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Old Jun 28, 2009, 12:18 AM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
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Build Log
Hobby king's Decathlon EP ARF, 49in. span.

Hey folks, how we doin?
Well, im doin great. I bough this finely done balsa ARF of the Decathlon from Hobby King. Was a great price of only $67.83, no electronics or motor.
The pkg arrived in about 10 days at regular shipping, and intact with no damage other than a wing retaining tab that had got knocked back into the wing just inside the root rib. I fished it out, and cut an access hole in wing bottom to re-install it as it had to be put in from the inside, it has ears that prevent it from being pulled out and cannot therefore be installed any other way. No biggie, was easily fixed and the square access I cut out simply was glued back in place.


Unpacking everything.


Note that the side windows are covered, and also they didnt provide any clear lexan to make any windows, kinda strange but also no biggie. I cut the covering from the openings and installed some windows later in the assembly.
The control surfaces have CA hinges, and must be CA'd by the user. This is as any ARF of this type, and is a very simple process as most of you know.



Now for the tail feathers. Do not do as the manual says.
It has you CA'ing the elevator to the stab before attaching it all to the tail of the fuselage. If you do this, you'll have to then cut the material at the very tail of the slot in order to install.
What I did was to slide the stationary prortion of the stab into the slot from the side, than place the elevator joiner in behind it. Glue the stab in place, and then carefully get the elevator glued to the joiner rod, and sliding the hinges in place at the same time. Then once the epoxy bonding the joiner rod to the elevator halves is set, then adust elevator position for end clearance, and snug to the stab and then CA the hinges.
Sationary portion, with elevator joiner rod loosely in place.


CA'ing the stab to fuse with Thin CA after placing it in and adjusting it's position to be centered properly. The bottle in the pic is some old medium CA that went bad, just used it for the pic so I wouldnt be having glue running out all over taking this shot. Use "Thin" CA for this.


Finished horizontal stab/elevator.


Next step of course is setting the vertcal satb into it's slot in the block on top, and thin CA'ing just like the horizontal was done.
Then do the rudder in similar fashion as the elevator, sliding the rudder and hinges into place, adjusting it's position & clearance and then CA the hinges.

Ok, now for the tailwheel assy. I didnt like the one supplied as it's the type that is directly and permanently attached to the rudder having a rod glued right into the rudder.
So I took a Dubro tailwheel assy w/ tiller arm and installed it with the tiller arm inline with the rudder. Then I took a short length of 1/8 fuel tubing and slid it over the arm, and then trapped it along the rudder's bottom edge with, a plastic bracket that was salvage from my AT Decathlon that suffered a paower failure and crashed a few weeks ago. Ironic that it's serving the same purpose as it did on the AT Decathlon.


Next up was the main landing gear struts, and they simply are bolted to a 1/4in thick plywood plate that has the blind nuts already in place.


I also used a set of Dubro 2-1/4" superlight wheels in lieu of the supplied ones. Reason being that I'll be operating off a grass RWY at the club field.
Could even go larger if you wish to 2-1/2", or even 3" if ya wanted to make her a tundra version. I also decided to leave the pants off, also for grass operational purposes. And besides I didnt like the look of the "half pants" that were supplied. I may later on aquire some better ones.
Used 6-32 hex cap bolts & nylock nuts for the axles, as the supplied ones were'nt big enough for the Dubro wheel hubs.



Well thats enough for now, as im worn out from the day's flying, and the Decathlon was maidened today also.
I'll post the rest forthcoming, and hopefully somebody will be availble to video the next flight.(Everybody was busy with something when my flight window came up.)
Ok, so see ya's later, be back to finish up.
Thanks for reading, and happy flying.

Chuck.
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Old Jun 28, 2009, 01:38 AM
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Hi chuck,

i own the same decathlon. The Red Version. Not from Hobbyking but from a german importer. Same chinese manufacturer.
Mine had side windows in the box and the cover was cutted out maybe they had no time to pack yours complete
I had to re-iron the cover one time beacuse of many wrinkles.

