PDA

View Full Version : In praise of SDM masts


nakaniko
3rd June 2011, 05:39 PM
Nowaday all is focused on RDM mast, brands pushing them and sometime making rdm-only sails. Luckily my wonderful HSM sails can be rigged on both, SDM and RDM.
I've all (almost) Fiberspar masts and I've also bought two (400 and 430) RDM for wave situations, but i've kept also the SDM, as selling them I would have gain few money compared to their real value.
As Fiberspar declare and write on their mast al the specs (weight, carbon content, reflex), it's easy to see that:
- a SDM mast of same carbon conteht is LIGHTER than the same RDM
- a SDM mast of same carbon content has way HIGHER reflex index of the RDM with the same carbon content.
So, yes an RDM mast is or should be more durable and waveproof than a SDM, but to get the same reflex of the old sdm brother you have to choose a way higher carbon content, and the more the carbon content the more it's fragile...
More: a SDM mast can be easily carried with the top inside the base, so less room inside the mastbag, you cannot do this with RDM. I'm able to carry 4 sdm masts in 2 hard-case FS mast bags, and only two rdm more in their dedicated soft case (all then inside the big tube mastbag)...
More and more: for us (middle?-)heaviweight riders a 490 is often necessary, sometime also more (520) as we need bigger sails to plane in low thermal winds, but even a 460 RDM is hard to find, not to telly a longer one...
Finally I've seem that in my windsurfing is way easier to find flat or choppy water conditions, where I use only the SDM's as I get a more lively feeling. Using RDM surely I feel greater handling and a softer response, but when I want to push hard on lake or sea and there aren't waves or shorebreak, no question, SDM is the best choice!

Unregistered
3rd June 2011, 09:24 PM
I`ve no doubt SDM are tougher and perfectly OK on some sails (ie the ones designed for them) but I`ve given up on them !!!

Found both my NP and Tush (Search and Rocks 4.2 to 6`s) when rigged on SDM can hang on for another 5 mph wind or so.Initially and when moderately powered sails felt fine on RDM but when really pushing to max they definitely break up earlier than when rigged on equivalent SDM. They need longer booms on RDM and downhaul tension is less .

And I dont care what anybody says (or that IMCS says differently) RDM are NOT as stiff on equivalent lengths as SDM.

I can rig my 7.5 (GTX) on a Tush 75 430 with a massive extension and it feels ok. (not ideal) but try same with a RDM and its feels more like its rigged on a fishing rod. And my 430 RDM is 100% C !!!

Lay a 430 RDM and SDM out together over 2 stools. The RDM is definitely more flexible ! (Perhaps the Tush 75 are over stiff ???)

My RDM `s are now the spares and only use them reluctantly !!! (But I weigh 105k)

davide
3rd June 2011, 10:20 PM
I only sail RDMs from 340 to 460 and I will not go back to SDM any time soon. Hot Sails Maui uses RDMs on their whole line and I am very happy with the bulletproof performance of the HOT RODS, from my Superfreak UL all the way to my race sails GPS. I actually love the fact that I can use the same mast on a Wave sail and on a Race Sail.

In general I think the consensus is that RDM are way stronger than SDM, and it is really a no brainer which one to choose in the waves or B&J. For the same carbon content they are indeed somewhat heavier, but keep in mind that a 90-100% carbon SDM is a big durability question mark, while a 90-100% RDM will probably outlast you. You should really compare a 75% SDM with a 90-100% RDM for durability (again not in the waves/B&J), and then the weight is the same. They are, in addition, easier to handle out and in the water (and easier to carry around, no need of a hard case, can be stored flat on top of each other, only one type of extension ... I saved a quite a lot of space in my van when I switched).

In terms of performance you need to rig a sail (more or less) on the mast it has been designed for, and if a mast feel too soft with a lot of extension for a 105Kg it just means ... it is the wrong mast for the application. Or if you use a race sail designed around a SDM you would be badly served by a RDM, and if you are a heavyweight a SDM + racesail is probably still the way to go, if you race. Same for big slalom sails (>8.5) or formula. For availability: Hot Sails has 92 and 97% carbon RDM in the lineup from 310 to 490 (65% carbon 340 to 430), and Loft Sails has a 520 in production.

