carlrich

Has anyone converted this p38 to brushless? 4 lbs, 51" WS, 23oz/sq in.
http://www.nitroplanes.com/plinigasrare.html
Looks nice but need two motors and two escs.
I've found mustangs to be difficult to fly due to high weight to wing area and wonder if this one is really 4 lbs brushless.
Also with two escs they say only to use the red wire from one to power the receiver. The escs I'm looking at only put out 1.5A and suggest powering only 3 servos and but there will be 4 used I would imagine. Why can't I connect the power the receiver with both escs in parallel? Same voltage and twice the amps. Many escs come capable of 3 and 4 amps. Wouldn't this be the same?

Carl

Glacier Girl

My Feedback: (4)

Carl,
I tried the parrallel esc thing on mine, I used Tower Pro 2410-9Y motors and their 30 amp esc's.
Mine developed a quirk where unless I powered up the left motor first, the right one would not run. Finally got tired of it and snipped one of the red leads. Problem solved.
Good deal on the motor/esc, $12.00 and $28.00 for each. Got them here www.aarchobby.com
Tony's been a joy to deal with, and I usually get my stuff in 4 days from Hong Kong.
My set up runs 6 servos. 2 aileron,2 elevator, 1 steering, and 1 for the air retracts. Seems to handle it fine on one esc powering it
I liked the set so much I used it in my B25 too.

Very low amp draw from these motors(970kv) the B25 pulls 16.9 amps combined, so I run it on a single TP3S2100 pro lite to keep the weight down. I run 2 of them on the P38, mounted
under the main canopy.
I liked the 51" version so much I'm dying, waiting on the 91" version that's due out this week.

carlrich

Glacier, thanks for the input! I bought 4 of the nippy black 1608/160 motors and will test one today on my thrust stand with amp meter etc. to find out it's capability with different props. Awesome to hear that the 1.5A BEC will run 6 servos without issue. I picked up these outrunners from Hobby Lobby for $20 ea and the 30A esc are Tower Pro from Raidentech for $22.95 - their 10% sale. Likely the same you have. Looking back I could have probably gotten the Tower Pro 15/25A escs for $12.95.
What kind of amp draw and thrust are you getting from your set up?
All up weight?
Really want to get this right.

Would like to know of a 4 motor bomber that isn't too big so I could convert with some of these smallish inexpensive outrunners.

Carl

Glacier Girl

My Feedback: (4)

Carl,
I can get you the specs on the P38 tonight, don't have access to the info here at work.

On a 4 engine job, look at CedarHobbies, they have a B17 that they just came out with.
http://cedarhobbies.net/index.php?id...esc&product=16

Not cheap though.[&:]

Glacier Girl

My Feedback: (4)

Sorry for taking so long. All out weight is 4 lbs ready to fly.
Motors pull 9.1 amps each, 107 watts, and 800 gr of thrust, spinning MAS 9x7 3 blades.
Going to do some searching to see if I can find a little bigger diameter and deeper pitched props as the motors aren't even straining and speed right now is I would say just enough.
Trouble with that is finding a matched set of pusher and pullers, as I run one counter rotater. just like the original.

carlrich

Glacier, thanks for the specs. It gives me something to shoot for when testing mine. You've got plenty of thrust I'd say. Nearly 4 lbs of thrust!
If you haven't posted pics and specs of your retracts already would you do so?
That would look so cool that I'm considering it if price isn't too much and set up not too difficult.
Did you go with larger diameter wheels incase you land off the pavement? I tend to miss or overrun the runway on occasion.

Carl

Glacier Girl

My Feedback: (4)

I got the retrats from SouthEast models. They are supposed to handle 5 to 7 pound bird.
Though I'm starting to see a lot of wear in the nose gear where the strut goes into it.
I have a heavier nose unit on the way. Could be the rough strip is just too much for the standard system. I use the local soccer field and the so/so conditions are pounding the nose gear. Not a cheap set up. Kit was around #300.00[X(]
As for wheels, all I did was replace the stock foam ones with the closest size rubber versions.
The foam ones flat spot badly and I also found the axle holes weren't even close to being in the center. On driveway taxis it looked like a drunken sailor, wobbling back and forth.

