Just a quick question. A 3 piece carbon mast - 14/12/10 sections. How much of the 12/10 sections should project onto the larger piece below? 50mm enough?? Then tow wrapped around the larger section to reinforce?

One final thing - no height limit for the mast - just the 1806 between deck and bottom of top band so if you want 50mm above that, say, then no reason why not?

Many thanks

Hi Simon

My recollection of Engineering 101 was that, other things being equal, a "sufficient" overlap should be at least 4 times the diameter. No limit on mast height. Unwanted drag a good reason to keep it as low as possible.

Thanks Lester, would that be internal diameter or external?

Diameter at the overlap, I believe.

If this is for a six then a lot of them are using 12 mm for the whole mast and stffening with 10mm at the base I tend to go roughly halfway between the spreaders and gooseneck with internal 10mm, but I do like a fairly stiff mast, remember you also need to ensure the mast does not rotate and exfra thickness at the bottom gives you a bit more meat around your desired locating point/method

I had the 12mm mast option but ditched it when I looked at a mast drawing showing the 3 piece mast so took my 2m length of 12 back and replaced it with a 1m length and a 1m of 14!! I had 2m of 10 for booms so all was catered for!!

So, Lester the overlap of 12 and 14 is 56mm then ? That’s fine - as long as I know what the accepted ‘normal’ is !

3 hours ago, SimonCornes said:

So, Lester the overlap of 12 and 14 is 56mm then ? That’s fine - as long as I know what the accepted ‘normal’ is !

Hi Simon

I think the 12 and 14 overlap is at a dia of 12 (outer for the 12, inner for the 14), so I guess an overlap length of 48 would be considered "sufficient". (Never did establish exactly what was meant by "sufficient"....)

Thanks Lester, so 48 for the 14/12 overlap and 40 for the 12/10 overlap?

As long as it doesn’t break! As it is I’ll have to sand down the smaller section a bit as it’s already pretty much an interference fit and if I’m using thick superglue and I’ve been told to keep turning as I feed the smaller into the larger then an interference fit is too tight and I might end up with only 10mm inserted if I’m not very careful !! 😂😂

Edited December 21, 2025Dec 21 by SimonCornes

Would you still need shrouds on a 6m rig like this?

8 minutes ago, Gary Dickens said:

Would you still need shrouds on a 6m rig like this?

Yes you would, just one pair.

For those looking at this when you buy your carbon tube a number of suppliers will sell matt or gloss finish, the gloss is exactly the same tube as the matt with a gloss coating on top so is oversized, if you want a reasonble fit buy the matt and make sure both diameters come from the same supplier, makes life easier and whilst it is very small, uneven sanding could make a difference to the bend characteristics of the mast

Thank you Mike, I had no idea that the tubes were produced that way!!