted by Mr Krinkle View Post
Hey guys, this will be my second F18, I wasn't quite ready for the first one i got a couple of years ago

I've modded one of the elevator servos so that i don't have to use that crooked reversing pushrod, as i noticed when bench testing that i wasn't getting even throws on both elevators. So i've now got two straight pushrods and a servo reversing lead, which has the throws looking identical.

I was just wondering if anyone on here remembers what flight times they were getting on the 1300mah 3S, so i can plug that in my timer! I know most of you are using 2200mah, but i'd like to stick with the 1300mah's for now.

Thanks.
In this situation (because i don't have a watt meter) I would run the jet for a 2 minute flight and then check the resting voltage of the battery after giving it a minute or 2 to cool off.
If you're well above 3.7volts per cell resting, you've got a bit more time, so increase to a 2:30 minute flight. Repeat and slowly increase your flight time in 30 second increments, but try not to go below 3.7v per cell (at rest). (or you may hit LVC on your ESC)

This way you don't risk compromising the battery and you still get to fly
(instead of bench testing).
Hope that helps.
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Old Mar 13, 2013, 09:10 PM
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Originally Posted by m_ark View Post
In this situation (because i don't have a watt meter) I would run the jet for a 2 minute flight and then check the resting voltage of the battery after giving it a minute or 2 to cool off.
If you're well above 3.7volts per cell resting, you've got a bit more time, so increase to a 2:30 minute flight. Repeat and slowly increase your flight time in 30 second increments, but try not to go below 3.7v per cell (at rest). (or you may hit LVC on your ESC)

This way you don't risk compromising the battery and you still get to fly
(instead of bench testing).
Hope that helps.
Cheers for that, your advice sounds good, so I'll run with that!

Weather is looking good tomorrow, so should be able to maiden her then.
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Old Mar 14, 2013, 03:06 AM
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Originally Posted by Mr Krinkle View Post
Cheers for that, your advice sounds good, so I'll run with that!

Weather is looking good tomorrow, so should be able to maiden her then.
Obviously you'll be recharging your battery between flights, or using different batteries on consecutive flights.
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Old Mar 14, 2013, 05:03 AM
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Obviously you'll be recharging your battery between flights, or using different batteries on consecutive flights.
Correct, I've got a heap of 1300's waiting to go.
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Old Mar 14, 2013, 02:32 PM
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Can anyone recommend a magnet size for this battery hatch? I'm not sure which ones to go for!

And also, I assume neodymium is probably a bit too strong?

Thanks!


edit: I'll be putting washers on one side, and the magnet on the other, so will need two, is 2x1mm too small? Need a rough guide on size + strength
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Old Mar 15, 2013, 05:34 PM
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Maiden was today... Took ages to get in the air, then trying to turn her around took ages too, end result was she got too far away and I lost orientation.

The main damage is the forward section of the fuselage is caved in, the plastic nose piece at the end is no more, as is the canopy. I will rebuild, but with 4S and maybe a bigger fan/motor. To me she was way under powered.
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Old Mar 15, 2013, 05:46 PM
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Sorry to hear that.

This F-18 was my first EDF so I still have a soft spot for it and keep up with the threads on it.
Mine was barely able to stay in the air on the stock power set-up. I quickly slapped a 4400kv wicked motor in there along with a bigger ESC and put a 2200kv in behind the cockpit.

It came alive!
Great little flyer, taught me a lot about jets.

Don't be afraid to stuff some mAh in this bird. It can carry a pretty good load. ...just go easy on the high G turns.
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