Down at Inverloch Australia Day with new(second hand Radz Spyro 12 mths old) 490 mast and decided to set up the 8.5mtr sail. Had a ball planning in 12 kts. Anyway.....
Found that the design of the Chinook boom clamp could not be tightened enough to hold the mast. So I am assuming the mast is a RDM. Had a spare rubber insert for the boom clamp which I used as a temporary device to hold boom in place. Not a long term solution as either end of the insert has lip that was getting in the way of the clamp. Apart from buying a new boom, which I do not want to do, has anyone got any smart solutions.
Cant you just put one of the RDM adapters in. They usually are supplied with the mast but have bought them before from stores for about ten dollars. I use one with my fiberspar boom, works perfectly.
Could you use your normal mast extension with the mast?
If you could, the mast isn't an RDM - you need special extensions for RDM masts.
I'd be very surprised if you'd bought a skinny without knowing about it - they're seriously different to a conventional mast, and hugely expensive as well... Ezzy RDMs cost about AUD700 for a 400cm at the moment.
As for the boom-clamp problem, maybe take it into SHQ or RPS and get the lads to have a look. SHQ have loads of Pryde pads that they pretty much giveaway, if you have indeed got an RDM.
Just quickly looking at it over the weekend Old Salty, I didn't think it was a "true" RDM/skinny....just slightly more reduced diameter than normal 
Which doesn't help much. 
Hey Flicky Spinny
Up there for dancing. You are so right. My normal mast extension does fit. Therefore it is a SDM but it begs the question why do the mast manufacturers differ so much. Like we are taking at least 15mm dia different between the 2 masts
Hmmm - that's a big difference - especially considering that I believe there's only a couple of mast factories in the world. I've seen some pretty thin RDM mast pads before now (the Pryde ones are too thick for a 15mm difference I think)... in fact, Matt has a really thin pad that might do the trick if you could find something simillar.
Weird. Ah well, sounds like you've got a SRDM mast - Slightly-Reduced-Diameter-Mast - it's a new breed!
Good luck!
just as a bit of an aside you can get reduced diameter masts which use a standard extension. Not sure if they are still made but Naish used to make an extreme taper mast which was a normal extension but still required a boom shim as by the time it got to the boom height it was skinny diameter.
Could it be a relation to the North 'Drop-Shape' ones..?
They're SDM at the bottom (where the extension goes) and then taper in to a smaller diameter than normal (but not quite RDM). 15mm difference could be about right..
Maybe a shim cut from a section of broken mast could work? Take a ring of mast, cut a 5-10mm section out of it lengthwise, slip it over your not-quite-skinny mast, and clamp it on hard with your boom clamp? Same theory as a collet.
Thanks for input guys.
It is not a North teardrop shape , Its a Radz Spyro 75% carbon 29 ICMS, the mast it is replacing is a Sailworks 100% carbon 29 ICMS. Dia difference between masts is 10 - 15mm at the boom connection area.
Got down to SHQ this arvo in 43 c heat with boom and mast in hand. Found a suitable rubber sleeve to fit over mast and problem resolved. Thanks to all. Interesting observation is that the mast increases it dia dramatically in the last 450mm to fit a sdm mast extension. Thought I would pass it on for what it is worth.
North masts definitely use a slightly smaller diameter for the SDM's - the theory is that you get a slightly softer mast and slightly stronger. Its not a bad idea - although I think it might be more of a marketing gimmick; I have one myself -> works well for giving that little bit of extra twist.
You shouldn't specifically need a shim, as your boom clamp should have enough adjustment to fit the mast.
