simple

My Feedback: (9)

Signing up for the club - Ziroli w/DA50's x 2

Reading this thread started me thinking about 3 bladed props.
Who has the best scale looking flying option for DA's?
Anyone with experience?

panhandler

Thank you ragtop. 1 on the way now I will have a fully modified 38 and a totally stock one.;}

70 ragtop

My Feedback: (24)

Welcome to the brotherhood Simple

Couple nice looking planes you have there. I think there are a couple that flew P-38s with three bladed DA-50s. I thought the 20x12x3 Mejzlik, or a 20x10x3 was a good fit for that engine, but I have not personally run that setup, so I can't say. I think Greg Wright did on a Yellow-38, and don't recall who else off hand.

Hopefully they will chime in with some suggestions

70 ragtop

My Feedback: (24)

Panhandler
Glad to hear it. It's a very enjoyable plane to fly. I am going to repower mine with a pair on Tacon 160s so it will spin the APC 15.75x13x3 props, and still stay within limits. Switching from 6S to 10S, can go from 120 ESCs down to 80s, and going to try 4000 packs to lighten it up (although it really doesn't need it) It is sport scale after all, might as well have some fun with it

P38J

My Feedback: (14)

I flew mine with zinger 19x12 three bladed props with the tips modified to look or scale. The TBM adjustable pitch propeller might also be a good choice.

langerl

My Feedback: (5)

Simple,
See post #6 and #167. Zipz had twin G45s or DLE50s and he flew with 3 blades. Scale but not overpowered. Post #167 is my, unflown P38J with twin DA85s (got the idea from GPete's P38M). After a LOT of questions, I've decided to go to counter rotating DA85s. Supposed to be much safer and more controllable at low speeds. I've just received matched, counter rotating, twin Xoar 3-blade 24x10 props. Now I've got to source the couter rotating DA85 to replace the existing standard DA85. If you look up GPete's P38M on Youtube et al, you'll see his model flew GREAT! In fact, idle thrust ended up giving the model quite a brisk landing speed. I forget whether Pete had fowler flaps, but my Robart doesn't.
Hope this helps.

simple

My Feedback: (9)

Thanks P38J & Langerl,

P38J - I have seen your excellent work and I don't have the skill to round the tips and balance the blades like you did.

G-Pete and I met at WOR several years ago and we both agreed then that once you step up to twin "DA" you step into torque. I first flew mine on G-38's with no ground issue, but after I upgraded to 50's it pulls hard left on the ground and I am sure the 85's will be worse unless counter rotating.

I'm not ready to try a reversed engine yet, but I am ready for 3 blades. I will look into the Xores. I was thinking about Biela and TBM had the best price but they are out of stock.[TABLE="width: 100%"]
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[TD="class: style12, colspan: 2, align: left"]Biela 3B 20x10 - http://www.troybuiltmodels.com/categ...ropellers.html

http://www.aircraftinternational.com...rbonProps.aspx was listing a different design with Pushers.[/TD]
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[TD="class: style5, colspan: 2, align: left"][/TD]
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One of the guys was flying the Biela 3B prop last weekend on a single engine plane and he said its a whole new landing experience which I witnessed several bounces. Biela seem to be the most scale option ready to fly I have found, but I cant find any body listing twin experience with them.

There are a pair of 3B 20x12 Mejlic's w/spinners for sale now but I don't think they are the right combination for 50's, I'm concerned the 12 pitch is too much.

70 ragtop

My Feedback: (24)

I've been doing a bit of body work on the Yellow P-38, and wanted to confirm panel line locations. Ran across this site http://legendsintheirowntime.com/P38..._1920x1200.png.

Make sure to check out all the links. Lots of good information

70 ragtop

My Feedback: (24)

Swordsn, tuchadwick

Wondering if you could post some detail pictures of the Dyna-skin on your Yellow model. I tried out the sample pack, and was impressed how it looked (after it was scuffed up), and how light it was. Basically, I'm wondering if you need to add panel lines with chart tape and primer prior to applying the covering, or if you can get good panel lines with just the Dyna skin? Also, how hard was it to work one large piece around the gun doors, and how did you get it to cover the nose with no wrinkles?

Has anyone done flight metal on a Yellow P-38? Curious how much weight it added, did you need to add panel lines beforehand? Any pictures?

Thanks

SWORDSN

My Feedback: (13)

I wish That I could but the deal fell through and I didn't get It. It was a great deal...... He said The crate fell off a truck in preparation for shipment,there was serious damage..... hmmmm. Now I'm reading that the Yellow P38 Is diccontinued....bummer!

P38J

My Feedback: (14)

Dave if you would like to try the zinger 3 blade setups I have three sets of replacement blades and to hubs drilled for a DA50 that I'm not going to use. one tractor and two pushers. the only thing needed to reverse a DA is a new ignition pickup. let me know if you want them.

