LARS (oz5425)

 

LARS (oz5425) by Dick Sarpolus from Flying Models 1976 - plan thumbnail

About this Plan

LARS. Low Aspect Ratio Sailplane. Radio control ailplane.

Quote: "LARS, by Dick Sarpolus.

The name 'LARS' stands for Low Aspect Ratio Sailplane. The first question usually asked about this model is - why did you use a low aspect ratio wing on a thermal soarer when everyone knows high aspect ratio wings are more efficient, therefore better?

That's why we designed and built it - we weren't convinced that high aspect ratio wings really were better for our size aircraft. It is true that most R/C sailplanes use high aspect ratio wing designs; usually limited only by structural considerations. These long, slender wings even seem to 'look right' when the sailplanes are circling gracefully in the thermals, beneath the clouds. Full scale sailplanes incorporate even higher aspect ratios than our models can duplicate. Lower ratios are used on slope soarers, racers, pattern aircraft, etc. So why try a thermal soarer with a low aspect ratio wing?

If it would work, such a plane could have several advantages over conventional sailplanes: The wing, having a shorter span, would be stronger and able to withstand heavy winch launches and higher winds. The model would be easier to transport with shorter, wider wing panels. A large amount of wing area could be used in a short span for lighter wing loading and hopefully better performance. We had been successful R/C soarers with lower than usual aspect ratios, and Free-Flight models tend to have lower aspect ratio wings. A friend of ours argued convincingly for low aspect ratios, drawing on his experience with hand launched glider design. The potential benefits seemed to justify an attempt at a low aspect ratio design.

We laid out a six foot span wing, to use standard 36 in balsa. Polyhedral was used for better turning capability with 24 in center panels and 12 in tip panels. The center panels have a 15 in chord with tip panels tapering to 10 in. Figuring on a 75 in span (including fuselage width as is normally done) wing area is 1065 square inches. Aspect ratio, span squared divided by area, is 5.3 to 1. This seemed like a good place to start; anything lower appeared impractical for stability considerations. The airfoil drawn up was a flat bottom, 10% thick section.

Wing construction is conventional built up practice; spruce spars, vertical grain spar webbing, planked leading and trailing edges, capstrips. Wings have tubes in the center-section to slide on a 1/4 in dia steel rod built into the fuselage.

Horizontal stabilizer area is 230 square inches, 22% of the wing area. Vertical fin/ rudder area is 90 square inches, 8.5% of the wing area. A fibreglass fuselage was used as we had access to a basic fuselage that could be easily modified to our desired configuration. The tail surfaces are simple structures; the tail assembly attaches to the fuselage with two nylon bolts..."

Direct submission to Outerzone.

Update 09/05/2016: article pages, text & pics added, thanks to RFJ.

Supplementary file notes

Article.

Corrections?

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

LARS (oz5425) by Dick Sarpolus from Flying Models 1976 - model pic

Datafile:
  • (oz5425)
    LARS
    by Dick Sarpolus
    from Flying Models
    July 1976 
    75in span
    Glider R/C
    all formers complete :)
    got article :)
  • Submitted: 19/03/2014
    Filesize: 616KB
    Format: • PDFbitmap
    Credit*: JJ

LARS (oz5425) by Dick Sarpolus from Flying Models 1976 - pic 003.jpg
003.jpg
LARS (oz5425) by Dick Sarpolus from Flying Models 1976 - pic 004.jpg
004.jpg
LARS (oz5425) by Dick Sarpolus from Flying Models 1976 - pic 005.jpg
005.jpg

Do you have a photo you'd like to submit for this page? Then email admin@outerzone.co.uk

User comments

No comments yet for this plan. Got something to say about this one?
Add a comment

 

 
 

Download File(s):
 

Notes

* 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.

Scaling

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, 2011-2020.

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.