Translator from GOOGLE


I do NOT profess to be a windsurf equipment expert. I just wish to share my experiences and experiments with others :-)

When I started with the BIC Dufour there were long one-piece masts that stayed where they were ie hard to transport. I managed to break one by vaulting over it while hooked into the harness. Mast bases did not have the three (3) pulley systems and were hand hauled. This meant they did NOT bend much.

Two (2) piece epoxy (and later carbon) masts could at least be transported in the car when mobile. Early one-piece mast equipment probably was transported to the lake and stayed there. ( I actually read somewhere that North Sails was now offering three (3) piece masts !! )

I went from fibreglass/epoxy masts to a 490 cm SRS/SDM 90 % constant curve carbon mast with an IMCS of 29. It is from an obscure company called Autima out of Taiwan. Lesson number one: buy from the sail manufacturer or at the very least, use a mast approved by your sail maker or someone you trust. My mast works fine, but they do not answer e-mails nor phone calls. I just wanted more information on the specs $%^&*(

So, we went from one and 2 piece masts to carbon masts with many different lengths, now widths (SRS/SDM and RDM), carbon content and bend characteristics. Some people say windsurfing is too technical :-) The easy way out is: purchase the recommended mast from the sail maker :-)

Length: Masts seem to vary from about 370 cm to 550 cm in increments of 30 cm. Obviously length is all about fitting into the sail without too much sticking out the top or bottom.

Width: SRS/SDM or standard radius/diameter was the norme until recently with RDM, reduced diameter. They say reduced diameter is stronger and less likely to break, especially when doing wave sailing. Wave sailors also seem to use lower carbon content. Once again this is to reduce breakage. RDM masts are actually thicker and heavier. Some swear by them and others do not. Some say heavyweights should stick to SDM and...
In other words , there is NO rule or recommendation written in concrete. Sometimes it is what you like !!!

Carbon content: Seems to go from 30 % to 100%. Read somewhere that 100 % is actually a myth. Lower values seem to break less and do not whip back as quickly  - from what i have read. Higher carbon content is supposed to be lighter as well. Bigger sails and race sails seem to prefer higher content- and bigger riders too. Guy Cribb says put out as much money as you can on carbon content. Better recovery and efficiency.

Bend: Little bit of controversy here :-) IMCS or Indexed Mast Check System would logically be the standard, but it is not. Masts of the same length and carbon content may have the same IMCS, but behave completely different in the same sail. Here people speak about flex top (Niel Pryde), constant curve (Sailworks) and hard top (Maui Sails n Gaastra). This is why it is important to put the "correct" mast in your sail. Once again, if you buy the recommended mast from the sail maker, IT SHOULD BE  NO ISSUE...

Peterman has written a much-quoted page on the subject of IMCS and mast bend: Peterman IMCS comments and Perterman Mast Article. There was also an article in French Planchemag in 2010 I believe. I thought I had a copy, butt all it informed me was : donut put a NP mast in an MS sail and vice versa :-( Thought there would be more specifications. Then again perhaps I did not have the right edition.

Can also check here : mast tool selector - unifiber

0 -  6:        Hard top.
7 -  9:        Hard top - constant curve.
10 - 12:     Constant curve.
13 - 15:     Constant curve - flex top.
16 - 18:     Flex top.
19 - 21:     Flex top - super flex top
22 -     :     Super flex top.

here is the chart from unifiber:
WARNING: this chart is ONLY viable for one year. Example in 2014 MauiSails went from extreme hard top to constant curve !! and many others moved around as well. Thanks to UNIFIBER for updating their mast selector charts !!!! Guess we all pray for the day when your mast will adequately fit ANY sail - size permitting of course ie independent of the different curves --> GO TO ONE !!!

clique to enlarge
Further down is another chart found on the Australian seabreeze forum and seems to come from Holland:

George, who surfs at OKA all the time, seemed concerned about the Fiberspar masts' placement on the chart. Windsurfing-direct is selling these masts with Gaastra and some people think they go with MauiSails. These sails are known as "hard top" and do work well with OLDER Fiberspar masts... One representative from a sail company says:

Except for some older masts that are still available in the marketplace, the current Fiberspar mast range is not well understood at this time for a couple of reasons. Most important of these is availability of the Fiberspar brand masts in the marketplace. We would know more about the masts were there a company behind the brand communicating with us and allowing us to test our sails on the current range of masts. Because there is no energy behind the brand, we see the Fiberspar mast slowly diminishing in importance for windsurfing consumers.  

