SanJoseDale

I'm about to start an EU-1a build on electric power. I ordered the short kit from Don at RCAIIR. I'm wondering if anyone has an e powered EU-1a yet? I'm still fairly uncertain about the motor/battery combo I will use. Looking for some advice.

Dale

doxilia

My Feedback: (3)

Dale,

Check out Doug's Conquest IV build here on the forum. Lots of e-details in it.

Scorpion ~550 Kv power was used on a 13x10 prop and 6s5000. About 1600W input power. You might want even more unless you can build to under 9 lbs.

David

SanJoseDale

David, I did actually see this plane fly at teh Lancaster contest last fall, very nice. Ithink 12 in prop is about all I can use on the EU 1a.

Dale

doxilia

My Feedback: (3)

Dale,

You might have to retract the nose gear slightly into the wing LE in order to attain sufficient power for an EU-1A. Many built to 10 lbs but I'm sure one could attain 9 or slightly better especially with covered wings and stabs.

Getting 1800W of power on a 12" prop and 6s might be a challenge. Not many motors that can handle the current draw will have Kv ratings that will efficiently deliver on a 12x11 or some such.

Have you fooled around with the motocalc programs?

Any motors jump out of the fray?

David

SanJoseDale

l did corespond with Lucien at Scorpion Morors, who is very helpful. The 4025-10 on 8s might do the trick, 550 KV, 2000W, with a 12x8 or 12x10 prop. I just don't know about weight yet. Gonna build as light as possible, with film wings/stab.

PatternPilot

My Feedback: (58)

The trick is light glass work... Is it a brick or light ? that and watch wood weight like a hawk..

s.

doxilia

My Feedback: (3)

Go 1/32 on the skins. CF underneath as you see fit.

That motor on 8s will do the trick I think but that's a lot of battery. Reverse engineer it.

David

stuntflyr

Hi Dale,

PatternPilot

My Feedback: (58)

Chris,

Has anyone done the honeycomb wing to save weight on EU-1A?

Scott

Ron Stahl

My Feedback: (12)

While many still doubt it I built several of these back in the eighties with OS .61 FIRE power that were under 9 lbs. they had 1/64 ply skins and monocoted wings and tails. I am doing a electric conversion on Strickers Excalibur which looks a lot like a bigger EU1a. I'm planing on a 10-12 cell system.

SanJoseDale

here is the data from Scprpion, their best recommendation. a 4025-10 with a 12x8 prop.

doxilia

My Feedback: (3)

Wow. Increasing the prop size by an inch only drops 250 rpm. That's rather impressive. I'm not sure that's accurate, all else being equal.

What props and batteries are being used?

It sounds like Ron has built em under 9 lbs with covered surfaces. I suspected this could be done. You might just have to keep the capacity of those 8s packs in check. The first 66A setup sounds promising allowing you to stretch the batteries a bit.

David

SanJoseDale

well, it also comes with over 20%more current. 66 vs 80 A.

doxilia

My Feedback: (3)

Dale,

Good point. 80A sounds like it might be the upper end of the motor's current capacity.

At 80A a 5000 mAh pack would give 3m45s at WOT. At 66A you'd have 4m30s which could translate into 7-8 min flights. I think that's about the current draw Doug has on a 13x8 on 6s. Same motor.

David

SanJoseDale

turbo.gst

My Feedback: (8)

I'm anxious to see how light an Eu-1a can be built. Please keep us informed.

pvogel

515kV actually, not 550. I'd think a 12x10 would actually have the prop stalling out, losing efficiency (just checked, Motocalc agrees, 12x10 would be stalled). 12x8 through 16x10 are good for this motor (I run the Osiris on 5S using the 4025-10 with a 16x10)

Peter+

doxilia

My Feedback: (3)

Dale,

Did you discuss with Lucien about 8s on that motor? Their web site says its rated for a max voltage of 6s.

If Doug can turn a 13" prop, you should have no problem doing the same on a bigger model. According to Chris and based on the glass fuse picture, there ought to be plenty of space for a longer nose strut.

I think if you want to go high voltage you might have to drop the kV some, or, use the 10 wind and go 6s.

David

SanJoseDale

With a firewall installed for an electric moror, there is probably 10 inches forward of the wing LE, more than enough. all Ineed is 7 inches to clear a 13 in prop.
Doug's Conquest flyes much more slowly, Isaw it fly at Lancaster last year, very nice but not as fast as Iwould like for an EU1.
Yes, the numbers Iposted above came from Lucien, this is his recommended motor. Isn't a -10 a 10 wind?

Dale

SanJoseDale

Not as anxious as me :!

here is the honnetcomb wing, prior to sheeting, saving 35g per panel.

doxilia

My Feedback: (3)

Dale,

The nose gear situation sounds good. I hadn't considered that your FW would of course be much further forward with e-power especially with a nose hatch.

So a high pitch 13" prop can be turned now but the speed won't increase by going 8s - the ESC and motor will just burn out. I think Lucien wants to be helpful but if you want a ballistic EU-1A, 515 kV is not the way to go. Although I haven't seen it fly like you have, I suspect Doug's model presents a classic version of a more modern constant speed model. Probably a touch faster. Personally, I feel your thinking is correct, you need to go 12x8, 12x10, or even 11" diameter and keep the RPM up and use 8s but not on that motor.

One way or another I'm sure it will fly well but this e-power equation thing always gets my head thinking...

David

pvogel

David, if I'm reading you right, you seem to be thinking that Electric motors are constant power systems like Glow/Gas (spinning faster/slower based on the load delivered by the prop) they aren't. Electric motors are constant speed, they will spin at or very near the rated RPM/V regardless of the load, they'll pull more amps to achieve that speed. Increasing volts and reducing kV is often a good way to reduce the amp draw of the system and since resistance (wasted energy) is a function of the square of the current, reducing amp draw makes your power system more efficient and LESS hot. Ex: a 3s motor at 1030kV would turn at about 11,433 rpm and might pull say, 100A to deliver 1110 watts of power. You could go to 6s at 515kV and turn the same prop at 11433 rpm but only pull 50A and your power system would have 1/4 the power losses due to heat.

So in Dale's case, the only risk of going to 8s is if you are hitting an RPM that would exceed the max RPM of the motor or continuously exceeding the power rating of the motor. The 4025-10 is rated at 2000W with a very low internal resistance. According to motocalc an 8s system with a 12x8 prop would pull very slightly over 2000W (2039 to be exact) and be well within the 100A maximum for the motor at 70A. Assuming Dale isn't flying at 100% throttle the whole time, I would not expect ESC or motor to burn out at all.

On top of that, Lucien knows his stuff! If he says the 4025-10 is OK on 8s then it'll be OK at 8s turning a shade under 14,000 RPM which sounds well within the max RPM range of most Scorpion motors of this size (though I couldn't find it for this specific motor).

Peter+

pvogel

Dale, all that said, whose prop do you intend to use? APC's rated max RPM for a 12x8E prop is 12833, you'd be exceeding that by more than 1000RPM (slightly under 10%) on your 8S setup.

Peter+

SanJoseDale

Peter, haven't really considered that yet

TonyF

My Feedback: (92)

Run a regular 12x8, not the E version.