jimkron

Mine had less than a pound of lead in the nose with all the lipos in front of the canopy. I made a hatch. The ESC is in the cowl as well. I fly with the 2 160s. I often wonder if I could have gone with a small motor (110) in the rear and maybe saved on the weight in the nose.

Katniss

I saw that Kahloq made a hatch up front too. Wonder if the plane could fly on two power 90s on 8s. power 90 has higher kv then the power 110 and can spin an 18x12 just fine.

Sessholvlaru

How do you think two 110's would fly it?

jimkron

Not sure. I know it flies well with two 160s but it is heavier...35 pounds for mine. I swing two 20x10 props on a (2) 10s 5000mahs lipos. Flight time is around 7 minutes. Takeoff is brisk, airspeed is very good, landing is ...well...heavy...gotta keep the speed up...this baby doesn't float. I have Sierra brakes on mine. 110 is 17oz and the 160 is 23oz....maybe you could knock a pound or more off the AUW with a 160 on the front and a 110 on the rear. Lighter 8s on the rear motor, smaller prop on rear, less nose weight...interesting idea. The thing about electric power in big planes, you have to vary your throttle...you can't go balls to the wall to just keep the plane in the air...that will lead to a Low Voltage Cut-off quicker than you want. So (2) 110s...that might be scary. As others like to say...try it and let us know how it works out.

jim

Sessholvlaru

I am just looking for the optimal setup. I want to go same motor/prop front and rear just like the real deal but I want to keep it light. I have experience with giant scale electric (see my twin motor contra-rotating Wyvern) so at least I have some experience. It spans 88" and flies on two 8S 5,000 packs and weighs in at under 20 pounds. Lighter is better for sure, this thing flies like an Astro Hog.

Just need to figure out the particulars.

glazier808

My Feedback: (1)

Hey Sess, I'm pretty sure Ray said he had two Eflite power 110 motors in his...here is the vid, seems pretty hot!

Casey

http://youtu.be/r7RvwL6rVfE

F82FAN

My Feedback: (10)

I have no shame in telling you that I am un-abashedly jealous of your airplane, and even more so if you found the time and talent to build it yourself even if it looks like an ARF.
LOVE IT!!!!

visioneer_one

My Feedback: (506)

I saw that ad and talked to the guy. I'd have bought that plane if he hadn't thrown away the boxes!

I'm planning on building one of these also as electric. I've read this entire thread and have done a bunch of research and planning... here are my thoughts.

All the examples I've read about using the same size motors fore and aft have all ended up needing the motor batteries placed up in the nose, which involves cutting an extra hatch in the fuse. I am trying to avoid that. I'm hoping to build mine so that all the propulsion batteries can go into the big hatch over the wing.

I'm going to follow the glow example of a bigger motor in the nose than the tail.

I have spotted an example on Youtube which I'm going sort of replicate. He's got an AXI 5345/18 (900g, 171kv) on 12S turning a 21x14 2-blade prop up front, and a 5330/24 (650g, 197kv) on 10S turning a 20x15 2-blade prop in the tail. (AXI 5345 is about 300g heavier than the 5330.) All battery packs are 5000 mAh.
RTF weight is 15.5kg / 34 lbs.

Video is here.

There are three other unedited videos of this plane at the same event.

(Beware! Awful techno music.)

https://www.youtube.com/watch?v=aLuWk6nfWiQ
https://www.youtube.com/watch?v=bPRhezftgkM
https://www.youtube.com/watch?v=_ehoGDPrqnU

Observations :
- based on its ground handling, takeoff and landing attitudes the plane appears to be balanced neutrally - almost slightly tail heavy.
- seems to have a flight duration of around 6 minutes of mixed-throttle flying, with some mild aerobatics thrown in.
- standard ESM struts (& wheels?). No idea as to the retract mechanisms, but they cycle too quickly to be electric.
- cannot confirm where he has his batteries placed, but I don't see any evidence of a hatch in the nose...