I personally wish RDMs were the industry standard: this sport can use some simplification!

Unregistered
3rd June 2011, 11:50 PM
Rocks are designed to be used on RDM but I`ve found I need to change down earlier when rigged on RDM as opposed to SDM.Similar story with Search but suspect that been an older design was intended for SDM.Rock rigs on either. (In theory)

End of day we use what suits us. I sail waves/bump/jump all time and have yet to break a Tush 75 SDM. Last season all my Vmax`s were recorded on SDM and IMO sails have a larger wind range when rigged on them. Do suspect weight has a great deal; to do with it. At 105k I must be putting at least 30% more loading onto kit than Davide (at 70k). I can see great lines appearing in Rocks(and Search) when on RDM and overpowered.

I would never even consider a 460 RDM. Might even sell my 430 and 400 RDM`s from experiences I`ve had !! Cant see point in having a tougher mast if it results in a less efficient sail.. Before anyone buys RDM I would recommend you do a bit of testing with your rigs (at least rigging on them) before you commit and buy them.Especially if you are heavy.

The whole IMCS is thrown into disrepute. Compare even a 45% SDM with a 100% RDM and I`ll bet the SDM is stiffer !! (And probably as light !!!???)

Slightly off topic but has anyone felt the weight of Naish RDM`s !!! They are unbelievably heavy !!! Perhaps they are as stiff as claimed but should be at price they are ???

davide
4th June 2011, 01:04 AM
I would never even consider a 460 RDM. Might even sell my 430 and 400 RDM`s from experiences I`ve had !! Cant see point in having a tougher mast if it results in a less efficient sail..

Whatever ... you are 105Kg and you are basing your conclusion on one mast that does not fit you. There are whole lines of sails out there (e.g North or Hot) built around a single RDM mast covering 4.0/4.5 to 6.0/6.5 ... who knows if a RDM has more or less range than a SDM (whatever range means). And your observation that a more flexible mast has less upper range makes actually little sense, hard to tell what it is going on but it might not be what you think it is. A softer masts, SDM or RDM, should make overpowered sailing easier: you might loose some power, bottom end, but you gain control.

As far as weights, who really cares, but compare any numbers out there and you will see that a 70-80% SDM has roughly the same weight of a 90-98% RDM. To see a weight gain you have to use a 100% SDM or compare with a 65% RDM.

nakaniko
4th June 2011, 03:57 AM
Forgot one thing.
What about the weight of rdm extensions??? I mean human-priced alloy type. The first time I got one I couldn't believe at it, 2x times than a sdm extension? And 2 time the price! I mean I've bought 4 rdm externsions, two common Ascan from Deutscheland, cheap and strong, but also a Chinook (something to complain about it), and a famous french one i don't remember
Standard: they are not. All 4 extensions are not snug fit in my Fiberspar, someone told me its because does exist a even smaller version, the super-rdm that is 2 mm less in inner diameter. I tried to solve the problem with a sheet of plastic, but the shorebreak of Rømø glued the nasty end cap of the Chinook inside, hard work to solve the problem..Never had similar problems with even old and weird sdm extensions
No debate that at least with wave mast rdm is the future, but I think that 20+ years of developement in SDMs were not useless, so RDMs need to still work on them, don't you agree?

Unregistered
4th June 2011, 05:27 AM
My first line was

"I`ve no doubt SDM are tougher and perfectly OK on some sails (ie the ones designed for them) but I`ve given up on them"

My observations are neither based on one mast or one set of sails but they are my observations !

Perhaps you should do some training; put on some weight and see if your observations on mine are justified !!!

A sailor at 70k can not comment on a sailors observations at 105 k and vice versa re over powered/stability. Your comments re flexible mast been more stable are simply wrong..

Flexible mast will twist off earlier to depower rig which is completely different to making sail stable ; your sails would be depowering too early for me which is exactly what is happening when I rig up on RDM.

