Bronze or plastic

[Leisure 27]

I am about to fit a through hull transducer to a grp yacht. Which is better bronze or plastic. Bronze sounds stronger but will it corrode. I now use a plastic exhaust as the stainless steel did not last.

 

[Stemar]

Bronze won't corrode, but brass will. OTOH, a bronze through hull will corrode your wallet. DZR is an acceptable compromise, but nothing wrong with a good plastic one, IMO.

 

[mjcoon]

Not sure why a "through hull transducer" would need to be especially strong. And per your aside, sounds like it might have been the "wrong type of stainless"; there is a lot of variation. Possibly Vyv Cox will be along to give us chapter and verse.

 

[steveallan]

I am about to fit a through hull transducer to a grp yacht. Which is better bronze or plastic. Bronze sounds stronger but will it corrode. I now use a plastic exhaust as the stainless steel did not last.

I fitted a NASA plastic through hull fitting for a log about 15 years ago still in excellent condition. The inside part is glassed in as per NASA recommendations.
The NASA transducer is bedded inside the hull with epoxy and work's to about 100 metres.

 

[Leighb]

I believe that bronze through hulls are advised for wooden boats, as timber can swell and contract, and if it swells it might damage the transducer, in GRP hull I would have thought that either would be OK.

 

[ctva]

I may be wrong ( an often am as wife tells me so) but plastic (or similar composites) may degrade in sunlight or UV. Not a problem for a through hull. As said above, metal for wood, either for GRP but pointless in the extra cost.

 

[Sandy]

I have a plastic hull why would I fit a metal through hull?

 

[Pye_End]

My DST800 said to use a bronze if using a fairing block. Otherwise plastic seems to be the norm so presumably this means that it has a low failure rate.

 

[Gary Fox]

I have a plastic hull why would I fit a metal through hull?

Why fit a metal prop shaft or chainplates?

 

[rogerthebodger]

Why fit a metal prop shaft or chainplates?

Because a plastic (GRP) prop shaft or chain plates will not take the stresses involved.

Some as a GRP engine would not take the stresses or heat involved.

With regard to skin fittings in GRP boats I don't understand why standpipes for water inlets or outlets are not included in the basic moulding process.