dumb sonar question

[Joe Lambert]

has anyone had experience mounting depth sounders in full keel sailboats?

What's the best way to mount the transducer?

Of all the stupid things to be puzzled over..

[Donn]

It's not a dumb question at all, and it's an interesting issue with sailboats. You have to mount it where it won't have it's beam blocked by the keel when you're heeling. You can mount it forward of the keel or on the transom, but you have to be sure it's perpendicular to the surface of the water, and not flush with the hull.

An interesting question arises regarding the accuracy of the measurement when the boat is heeling. The 'ducer won't be shooting straight down.

[CarlZog]

I have a hard chine, full keel boat, and my boat's previous owner solved the transducer problem by mounting it so far outboard (away from the keel) that it's out of the water when the boat heels over even 5 degrees!

But since I only draw 3.5 feet, it's pretty low on the list of projects.

Carl

[Gresham CA]

Most of the ones that I have seen are mounted forward of the keel and just slightly off center. They use a fairing block that allows them to be mounted as Donn said. With the cone angles there should always be a part of the signal that is straight down.

[JimConlin]

I recollect that the cone angles of these things are among their published specs. Pick a location such that the keel is not in the cone, it's in a spot that's immersed as much of the time as possible and fairly far forward forward, so it's in laminar flow and gives you have a bit more warning.

[paladin]

Mount two transducers, either side, on fairing blocks, about a foot away from the keel so that when the boat is heeled about 10-15 degrees the transducer is looking straight down. They should be mounted about 1/3 rd of the way back from the stem...the two cables are then run to a relay or switch, which is activated by a mercury switch mounted horizontally with the ends facing either side of the boat...as the boat heels the correct transducer is selected....

[Joe Lambert]

The problem I have with fairing blocks is that this is a really sweet old racing hull with some of the purest lines you've seen. It just seems like putting a big block of wood somewhere on there is somehow sacriligous.

Has anyone tried something really far out like mounting it in the ballast or perhaps on the front of the ballast and running the wire up the front of the keel until you could bring it inboard?

[Excalibur]

No, but I have mounted them inside the hull of plastic boats so that they shot through the hull. Can you put a plastic fairing on the leading or trailing edge of the keel and shoot through that?

[Gary E]

If your in a sailboat and it's healed over so that the beam is pointed at some angle that may give you a false sense of actual depth arnt you sorta really haulling A$$ for a blow boat so ta speak? I would think so. Now ifin your haullin A$$ arnt you likely in deep water? where you KNOW you can go where ever the wind blows ya? Now ifin your in skinny water and haullin A$$ arnt you really STUPID for doin that? So why bother with a double transducer dealie and why bother with worrin about settin it for whatever kaddywhompus angle your boat might be leanin to? Pay attention to your charts and or the fancy GPS chart combination thingie so you know where you are.

[Dan McCosh]

It's a little tricky. Sound propagates as a sphere, which means that a transducer doesn't actually "aim" the sound wave, and even when a boat is heeled over it will still read the same distance to the bottom. The angle of operation is actually the angle of reception, not something like a searchlight you aim. The shadow of the keel can block part of the signal, however, hence it's theoretically best to mount it ahead of the keel. (behind could work, but you probably want it as far forward as possible. I've had it mounted through the hull close to the leading edge of the keel, where the keel is still fairly shallow, and it seems to work fine.