Beware of the landing gear ! it is made from very soft alloy. You should land it very very soft
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Old Jun 28, 2009, 01:57 AM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
Joined Jan 2006
3,325 Posts
Yes I saw that one, I was searching out the mfr myself and came up with this.:
http://www.yhmodels.com/big_.asp?pid=308&pmodel=YH142

I thought it strange that the Hobby King one, obviously manufactred by the same wouldnt have the side windows as the red version does. I see that the red one has the better wheel pants too. Must be the way they got it down cheaper for HK.

Yeah, dang me........I didnt include a link to the plane in the first post sorry.
Here is HK's
http://www.hobbycity.com/hobbycity/s..._48.9_inch_ARF

I powered this one with what I had on hand, which is an E-flight Park450 and an E-flight 25a pro ESC. I do need to go to a much higher C rating on the battery though, and more Mah. Yeah, it was a might too warm at the end of only a four min. flight, and a lightly flown one at that. Should prop down a tad too, was swinging an APC 11x4.7 SF.
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Old Jun 28, 2009, 04:06 AM
Why am I addicted!!!
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United States, IL, Columbia
Joined Jan 2008
561 Posts
So, how would you rate the plane flying? Do you have any videos? Great pictures and information. Keep it coming I think I am going to go for it soon. I heard you can cut out the sides and use the same gloss writing paper that they used back in my college days for overhead projectors. Cheers
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Old Jun 28, 2009, 05:34 AM
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ahm Park450
My Setup is Turnigy 3542-1000 with 11x6 APC-E, at 48A. Battery 3S 3600mAh.
With that it goes really "scale". Not endless vertikal, but nearly 70-75 for a few seconds, and powerful dynamic aerobatic figures .

Wish you good luck for the maiden !
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Old Aug 18, 2009, 10:39 AM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
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Ok sorry I left this thread alone so long, but I been busy. Yes I do have a video now, and she's been up for 9 flights now and am still feeling out the plane and prop sizes trying to find the one that it's happiest with.
Im flying her on a Park 480 now, and have tried everything from a 10x4.7 to an 11x4.7 and this flight was with an APC 10x7 SF.
Please exuse the camera operator's shakeyness and losing foucus every now and then, he's only 14 I think and I bit inexperienced. But he was the only one who offered, and I appriciate him doing so.
Hobby King's Decathlon EP (5 min 51 sec)


I got some 2200 mah batteries coming, these 1500's aint cutting it, flights cant be more than 7min. on them.
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Old Aug 20, 2009, 02:52 PM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
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I though I might throw in a few pics of my motor mounting and ESC placement. A couple guys at HK's forum had asked for that too.

So yes even though the Park 450 did just fine except for getting a little too hot, I did go ahead and get the 480 and mounted it in, and also even though the 25a pro ESC did the job, it was barely within the amp draw range so I also got the 40a pro ESC and installed it in place of the 25a one. Heh, the 40a one is quite a bit larger, so it's present location will likely be changed when I fit the 2200mah battery when they arrive, but it may not need to be just have to see.
Anyway, here are some pics of the 480 and 40a esc mounted in.






Cowl clearance is just right using the set screw type prop adapter. Collet type wouldnt work as it couldnt get ahold of enough of the shaft to be past the flat. I also had to make use of a flat washer between the adapter's prop seat, and the Dubro 1.5" spinner backplate so that the spinner didnt contact the cowl. Without the spinner though and just using the adapter's spinner-nut the flat washer wasnt needed.
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Old Aug 20, 2009, 05:21 PM
anything Yak
Joined May 2007
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Just out of curiosity, can't the cowl be shortened to accomodate for the short motor shaft when the motor is inside the mount?
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Old Aug 20, 2009, 05:52 PM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
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Well no, its shape and upward slope on the bottom only allows it to slip on the fuse just so far, about 1/4 inch and you need that to attach it with the four screws. It cant go on further, even if you did shorten it. Its not it's length, its the shape.

