RDM mast extension, 42 or 28?

[barrowboy]

Just wanted to know what people's thoughts are on how much mast extension is ok to have inside the mast?

The reason being I have just bought a North Gold 430 RDM mast to work on both of my North Duke's. Both are recommended using a 430 and decided to go for a 42 North UNI.XT Extension. The maximum extension I will use is 24 for my 5.9, which is around halfway, so half the extension will be inside the mast. On my smaller sail I use 10 on the extension which means two thirds of the extension is inside the mast. I didn't go for a 28 as I thought it doesn't leave much extension when using on my larger sail. Also read about not having much extension inside a mast leaves it prone to snap, but also using a too larger extension can cause issues with how the mast flex's. At the moment haven't got any more cash to buy another extension, but would the ideal situation be to have a 28 extension that runs on the 5.4 and use the 42 solely for the 5.9?

[Distinctly Average]

I would be happy using the 28 with both sails.

[Asle]

No problem with 28. I would never buy the 42 and just use it from 24 and under. Then I would go 28 all the way.
I think the common agreement between hard core wave sailors goes at 30 cm of extension at the most, that means if you got one with 30 cm max you can use it at 30, but if you got a 42 you will still not use it over 30cm.

But, of course it is not just cm, the quality of the extension at hand is also important.

[barrowboy]

Thanks. So basically mast extensions over 30cm are a no go then? The extension is North and I think its aluminium.

[basher]

The general concensus is that RDM masts extensions aren't to be trusted on full extension – compared to SDM ones – due the inherent fragility brought on by such a small tube diameter.

I try to restrict my RDM extension use to 20cms.


If you are worried about needing enough extension up the mast when using 24cms on a 30cm extension then I would say that is fine.


All that said, I use a Chinook carbon RDM extension which goes to 32cms – which means you have a bit more of the extension inside the mast when it is set on say 24cms or more.


When they break however it is usually halfway between the mast foot/UJ and the bottom of the mast. Aluminium ones tend to bend in the same place.