All about masts...new technology?

[brega]

I've searched the forum and can't seem to find clear info. I am relativly new to the new mast technology on the market today. So can someone explain to me the diference between an SDM & RDM mast. I know I use an RDM 460cm 2 piece mast, but what advantages do these RDM masts have? And what is a fiberspar mast? if there's any other new mast technology please let me know. I hope this will serve as an informative up to date thread for everyone.



-La Parguera Crew

[coachg]

Fiberspar is the name of a company that makes masts, so a Fiberspar mast is a mast made by Fiberspar.

There are basically two types of masts. RDM (Reduced Diameter Mast), or Skinny, and SDM (Standard Diameter Mast).

The advantages of RDM’s with their smaller diameter are that they are easier to handle because you can reach your hand around them easier do to their smaller diameter. RDM’s are also easier to rig do to the smaller diameter. RDM's are stronger, thus breakage is less of a problem than with SDM.

Beyond the advantages, it becomes a matter of preference & cost as to which mast you choose. SDM’s offer performance advantages over RDM’s, especially in the larger sizes. But when all is said and done, it is best to buy the proper mast for your sail or buy the proper sail that fits your mast.

Coachg

[swchandler]

As an addendum to Coachg's comments above, RDMs are stronger overall due to the fact that the wall thickness is significantly greater than SDMs.

Also, another thing to be aware of is that different mast brands can have slightly different bend curves, and this is irrespective of whether a mast is a RDM or SDM. As a result, it's important to ensure that a given sail and mast are compatible. Otherwise, the sail will not perform as intended by the sail designer, or in worst case scenario, the match up will not work at all.

Lastly, masts are manufactured with varying percentages of carbon content. The more carbon used in the manufacture of the mast makes the mast both lighter and more responsive (the frequency response is much quicker, so that the rigged mast and sail returns its intended shape faster when deflected by the wind). The downside to a 100% carbon mast is that they are significantly more expensive, and in the case of SDMs, they can be far more fragile and subject to breakage.

[U2U2U2]

Plus side for RDMs:
stronger, will improve the performance in almost any sail, exceptions those over 6.5 . almost all the new sails are designed for skinnys, some claim either are suitable. easier to rig/de-rig. Most cases are lighter.

plus for SDM

when at the top end of the sails range or overpowered, they seem to perform better.

Minus for RDM, they sink faster, small hands may have a grip problem
they hurt more when hit with in the head ( good case for a helmet)

if you already don't have then you need a RDM mast extension, as well as for most booms a small sleeve to make your boom fit tightly.

the suitability of the correct mast for the sail is very important, wrong one and it will be crap.

Boards UK magazine as a reference, have done mast tests the past few years.

[jingebritsen]

Tabou, did you mean to say RDM's improve performances of sails larger or smaller? RDM's don't reflex as quickly back to their original shape, thus the sails stay distorted longer when bent by the dynamic forces of sailing actions. Also, when down hauled bunches they tend to really flatten the sail too much. I've tended to hate larger sails with RDM's. Too noodly and unstable.

If you sail in venues that have large wind ranges, SDM's are better. If a typical day is 14-28 vs some other part of the world that has something more like 20-22. Unfortunately, the industry looks at gear thru the paradise filter on this issue.

What I would like is a std diameter performing RDM that floats like a SDM, and never breaks. I've broken 30 SDM's and 3 RDM's in my 26 years of windsurfing. RDM's still break in the surf, just not as much. They tend to suck in choppy gusty days too.

[U2U2U2]

[artnvicky]

There is a 3rd category of mast - the RDM tip, which combines the best of both types.
Cons for pure RDMs as I see them are:

RDMs are o.k for really little sails, but leave too much un-stabilized room in the luff, so are not so good in gusty conditions. The sail feels too nervous. Sailmakers understandibly have resisted building separate RDM-only as well as SDM sails. This would cure that problem. It seems odd to me that many sailmakers have such huge product lines with only minor differences between models, yet all will fly on both mast types. Hmmm.

With a smaller diameter, a mast slam with an RDM mast can do more damage to your board.

The lack of taper with an RDM requires tighter clamping at the head so that the boom doesn't slip down the mast in choppy conditions.

The RDM's lack of volume for float can make them more prone to turn turtle. This makes for endless fun waterstarting! Many also feature a reversed ferrule, which makes sealing off the head from water more challenging. Completely plugging any mast invites sucking in water.

Yeah, they're more durable, but in my view, not as much fun to sail. And this is all about play anyway!
Want durable? Get a cheap carbon 30 or a wave mast.
-A

[swchandler]

I switched to RDMs more recently over the last 3 years, yet I haven't experienced the notable downsides that some are identifying here. I'm currently using 400, 430 and 490cm length RDMs across my quiver (4.2-8.3). While I use the 490cm strictly with an 8.3, I still find pretty great performance attributes overall. However, I'm a lighter weight sailor, so I thinking that might have a lot to do with it. Also, I prefer a fairly flat rigged sail that doesn't rely on a deep draft for raw power. If someone likes a deep draft and a lot of negative outhaul, I'm convinced that that sailor would more likely prefer an SDM for stability.

[jingebritsen]

What complicates this issue most is how often does one sail, and how lit up do those sessions become? Quite often, I'm sailing a meter or more sail than those around me, sheeted home and blasting around, pumping out turns when necessary. Sometimes, the wind abates a bit, and I adjust and pump more, rather than rerig. Lots of folks do not sail as much and, when they do get out, they change rigs too quickly as conditions vary here in FL.

In venues where conditions don't vary so much, perspectives are way different than mine. Doesn't make 'em wrong, just different than what may be appropo to anyone else's? Down hauled flat, sails become less stable. RDM's allow for a flatter sail with less D/H, thus they get twitchy sooner.... Too much like work for me. Guess that's why cam sails just won't disappear despite all the consumer oriented mantras about camless being better, right?

[bred2shred]

The primary reason why RDM masts were developed was to take advantage of the increased wall thickness which results in a more durable mast. RDMs can reportedly bend a foot farther than an SDM mast before breaking. To my knowledge, RDMs have never claimed to offer better performance from a weight, response, handling, or ease of use standpoint. The reason for using an RDM is for increased durability primarily when wave sailing- no a 30% carbon SDM is not as durable as an RDM.

Many people find that they also like the fact that RDMs slide into the luff sleeve more easily than SDMs when rigging, and that grabbing the RDM (during a gybe for instance) is easier than an SDM.

There are many claims that RDMs don't float as well. Again, RDMs are primarily intend for advanced sailors that don't have a problem waterstarting and generally do so quickly enough that a sinking rig isn't an issue.

Also, some folks claim that RDMs are too noodly. I'm 210lb and I find RDMs to be perfectly fine. But if you're going to be doing slalom type sailing, then you probably want an SDM. Again, it's a compromise and you have to consider what the primary purpose is for an RDM- durability.

As for RDMs causing more damage to the board or causing more injury if they hit your head, I think that's totally bogus. Any mast is going to cause damage if you hit it hard enough. The RDM would have a better chance of surviving a hard hit.

sm