George has confirmed that the Fiberspar masts are getting more difficult to acquire !! 
When I finally got an answer from "Fiberspar", I was referred to Excelcomposites, a firm that purchased  Fiberspar some time ago ...

Clique to enlarge

Constant Curve a.k.a. stiff top
Any mast with a base - tip percent of mid-point difference in the 10% - 14% range is considered to be a 'constant curve' mast. The 'classic' definition of a constant curve mast is a mast having a 76% tip deflection percentage and a 64% base deflection percentage. These masts are often labeled as 12% constant curve masts. (as in the example above)

Flex Top
Any mast with a base - tip percent of mid-point difference in the 18% - 22% range is considered to be a 'flex top' mast. The 'classic' definition of a flex top mast is a mast having a 82% tip deflection percentage and a 62% base deflection percentage. These masts are often labeled as 20% flex-top masts.

Combi Curve
Any mast with a base - tip percent of mid-point difference in the 14% - 18% range is considered to be a 'combi curve' mast. The 'classic' definition of a combi curve mast is a mast having a 79% tip deflection percentage and a 63% base deflection percentage. These masts are often labeled as 16% combi curve masts

The above numbers were taken from Peterman and the discussion from somewhere else {i believe}

personally separate hard top from constant curve => some call them stiff top
super hard top - Maui Sails
hard top -  Gaastra, older NP masts from the Barry Spanier era, Severne, Naish RDM
constant curve - the majority - Sailworks, Aerotech, Naish,
flex top - newer Niel Pryde, North, Ezzy ?, Hot Sails Maui ?

NOTE:  I just added the word newer to Niel Pryde in the flex top section. The reason or this is the following: on the MauiSails forum, there was some discussion about the NP CK66 mast and MS sails. This mast is from the Barry era with NP ie over 10 years ago and DOES work with the MS sails. Life is full of surprises :-)

The following is from the NorthSails website:
Thanks to our new mast measuring and our refined IMCS system, we were able to analyze the masts of all other brands. This allows us to say exactly how good NorthSails masts work with other brand sails or which masts from other manufacturers are compatible with NorthSails:

• NorthSails compatible masts / sails: Aerotech / Ezzy / Goya / Hot Sails / KA Sails Loft Sails / SailWorks / Simmer / XO Sails
• NorthSails partly compatible masts / sails (at about 30-40% performance loss): Gun Sails / Point 7
• NorthSails incompatible masts / sails: 

Hard Top: Gaastra / Maui Sails / Naish Sails / Severne 
Flextop: Insert Tushingham / Neil Pryde

The importance of the mast is almost always extremely underestimated. In fact the mast is the engine of each rig. Or in other words, a Ferrari chassis with a beetle engine will never become really fast!

what about masts like Powerex, Fiberspar and NoLimitz ?? (and dynafiber, UP, etc) Will do a follow-up on this, but so far my understanding is - these are all constant curve.  So far it seems the Fiberspars could be used with the earlier MS TR sails, but NO more. This means they are CC tending towards hard top. So far it seems Powerex are softer top and harder bottom than MauiSails masts - which are at the extreme left. This makes it seem like Powerex are closer to NP/Niel Pryde.   The reason I crossed OUT the previous phrase? An RDM Powerex seems to work fine with my Hot Sails Maui and NOT with someone i saw rigging a NP. The mast sleeve had ripped and the sail was NOT even one year old. He was blaming the sail, butt when i watched him rig, I asked about Powerex and NP compatibility. I did NOT like the look of the combo for rigging "/$%?&* FAR too much pressure at the top !!! and YET everyone tells me Powerex is like a flex top !!!