F106A

My Feedback: (2)

There's a member of my club, Buc-Le Aerosportsmen, that has a Flite metal Ziroli P-38 that he brought to our Warbirds meet..
I talked to him about it but he didn't say anything about how much extra, if anything, it added.
When Nick first mentioned he was designing a P-38, I bugged him to get the plans started and finished. To shut me up he sent his rough plans so I could get started.
I cut most of the formers, bought the original tail booms, they had a yellow tint and had the radiators molded in, along with the canopy, etc.
Things change and never started the model.

When I saw our members P-38, I got the bug again but deaded the build, I'm tired of building, been doing it for a LONG time. Then I found out that Charlie Kellogg's P-38 was for sale and bought it.
He did a great job and looking forward to flying it.

Jon

sudstad

I'm still trying to understand all of the factors in sizing/matching large scale electric components. This question is regarding C ratings.

(So far) I'm planning to run eFlite 90's in my Lightning. They're rated at 50a continuous and 65a burst. If I go with 6s 5000mah 35C batteries, they should be able to provide 175amps (over double the 90's burst amperage)... correct? If so, shouldn't they be able to support the 90's without even getting warm?

Am I thinking correctly?

70 ragtop

My Feedback: (24)

Swordsn, Sorry to hear, I feel sure another one will come along. I can't imagine it got too damaged failing off a truck. We've all seen/had "landings" that hit that hard. Maybe you can work something out?

F106A, thanks for the info, couple beautiful looking planes you have there. I like the stab mod, I assume that's for ease of transport? Does your friend normally transport it in six pieces? (LH wing, RH wing, center wing, LH boom, RH boom, and stab)Welcome to the brotherhood

sudstad, you're thinking correctly, you should have no issues with those batteries

sudstad

Thank you!
Sig

70 ragtop

My Feedback: (24)

As much fun as I was having with the NP-38, I got bored and repowered it.
I really like the way the plane flew with APC 15.75x13x3 props, but they were a little too much for the Scorpion 4025-12s. Since I was already carrying a bunch of batteries for weight, and had the motors, I installed a pair of Tacon 160s running on pair of 5300 mah 10S packs. As the 160's are heavier than the Scorpions, and use less amps, intent was to use CC 80 amp ESCs (smaller and lighter), and move batteries around, putting the larger battery over the wing, and the smaller battery up front to help counter balance the heavier motors.

Did a quick run, and the Tacons pulled 72 Amps, 2600+ watts with batteries in storage state, at around 7300RPM, so decided to leave the 120s installed until we get some flight data. Those props pull very hard, so I'm looking fwd to seeing how the plane fly's.

sudstad

Wow! So... when do we get to see video of this beast in flight?

70 ragtop

My Feedback: (24)

Ask and you shall receive.
Sorry about video quality, I need to get a camera, and figure out how to upload higher resolution files. Videos are pretty clear on my computer, but once uploaded, they get very fuzzy
First video is of the third flight after repower. Plane wasn't 100% as I had a questionable battery in it. You can hear it as it just starts the 1st downwind leg. Seemed to settle down, but not a spirited as first two flights. Problems with the Robarts.....again. Second video is of the first flight, and is really just for audio. It had that P-51 whistling sound during a couple passes around the one minute mark. I think it due to lack of gear doors as you hear it more when the bottom of the plane is towards you, but it sounds pretty cool. Plane is very maneuverable, I'm just a little apprehensive yanking and banking any harder. There's a lot of quality (China) wood and glue joints inside!

Planes are back in stock at General hobby, fun plane for not a lot of dough
https://www.youtube.com/watch?v=KMMEX_S2x1M https://www.youtube.com/watch?v=uziQzTDsiA8

sudstad

WOW! That's a testament to your building and flying skills... and to the strength of that airframe!

70 ragtop

My Feedback: (24)

Thanks

The time it was flying in a scale manner around the 2 minute mark, it was spinning the APC 15.75x13x3 props between 5400 and 5900 RPM, and never pulled more than a 1000 watts. I really like those props, obviously I'm spinning them too fast for scale. But, if you shoot for a no load RPM (Motor's KV rating times volts you plan to run) of around 6500-6800, you've got a great prop option for scale flight, while using very little power. That means longer flight time with less batteries. 5 minute flight used 2.78ah from batteries

Chris Nicastro

My Feedback: (3)

Let me help explain C Rate for LiPos.

The C Rate is the battery packs ability to discharge at full capacity or in other words under max load. The voltage under load is the measure of how efficient the chemistry is working. Your looking for the highest voltage possible under high loads when setting up high power systems. The higher the C Rate the higher the discharge Amp capability and the higher the voltage under load.
Typically for sport and scale planes you dont need high C Rates so dont invest a lot of money on the newest battery packs when a lower C rate will be less money and serve your purposes just fine.