I've had good luck with the 63mm Turnigy SK3 motors so I'm thinking on using a 6374-192kv up front and a 6354-215kv on the tail. These motors are comparable weight-wise to the AXI examples (840g and 485g, respectively), and are certainly affordable. Planning on running both motors off of 10S to keep the overall weight down. Potential front/rear prop combos with these motors could be a 20x13 2-blade & 18x13 2-blade or 19x12 3-blade & 18x13 2-blade.

(Regarding prop selection. Everything I've read on full-scale inline twins suggests that you balance the pitch speed at both ends for maximum thrust and run slightly more pitch in the rear for maximum speed. Planes with inline engines and fixed-pitch props (Burt Rutan's Defiant is the best example) are set up with more pitch on the rear engine... thrust balancing is managed by throttle position.)

I also plan on using the usual tricks to keep weight out of the tail. HS-225-sized servos on the rudders & elevators rather than full-sized ones. CF control rods versus steel. CF spinner & lightweight backplate instead of the scale ESM aluminum one. Light 2-blade wood prop versus heavy composite 3-blade examples. All of these are small changes, but can easily shave 10oz from the tail, which translates to not needing double (or triple!) the same amount of weight in the nose for balancing.

Finally - I'm going to stick with the ESM V3 electric retracts, struts and wheels. I had an ESM PC-71 (have since sold it) with the standard air retracts. I eventually converted these to electric with units from HobbyKing. (I had to ream out the trunnions to fit the ESM struts). The ESM retract units worked fine and were quite strong, but I was never pleased with the non-scale cycle speed or the lack of sequencing. Also irked me having to borrow an air pump each time I wanted to fly my electric airplane.

I evaluated the ESM V3 electric gear for my Pilatus. The ESM electric retracts use the same frame as do the air ones - they simply substitute the electric actuator for the air cylinder.

I'd have bought them if I could have gotten just the retract units or actuators, as I didn't need a second set of struts.

BTW your Wyvern looks awesome. Got any video of it anywhere?

it must sound... unique

Sessholvlaru

Well I also drove 3.5 hours to outside Boston to get that Do-335, so it cost me a couple bucks in gas. Wyvern video below. Was taken at a funfly a couple months ago. One of my Robart electric retracts had died so I had to fly it gear down. The plane and I are also on the 2014 NEAT Fair video...you should totally pick it up. There is an in-depth thread about this plane over at that "other" forum.

http://www.youtube.com/watch?v=ayU247BUI6o

skubacb

Hi, know this thread is old but need some info. I trying to use a 35cc in front and a 20cc gas in the rear. My rear firewall has almost a 10 degree angle pointing the engine to the right. Did ESM just mess up on my rear firewall.
I believe this is NOT correct since the rear fake propeller setup would not work correctly with this firewall.
Can anyone else tell me if their rear firewall is perpendicular to the thrust line or not?

Ameisenbar

Hi, My rear firewall was also glued in at an angle, and I don't think this is correct. I went to a bit of trouble and routed the rear firewall to be perpendicular to the fuselage. This needed an extended bit on the router, plus several people to hold things and a lot of care to make sure the router did not get away and go through the side of the fuselage. I glued an extra piece of plywood on so that I was routing that away rather than the original firewall. Another way to tackle this if you don't have a router would be to make a wedge the right shape and glue it in place. Mine was actually out of line both vertically and horizontally. I suspect someone was being careless at the factory.
Mine has a 160 twin up front and a 120 single at the back, both four stroke engines. It has not flown yet, I have been busy preparing to move house, but it only needs a bit of work on the muffler installation for the front engine and a few finishing touches.
John

skubacb

Hi,
Thanks for the reply. Just heard back from ESM. Indeed the rear firewall should not be skewed. Those four-strokes should really sound nice. I have two in my B-25 with Twin-sync. Much better sound than the two-strokes.
The router sounds like a decent way to bring the firewall to zero/zero. I will start with a wedge that will be close and go from there.
My firewall measures: Left - 2.440" Right - 2.675" measured from the right and left sides of the rear of the fuse. So I have about a 1/4 inch to repair. That is way off in that short of a distance.Although this moves the motor further from the firewall. I may have just enough room to not have the prop sticking out too far. Sounds like the factory didn't bother with angles and just pulled the firewall in without even eyeballing it.

