Tern (oz7694)

 

Tern (oz7694) by Brian Springall 1986 - plan thumbnail

About this Plan

Tern. Radio control sport model for miniature 2 function RC and 0.5cc engines. This is a high wing design, but the plan also includes a 2nd sheet showing alternate fuselage layout with low-wing and an open cockpit.

Quote: "THIS IS THE LATEST design in a series in which the requirement was for a small model with a low capacity motor that could be flown in a small field. An 0.5 cu in engine, the Allbon Dart, was chosen in preference to a small glow motor for the following reasons:

1. Ease in operation (no glow battery required).
2. Very low noise levels compared with high revving glows.
3. It will turn a fairly large prop, which gives a better performance at low airspeeds.
4. Finally, the Dart is the best little IC motor I have ever owned, and seems to go on forever.

The disadvantages are:

1. They are messy, so a well sealed model is needed.
2. Power output is lower than an equivalent glow motor.

These shortcomings are easily remedied, however: the answer to 1 is to cover model with film and for 2, to build light.

Before constructing the Tern, I experimented with a number of small models using aileron elevator controls. A variety of wing sections were tried, with thickness ranging from 10 - 22% symmetrical. They all flew fairly well but the aileron response left as lot to be desired. At low speeds or on fast turns funny things started to happen, eg tip stalls. At high speeds powered with glows they worked but it was not what I was looking for.

About this time, I was looking for a model that would fit into a box on the back of a motor hike, instead of filling the back of an estate car. Even a 35 in (890mm) wing was too big, small two piece aileron wings are fiddly, so it was hack to rudder/elevator. The latest is the Tern and it fits my needs almost perfectly. It fits in the bike box and flys on the lawn at home. It even raised £40 for the RSPCA flying off the back lawn during a garden party! People paid 20p to guess how long it would stay in the air on 6cc of fuel.

It will fly like a free flight sports model - in fact it did so when I forgot to switch the Rx on. On a good day it's not averse to a good thermal, will slope soar, has been used as an R/C chuck glider but it really comes into its own as a low level Barnstormer, performing rolls, loops, pylon turns, 20ft circuits around the operator from a maximum height of 40ft to 3ft - or less if you keep your nerve!

The main requirement is build it light and it will turn tight. Anything over 11.5 oz (325 grams) complete with radio is heavy.

Construction: The model is straightforward to build but when choosing the wood, think in free flight aeromodelling terms.

Wings: Make a ply or hard balsa template for cutting out the ribs. I band saw them out of 3 in block and slice them. Use hard balsa for these, say 7-lb density. Main spars, 9-10 lb balsa, straight grain. Aux spars, 8-9 lb balsa, straight grain. Leading edge, 6 lb balsa, straight grain.

If a 2-piece wing is required, use paper tubes for the 1/8 in alloy welding rod wires. The 5 mm washout is a must, so build it in during construction. Don't worry if it's not quite right, the trailing edge section of the wing is flexible so adjust it when the film covering is shrunk..."

Direct submission to Outerzone.

Update 13/05/2016: 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

Tern (oz7694) by Brian Springall 1986 - model pic

Datafile:
  • (oz7694)
    Tern
    by Brian Springall
    from Radio Modeller
    February 1986 
    34in span
    IC R/C
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 03/05/2016
    Filesize: 421KB
    Format: • PDFbitmap
    Credit*: StewartClydsdale
    Downloads: 1262

Tern (oz7694) by Brian Springall 1986 - pic 003.jpg
003.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, 2011-2024.

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.