Think about it Davide; when I`m sailing just normally powered up the sail is already operating at levels you would sense as overpowered !!!(It is nothing to do with ability/skil or anything itis just plain physics/weight.

The point is FOR ME RDM masts on the sails I am using are too flexible.

There has been a lot of market manipulation getting sailors to convert over to RDM. For some it is both a retrograde and expensive one.

Have you done any back to back testing recording boardspeed and windspeed with your sails on RDM and SDM ???? I have.

You stick to RDM (you can buy mine) and I`ll stick to SDM.

And my comment was relevant to original posters findings.

Unregistered
4th June 2011, 05:51 PM
I think clue is thread title ....
In Praise Of SDM masts ????

BelSkorpio
5th June 2011, 05:59 PM
I've broken yesterday 2 100% carbon SDM 490 masts on the same day.
Bitter taste in my mouth ...
1 mast just snapped on the beach, while it was laying +/- 1 hour in the sun. I know I should not do it, but it happened.
The other snapped on the water after pumping, so I had to swim +/- half an hour. :(

My 8.8 race sail needs a SDM mast. I'm thinking of buying a 75% carbon SDM mast (in stead of 100%).
Do you think they are generally stronger ?

Unregistered
5th June 2011, 06:26 PM
I think they are !

Few years ago I was rigging a cambered NP on beach at Sotavento. Mast broke as I downhauled it (a NP X9) They brought me another. ( I was hiring kit luckiliy) and it broke again as I applied DH !!! Chose another rig !!!

My longest mast is 490 so weight penalty on 75% isnt too bad. Only use Tush 75% now. (last 5 years) Yet to break one !!

Floyd
9th June 2011, 06:52 PM
Tend to agree with original poster. Think its to do with weight.Heavier sailors seem to prefer SDM .For same weight they are stiffer , by definition. Strength /stiffness propotional to depth ???

Unregistered
10th June 2011, 08:53 PM
Tend to agree with original poster. Think its to do with weight.Heavier sailors seem to prefer SDM as I do.
For same weight they are stiffer , by definition. Strength /stiffness propotional to depth ???

that is not true "everything else being equal, then an sdm will be stiffer than an rdm" may be true, but same weight could mean wildly different materials and construction techniques.

Im 95kg and use RDM masts on sails cut for RDM masts and am perfectly happy with them. If the sail is cut for the RDM masts there should not really be any issue.

Floyd
10th June 2011, 09:16 PM
Ok
Should have said for same weight/same carbon content/same construction/same laminate direction etc etc SDM will be stiffer and stronger (OK not tougher) than equivalent RDM. !!!!

Cant change physics. Strength (and stiffness?) is/are proportional to depth. (ie in this case diameter )

IAnybody who has converted over to RDM as an experiment try your sail on an SDM ???? See how it feels.??

davide
10th June 2011, 10:27 PM
Ok
Should have said for same weight/same carbon content/same construction/same laminate direction etc etc SDM will be stiffer and stronger (OK not tougher) than equivalent RDM. !!!!

Cant change physics. Strength (and stiffness?) is/are proportional to depth. (ie in this case diameter )

My 430 RDM would only cover 4.7 to 5.4. Which is probably why they are been pushed at us !!! New bases and more masts for us to buy !!!???


It is the thickness that makes RDMs masts so strong: to make a SDM as thick as a RDM it would weight a ton.

And in this case the conspiracy theories are quite misplaced: my Hot Sails HotRod 430 is used from my 4.7 Superfreak UL (you could go even smaller if you wanted), and is the recommended mast for my GPS 6.6, a race sail requiring 24cm extension. Quite a range of use: one mast for one of the softest sails around, used in extreme B&J, all the way to a multi-cambered sail. In addition tops and bottoms of the mast line are all exchangeable, so you can buy just the bottom of the next larger mast if you need something longer. Hot Sails and others have whole lines of sails that are designed to be rigged on a single RDM mast, take the Liquid: 5.0 to 7.5 can be rigged on a 430.

How a sail designed for a RDM would work with a SDM, and vice-versa? Who knows, some would work worst, some maybe better, some the same. What's the point?

sergio k
10th June 2011, 11:04 PM
In general, lighter guys <70kg prefer RDM in most cases, and >100kg prefer SDM, if you weight is in between things are a lot more blurry... case closed.

