Building the Ultrasonic Antifouling Kit from Jaycar

[Norman_E]

Encapsulation 2

My method works well, though the foil is quite hard to peel off, which may be down to my use of an old spraycan of dry silicone as a release agent.

I have however found a little problem, which might happen however you do the job. The transducer was pushed firmly down, with four little pieces of just under 1mm thick plastic glued to it with superglue, to act as spacers. On peeling off the foil, only two were visible, as the transducer appears to have tilted slightly. Careful probing of the potting compound, aided by a small air bubble, reveals that the tilt is very small, with the base of the transducer about 1.2mm from the bottom at the high side.

I am carefully rubbing the base of the unit on a piece of fine sandpaper to reduce the average thickness of the potting compound below the transducer to 1mm. I doubt that it is critical, but rubbing the unit down with the sandpaper on a flat surface is producing a flat base with no ripples in it where the foil did not sit perfectly flat. I will fill the little hole when I pot the other transducer.

 

[Fr J Hackett]

Thanks Norman that was what I was thinking probably about 3 or 4 feet in front of prop, ruddder and skeg as close to the keel as possible with the other ( I ordered 2 ) just in front of the keel as it's quite a sharp fall off and would be about a third of the waterline length back, if that makes sense. If it works and is patchy I can allways put a 3rd transducer in later. Looking forward to it.

As an afterthought I could mount them on the top of the keel which is solid ie has encapsulated ballast but don't know if there would be significant attenuation of the signal and associated loss of performance.

 

[Norman_E]

I doubt mounting them on top of the keel would work, as the idea seems to be to transmit the ultrasound through the hull into the water. I may be wrong on this but I think that ideally the transducers probably need to be on the relatively thin hull in which they set up an ultrasonic vibration, and probably midway between stringers to let the hull act a bit like a sounding board. They don't work in cored hulls, and a thick keel with encapsulated balast would probably have a similar effect.

 

[Norman_E]

I tested the first unit this evening. If you listen carefully the potted transducer makes a very faint clicking sound.

The second transducer is in the clamping fixture and has just had the compound poured over it. There is no leakage at all this time. Again the hardener was crystalline, it looked as if it had sugar in it, and had to be clarified by immersing the pack in warm water. Doing that is a good idea anyway as warming the two parts makes mixing much easier.

 

[Norman_E]

Its been staring me in the face

I have just realised that instead of using kitchen foil in place of the cling film when potting the transducers, the ideal material has been staring me in the face. The potting compound comes in strong foil outer pouches, which are much tougher than ordinary kitchen foil. (they may be plastic, but look like very thick aluminium foil) If I was doing one again I would cut open a pouch and use the inside surface, coated with silicone.

 

[VicS]

I have just realised that instead of using kitchen foil in place of the cling film when potting the transducers, the ideal material has been staring me in the face. The potting compound comes in strong foil outer pouches, which are much tougher than ordinary kitchen foil. (they may be plastic, but look like very thick aluminium foil) If I was doing one again I would cut open a pouch and use the inside surface, coated with silicone.

How about opening out a drinks can? Aluminium but almost paper thin

 

[Fr J Hackett]

Or a sheet of glass

 

[Elessar]

I have found the time to encapsulate the first transducer. I was concerned that the method described in the article could lead to the socket and nut becoming stuck together, so I thought up another method. What I did was to make a clamping fixture to hold the socket firmly down to a board without the nut. The fixture consists of a double thickness of melamine faced chipboard, with a third piece as the clamp. The third piece has a 64mm hole in it, which is a standard hole-saw size, to enable the resin to be poured.

My efforts to use cling film failed as it rucked up when sprayed with silicone dry lubricant which is intended to act as the release agent, so I have used aluminium foil. A small amount of the resin has escaped at the bottom, but it is not significant. It will be many hours before the resin sets and I can remove the clamp.

I did have a couple of problems with the resin mix. The first was that the translucent hardener could be seen to have crystallised, probably due to getting cold in transit. That was rectified by placing the bag in lukewarm water until the crystals could no longer be seen. The second was that in my efforts to remove the plastic clip that separates the two halves of the bag, I made a pinhole in it, and the mixing process became a messy one.

The photo should give some idea of how the clamping fixture works.

can you explain this some more? why is the resin not just poured into the transducer why all the complication? I guess I'm being dull but am very interested....

