Transducer Fun - How would you handle this ?

[SailMaster]

Hi guys,

We are continuing our refit of Thalassa. She is a 1973 Nordcantieri Koala 38. I know you have not heard of this make as they appear to be no longer in business.

We are going with Raymarine ST60 series depth and speed gauges for replacements of what appear to be the original dinosaur era gauges. I spent a few hours, surgically removing the original depth transducer which appears to be about 10 pounds of pure brass. It leaves a 5 inch hole for us to contend with prior to installing the new transducer which only requires a 2 in hole

Our boat yard has a few ideas. I would like to know how you would handle this roadblock while maintaining original hull integrity. The pictures tell the story.

Thanks in advance,

Walt

 

[Sailvayu]

Wow that is an impressive hole for sure! If it were my boat I would glass it back in properly and then just redrill for the new ducer. It also looks to be at quite an angle, you may need a fairing block or mount it in a flatter section. Being a few feet farther aft will not matter as with the forward movement of the boat it will not matter that much.

 

[kenn]

Yeah - either 'glass that old up properly, or enlarge it for dropping mines, launching minisubs, diving bell, etc.

 

[RAD88]

internal transducer

I would also glass up the hole but I would not redrill . I would install the new transducer on the inside. I have not done this yet but I hear it works perfectly and no worries about leakage. The only reason this will not work is it the transducer has a paddle wheel for speed.

 

[MrBill_FLL]

yep, no need to drill at all.

you can mount it with a toilet wax ring, silicone, (temporary) or epoxy once you know it works. (just no bubbles in the mix)

it works fine for under 300'

+ bet you'll sleep better without that huge hole in the boat.

 

[kenn]

I would also glass up the hole but I would not redrill . I would install the new transducer on the inside. I have not done this yet but I hear it works perfectly and no worries about leakage.

It works as long as you don't have a cored hull.

I did this on our boat - we have a Raymarine ST40 depth sounder with a Airmar thru-hull transducer. It's a trailerable boat so i didn't want to have things sticking out. So I put the transducer in a baggie filled with water, moved this around the hull interior to find a spot that works, then constructed a small "tank" for the transducer which I fill with water (some use oil or anti-freeze)

Some report success with just epoxying the depth transducer to the hull.

 

[arf145]

I'm one who used wax (as in the ring used to seat a toilet) to seat an in-hull transducer 5 years ago and left it in wax. Has always worked perfectly.

 

[Ken Cross]

Ours is still mounted in wax. It seems to work down to 600 feet or so.
Ken

 

[rgranger]

That is a nice thick hull. Got to love those '70s era boats.

I'm wondering about how well a transducer can shoot through a hull that thick. I guess you can try it and if it doesn't work, drill in a hole at the next haul out. (?)

 

[Anonymous 121765]

Sail,

The guys had good suggestions and all would work for you.

However, if it were me, I would re-install it & forget about it. You can either caulk or epoxy it in. Only, however that you have room to mount an in hull transducer like Mr. Bill said.

Then you don't have to worry about the big hole with all the little holes pal.

CR

 

[Chris Patterson]

I'm with Wayne. I don't see HOW the transducer could work at that angle. It could tell you how far away the lee shore is..

 

[Merlin Clark]

Usually I'd grind/feather it back to a 12:1 determined by 1/2 the thickness of the hull for these heavily built boats, lay in increasing circles of glass/epoxy but you don't have the space for this on the lower/forward portion.
Might rabbet the edge of the hole, something like 3/4" wide, half the depth then lay up a glass/epoxy plug (stepped to match the rabbet) which would be epoxied in place, faired and barrier coated.
I would, like the other responders, find another place to mount the transducer. I like the 'ducer as far forward as possible but it doen't really make that much difference. Mounting it level with the boat and keeping it in the water is more important.

 

[Ross]

I would restore the hull with new glass and resin. I would work from both sides. The long tapers are not etched in granite and are just the ideal. Stopping the grinding at the turn of the hull and extending along the turn of the bow would allow for laying in a strong repair. As far as the location of the sonar transducer. I always point my flashlight in the direction that I wish to see.

 

[tomgrigsby]

If money is a consideration, reinstall the transducer to plug the hole. Put the new transducer in a better spot so that it points down instead of to the side