Delimma in the toy box: seeking suggestions

[Page 83]

Page 83 is still out of the water and I have a decision to make. I bought an Interphase TwinScope forward scanning sonar last year intending to mount it on a swing-down post hinging from the back of the trampolines. The transducer is huge, almost the size of a squashed grapefruit. My thinking was that I would only use it creeping into shallow creeks and over sandbars, then raise it out of the water when I wanted to go fast. Make that relatively fast.

I'm having second thoughts. Since my new electronics suite is coming together now, it would be a good time to get this ducer mounted and wired, but there's not enough time to get the dipping mechanism thought out, designed and built.

Help me think this out. Should I go ahead and drill the big hole, mount this great lump of drag on the port hull in front of the mini keel, and teach it to play with all my other new toys, or wait another season to add another 30 pounds to the world's most overloaded PDQ 36. How much of a loss of performance do you think a permanent underwater mount would cause? Would it disrupt water flow around the root of the keel?

[amytom]

To be honest, if I were to ask the same question, you would have been the person I asked. I am drooling though, let us know how well it works.

[eepstein]

I'd mount it to the dinghy and a car battery, and play with it first. Then if its not all you thought it was, there is no hole on Page 83 to plug or other electronics to untangle. I'm envious too...

[thinwater]

A line to each bow (beam end?) and lash it (or other mount as apropriate) to a boat hook and stick down at the back edge of the tramp. a few feet below the WL?

I like your first idea; perhaps I would hinge it forward, pulling it up with a tackle, but letting the pressure of the water press it back into a hinge/socket.

The only way I would consider a hull mount is if I was going to fabricate a well-faired home for it, yes, just in front of the keel. I doubt it would function elsewhere.

[SeaPaws]

Did you get the color version? I have the older B&W on our boat. I have used many recording depth finders for hydrographic surveying and was anxious to use the forward looking feature when we got our boat. BUt it doesn't really look far enough unless the water is deep. I haven't found a great advantage to it but it is neat to watch and I must have a recording sounder instead of just a digital readout. I have always realized that the history of what you have been over is a great tool to "see" what is below and even tell the hardness of the bottom.

On the mounting issue, I have temporarily mounted many transducers on all types of boats. Must be secured well to stay in place, we would often just have them over the side on some type of pipe or something with a line from the ducer going forward and up to the bow for support.

When are we gong sailing, SandY?

[Page 83]

Hey Chester! Good to hear from you! This is the original 6.5" transducer with the monochrome dualscan instrument, like yours. I Got it off the bargain table at West Marine for about a half a boat unit. Yesterday I ordered the SC200 box so it will display in color on my Garmin 3010C chart plotter. I also ordered the 4" tall fairing block for it so it can be mounted a little off to one side of the hull, causing less disturbance around the keel. Its a chunk of plastic that can be cut to fit the curve of the hull; one half outside and the other half inside the hull to keep the ducer perpendicular with level landings for a firm attachment. Add a little Chesapeake Bay vegetation and it becomes a big hairy mole on the chin.

I've finally put my 700 pound gorilla (AKA 5kw Westerbeke Generator ) on Craig's list. Please, everybody, cross the fingers of one hand for me!

Jose' got me off bottom dead center on the project, and I'm geting stuff done.

[maxicrom]

Sandy,

Did you ever see my old trolling motor mount before I installed the Torqueedo motor. I used a swivel antenna mount with a 3/4" bronze coupling to the top of the trolling motor rod, it was a 60 ft lb trolling motor driving the Stbd hull on that mount (I don't think a transducer will tax it). You just swivel it down and clamp it in, the mount comes with 2 mounts (one for up and one for down). I through bolted the mount and clamps to the hull and it worked great. The only issue might be for reaching the down position and clamping it. I used to lower the motor from the aft steps. I still have the old mount if you want to try it.

Mike

[Page 83]

Thanks everyone. I spent some time at the boat with "Mr. Transducer" who advised mounting the ducer on centerline of the hull as far fwd as possible. His position is that the flow behind the ducer, at speeds under 16 knots will normalize when the unit is mounted as far forward as possible. That will be at the bulkhead in the hanging closet, just as are the transducers for the ST50's. He also pointed out the the foil section on the mini-keels are not optimized for laminar flow, (too fat) brobably because at 18" depth the water is turbulent from surface wave action. That way they still provide some lift (like a mushing stall in a light plane) at higher angles of attack. That was a lot of information!

So unless someone points out a grave error in this thinking, the fairing block goes under the knife on monday.

CK: when do I get my Operator's Training on this toy aboard SP2?