 

[Norman_E]

To understand it you really need to see the instructions given in the magazine articles. The method described there is a complex one using the plastic nut fixed to a piece of melamine faced board with cling film on it. Precautions have to be taken to prevent the potting compound, which is quite liquid, from getting onto the threads and sticking the parts together. Another issue is the use of cling film, because the silicone spray used as a release agent can cause it to wrinkle.

My method is to make the fixture shown, and use foil instead of cling film. A piece of unwrinkled foil is placed shiny side up between the two wood battens and sprayed with dry silicone lubricant. The bottom edge of the plastic socket is also given a smear of the silicone by finger. The four long screws serve to clamp the top board down tightly on the socket and force it against the foil so that the compound cannot run out.

 

[Norman_E]

Or a sheet of glass

Not a good idea, the potting compound is a superb adhesive, and even with the silicone acting as a release agent it takes some effort to peel off the foil that I used. You would probably have to chisel glass off.

 

[bitman]

parcel received

got my parcel received this morning; total cost of £134.07 (jaycar £111.24 + uk customs £22.83)

now it's building time

 

[Norman_E]

Have fun! When I started this thread I thought it would interest one or two confirmed experimenters like me, but with over 2500 views so far it is now one of the most viewed threads on this forum, so perhaps lots of people are thinking of building the kit, or maybe just waiting to see how easy it is. As someone who had done no electronic work for nearly 50 years, I can only say that it is not too difficult at all.

 

[Fr J Hackett]

got my parcel received this morning; total cost of £134.07 (jaycar £111.24 + uk customs £22.83)

now it's building time

So when did you order yours, what responses etc can I expect.

I ordered my two on Sunday night, Monday morming Aussie time, got an order confirmation by return but no mention of additional postage etc. I was expecting to have had a request for the excess postage by now and hope to recieve the kits in 2 to 3 weeks. So what was your time line.

 

[bitman]

So when did you order yours, what responses etc can I expect.

I ordered my two on Sunday night, Monday morming Aussie time, got an order confirmation by return but no mention of additional postage etc. I was expecting to have had a request for the excess postage by now and hope to recieve the kits in 2 to 3 weeks. So what was your time line.

i ordered my around the same time as Norman_E but had some phone calls with Mi Jung about the extra p&p. also mine was probally in a huge backlog as it's like boxing day here at my work. our security guy is like father christmas

 

[st599]

Now a question for the electronics wizards here. Should I make sure that components like resistors and capacitors stand a bit clear of the PCB, if so, by how much?

No, can be flush mounted.

 

[bitman]

Have fun! When I started this thread I thought it would interest one or two confirmed experimenters like me, but with over 2500 views so far it is now one of the most viewed threads on this forum, so perhaps lots of people are thinking of building the kit, or maybe just waiting to see how easy it is. As someone who had done no electronic work for nearly 50 years, I can only say that it is not too difficult at all.

the only thing i can say is that we might have a possible ultrasonic antifouling system for the price of hailing out + jetwash

you did just fine of building yours with great pictures.

i still do play with electronics as i'm a freelance sound engineer and also like modifiying things (like mod a scanner to make it an ais receiver). even still have my 40mhz hameg scope!

a shame that i couldn't be more helpfull when you started building yours as i was off this forum over christmas / new year.

 

[st599]

A vital point is the correct identification of the components, and the Jaycar instructions do provide a component list with some identification guidance. Resistors are now tiny things compared to the ones of my youth, and an illuminated magnifier was invaluable in identifying them, as was this website. http://www.diyaudioandvideo.com/Electronics/Color/

Can't see any tiny ones in the picture - have to solder 0402s at work http://articulationllc.home.comcast.net/~articulationllc/ReflowPics/0402.jpg

 

[bitman]

Now a question for the electronics wizards here. Should I make sure that components like resistors and capacitors stand a bit clear of the PCB, if so, by how much?

No, can be flush mounted.

i always leave a bit of room (couple mm) between the resistors and the pcb for heat but flush mount the capacitors if they are big ones with some glue of a glue gun to secure them.

 

[haydude]

Not suitable for foam sandwich?

Just a question, it says it is not suitable for foam sandwich, but almost every AWB built in the last 15 years is foam sandwich.

 

[Norman_E]

Just a question, it says it is not suitable for foam sandwich, but almost every AWB built in the last 15 years is foam sandwich.

Not true, decks are often foam sandwich or balsa cored, and many boats have foam sandwich above the waterline, but most AWBs by Beneteau, Jeanneau, Bavaria et al are plain and simple fibreglass layup below the waterline.