The mast bend curve for NL is posted on their site: its about 65 77% or 12 This puts them in the SW/Sailworks arena - for me. The NOlimitZ weblink disappeared - as usual - will start to copy and paste this type of data :-( Also , people mix NL tops and bottoms to suit different sails - as discussed on iwindsurf ...

The weird thing is David Ezzy used to say any mast works with Ezzy sails - it's just a matter of performance. I do not understand - This is a very respected fellow. Some riggings look like crap and should not work at all :-(

Sailworks publishes their specs on their masts: Barry Spanier of MauiSails says it is too difficult to put such precise numbers on mast specs. People are accusing Barry and MS of denying that their masts and sails are more hard top than ANY other windsurf sail.

do not take my word for it - investigate before mixing n matching. MauiSails says ok to their masts, Gaastra and Naish. For me right now masts, sails and boards are pricing themselves out of my range. i am having a hard time outbidding people for masts on e-bay !! Guess I will stick with what i got and try to fit the next sail 7.5 on my current 490 - SW Retro and 2010 Gaastra Matrix are ok.

Here is an extract from about masts: (anders is a swedish speed windsurfer)

For most sailors the recommended masts will do the work. Especially if you are into slalom and not are committed to find the extra knot on the top. 
The general rule is light riders - soft masts, and heavy – stiffer. But remember it could be the opposite. When it comes to tuning the sail, it is good the have some ideas and basic knowledge in sail design. You also have to know what you are looking for. Low-end acceleration, middle-end acceleration, top-speed, control etc. I.e. the right mast can give you the turbo-kick you want when the gust comes!

Mast bases after the epoxy/fibreglass era have at least a standard nut to fit into a standard mast slot. They also have a pulley system in order to properly downhaul the sail - to sail maker specification. People use one-handed or two-handed downhaul tools, harnesses and winches for downhauling the sails. VERY IMPORTANT: DO NOT use a screwdriver of any sort !!! Many people have injured themselves and/or punched holes in their sails !!! Downhaul tension varies GREATLY between sail makers. North Sails makes a mast base with downhaul cinch.

Also, there are two (2) different pin mechanisms that must match the mast extension. There is the standard U.S. two(2) side pins and the Euro single pin in the middle. Some say we are going towards the Euro pin - it is just easier to put and take apart. I still use the U.S. two (2) pin system and have never had an issue except getting it apart when my hands are frozen. Some people have had the Euro pin come apart while sailing = woah.

When I started this blog, there was NO intention of making it a "complete" type of website. It was supposed to be a windsuring journal and nothing more. Guess I just got carried away.. In any case, if there is all this info, then I feel I must also list how to properly thread a pulley. I actually had to show my buddy who windsurfed shortboards longer than I :-( It makes it easier to downhaul and is just more efficient. So, here is my version of the threading:

How to thread “Streamline” Pulley

Start with thread down => for my old “homegrown” extension this means pulley on the right

  • Thread up to sail pulley closest to mast – up the bottom and out the top
  • Obviously thread up on that pulley
  • Thread down middle extension pulley – at the mast side - from inside out
  • Thread up outside that extension pulley – obviously
  • Thread to outside sail pulley @ the top side - top down
  • From top of sail pulley to outside of bottom extension pulley. - outside in
  • Now up to middle sail pulley from bottom up
  • And lastly up through the cleat .
  • There may be some slight crossover on this extension since the start of the cord should actually be up higher….

  • For the mast extension where those pulleys line up with the sail pulleys, it is even easier to rig properly. Just keep putting the thread through the logical pulley on the logical side and make sure no lines cross or touch.  At the left I have shown a simulation of where the pulleys at the base line up directly with the pulleys of the sail. When one does this with either of these setups, it makes the downhaul easier. Just the same I use a one-handed downhaul tool.

