Skybench Big-Bird XL modified for ALES - RC Groups
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Nov 01, 2012, 02:03 AM
Registered User

Skybench Big-Bird XL modified for ALES

Flew for the first time today a Ray Hayes Skybench Big-Bird XL, in which I modified during the build into an ALES model. The conversion worked-out pretty well.

Power system is a Mega Motor 16/15/2 (4600kv) with a Maxx 4.28:1 gearbox, 13-8 Aeronaut CAM carbon prop, Hacker 40 amp ESC, running on a (2S) 1750mah TP 45C pack. Total weight RTF is 50oz.

The model makes 200m consistently between 26-28 seconds. Draws about 38 amps, for about a 280 watt deal (static on the bench). A climb to 200m uses in the range of 325mah, so multiple climbs with the 1750mah battery are possible.

Servos are in the fuse just behind the wing, and the power system, battery and all, are up front forward of the wing.

The model isn't going to win any world class competitions, but for my first entry into ALES, it's pretty cool.

(-: Dave Dahl
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Nov 01, 2012, 07:42 AM
Red Merle ALES VI
Curtis Suter's Avatar
Originally Posted by ddahl

The model isn't going to win any world class competitions, but for my first entry into ALES, it's pretty cool.

(-: Dave Dahl

Practice, practice and practice till you know this plane better than the back of your hand and you'll be amazed how competitive you can be with it! Of course you know that.

Nice work!
Nov 01, 2012, 12:49 PM
Registered User
ozmo01's Avatar

Wing pics???

Did you add flaps or anything to your wings?
My BBXL is on the fix list after a winch mishap (leadfoot syndrome mixed with not enough toss)
It could end up being an ALES bird too.
Last edited by ozmo01; Nov 01, 2012 at 12:54 PM.
Nov 01, 2012, 03:17 PM
Registered User
The wings on this model are from a previously built winch launch Big-Bird XL RES (still fully flyable and in good health)

But I'm not sure if that model it will get flown much anymore

The wings that came with the modified fuselage, are in the process of being constructed with flaps.

(-: Dave
Nov 01, 2012, 03:25 PM
Gasbags & Gussets
jswain's Avatar

photo ?

Hi Dave.
Thank you for the specifics on the motor/prop/electrics.

When you get a chance could post a picture(s) of the power components setup?
I ask because as soon as i start sticking stuff into the nose i suddenly run out of space whereas the other guy said it would all fit with room to spare

Also what about ventilation for the heat......

thanks in advance,
string-launch BBXL owner john s

Last edited by jswain; Nov 01, 2012 at 03:36 PM. Reason: ask about venelation
Nov 01, 2012, 05:08 PM
Registered User
@ jswain,

In photo one, I placed on the nose some blue tape with a black line on it. The black line indicates the rear location of the motor/gearbox combination. The 2S battery pack is located in its relative position when it's inside the fuse.

Photo two shows the inside of the fuse without the battery installed, and you can see the ESC to the rear of the motor and on the floor of the fuse.

Photo three shows the battery installed, which sits on top of the ESC.

Photo four shows the underside of the fuse. I originally though I'd have to place the battery somewhere along the CG, so I made the bottom of the fuse removable to facilitate battery mounting. As you know from building one, the hatch is originally on the top. But I needed to avoid the wing rod (I thought), while getting batteries in and out, so I went through the bottom. Either way (top or bottom), you still need access to the inside, so no harm no foul.

The servos are mounted under a hatch just aft of the rear wing saddle bulkhead. You could probably get by with mounting them in front of the wing saddle's rear bulkhead, and still have the CG work out. Thus, deleting the second hatch.

Ventilation? None. The system doesn't produce enough heat in 30 seconds to matter much, and the heat dissipates during the glide. When back on the ground after a 10 minute flight, the battery and motor are practically ambient again.

Hope this helps,

(-: Dave
Nov 01, 2012, 08:06 PM
Gasbags & Gussets
jswain's Avatar

thank you Dave

Thank you Dave.
Great craftsmanship and i am glad of your success so far.
This is great nuts+bolts type info and will be a resource i can use in the future for another BB build.
Using the 2s really makes a difference in the real-estate department vs. trying to shoe horn in a 3s.

I set mine up (1980s R/E/Motor design)but it was tight so i was curious about your setup. I am going for the lightest weight for my Ultra MkIV and it looks like it will be a flying around 26~27oz for a 85" model.
That said, It took me about a week to figure out the darn arrangement....

best wishes and thanks again, john s.
Last edited by jswain; Nov 02, 2012 at 12:23 AM.

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