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Old Jul 02, 2009, 08:33 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
3,919 Posts
Build Log
ElectroFFFreak!--An electric pioneer revisited in FFF--**VIDEO & PLANS**

***UPDATE 7/6/09: Maidened! Link to VIDEO is in post #15!***

***UPDATE 7/9/09: Plans are in post #36***


Not so long ago but before there were lipos and cheap, ubiquitous brushless motors there was the ElectroStreak. Weighing in at a hefty 46oz with its 550 brushed motor and 7-cell NiCD pack it would probably be underpowered compared to what most of us are used to. But when electric options were relatively limited the ElectoStreak was the electric sport plane. The balsa kit was discontinued just after the turn of the century. It was re-introduced as an ARF sometime in 2003 which has also since been discontinued. Nowadays when electric ARF’s abound and you can e-convert pretty much any slimer on the market, I suppose the ElectroStreak just lost its niche. I, however, still love the looks–simple and sleek–perhaps even iconic. So...

Introducing ElectroFFFreak!--my version of the venerable ElectroStreak in FFF. Like its inspiration it sports a 44.5" span and 39.5" length. It features a simple, folded NACA0015-ish airfoil and Tony65x55's monoblock construction technique to make a simple box fuse like the original balsa kit. I used what pictures I could find online to TLAR a set of plans in MSPaint.

I'm shooting to stay under 23oz, around half the weight of the original. So far I'm looking at around 14oz as pictured below (without paint and battery).

Gear:
  • Scorpion 2215-1860
  • APC 7x5E
  • Turnigy Sentry 40A ESC
  • Rhino 30C 1350-2250mAh lipo
  • 1x BlueBird BMS-380MG servo (ailerons)
  • 2x HXT900 servos (rudder and elevator)

Published specs for the power system at 10.5V are: 32A/335W/40oz thrust/15,250rpm/72mph. These lipos may hold a slightly better voltage than that so I may end up having to prop down a bit.

I should be able to get the linkages on tonight. Hoping for a maiden later this weekend.

kendall
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Old Jul 02, 2009, 09:04 PM
Bernoulli+Newton=Lift
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Somewhere south of Chicago, IL
Joined Jan 2006
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Kendall, that looks really nice! Great job, sir.
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Old Jul 03, 2009, 11:16 AM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
3,919 Posts
Quote:
Originally Posted by magic612
Kendall, that looks really nice! Great job, sir.
Thanks, Magic.




Been thinking about the power system. The 2215-1860 is really a 4s propjet motor. It would still scoot like the dickens on 3s but burns plenty of power to get there. I also have a Scorpion 2215-18 laying around. That one makes some good numbers too for much less current. Especially if the plane is only going to weigh 23oz. For example, I can get a 1:1 thrust to weight ratio with a 66mph pitch speed swinging APC 8x8E at only 17A. With an APC 9x6E thrust goes to 32oz (1.4:1) at 49mph for the same power consumption.

According to the review of the ARF done here on RCG back in 2002, the ElectroStreak really needed to fly on the wing with the stock power system. Their brushless upgrade netted 32A on a 7-cell NiCD...so maybe 260W tops for the then 43oz plane. Both of my options would top that at least in terms of W/lb.

I guess I need to figure out how I want this thing to fly...er, assuming it does fly. If I reduce the drain on the battery just a bit I can fly with the 3s/1350 pack and still get flight times of 8-9 minutes. It would also put me in under 20oz AUW.

kendall
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Old Jul 03, 2009, 03:44 PM
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Very nice! If it flies half as good as it looks it should be awesome!
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Old Jul 04, 2009, 12:07 AM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Errr...having minor balancing issues now.

I figured the original was designed to fly with a nearly 8oz chunk of brushed motor up front so I made the nose of mine a couple of inches longer to compensate. I may have overdone it. With the 3s/1350 lipo all the way in the back of the battery compartment I'm still about an inch forward of where I want to be with the CG. And that's with the emmpenage servos as far aft as they could go. I do have a 1.5" Du-Bro spinner on there now so I can lose that I guess. Probably better that than add counterweight to the tail. I'll play with it a bit in the morning.