    An Italian has a new invention called the iDo to help people with masts and sails.  It is a mast base that keeps the sail out of the water. It cannot handle big sails and one better attach the board to something cuz it could take off on its own :-)

    The mast extension is not the same as original or older mast extensions  and has better clamps to hold the mast up. Some surprisingly enough do NOT put markings on the holes !! Some have closer holes , like every 2 cm, to allow more flexibility. One fellow told me he will always stick to NP extensions because the cuff for the mast is just a little smaller and slides in and out of the sail so much easier. Each person seems to have their favourite based on experience or misfortune.

    The ferrule is the part of the mast that goes from one part into the other tightly. This was a new word for me, butt apparently is a common part of the English language meaning ring or bushing :-)

    Masts are expensive and critical. Choose wisely and handle with care.Word to the wise: keep sand out of the mast joint. Some people put electrical tape on the joint. Masts that are stuck together are NOT easy to take apart :-( I too started using electrical tape to join my mast pieces together when rigging. In my case it not helps keep the sand out, butt makes it MUCH easier to get the mast out of my cambered sails like my MS-2...

    One thing I forgot to mention: it is important to measure your equipment. My 490 mast is actually 491 cm. This may not seem like much, but it is an indicator in terms of downhaul. One cm more or less of downhaul is definitely  a difference one will feel out on the water... For downhaul I tend to stick close to manufacture specs, but for outhaul, I may go way under or way over - to see what I can get out of a sail :-)

    Masts are expensive and MUST match your sail(s). They can get stuck together, crack and break - especially @ the ferrule IF you do not ensure the two(2) parts are completely together. My carbon masts cost me over $400. A 100% carbon mast can be close to $1000. There are used masts, but one needs to be careful and inspect the mast.  The mast is the backbone and we all know how important that is and how much it can hurt !

    As you can see here - they may break at the most inopportune moments $%^&*(

    Crash Bjorn Sylt from eric bellande on Vimeo.

    Addendum 2015 -- Mix n Match ??
    End of 2014 I decided that i needed a replacement sail in the 8.0 range for going in the snow with my heavyweight carcass. I managed to find a used SailWorks Retro 8-oh at 2-rad for around $200. Bruce Peterson had once informed me that the Retro sail would be okay with my MauiSails 490/75 hard top mast. It is okay, but quite loose leech. Even when i put less than the recommended downhaul. Some discussion on iwindsurf at the time felt that a hard-top/HT mast on a constant curve/CC sail like the Retro would yield a tighter leech. Quite the opposite happened. Here is a photo with less downhaul...

    Since this seemed to generate some discussion, I thought what happens when one rigs a flex top/FT mast on a CC sail like the SW Retro ?? I happened to have a Neil Pryde/NP FT 490/90 mast that i had purchased summer 2014 to go with the HotSailsMaui SpeedFreak 8.5 dacron sail. As anticipated the battens pushed against the edge of their respective sleeves. Downhaul did NOT generate as much leech and the battens were okay once outhauled - and not as much force as required when outhauling with HT. Here is the photo with the same downhaul and outhaul as in the photo above. I tried this sail and found it fine !! Leech is loose, but up high ONLY !!

    As "luck" would have it, I broke the NP 490/90 SDM mast on my first trip to Hatteras in May 2015. Should I cry or ?? NON, will not let such a misfortune ruin my first holiday to the windsurf mecca of Montreal. None of the local shops had ANY used 490 masts and all seemed to carry Chinook masts in that size - either 40% or 80% where 80% was much more money - obviously. So, purchased the 40% to carry me through the holidays - and perhaps beyond. The SailWorks Retro is constant curve and I expected it to look better with the Chinook mast. The sail looked and sailed the same as with the NP !! It felt heavier since the mast is about 7 pounds. Tried the HotSailsMaui with the mast as well and it looked and felt fine as well - again somewhat heavier - especially in the tack. Surprise, surprise !!

    Speaking about mast bend... just how far can a mast be bent before it breaks ??

    In 2015 I found this on the Unifiber website:

    This helps in analyzing the chart I had published earlier from NoLimitZ

    Earlier I had discussed that these masts seemed to be in the SailWorks constant curve arena. Based on the diagram they are in the constant curve / flex top area ...

