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Nov 07, 2009, 10:58 PM
jhraley's Avatar

Still researching the Airspeed Tern

Still working on 1/3 scale plans for the Airspeed Tern. I have included all I could fine on the internet. I also have Martin Simons' 3 view. Martin's plans are a little vague and things like rib spacing and the diagonal bracing seem suspect. He only gives it a "C" rating in his book. Is there anything out there I am missing before I commit to what I have?
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Nov 07, 2009, 11:31 PM
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Bill L's Avatar
sweet project
Nov 08, 2009, 01:01 AM
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My observations based upon the photos and compared to Martin's drawings:

Apex of the wing tip curve needs to be moved forward;
Radius of the stabilizer/elevator tips needs to be roughly doubled;
Radius of the very tip of the nose needs to be reduced markedly;
Curvature in cockpit opening is lacking; there should be no angle at the instrument panel;
Curvature of central fuselage longeron from wing spar to nose needs to be reduced;
Aileron hingline intersects the wing tip at the wrong place;
Leading edge of vertical tail needs to be more curved, aft less curved, area at base increased;
Horizontal tail has slight radius faired to fuselage at leading edge;
Fuselage is thick at the aft end of the tail boom in side view, probably too wide in top view too;
Line of nose skid needs to reduce aft to front more fairly;

I would suggest tracing the photographs you have, including all flying and control surface junction points in the fuselage and longerons and stringers shown. Next overlay those drawing with Martin's. Then distort them with skewing, rotation and other tools to get the outlines to match and then note where the structural details and shapes you've pulled from the photos correspond to the three view. This should clearly show the discrepancies and what needs to be done to correct them.

Then take your new three views into Photoshop and see if they can easily be distorted to now match closely the phots you traced, once distorted for perspective and angle of view.

This is a very sweet design, really cool and simple to model. Let me know if I can help.

Nov 08, 2009, 01:55 AM
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three more for you. Keep us posted on your project
Nov 09, 2009, 08:41 AM
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Tern - info from British Gliders and Saiplplanes 1922 - 1970

Sorry I think I promised you this last year.

Here's a 3 view from Norman Ellison's book.

It probably has imperfections like most 3 views. Btw, Norman and Martin Simons occasionally worked together, so it's just possible that any innaccuracies could be shared.

Apparently there were 3 Terns built, although only 1 was BGA registered (BGA190). No.3 was finished by the Dart Aircraft Co. at Dunstable.

A. Coulson, of Newcastle in North East England bought No.2 and No.3 and cobbled them into one glider with the rear fuselage top decking removed, a reduced rudder height, and dihedral added. He sold this to the RAF gliding club in Bedfordshire.

So there we are, lots of key facts no vintage glider fan can sleep without
Nov 10, 2009, 10:34 AM
jhraley's Avatar
Thanks everybody. All your input will help a lot. Doesn't it seem odd that the surviving Tern (Terns) disappeared? Somewhere in Bedfordshire in an old barn next to where the airfield use to be, up in the hay loft lays the remains of an Airspeed Tern. Only the mice seem to know.
Nov 10, 2009, 11:45 AM
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Photo - 3 view Comparison Airspeed Tern

Originally Posted by Sutton Bank
Here's a 3 view from Norman Ellison's book.

It probably has imperfections like most 3 views. Btw, Norman and Martin Simons occasionally worked together, so it's just possible that any innaccuracies could be shared.
Actually, the Ellison three view is more accurate than the Simons version in several regards, comparing again to the photos, But Simons' overall is probably better in the fuselage overall.

What is not correct in Ellison's seems to be the following:
Wing tip chords are too small (taper ratio of wing incorrect);
Wing tips are not correctly shaped, (apex of curve needs to be skewed forward);
Canopy windscreen is not correct (Simons' is in fact);
Nose is not pointed enough;
And there is a distinctive small hump in the curved line in side view in the nose and aft of the cockpit that none of the three views depict except for yours John, but only the one aft of the cockpit.

I am basing this on the photo "Chapter 15 Britain" which clearly shows the three details of point of the nose, turtle deck curvature and hump while the underside in flight view clearly shows the taper, tip shapes and aileron placement on the wings. There is curvature in the aileron trailing edge outboard section that is not shown in Ellison's drawing. Simons' shows this correctly but the entire wing tip curve is not symmetrical as he shows in planview. I've put it up here from Vincent's Retroplane pages for comparison.


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