I'm sure this comes up a fair bit.
What are the pros and cons of SDM and RDM masts? Why would you get either one over the other? Is there any noticeable difference for your average weekend windsurfer?
Context: I've heard that for lighter people an RDM mast is good because it makes the sail feel a bit lighter. My younger sister is learning to windsurf and we are looking at gear for her. She's using a 4.7 KA Kult at the moment rigged on a 400cm mast and an extension.

Cheers, Moose.

Personally I don't think it matters, What ever gets you out there. Not all RDMs are light but the high end ones are but costly. Wave sails I'd say RDM for ease of rigging and easy to grab in tacks and when you screw up. For your sister I would just get the lightest thing you can find, The easier you make this sport the more likely someone is going to stick with it. Light means high carbon content which means big $$$ and in some cases less durable, it's a toss up which you choose but light is very nice but can strip your wallet.

Generally-

SDM = more grunt from sail.

RDM = nicer to use, little bit flatter sail, increased durability, often mast itself is a little bit heavier, hurts more when it hits ya.

They say heavy people aren't so compatible with RDM, I weigh more than most guys & use them in both my wave and racesails but I do sacrifice a little bit of bottom end for a sail which is much nicer to use.

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mkseven said..

Generally-

SDM = more grunt from sail.

RDM = nicer to use, little bit flatter sail, increased durability, often mast itself is a little bit heavier, hurts more when it hits ya.

They say heavy people aren't so compatible with RDM, I weigh more than most guys & use them in both my wave and racesails but I do sacrifice a little bit of bottom end for a sail which is much nicer to use.

So true Mark. After numerous SDM breakages I somewhat reluctantly changed over to RDMs but haven't looked back. There is definitely a difference in initial power (acceleration) with the SDM compared to the RDMs softer traits (when a gust hits) but at top end speed I haven't noticed any difference (maybe that's just because I've reached the limits of my abilities ). In fact it's probably made sailing in the ocean just that little bit more comfortable (read controllable). RDMs improved sail rotation and I much prefer to use a shim as you need very little tension on the boom clamp whereas the SDM's needed just enough not to slip and not too much so as not to crush the mast which was a very fine line (I used a small sheet of 1mm rubber on my SDMs at the clamp so I didn't need to over tension)

There's some great previous posts regarding SDM v RDm too
www.seabreeze.com.au/forums/Windsurfing/General/Rdm-or-Sdm-for-Lightwind-setup/
www.seabreeze.com.au/forums/Windsurfing/General/Skinny-masts-4/

I have found the above to be the opposite case with wave sails I've used. but that could very well be due to a lack of cams.

in my wave sails, rdm gives more power. I don't have a technical explanation for this other than I think it's the extra luff round as my sails are designed to suit both sdm and rdm so running an rdm allows the front of the draft to have a bit more depth.

could be a specific mast thing also.

kind of, you can rig a wave sail with a bit less downhaul for grunt & it'll still twist off with the rdm & work ok but it's not ideal setting, but then being underpowered isnt ideal either. Bit harder to do with race sail as you risk breaking battens.

if u can get a SDM mast that suits the sail (compatible with sail mast curve) then get one as they are way cheaper, the big bonus I remember (decades ago now) also was that the sdm mast and sail tended to stay on the top of the water for uphauling and waterstarting ease, the first season I changed to rdm s I hated how the rig was always submerging and going straight down!!

For the average weekend surfer I think the biggest difference is you will most likely never break a RDM mast while sometimes a SDM mast will break for no apparent reason.

I am/was a heavy weight. I was up around 100+kgs, but am now down to about 90. I started out with SDMs and have broken a few, but mainly because they were 530 or 580 masts and under huge loads. I broke some 460s too.

I decided to ditch the SDMs in favor of RDMs because I was sick of breaking them, and with Ezzy RDMs I could buy the parts separately. The disadvantage to this is that these masts are always going to be a compromise for most sails. Durable, but not exactly the perfect curve for most brands of sails.

I feel that the larger sails with a 490 could be better with an SDM, as I think the RDM loses a bit of power. The smaller sails probably don't matter as much. I have been using Ezzy RDMs for maybe 5 years now and haven't had a problem with them. I even use KA cammed sails with them, and they work fine.

I like them, as I don't care about 100% performance and am more worried about breaking gear. I should be able to change sails and use the same masts without getting locked into specific brands. I can't afford to buy much gear, so being able to buy a sail without the matching mast is a plus.

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FormulaNova said..

I like them, as I don't care about 100% performance and am more worried about breaking gear.

+1 That's it in nutshell

I only use RDM, the oldest that I still use is an 8yo Ezzy which I now use on a Loft. Performance wise I don't know as I haven't used a SDM since that Ezzy, but then I still manage to keep up with my mates and have fun with no tears. The last long ocean swim with a broken SDM was it for me

I have a North SDM mast because that's what my 6.6 North Natural was designed to be used with. When I was looking for a new 5.5m I found it hard to find a sail that wasn't specified RDM only. I ended up getting a Naish Vibe which is stil RDM only but the SDM still fits in it with plenty of room to spare. I'd be happy to suggest an SDM but if your sister is going to be getting some new sails also, make sure whatever mast you get will work with them.