I've recently begun upgrading my masts to 90-100% carbon content, having experienced first-hand enormous benefits that make the extra cost worthwhile. As an average Joe freerider I have no intention of buying carbon extensions due to their high cost, but I was just wondering whether there is potential to damage a carbon mast when using it with an aluminium extension?
I assume that an aluminium extension is 100% rigid with no flex. I also assume that an advantage of a carbon extension when used in conjunction with a carbon mast is that it will flex, hence perfecting the curvature of the full length of the mast how it was intended, to maximise the performance of the sail.
Does the bottom 20-30 cm of a carbon mast flex? Does a carbon mast extension flex? If they do flex is there potential for damage using an extension that presumably doesn't flex?
It's just not a problem. Been using alloy extensions and 100% carbon masts for years.
RDM or SDM? Don't think it matters anyhow.........
All the answers above are correct. Also, bending forces are the least on the ends, the most in the middle. Almost all the force on an extension is in compression (downhaul). Think about it: bridges (sticks, toothpicks, etc.) fail in the middle, not the ends.
Alu ext is good - will not snap like a Carbon ext - you can still sail back home though it would be bent, but with snapped Carbon it is gonna be a swimming case. And Alu likes Carbon - so no worries 
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Select to expand quotesailquik said..
It's just not a problem. Been using alloy extensions and 100% carbon masts for years.
RDM or SDM? Don't think it matters anyhow.........
What he said.
write this dude.
david@ezzy.com
Select to expand quoteFarang said..
Alu ext is good - will not snap like a Carbon ext - you can still sail back home though it would be bent, but with snapped Carbon it is gonna be a swimming case. And Alu likes Carbon - so no worries .
Spot on Farang! I had a big crash and snapped my carbon RDM extansion luckily I could walk back instead of swimming in the sea.
Ditto,
Carbon looks cool but ally cheaper and more reliable... bugger all weight difference and it is in a location where it doesn't matter anyway.
Never had a carbon break on me, but had both SDM & RDM aluminium extensions snap in half. (I qualify this by saying the extensions both had excessive chalking /corrosion at one length I had it set at fairly consistently). Carbon can /does induce galvanic corrosion in aluminium but all in all it's not a major concern.
BTW Still could sail the board even if with some difficulty (although it did damage inside of mast sleeve at base)
Never leave your extension in the mast for storage though.
Corrosion will occurs and damage the mast.
Select to expand quotejusavina said..
Never leave your extension in the mast for storage though.
Corrosion will occurs and damage the mast.
Yep, even after leaving my gear rigged for a long weekend the Alu extension came out of mast slightly pitted, ie. small corrosion spots all over it. 