But mine came out fine with only a flat washer needed to put the spinner backplate far enough that it doesnt contact the cowl behind it. But as I say, its all pretty close. And it works fine, and looks great to me. Now of course I didnt have to use the dubro spinner, I could just put the adapter's spinner nut on with out it and the flat washer isnt required. BTW, well maybe I should take another picture to show this and I will later but im using both the prop adapter, it's spnner nut, and Dubro spinner together.
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Old Aug 20, 2009, 05:58 PM
anything Yak
Joined May 2007
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Thx Sabrehawk, that picture clears it up. I noticed most users were using the 35 size Turnigy's and someone flipped the motor outside of a shortened motor cage. I plan to mount the motor inside as you did on your 480.

Thx. btw. the spinner and your setup looks very sharp!
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Old Aug 20, 2009, 06:17 PM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
Joined Jan 2006
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Yes and it seems logical to think that some other motors of different brands may have longer shafts than the Eflite units. Or they may have longer ones availible(yeah that would be nice).
But as I have said, im happy with my arragement and its working very well, and as you said looks sharp. I though it looked quite strange with only the Eflite adapter, even though that works just fine. Me I had to have it scale.
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Old Aug 20, 2009, 06:48 PM
anything Yak
Joined May 2007
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Just for comparison,

Here's the specs of the Hobbyzone Super Cub LP.

Wingspan:*47.7 in (1200mm)
Overall Length:*32.5 in (825mm)
Flying Weight:*25.2 oz (715 g)
Motor Size:*480 brushed
Prop Size:*9 x 6
Recommended Battery:*3S 11.1V 1300 Li-Po (included)

And the Decathlon:
Wingspan : 48.9in
Length : 33.2in
Wing Area :*366 sq. in
Suggested Prop: 10x6~11x6*
Weight (without motor/battery etc.): 25.4

Size wise the Decathlon is very similar.

It would be great to be able to fly the Decathlon in the same fashion as the Super Cub, nice and slow.

With a 3S 1320mAh lipo, 2oz brushless motor, TB-18 ESC, and propped for 100-150W, it would be in the range of 30oz AUW.
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Old Aug 21, 2009, 10:40 PM
anything Yak
Joined May 2007
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Sabrehawk,

Try giving the APC 10x7E a shot, not the SF version. I think the pitch speed on the 11x4.7SF may be too low. It'll still give you enough thrust for loops, etc. I got a 17mph stall speed for the Decathlon. The SF may only be giving you a 29mph pitch speed.

With 2200 lipos, you'll be seeing a 52mph pitch speed and ~1:1 thrust.
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Old Aug 22, 2009, 05:30 PM
Off we go.............
SabreHawk's Avatar
Seattle, WA. USA
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Funny you mention it, I was thinking of trying an E prop, and have a 10x7 one on hand. But it's hub is much thicker than that of the SF prop and would prevent the use of the Dubro spinner. There's just good enough propshaft left after the spinner backplate, and the prop for the adapter's nut to get on as it is, any thicker prop hub and its not enough.
So I think I'll stay with the SF for now and it's flying at just what speed I want for a scale looking flight.
Right now im busy taking a day off from flying to work on the graphics change I also wanted to do but was putting off.

So, hahh, well I spent the entire morning painstakingly laying out and cutting the graphics trim material I bought to do this with. (Top Flite trim sheet, in black). Got them all cut and was ready to start applying them.


I laid the first strake down and was testing out how I'll proceed and from which end, when I noticed one star's tip had come loose and sticking up. And thats where I saw what I wished I'd saw before I did all that painstaking work. Yup, that white was not bordered with pinstripe as I had thought, but was applied over a pattern entirely black.
Well, the picture says it.


Now all I have to do is get under one corner and gently peel away the white portion leaving the black. So, thats what im about to do. Will post pics of the final look in a bit. But I am going to use what I did make to cut extensions to take the strakes all the way to the trailing edge like they should be.

Edit: Ok now she looks right. Much more striking this way.(now to clean up my mess!)




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Old Sep 01, 2009, 03:48 AM
anything Yak
Joined May 2007
444 Posts
I just received my Decathlon today. What a beauty!

It didn't come w/ directions, but it looks to be an easy build.

The little Hyperion 2213-24 looks pretty small in there, but it should fly her like a stock hobbyzone supercub, which is what I'm after. Setup will be an APC 10x7 or GWS 11x7HD, TP1320, Thunderbird-18.

Here's some pics.
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