From the beginning Sealegs boats have been fitted internally with standard wire braid hoses. These hoses are sprayed with CRC Soft Seal spray (or similar) to afford some protection from salt water. However many hoses run through the boats bilge and are constantly exposed to salt water. Inevitability salt water gets through this protection, corrosion begins and eventually hoses burst, (Note - the hoses outside of the boat are stainless steel and don’t have this problem). Consequently the recommendation from Sealegs is to check the integrity of all hoses say every 4 years and to replace all hoses every 6 years. Unfortunately checking hose integrity is pretty much impossible as they are routed through impossible to access parts of the boat.
But firstly a little bit about thermoplastic hoses and their advantages which are:
Infinite life span – Under optimal storage conditions a fluoropolymer thermoplastic hose will last almost indefinitely.
Over 5 times the pressure capacity – thermoplastics are an extremely strong material which is why even currently most rubber hydraulic hose connections are made from a thermoplastic. They can hold up to 4000 bars of pressure (58,000 psi) in comparison with rubbers maximum 700 bar of pressure (10,000 psi).
Increased internal fluid efficiency – Thermoplastic materials are inherently smoother and stronger than rubber materials. This gives them several advantageous properties such as being 3X more abrasion resistant as well as far more noise reductant.
Lightweight and compact – The manufacturing of thermoplastic hoses results in a highly compact outer diameter. The result is that thermoplastic hoses typically have 20% smaller outer diameters than rubber hoses and can be up to 70% lighter.
On top of this, thermoplastic hoses can achieve an inner diameter as little as 1.3mm which is 27% smaller than the minimum inner diameter a rubber hose can achieve making them particularly useful in applications where only a small amount of fluid needs to be transferred.
Replacing the hoses “opens up” the hydraulic system which leads to an increased risk of introducing contamination into the systems. Using thermoplastic hoses that last the lifetime of the system eliminates this risk.
In fact it is hard to find any reasons not to switch to thermoplastic hoses. It also should be noted that thermoplastic hoses are already standard on some other amphibious craft from non-Sealegs manufacturers. So going forward Waiheke Central Marine will be offering (in fact strongly recommending) thermoplastic hoses to all Hauraki Gulf Sealeg owners when it comes time for a hose replacement.
Then hopeful this will be the last hose replacement that they will ever need to do!
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