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Apr 13, 2011, 10:06 PM
Registered User

Twin Motor - p38 version of the FL


I totaled my FL 40" WS this past weekend due to STUPID fingers on my part.

Now I'm ready to start the next build, but am pondering a twin motor with fixed landing gear version. Probably still 40" ws, as it fits into the car.

I found some flat foamie P38 plans (see attached) and overlaid the FL wing with slight modifications (see attached). I have searched for FL twins and not found much, which surprises me a bit given how the FL setup is so natural for a twin.

Are there any twin FL thread viewers out there that have thoughts on this possible build? I'm thinking of BW type motors, and low amp draw ESC, using a 2200 mah type 3s pack to drive it all.

Suggestions or input would be appreciated.

Blade...
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Apr 13, 2011, 11:16 PM
Registered User
wlrman36's Avatar
I built a 44 inch twin engine. Basically I converted my 44 inch original with single motor to twins... I used the stick mount from various hobby shops and used 5 minute epoxy to attach it to the wings.... After reading "The Twins) thread I used a v-tail mixer to set up differential throttle in conjunction with the rudder..... I did work... but was Very twitchy and I didnt have counter rotating props so it torqued on hard throttle.

On a side note... I finished my twin cargo this weekend again with differential throttle... and was a little nervous since I didn't have counter rotating props again... I guess the FL was more stream-lined than the cargo plane.. because the props rotating the same didnt make a BIT of difference.

So you can make it all pretty... but I would definitely invest in counter rotating props and I would probably pull out one of the red wires on one of the ESC to disable ONE of the BEC's
Apr 13, 2011, 11:56 PM
Registered User

Twin setups


I have never tried changing the power setup. I'm cheap and have only a DX6i which doesn't let you route throttle through another channel which I'm assuming you need to do if you want to to change the power based on rudder inputs. If I don't understand this (likely) clarify it for me.

My previous twin, an A26 (Tigercat - photo of concept not my build attached) used two 10 amp ESC's with 1 red wire pulled, and a separate BEC to power the servos.

This time around I'm thinking fixed gear, turning nose wheel/rudder (servo 1), elev, and 2 servo for ailerons so I can do flaps with the DX6i.
Apr 14, 2011, 11:50 AM
Unrepentant Carnivore
jamesdr's Avatar
I built a twin F&L also. Interesting experimant but I wouldn't do it again or recommend it. It sounded cool but the added complexity and weight had no positives other than folks saying "Huhhhhh??" It was just as fast, just as manuverable - and flew oly 1/2 as long.

Jim
Apr 14, 2011, 11:59 AM
3DHS 'native'
going4speed's Avatar
These part few replies have made me want to resurrect my funder streak project

https://www.rcgroups.com/forums/show....php?t=1201292
Apr 14, 2011, 02:28 PM
Reap the wild wind
headlessagain's Avatar
Well, there did seem to some interest in your design. Very cool looks and I'm sure if you posted some video this would help folk make their mind up about building it or at least pushing it nearer the top of the to do list. So many plans, so little time.
Head
Apr 14, 2011, 03:43 PM
Registered User
wlrman36's Avatar
Blade Crasher.... I am using a Dx6i as well.... I use a small 4 dollar Vtail mixer so I can use differential throttle...

On a different note... After 4 F&L's... I'm seriously looking at doing a Pusher config... Like a Vampire/Venom?Piranha.... Stay tuned for more.
Apr 14, 2011, 06:46 PM
Airplane and Heli Flyer
V-Man's Avatar
Quote:
Originally Posted by wlrman36
On a different note... After 4 F&L's... I'm seriously looking at doing a Pusher config... Like a Vampire/Venom?Piranha.... Stay tuned for more.
Pusher works well -- see my plane in the avatar picture. Advice:

1) Make the nose much longer and put the battery as far forward as you can, nose tip if your wires are long enough. I though mine was fine, and still I ended up putting a couple of ounces of lead in front. The motor plus the booms behind the CG need serious counter balance.

