PDA

View Full Version : How does this power setup sound for my P-38?


ForestCam
06-06-2006, 06:04 AM
I recently accuired a Nitromodels P-38 and I've been trying to figure out what to put into it.

I was first leaning towards the Nippy 2510/114s after seeing Cubano8's video but at $57 per they're a little out of my price range.

Cost is a factor so I was pleasently suprised when I saw that K CLOSE powered his with a pair of BP-21's but he never said what the preformance was before he crashed.

I'm looking at a pair of BM2409-12 1600Kv DELTAs (w/3mm shafts), Tower Pro 30AMP Brushless Programmable ESCs powered with a pair of Polyquest 3S 2600's that I already have.

From my research on the BM2409-12 running an 8x6 prop I'd get 33.39 oz. of thrust drawing 27 amps 306 watts per motor so at WOT my power to weight should be close to 1:1

And I can get everything for around $65 shipped

Gliderbill
06-06-2006, 03:53 PM
Gliderbill here:
Interested in knowing the weight of your P-38, and wingspan. I am building the older Guillows 40" rubber powered one but will use e-power. It will be less than 16 ozs AUW, (hopefully!). I'll leave off the gear and most of the plastic, (read...Heavy!), parts, and am only wiggling the ailerons and elevator. Noted that you measured the thrust of your motor(s). What did you use?

Things a pilot can't use...Runway behind and altitude above.

Gliderbill
06-06-2006, 04:03 PM
I recently accuired a Nitromodels P-38 and I've been trying to figure out what to put into it.

I was first leaning towards the Nippy 2510/114s after seeing Cubano8's video but at $57 per they're a little out of my price range.

Cost is a factor so I was pleasently suprised when I saw that K CLOSE powered his with a pair of BP-21's but he never said what the preformance was before he crashed.

I'm looking at a pair of BM2409-12 1600Kv DELTAs (w/3mm shafts), Tower Pro 30AMP Brushless Programmable ESCs powered with a pair of Polyquest 3S 2600's that I already have.

From my research on the BM2409-12 running an 8x6 prop I'd get 33.39 oz. of thrust drawing 27 amps 306 watts per motor so at WOT my power to weight should be close to 1:1

And I can get everything for around $65 shipped

Gliderbill here again! Now I know what they mean about "short-term memory loss!. "...1:1 power to wgt. ratio". DUH! So your plane weighs about 33 ozs. or so. Just ignore this 80 year young flyers' odd requests! Maybe it's the old grey matter reacting to the banana oil residue from years past!

ForestCam
06-06-2006, 06:40 PM
Actually the lightest I've heard someone put one togeater was close to 3 1/2 lbs. and I plan on going the light route too, actually the heaviest part will be the 12 oz. of batteries it'll be lugging around.

I found the graph someplace online that I can't seem to find at the moment and don't forget that's 33 oz. of thrust PER motor for a total that's a shade over 4 lbs. total.

blackdogrc
06-09-2006, 05:38 AM
From my research on the BM2409-12 running an 8x6 prop I'd get 33.39 oz. of thrust drawing 27 amps 306 watts per motor so at WOT my power to weight should be close to 1:1

Hi ForestCam:

I'm concerned your BM2409-12 will not pull 27 amps. Aren't these rated at 100 watts max, but can be pushed to 150 watts with a shortened life span? Maybe I'm wrong, I'll do some checking.

I designed a foam p-38 and run it with two BM2410-24 motors. Speed is about 55mph, all up weight is about 17oz with battery. Take a look: www.blackdogrc.com/parkflyers.jsp
This setup pulls 23amps, and I run with a 1100 3s1p, 1300 3s1p or 1500 3s1p lipo. Flyes like on rails. Really, really fast. There are videos and photos on my site.

With GWS 9050HD, you get 25oz thrust each, or 50oz all up and 50 on the radar gun. If you bump to GWS 1060hd, you get 30oz thrust, 60 oz total but a loss of speed to 42-45mph. I personally fly with 8x6 and get the 52-55mph out of it.

I sell the motors for $16, and the 1100 3s1p lipo for $29. You get $5 off your first order(when you make an account), so two motors AND a light 3oz lipo will be $62, minus the $5coupon = $56! I feel these are the best deals going anywhere. The motors are www.blackdogrc.com/brushless.jsp#BM2410-12 (http://www.blackdogrc.com/brushless.jsp#BM2410-12) You can see how fast the plane goes on the motors in the video. But, granted, my setup is a bit lighter than your setup.

I exhaustivly test every product I sell, so I tested the motors against a bunch of different props and batteries. I fly the 2410-12 motors and love them.