The other thing I just noticed is that I don't have the 7x5 prop I thought was hanging up in the workshop. I have a Graupner CAM SPEED 6x6 that would work but they tend to be less thrusty than the APC's. Might need to make a trip to the not-so-LHS in Providence before the maiden tomorrow.

kendall
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Old Jul 04, 2009, 01:43 AM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Okay. Removed the spinner, stuck 3/4oz of lead up its butt and got to the forward CG limit. AUW in this configuration is 21.3oz. The prototype is now maidenable...weather permitting.

kendall
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Old Jul 04, 2009, 07:55 AM
John 3:16
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It's a great looking plane kendall. Good luck on your maiden flight. I hope you'll be able to get some pictures (or video).
Daddy-O
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Old Jul 04, 2009, 07:51 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Well, no love from the weather for a maiden today. It seems Summer on the island brings only two kinds of weather--either kite-flying conditions or rain. Early mornings are sometimes good if you can deal with 100ft of visibility through the fog.

Anyway, still waiting for a chance to crash it. I soldered 6" extensions to the motor wires and brought the ESC back far enough to have a comfortably pliable CG. Glide tests in the backyard look promising (musta done a hundred of 'em just for shiggles).

I also modified my plans to put the battery compartment further aft. ElectroFreak V2 shouldn't have these issues.

kendall
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Old Jul 04, 2009, 08:04 PM
Geaux Saints
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Grafton, Il
Joined Nov 2007
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Ken

Looking good as usual.

I hope the maiden goes well.

Mike
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Old Jul 04, 2009, 09:24 PM
John 3:16
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I'm sorry you weren't able to maiden it today, but it is best to wait until the conditions are right (good call). I was just wondering if you considered shortening the nose a little bit instead of moving the battery bay back. That might have the same effect. I am looking forward to hearing how your maiden goes.
Daddy-O
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Old Jul 04, 2009, 10:45 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Quote:
Originally Posted by Daddy-O
I was just wondering if you considered shortening the nose a little bit instead of moving the battery bay back. That might have the same effect.
Actually, I re-drew the plans both ways. I like the look of the longer nose though.

Here are the rough plans I worked from and the two re-draws from today. Obviously, these are incomplete. They're not scaled correctly in this form and there are still parts missing. I know, not like anybody's going to start cutting, but just in case.

kendall
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Old Jul 06, 2009, 12:42 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Maiden!!!!!!!!

There must be lots of people wanting to fly kites today because it's as calm as I've ever seen it. Light and variable winds. Almost never happens on a clear day here.

Anyway...

The FFFreak FFFlies!!!!!!

Took her out to the polo fields for a good romp. And romp she did, Baby. I think I may even have heard a Barbaric Yawp or two. Hand launched at half throttle and she got on step quick and smooth. A few mistakes high I only needed a few clicks down elevator and one of left aileron to get straight and level flight. She's remarkable neutral--nice, reasonably axial rolls, loops as big as you want 'em. As you would expect with the symmetrical foil, inverted flight was easy with just the slightest breath of up elevator. I think I only used the rudder for a couple of hammerheads. Otherwise it's not needed.

The Scorpion 2215-1860 and Graupner 6x6 CAM Speed prop is a good combo, friggin' fast, but still decent thrust. Using my stock Stryker as a benchmark, WOT passes were pushing 70mph. I set the countdown timer on the DX7 for 5 minutes since the 3s/1350's are just a bit smallish on this setup. That brought me back with 11.2 resting volts left. The one I charged at the field took back 915mAh. I had some issues with the ESC timing. I think I started on low and would lose it before I got to WOT. On high timing WOT was good but there was a little bauble around 80%. I'll have to play with it some more. I brought the Scorpion 2215-18 and APC 9x6E with me but I was having too much fun to switch 'em out. I'd still like to try it though.

I suppose it's not a mystery why it flies so well. After all it is completely stolen, er...adapted from a proven design. I guess it's time to paint!

I'm editing video now. I'll get something posted up later this evening.



kendall
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Old Jul 06, 2009, 12:54 PM
3DHS 'native'
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USA, TX, Spring
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Man this thing is awesome!! Kinda reminds me of the scratch but in foam.

Any plans for PDF tile plans?
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Old Jul 06, 2009, 02:36 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Quote:
Originally Posted by going4speed
Any plans for PDF tile plans?
Sure. I gotta make 'em a little prettier first.

kendall
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Old Jul 06, 2009, 03:03 PM
Postcards From The Purple Edge
tuppertn's Avatar
United States, OK, Sand Springs
Joined May 2007
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Video!

Just posted the MAIDEN SESSION VIDEO in the Electric Airplane Video Section.

Enjoy.

kendall
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