2) Be careful when you launch. The prop is behind your hand.
Apr 14, 2011, 09:19 PM
It's just a plane.
ZackJones's Avatar
FWIW I saw at least 3 F&L's at SEFF today. Two small versions and one bigger version.
Apr 15, 2011, 08:48 PM
Registered User
wlrman36's Avatar
Thanks for the Advice Vman..... I have a healing injury on right index finger where the blade on my ezblue flying wing tried to part me from my finger...Would love to see some photos of your pusher... Im really obsessing about this Vampire/Venom... and possibly even a Light Jet from the new TRON movie.
Apr 15, 2011, 09:32 PM
Airplane and Heli Flyer
V-Man's Avatar
Quote:
Originally Posted by wlrman36
Thanks for the Advice Vman..... I have a healing injury on right index finger where the blade on my ezblue flying wing tried to part me from my finger...Would love to see some photos of your pusher...
See attached. The battery is centrally located because my ESC wires weren't long enough. When I rebuild it (a launch mishap last November pulverized the fuselage, wing and tail are fine), I'll have to do something about it. I'll save at least 2 oz if I can put the battery in the nose.

Performance-wise, I have no idea whether this configuration is better. I selected it because I flew from a rocky field and didn't want to repeatedly lose props. Must have worked, because I broke only one and even then, it was in a crash, not a landing. I have a more standard tractor F&L in progress, I look forward to flying it this summer and seeing whether it handles better.

Quote:
Im really obsessing about this Vampire/Venom... and possibly even a Light Jet from the new TRON movie.
I've been trying to find pictures of the Light Jet and came up empty. There's plenty of concept art and screenshots of everything else, but no jet. Which is weird, because it's on screen for the entire final act!
Apr 16, 2011, 05:46 AM
Foam is where the heart is
brett.c's Avatar
Factory fresh and ready for battle.

Made from 6mm depron with 5mm carbon spar and 9mm wooden booms.
Turnigy L2210C 1200kv 150W, 8x6 APC. Bench tested at 160W.
15g to hit cg.

Hopefully will maiden tomorrow weather permitting.
Apr 16, 2011, 09:04 AM
Gravity-Compliant User
Zaurak3's Avatar
Looks like you have a cracker there, brett.

Good luck, and give us an update on the maiden!
Apr 16, 2011, 05:39 PM
Curiouser and curiouser
Kokopeli's Avatar
Quote:
Originally Posted by V-Man
.....The battery is centrally located because my ESC wires weren't long enough. When I rebuild it (a launch mishap last November pulverized the fuselage, wing and tail are fine), I'll have to do something about it......:
I haven't had this happen to me but from what I read about long battery wires, you need to be careful. It seems that you should keep the battery to ESC wires short and make the ESC to motor wires longer. The reasons behind it sound logical to me: fast changing currents between the battery and ESC can set up a resonance and burn out the ESC circuitry.

Walt
Apr 16, 2011, 08:51 PM
Foam is where the heart is
brett.c's Avatar
Quote:
Originally Posted by Zaurak3
Looks like you have a cracker there, brett.

Good luck, and give us an update on the maiden!
Cheers.
Took it up for 2 flight this morning and all went well.
Hand launching was very easy. Just a quick left arm up chuck and she was away.

Took a fair amount of up trim to get it fly level. Gg is bang on at 2.5 inches and glide path is nice and level so I don't think it is too nose heavy.

Rolls loops all good but haven't tried inverted yet. Behaves well at low speeds but drops a fair bit when banking. At higher speeds it banks nice and flat. Maybe it is nose heavy.

Doesn't like gusty conditions very much as it got buffeted around a lot on the second flight. I guess that's because of the large flat wing.

Landings are a snip.

Guys at the flying field were quite impressed with it so there may be a few more of them coming off the cottage production line

I reckon I'm going to have a lot of fun with this plane.


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