ParkZone Piper Archer w/3S battery
So I was thinking, hmm, the 1300mAh 2S batteries have the same footprint as the 1300mAh 3S batteries from my Glasair, so I bet I can get one in there.
I still had the wrecked canopy from the ill-fated maiden flight, so I taped up the cracked top and cut a recess in the bottom of it to allow for the extra height of the 3S pack. Mr. Pilot is still there, but I think he was cutting washers out of his seat cushion.
The CG remained the same because the battery is positioned over it. The stock prop is an 8.25 x 5.5, but I went ahead and put an 8 x 6 APC prop on just for grins.
I went to the field this morning and put her in the air. Wow! The scale purists won't like it because of the speed, but this little bird can fly!
I set the timer for 6 minutes. The battery voltage was 3.7V, so I could have flown a while longer, but the wind was kicking up so I decided to pack it in for the day.
There were two downsides. First, adverse yaw really shows up in a turn. I use an aileron/rudder mix set at 100%, and that wasn't enough. I had to add rudder to keep the nose in line.
Second, it came in very hot, and it was really difficult to get it to slow down enough to land. Our field is 600' long x 200' wide, and I used every bit of it to land. I need to set the battery back a bit, and maybe try the flaps mod.
Anyways, it was an easy mod and completely reversible. Just install the stock canopy, prop, and battery and fly lazily around the field. What ever suits your mood! :D
Did you check amps with a wattmeter? If not you must because it's very likely that you will be miles over the rating of the motor and ESC and you will very likely burn up one, or both. Even if you ignore the slight propping up, just changing from a 2s to a 3s battery will increase your amps to more than double it's original value, maybe closer the three times!
Anyone reading this thread... Dont do this without first check amps. You will likely have to prop down considerably to keep the hardware within spec.
Regarding the 'coming in hot'.. Are you running out of up elevator, or does it stall if you try to slow? If you are running out of up elevator that indicates that the CG is too far forward. If it stalls when you try to fly slower then the plane is heavy there not really very much you can do about that other then put a lighter battery in.
Good tip about the wattage. The 370 BL is rated at 120 watts, 2S or 3S, but the ESC is only 10A. I'll check it out before I put another pack through!
As far as coming in hot, I'm sure that the CG is too far forward. I'll move it back once I've confirmed that the power system is adequate.
I bet your putting at about 20A through that ESC...
If the prop is an APC Slow Fly then more like 25A,
I haven't forgotten about checking the wattage. I bought a wattmeter, but I had shoulder surgery last week and I'm still very limited in arm motion. Flying, soldering, and using hand tools are all out of the picture for the next couple of weeks. Just pulling up my trousers is a real challenge!
I'll check it first thing, before I do anything else.
If your going to use a 3 cell lipo, use a Turnigy 25AMP esc, use a 7x6 apc prop, make the ailerons and rudder surfaces wider, Epoxy some more foam to the trailing edge for better control, 1/2" more should do it, or you can cut out the original ailerons make the pocket deeper and make the ailerons longer too, towards the fuselage for better control, use wider aileron formed balsa ,the rudder is small on that plane. It really needs to be 2X wider so you can do knife edges :eek: :Q thats what happens when you Hot Rod a under powered plane Design :D :D :D LOL ,Take my Advice and you will be able to fly 3d with it :eek: ;-) Ok, Just kidding on the 3D, take care, Chellie
I am loving the little Archer - stock as it can be. I have the battery as far back as it can go and it will land at almost walking speed. In fact I like to set it on the mains and keep the nose in the air.
My timer is set for 12m with stock pack and I love the long flights too. :)
Agree with above. The stock prop on 2s is right at the 10amp limit. The 8x6 APC SF draws even more current! On 3s I am surprised you have not already blown the stock ESC. I suspect you are in the 20amp range.
I have found the existing control surfaces are more than enough - with a bit of extra throw. The rudder in fact I dial back and added expo - it was so strong on the ground it was hard to be smooth.
A great little plane - flew it last night for 30 minutes!
I think I was spared the shame of a blown ESC because I just flew the one pack. If the wind had stayed calm, I would have kept going until the magic smoke came out. All of my other flights have been straight stock with a perfectly balanced prop.
As long as I'm grounded, it would be great to have a sim model of the Archer, in any flavor, to play with.
Well, after my Archer had an unfortunately close encounter with Mother Earth, the issue of power suddenly became moot.:<:
I've now put her all back together, and since the motor was trashed, I've replaced it with a Turnigy 2210A 185w motor and a 20A ESC. I have a 30A on the bench in case the wattmeter says to go big.
I have that motor on my Assassin, and it is very fast with a 7x6 APC prop.
I should be able to fly this weekend after I get it all balanced! I'll put a cam on the wing and post the video if it goes well.
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