Fili

Mine flew great with tower hobbies .40s for years. I still have her, stripped and ready for a recover and update (engines, retracts...) Anyhoo she was my first twin, and the first few flights I was scared to death. She soon set me at ease as she flew nicely and really had no bad tendencies... nice and slow landings, looked great at speed. All this was good and bad, as the twin "bug" bit me and now I have many twins. Don't know enough about electrics to help, just thought I'd advise mine landed nicely... (I'll dig for a pic)

ramp4ge

I kind of figured with the age of the plane and the way radios and engines were back in the 1970s, she'd have a certain amount of inherent..niceness...built into her to actually make her flyable on those old systems.

Especially glad to hear about the "slow landings" part.

Do you have any input on CG or control throws? I measured the CG off of the plan and it looks like it's 4 1/8 inches, or 105mm from the leading edge. So that's where I'm going to start.

Target weight is just shy of 9 pounds.

ramp4ge

She's ready to fly. Gonna do some decal work this evening and tomorrow evening but she's good to go.

A bit nose heavy at 105mm but I'm alright with that.

She came in heavy, though, at 10.44 pounds.

geothekoz

The plane looks great, the silver covering add a different dimension to the plane , but the props take away form the scale look of the plane, 3 blades would look the part. Can you shoot some video I would love to see it fly.

ramp4ge

There are no 3 blade props that would have given me the pitch I would've needed with the small size required due to the clearance of the nacelles AND given the pitch speed necessary on 4S.

After I fly her, if I feel I can stand to lose some performance to 3 bladed props, I'll definitely go that route. But we'll have to see. Right now, 510 watts @ 32 amps is sweet. I'll take it.

geothekoz

Here's where I need help. How do you determine the watt output and measure the amp draw? Can you take a picture of how you mounted your batteries and esc's. And given the size and pitch of your prop's how does she perform and how long a flight time do you get.

ramp4ge

I got my current draw from a watt meter. They really are a necessity. You can determine your watt production by multiplying your current by your voltage.

So say you're using a 4S pack at 16 volts. You're pulling 30 amps. That's 480 watts of power production. For warbirds (or other fast-flying scale planes that aren't EDF jets) you generally want to produce 100-110+ watts per pound to have a good-flying plane. That's just a rule of thumb but it works out well.

I've got my batteries and ESCs in the nacelles, 1 battery and 1 ESC per nacelle, so the power systems are independent on both motors. I utilized the fuel tank access hatches as battery hatches and replaced the bolt-down with a magnet for easy access. The nacelles are big enough to take the 4,000MAh 20C packs I'm using and the rather bulky HobbyKing 60-amp ESCs.



Sorry for the dark pictures. My phone's flash wasn't cooperating.

With the batteries in the nacelles she's a bit nose-heavy at the plan-indicated 105mm CG. I like to maiden the plane a bit nose-heavy. There's plenty of room in teh nacelle to slide the battery back. I have it all the way against the firewall (which I padded with a bit of foam).

For battery runtime I used the quick and dirty battery runtime calculator.

http://www.rtideas.com/battcalc/

I know that I'm pulling 32 amps on a 4,000MAh battery, That should in theory give me 7.5 minutes of full throttle. But it'll probably be more like 5 minutes if I don't want to implode the battery. ANd that's at full throttle. I shouldn't need full throttle for the whole flight.

Of course, the best way to check is to fly it and then check battery voltage when you land. I'm going to set my timer for 5 minutes, land and see what's left in the packs. Then I'll know for sure.

I'm hoping to maiden her tomorrow. I'll let you know how she performs!

geothekoz

Hi; Thanks for the info, and the pic's. I find it quite helpful.
So at 100 watts per pound, a 10 lb. aircraft would need 1000 watts of power...roughly, I think that's about 1.3hp. You said you were getting 510 watts at 32 amps, I take it that's per motor, so that would give you more than enough power....sweet.
My concern is weight, if your over 10lb. with a basic installation I might be looking at a lot more with retracts and gear doors installed.

ramp4ge

You can take some precautions during your build to lighten her up. Drilling lightening holes helps quite a lot as there's really no reason for her to be built as heavily when you're flying electric. There's no vibrating engines so the structure doesn't need to be as heavy. On the previous page there are some photos of lightening holes. I'm sure those made it significantly lighter.

I also used some weight where it wasn't necessary in the Great Planes motor mounts. They're really not needed, I just liked the way they looked.

I'd also recommend, while you're still building her, to set her up for individual aileron servos, if you haven't already. I'm going to have to battle the flexi-rods because one of the ailerons isn't centering correctly. I'm already thinking about just installing individual aileron servos.

ramp4ge

I got her maidened today. I was worried that at 10.44 pounds she might be a bit overweight but she flew really well. I kept her flying fast just in case, I'll try slowing her down more next time. One of the ailerons is sticking and not centering correctly so it made things a little bit dicey but otherwise she flew really well. Going to try higher torque servos and see if that resolves the issue, if not I'm going to have to do a servo for each aileron.

The power system was more than enough power. In fact, one of the guys at the field said something to the extent of "God damn that's got some power". And she does. She really, really hauls the mail.

Hoping to get a video in the next couple days. Will link here when I get one. 3 different guys filmed it, just need to get the videos.

geothekoz

Thanks for the info. I have already started to drill out the ribs and will be using independent servos for the aileron and flap controls.... the extra weight will be worth it. Is there a chart that tells you how much power is required in a servo, relative to the area it's trying to control, and the forces working against it ? I.e. an aileron of 10 sq.in. in an airplane that can travel at 80 mph. how much torque would you need in the servo to control the aileron.
Congrats on the maiden.....I like the part about the extra power.

geothekoz

I've been following a great scratch build on RC Groups by Geoff.Sim https://www.rcgroups.com/forums/thum...one&starter=no unfortunately he never posts the completed model or of it flying. To bad for such a nice build.

ramp4ge

https://www.youtube.com/watch?v=OczglXZnBSs&feature=youtu.be