Floyd
10th June 2011, 11:53 PM
Davide
Putting it other way around
An SDM doesnt need the thick walls to be strong/stiff.;but the thinner wall makes them more fragile.(A relative term)

I

davide
11th June 2011, 12:23 AM
I`ve yet to use an RDM on a sail over 5.4 that I`ve been impressed ;infact I`ve hired 5`s on RDM and swapped them for same rigs on SDM but totally agree with Sergio over the weight classification/choice.
Think I mentioned earlier I`m 105 kg;we are almost involved in different sports !!!???
Yep, that's a gap in weight! although you might want to check out http://martynogier68.blogspot.com/ Martyn Ogier is 110Kg and he was rated 2nd fastest in the world speed circuit last year, just in front of Dunkerbeck. Last time I noticed he was using RDM + Hot Sails GPS (not sure what he is using this year) ...

Floyd
11th June 2011, 01:32 AM
Bet he`s not buying them !!!

Floyd
11th June 2011, 01:48 AM
This is another debate that will run a nd run. Just checked boards Forum to see what opinion was on there. Rik (of Rik`s Windsurfing) posted this;
Originally Posted by Rikster


"A RDM sets a sail flatter so immediately you have less power from a standing start. In use the softer relative flex of the smaller diameter spar prevents the sail from delivering the same amount of power as the SDM. The extra deflection causes draft instability when sailing heavily powered-up.

Like with so many things it’s all rather subjective to the user, the conditions they sail in and the equipment combinations being used. I know many sailors swear by the softer more forgiving flex the RDM provides but that is often making up for other deficiencies (technique or equipment set-up). In general terms however, easier conditions that do not require the extra strength of the RDM benefit from the extra power and wind range offered by the SDM. "

Best regards,

Rik
This is the NP line on issue. I use NP sails ...nufsaid.

davide
11th June 2011, 03:41 AM
Bet he`s not buying them like us though !!!

Not sure what this is supposed to mean ... he is 110Kg and using RDM he almost won the world speed tour, and you just said that RDMs were not good for people above 100Kg ... I don't personally care if they are or not but this is just a counterexample to show that you can happily compete at the highest level on a RDM as a heavy-weight ...

As far as the (cherry picked!) comment of the guy from ... rik's windsurfing (sic) ... sails do not rig more flat on a RDM (or fatter on a SDM, sigh ..). Sails rig exactly as they are supposed to rig by design on a specific mast, RDM or SDM. (I'll skip commenting on range ... my 6.6 GPS is very happy when people are on 4.7s and I am 72Kg).

BTW to talk of RDM vs SDM is actually silly. For optimal performance a sail should be rigged on the mast it was designed for. One should not rig a sail designed for a, say, SDM NP on a, say, SDM North. This of course, unless you want to buy a dozen of SDMs from different manufacturers and investigate which one give you more "performance"!!!!!!

Ok, off to go sailing: 20knots in the forcast!

Floyd
11th June 2011, 06:16 AM
Davide
The thread is
In praise of SDM masts
I didnt say RDM dont suit sailors over 100k,they obviuosly suit some; but not many.Basically those using sails specifically designed for RDM`s !! i

Totally agree with unreg posters comments re IMCS been very flawed. There is just no way a 430 RDM is as stiff as a 430 SDM ; but perhaps I`m wrong .

davide
11th June 2011, 09:30 AM
But then I might have been wrong assesing my sails over last 30+ years sailing ! I should sell my SDM`s and buy RDM`s and put up with the poorer range;less stability and worse top end they give MY SAILS !

Totally agree with unreg posters comments re IMCS been very flawed. There is just no way my 430 RDM is as stiff as my 430 SDM ; but perhaps I`m wrong with that too !! Davide Knows best ???

PS Buy a dictionary and look up RANGE.

