[CA] RV Transducer(s) placement help

[scott06903]

Hi,

I would line to determine the ideal transducer to purchase based on the hull of my Grady White 282 Sailfish. There are a few potential issues with his hull that I would like some input on.

There are pickup and discharge ports for the marine head about 20 feet forward of the transom close to the center line

There are 3 water pickups about 2-3 feet forward of the transom close to the center line.

There are 2 molded in transducer pockets about 2-3 feet forward of the transom and about 3 feet from the center line.

My main concern is aerated water from the two ports in the head.

Ideally I would install the RV 200 on center line just forward of the water pickups. The bottom of the boat is slightly rounded and not flat so it would either need to be sanded flat or a fairing block would need to be installed. The angle is not severe but i am weary about removing material in a 12"x4" area on the bottom of the boat.

The other option is the rv220 set. Now the question is where to install these? I can consolidate the 3 current water inlets to 2 inlets so there is some flexibility. I worry about clean water again because of the ports for the head.

Based on what I have read here, the transducer pair should not be more than 36" apart so using the built in pockets would not work plus they are designed so they are flat facing the bottom and there are no "0" offset transducer pairs that I know of.

Please see linked photo http://i.cubeupload.com/qJwiw9.jpg

that shows the location of the forward ports (other port not in pic but same location on other side) the 3 water intakes and the starbord transducer pocket with existing ducer.

Please let me know what you guys think.

Also at what speed should I realistically be able to read bottom, scan sides, use 3d etc.

Thanks in advance

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Scott,

The Grady White 282 Sailfish has a deadrise of 20.5". Accordingly, RV transducer pair would typically be recommended for this application. The problem is that there is no way to absolutely predict whether pickups and discharge through hulls will cause an aerated flow of water across the face of the transducers which are located anywhere other than alongside or forward of the through-hulls. I would recommend that you consider moving the head's through-hull aft and additionally consider filling the transducer pockets should doing so reduce the chances of having an aerated flow of water flow across the face of the transducers. It would be recommended that the RV transducers be located adjacent to or forward of the engine water pick-up through-hulls.

[scott06903]

Thanks for the reply.
I am wondering if the rv-200 might be the way to go? While the bottom is not perfectly flat it may be able to be made flat in the approx 4" x 12" foot print of the RV 200. I am going to measure how far out of flat the bottom is this evening. I may be able to mount it on the keel forward of the water pickups ..or relocate them if needed.

Assuming clean water what is a realistic speed to expect the rv transducers to operate?


Unfortunately it is not practical to move the head through-hulls near the stern. I may be able to move them back a few feet from where they currently are and mount a RV-220 pair in front of them. This location is pretty far forward but according to Grady this location is under water when planing. Grady does list this location as a spot for shoot through transducers but I have read mixed results on installs. I need to verify deadrise here, I think it is greater than 20-25.

I want to take the time to explore all of the potential locations so I don't need to relocate later.

Thanks

[Chuck - Raymarine - Moderator]

Q1. I am wondering if the rv-200 might be the way to go?
A1. Unfortunately, there is no way to be certain about this and it is likely that low CHIRP conical sonar (the sonar technology supported by the RV transducer which will perform better than the other supported sonar technologies at higher speeds) would drop out sooner than would occur with a properly installed RV transducer pair.

Q2. Assuming clean water what is a realistic speed to expect the rv transducers to operate?
A2. Please click here to view a FAQ addressing this subject.

[scott06903]

Hi Chuck

I seem to have 3 options here

Option 1 place the rv 220 set forward, where the head through-hulls are and move those back a foot or so. This will move the transducers below where the helm is, see linked photo.

http://cubeupload.com/im/NqtH5K.jpg

This location will experience a higher likelihood of being out of the water in moderate and above seas when planing. (moot point if these only work at trolling speeds as the faq seem to indicate) I am assuming trolling speed is 8-10 mph or lower?

Option 2 is to locate the pair in the stern and relocate the live well/ wash down water intakes aft or out bord of the transducers. I will still have to deal with the potential of the head through hulls disturbing the water.

http://cubeupload.com/im/Pgf7Wy.jpg


Is there a hierarchy of location preferences in relation to through hulls? i.e is outboard of the transducer preferred to inboard?

