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According to North Sails RDM masts are not good over 430 length, as a lightweight i have 460 skinny and love it. no issues with two different mast brands at this length(Severne and Hot sails). In fact Hot sails recommend RDM mast for their 8m GPS slalom sail. I think for non PWA sailors, even 460 has lot of benefits in RDM. I'm not sure about this claim by North Sails

From the North brochure
"Not everyone
<div data-canvas-width="283.931">knows that RDM masts make sense only up to lengths of around

<div data-canvas-width="275.0400000000001">430 cm, since they show a rather soft flex behavior as a result

<div data-canvas-width="259.11600000000004">of their smaller cross section. Therefore, they are primarily

<div data-canvas-width="280.04099999999994">suitable for Wave/Freestyle sails with the additional advantage

<div data-canvas-width="282.74199999999996">that they are easier to grip during maneuvers. On the other hand

<div data-canvas-width="283.68800000000005">large, mostly performance-oriented sails need stiffer masts with

<div data-canvas-width="275.43900000000014">a “more direct“ flex. This characteristic demands a larger mast

cross section in order to ensure reaching the required stiffness"

Try to correct

"
Not everyone knows that RDM masts make sense only up to lengths of around 430 cm, since they show a rather soft flex behavior as a result of their smaller cross section. Therefore, they are primarily suitable for Wave/Freestyle sails with the additional advantage that they are easier to grip during maneuvers. On the other hand large, mostly performance-oriented sails need stiffer masts with a “more direct“ flex. This characteristic demands a larger mast cross section in order to ensure reaching the required stiffness"

Gidday sonny ..RDM mast are softer true ..me and a bunch of mates all use 80-100% RDM 460 's ,we ocean sail a lot so ..more control .especially when you have swell and need the extra flexing of the mast .
I understand what north are saying ..with the Sdm mast being better in ...flatter water ..as it gives you more drive ..and bottom end with cammed and bigger sails.
I use both depending on the conditions ..and have noticed this from experience in using both ..
but I'm with you ..I like the RDMs .. Better .
Every sail is different and behaves different With the mast you put in it ...some sails are awful with RDMS ..NO GRUNT .to soft.
I have just changes sail brand s to Ezzy ..they work perfect with both ..
I reckon use what feels good to you ..but Im sure they would love to sell you another mast .
I have had north sails in the past ..and they do like the correct mast ..they are fussy ..but still nice sails .
i still have a 5.9 ego and it ONLY works with a 430 RDM . It's still a fav.

I think it's personal, I am heavier than most at 110, I use rdm up to 490/8.6m. The power gain of sdm is good only if you can use it, otherwise you will go faster if you're in control & comfortable. I think the most important thing is sail designed properly for mast, I've used alot of sdm/rdm crossover sails & yes at around 6.5m 460 luff they feel crap. Yet loft could design sails that happily run to 8.6 on rdm & feel good.

Power & stability can also be designed into sail, my lofts have a much greater tuning range than my severne r7.

Naish year dependent I think make 460rdm, loft go bigger nice masts to use but quality a bit hit & miss. Loft have moved away from this now as they've sold out & gone to cliche marketing.

I have been messing around with RDM / SDM substitution a lot. What I have found is that the larger the sail is and the more luff round it has the more noticeable the difference between RDM and SDM becomes. In general Wave sails have less luff round than cammed /race sails and are far less sensitive to mast bend curve and successfully run on RDM in fact most are now designed for RDM. It is when you get to the larger Race or freerace sails that you start to notice the difference. For example I recently needed to rig a KA Koncept 7.5 on an RDM as I broke my SDM 460. I started on a 460 RDM with the recommended bend curve but the sail set too flat at boom height. I then tried some old sampe RDM masts I had that were more flex top, around 15.0 and the sail set really nice.
So in my opinion you can run Race/freerace sails on RDM up to around 6 to 6.5 but once you go larger the sail will set flat and lose bottom end. If you run a more flex top RDM mast than recommended it will work better on bigger sails. Sails like the Ezzy that are designed with far less luff round do work more successfully on RDM in the bigger sizes.

The Hotsails Maui 8m GPS rigs sweet on the recommended HSM RDM 460. No issues. Guess you just gotta pick the right brand if you want to run an RDM in your race sails.

Guy Cribb says RDM below 460, SDM - 460 and above. He is sponsored by Neil Pryde, however, who don't make 460 RDMs.

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N1GEL said..
The Hotsails Maui 8m GPS rigs sweet on the recommended HSM RDM 460. No issues. Guess you just gotta pick the right brand if you want to run an RDM in your race sails.

