transducer

[Zzippy]

Does anyone really know if we have to Have the transducer in Vassaline,water or Sealent????

The only reason I ask is because last week I used my fishfinder whilst out fishing.After about 10 minutes I had realised that I hadnt put any water in the Noodle where I have my transducer mounted.It worked perfectly just sitting on the inside of my hull

Zzippy

[YakDiver]

Maybe your kayak is leaking

Does make you wonder, when I put mine in I just followed what others had done on the US site

[Zzippy]

Maybe your kayak is leaking

Does make you wonder, when I put mine in I just followed what others had done on the US site

Hiya Yakdiver.I have a good yak this time,no leaks yet(Touch wood)My transducer is just inside my centre hatch.When I opened it up to put some water in it was as dry as a bone

[spanner]

It sounds like several things combined to make you lucky... you had your transducer being pushed into contact with the hull by your foam cap, I'm guessing you were in shallow water, and you must have a reasonably high power unit.

 

There are two main things that affect the signal strength.

 

Firstly, the accoustic impedance of all the materials between the transducer and the sea bed. Any time you have a change in materials, tranducer to hull, hull to water etc some of the signal is reflected and only a portion is transmitted. You get 100% transmission when the acoustic impedance of the materials are the same, and the bigger the contrast the more signal is 'lost' through reflection. The plastic hull is actually quite similar to water so that is why can shoot through the hull just fine. If you put somethng between the hull and the transducer, a bonding agent, then ideally you want it to be similar to the hull or the transducer. The face of the transducer is basically epoxy so that works fine. Water in a cup is fine as it is similar to the hull.

 

The second thing is attenuation. Different materials attenuate sound at different rates. Sound travels much further under water than in air, i.e. it is attenuated less. We want to avoid high attenuation materials, stuff that you might consdier good for sound proofing. Spongy, elastic materials tend to high attenaution, especially when they have air bubbles in them as that is a double whammy due to the reflections. That is why silicon is not so good as epoxy, but it is OK if it is free of bubbles and only a thin layer. Vaseline is better than silicon as it is easier to get all the air out, its closer to impedance of water, and you have to mount it in a 'cup' so its pretty rigidly held.

 

There will be a test at the end of term

Edited June 7, 2006 by spanner

[Somerset in Jersey]

Hi all

 

excerpt from my fishfinder gps manual.

 

 

Shoot-thru-hull vs. Transom Mounting

 

In a shoot-thru-hull installation, the transducer is bonded to the inside

of the hull with epoxy. The sonar "ping" signal actually passes through

the hull and into the water. This differs from a bolt-thru-hull installation

(often called simply "thru-hull"). In that case, a hole is cut in the

hull and a specially designed transducer is mounted through the hull

with a threaded shaft and nut. This puts the transducer in direct contact

with the water.

 

Typically, shoot-thru-hull installations give excellent high speed operation

and good to excellent depth capability. There is no possibility of

transducer damage from floating objects, as there is with a transommounted

transducer. A transducer mounted inside the hull can't be

knocked off when docking or loading on a trailer.

 

However, the shoot-thru-hull installation does have its drawbacks.

 

First, some loss of sensitivity does occur, even on the best hulls. This

varies from hull to hull, even from different installations on the same

hull. This is caused by differences in hull lay-up and construction.

 

Second, the transducer angle cannot be adjusted for the best fish arches

on your sonar display. (This is not an issue for flasher-style sonars.)

Lack of angle adjustment can be particularly troublesome on hulls that

sit with the bow high when at rest or at slow trolling speeds.

 

Third, a transducer CAN NOT shoot through wood and metal hulls.

Those hulls require either a transom mount or a thru-hull installation.

 

Fourth, if your Skimmer transducer has a built in temp sensor, it will

only show the temperature of the bilge, not the water surface temp.

Follow the testing procedures listed in the shoot-thru-hull installation

section at the end of this lesson to determine if you can satisfactorily

shoot through the hull.

 

 

It also states the use of epoxy and shows the transducer mounted in a cavity secured by a small film of epoxy then flooded around the transducer with epoxy. thus making a sealed block similar in construction to the actual transducer itself.

 

I am in the proces of ordering a new transducer for my finder as the other unit is firmly fixed to my other toy.

 

will have a play as i now you can get suction cup support fixings for the transducers and that is going to be my first go, cheap and simple and can easilly be removed or relocated.

 

hope this helps aswell.

[Somerset in Jersey]

found a picture of the suction cup system if required

[Zzippy]

Cheers lads.Some good info there.

Spanner....I was in shallow water compared to what your used to I passed through the main channel which was 68feet at the deepest.Then was in the Swash channel which was about 28-32 feet.I added the water to the cup I made out of a swimming noodle connector.It showed exactly the same as when I didnt have water.

So as you say...I must have been lucky and had it flush tight against the inside of my hull

But I did forget to empty it when I put the kayak upside down on my roof rack

[RayJ]

found a picture of the suction cup system if required

 

I have used the suction cup method...it is ok for short term use but found that it kept getting tangled in seawead and occasionaly fell off.

I didnt really care for it tbh.