Weeeeee! Nice flurry of unpleasantries, bordering on personal attacks ... classic e-mail syndrome and this is when I stop chatting on a forum, I am sorry I got trapped in this silly thread. RDMs or SDMs is all good ... let's just enjoy sailing: great day today at Crissy! and tomorrow is another 20 knots+

Unregistered
11th June 2011, 05:33 PM
Davide
I said they dont suit my sails; Neil Prydes;

well there is your mistake
you should get some decent sails and you wouldnt have any more problems

Unregistered
11th June 2011, 05:41 PM
there is no problem with IMCS, there is a problem with bullshit marketing which prints numbers that are not real.
Most RDM masts are softer in the base/boom area than most SDM masts.
If you then use a soft based RDM in place of a stiff based SDM it will flatten the sail in a way as described by Floyd and others.
Some SDM masts are flexy in the bottom and stiff in the top and bend much like most RDM masts.
Some RDM masts are stiff in the base and flexy in the top and bend much like most SDM masts.

Unregistered
11th June 2011, 06:00 PM
And Davides` unpleasantries ???

"and it is really a no brainer which one to choose in the waves or B&J."

"and if a mast feel too soft with a lot of extension for a 105Kg it just means ... it is the wrong mast for the application"

"I personally wish RDMs were the industry standard: this sport can use some simplification! "

"Whatever ... you are 105Kg and you are basing your conclusion on one mast that does not fit you."

"It is the thickness that makes RDMs masts so strong"

"sails do not rig more flat on a RDM (or fatter on a SDM, sigh ..). "

"BTW to talk of RDM vs SDM is actually silly."

No wonder Floyd was a bit unpleasant !!!

Unregistered
11th June 2011, 06:02 PM
They dont suit my Rocks either !!! And they are supposed to !!!

nakaniko
11th June 2011, 06:14 PM
For sure I never wanted to cause an argument between us windsurfers, I only wanted to tell what nowday few people tell, that SDM in some situations have some advantages in the most common situations for us windsurfers, that is to say free sailng in bays and lakes; for sure strength and handling in waves are best in RDM.
Davide, as I can read on the instructions booklets given with "our" (fantastic) HSM sails, JH tells that we can use on them both SDM and RDM, changing the sail response that is more steady and bump&jump with sdm and more loose and forgiving with rdm. So I simply do both things, and because of the well known lack of often wave conditions of the unlucky north east of Italy, at the end are the SDM that are mostly used: 16 days of sailing, 16 sdms days.
As told, selling the SDM I would have get 100-150 euro for three masts which had total retail price of about 1.000 euro, so choice of keeping them was obvious. And so I have a spare mast in case of a breackage.
I know that the more the time pass, the less easier is that sailmaker keep on making sail really compatible with SDM, but this imho is a mistake, as masts can lasts for 20 years and more, so this way you close the door to a lot of people wanting to learn windsurf end buying stuff used at cheap price, like on much places in the world. I don't think sending out of market the SDM would help windsurfing, imho...
HSM are really compatible with SDM, other brand's sail they tell me that trying to rig them - even stated compatible - on a SDM is a nightmare (some Simmer's f.e.). Also between my 2008 HSM the difference is noticeable, little hard with Fires, good with Smacks, very good with the Superfreak (because it's 8,0?)
So, as seems to be clear that SDMs stil their advantages in many situations and for some kind of riders, why not keeping the compatiblity? We are the ones that finally cause the choiches of the brands, so imho we have to choos brands that give this opportunity, leaving the others in the stores unsold!
BTW, unreg, I don't find real unpleasantries in Davide's words, it's simply a point of wiew.

Floyd
11th June 2011, 07:00 PM
There is an industry standard. Its called SDM. Standard Diameter Mast.(or there used to be!)

Floyd
11th June 2011, 07:21 PM
The Grand Prix Speed is designed to be used only with RDM masts .

The GPS is designed for the Hot Rod RDM mast, but is SDM compatible, supplied with an extra set of cambers.

Both above comments taken from Hot Sails site. Same sail,same year,one in main web part other in PDF rigging guide !!!

Not very helpful !!!

Floyd
11th June 2011, 07:44 PM
Standard diameter (SDM) or reduced diameter (RDM)?

