[Chris W]

Hi All,

this is my first RC scratch build in a good long while, (15+ years....)
i finally got the bug again and looking over all my stuff that i've collected over the years found these plans from an old MAN article. as luck would have it the author of the plans made his own electric version. (can be viewed here: http://www.rcgroups.com/forums/showthread.php?t=65703)

i decided to go electric after remembering the mess dealing with glow engines, and the fact that the apartment is small. besides if i can have a 'quiet' hobby the wife will be happier.

i made templates out of 1 mm plastic sheet, and proceeded to get the formers and the rest of the ply pieces are cut. (done last night) i'll be taking my time to build to get a nice and sound plane.

needless to say i've been out of the hobby for quite some time. my radios i have are antiques. no longer in the proper bands. and my knowledge of electrics is growing little by little but any and all help will be appreciated.

i will be using a cut down 3 blade 5x3p from cox (yup they still make the props) but have no idea on the power plant/battery/ESC combination.

i was looking at some e-flite motors (inrunner 400's or 380's) that had a nice power range but do not know how much they will push. (i think they were 4200kv and 3700kv respectively)

the plane should be somewhere in the neiborhood of 23-26 oz without radio or electronics. the wing loading on the plans state 17-19.

my only concerns are: making the duct & trimming the prop, but i do have an electronic copy of the original construction article from the author.

anyhoo as my first post hello to everyone.
-Chris

[cassat]

Hi Chris,

Sending you a pm.

[Chris W]

after doing a bit more reading i have some numbers to help with the motor decision.

the cox .049 motor had a rpm 20 000 ('when the temperamental motor worked just right' to quote Paul)

i think an outrunner may fit well but if i want to smooth out the shape (ie not make the motor mount ugly) i'll be using a insuinrunnerh a plug. either or i want to just figure out what i need for a motor / battery configuration.

Park 370 Brushless Inrunner Motor, 3600KV
Product Specifications
Type: Brushless
Size: Park 370
Voltage: 7.2 - 12
RPM/Volt (Kv): 3600
Continuous Current: 7A
Maximum Burst Current: 11A (15 sec)
Cells: 6-10 NiCd/NiMh or 2-3 LiPo 1200-1320mAh
Speed Control: 10 - 25 Amp Brushless

nice that they give an idea for the ESC and the batt pack.

is the higher value mAh battery packs be equivalant to having more of a gas tank?

now if i got all this new learnin' right. 3 cell LiPo is 12 volts (+/-) which will give in the neiborhood of 43000 rpm way too much jam. maybe using a couple of 2 cell battery packs in parallel should be 8 volts is 28000 rpm.

are these calculated values the 'top' of the throttle?


Six-Series Brushless 2000 kV Motor (28mm)
Product Specifications
Type: Brushless Inrunner
Size: 400 / 480 Upgrade
Voltage: 7.2 - 12
RPM/Volt (Kv): 2000
Continuous Current: 26A
Maximum Burst Current: 32A (15 sec)
Cells: -10 Ni-MH/Ni-Cd or 2-3S Li-Po
Speed Control: 35A -40A Brushless


Tech Notes

* Maximum Operating Temperature: 220 degrees Fahrenheit
* Adequate cooling is required for all motor operation at maximum current levels.
* Maximum Burst Current duration is 15 seconds. Adequate time between maximum burst intervals is required for proper cooling and to avoid overheating the motor.
* Maximum Burst Current rating is for 3D and limited motor run flights. Lack of proper throttle management may result in damage to the motor since excessive use of burst current may overheat the motor.

where as this motor would be where i want the rpms 24 k which would be about right at full trottle but no extra room for the oops need mthrottleed/power or ..... crash.

the tech notes talks about overheating, this plane is a pusher with little to no airflow over the electronics. .......

anyhoo sorry for the babble please feel free to ad any comments, especially if i'm going about this the wrong way.

thanks
-Chris

[cassat]

Chris ,

You should try and get a GWS ducted fan unit with multi blades. Noticeable for there orange plastic color and not too expensive.
Then, the 3600 kv inrunner motor would be about right and you can use the 11.1 V lipo battery.

[Chris W]

already tried that route

the duct on the fantrainer has a ID of 4 3/8" or roughly 113mm. the GWS fan i have on order from Great Hobbies is the 75 4 blade, it has an outer diameter of 86.4. no worries though i'll find a use for it

-Chris

[Chris W]

cut out the fuse sides from 3/32 balsa last night.

noticed a possible goof with one of the formers though. seems a notch is in the wrong location for where the tail hooks to the main fuse.

waiting paciently to assemble in due time. tax money will be invested into the powerplant. Great Hobbies has a good deal on spectruim radios but i should invest in a simulator to get up to speed again.

picked up a park flyer to get my skills back.

if i actually get anything worth looking at i'll start posting pics.

[Chris W]

Hey Cassat,

i tried sending a pm, but you inbox is full.

-Chris

[Chris W]

a small update:

added the support tri-stock and 1/8x1/4 strip to the fuse sides.

did many cuts into the tri-stock to make some sort of flexibility for when the formers are glued in. (any hints on getting the fuse to shape properly will be great)

i'm going to pick up a medium sized cork board to be able to hold the thing together while i assemble the fusealage. maybe even get a few pictures if i can get some decient batteries for the camera.

[cassat]

Yes Chris,

I did get all of your messages. Thank you.
Was lots of elephants in my box, trying to herd them out.
So we have to mail you duracells to get photos?

[Chris W]

lol
took one picture so far. the forward fuse is assembled and i've been gluing my fingers to sticks over the past couple days. the rear of the fuse is nicely in line but the front has a former that was slightly out...... makes it look a little odd but i hope it will fly true.

most all the parts are cut out. just got to cut out the elevator and assemble more. also have to build the duct, that is going to be the toughest thing to build.

i'll try to get the pics up to photobucket tonight, (i'll take a couple more as well.)