The C Rate is used in the following manner to predict the capability of the battery pack; C Rate X Capacity / 1000 = Max Discharge Amps

For example: 50C X 5000mah / 1000 = 250A Max Discharge Rate

Burst Rate means an instantanious 1-5 second maximum discharge rate. So when you see 50C Continuous and 65C Burst you can easily calculate that with the same formula if its not alrady stated.

Charging a LiPo;

Capacity / 1000 = Max Charging Amps. For example 5000ma / 1000 = 5A Charge Rate

How is voltage tied into the set up and why the emphasis on voltage under load?

It matters because the motor is rated by KV which means revolutions per volt. So if your really critical of high performance then your really looking at the actual RPM of the motor under max load and every volt the battery can deliver is important. For example in RC car racing if a car is on carpet with foam tires this is a very high grip condition and the ESC can see loads well over 110A instantaneously. I have data logged this kind of info myself. The peak lasts only a fraction of a second but the ESC, Battery and Motor must be capable of taking this punishment as a system, the three work as one.
In a helicopter the cyclic will load and unload the motor thru pitch changes. This is very abusive on battery packs and they build up a lot of heat with punishing cycles while in 3D flight. If the battery has a low C rate then the motor has to work harder and so will the ESC. The head speed will bog under load and a few less RPM under max load in an extreme manuever can make the difference.

Back to planes. The 3D environment is similar to helis for batteries because of repeated throttle adjustments and high loads. Even worse are EDF applications because typically these are run at higher power settings to fly and the loads are quite high plus sustained for long periods. Pilots need to manage the heat and stress on packs by flying a higher energy routine, climbing and diving, to let the packs rest.

As you can see scale models and sport planes dont really need high C Rate packs for typical applications and sport flying. If your over powering a plane for speed then you will probably end up choosing high C Rate packs. Save your money and just set up a well balanced system with the right combination of components to give your plane good performance and flight duration. Buy higher capacity packs in order to compensate for lower C Rates.

For example;

30C pack and 5000mah = 150A
50C pack and 3000mah = 150A

When you can fit a slightly larger 30C pack in your plane you will increase the flight time and pay less for the battery pack. The difference is if you need higher performance then the lighter 50C pack has the advantage but its more expensive and wont last as long.

Using this example above I set up a racing boat with a team driver we sponsored and it set a world record. He used the highest C Rate we had and smallest capacity battery pack which translated into very high energy density and light weight for a short run.

Chris Nicastro

My Feedback: (3)

Yes in theory but changing the prop, pitch/dia and 2 or 3 blades, will effect the outcome. The battery pack your using will have ample head room for that motor. What ESC are you using?
The ESC should have 10-20% more capacity than the motor to give it a margin of safety. A mistake/test in prop choice can fry an ESC rated too closely to the motor max amp rating. Usually the motors can run past their rated specs if there is ample cooling. Thats why its safer to have a 60A ESC for a motor rated to 50A. Same with the battery pack, you want a pack with plenty of room for your application. The worst case is a little added weight, which can be useful, but you get more flight time.

Try choosing a prop to load the motor to its max rated Amp load when the pack is peak charged and tested on the bench/ground. In the air the load will be less and the system will have a margin of safety. Check temps when you land as soon as possible and then a couple minutes later. This is very important.

Peak Battery operating temp while under load = 120F
Peak Battery temp at rest after use = <140F (Heat Soak Period)
Ideal Operating Temp = 90-100F

Anything above these temps is a problem. That diagnosis is another topic.

sudstad

I really appreciate everyone's input, as alot of this still seems like rocket science to me!

The plan to date is:
- Scale like flight
- VQ P-38
- 82" wing
- 18lbs (est)
- Motors: eflite 90's - 50a continuous, 65a burst
- ESCs: Castle Ice 100's
- Batteries: 6s 30c 5000mah
- Props: still trying to understand how to size

Do I shoot for a prop that will pull 50a static and expect lower draw in flight?

Chris Nicastro

My Feedback: (3)

Yes, You can try their suggested prop and then work from there. The most important tool in your box should be a Watt Meter, do you own one? If not please get one and use that to check and tune all of your electric planes, helis and boats.

Also if your interested in continuing with brushless planes you should consider a data logging system or expand on a radio system that has telemetry. This way your fully informed both in flight and on the bench. You will know more and learn faster this way trust me!

sudstad

We don't have a watt meter.. but absolutely will get one! eFlite doesn't give a wattage spec. Rather, they say that this motor is good for planes needing up to 1800w. So I'm not sure how to determine what to do.

eFlite recommends for the 90:

- 6s to 8s
- 16x8 to 18x8

I'm hoping to stay with 6s, Do they mean "go 16x8 on 6s and 18x8 on 8s"?

Also, I'd really like to go with three blades. I've read recommendations to "go down one inch of diameter and up one inch of pitch" when going from 2 to 3 blades. Although I haven't found a 15x9 yet. :-/