RDM versus SDM masts remains one of the hottest topics concerning windsurfing masts. Wasn’t everything just right when there were no RDM masts?
To get a honest answer to this question we need to know why RDM masts were introduced and what the benefits of such a mast is.
RDM masts were introduced as a stronger version of SDM wave masts. The wall size is bigger as the wall size of SDM masts, which means that they have a bigger wall thickness. This results in a smaller amount of broken masts in the surf.
Because of the smaller diameter your sail feels lighter in your hand as well. Although when rigging a RDM mast in a sail designed for a SDM mast the mast length is not equal to what is subscribed.
What Are The Disadvantages of RDM Versus SDM Masts
One of the biggest disadvantages of RDM versus SDM masts is that they are heavier than the same SDM mast would be. The funny thing is that your rig feels softer or as you might prefer to call it, it feels more maneuverable.
The inside diameter of your mastbase (the part where you need to shove you mast base or mast extension in) is smaller as well, so you need to have a new mast foot and/or mast extension.
Then you needed a new boom in the beginning, now all booms come with mast shims to fit them tightly onto the slimmer diameters. Do I need to tell you that a mast shim also is the best option preventing a mast to break?
When snapping a boom onto your mast you want to connect it tight, because one of the things you don’t want to happen is while surfing having your boom sliding down on your mast.
But a boom can be connected to tight to your mast, and when this happens, your mast can break easily, so the reduce this to a minimum your best bet is to use a mast shim.
One last thing to mention is that for the average windsurfer of 80 kilo’s or more, ask yourself if you should go for an RDM versus SDM mast.
an SDM mast can be a better option as you like to have a more powerful sail to get you up and planing.
So if you like a more powerful rig don’t just go for RDM masts, but give the right SDM mast a change to prove itself, you might like the feel of these masts more.
Wavesails Designed For RDM Masts
Now that these Reduced Diameter Masts (RDM) have proven to be a great option for wavesails, all the brands have them and even have sails that are specifically designed on RDM masts.
There are wavesails designed on SDM masts as well, most of them do just fine on RDM masts as well.
Since a few years even the sail manufacturers Neill Pryde and North Sails have decided to no longer refuse the benefits of these thinner masts and have sails specifically to be rigged on RDM masts.
Most wavesails designed for RDM masts are easier to handle especially when you’re a light windsurfer of let’s say 70 to 80 kilo. The lighter windsurfers like a soft sail handling even more.
With these thinner masts you sail feels more compact and softer. This can make it a disadvantage for heavier riders as mentioned above.
What To Look For When Buying A RDM Mast
When deciding on buying a RDM versus an SDM mast there can be several points you need to have deciced on up front.
Do you want a softer feel to your sail, or just want to switch to RDM? Maybe you like the light weight of an SDM mast or have sails bigger and 6 meter than SDM mast still make sense.
SDM masts still are the way to go for all racing sails having camber inducers, we leave Loft Sails out as they’re standing on their own but let you decide by using spacers if you like an RDM or SDM mast in their Blade racing sails.
Although RDM seems to be the direction in windsurfing mast design you and your sails may not benefit that much from RDM versus SDM masts.
So, what do you look for if you decided to go for a RDM mast? First of all you need to take a close look at the sails you want to use it for.
Are your sails designed for these new masts? If not your sail might not be perfectly fit for these sails. Are these rumors true and how different does these masts make your sails behave
To know for sure I tested my 4,7 and 5,3 North Sails Ice wavesails on a RDM and SDM mast as well. Although they were designed and tested on SDM masts, I liked them more when rigged on a RDM mast.
Both masts were constant curve masts and had the right bending characteristic, me as a 75 kilo windsurfer liked the softer feel to these sails when rigged on the thinner mast, the feel of the sails now felt more like the Voodoo which is a really soft sail for North standards.
The most impressive thing I found out was that when overpowered I could much better control my sail when a gust hit my sail.
Assume you have a sail that’s not perfect for a RDM mast but you like to have a softer feel to it. Just try it on one of these masts. You should know what the subscribed bending curve is, as this is crucial for the functioning of your sail.
You need to know that the subscribed IMCS number is matched as well. You could however get one er two numbers on the IMCS scale up or down if you like your sail to be more powerful or softer.
When you like to have a RDM mast but still want your sail to be softer, take the shorter mast length and use a longer mast extension, you will notice a remarkable difference, even if you’re no pro rider or just windsurfing a few times a month or year.
RDM Versus SDM Masts for Racing Sails
As racing sails are designed for the maximum amount of power as this is when they perform best, you should think that they are designed specifically for SDM masts and most sails are.
But there are race sails that go on SDM masts as well. These sails however are mostly the smaller sizes as in this high wind range control an important part of your speeds.
Without control no higher speeds they say, and that’s true. Would you go downwind, I mean really far downwind like a speed sailing angle downwind without control?
To have better control over your sail in highwind a RDM mast in your sail can make your sail softer as well, you need to know however if the cambers designed for a SDM mast will fit the reduced mast diameter as well.
If you are a light racer or just like the feel of a RDM mast in your sail, or just want to use your RDM mast from your wavesails in your race sails as well, than there are not that much options.
The Loft Sails Racing Blade, however is a full on racing line that can be sailed on RDM masts from the smallest to the biggest sail.
So RDM versus SDM masts can even be an issue when looking for race sails, racing sails are equiped with camber inducers.
Cambers are designed around the diameter of the prefered masts.
When they are designed around RDM or SDM masts, they won’t fit if you use another diameter mast.