Installing depth-finder in-hull

[Capslock118]

Hi There,

So we are near purchasing a 25' sail for the first time.

I've always had a depth finder on motor boats prior, generally more for the fish finder part though I can never catch fish

some depth finders allow the sonar to be installed inside the hull.

I am playing with the idea of installing a depth finder for the sail boat, again mainly for fishing and inside the hull rather than drilling through the hull to mount outside. But maybe this is a useless item and my meager budget would be better spent elsewhere.

what are your thoughts? do you own a depth/fish finder? if so, have you installed inside the hull? any problems come up doing that?

also, if installed in the hull, if I reversed the sonar so the part that is suppose to face toward the bow is now facing the stern, would I end up with readings ahead of the boat or is that not how it works?

it would be good to see depth ahead if that's how it works.

[QuickMick]

I hooked up my hummingbird this way, works like a charm. i put it in a bag of water(which im not sure if you need to do) and moved it around till i liked reading, removed from bag and epoxyed it to the fiberglass (after a decent cleaning), when i pushed it down into the epoxy, i kinda used a twisting motion to get rid of any bubbles. there is another method with mineral spirits filled pvc but i didnt go that route. what your boat is made of is a consideration, as well as not forgetting to offset the unit to keel depth.

mine is in the engine compartment, but i use that unit primarily for fishing from the cockpit, and do have redundancy via thru hull unit. if you are worried about grounding id put the transducer toward the bow to 'see' what is in front of you.

good luck

edit: while i maybe off base, i believe the number of 'beams' affects size of area you can view-spinning the transducer wouldnt affect the range, persay just make everything on the scrolling display be backwards... i think~that last bit was giving me a headache... lol.

[copacabana]

Rather than glue it with epoxy, you can use silicone. The advantage of silicone is that you can always remove the transducer at a later date or move it to another place. It has to point down to read the bottom (ie. in the same orientation it would be in if attached to the outside of the hull). It won't read ahead of the hull. You can try installing it ahead of the keel, but the millisecond warning it will give you before you run aground won't do you much good. It's best to find a place that has no turbulence and won't be out of the water when heeled over. I installed two in my boat and both work fine. Don't drill holes in your hull if you can avoid it!

[Faster]

Forward looking depth sounders are available, but are pricey, use bulky transducers and are not 'the norm'.

Generally your depth indication is going to be whatever's directly below the transducer, wherever that is. Most are mounted ahead of the keel to give you a (very little bit of) warning, and only if you're going very slowly. Mounting ahead of the keel also minimizes interference from vortices and disturbances to the water that can confuse the sounder (as an example watch your sounder readings anytime you're reversing at some revs, or if you're backing down hard... the number is often all over the place)

Epoxy, silicone, or liquid cavity mounts are ways to mount inside the skin of the hull. I think it works better in single skin hulls vs cored hulls, and you will lose some range but it does avoid the issues with adding a through hull fitting.

A transducer intended as a through hull will probably need to be mounted in the lid of a liquid cavity style installation.

[mitiempo]

They will not work in a cored hull, but even cored hulls are usually solid fiberglass along the keel. Any epoxied transducer can be mounted inside. On my current boat I installed a Raymarine ST-40 and it comes with an Airmar transducer designed to be mounted in a drilled hole. I just removed the nut and gasket and epoxied it in. I installed it under the aft most part of the V-berth, on the centerline. You will get less disturbance in this location. As posted above place the transducer in a baggie of water and check that your chosen location works first.

[Joesaila]

I gonna do this! I want to connect it w my garmin chartplotter w/o drilling another hole in the hull. The original digital unit is only about 90% correct. It seems to blink off at the most inconvenient times. THANKS FOR THE GOOD POINTERS!

[mitiempo]

YOU"RE WELCOME

[sailor50]

This months SAIL MAGAZINE addresses this issue right to the point.

[mitiempo]

It is also addressed here: WEST SYSTEM | Modifying and Customizing Boats - Depth sounder installation

And as they state most manufacturers of depth sounders recommend epoxy for installing the transducer. Less chance of bubbles.

[Faster]

In a somewhat related question:

We've recently upgraded to a compact plotter/depthfinder and we already have an aging but functional Signet DS. I'd like the expanded features of the newer/smarter depthsounder capabilities, and the internal install has appeal for obvious reasons.

Anybody think there would be cross-talk between two simultaneously operating systems? The new one has selectable Hz settings - should I make them different? I'm thinking of mounting them some distance from each other.. Any thoughts?