I won't mention the brand, but I've owned a 140-190cm Monocoque boom for two years. The mast clamp has given me nothing but headaches. Note: It's got an RDM adaptor, so it can clamp to a SDM or RDM mast. I use it with RDM masts.

The biggest problem (among others) is the clamp slips down, lowering the boom during sailing. Since owning the boom, I have used it with the RDM adaptor, which the clamp slips very badly no matter how tight the clamp is, and scratches the enamel off the mast. I have also used it without the RDM adaptor and with a plastic SDM shim. In this case, it doesn't slip as badly, but does slowly slip down over a period of a few hours. However, if I clamp is ready ready tight, it doesn't slip, but I'm concerned about damaging the mast. Just a couple of questions.

How much clamp pressure can an RDM mast take using a plastic or rubber SDM shim ? (Can I crank the clamp pressure without damaging the mast ?)

Does anyone have any opinions about this product for RDM masts ?:

www.surfsailaustralia.com.au/showProduct/Windsurfing/Boom+Max+Length+Up+To+200cm/tcwave/Chinook+Wave+Triple+Clamp+Alloy+Boom

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Thanks :)

Hi jn1. Have you tried the rubber rdm shims? Take the rdm adaptor off and use a rdm shim. I have been using the ezzy shims for the past 4 years and they work great. Nice secure fit, much better then the rdm adaptors that come with the booms, from my experience.

Agree with RDM shims.

The rubber grips the mast well, I used Ezzy (No Limitz) for ages and never had a slip, now use NP and likewise.

Since owning it, I've tried a rubber Mauisails shim and a rubber Severne shim. Both don't fit. I then got a plastic severne shim (which came with one of my masts last year). This plastic shim has a smaller diameter then my two other shims, and fits perfectly... but because it's plastic, it's probably still not perfect. I'll try sourcing a rubber shim. Hopefully it's diameter compatible.

Thanks all for your advices :)

Line the shim with a few lines of black witch (or any rubber/neoprene glue), never slips then and adds more cushioning. Do it diagonally down the shim for maximum contact.

I prefer the built in shims on the chinooks than the supplied shims with my masts as one trapped my finger once when putting it on

Never had a triple clamp slip, and had 3 before I had to renew when I became a team rider. Must confess I preferred the older triple clamp, due to the ease of putting the boom on without faffing with hinges in tight luff tubes with hand eating zips.

Agree with ejmack, use the rubber shim and grind the raised lip off one side and then it fits

Yep, agree with the rubber shim. I used a fiberspar one for years with a chinook boom. Never slipped.

I also had to grind the end off the shim to get it too fit.