As you may already know, the Unicorn 2009 catalogue is now available (not much plot, but still many good points!) and includes my latest excursion into the mystic art of dart design, the Sigma 950. This should come as no surprise to dedicated readers (those determined souls who don’t actually nod off at the very mention of moment of inertia!) who will have caught my past hints about the coming of “Son of Sigma”.
For example, Lonnie probably guessed why I suggested he wait awhile before buying soft tip darts similar to the 19gm Sigma but meeting US league rules by being no more than 18gm. Similarly, I expect Clarence, John P, Chris R, Bob and Warren will not be surprised at the new Sigmas’ longer, more aggressive grip, slight nose taper, and choice of even weights, even though I had to be a bit non-committal when answering pleas for such changes.
These modifications have in fact been long-planned, but another wasn’t decided until fairly recently – changing the barrel material from the original’s 97% tungsten to 95%. Now the cynical will no doubt be suspicious that this is merely an exercise in cost-cutting, but in fact almost the opposite is true – the change was needed to provide the best quality product without incurring too much of a cost penalty.
To explain, 97% tungsten is quite brittle and the design of the original Sigmas had to take this into account by having a front flat on the barrel nose to facilitate precision machining and point insertion. Even so, it had to be accepted that this brittleness means that a percentage of manufactured barrels will not pass Unicorn’s rigorous quality control procedures. Unfortunately the cost of such quality must eventually be passed on to the customer, who may not always be that happy about it!
With the new Sigmas, I wanted to have a more tapered nose to help prevent flight damage during close grouping. However, with 97% tungsten this would have caused even greater machining difficulties and quality control issues. In a world where raw material costs have already risen hugely and keep on rising, the consequences of this on the retail price of the product would have been very severe, so it was decided to use 95% alloy, which, for very little less density, has significantly better machinability.
My task was then to ensure that the slight reduction in density didn’t compromise the aerodynamics - which is, after all, the main focus of Sigma darts. Improving on the aerodynamic performance of the original Sigmas was not possible (if I say so myself), so my aim was to match it using the same Pro and One shaft/flights combinations.
Now this meant designing barrels with comparable moments of inertia (wake up at the back there!). However, to allow close grouping, I didn’t want to increase the diameter of the heaviest dart and that factor, together with my desire to offer a more aggressive grip (which obviously involves taking material off), implied that the 95% Sigmas would be longer than the 97% for the same weight.
Although I saw this length increase as no bad thing in terms of fitting in with the majority of player’s grips, it did mean that a moment of inertia match with the original Sigmas could only be achieved if the weight range didn’t extend quite so far up.
Fortunately (with apologies to any players who were waiting for a 28gm plus version of Sigma), I didn’t see the need for a small weight reduction as a huge problem as I’d already intended merely to “fill in the gaps” in the Sigma steel tip weights on offer by taking a gram off the original’s choice of 21, 23, 25 or 27gms. Unicorn also asked me to add an 18gm steel tip to match the new 18gm soft tip (although the soft tip barrel is actual much lighter as, by convention, its nominal weight includes the shaft and flights whereas the nominal weight of a steel tip dart just refers to the barrel).
So “Son of Sigma” darts were born. Mind you, despite all my calculations to ensure they were just as good aerodynamically as the originals, they still had to pass a crucial test. And, luckily for me, they did so with literally flying colours when, after some judicious throws, the Big Boss pronounced they had “that characteristic Sigma feel”.
So now only one problem remained - what to call them? Sigma 2 was dull, but I still couldn’t resist suggesting it would be nice to write it as Sigma squared, which in statistics is called “variance” and can be a measure of accuracy. This idea, although appealing to a sad scientist like me, met with pitying stares all round, and, although I desperately tried again with a “Sigma Variants” pun, the Big Boss wisely went for the rather less esoteric Sigma 950, at the same time renaming the originals Sigma 970.
Marketing-wise I know when I’m beaten – the new name is clearly one in a thousand!
Q&As
John and Dilithium
Thanks for the advice, John, but the places you mention only do regular dilithium – as I said, I was looking for free-range organic!
Paul and Troy and 2, 3 and 8 “Panel” Flights
Paul (whom I must also thank for the feedback on his curved flights) and Troy want to know why most flights have 4 “panels” and not 3, or 2, or even 8. The answer to this is linked to the lift “non-axisymmetry” I was talking about in my “The Spin Doctor” blog. Whereas 4-panel flights have, as I explained, only around 10% difference in lift between the “x” and the “+” configuration, 3-panel flights have maybe 20% between the “Y” and “Upside-Down Y”. Players who spin their darts a lot might not notice this, but for the rest of us it could create some inconsistent yawing motion. 2-panel flights would need yet faster spin to work even vaguely properly because, of course, in one direction they produce no lift at all.
As for flights with more than 4 panels, for each added panel aerodynamic interference between the panels will cause a slight loss of lift efficiency for a given total panel area. For a set length (chord is the technical term) of flight and amount of lift required, this means that there will be more “total length of panel back” to affect following darts. This wouldn’t be helped by the lower width (span) of individual panels resulting in a reduction in “aspect ratio” (basically span divided by chord), which also causes lift per unit area to fall. Apart from all that, they would also be a bit harder to make and fit!
Clarence and Replacement Sigma Soft Tips
Sorry you’re experiencing difficulties in getting these, Clarence – at the risk of being accused of passing the buck, try e-mailing assist@unicorngroup.com.
Dylan and Sigma 970 25gm
It’s hard to make a recommendation without knowing more about your style, etc, Dylan, but my first thought is that you should have found the Sigma One set up better than the Gripper/Q combination you are using. However, if you have already tried the former without success, you could give CheckOut medium shafts (cat nos 78565-8) and Maestro Xtra flights (eg cat no 68195) a go. Good luck!