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Old Jan 20, 2012, 04:01 PM
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starboardplan's Avatar
sacramento , california
Joined Jan 2008
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I thought i would share with you guys my cousins bananahobby p-38 that we have decided to turn into more of a scale project . We still have a ways to go before its complete.

Cheers...
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Old Jan 20, 2012, 06:54 PM
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Thanks bro!! Nice work!!
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Old Jan 21, 2012, 12:52 AM
Captain Coolite
Rob Knox's Avatar
Meringandan, QLD , Australia
Joined Jan 2011
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Quote:
Originally Posted by starboardplan View Post
I thought i would share with you guys my cousins bananahobby p-38 that we have decided to turn into more of a scale project . We still have a ways to go before its complete.

Cheers...
VERY Nice, keep us posted of your progress.
Rob
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Old Jan 21, 2012, 07:40 AM
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Hink64's Avatar
Cape Coral, Fl
Joined Jan 2010
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Quote:
Originally Posted by starboardplan View Post
I thought i would share with you guys my cousins bananahobby p-38 that we have decided to turn into more of a scale project . We still have a ways to go before its complete.

Cheers...
Good start - is that the Durafly F4U next door?
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Old Jan 21, 2012, 05:10 PM
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starboardplan's Avatar
sacramento , california
Joined Jan 2008
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Thanks guys , yes that is the durafly corsair on the table too . I got it so that both aircraft are kind of close in scale when we fly formations. The durafly F4U is probly one of my best purchases .
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Old Jan 21, 2012, 07:41 PM
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Grand Rapids, MI
Joined Jun 2005
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Flew my p-38 off the frozen parking lot pavement this afternoon. 20deg and very calm breeze. Thumb got a bit frozen, but put 2 packs thru her. Was good to get it up in the air again. I love how easy of a flier it is! Got to work on giving it some scale details this winter and get the drop tanks and retract doors back on.
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Old Jan 22, 2012, 02:46 PM
will work for stick time
Don Shimoda's Avatar
Austin, TX
Joined Apr 2006
267 Posts
Just bought the V2, and it's my first twin engine, although I've flown everything from gliders to warbirds to edj jets.

After reading through this thread, I'm still not clear on the best solution to losing a single engine to lvc. Which red wire exactly do I need to cut, and is their anything else I need to do, besides not running may battery down to lvc?

Thanks, I appreciate the help.
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Old Jan 22, 2012, 04:11 PM
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Ah Clem's Avatar
Joined Mar 2005
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For preventing it, not running the battery down too far is very important.

If it happens, kill the power to the good engine right away (correct procedure on a full sized P-38 as well, from what I have read), get the nose down and glide in. Drop the gear right before touch down.

I am not much of an airplane pilot and I lost an engine, physically (I did not check the motor mount set screws before flying). It was about 100 feet up and I got is turned around and landed safely.
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Old Jan 22, 2012, 04:39 PM
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Galand's Avatar
Long Island, NY
Joined May 2010
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Quote:
Originally Posted by Don Shimoda View Post
Just bought the V2, and it's my first twin engine, although I've flown everything from gliders to warbirds to edj jets.

After reading through this thread, I'm still not clear on the best solution to losing a single engine to lvc. Which red wire exactly do I need to cut, and is their anything else I need to do, besides not running may battery down to lvc?

Thanks, I appreciate the help.
The smart thing to do is not to run down the batteries as Clem says but I guess you could have figured that one out by yourself.
I incorporated on of these:
http://www.dimensionengineering.com/LipoShield.htm
between the Y-lead to the ESC's and Rx.
Do a search on this thread under Liposhield
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Old Jan 22, 2012, 05:15 PM
will work for stick time
Don Shimoda's Avatar
Austin, TX
Joined Apr 2006
267 Posts
Of course not running the batteries down is a good first step. What kind of flight times do you guys get on the stock motors with one 2200mah or 2600mah 3 cell battery?

Galand, it looks like the lipo shield will soft cutoff one motor before it reaches lvc. Do I need just one lipo shield or one for each esc? Thanks for your help.
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Old Jan 22, 2012, 06:59 PM
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Long Island, NY
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Quote:
Originally Posted by Don Shimoda View Post
Of course not running the batteries down is a good first step. What kind of flight times do you guys get on the stock motors with one 2200mah or 2600mah 3 cell battery?

Galand, it looks like the lipo shield will soft cutoff one motor before it reaches lvc. Do I need just one lipo shield or one for each esc? Thanks for your help.
Can't tell for flight time because I have 2x1650mAh. One in each boom. I get somewhere around 12 mins.

Re LVC: What you think is not correct, it is exactly the opposite. The single Liposhield sits between the Rx (Ch3) and the Y-lead going to the two ESC's. If you set the LVC value of both ESC's at a voltage below the 3V cut-off value of the Liposhield, the Liposhield LVC will get activated first, before the ESC's LVC. Now because of the Y-lead set-up both ESC's and motors will get cut-off at the same time.
This ofcourse does nothing for a mechanical failure of one of the motors.