BTW how did the CG work out with the two engines? Figure my engine weight should be about the same as yours so very interested.

Hope your first flight goes well.

bcrc

My Feedback: (19)

Last summer I finally completely finished my DO335. It flies great with the Laser 360V2 in front.
Here is a video of it on youtube:
https://youtu.be/CGqnqQbMvA4

F82FAN

My Feedback: (10)

BEAUTIFUL FLIGHT VIDEO!!!!
Good job BCRC

skubacb

Removed. (Got posted three times)

skubacb

Removed.

skubacb

Nice. Looks like the Laser pulls it around with authority.

Wood glued 1/4" thick plywood to the rear firewall. Then routed it even with the rear fuse. Right now eyeball says the engine offset is zero/zero. Plan to do some checking before saying it is so. They call for the engine to be about .280 too far to the rear. So I have some work to do to get the rear engine buried far enough into the fuse.

bcrc

My Feedback: (19)

Mine was straight (no offset either to the side or up or down)

skubacb

I built an aluminum motor mount which allowed the motor to be moved far enough back. The DLE-20 plug with boot just and I mean just fits under the vertical stab (lower). Ready to mount the motor but will make brass tube leads for adjusting the motor. Permanently mounted in the fuse they will direct a screwdriver to the needle valves. Just too dark in there to get the screw driver onto the valve without the brass tubes. Hope to fly in the next two weeks.

bcrc

My Feedback: (19)

I have to sell my Dornier, as we are moving to a retirement home and I have to downsize.
See my RCU ad for details.
About $6000 into it and a lot of labor. Selling it for $3499.
Video: https://www.youtube.com/watch?v=CGqn...ature=youtu.be
I have many photos and history of the evolution of this model - just ask.

bcrc

My Feedback: (19)

I'm not sure why my photos covered my text.
Here is the video:
https://youtu.be/CGqnqQbMvA4

I have lots of photos of this airplane from beginning to present. If you are interested, please ask.

Ram-bro

My Feedback: (101)

is this the ARF kit?

bcrc

My Feedback: (19)

Yes, it started as the ESM ARF, but to say it was "almost ready to fly" is a stretch. My ad will tell you all what I did to it. Also, I can send you a Powerpoint presentation of many photos from beginning to end. Do you want the powerpoint presentation? It is in .pdf form so anyone can look at it.

skubacb

First Flight: DLE-35R front and DLE-20RA back. Took about 5 lbs of lead in the nose to balance the bird.
Out doing taxi tests. I did my best to check that the rear engine was Zero/Zero but without any clear reference it was hard to tell. So I was doing a number of taxi tests to see if I could tell if the rear engine was doing anything wrong.
After some taxiing at high speeds I decided I would see if the plane would just lift off the ground with half-flaps.
It never did seem to get light until I hit a bump and was in the air. Had to take the chance and go full throttle. Guess I got the rear engine correct since the tail was not shoved around.
CG was exactly as the manual called for.
Once in air I tried gear up, half-flaps, full-flaps. In all cases the aircraft seemed to not be disturbed by the configuration changes. Did a quick stall test. With stock settings on the controls the aircraft just mushed. No roll off to either side. I did leave the engine at high idle so it may be different at lower engine speeds.
Lost a wheel on landing. Did not notice but unless you drill them the VQ Models aluminum wheels are slightly too thick for the nylock nut to fully capture the threads.

In flight the rear engine was unloading. I could only find two pusher props for the rear engine. So while you could break in the 20RA with the 15x8 it tends to unload in the air. My only other choice was the 16x6. With the lower pitch I am very uncertain that it would not also unload in the air. It seems that the 35R is pulling a little harder than the 20RA. So until I can find another propeller I will do some mixing in the radio to slow the rear engine.

The good side to the unintended flight is that I no longer have to sweat about the rear engine thrust line.

bcrc

My Feedback: (19)

I have reduced my price on this to $2000, as I must sell it.

See my RCU ad for more info