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[CA11] Correct scanner for Black Thunder XT430SC
01-27-20, 05:37 PM (This post was last modified: 01-28-20 12:17 PM by Chuck - Raymarine - Moderator.)
Post: #1
[CA11] Correct scanner for Black Thunder XT430SC
Greetings,

I have a Raymarine a98 MFD I purchased a couple years ago but am just now installing in my 2000 Black Thunder XT430SC Triple. I live on the Grand River about 12 miles inland from Lake Michigan. I do not fish in the boat, but want the DownVision feature to see obstacles in the river bottom.

I did purchase a CPT-100 sensor, but I'm not sure this is the correct sensor for this boat. The boat does get trailered regularly, and because of the weight, the trailer has multiple bunks. There are 3 sets of four bunks (as shown in the attached photos) -- four wide by three long, so that the boat can also be lifted off the trailer using slings if desired. The boat has two steps in the hull as well as a stepped transom, and is capable of approximately 80 mph.

I am concerned that the CPT-100 sensor will not stay in position and get a good read on the bottom. I understand that at speed I may not get a good reading regardless of sensor, but I am concerned this sensor will displace and will have to be moved back into position every time I come home, which somewhat defeats the purpose. Also, with it mounted to the transom, I don't know if it will be too far back and only show me the areas I've already passed. It seems to me that I might need the CPT-120 sensor. But if that is the case, where do I mount it such that I don't damage it when loading on the trailer? Will there be any adverse effects when running, and is there anything I can do to minimize these effects?

Thanks in advance and sorry for the newbie questions - I haven't had this capability before
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01-28-20, 12:47 PM (This post was last modified: 01-29-20 11:15 AM by Chuck - Raymarine - Moderator.)
Post: #2
RE: [CA11] Correct scanner for Black Thunder XT430SC
Welcome to the Raymarine Forum BlackThunderinGH,

I can say with almost complete certainty, that when operating at the upper end of the speeds support by this boat, any fishfinding product will be challenged to maintain bottom. You are most correct in believing that a CPT-100 would not be recommended for this application, primarily because of steps forward of the transducer and because thru-hull and in hull transducers will typically hold bottom at higher speed due to better hydrodynamics (transducer and hull). For vessels having steps, thru-hull or in-hull transducer(s) would need to be installed forward of the first step if seeking to maintain bottom while on plane. See the photo below showing hull aeration caused by steps. While the aeration created by hull steps can do wonders to increase hull efficiency by reducing drag, it does so at the expense of any depth sounding transducers located aft of the steps.

[Image: attachment.php?aid=70]

Raymarine does not offer in-hull CPT-S or in-hull DownVision transducers. As this is a trailered boat, the possibility of damaging thru-hull RV transducers is real ... particularly for any transducer presenting a surface which protrudes above the hull's surface. Use of a tilted element CPT-S transducer may be the easiest means of utilizing the ax8 MFD's Fishfinder feature. As you have suggested in another correspondence, it may also be possible to modify the hull to create a pocket in which a thru-hull DownVision transducer may be installed. The ability of a pocketed transducer to hold bottom will dependent where the pocket is located with respect to hull features and the waterline and the degree to which the pocket wraps the transducer to prevent aeration caused by gaps or protrusions.

It would also typically be recommended that a sounder/transducer outputting greater power than is supported by the ax8/eSx8 MFDs, or CP100 DownVision Sounder Module are capable of (approx. 25W) be used for holding bottom at higher speeds. For hulls such as this, it would typically be recommended that a 600W or 1kW in-hull CHIRP or 50kHz/200kHz transducer be installed. Such sonar imaging has been commonly used for decades to monitor the bottom, find structure, and determine depth beneath the vessel. However, these transducers cannot be used with the internal fishfinder sounder circuitry of the ax8/eSx8 MFDs, or CP100 DownVision Sounder Module and would require that the MFD be interfaced to an external fishfinder sounder module (ex. CP370, CP470, etc.) matching the type of transducer to be installed.
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