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Secret of the Unicorn

Posted by UniBoffin at 12:15 on 3rd August 2010 in UniBlog

Now all but the most ardent Tintin fan will be relieved to learn that, despite the feebly contrived similarity in title, this blog is not about the forthcoming Spielberg movie but something else on 2011 release. But no 3-d glasses are needed here to appreciate the extra darting dimension as I boldly go and reveal a rather different secret of the Unicorn. I refer, probably somewhat predictably, to Sigmas – The Next Generation.

And this Unicorn secret – about which I’ve already dropped some heavy hints in my recent blogs - is called the Sigma XL. It aims at offering the accuracy and balance of a Sigma Pro 970 or 950 but with a longer barrel and will be available in two aerodynamically-optimised versions, the Sigma XL Pro and Super Pro, both of which feature, among other innovations, a revolutionary screw-in titanium nose cone.

Although devotees of certain darts suppliers’ websites - or even The Big Boss’s and the inimitable Róisín’s tweets - may already know at least some of this, I think I can best explain further if I start at the beginning of the whole Sigma story. Which, somewhat unbelievably for me, was over a quarter of a century ago.

At that point, excuse me while I digress briefly to answer yet again those persistent sceptics who still think I’m a figment of Unicorn marketing department’s fevered imagination! Yes, you did see John Lowe play with Sigma-style flights on TV in the 1980s. But it was still me that designed them. Yes, I’m THAT old and that’s how long it’s taken for Sigmas to be developed from small-batch prototypes to the finished article you can buy in the shops today. Guess I’m lucky still to be around to see them!

Anyway, back at the plot. I originally called Sigmas “Total Design” darts because the idea was to design the barrel, shaft and flights as a total aerodynamic unit with optimal flight characteristics. One technical requirement in achieving this was to have a low moment of inertia (MI) barrel, which allowed a smaller flight to be used without compromising flight stability, thus reducing some of the sources of inaccuracy.

This requirement of low barrel MI (lots on exactly what that is in my past blogs, if you’re in doubt) necessitated the use of very high density tungsten alloy and sophisticated manufacturing techniques, which is part of the reason why they didn’t go on sale 20 years ago. Moreover, as MI increases with the square of length, it also set an upper bound on how long Sigma barrels could be. With the lower bound being set by the ergonomics of most players’ grips and the desire to avoid overly large diameters, this explains why the lengths of both 950 and 970 barrels are limited to a narrow band between 40 and 46mm.

Now I’m keenly aware that the grip of some players better suits a longer barrel than that - 50mm+, say. However, try as I might, I couldn’t make the sums work for a Sigma-performance dart to have the MI so long a barrel implies.

But even if the Laws of Physics can’t be broken, they can sometimes be side-stepped. And in this case that involved a re-think of both dart construction and materials as well as a change to the existing Sigma Pro and One options.

The first element in this re-think was the aforementioned screw-in titanium nose-cone. This not only effectively lengthens the barrel without adding too much MI, it also lessens the front flat, something I wanted to achieve to reduce deflections. Moreover, it allows for easy point replacement – so easy that Sigma XLs come with changeable points in both standard and “finger grip” versions for the player to fit as desired.

The next advance involved accepting that, even with the new nose cone to help, the MI of the Sigma XL barrel would be too large for the very high-stability Sigma One variant. Thus the original plan was to offer only the high-accuracy Pro version, still using the same compact delta Sigma Pro flight as the 970 and 950, but with a much lighter shaft to compensate for the increased barrel MI.

For this reason, for a while I thought the shaft for my new creation might have to be all-plastic, which would not be ideal for a number of reasons. Fortunately, though, recalling some hi-tec metal alloys from my aerospace days, I managed to enlist Q, Unicorn’s engineering wizard, to produce a Sigma Pro-style side-loading shaft with very lightweight magnesium replacing the titanium. The result had exactly the characteristics I was looking for and hence the Sigma XL Pro shaft was born.

And the Sigma XL story might have more-or-less ended there, except for Phil Taylor, who started trimming his already slim flights down to a shape which is now in the Unicorn 2011 range as the “DXM”. As reported in my “Flights of Fancy” blog, this started me thinking, partly because the result was interestingly similar to some of my prototype Sigma flights from the 1980s. And I can show you just how similar below:

On the left is (obviously!) Phil’s self-trimmed flight shape from late 2009 and next to it are two Sigma (or rather “Total Design”) flights from the 1980s. By 2007 the right one of these had grown into the Sigma Pro “compact delta” flight beside it, but the left one had stayed patiently in my drawer, waiting for its moment to arrive. And arrive it now has, as, with some further tweaking, this flight has evolved into the ultra-compact delta flight to be supplied with the Sigma XL Super Pro dart.

But more about that next time!

Joe Pearce and High-Speed Recording
Many thanks for the feedback, Joe (by the way, although the UniBlog Moderator may have posters’ e-mail addresses, quite properly they don’t get passed on). I also just want to say that, before you give up on that high-speed recording, try reading my “Lower Resolution” blog. Legendom could await!

There are 3 comments to this post

Posted by Ethan James Escaño at 09:02 on 7th August 2010

Sigma is cool.

Posted by freddie grice at 19:51 on 8th August 2010

i think that you should put forward the idea of latinum phase 5's. then you wpuld have the phase 5's in every unicorn coating and would make me get all of them for the collection. good idea or not?

Posted by Hayden at 15:43 on 10th August 2010

HI UniBoffin,

Just wanted to ask a question regarding the Sigma Pro 950 darts. As they have been designed with balance etc in mind, how will it affect the flight / balance of the dart if i fit the Target Storm points (26mm Smooth ones)?

Just wondering as am contemplating getting a set however I like using the Storm points in my darts.



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