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Pbraffit - - - Transducer and Aluminum Hull

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Pbraffit - - - Transducer and Aluminum Hull

Old 12-24-2003, 07:16 AM
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Default Pbraffit - - - Transducer and Aluminum Hull

I am looking to replace my transducer with the 256 series transducer . . . to be hooked up to existing Lawrence 104C

Which model - configuration should I use for a welded aluminum hull . . . thank you in advance



. . . just thinking out loud . . . yes, I'm "Miss-Be-Haven"
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Old 12-24-2003, 10:47 AM
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Default Pbraffit - - - Transducer and Aluminum Hull

How thick the aluminum will have a great affect on the performance. Any material that the transducer has to shoot through will probably match the frequency at some point, but it will vary by frequency and hull thickness. I have a chart I put together that explains each frequency and it's loss based on material thickness but I have to figure out how to post it for you. I have one for aluminum and another for 'glass. They are Excel files but I can attach them once I figure that out. I will work on it during the holiday break, but I'm also hinting for instructions.

Happy Holidays.

Peter Braffitt
Business Development Manager
AIRMAR Technology Corp.
Milford, NH USA
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Old 12-24-2003, 12:18 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

Woops . . . I meant that I would drill a hole through the hull to afix the transducer under the boat . . . sorry about that . . . the hull is 1/4 plate . . . thanks . . .



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Old 12-24-2003, 04:07 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

Auguste, don't use a bronze 'ducer on an aluminum hull, they'll eat each other up.

Peter, I contacted your tech dept about shooting thru an aluminum hull and they discouraged it - what is the "hull truth"? Does it work? I have an R155 50/200 that I currently have mounted off the transom on a huge bracket (and I have problems with it there). I have a flat step in my hull just forward of the engines that the R155 could be bonded to if it would work. Pls advise, my hull at that point is 3/16"

28' Maxcat w/twin Honda 225's
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Old 01-06-2004, 02:53 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

. . . to the top, hoping to hear from Peter on my aluminum shoot-thru question.

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Old 01-06-2004, 03:48 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

We commonly discourage shooting through aluminum because aluminum is less forgiving in reference to thickness than fiberglass. We have done a fair amount of testing and found that the loss through aluminum is significantly different at 50kHz than at 200kHz. For example at .08" aluminum 50 has virtually no loss but 200 loses 15dB. At .32" 50 loses 15dB and 200 loses 27dB. At .48" both frequencies lose about 21dB, but at .60" the 50 loses 23dB but 200 has no loss. That cycle seems to ocilate as the thickness repeats in multiples. As you can see the sound pressure loss can be significant but in some cases an in-hull is the only thing that makes sense.

My reccomendation is not to shoot through aluminum unless you see no other choice. Chaps, you are correct that you don't want bronze in contact with aluminum, the aluminum will probaly lose, but either way the damage will be done. We make an SS560, which is basically a stainless B260, that can be installed into an aluminum hull. You still need to isolate it so it's not in contact with the aluminum, but we supply it with a fairing to aid in the isolation. If you want to try the R155 shooting through the aluminum you can flood the bilge with a few inches of water (if you dare) and place the tranducer in the water. This will allow the transducer to couple to the hull and will simulate a proper wet-box installation. If you aren't that daring that fill a small trash bag with water, place the transducer in it face down, wet the hull and place the transducer onto the wet area. This may take some tinkering to get a good seal to the hull (no air can be between the transducer, bag, and hull) but is much easier on the nerves.

I hope that answers it for you. I need to figure out which postings I should be looking at so I can get you all timely answers. I'm not sure what I'm in for but this could turn into a full time job!

Peter Braffitt
Business Development Manager
AIRMAR Technology Corp.
Milford, NH USA
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Old 01-06-2004, 06:24 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

Peter

Thanks, waiting for the response . . . below is a pic of my boat



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Old 01-06-2004, 08:44 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

Peter, thanks for the clarification. I think I will proceed with a fabricated can welded into the hull that will provide a pocket I can mount the 'ducer into. That way it will be flush with the hull but exposed to the water. Really appreciate your input here on the board.

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Old 01-07-2004, 08:08 AM
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Default Pbraffit - - - Transducer and Aluminum Hull

Chaps,

Peter Braffitt
Business Development Manager
AIRMAR Technology Corp.
Milford, NH USA
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Old 01-07-2004, 08:08 AM
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Default Pbraffit - - - Transducer and Aluminum Hull

Chaps,

Peter Braffitt
Business Development Manager
AIRMAR Technology Corp.
Milford, NH USA
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Old 01-07-2004, 08:10 AM
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Default Pbraffit - - - Transducer and Aluminum Hull

I would say you will have the best installation around if you go that route. We provide a lip on the face of the R199 so it can be mounted in the fahion you are refering to. This is a common method in commercial vessels and there are many very succesful installations. If you need drawings of the R199 to work with let me know.

Peter Braffitt
Business Development Manager
AIRMAR Technology Corp.
Milford, NH USA
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Old 01-07-2004, 01:29 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

Peter - Is the R199 shown on your website? I would be interested in seeing that unit . It sounds like it has a mount flange that would allow thru hull/flush mounting on a horizontal (flat) hull surface? If so I would strongly consider changing from the R155 to avoid all the hull work as I described above. Thanks again.

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Old 01-07-2004, 07:53 PM
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Default Pbraffit - - - Transducer and Aluminum Hull

Peter, OK, I found the info on the R199, PDF files, no need to respond

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