    Around 2014 Maui Sails went from hard top masts to constant curve... They were saying the new sails fit the older masts and vice versa. Sailors were  disagreeing and wouldn't you know it, in 2015 the company broke down - Barry and Artur left and started S2Maui sail company with stuff available in 2016. Because I have MS masts 520 and 490 , I need to decide which direction to go in the future. I also have a HotSailsMaui SpeedFreak 8.5 sail that prefers flextop like Neil  Pryde. Ironically flex top sails like Tushingham are also going towards constant curve ... So, what does all this mean. Personally, I would suggest that if you have not started a sail quiver yet, go for constant curve... For now I will stay with what I have. An HSM SPF 10.0 m² sail also fits on a 490 and so, perhaps one day I will go flextop... For now, I stay with my mix of sails and masts ...
    SEE   >   have-mastssails-all-gone-cc.html

    Neil Pryde is also another story $%^& Barry Spanier was there once upon a time and masts were HARD TOP. We are know they are currently FLEX/SOFT TOP. However, it seems there actually was a time they were CC/constant curve #$%^&* This is how I discovered that !! Unfortunately destroyed the top of my NP 490/99 mast en route -  my first trip to Cape Hatteras, NC. As we were there and I wanted to use the sail, I purchased a Chinook 490/40 CC mast, which I hope to sell today. Kept my eye open looking for a NP 490 of 60% or more carbon and found a NP FreeRide PRO 490/77 from GolfSport, Mississippi. This mast is from around 2000. The top fit in the base from the original NP 490/99 and this is what the sail looks like - NOT tried on the water YET.

    Some forum discussion  suggests the bottom may go soft - not the case if I keep using the original bottom. Will  report back after testing ON the water ...

    For now .. does NOT look that different from original settings ...

    And first outing was VERY good. It was rated 8 outta 10 and ONLY lost points due to weather/wind conditions and NOT due to sail/mast combo. The sail/mast combo was GREAT !!

    In 2016 I am reviving an old dilemma , RDM vs SDM. SDM is standard diameter and RDM is reduced diameter mast - as discussed earlier. Buddy windsurfer King Kong has been busting expensive SDM masts and is sick and tired of it - going RDM. I have seen him go out on a SailWorks Retro 8 m² sail with a NorthSails RDM 490 mast. Some people recommend heavy weights like us to continue with SDM on sails larger than 7 square meters. Others suggest to stick with SDM on cambered sails. Ezzy is more RDM oriented and has a Lion 2 camber sail going as large as 9.5 m². It is thus more free race and not quite race sail with four cambers... RDM is NOT lighter, but feels softer ... For myself, my RDM mast is used with sails 6.9 and down. Then again I only go down to 6.3 ...

    Well, I am VERY happy to say that Bruce Peterson of SailWorks agrees with me ...

    You have already answered your own question, but I will reaffirm it.  The reduced diameter design and construction lends itself to making very strong, shorter and softer masts.  I think that the RDM is a superior mast in all applications up to the 430 cm length.  Beyond that, beginning with a 460 and most definitely with a 490, the reduced diameter starts to work against the required stiffness for that length.  A Nolimitz Sumo 91% carbon RDM 460 is a great wave mast, but does not feel as light or lively as a Joystick 75% carbon SDM 460.  The Nolimitz FAST 460 (listed with our Twill masts) is probably the best 460 RDM I've seen, but it has to be 2 points stiffer on the MCS to reactively compare to Joystick 460 SDM.

    Like other 490 RDMs (North, Ezzy, Gulftech, etc.) the Nolimitz FAST 490 RDM is not a very stiff 490 when compared to a 75% carbon SDM, but it sure is a brittle RDM mast. When you try to stiffen up the small diameter too much they just buckle under load as all the wall thickness resiliency is gone.  We've stopped recommending the FAST 490 mast after a few failures.  It has the highest failure rate, by volume, of all the Nolimitz RDM masts.

    Your Retro 8.0 needs a 490 mast (especially at your size) and I think your best bet is to stick with 75% carbon SDMs, like the Joystick 490.