I didn't take any shots of the install. Though I can pass on some tips.
Build the nose unit on a piece of 1/8" lite ply outside the bird. Makes setting it up so much easier. I then went in and built up the formers to support the lite ply. Then just slid the whole shooting match in through the back of the center pod and into place in the front.
Where the gear exits the fuselage instead of trying to trim everything, I cut out a big section of the balsa sheeting then made up cardboard templates to get a nice fit. Used the template to cut out a new balsa sheeting, and used a pair of R/E magnets to hold the piece in place. Covered the new hatch and painted it to match. Makes it easy to access everything by just popping off the hatch.
On the rears I left them open, went the PITA trimming method. That way air can get out to aid in cooling the motors and esc's.
What else???????? Oh, I moved the nose wheel back to a more realistic position, and had to play with the retract angle and strut to get a slightly forward rake on it. Ended up having to cut out some of the lower formers and boxing them in to get the nose gear up in, in the retract position. On the rears same thing, though the wheels won't go up in fully. About 1/2 of the wheel sticks out when retracted. Just not enough room where the booms are cut out for the wing to get a full unseen wheel.
I mounted the tank,servo, and valve in the center pod at the back. Used lots of line and quick connectors so I can dissasemble the booms and center pod if need be. Rx sits under the wing in the center pod, right at the LE.
If you need any help give me a holler.

carlrich

Glacier, $300 is out of my price range. Will need less expensive option. Will likely wait until I can consistantly hit the runway before investing in retracts. Would look so cool though!
For grins I'm searching for reverse pitch props so I can run one motor backwards. If I can't find right size prop for my motor I wont be too bummed but thought I'd give it a whirl anyway.
Do you know where to find reverse props? Do you know if the original P38 ran 2,3 or 4 blade props?

thanks for all the info!
Carl

Glacier Girl

My Feedback: (4)

The original ran 3 bladed props. I use 9x7 versions on mine from Master Airscrew. They are one tractor and one pusher versions. Left motor spins clockwise, looking at it from the front, right motor spins counter clockwise, like the later version P38.

carlrich

Great, I'll do a search for master airscrew dealers.
My motors are 1600 kv and spin fast. Testing only one motor; 7x4 prop gives me 22 oz thrust at 15A and 175 watts and 8x4 prop gives 22oz at 18A and 211 watts. On 3cell 2100 battery.
Was hoping for 30 oz thrust at less than 18A. Not going to happen I don't think. Triblades use more amps I think. Would like to try though.

Carl

Glacier Girl

My Feedback: (4)

Yeah motors kv may be a problem. Mine are only 970 versions.
I'm surprised the thrust didn't go up when you went with the 8x4's.

Found another site with cheap electronics. Obviously it's an engrish one, instead of brushless they list stuff as BLUSHLESS. LOL
http://www.bidproduct.com/part/Produ...S%20ESC_9.html
40 amp esc $25.50
80 amp esc $36.50[X(]
May give a couple a try just for S&G's.

carlrich

Glacier, can you tell me if the C.G. point is measured back from the front middle of the wing where the canopy is or is it measured from the outside of either one of the fuselages on the P38?

Do I turn the plane upside down to check CG from the top of the wing. Or right side up to check CG from bottom of wing?


Mine is built and I'm just trying to decide where to put the two batteries. I have prewired them to be in the gas tank compartment behind the firewall. May need to open up more air inlets.

Carl

Glacier Girl

My Feedback: (4)

Carl,
I measured right up against the center pod, Used a CG stand and flipped the bird upside down.
If you are using the included gear you're good to go. If you use retracts, see how much the CG changes when the gear goes up.

Cooling "inlets" are needed, and don't forget some exhaust ones too, gotta let the air out.

My packs sit up under the main canopy, I get airflow for them from the nose gear opening, and I have the canopy sit not quite flush at the rear, to let the air escape.
I also opened up the intakes on the fiberglass motor cowls to cool the motors, air gets out the rear through the landing gear openings.

Make sure you have lots of runway, and don't try and horse her off the ground. She'll let you know when she's ready.
And she will come in fast on landing. So be prepared.

Best of luck.

carlrich

I have built and flown this P-38 and maidened today. Here is what I'd want to know if I were considering this model.

It is an easy conversion to electric. I am a slow builder/tinkerer and put in 25 hours total including having to rewire to put my lipos under the center canopy after running all wires to the area under the wing as it turned out to be too nose heavy to put them under the under the wings in the nice big open area. If you use lighter motors (2 ounces) you may be able to put your lipos behind each firewall and under the wing.

My personal opinion is that two lipos in parallel is better than one lipo seperate to each motor.

I had two perfect landings (only two flights) and that is not typical for me. I attribute that to lowering the front of the plane by having the nose gear up in the plane further than what would create a level plane. This also tilts the wings so the front is lower than the rear which helps hold the plane down when you are taking off and when landing the rear wheels will hit first as opposed to what happens when you hit front wheel first (BOUNCE).

The instructions leave something to be disired as their are several steps missing like the fact that you are supposed to put a wooden dowl in the rear of the wing halves to help hold them together and that their are two more dowls to put in the leading edge of each wing to secure the front of the wing into their fuselage. There is not markings for where they go in. I put the wings in place and made a little mark with a marker where the dowl would likely go and then found the hole by running my finger over that general area.

