Astro 05 & Large(ish) AP Plane? - RC Groups
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Jun 23, 2004, 03:33 PM
Grizzled Member
Jim Robinson's Avatar

Astro 05 & Large(ish) AP Plane?

Hello all,

I am just starting to get back into R/C after being absent for about 2 yrs. I've got a lot of glow experience, but the extent of my electric knowledge consists of a little time spent with a Lite-Stick, and a scratch built "Tiny" using the GWS IPS motor. I experimented a little with NiMH packs on the Tiny and tweaked a few props and actually got it to fly really good (until I whacked a tree with it). Beyond that I'm pretty green in the electrics area.

What I want to do is build an AP plane out of some (good) junk I have laying around. I have a wing and an Astro 05 direct drive motor that I believe will work together. Picked up the wing at a swap meet a while back for $5 bucks. Very nicely built, flat bottomed airfoil, it looks like it might be for a 2 meter sport/training type of sailplane (Wanderer 72 would be my best guess, but there probably haven't been any of those around for 10 yrs). The motor was installed in some sort of high-wing trainer that I traded straight across for a new Lite-Stick kit. It's a 7-turn motor, from what I've gleaned from the forum. No batteries, speed control, or anything else.

The wing specs:
Span: 72"
Chord: 10"
Area: 640 sq. in. (taking the tapered tips into account)
Weight: 9.8 oz.

Planning to build something similar to the EZ400 G, but of course slightly bigger. Tenatively planning on using a Fuji A210 camera (6.2 0z. without batt) and I'd also like to be able to fly a GPS (5.7 oz. rtf), and eventually a downlink system at the same time.

My questions are:

1. Am I even in the ballpark with this combo?

2. Which gearbox should I use? I'm thinking the Astro Flight "super box" for maximum gear reduction? Are there other options for gearing this motor other than Astro Flight? It wouldn't work on a plane this size without gearing, would it?

3. What are my options for batteries? I know less than nothing about the LiPos, but is there a LiPo setup big enough nowdays to work here? What about NiMH? I've got everything I need to charge NiCd or NiMH, maybe I should just go that route?

4. What do I need for a speed control? I'd like to leave myself open to the option of powering the camera, downlink, & GPS with the flight pack someday, if possible, but maybe I should bypass the speed control BEC here and just build an IC voltage regulator and go straight to the battery with it, since both the camera and the GPS operate at 3 V.

There's about a million other questions I have too, but let's start with that. Here's a couple pics just for grins.

(the aluminum tube is what I plan on using for a "fuselage", peppered full of lightening holes)

Really appreciate any input you guys can give me. Thanks,

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Jun 23, 2004, 08:20 PM
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Sabrejock's Avatar
Jim, the Astro 7 turn 05 with a "Superbox" (3.69:1) and 10 cells will amaze you. You could look at 400 watts in and very high efficiency in this application. Go with the GP 3300 cells with something like a 15x8 APCe and you will have a great camera plane as well as a good sport flier. I'm using this settup and a 3 blade 14x9 drawing 40A hot off charge. Tex.
Last edited by Sabrejock; Jun 23, 2004 at 08:26 PM.
Jun 23, 2004, 08:35 PM
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vintage1's Avatar
...but not in a 9.8 oz airframe...
Jun 24, 2004, 12:05 AM
Grizzled Member
Jim Robinson's Avatar
Thanks, Sabrejock. I noticed when I was searching the forums for info on the Astro 05, your name came up in almost every search. You must be a diehard Astro man! I was hoping you would see this thread.

To show you how out of touch I am with this stuff, what are GP 3300s? Obviously they are 3300 mAh cells, but what's the "GP" mean? NiCd? NiMH? How much does a pack like that weigh?

The 9.8 oz. is for the wing alone. I've done a very rough estimate of the AUW w/camera & GPS and found it to be 64.5 oz., or just a shade over 4 lbs. That puts me at a wing loading of 14.5 oz./sq. ft. loaded, 11.8 empty. I am using some old sub C (I think) NiCds for my battery weight (10 cells=18.9 oz.), and just really hoping that Sabrejock will come back and tell me that his pack weighs about half that much . As I said, this is a very rough estimate as I am still weighing and choosing components and guessing at most of the weights.

Thanks for your replies guys,
Jun 24, 2004, 03:39 AM
Registered User
Tomahawk's Avatar
GP (Gold Peak) is just the brand name like "Sanyo"
They are Nimh cells and about the best you can get right now in the large nimh mah size. A 10 cell pack of these cells will weigh around 22ozs.

Jun 24, 2004, 05:48 AM
Registered User
vintage1's Avatar
Ok, that all comes up sensible then. Definitely geared, definitely 10 cells unless you fork out for 3s LIPO pack and save about half a pound weight...