Regarding general placement:
Is farther back on the boat preferred to closer to the bow

Does clean water at trolling speed trump a more aft location?

I have seen the diagrams on placement but they do not include discussion of forward through hulls.

Option 3

Place the transducers between water intakes and the transducer flats, link below

https://cubeupload.com/im/ZWnikS.jpg

I am concerned that the inlets may cause problems, partly because they are inboard of the transducer. I would think air will migrate to the surface from the keel up so any transducer inboard of an intake would be less likely to have aerated water interference.

One last question, I have an existing dsm300 with a B744v transducer. Will I be able to use this with the Axiom pro? Can I connect directly to the Axiom or do I need to use the dsm 300? Are and adapter cables needed?

Thanks

[Chuck - Raymarine - Moderator]

Scott,

Unfortunately, your photos cannot be viewed without creating an account where you posted them. Please re-size the photos to be less than 500kb (100kb should be sufficient and then attach them to a response to this post.

Regarding the B744V fishfinder transducer, should its cable be terminated in a plug which was designed to be directly mated to the DSM300, then it may be adapted (A80496) to be mated to the 50kHz/200kHz/CHIRP transducer socket of the Axiom Pro RVX MFD.

[scott06903]

Hi Chuck

Photo 1 below is an estimation of where the head through hulls are

http://forum.raymarine.com/attachment.php?aid=1622

Photo 2 below depicts where the transducer stems would be placed where 2 of the current intakes are, the third would be removed and all relocated aft of the transducers.

http://forum.raymarine.com/attachment.php?aid=1623

Photo 3 is a proposed location between existing intakes and transducer flats.

http://forum.raymarine.com/attachment.php?aid=1624

[Chuck - Raymarine - Moderator]

Scott,

Q1. Option 1 place the rv 220 set forward, where the head through-hulls are and move those back a foot or so. This will move the transducers below where the helm is, see photo. This location will experience a higher likelihood of being out of the water in moderate and above seas when planing. (moot point if these only work at trolling speeds as the faq seem to indicate) I am assuming trolling speed is 8-10 mph or lower?
A1. Trolling speed is within range which you have specified. However, at trolling speed, there is also little or no aeration of the water beneath the hull. Aeration generally begins at higher speeds. Accordingly and as long as you will be satisfied with using the B744V at higher speeds (assumes that the B744V currently performs well in its present location, then you may want to consider Option 2, as it will likely provide the RV transducers with deadrise which is within the range which they were designed to be installed.

Q2. Option 2 is to locate the pair in the stern and relocate the live well/ wash down water intakes aft or out bord of the transducers. I will still have to deal with the potential of the head through hulls disturbing the water.
A2. See the response to Q1.

Q3. Is there a hierarchy of location preferences in relation to through hulls? i.e is outboard of the transducer preferred to inboard?
Q3. It is recommended that the RV transducers be installed inboard of the B744V.

Q4. Is farther back on the boat preferred to closer to the bow.
A4. Yes.

Q5. Does clean water at trolling speed trump a more aft location?
A5. Clean water and not separating the RV transducer by too great of a distance are the most important considerations.

Q6. I have seen the diagrams on placement but they do not include discussion of forward through hulls.
A6. In spite of no specific directions to the contrary, through hulls, steps, etc. located forward of the transducers may (and most likely will, particularly if they are directly in line with) will cause an aerated flow of water across the face of the transducer at speeds above trolling speeds, preventing their proper operation at such speeds. The size, shape, and other physical characteristics of such objects is s determining factor in the speed at which they will trail an aerated flow of water.


Q7. Place the transducers between water intakes and the transducer flats.
I am concerned that the inlets may cause problems, partly because they are inboard of the transducer. I would think air will migrate to the surface from the keel up so any transducer inboard of an intake would be less likely to have aerated water interference.
A7. See the response to Q1. I would recommend moving the intakes aft.

[scott06903]

Thanks,

and you would recommend the rv-220 pair over the rv-200 on the keel? in both setups the intakes would need to be moved aft.

[Chuck - Raymarine - Moderator]

Scott,

Should the keel of the hull be flat enough to accommodate the rv-200 without fairing, then it would be reasonable to consider using it instead of a RV-220 pair. Dimensional data for the RV-2xx transducers may be found here.