1:45.9

[CHE]

Read all about it here :-

http://www.smallflyingartsforum.com/cgi-bin/yabb2/YaBB.pl?num=1269727358/0

CHE

[PeeTee]

Impressive indeed. Also have a look at the vacuum bagged foam wings which Jim Buxton produced for the competition.

To put the achievement into perspective, the record time has increasedby 25% over the past five years (Mark Benns set the record of 1:24.8 in 2005).

For me, even more impressive are the CLG times which are now just a smidgen under 2 minutes. I don't believe that 90 secs has yet been achieved over here, and unfortunately we don't have the same range of venues to choose from. From what I've seen, Cardington is narrower than Tustin, and the roof safety nets and girders are model eaters (both Steve Brewer & I have models up in the roof somewhere ) The  Dome was great except for the bank of speakers up in the roof, but now it is no more of course (well for model flying anyway).

PT

[tonymat]

That's just under 2 minutes for the 12" catapult gliders Pete. Stan's unlimited catapult record (also set at Tustin more than 10 years ago now) is 2 minutes 5 seconds!! That was done with his Sweep-up clg about 18" span.


Tony

[CHE]

I did some trimming at the Dome last year. It was expensive to get in and Prince seemed a little confused when I launched the model during the guitar break for 'When Doves Fly' .................

CHE

[PeeTee]

Prince who?............Phil, Charlie, Wills or Harry?

I think I'd prefer 'Stairway to Heaven' - or should that be 'Maxing Out'?

[JefO]

Only just caught up with this thread - having been on holiday when it was active.

Wow - what a first rate job. Love the use of pink and blue foam in the same wing, does that look perfect or what?

Question to our FF Boffins -
Can anyone tell me what the advantage of a sharp leading edge is? I always thought that the leading edge should be round and smooth to allow the air to keep flowing over the top of the section at high angles of attack and low speeds.

Jef

[CHE]

Mr O,

"Can anyone tell me what the advantage of a sharp leading edge is?"

Provides turbulation and therefore less drag at high speeds.

Will be at the Nats but hopefully busy but do hope to look at the rocket thingies. Weather forecast has been very variable but has settled down a bit to lighter winds now. Fingers crossed; we couldn't have three days like last year could we ?

CHE

PS Wonder if the editor of the sponsoring magazine can be bothered to turn up this year.

[tonymat]

"Provides turbulation and therefore less drag at high speeds."
Well ... yes and no.
A sharp leading edge can provide turbulation. It's sensitive to angle of attack though (not equally effective at all angles) and the benefit is basically for the glide only. It's usually a drag penalty for the climb. Thus as most things with wing sections at low reynolds numbers, there is a trade off.
Brian Eggleston has analyzed Jim Buxton's record setting "Amalgam" indoor glider airfoil and the results will be published in an upcoming FFQ. The shape of the airfoil immediately behind the sharp leading edge is critical to the performance of the airfoil. Too much curvature and  the leading edge just creates drag. Reduce the curvature and a trapped vortex is created right behind the leading edge that acts like a fully functioning tubulator that is not high drag for the climb also. To simply add a sharp leading edge to an airfoil is not enough. Look at Whittman's Supersweep 22 airfoil (very similar to Amalgam) to see the sort of shape I'm talking about.
I've attached a copy of Jim's Amalgam airfoil (courtesy of Jim) so that you can see what he actually used.

Tony

[JefO]

This sport is amazing isn't it?

Still learning the basics after a lifetime of aeromodelling, thanks for the latest batch of enlightenment goodies Tony.

Previously I would have thought that the sharp leading edge would have been an advantage only in the launch phase.

Is the Amalgam TE really thicker than its LE? I have been aiming to achieve the opposite for a few years, so am going to give the Whittman / Buxton treatment to my next projects, where launch height is less important than glide efficiency!

Out of interest, what sections do these wizards use on their tail feathers?

Best regards,

Jef

[tonymat]

Jim's leading edge was apparently very sharp, so indeed it might be thinner than the trailing edge!
I've attached another very good airfoil for your reference. (By the way I have co-ordinates for these airfoils if required and CAD files).
Shown is a modified version of Stan Buddenbohm's excellent outdoor glider airfoil dubbed the "Stanfoil". Note the unusual flat immediately behind the leading edge! This is a very effective vortex generator and a self sustaining turbulator. This version was modified by Brian Eggleston and shows excellent performance using the X-foil aerodynamic tool developed by Mark Drela.

As to stabilizer airfoils, Stan uses a very simple wedge shaped symmetrical airfoil. Basically, the stab is 0.062" (1.5 mm) thick at the high point (aprox 5 % to 7 % chord) and 0.030" (0.8 mm) at the trailing edge with an elliptical leading edge. Literally just a tapered wedge with a rounded leading edge! I make mine with a piece of 1/16" music wire at the leading edge and a piece of 1/32" wire at the trailing edge with the stab blank between them on a piece of plate glass. Just sand until you hit the wires. Round the leading edge and you are done.
I've attached a scan of one of my stabilizers at the root that shows the airfoil better than I can describe it.

Incidentally, while the sharp leading edge as used in these airfoils is primarily for benefit of the glide, I should stress that the clever shaping of the lower surface, the reduced curvature behind the leading edge and the thin flat bottom shape makes them very low drag for the climb. The trick with these models is to find an airfoil that can be launched very high and yet still have a good sink rate. Some undercamber can be used, but usually with a launch height penalty.

Tony