Astro Challenger (oz14610)


Astro Challenger (oz14610) by Bob Boucher 1985 - plan thumbnail

About this Plan

Astro Challenger. Radio control sport model. Wingspan 70 in, wing area 630 sq in, for electric power with Astro Cobalt 05 motor.

Note plan shows installation of both direct drive and geared motor.

Direct submission to Outerzone.

Update 9/6/2023: Added article, thanks to RFJ.

Quote: "A Nationals winner in electric competition! Astro Challenger, by Bob Boucher.

I began designing the Challenger right after our tenth annual Astro Championships in February 1984. At that contest Mike Regan amazed everybody with the fantastic climb of his electric Mirage sailplane. Mike used the new Astro Challenger Cobalt geared motor with seven Sanyo 800 mAh nicads. I figured that with a model designed especially for the geared motor, I would have an unbeatable combination for the Reno Nats.

Using my IBM computer program I tried various combinations of wing area, wingspan, and airfoil sections. For these calculations I assumed that the model would weigh 38 ounces complete with motor, battery, and radio. The actual model weighed 39 ounces. The computer said that the model with the best still air time after a one-minute motor run would have an Eppler 193 airfoil, a span of 6 feet, and a wing chord between 8 and 9 inches.

Using these parameters I began to lay out the model. I wanted to try a flat center section and an open frame wing for minimum weight and minimum work. In order to eliminate the requirement for washout to alleviate tip stall, I chose an elliptical planform for the wing tips. I matched this with an elliptical stab for a distinctive and pleasing appearance. This wing/ tail combination really works. The glide is superb and the model just won't tip stall. Another bonus of eliminating washout is that with the power on, the Challenger will fly inverted and do nice rudder rolls. The Eppler 193 is thick enough so that the MonoKoted wing is torsionally stiff to resist flutter, even in steep descents.

The power train consists of the Astro Cobalt 05 geared motor and seven Sanyo 800 mAh fast charge nicad cells. I chose the small Geist prop (13x7) and the Astro electronic switch. The total power system weighs 19.6 ounces. My model with radio weighed 19.9 ounces.

Using the computer simulation of the model glide polar combined with a simple model of the propeller characteristics, we can calculate expected climb altitude as a function of lift coefficient. Table 2 shows the results of these calculations and indicates that climb altitudes of almost 1,400 feet can be obtained with a one-minute motor run. Best altitudes are obtained when climb angle is held between 20° and 30°. From this altitude still air glide times of over 16 minutes can be expected.

Table 3 repeats the same computer simulation but with a direct-drive 8x4 propeller installed. The climb performance is a bit less dramatic, but nonetheless the Challenger can easily max in still air with a one-minute motor run.

CONSTRUCTION: The construction of the Challenger is straightforward. The wing and tail use conventional open frame construction. The wing has spar webs extending all the way to the wing tips for maximum strength. Both spars and the leading edge are bent backward to achieve the elliptical planform. I built the original wing dry, but if the bending of the spars and leading edde seems difficult, the wet the spars and leading edge, towel dry, and you should have no trouble bending them..."

Update 9/11/2023: Added kit review from Model Builder, February 1989, thanks to RFJ.

Supplementary file notes



Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction

Astro Challenger (oz14610) by Bob Boucher 1985 - model pic

  • (oz14610)
    Astro Challenger
    by Bob Boucher
    from Model Airplane News, Astro Flight
    June 1985 
    70in span
    Electric R/C
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 29/05/2023
    Filesize: 547KB
    Format: • PDFbitmap
    Credit*: theshadow
    Downloads: 805

Astro Challenger (oz14610) by Bob Boucher 1985 - pic 003.jpg
Astro Challenger (oz14610) by Bob Boucher 1985 - pic 004.jpg

Do you have a photo you'd like to submit for this page? Then email

User comments

I've been looking/waiting for this one to surface! My dad got into electrics (away from the icky gas engines and boat distractions) and this was one of the first planes he built (for electric). He got good at doing conversions for the guys in his clubs :D
des - 09/06/2023
Add a comment



Download File(s):
  • Astro Challenger (oz14610)
  • Plan File Filesize: 547KB Filename: Astro_Challenger_oz14610.pdf
  • Supplement Filesize: 3363KB Filename: Astro_Challenger_oz14610_article.pdf
  • Supplement Filesize: 3640KB Filename: Astro_Challenger_oz14610_review_MB.pdf
  • help with downloads


* Credit field

The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.


This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.


Terms of Use

© Outerzone, 2011-2024.

All content is free to download for personal use.

For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.

Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.