RDM – Advantages:

•Thinner in the hands, many prefer this feel in transitions where the mast is held.
•Thicker wall, more durable
•Relatively softer in the middle for a springy feel
•More suited to wave & freestyle applications


SDM – Advantages:

•Lighter for a given stiffness
•Range of top section stiffness available for speed/slalom applications
•First choice for camber induced sails
•More locked in feel with better top end performance
•More suited to freeride, slalom, racing and speed applications.
•Floats better for easier water starting


Generally speaking it’s obvious that the SDM is the natural choice for larger sails, for speed, slalom, and light/medium wind freeride. Conversely, the RDM is popular with wave and freestyle sailors.


Lifted from Tushingham site !!!

Unregistered
11th June 2011, 10:16 PM
There`s no comparison between Hot Rods and any other RDM !!! (Probably Naish ?)
They are nearer in stiffness/performance than any other RDM to SDM ???
Hot Sails dont recommend any other mast apart from Hot Rod with any sail needing 460 !!(for GPS)
All other RDM`s too flexible ???(Especially in base ?)

Davide`s perference is not to RDM`s ; its to Hot Rods. !!!
All others dislike of RDM`s is not against Hot Rods but "normal" RDM`s.

Perhaps others should try Hot Rods (But they are £328 each !!! ouch) before they judge.???
Perhaps Davide should try other RDM`s before he judges others assesments of RDM`s ???

Reckon Tushingham site summed it up best ! (But thats not Hot Rods !!!)

Sailing gets more complicated every year !!!

We get further and further away from standardisation !!!

We should be able to rely on IMCS for comparison. We obviously cant !!!

Personally I have also found my RDM`s (Amex)more flexible than expected.

Unregistered
13th June 2011, 03:19 AM
We should be able to rely on IMCS for comparison. We obviously cant !!!

The IMCS system is perfectly reliable. The problem is that manufacturers lie about the bend curves of their masts. If everyone told the truth and stated the real stiffness and real bend curve numbers of their masts then you could rely on the IMCS.
re hot rods, they are stiffer based than most (not all) other RDM masts but they still have more bend low down than the majority of SDM masts. They also bend very differently in the different sizes, the 430 for example being very flex top but the 400 no where near as much,but quite stiff overall and the 370 being very soft.

Unregistered
16th June 2011, 05:49 AM
Having used my hotsails gps 7,3 with hotrod 460 quite a bit I can say that i really liked it. HSM build quality and ease of use were great. Then switched to challenger sails and a north platinum mast recently and can comment that I miss the build quality of HSM compared to challenger sails. Even tough the HSM hotrod combo was very nice to sail i think that I can tell a difference that the NS platinum mast feels a lot stiffer. I also think the term SDM is really missleading, it means that you can use a sdm extensiorner but different brands use different amount of drop shape so camber fit can be a problem. The rdm was great for free sailing but I belive that an sdm is the way to get best performance for larger sails (460).

nakaniko
16th June 2011, 03:46 PM
I'm a bit surprised about some statements over Hot Rod masts from Hotsails. I use Fiberspars on my full quiver of HSM and I get very good shape both with sdm and rdm. If the sails would have been designed over so strange masts like told I don't think I could get the seme result using my Fiberspar, I should get very different answer when using f.e. Fire 4,5 or Smack 5,5, shaped on the Hot Rods 400 and 430.
About GPS I've never used them, I avoid cambered sails, but I know that only in 2009 they were rdm-only, now they are provided with another set of cambers for sdm masts, they tell me; and so for masts not produced from HSM...
In any case nowaday every sail brand suggest only their own masts. but on the specs of HSM sails booklet is clearly told that you can use successfully other various brands, sometime even suggesting what brands gives good answer (and so you can understand what brands don't).
This was intended like a post about sdm masts but in defence of HSM I want all to know that I've casually met HSM sails but since that time I've never found the same quality, durability, and easiness of use (also with different masts!).
Coming back to the topic, I thnk that a waveproof mast has to be stronger, so they have to build it with a thicker section. But not necessarily in reduced section, imho. So I don't know what were the reasons to change the standard. Anyhow rdm is nowaday a standard like sdm