RE: 1/2A trainer anyone?  
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RE: 1/2A trainer anyone? - 7/21/2007 1:51:17 AM   
Bipe Flyer



Posts: 4981
Joined: 11/6/2002
From: Mission, BC, CANADA
Status: offline 		The Receiver will be fine. I'd go with Hitec HS-65 servos and a 250mAh to 370mAh NiCad or NiMH receiver pack. http://radicalrc.secure-mall.com/shop/?shop=1&cat=19

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1/2A all the way!
Club Saito #151

(in reply to martin_solo)
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RE: 1/2A trainer anyone? - 7/21/2007 5:53:21 AM   
martin_solo


 

Posts: 31
Joined: 12/19/2005
From: CampinasSao Paulo, BRAZIL
Status: offline 		Hi Bipe,

thanks for all the tips!

I visited the link and found the

Radical RC 350mah Sanyo NiCad 4-2/3AA cell 4.8V Flat RX pack 1.975Oz $14.75

and the

Radical RC 370mah NiMH 4-2/3 AAA Cell 4.8V Square RX Pack 1.05Oz $ 11.00

The NiMH is lighter and cheaper, is there any disavantge against NiCad batteries?

thank you

Martin



(in reply to Bipe Flyer)
       Post #: 727

RE: 1/2A trainer anyone? - 7/21/2007 6:11:03 AM   
Bipe Flyer



Posts: 4981
Joined: 11/6/2002
From: Mission, BC, CANADA
Status: offline 		The only disavantge is that NiMH needs a different charger if you want to quick charge. If you are going to slow charge overnight, you can use the same charger for NiCad and NiMH.

_____________________________

1/2A all the way!
Club Saito #151

(in reply to martin_solo)
       Post #: 728

RE: 1/2A trainer anyone? - 9/17/2007 4:31:53 AM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		I used to do a lot of control line and rubber power maybe 20 years ago, but am completely new to RC, so I need a trainer. I am building Keith Laumer's Push-Up, slightly reduced in size, as I have mentioned on the Keith Laumer thread. I am making a lot of mistakes, cause I am so out of practice, but I am optimistic. I plan to use a two channel, rudder and elevator, control, left over from the Cox P40 Warbird that failed to teach me to fly RC, and a Pee Wee. (The speed control is fried.) I have not flown combustion free flight, but I figure having experience with rubber power I can fly it with little help from my clumsy RC abilities.
Assuming it survives that, the next step will be too teach my nieces and nephews to fly it.
One question now is how to power the Cox electrics. They work in the Micro Warbird on 7.2 V. and less when the battery is running low. The Ni metal hydrides from the Warbird weigh twice as much as the engine, so I am thinking two disposable Li cells, maybe watch size. I suppose Li polymer would work if I found ones that are small enough and can be charged with my charger that has 1/2 amp minimum current output.

< Message edited by David Ingham -- 9/17/2007 5:07:41 AM >

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       Post #: 729

RE: 1/2A trainer anyone? - 9/17/2007 5:25:50 AM   
skaliwag



Posts: 1111
Joined: 1/9/2003
From: santa cruz, CA, USA
Status: online 		Iv'e never tested and checked but I think the Cox Rx from the Warbirds cut Channel 3 at 5.4V. With #3 not being used you won't know when you have reached a point of no return with a pair of Li Po's. The stock bats are 6 cell 220Mah.. and weigh 1.3oz. You can always take a cell out. But you may need the extra weght at the front to get a good CG. What engine are you going to use? If its a TD .010, 7oz is a threashhold... (Skimmed the thread but couldn't see it)

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Real Airplanes have Round Engines and Two Wings.

(in reply to David Ingham)
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RE: 1/2A trainer anyone? - 9/17/2007 8:29:39 AM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		Thanks skaliwag.
Yes, the manual says it cuts the motor in time to land. I will be left with only testing the voltage between flights.
(I have gathered that lipos don't like to be fully discharged.)
Those numbers may be of much use to me. 1.3 oz is less than I guessed for the battery, but still much more than the weight of the engine, tank and fuel.
Taking a cell out would help the weight, but I don't think the charger would work.
It does appear to be coming out tail heavy, so I plan to put the battery well forward.
I am more afraid of weight than of loss of control. It is a free flight design and doesn't really need my control. But weight means speed which, for a beginner, usually means damage.
I would like to use an 010 but my $ 77 bid did not lead long on eBay, and they may be fussy. I have two Pee Wees. They weigh (not checking my notes) around 0.8 0z. They are the engine shown in the plans, so its coming out tail heavy is my fault (out of practice).
Having committed to building the model, if the left-over Cox controls don't work, I will have to try to find some that do, or fly free flight on drops of fuel.

(in reply to skaliwag)
       Post #: 731

RE: 1/2A trainer anyone? - 9/17/2007 9:13:23 AM   
skaliwag



Posts: 1111
Joined: 1/9/2003
From: santa cruz, CA, USA
Status: online 		How much Wing Area does the Push Up have? I don't like to ask the Pee Wee to handle any more than an 11oz model.

