through hull transducers

[Guest]

Could anyone please detail the risks of installing a nylon transducer in a wood hull?
I bought an ST40 speed and depth transducer for my sailboat only to find the hard way - after received and customs paper work - reading on the installation manual "never install in wood hulls". West Marine's catalog did not mention the need for the optional bronze type.

Thanks,

 

[Dipper]

The risk is you will sink!

Wood expands and contracts and the plastic transducer/through hull mounting can't take the strain and will crack. I'm afraid you will have to buy the bronze transducer.

 

[Mirelle]

I've just been puzzling over this one myself, having finally removed the ancient Seafarer 3 and replaced it with a Simrad one. The Seafarer, which had been in the boat for a quarter of a century, had a plastic transducer; the Simrad needed an expensive bronze one!

It seems plastic is not what it was!

 

[Dipper]

I guess it is a matter of risk. There is a possibility that the transducer fitting will crack but as you have found out, it might not! It might also depend on how wet the wood was when it was installed and how tightly it was fitted.

 

[Guest]

Precisely what I was afraid of: cracking and sinking!

On the other hand, Mirelle mentions her good experience with a quarter century plastic transducer. What do you precisely mean by how wet the wood is at installation and how tightly fit?

Yes, it is better not to take the risk, but if I cannot find a way to return the plastic ones and import the bronze....

Thanks again,

 

[Sniper]

I think there's another dimension to this that you ought to consider. I, too have had plastic transducers fitted through hull in my wooden Twister. However, they have been seafarers and have a relatively small body. Because of this, I believe they are better able to withstand the compression stress of wet wood, especially as the hole diameter is small. I think the one you are considering is of a substantially greater diameter, so you should perhaps consider the risk of cracking under pressure to be greater.

The other factor - if the boat is in commission (or newly out of the water) when the transducer is fitted, then the wood will not expand and crack the transducer as feared. Beware of fitting if the hull has dried out.

On balance, if I had the choice I'd play safe and fit the bronze one - cheaper than a sunk boat!

 

[Dipper]

I must point out that I am not an expert on this! I am on the wrong forum ( I've got a pl*st*c boat).

However, wood will expand when wet and contract when dry which is what causes the stesses on the transducer. Thinking about it, as the wood expands, the hole itself will expand rather than contract. Although this seems the wrong way round I think that is correct - any engineers out there to advise? So it could be that the cracking occurs as the boat dries out.

If you fit the transducer in a slightly oversize hole with generous helpings of sealant, you may be able to avoid any compression on the plastic. Another idea, depending on the location of your transducer, is to cover it over with a waterproof box with an access lid (and waterproof exit for the cable) so that IF it did crack and leak, the hull would still remain watertight. Or you could build up the sides of an open box or tube around it to a level well above the waterline. This is all a bit Heath Robinson but it would provide a secondary backup in the event of leakage.

Or you could get the bronze transducer......!

Best wishes and happy sailing.

 

[muchy_]

All you have to think about is sitting in that inflatable, watching the upturned bow of your boat dissapear beneath the waves and thinking "BO**OCKS" wish I'd paid the extra and done it properly

 

[Plum]

Might be worth checking the inside diameter of the plastic skin fitting and see if one of the standard bronze skin fittings from a chandler could be bored out to the right diameter to accept the existing transducer.

 

[anmarine]

I'm affraid you will have to cough up and fit a bronze one. Plastic ones do split, belive me, it's not worth the risk. No insurance co. will pay up it it all goes wrong.
Your boat is an expensive item dont risk it for the sake of a few quid.

 

[Guest]

Thanks to all who replied to my post and from your answers I guess I should try again to replace the plastic ones with bronze.

 

[spark]

Fit the plastic into a bronze plate and then fit the bronze plate to the hull?