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Oct 07, 2003, 07:10 AM
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Fai15 cobalt motor with gbox

I have a surplus FAI 15 with gearbox that comes out of a glider that I am thinking of putting into a VMAR arf PC 9 made for a .47 glow motor. I am wondering if this would be a suitable powerplant as both are just lying around. If not, can someone suggest another suitable scale type aircraft that the motor would be good for or alternatively give me some guidelines as to the limits of the motor so that I could match it to an aircraft - ie what type/size of plane will it fly?
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Oct 07, 2003, 10:18 AM
Registered User
Mark: is this an Astro cobalt and what gear ratio/prop are you going to use?

Typically the Astro cobalt 25 geared (14-16 cell) is reccomended with 40 sized planes.

Oct 07, 2003, 10:45 AM
AKA BillyKillaWatt
Billy Haynes's Avatar
I have a FAI 15 w/std g.b. on my Morris Hobbies Pen Knife. I'm thinking about go'n the opposite direction,... take it off the Knife & put it on a I don't think it would be suitable unless it's a very light .40 size plane. here's my Knife--> W.S.36", W.A.500sq", Weight w/o motor & batt 28 oz's, std ratio (2.38 i think) 10c 4/5aup, 13x7 apc e, 'round 42A wot. This setup fly's the plane nice, @ 1st of flight it has alittle more than 1:1. With the 4/5 aup's (used for lightweight) run time is only 5 min w/throttle useage, granted throttle hardly ever below 1/2, usually around 3/4, using 100% for hover, loops, ect. Temp has never been a prob with motor or pack, mounted outside of a profile fuse. If you weren't looking for aerobatics, just poking around in circles, I think that motor would fly a plane nice, w/ say 50-60 " w.s.-flat or simisym. airfoil, if weight is kept below say... 60-70oz's AUW. This is just my opinion with the experience I've had with mine.........
Oct 08, 2003, 08:19 AM
Thread OP
yes, astro cobalt, standard gbox i think its 2.38:1, prop i cant remember what's on it suffice to say that i'll use whatever works except that i've heard it shouldn't pull more than 40 A
Oct 08, 2003, 08:22 AM
Thread OP
Billy Haynes,
Thanks for your comments, they are useful. It looks like its destined for another plane, something smaller and lighter.
Oct 08, 2003, 08:28 AM
AKA BillyKillaWatt
Billy Haynes's Avatar
" i'll use whatever works except that i've heard it shouldn't pull more than 40 A""
'round 40a continuous, but a FAI motors can handle alot of amps for short burst...... thats what everyone's told me...

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