EDIT: do not use a SmartBec see:
http://www.rcgroups.com/forums/showp...postcount=4028
And Post # 3702
http://www.rcgroups.com/forums/showp...postcount=3702
and subsequent postings.
Although with a single battery it probably does mot matter.
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Last edited by Galand; Jan 22, 2012 at 08:31 PM. Reason: Added Info Correction ol Lipo capacity
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Old Jan 22, 2012, 07:14 PM
Captain Coolite
Rob Knox's Avatar
Meringandan, QLD , Australia
Joined Jan 2011
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One 2200 mah Battery flight time

G'day Don,
I tend to fly conservatively, so I'll typically only fly for 5 mins on the single 2200 battery. This provides me with sufficient power for go arounds should I mess up landing approaches.

I don't fly flat out normally, I manage the throttle depending on what I'm doing during a flight.

I have a few 2200's so, 5 mins is fine for me.
Hope this helps.
Rob
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Old Jan 23, 2012, 12:46 AM
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Monahans TX
Joined Sep 2010
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Another option is to disable the LVC completely and use a telemetry system (Quanum, for example) to keep an eye on battery level.
It'll let you know to get on the ground with an audible alarm, and you can set it to any voltage you want.
The Quanum also monitors individual cell voltage by using the balance charger lead, and other options include a temp monitor probe and current draw.
Hardly adds any weight to the model, and it really helps to know you're getting close to LVC (if you keep it armed) before it actually happens...much more accurate than using a timer especially when you don't always fly your models the same way during every flight.
I test all of my models that are large enough to carry it with 3 criteria:
-Longest possible duration (using as little throttle as possible)
-Full throttle from start to finish
-Aerobatic routines with varied throttle settings (no straight and level flying, only all out aerobatic maneuvers)

I probably wouldn't have been able to test right up to LVC safely without it, as I knew when I only had mere seconds to land before LVC.
It gave me an idea of the minimum and maximum flight times, as well as what I can expect for fun/spirited flying.
The Quanum really helped me put flight times into perspective, and once I got comfortable with it I could almost predict when the alarm would start.

LVC was a non-issue with my P38, but I still had to worry about losing motors and props in flight.
It went in 4 different times because of losing motors and props and not once did I have a problem controlling it.
3 of them happened around 50-100ft, and one happened less than 5ft from the ground right in front of me.
Just as long as you remember to chop power and do your best not to over control when you get nervous about it you'll do fine.
If you have time to think about it, roll the good engine below you and hold a shallow turn until you're lined up with the field again...but it's definitely not a law set in stone.
Any sort of shallow or gentle maneuver that gets you back to the field is a good call.
She glides quite well with only one motor, little to no yaw issues, and is very stable with an aft CG.
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Old Jan 23, 2012, 12:48 PM
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United States, CO, Colorado Springs
Joined Aug 2003
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Quote:
Originally Posted by Galand View Post
EDIT: do not use a SmartBec see:
http://www.rcgroups.com/forums/showp...postcount=4028
And Post # 3702
http://www.rcgroups.com/forums/showp...postcount=3702
and subsequent postings.
Although with a single battery it probably does mot matter.

I've used SmartBECs on twins wth single or multiple parallel batteries just fine for years. Just make sure to have the positive leads from the ESCs to the BEC disconnected from both each other and the BEC. (An extra step that isn't necessary when using a SmartBEC with a single ESC) THe problem you're trying to avoid here is one LVC tripping, and the other motoring along happily because the lower draw keeps the second LVC from tripping. (THe 1st one won't reset by itself)

If you have totally separate batteries (i.e. no cross-bridge between them so they aren't actually running in parallel) then it gets much more complicated because there's no *good* way to detect or deal with one battery going flat before the other.

One of those posts talks about the UBEC wires being too small for 20A, too. Drawing 20A through a BEC is preposterous! Only VERY LARGE aircraft look for this number, and they always use seperate, redundent, batteries. Your P-38 draws something under 1.5 most of the time, maybe 2 or 3 if you're pulling up the gear during a high-G maneuver.
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Old Jan 24, 2012, 04:53 AM
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yorkshire UK
Joined Oct 2007
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I just disable lvc and time flights so batts have plenty left anyway that way your gonna make lipos last longer and even if you manage to somehow drop yr batt volts a bit too low its not gonna shut one motor downb4 other and make you crash-worst case you loose a lipo but most lipos will still charge up of, unless of course you ignore the fact that your plane has not much power and carry on flying till yr batts drop bellow voltage needed for rx then you will crash.
Just my 2 pence worth but its simple and costs nothing!
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