The motor will easily do 250W, and for a camera platform at 50W/lb thats 5lb.

I will watch this closely because I have one of those motors, and this is one option of the sort of plane it will (eventually) end up in..
Jun 24, 2004, 12:43 PM
Registered User
Sabrejock's Avatar
Jim, If you're concerned with weight you could consider Sanyo 1950 FAUP cells. They're 'A' size and 10 will weigh 14oz vs 22oz for the 3300's. Plus wiring and assembly. The 1950 pack will provide almost the same power under load. By comparison on the same application, my 10x3300's puke out 40A and my 10x1950 will provide 35A. A diff of about 50W, but then the lighter load requires less so it's probably a wash. Tex.
Jun 24, 2004, 05:45 PM
Grizzled Member
Jim Robinson's Avatar
Thanks for the input here, guys, really appreciate it. I think I'm up to speed on the GP 3300 cells, now. I think in the interest of saving weight, it might be best to go with the Sanyo 1920s instead, at least for use while the acft is loaded with the camera. Maybe I'll pick up a set of the GP 3300s also, for use when I'm not flying the camera.

Sorry, more questions: Where is a good place to buy these batteries? The "Tower Hobbies" of NiMH cells is what I'm looking for, where are they cheapest? Also, what would everybody recommend I purchase for an ESC?

I did a little experimenting with a 6" piece of the aluminum tubing I am planning to use for a fuselage and was pleasantly surprised to find that I can reduce it's weight by over 50% by drilling it full of 3/8" holes. Besides that, it looks really cool! The 6" sample went from 30 gm. without holes, down to 22 gm. with 1/4" holes, and finally down to 14 gm. using 3/8" holes. I'm not sure if I like the looks of the tube with the 3/8" holes; looks like it's been weakened quite a bit. It's deceptive though, as I am unable to bend, collapse, or deform the sample in any way with my bare hands (and I am a 260 lb. bruiser ) Think I may split the difference when it comes time to lighten the actual fuse/boom, and go with 5/16 holes for appearance reasons if nothing else. Here's a pic of the sample with 3/8" holes, what do you think?

Thanks again,

Jun 24, 2004, 07:03 PM
Registered User
vintage1's Avatar
I think Aluminim has entirely the wrong properties for a model plane structural member - sorry!

The best is undoubtedly carbon fibre, with tradiotional wood - balsa frame or rolled ply - coming in very well too, especially skinned with glass cloth.

The experts in high strength low weigh structures are to be found in the builders forum. And probably in the new composites forum, tho I haven't bothered to lurk there.
Jun 24, 2004, 07:20 PM
Registered User
i was lucky enough to get a wing similar to the one shown (2 meter) and a friend of mine donated a carbon fibre or graphite golf club shaft and designed some tail feathers for me based on the wing area, etc.
i then built a pod to house the electronics and the plane handles beautifully.
if you are interested i can take a picture of the finished product and provide some construction details.
Jun 24, 2004, 08:07 PM
Grizzled Member
Jim Robinson's Avatar
As you stated Vintage, this isn't the correct forum for this, but as long as we're on the subject, what dia/wall thickness CF tube would be adequate to function as a fuselage/tailboom for a bird of this size? I have no idea.

I looked at some CF a bit ago, and a 1/2" dia. x .032" WT was about $35! I don't even know if that would be rigid enough for the job, maybe I need something even bigger. The ironic thing is that the vendor didn't bother to list the weights of his CF tubes, which I found a bit peculiar since the whole push behind CF is it's strength to weight ratio. I have nothing to compare my aluminum tube to as a result. Where can I find weights for specific CF tube sizes?

I'm not really interested in building an expensive, high performance, sport acft. here (I have dozens of those), using all the exotic materials I can find. All it needs to do is carry the camera to altitude for photos and return it safely to earth afterwards. In terms of weight vs. cost, I could delete the electric power and install a small glow engine and make up for 10 feet of that aluminum tube for not much more than the price of the CF. On the other hand, I'm not interested in building an acft that will barely sustain flight because of it's weight either. Maybe I just need someone to show me where to buy CF .

By all means, post some pics. I'd be delighted to see what you came up with! Wish I knew someone who plays golf...

Jun 24, 2004, 09:26 PM
Registered User
vintage1's Avatar
Oh, do you know, I'd get some 1/64" ply, and rollit round a plastic rod and glue it.

If it felt flimsy, I'd roll another layer on top

Then make a 1/32" ply box with basla formers to hold the bits in, and some kind of motor mount and thats about it.

No need to even paint it really. French polish maybe
Jun 24, 2004, 09:44 PM
Grizzled Member
Jim Robinson's Avatar
Hmmm... That would look really nice stained & clear-coated, now wouldn't it...