You can use just one servo for the elevator
I used 4 HS55 servos in the plane and all are working fine.

The hole in each rear wheel was off center so I used two wheels from a Super Sportster EP that were of the same size. Will be looking for larger light weight wheels for grass landing and take off.

The firewall portion that you must build and attaches to the motor was made of two pieces of 1/8" ply glued together. Both were glued without being centered. They come apart easily with a hobby razor that extends several inches like the yellow and black ones from Home Depot.

The wheel mounts are shown being mounted with the part that goes up into the fuselage being on the inside portion of the fuselage (there are two fuselages) so I drilled a hole to do this. Then I noticed when taking the wing off later that a block of wood was added to the opposite side to support a hole being drilled on the outside portion of the fuselage.

The picture shows the CG being measured from one of the fuselages when I believe it was supposed to be measured 3" back from the leading wing edge when starting from beside the center canopy and not an outside wing. I got this advice from another person on this forum and the plane flew great.

My final all up weight was 63 1/2 ounces so just under 4 lbs including batteries and 1 3/8 ounces of lead on the tail.

I used two nippy black 1608/160 motors. $20 each from Hobby Lobby
two Commonsenserc 2000mah 3 cell 8C packs $35 for both
two tower pro 25A esc from raidentech at $23 each

The motors weight 90grams/ 3.12 ounces and had to be built out 1/4" from firewall to make a perfect mount for the 1 3/4" red spinners that look so nice on this model.
I used 7x4 apc slow flyer props that produced 44ounces of thrust at 29amps and 330watts combined.
I static tested some 8x3.8 apc SF props at 58 ounces thrust 40 amps and 440 watts but they may be overkill and the motor is only rated to 16A (each motor) continous. In the air the actual amps used at full throttle would be less that 20A each motor and I intend to fly this set up at some point.

The plane flies nicely at 3/4 throttle and really zips at full throttle. It will not vertical for any period of time but will make a nice loop. I've only had two flights and only attempted one loop thus far.

All in all a nice flying model that looks way cool in the air and could be a static model it looks that good period. Landings were as easy or easier than any of my other 6 planes and I stress the lower front end idea.

I got alot of good info from this thread. Thanks to all especially Glacier!

Carl

Glacier Girl

My Feedback: (4)

Carl,
Great flight report!!!!!!!!

Welcome to the brotherhood of the P38.

I installed the new nose gear in mine yesterday as it rained all day.
Was not fun. Had to hack out all the sheeting I installed originally, cut out to fit the much bigger retract, and rebrace it all over again. [:@]
Some new covering and she's ready to go again.

Just in time too. According to snail mail site, 90" version is to hit tomorrow.

Glacier Girl

My Feedback: (4)

Carl,
When that one get's boring this is availible.
1/2 of the wing for the new 90" version. Gonna need a bigger truck.[X(]

carlrich

Holy crap that's big! I just had my third flight today with the P-38 so I'm no where near bored yet. Loops and rolls well. Will try another prop for more speed thrust. Speed is fine. Lands very well. Makes me look good and that is a job!

WHAT are you going to use for motor, esc and batteries?????????????

I don't know if the Eflite 46 is big enough but I can tell you it is a powerful motor. A buddy of mine has one and it will pull a 72" WS 5 lb trainer off the runway in a hurry and climb almost straight vertical on a 4 cell pack. I had a Tower Pro 3520-7 in a 5 Lb 3D machine and felt it did a good job but was not as capable as the 46 from eflite. 1/2 the price but I would go with the 46 next time.

Carl

Glacier Girl

My Feedback: (4)

Carl,
I'm still up in the air about motors. kalog recommended looking at the 60 eflites also.
But the price on the 3520's look really appealing. I have 2 of them already looking for a home.
I have to do some checking as from what I understand there are at least 2 versions out there.
A 720 and a 590 kv version, and for some reason I have stuck in my mind that these that I have were advertised as 670 kv. I'm going to get some big old 3 blades, somewhere around 15 x10's and run the motors up. We'll see what happens. Probably going to run a 5 or 6 cell pack as I'm guessing around 50 amps from each motor and somewhere around 650-700 watts each. There's a real good forum on these over on RCG. I've been talking with some of the guys there. Real brains on these electric motors, me I'm like a babe in the woods, when they go into some of their conversations.

carlrich

If you've got them already you may as well give them a shot. I think the eflite 60s would do a wonderful job but likely overkill. 100watts per pound should be plenty I would think and the 3520-7 can do that. After seeing the eflite 46 I was just real impressed with how smooth it ran and seemingly had more power maybe due to greater efficiency / better quality. Maybe all in my head. Will look forward to some pics and specs as you get that big bird ready to fly.
I'm currently looking for a ducted fan jet. An arf preferably already painted. Not into kits yet. Need speed and don't like the ones made of flat foam.
Hobby Lobby has a couple and the videos are great.
http://www.hobby-lobby.com/f86.htm
Would prefer something larger than the 30" x 30" of above.
The really sectacular ones at 100mph plus are unfortunately $400 pre motor.