_____________________________

Real Airplanes have Round Engines and Two Wings.

(in reply to David Ingham)
       Post #: 732

RE: 1/2A trainer anyone? - 9/17/2007 10:06:05 AM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		I get 91 in2. wing area for my plan.
The engine is around 0.80, or at least less than an ounce.
The fuselage is 1.1 oz before covering.
Plus the wing and tail.
You say 1.3 for the old battery, if I can't do better than the Cox µWarbird battery. The RC equipment was about a pound when I watched people fly RC. I hope Moor's Law has trimmed it down below an ounce.
So I have the propeller on backwards to keep it from going too fast.
My ideal goal is to have an RC airplane that children can fly, with only occasional repairs.

(in reply to skaliwag)
       Post #: 733

RE: 1/2A trainer anyone? - 9/17/2007 10:52:07 PM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		I bought two CR2032 3 V watch cells and soldered them in series. They do power the Rx and servos. The electrics draw 50 mA steady with bursts over 100 when moving the tail. The Li cells are rated 220 mAh, so they should be good for a couple of hours switched on or ten years hanging from the ceiling. They weigh about half an ounce together. The electrics now weigh about the same as the un-covered fuselage but still around twice the weight of the engine. I plan to try the Ni metal hydrides on a control line trainer.

(in reply to David Ingham)
       Post #: 734

RE: 1/2A trainer anyone? - 9/24/2007 6:09:05 AM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		Fortunately, I found, before I flew it, that the watch batteries don't have enough average current capacity to work the Cox receiver (Rx) and servos for long. I now have two of the smallest camera Li cells that I could find. My little volt meter shows no drop when working the servos with these. The next step is glide testing. I am looking for the park with the most grass.
I had an RC trainer that I bought from a friend. I asked another friend, who was a licensed pilot at the time, to try it first, and he broke both the air frame and the engine. He bought me the new engine parts, but I never got around to fixing the air frame. Thanks to Moor's law, my Push-Up should be small and light enough not to break on the first crash.
There are two types of trainers. There are trainers like the (full size) PT19 that have dual control, and trainers like the Wright Flyer and the Flying Flea (http://en.wikipedia.org/wiki/Flying_Flea) that are designed to allow the pilot to teach himself.

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< Message edited by David Ingham -- 9/24/2007 6:17:25 AM >

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RE: 1/2A trainer anyone? - 10/23/2007 8:13:54 AM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		The most serious problem, as an elementary trainer, seems to be too much power. Either it didn't slow down with the needle valve as well in the field as on the bench or I got carried away. By bad luck, it hit on asphalt pavement, and now it needs a new fuselage. Back to putting the propeller on backward, and I need more head gaskets. Maybe it is too small for this engine. 010s are so expensive now. (My car broke the same day.)
I am still convinced that small size is the key to a survivable trainer. The limit is the electrics, which still weigh several times as much as the engine. I have them soft mounted, but their weight requires it to fly faster than it would have to for FF or CL. In this respect, the advantage of RC is better tolerance for wind.

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RE: 1/2A trainer anyone? - 10/24/2007 1:29:09 AM   
tri-pacer


 

Posts: 108
Joined: 5/20/2007
From: napa, CA, USA
Status: offline 		Hey Dave,

A way to slow it down a bit, is to scale the airplane up a bit, or at least the wing, to lighten the wing loading. For my Laumer project, the Yardbird, I wanted something a little more relaxing; so I left everything the same, and gave it a 38" wingspan, leaving the chord the same. I'll throw some pics on the Laumer thread in the next few days. Anyway, sorry about your plane, but don't give up!

Chuck

(in reply to David Ingham)
       Post #: 737

RE: 1/2A trainer anyone? - 10/24/2007 7:20:18 AM   
David Ingham


 

Posts: 166
Joined: 8/22/2007
From: , CA, USA
Status: offline 		Thanks Tri-pacer, Most of the damage is at the 4th station where it becomes lighter. If I can get it straight, it should not be as bad as I thought. Will need refitting and recovering. The wing is ok.
The electrics are really about twice as heavy as the engine, and maybe I can find lighter batteries. I do sort of wish I had stuck to the original size.
I think for the same stiffness in flight and crash survivability (for given speed) the structural weight goes like the volume, so the bigger an airplane (or bird) is the higher the wing loading and the higher the stall speed. [Did anyone ever hear of a 747 surviving a crash like a Gwillows ROG?] It is a matter of compromising with the available radio equipment and finding a suitable power source.
For my Flea Whiz, when my son was young, I scaled it up by the square root of two and substituted an 049 for an 020. With no sub-induction and a muffler, it is very mild mannered, as I hoped it would be. But I don't think it would survive much of a crash, as the slab-winged trainers do.

(in reply to tri-pacer)