Thru-hull Transducer: Is this a dumb question?

[Jim Cate]

Originally Posted by Kiwi399

Ok Jim, 21 years is a good long time. I don't expect you to write a novel, but I would be interested if you could quickly explain when you get a moment how you put yours together to provide such a flawless experience with your thru-hull for such a long time, because I have to say some of the scare stories do not equate with your experience.
I see your boat is in Hobart. Beautiful part of the world, I have been there (as a tourist, not as a sailor).
Cheers mate.

Fairly simple process: drill or hole saw hole, soak exposed timber (Western Red Cedar) with epoxy, apply copious Sikaflex 291 or equivalent sealant, install fitting, don't overtighten and crush the timber.

I suspect that the scare stories refer to timber construction that is open to water, and where repeated immersion/drying out cycles with their expansion/contraction of the timber has loosened the fittings.

I make no claims to expertise on traditional timber boats... never have been associated with one. Yours, being sealed on the outside is kinda in between. If you keep dry bilges I would think that the timber would be as stable as mine is.

Cheers,

Jim

[SVTatia]

Originally Posted by Kiwi399

...So--why can not one build a little solid fibreglass "box" with a watertight inspection port/plug over the thru-hull, meaning that if the little f**ker ever failed, then your "safety box" over the thru-hull saves your boat from sinking, working like a watertight bulkhead does in other areas of some boats....

This is what I have on my boat - it came with it, and it looks like the original transducer was mounted inside, and a subsequent owner replaced it with an exterior unit. The box has an inspection port on top and there is a watertight gland leading the cable thru the box. This is not a bad arrangement, and if you have a speed unit you may want to do do the same, but on mine, it is mounted forward and there is no clearance room for a box.

[LBW399]

Originally Posted by Jim Cate

Fairly simple process: drill or hole saw hole, soak exposed timber (Western Red Cedar) with epoxy, apply copious Sikaflex 291 or equivalent sealant, install fitting, don't overtighten and crush the timber.

I suspect that the scare stories refer to timber construction that is open to water, and where repeated immersion/drying out cycles with their expansion/contraction of the timber has loosened the fittings.

I make no claims to expertise on traditional timber boats... never have been associated with one. Yours, being sealed on the outside is kinda in between. If you keep dry bilges I would think that the timber would be as stable as mine is.

Cheers,

Jim

Hey thanks Jim.
I also see no reason that on that particular section that the thru-hull is to be located that it could not be glassed on the inside first as well.
Kia Ora mate.

[RaymondR]

Hi Kiwi399,

The thru hull transducers started to make me nervous a few years ago as it appeared that they were making the flanges on them thinner. I went down the same road as you and finally machined a housing from black poly. I have a steel boat so was able to bolt the housing inside the hull over the hole where the transducer had previously penetrated with six 8mm studs which are welded into the hull. Whilst there is still a hole in the hull rather than hull integrity depending upon a skinny plastic flange it now depends upon about 20mm of black poly which is protected from impacts by being inside the hull.

[roverhi]

Depthsounder transponder water proof integrity failure is such a low possiblity as to be a non issue. You'd have to ram something with the transducer and rip it off the hull. Same goes for the removable type as they are sealed with a plug. In either case, you'd probably suffer severe hull damage which would be way worse than the puka that the transducer would leave.

If you want to make yourself a lot of work, have at it. There are a lot of other things I'd worry about above the waterline before I'd waste any energy on a transducer though hull. The glassed in standpipe idea is probably the best 'solution' but will make changing the transducer a mother and intrude into the interior. When I say change, mean replacing the transducer because of electronic failure not water tight integrity.

[RaymondR]

Hi again,

perhaps I should also have explained that I don't use the expensive yacht type sounders with only a depth readout as they tend to be excessively expensive and I found them to be electrically delicate and experienced a burnout from voltage spikes in the electrical system.

Years ago I changed over to using fish finders as depth sounders. They are very inexpensive and I find that the nice picture of the bottom profile on the screen which shows the depth trend which is much handier than just a depth readout which requires a is-that-deeper-or shallower calculation.

Unfortunately, whilst they may be a more practicable device, fish finders usually come with a transom mount transducer and you have to purchase the thru hull as an optional extra. (It's also interesting to see the fish underneath you.)

The housing I installed inside the hull, in addition to relieving my concern regarding retention of watertight integrity, also allow me to use the transom mount transducer as a thru hull type and I don't have to purchase the optional one.

[Albro359]

Our yacht DIVA was built in 1974 ... she's triple skin kauri epoxy saturated...we have a depth transducer and a speed transducer in thru hull fittings...and they have NEVER been a problem....as a previous poster said....make the hole just the right size, plenty of good sealant, don't tighten them too hard, and they will be fine.

I am more concerned about the bronze thru hulls for the coolant water intake, sink drains, head etc.....but none of these have caused any problems in the 15 years I've owned that wonderful boat ....

Don't worry so much...do it once...do it right...