    Fair winds,

    Bruce Peterson

    I apologize if this post is NOT organized in a more logical or easy reading manner - I add thoughts hap hazard / adhoc of what I feel may be of significance or interest to  others ...

    another place to see current mast curves of sail suppliers/makers AND their changes over time ...

    now there are very FEW masts that are still HARD top -- avanti, point7sdm?, vandal rdm
    flex top getting less too ...
    now is mid 2020 ...

    In early 2024 unifiber is listing masts as CC/constant curve + FL and FH where FL is "Flex Low" and FH is (you guessed it) "Flex High". There are NO MORE hard-top !! When I look at the diagrams of the flex, it feels like the curves are not really that different, butt ... lol


    1. Hi, I appreciate your passion for the sport. Thanks for all the hard work

      1. Comments like that are always appreciated !!!
        11,000 hits per month and few comments :-(
        Thank YOU !!

    2. Great clarification on the bendcurve issue ...after reading a few of these i persuaded myself to buy some masts for my RS Racings and I've still feel that i've been conned by these brands cause there's still the weight issue and what it causes to the bendcurve of the mast . Mine weight in at more than 2.100 kg for a 460 Matrix100 and 1.850kg for the 430Matrix100 that's 12-18% more than they claim , even if the bendcurve 'may probebly' be okey i can not overlook the fact that there are a lot of sharks in our waters these day's :) . Still i want to thank you for the great mastbendcurve clarification !!!

    3. Nice work Joe,


    4. Joe,
      I'm an avid reader of your blog posts (and casual forum threads).
      I want to thank you for the effort of writing all this info online and keep updating it.
      I really appreciate such task!
      This post, and the new one about new freemove boards are my most visited ones.
      Please keep doing this!
      "Abrazos" (hugs) from Argentina


      1. Thanks Gaspar !!

        Comments like that keep me going...
        MASTS is my 2nd most popular post !!
        Ironically the BIC Dufour Wing which was my FIRST post on this blog is STILL the MOST popular !!!

        Enjoy :-)

    5. can't say more than what's stated above !!
      thanks for these (and other) clarifications, Joe

      biggest belgian fan ;-)

      1. Herzlichen Dank Mattias
        Merci Beaucoup
        Mant Thanks

        now get out there n rock :-)

    6. Just wanted to let you know that this is still useful information!

      I had a Maui MS-2 8.5 which wasn't rigging well on a Fiberspar 490cm mast, and now I know why.

      The results were similar to your Retro 8.0 with Maui mast. The leech was far too loose and made the sail feel smaller than its actual size and shifted the center of effort quite a bit too.

      1. GLAD to be of help.
        This is the 2nd most popular post on this blog.
        And so, we are NOT alone in our mast "issues"
        What i find even more troublesome is it also depends on the year of the mast :-) example: MauiSails just switched to CC/constant curve after MANY years of being the HARDEST top mast on the market !!!

    7. Just wanted to know that your downhaul pulley explanation is the best. Cheers mate!

      1. Glad you liked it cuz when i posted it on a windsurf forum they laffed :-) Now get back on the water :-)

    8. Andreas from Sweden10 August 2015 at 04:10

      Great overview. I'm looking for a new mast and your experiences gave me the insight I needed to proceed - Thanks! Great that you went into the downhaul as well. Always nice to learn more. Getting the details right just makes life better. ;-)

    9. Very helpful, thank you. I have been trying to find a used rdm mast for a NP Combat 5.3 sail. The NP masts are pricey and it has been tricky trying to figure out whether another mast such as Fibrespar would work, as I think it is also supposed to be a flex top. As I am only an intermediate sailor, I don't know whether I would even notice, but it certainly is much nicely when the sail is balanced.

      1. I have had luck with Powerex on a flex top sail - HotSailsMaui Fire.
        There are also Autima masts that are usually a little cheaper.
        In MTL they are available @ auventfou.
        MANY used masts on the windsurf forums/websites
        Here is a NP wave 400 for $100
        You may need to drive to get the bargain ...
        good luck

    10. Thanks Joe for the information. Mauro from Argentina


    all comments are now moderated = sorry.
    due to comment spam
    MUST have google account ...