Here is the link to the motor graph on the BM2409 and the BM2410 motors:
www.blackdogrc.com/brushless.jsp#BM2410-12 (http://www.blackdogrc.com/brushless.jsp#BM2410-12)

Hope this helps!

df, www.blackdogrc.com (http://www.blackdogrc.com)

K CLOSE
06-12-2006, 12:16 AM
Cost is a factor so I was pleasently suprised when I saw that K CLOSE powered his with a pair of BP-21's but he never said what the preformance was before he crashed.

Forestcam--- I thought I stated in the posting that performance was good.:confused: I guess I didn't. The P-38 flew FANTASTIC with this set up. Two flights, both about 10 min and the batteries ( 11.1v 2200mAH were undamaged in the crash ) still had about 900 mAH left when cycled. I'm 95% done re-building the plane (fellow posters were right, after I got home I decided I could rebuild it) and it is still JUST over 3lbs. She would not do "unlimited vert" but it sure as heck was not a scale rate of climb. She could go vert for about 8-10' before I had to level off. She'll fly again soon, and the only change I'm going to make (besides the receiver) is to wire the two batteries together. I cut hinged hatches in the bottom of the cowls to access the wires but I think that (A) access will be better at the field under the canopy and (B) hopefully the LVC's will kick in at the same time should I screw up timing. The plane slowed GREAT for landing, but a successful dead stick would take a better flyer than I. :eek:
As a low buck P-38 this set up is unbeatable, and as my largest model and first twin to date--much easier to track in the air. My F2G Super Corsair (my icon pic) is just about imposible to see in the air. Granted it flys much faster, but I really think it's the size that makes the difference. The P-38 covers a lot of ground, but somehow did not seem to shrink the field in the same way. Just my 2bits.

ForestCam
06-12-2006, 01:39 AM
Glad to hear it! Still waiting on some funds that are due me (gotta fire off some DUN emails Monday) but I plan on finishing it soon as I can.

I'm thinking about making hatches in the bottom of the pods for battery replacement, I don't think going through the SC covers is going to cut it.

I've had a couple of setbacks too, one of my 3s 1300 mAhs bit the dust for some unknown reason and I had to rob two servos out of my CAP to keep my SlowStick flying.:rolleyes:

This hobby's gonna break me but I'll be smiling all the way to the poor house.:D

darkside212
06-12-2006, 04:04 AM
K close what size props were you using on the bp21s?
(an 8040 will give around 23 ounces of thrust on a 3 cell lipo drawing 12-14 amps)

I converted a life foam glider to rc....I have 2 -21's on it with 5" props pulls it around nicely. AUW is about 2 lbs.

I tried it with 8" props and it was just too much :) basically you could take off straight up!

6" props were good to but I broke one on a landing (in tall grash/shrubbery oops)

either way I was using 2 different lipos: 1 TP 2100 15c and with the 8" props the battery would warm a little the other is a EP20C 2200 11.1v the temp doesnt even change. If you do use a larger prop I would definitely use a higher discharge lipo. Using one will definitely save some weight and flight times should be at least 10minutes

darkside212
06-12-2006, 04:14 AM
also you can utilize 2 15a esc's as oppose to 2 30as. This will save you some cash, and weight. I made a simple harness out of 2 male "ultra" style plugs and one female-simple and effective.

darkside212
06-12-2006, 03:06 PM
also: where did you get the kit from?

K CLOSE
06-13-2006, 02:59 AM
Darkside,
I got the kit from nitromodels, and found it because of a posting on wattflyer. It's BP 21's on 11.1 2200 ART-TEC lipos, one 30 Amp speed control-one battery per motor, spinning an 8x4 prop. I want to wire the two Lipo's (+ to +, - to -) in an attempt to ensure the LVC' cut in together, hopefully avoiding a one on/one off situation. The batteries are in the motor mounts, and as such she is right on the CG. Cool idea on the ultra plugs though.

darkside212
06-13-2006, 03:46 AM
OK
there is another wattflyer interested in a p38 setup,but the model he wants is from raidentech I'm curious if they're the same:
www.raidentech.com/pnigararecor.html (http://www.raidentech.com/pnigararecor.html)


btw
30A escs are overkill for those BP21's :)

Grasshopper
06-13-2006, 03:50 AM
Good question DS. I've been following this thread too?

K Close, do you by any chance have any photos of your battery placement?

Tom

darkside212
06-13-2006, 04:03 AM
Yeah I was trying to find that info out for you!

Grasshopper
06-13-2006, 04:09 AM
Appreciate it. I'm going nuts waiting to get mine.

darkside212
06-13-2006, 04:24 AM
been there.....But you gotta draw the line somewhere....otherwise I'd have every plane ever made! :)

Grasshopper
06-13-2006, 04:26 AM
And your point would be.................

darkside212
06-13-2006, 04:31 AM
that I have an illness :)

darkside212
06-13-2006, 04:35 AM
Seriously though: K Close do you know if the two planes are the same, and do you have pics/dimensions of the battery hatches?

Thanks?