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Scientific Anglers Sonar Leaders for Trout Spey

Sonar Leaders are Scientific Angler’s version of the coated leader, commonly referred to as Polyleaders.


Coated leaders consist of a level monofilament core with a tapered coating of polyurethane or PVC. They are nowadays available in a mind boggling range of lengths, thicknesses, breaking strains and sink rates, for everything from trout to salmon to salt water predators.


Scientific Anglers Sonar leaders are either 7 ft or 10 ft long and both lengths are built on 25 lb nylon cores - there is no 12 lb ‘Trout ‘series. While Sonar Leaders don’t encompass the range available from other brands, they do have some distinct advantages.


To start with, all Sonar leaders within a series weigh the same, regardless of sink rate.Ten foot Sonar Leaders all weigh 50 grains and the seven foot Sonar Leaders weigh 35 grains. The weights of other brands of coated leaders tend to increase with sink rate. Sonar Leader sink rates available within each series include: floating, hover, intermediate, Sink 3 and Sink 6.


Another area Scientific Angler’s Sonar leaders differ from coated leaders produced by other manufacturers is that the coating extends to the very end of the fine tip, in other words there is no nylon core protruding at the tip end. The coating is also much tougher and more strongly bonded to the monofilament core than coatings on opposition products - resulting in a more durable leader.


For this review I discuss the utility of 7 ft and 10 ft Sonar Leaders for Trout Spey applications.



Scientific Anglers Sonar Leaders lying on river gravel

Skagit Heads

The 10 ft Sonar leaders make great tips for light Skagit heads without the grains per foot to cast heavier 10 ft sink tips, e.g 150 grain Skagit heads shorter than 12 ft and 175-180 grain heads longer than13 ft - particularly when used on 9-9.5 ft single hand rods.


Choose the willow coloured floating tip for dry flies, the translucent pale green hover and translucent pale blue intermediate for soft hackles, and the green S3 and black S6 leaders for small to medium streamers. Note, the floating, hover and intermediate are not transparent.


The stand out in the series, for me, is the S6 leader. It is very skinny and wiry stiff, but turns over a #6 bead-head woolly bugger and lands perfectly straight with hardly a ripple, cast after cast. It is also one wind-mocking smooth caster and it sinks exceedingly well for a coated leader. At 50 grains it is lighter than other brands of 10 ft S6 coated leaders built on 24 lb cores.


Perhaps I should qualify my preference.


New Zealand’s rivers and streams are not wide by internationals standards, but they have a lot of oomph and most times when I fishing streamers I need to get down.


When I fish dry flies or soft hackles on Spey gear I prefer to loop on a 150 or 180 grain SA Scandi Lite, because presentation is much better than with a Skagit head and floating or intermediate tip, and there is one less loop-to-loop connection to deal with when fighting fish on light tippets.


Scandi Heads

Another great Trout Spey application for Sonar Leaders is on the end of a Rio Trout Spey shooting head. Rio Trout Spey lines have the long gradual front taper of a Scandi, but they are only 22 ft long, and end in a relatively thick tip designed to handle modest sink tips.


Ten foot Sonar leaders are a fantastic tip choice for Trout Spey heads of 230 to 270 grains, when used on two-handed rods. When it comes Trout Spey and Scandi Body heads in the 305 to 350 grain range I like the slightly heavier 10 ft #5 and #6 Rio Replacement tips because they provide more line stick for the heavier heads.


Seven foot Sonar Leaders are a good choice for 230 to 270 grain Trout Spey heads when used on 9-9.5 ft single hand rods, and in hover and intermediate may also be a better option for soft hackles on light 10 -11 ft two handed rods.


Scientific Anglers Scandi Lite heads have skinnier tips than the Trout Spey heads, as they are primarily designed for use with standard tapered leaders. Although the 150 grain Scandi Lites cannot handle much more than an Airflo 5 ft intermediate Trout Polyleader, the 180 and 210 grain heads are able to turn over 7 ft S6 Sonar leader and a small weighted streamer.

The 300 grain Scandi Lite head casts very well and with excellent presentation with 10 ft Sonar Leaders on 11-12 ft double handers. The 10 ft Sonar leaders would no doubt also work well on heavier Scandi Lite heads.


Attaching Tippet

Scientific Anglers recommend tying a perfection loop in the tip end, to which tippet can be attached. I found tying on a 3mm tippet ring with a clinch knot to be a solution more in keeping with the durability of these exceptional coated leaders.


Tippet rings attached to 7 ft Sonar Leaders


Scientific Anglers Sonar leaders in 7 ft and 10 ft are essential products for the Trout Spey angler.

They provide excellent depth control and presentation with small to medium flies on light Skagit heads and they expand the utility of Scandi style heads.


Sonar leaders cast very well and are extremely durable.


Thanks to Kilwell Sports, New Zealand, for providing me with the Scientific Angler's Sonar Leaders to test.

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