Break out the Fish Hawk, or don't

[Slow&Low]

At what depth of water do you start using the a Fish Hawk (or any other similar device) when trolling and you want an accurate reading of speed at the ball? Assuming your boat has surface speed capabilities and you trust that information to be accurate at the surface and similar at the downrigger ball up to a particular depth.  Photo is for show, Canadice Lake 2019. 

[Zinger11]

If I'm running a downrigger my probe is on it

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[ThreeDogsDown]

Agree with Zinger.


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[Sk8man]

Your question has a basic problem from the start. The speed at the weight and speed at the surface do not have the same constants attached to them to allow a direct comparison. The surface speed is based on either an impeller attached to your depth finder or GPS speed noted on it. They each refer to different measures of speed and are based on different factors. As such they have different error factors attached to them as well as the GPS speed is based on speed over ground (the lake bottom) and the impeller device is measuring the relative speed of your boat moving across the surface of the water which is based on the rate of rotation of the impeller as it processes the water turbulence passing over it. These impellers are usually least accurate at the extreme upper and lower values. The speed at the weight of the downrigger using a Fishhawk is also based on an impeller type measure and it is a function of the rate of water passing over the surface of the impeller causing it to rotate which in turn is interpreted as speed on the display. Because this impeller is down below the boat and not at the surface the measure is very different as it can be affected by many other factors such as underwater current, the movement of the weight back and forth in the water etc. In other words you can't assume that the speed at the weight and speed of boat at surface will always be the same even if just slightly below the surface. Beautifully spotted up brown by the way

Edited September 29, 2020 by Sk8man

[Legacy]

At what depth of water do you start using the a Fish Hawk (or any other similar device) when trolling and you want an accurate reading of speed at the ball? Assuming your boat has surface speed capabilities and you trust that information to be accurate at the surface and similar at the downrigger ball up to a particular depth.  Photo is for show, Canadice Lake 2019. 

Always in the water...

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[spoonfed-1]

4 hours ago, Slow&Low said:

At what depth of water do you start using the a Fish Hawk (or any other similar device) when trolling and you want an accurate reading of speed at the ball? Assuming your boat has surface speed capabilities and you trust that information to be accurate at the surface and similar at the downrigger ball up to a particular depth.  Photo is for show, Canadice Lake 2019. 

 

3 hours ago, Legacy said:

Always in the water...

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YUP

[Slow&Low]

Thanks for the replies. Knowing the cost of a new probe I was thinking if you don't need it, leave it in the boat. My mindset was shallow water (0-30') vs the surface speed, regardless of GPS or at the transducer would be very similar. I will rethink my shallow water approach and keep the FH probe in the water.

[HB2]

I guess it's about how much of a feel  you have and how well you are in tune with what you are doing . 

I fished without down speed for 30 years,and now that I have it ,  things got a whole lot  easier .

 

On my big boat it's out past 40 ft .inside that , the surface speed is enough. Why risk losing 300$ . Deeper than that , it's hard to judge sub surface currents . 

 

 

On my little boat I have no speed at all and I seem to do pretty well . There are ways to compensate for it to draw,hits . I keep saying to myself I'm  going to get a probe add on   for my depth finder, and might ,  but I like  the challenge of using my expertise . Makes me better . 

Edited September 29, 2020 by HB2