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What I’ve learned so far.
Conathane EN-9 is very difficult to work with as Sture said. My first transducer was wrecked because I used the wrong mold release. It was a wax based release I used for urethane foam, The part came out just fine but had so many bubbles it looked like foam. Silicone based release is the right stuff. My seconded ducer was no good for the same reason, bubbles, this time the culprit was the cork. I found I could use a foam made by 3M. I don’t know the name but it has adhesive on both sides and measures 1.5 wide by 0.056 thick. Another problem is moisture. You should preheat the oven and the molds to 175 f before potting, this removes the moisture. EN-9 is heat cured and has a shrinkage of 1.15%, but before it shrinks it expands (do to the foam), make room for the expansion. You half to degas, so you need a vacuum pump and chamber. My 3rd ducer went together well, the only problem was I went to fill a small hole in the urethane and tried to mix a small batch but it’s hard to weigh and it didn’t cure, even at 200 f. By the way when placing piezo crystals in the oven, join the wires together. Or else, ZAP OUCH sh**! I have a new dent in the side of my computer. OK, the results are in, I got out Sunday late afternoon, big waves (for a 14’ Zodiac) but got to my buoyed wreck, set up the stuff and throw it over. After two hours of tuning and making passes past the buoyed wreck all I could see was the bottom but not much more. I had better results with a single fish ducer on the same fish. I think I need more power (what else is new). Zero to peek I’m getting 200 volts or 400 peek to peek. I tried tuning with an inductor but found I got the best results with tuning the on board inductor ( Raytheon was very good at supplying a schematic for the old DC 200Z fish finder I found at the junk yard). Now I feel like a ducer vet (after being ZAPPED real good) and want to take on the world
Pics to come when I figure out how to post them easaly.
Jan, how are you doing? I’ve been thinking of your needs for a fish (150x25x25) and if you can define any better the size of the cavity (dry zone) I’d like to sketch up some ideas. How about 25 high (board height) and something 5 or 10 wide and as long as you need for the boards plus batteries. Than you can pull the rack out from one end, this will make sealing the cavity a little easier. Put the ducers on the out side and all you need is a bulkhead fitting for them. The only other problem is good water flow over the ducer (not turbulent).
Tod
Conathane EN-9 is very difficult to work with as Sture said. My first transducer was wrecked because I used the wrong mold release. It was a wax based release I used for urethane foam, The part came out just fine but had so many bubbles it looked like foam. Silicone based release is the right stuff. My seconded ducer was no good for the same reason, bubbles, this time the culprit was the cork. I found I could use a foam made by 3M. I don’t know the name but it has adhesive on both sides and measures 1.5 wide by 0.056 thick. Another problem is moisture. You should preheat the oven and the molds to 175 f before potting, this removes the moisture. EN-9 is heat cured and has a shrinkage of 1.15%, but before it shrinks it expands (do to the foam), make room for the expansion. You half to degas, so you need a vacuum pump and chamber. My 3rd ducer went together well, the only problem was I went to fill a small hole in the urethane and tried to mix a small batch but it’s hard to weigh and it didn’t cure, even at 200 f. By the way when placing piezo crystals in the oven, join the wires together. Or else, ZAP OUCH sh**! I have a new dent in the side of my computer. OK, the results are in, I got out Sunday late afternoon, big waves (for a 14’ Zodiac) but got to my buoyed wreck, set up the stuff and throw it over. After two hours of tuning and making passes past the buoyed wreck all I could see was the bottom but not much more. I had better results with a single fish ducer on the same fish. I think I need more power (what else is new). Zero to peek I’m getting 200 volts or 400 peek to peek. I tried tuning with an inductor but found I got the best results with tuning the on board inductor ( Raytheon was very good at supplying a schematic for the old DC 200Z fish finder I found at the junk yard). Now I feel like a ducer vet (after being ZAPPED real good) and want to take on the world
Pics to come when I figure out how to post them easaly.
Jan, how are you doing? I’ve been thinking of your needs for a fish (150x25x25) and if you can define any better the size of the cavity (dry zone) I’d like to sketch up some ideas. How about 25 high (board height) and something 5 or 10 wide and as long as you need for the boards plus batteries. Than you can pull the rack out from one end, this will make sealing the cavity a little easier. Put the ducers on the out side and all you need is a bulkhead fitting for them. The only other problem is good water flow over the ducer (not turbulent).
Tod