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Third generation spearguns… how they work?

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With “third generation” are identified two systems: the Fusion and Demultiplied. The Fusion system, invented by Davide Roi, is an improvement of the classic Rollergun where part of the rubbers (that part that enter in contact with the sheaves) has been replaced with dyneema. The result is a gun that can release a bit less power than a traditional roller but at a greater speed.

The Fusion system has as primary objective to improve the precision of the shot by removing the main reason for errors: the recoil. An increase of power, compared to traditional spearguns, can be noticed also.

Studio Session-847_lowDemultiplied system

Studio Session-830

Fusion system

The old “Reverse” system has the rubbers attached near the handle and the long Dyneema wishbone pass through a pair of sheaves (the wheels on the muzzle) and pull the spear. This system has less recoil than the Fusion but also less power as the pretension achievable is minimal or null. It is also somehow harder to use: in the Fusion you can use the small upper rubbers (the “sausages”) as loading handles and this make the reload MUCH easier if compared to just pulling a piece of Dyneema.


With the possibility of pretensioning the game change…

The Fusion configuration chosen by Divecenter.dk is the Fusion PRET (from PRETensioned) and this means that the available energy and time of application of the force is higher than a standard reverse or any ordinary speargun: this increases are going to provide higher amount of Work (Joules) and so more push to the spear.
In the Fusion, the big mass of the rubbers is not hitting on the tip of the speargun, where is more instable, but down to the handle where is much easier to control… so much that you almost don’t feel it.

With the introduction of the demultiplied concept we are instead looking at a complete revolution in the spearguns, with more power (much more) and almost zero recoil (higher accuracy). One Demultiplied speargun can easily outshot any traditional/roller/oleopneumatic speargun both in range and in accuracy.
The recoil on this kind of spearguns is just the reaction to the mass of the spear leaving the muzzle at a speed and is nothing compared to the kick given by a traditional gun to the spearo’s wrist, even more if is a double rubber!

Here below are the charts of the work applied to the spear in 3 different guns:

  • Traditional speargungun

  • Fusion PRET (or Roller pretensioned)

  • Demultiplied (or compound)

The force applied by the rubbers is the same but the time of application change and change also the portion of the force curve that is used (from 100 to 0 Kg or from 100 to 40 Kg).




Range/Accuracy: there is no point in having a 4-5-6m range of the shot if then the accuracy is so low that you simply pass-by the fish and miss it! That is why is so important to reduce the recoil to the minimum…

For Spearo-Engineers: I know that there are many other factors involved, like the spear spin, friction, rubber energy curve, speed etc… will follow on future articles.

Where to find Roisub/Pathos spearguns: http://divecenter.dk/index.php?route=product/category&path=60_133
More about Roisub: http://www.roisub.net/

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