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Old May 31, 2002, 04:11 PM
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mario alvarez's Avatar
San Salvador, El Salvador
Joined May 2001
605 Posts
average flight times for an EDF jet

EDF's look interesting. Just curious before I indulge in another fantasy... What are the average flight times of a MF480, 10 x 1700 battery pack equipped jet on a brushless motor? a cobalt? What are their climbs like?

Thanks.
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Old May 31, 2002, 08:49 PM
H301 Libelle Pilot
Dr. Jet's Avatar
Oceanside, California
Joined Sep 2000
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If your motor draws around 35 amps, plan on about 3 minutes of full-throttle flying. Add another minute if you use the throttle. My little A-4 (14 CP1300 and a 1114/4Y) will climb nearly vertically at high speed off the launch. I really don't know how high it will clinb because my eyes give out before the plane does!

I've been saying this for years: Don't bother with a brushed motor in an EDF. It will only wind up costing you more in the long run. You will spend time and money on maintaining the comm and brushes, then you will finally go brushless because the performance was disappointing. Might as well do it right the first time. Jets should JET, if you know what I mean.
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Old Jun 01, 2002, 08:29 AM
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mario alvarez's Avatar
San Salvador, El Salvador
Joined May 2001
605 Posts
Thanks Dr. Jet. Brushless it will be.

For a first EDF, would a delta wing such as an A-4 be better than say a conventional airframe such as a Mig15? I don't want to purchase a "disposable" foamie either.
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Old Jun 01, 2002, 08:41 AM
H301 Libelle Pilot
Dr. Jet's Avatar
Oceanside, California
Joined Sep 2000
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Take a look at the Kevin Cox designed F-18. Great flying airplanes with no bad habits. Kits are available from the Electric Jet Factory, a slightly larger (and a lighter wingloading) version is available as an ARF from EAM. The RBC kits require a lot of building expertise, but result in a great looking and flying model. The F4D is one of my favorites.

As for the delta/swept wing choice, it depends on your preference and experience.
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Old Jun 01, 2002, 06:18 PM
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Bob P's Avatar
Wiltshire England
Joined Feb 2001
919 Posts
Jets with a conventional layout like the Mig 15 F-86 etc are hard to decelerate for landing and have a high landing speed, unless you fit flaps. Flaps are complex and add weight.

The F-18 is designed for low speed at high AOA. The layout of the fuselage, twin fins, LEXS etc allow you to slow easily and fly on finals in a nose-up attitude which is both safe and slow.

The KC F-18 kitted by EJF is a superb design which is straightforward and easy to build. Allthough it is very fast, for the reasons above it is a pussy cat to land.

Bob
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Last edited by Bob P; Jun 01, 2002 at 06:22 PM.
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Old Jun 01, 2002, 07:47 PM
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mario alvarez's Avatar
San Salvador, El Salvador
Joined May 2001
605 Posts
The reason I asked is that delta wings, like on an A-4, tend not to stall out while slowing down for a landing and that would be a very desirable trait on an EDF jet. You can fly it fast then slow it down for a landing.

If a swept wing needs flaps to increase its lift at slower speeds, could a flaperons mix be used instead of adding extra servos for the flap actuation?

What is the "general" wing loading on an EDF?

I'm really an "old timer", while the F-18 model might be a great design, new jets just don't do it for me. Love the early English jets (Hunter, Vampire) and the VietNam era jets (specially the
F-4's and the A-4's), but you never know, I'll look into Aeromaster's web site and see what they have for the F-18's.
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Old Jun 02, 2002, 12:13 PM
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Bob P's Avatar
Wiltshire England
Joined Feb 2001
919 Posts
I've got an RBC kits A-4. This takes the same MF 480 fan as the KC F-18. The aircraft exhibits the delta wing characteristics that you mentioned, but it is not quite as easy to fly slowly as the F-18. Great kit, but a bit more of a builders model than the KC F-18.

Bob
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Old Jun 02, 2002, 12:42 PM
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Haldor's Avatar
Stavanger, Norway
Joined Feb 2000
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BoB - thats a very smart looking Scooter you got there
Pleased with it?
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Old Jun 02, 2002, 02:10 PM
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mario alvarez's Avatar
San Salvador, El Salvador
Joined May 2001
605 Posts
Beautiful!!

Check out these Scooters.

www.kitparade.com/features01/a4mig17da_1.htm
http://www.kitparade.com/features01/...essordwa_2.htm
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Old Jun 02, 2002, 06:18 PM
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Bob P's Avatar
Wiltshire England
Joined Feb 2001
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Haldor - yes I am.

I reckon the intake and duct are pretty efficient and the exhaust is short, giving really good performance. I modded mine with a removable cockpit section for battery access to save removing the wing each time. The hump hides the elevator servo which drives via a snake. A bit cleaner and more scalish than the original design. The ailerons are very efficient and the roll is axial.

Weren't you building one for a friend? Make sure you let him allow you lots of test flights before you let him have the Tx.

Bob
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Old Jun 02, 2002, 06:28 PM
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Bob P's Avatar
Wiltshire England
Joined Feb 2001
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Mario

Just checked out those aggressor finishes. Fantastic. Really different. Go for it.

Bob
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Old Jun 02, 2002, 08:36 PM
Acme Powered!
Joe Elston's Avatar
Orange,CA
Joined Jul 2000
4,040 Posts
RBC A4

Hi Bob, that is one good looking A4 you have there. Can I ask what you powered it with, motor and cell type and how many? I have an RBC A4 kit to that I have yet to start and I am curious what you used. I am still not sure for mine but I am thinking of a Kontroniks 480-33 on 10-12 CP 1700's
Thanks Joe
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Old Jun 03, 2002, 06:14 AM
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Bob P's Avatar
Wiltshire England
Joined Feb 2001
919 Posts
Hi Joe

The motor is a Plettenberg 200-25-4 on 10xCP1700s. It flies just fine but the fuselage is big and therefore draggy, so a bit more power would be nice. Your 480 would be good, on more than 10 cells.

You'l love it!

Bob
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Old Jun 03, 2002, 12:05 PM
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mario alvarez's Avatar
San Salvador, El Salvador
Joined May 2001
605 Posts
Bob

On your A-4, you have the avionics hump which houses your elevator servo. On the stock kit, where does the elevator servo go? Or is it an elevon mix controlled a/c?

I'm a builder, so I'm pretty much sold on the A-4. Icare has recommended a MF480 / Hacker B40-14S / ESC Hacker Master 70-3P / 10 x cells? Any comments before I say " charge my Visa card number ..."
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Old Jun 03, 2002, 12:27 PM
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Bob P's Avatar
Wiltshire England
Joined Feb 2001
919 Posts
Mario

The elevator servo in the kit version fits in the fin above the tailplane with a pushrod to a top mounted horn, which I thought was unsightly. I fitted a bottom horn coupled by a wire rod in plastic tube through the dorsal fin to the servo in the hump. Looks and works just fine.

The kit also has the aileron horns on top of the wing with top mounted pushrods. This was done to protect the horns from damage if bottom mounted. I took a risk and mounted the horns underneath with a plastic rod in tube pushrod to a single centrally mounted servo. This is the same system Balsacraft scale models use. I have three of those and have flown at least a hundred flights and have only broken one horn. A risk I thought worth taking. 25 flights later no breakages.

Fraid I can't comment on the specific motor. Perhaps Haldor or another expert will chip in. You are looking for something that will take 370 to 400 plus watts of power at say 34 Amps on at least 10 CP1700 cells

Bob
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