shoot through depth transponder

[Guest]

I'm considering a shoot through depth transponder in the forward part of a ferro cement hull. reading that ferro is not good for this but fibreglass is fine so am wondering about bashing a hole in the ferro cement and then filling the hole with fibreglass and placing the transponder over the glass.

Any suggestions about how to go about this, indeed if its feasible, would be greatly appreciated. I would use epoxy and glass.

[banaari 27]

If you're going to have to bung a hole in the ferro anyway... why not bury the transponder _in_ the epoxy, more or less flush with the outer surface?

[Battleship 100]

Or just put a through hull in, makes for easy replacement of the transducer if you have issues.

[wheels 543]

Through Hull would be best bet. I really don't know how you would bash a hole without creating possible wider spread damage. Cutting a hole with a diamond holesaw would be better. A lot of steel inside that Plaster. I also don't know about how strong a joint between Cement plaster and Epoxy that would be. Cement does not bond that well with Epoxy. It can crack due to different expansion rates Epoxy Mortar is a better material, but then I am not sure the transducer would fire through it. Even through Epoxy and glass, you do have a huge loss in sounding power. Most certainly a through Hull would be by far the better way of going.

[Guest]

The reason for suggesting the glass shot through is to get the transducer way forward. Still shooting straight down though. I agree simply putting a ducer in as usual is the most easy way but it would be pointing in the wrong direction.

[Marshy 30]

Raymarine do a tilting sensor?

http://www.raymarine.com/view/?id=199

[wheels 543]

agree simply putting a ducer in as usual is the most easy way but it would be pointing in the wrong direction.

That's why you use a fairing block. The side between block and hull is shaped to to suit the angle so the face of the block is horizontal to make transducer point down. The block can be Wood, Epoxy, Epoxy mortar or Cement even.

However, unless you are firing forward to "see" what is coming, then really you are going to see a rock pretty much as you hit it.

[Guest]

Got to be better than seeing it ten metres after I hit it! With a block tilted i'd end up with a huge lump hanging off the bow, id rather the lump inside the hull. You've got to remember this is a racing ferro here, these things are important! I'm not worried about the fish, nor a great depth either. I don't think the tilting ducers will have enought tilt on my bow.

If epoxy sticks to ferro with cement in it it would also stick with glass in it, well i think it would. Putting a hole through is easy, just hammer drill some small hole in a suitable circle and pound out the cement, cut the steel.

[wheels 543]

So you are able to mount the transducer 10ft further forward. That might give you a whole second earlier warning at the most. A seconds earlier warning is not going to save you from the inevitable. To me, you are somewhere you should not be for starter. You should have first plotted your course on the Chart and maybe at least using the GPS and not be anywhere near anything that can cause you such grief.

It is one reason why I never bothered with the Interphase forward looking Sonars. To me, you don't get enough fore warning even with that kind of device and should not be in waters where you start having to reply on such to tell you what is in front.

Any "fish finder" type device simply does not give you positional accuracy of under water obsticles, due to the way the info is portrayed on the screen. What you really need is a 360deg canning Sonar to give you positional info. A "fish finder/depth sounder" only gives you a very inaccurate 2D picture.

[Guest]

More like 10 metres in my case. I think it would be very useful when anchoring, going dead slow. I really don't need a lecture on how to navigate Wheels. Thanks.

[wheels 543]

Not a lecture, just in general conversation. I always view posts as "open conversations".

[Guest]

I'm thinking a fg tube, really strong glued into the hull with the top above the water line. The transponder attached to a lid with a rod to bring it down to near the bottom of the hull. I could be pulled to clean .

[Battleship 100]

Just curious bbay, what exactly are you trying to achieve?

Sounds like a really elegant solution to a non existent problem.

Is it just a better way to use an existing transducer?

[Guest]

Just in the habit of looking at these problems from all the angles Willow. At the moment I have a transducer attached to a rod aft that I can drop into the water when needed. Its an ugly arrangement but it works ok. Seems to be at the wrong end of the yacht. So i'm thinking of making a proper job of it.

[Guest]

Here's what I think may be best... shoot through transducer.. hole in hull glassed over and a tube glassed in over the ex hole...transducer placed in tube with oil or water.

[wheels 543]

Personally I think there will be too much attenuation of the sound energy returning to the transducer. A fibre glass hull transmits the sound due to two points to consider. The density of the Glass/resin and the fact that a large area of the Glass resonates. I think the FC hull will absorb too much sound and the very small area of glass will not allow enough sound to transmit through. But that is my thoughts, I may be wrong. There is only one way to know for sure.

[Guest]

Thanks Guys, food for thought. I've read the things will shoot through oil, glass as long as no air bubbles are present.

Yes it would be easier Motorbike, for sure. One thought though is that being forward there's quite an angle involved which means the ducer would have to have a lot of stuff bolstering it to make it point down. Now being in the part that first parts the water could lead to something , like a log, being hit right where the ducer is. With the packing that could be a disaster in the making or at least test the emergency bilge pump. It is a different situation and I'm thinking shooting through glass is a good option, agreed no speed or temperature.

[wheels 543]

A little issue I am having with my sounder right at the mo, is that I coated the surface of the transducer in Anti-foul. Now I am not getting a reading of any deeper than 4.8ft. Which is probably reading of the edge of the Keel below it darn it. So firing through anything will mean an attenuation in it's power and that means you don't get good depth.

However, I have fitted transducers to the inside of Glass Hulls and have had them work OK. They were commercial units however with plenty of power.

[Guest]

Looks like you will be going for a swim with a wire brush Wheels!

[Island Time 1,240]

Interesting Wheels, I've always anti-fouled my transducer (both the instrument 52mm one, and the interphase one) and not had a problem...

 

Also, in relation to your earlier comment Wheels, re the fwd scanning interphase units. Mine (Probe) can see 210m fwd, on about a 16 deg arc (8 deg either side). I have often used it for coral and or uncharted entries. It's been fantastic until a log broke the transducer off Borneo - have not yet been able to afford a replacement transducer. But I will. How far fwd do you need to see before you would think it's useful?