Casting Resins

[Brad]

Does anyone know if there would be a problem using a vinyl epoxy resin for casting ducers? Something like West Systems 105. http://www.concentric.net/~westsys/index.shtml Its the type used in fiberglass repair, and boat construction. At room temperatures it has the viscosity of warm syrup. The only drawback I can see is it's rather permanent. What I don't know is how it might alter ducer properties. People fire ducer 's through boat hulls every day without problems, and its the same stuff. Also does anyone know a good source for waterproof connectors that could be used to connect tow cable to fish?


Thanks,


Brad

[Bob]

Re: Casting Resins

Hello everyone, sorry I've been away for a while..


About using resins, I got a call recently from a Conap representative, about using Conathane EM-9. He said that for all practical purposes, you need to use a precision scale and a vacum pump for good results.


I said this was expensive, but he told me about a small company nearby that used EM-9 and had all of the needed equipment. (as well as experience) I am wondering if anyone has a transducer design they like and are willing to share.


If so, I may try to use EM-9 and work with this local company to do the EM 9 pour. I will let you guys know about all of the "tricks of the trade" I find out about.


(For those that haven't read way back in the postings, EM 9 is a resin that is hard to work with, but acoustically matched to water, so it appears transparent to the ultrasonic waves)


-Bob

[Tod]

Re: Casting Resins

[Tod]

Re: Casting Resins

Hi Brad,


You have to be careful of exothermic reaction of laminating resins. You should really use a potting resin and one with the same density of water like EM-9 or else you have to be more actuate with the thickness of the window. See Sture's discussions on windows "Materials for transducers" . I saw some waterproof connectors in the Newark electronics catalog.


Regards,


Tod

[Bob]

Re: Casting Resins

Tod,


Thanks for your reply. I looked at your message and pictures for a long time, but I am still a little confused. Let me try to play back what I think you did, and you can tell me if I have it right..


First, you covered 3 sides of the piezos with the 3m foamy stuff, which acts as an insulator, and is an alternative to cork, which will react with EM-9.


Then you put the pieces in the slotted aluminum fixture. Then you turn this fixture over, and put it in a layer of waiting EM-9 in the black Plexiglas tray.


When this cures, you put the curved aluminum piece on the tray and fill it with some material. More EM-9?


Some questions:


I am not sure where in the process you added the connectors. I saw you using the eraser to get a good connection, but the prepot picture doesn't show connectors, yet after the first part is done, there are wires there. Also, have you thought about the possibility of the metal conducting ultrasonics?


It looks to me like the Plexiglas tray is used permanently. If this is so, then the ultrasonics need to go through the Plexiglas. Can this cause interference? If I'm wrong and the Plexiglas tray is removed before use, how do you prevent it from sticking?


For the back potting, are you using EM-9? I would think you might want to use something that was more absorbent of ultrasonics, not to mention easier to work with. Sture's 'Corkopoxy' perhaps?


What frequency did you end up going for? What were the dimensions of the piezos, and the material that was used? (I spoke to Harry Sharry once or twice, and he said he could make piezos up to 4 inches long. Do you think that would help make things easier to build?)


Do you have an idea of how much all this costs per transducer array?


Thanks,


-Bob

[Brad]

Tod - Please Email pics

Tod,


Could you email your ducer building pictures to help me understand the process.


Thanks,


Brad


[email protected]

[Tod]

Re: Casting Resins

[Mike]

Re: Casting Resins