Carl

algutkin

My Feedback: (1)

I have been watching this thread with great interest. I'd love to see some more build pictures, especially the 90" being constructed by Glacier Girl. I love ARFs also Carl, however, some of the more complex ARFs seem to require the builder to re-invent the wheel. For example, putting retracts in the P38. Why can't the design engineers do it right the first time, the added expense would be small.

Glacier Girl and Carl,

Why haven't you considered the Model Motors AXI line?

I have been eagerly waiting for the 90" P38 to arrive, as I discovered it takes the same time to build a small plane as it does a large plane, might as well start big. However, after reading this thread, building the 90" bird may not be an easy slam dunk construction process if it is anything like the smaller craft. What is your first impresseion Glacier Girl?

Al

carlrich

Al, I went with Nippy motors because they were $20 each. I feel out done by Glacier as he only spent $12 each. I don't know what Axi motors would cost. I haven't heard a bad thing about them and I'm sure they are top quality but if I find a less expensive route and I believe I can make it work and save $100 in the process I usually jump on it. Like commonsenserc lipos and Thunder power. Not many people question thunder power makes a good pack. I have one and it works fine and I have one no name from rc dymond that stinks out the wazoo. The commonsense packs seem to be awesome packs with every bit the power of the comparable TP packs if not more as they sure seem to be very accurate on labeling them as 15C packs as opposed to calling the 20C when they would compare to others 20C packs easy.

I'm with you on building an arf. Always some challenge and I guess I look forward to some level of challenge. Would love inexpensive retracts that would hold up on this P-38!

Get the 90" I want to see what you and Glacier can do with them!

Carl

algutkin

My Feedback: (1)

Oh no Carl, you and Glacier Girl build one first. You guys figure out the engineering changes, make the retracts work, modify the design to make it better, and finally, purchase the various props and battery combinations to test out the Motocalc and Electricalc opinions. You guys are the ones that make ARF a reality. Other than that, ARF just means "We covered the model for you and installed the hinges. The hobbiest is responsible for making our poorly designed concept actually fly" LOL

Take care
Al

Glacier Girl

My Feedback: (4)

Why did I not go with the Axi's?
Actually I looked at them a long time ago. Mookie1 did an elec conversion to a VQ Models 83" P38 and got me started on this whole P38 affair.
VQ = $600.00. N/M = $249.00
Axi(4130-16's?) around $170.00 a piece. TP 3520's $50.00 per.
I figure I'm ahead of the game so to speak by what $420.00?
Should put a good down payment on the packs.

Carl,
Something that may have been a problem on your 3520. Supposedly the stock bearings are marginal at best. Noisey and sloppy. Replace them and they get much better. I guess I'll do it to mine when the time comes. Still cheaper the the Axi's. LOL

Oh and this may help with how big it is.
I dry fitted some of it together and threw the 52" version on top, just so you get some idea of the scale.
I'm impressed to say the least at the workmanship on it. Somebody designed it to be light.
Now just have to figure out how to build it to fit in the van. Or I guess I could strap it to the roof rack.

Glacier Girl

My Feedback: (4)

Carl,
Be careful looking at ARF EDF's.
I built this one. F20 TigerShark from Warbirds RC.
Unlike the P38 it came with an almost 400 page build CD. Plus there was an optional 150 or so one for installing air retracts. And this is considered an ARF.

Hang on a bit, My bud Ray, aka DepronJets, is developing an EDF bird as we speak.
His kits are a snap to build. All depron and plastic.
Has a 5 1/2 foot, yes foot long, F16 that is a blast to fly. And I just finished his Bae Hawk this weekend. Both are prop jobs, but you never see them in the air.

carlrich

Hang on???
It's almost been a whole week since I built a plane!!!
I have a multiplex twin star that is pretty fast as a twin pusher. Sounds great too. Louder whine that would be expected. Really wanting the fast DF.
Check out this video from X-flight on a falcon. $90 for plane $90 for motor.
29.5" WS, 42" L, 2.2 Lbs
click on "relevant video" on the right.
http://www.x-flight.hk/e/products/pr....asp?ic=XFP006

Do you think your plane will come in at the 11 Lb mark?

Carl