DECATHLON House of Balsa SchoolYard scale - RC Groups
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Jul 05, 2005, 05:32 PM
Space Coast USA
hoppy's Avatar

DECATHLON House of Balsa SchoolYard scale

This is a very nice kit from House of Balsa. It's the Decathlon, Kit K-21, school yard scale for .061 engines. It was a no brainer conversion to electric with the Hacker A20-20L going on the firewall and the battery going in the fuselage above the LG. With a Tronics 3s1800Lipo, the AUW was 20oz. It flies well at 1/2 throttle and will do all basic aerobatics including knife edges.
The list price is $59 but by shopping around, I found one for $39.

I didn't make any attempt to lighten the plane. The body is solid balsa sheeting as are the tail surfaces and the ailerons.
Last edited by hoppy; Jul 05, 2005 at 07:34 PM.
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Jul 05, 2005, 10:51 PM
Registered User
Matt D.'s Avatar
Nice job!
Jul 07, 2005, 11:46 PM
Space Coast USA
hoppy's Avatar
Thanks Matt, I owe it all to the kit

Should have mentioned that it probably is for an intermediate or better flyer as it can be quite a bit faster than the usual foam floater. The ailerons are large and roll it quite nicely. The Hacker A20-20L provides about 10oz of thrust over the AUW so you know it will get up and boogie.

On the motor mount...the firewall was simply moved to the very front of the nose and the motor screwed to the back of the firewall. Neat and simple.
Jul 08, 2005, 11:28 AM
Registered User
BuzzBomber's Avatar
Hoppy, that looks REALLY nice! Love the covering! I've got the Laser stick from the chea-pass series myself; just started putting it together last weekend, and have one wing panel done and the other dry fit with about 1 hour time on the project so far. These kits are amazingly simple to build, eh? Mine is going to be motivated by an ancient Enya .15 (or an OS .10, haven't made up my mind), but I must admit, I did think of E-conversion. Be sure to some back with a flight report!
Jul 08, 2005, 11:36 AM
Suspended Account
Wow the AUW is 20OZ!!!!! Very Light for a 47" wing span. I'm building a HOB Acro Cub now and have a HOB Space Walker on order. Im liking these HOB Kits
Last edited by fly4fun; Jul 08, 2005 at 03:14 PM.
Jul 08, 2005, 03:03 PM
Space Coast USA
hoppy's Avatar
And it comes with all the hardware! Those modelers that have been only on the electric side probably won't recognize the's heavy duty.

By cutting holes in the body and tail surfaces, using light weight hardware, and reducing the amount of plywood doublers, several or more ounces could probably be shaved off. I put the Rx and servos as far forward as possible as I thought the cg might be hard to adjust otherwise. As it turns out, things would have worked out better if I had mounted them as far back as possible. The way it is now, i had to mount the battery over the LG....otherwise it probably would have fit in nicely entirely in front of the gear. No problem, it all worked out OK.
Jul 08, 2005, 03:15 PM
Suspended Account
Sounds good Hoppy.
Dec 07, 2012, 05:00 PM
Registered User
Mine weighs 31 oz now.
Last edited by Dave180; Jan 27, 2014 at 09:20 PM.
Dec 07, 2012, 05:19 PM
I just want to go fly!
walter3rd's Avatar
nice belly skid!
Dec 09, 2012, 05:47 PM
Registered User
Dec 11, 2012, 01:39 AM
Registered User
Video of landing skid:
Last edited by Dave180; Dec 11, 2012 at 01:51 AM.
Jan 23, 2014, 04:57 PM
Registered User
I'm still flying mine. Its down to 31oz now after a calibration error on my scale.

Super Decathon rc motor test (6 min 42 sec)
Last edited by Dave180; Feb 10, 2014 at 11:27 AM.
Jan 23, 2014, 09:24 PM
Registered User
Hard ton see much of anything.. Ccaisionaly a red speck and mostly scenery.
33 ! ounces.. How was that managed?? that's a 10/11 oz airframe with wheels.
Typically HOB kits are a bit overdesigned /heavy but 33 oz is a bit Much.
22 ounces for avionics? Are you using a Speed 600 and 8 2400 nicads?
Note that It's designed for Norvel 061 which is "perhaps' a 90/100 watt motor.
Usually a 5 to 7 ounce electric power avionics package.. and that's using medium size bits
Jan 23, 2014, 11:50 PM
Registered User
Did you watch the ending? You can see the plane there. Ha Ha. The cg on that plane is kind of forward. I had to add like 2.5 oz of lead up front when I changed to the brushless motor plus I run a receiver battery which is 1.6 oz; so thats 4.1 oz extra. No big deal. Its got plenty of wing. It can fly really slow if you trim it right.
Jan 24, 2014, 01:46 AM
Registered User
I rechecked the weight. It's up to 15oz empty now after some upgrades. I just finished a smaller plane then this and it ended up at 13oz empty.

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