+1. I think if a large sail is designed to run on a rdm then it can work. The GPS certainly does. My 8m has buckets of power, gets my 115l board going in 12 knots. The top end isn't bad either, I can use it comfortably up to 18 knots and gusts up to 20+.

i think the other major benefit of the skinny is the soft feel it gives the sail, it really makes the ride smoother, less jolts transmitted through the rig. I think you lose a bit of crispness and top end (Compared to my Rs slalom) but theres not much in it.

See below, lots of shape around and below the boom, the sail follows the profile of the boom. I've tried this sail with an SDM ( it comes with both SDM and rdm cams) and i really prefer the ride with Rdm.

ps. This is not a plug for hot sail GPS, just my observations. I also use loft and Neil Pryde sails.







Profile on the water


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The big boys won't change if the market keeps swallowing the can't do 460 RDM, 7-8m range BS and keeps spending $ with them.
Hot/Loft/Severne/Ezzy and others all have great sails that work on RDM 460's
SDM's are so stuck in the old tech, spend your $ with a brand that works with RDM.
when I'm looking at sail spec's for brands as soon as I see SDM I move on, once you've had skinny you can't do fat!

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Waiting4wind said..

N1GEL said..
The Hotsails Maui 8m GPS rigs sweet on the recommended HSM RDM 460. No issues. Guess you just gotta pick the right brand if you want to run an RDM in your race sails.

+1. I think if a large sail is designed to run on a rdm then it can work. The GPS certainly does. My 8m has buckets of power, gets my 115l board going in 12 knots. The top end isn't bad either, I can use it comfortably up to 18 knots and gusts up to 20+.

i think the other major benefit of the skinny is the soft feel it gives the sail, it really makes the ride smoother, less jolts transmitted through the rig. I think you lose a bit of crispness and top end (Compared to my Rs slalom) but theres not much in it.

See below, lots of shape around and below the boom, the sail follows the profile of the boom. I've tried this sail with an SDM ( it comes with both SDM and rdm cams) and i really prefer the ride with Rdm.

ps. This is not a plug for hot sail GPS, just my observations. I also use loft and Neil Pryde sails.

I actually found the HSM GPS 8m (pink) power improved a lot changing to a SDM (Severne 90%) after using the rec. RDM (Hot Rod) for more than a year.

RDM is more forgiving when over-powered though (as expected).

Used with a Mistral 137. Cheers JJ

I have from 7.8 to 5.2 of Overdrives R6, they are all set on RDM, sail rotation is super sweet, can't complain about anything really, well buit sail that works sensational and is super comfortable. My sail size that I mainly use is the 7.0 in around 20 to 30 knots and it very responsive. Keep up the good work Severne. Looking forward to the R8..

I use rdm only and they feel good this pic is with a 460 rdm hot rod on a 7.3 lots of power and control.

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nudist said..





I have from 7.8 to 5.2 of Overdrives R6, they are all set on RDM, sail rotation is super sweet, can't complain about anything really, well buit sail that works sensational and is super comfortable. My sail size that I mainly use is the 7.0 in around 20 to 30 knots and it very responsive. Keep up the good work Severne. Looking forward to the R8..

Cripes I use my 7m in 12-18kts.. I wonder what effect that hason performance and handling.? I supposed they are more designed for heavier ( 80kg + ) riders and more wind..

Now now, 92 beers all day long

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JonesySail said...
The big boys won't change if the market keeps swallowing the can't do 460 RDM, 7-8m range BS and keeps spending $ with them.
Hot/Loft/Severne/Ezzy and others all have great sails that work on RDM 460's
SDM's are so stuck in the old tech, spend your $ with a brand that works with RDM.
when I'm looking at sail spec's for brands as soon as I see SDM I move on, once you've had skinny you can't do fat!

Well, I just voted for 460 RDM with my wallet.

Good decision! I've never seen an RDM break in the rigging area, but have seen plenty of SDMs go pop.

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MrCranky said..
Guy Cribb says RDM below 460, SDM - 460 and above. He is sponsored by Neil Pryde, however, who don't make 460 RDMs.

Guy Cribb will not buy you a new SDM extension and rescue you when your SDM mast breaks!

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MrCranky said...

JonesySail said...
The big boys won't change if the market keeps swallowing the can't do 460 RDM, 7-8m range BS and keeps spending $ with them.
Hot/Loft/Severne/Ezzy and others all have great sails that work on RDM 460's
SDM's are so stuck in the old tech, spend your $ with a brand that works with RDM.
when I'm looking at sail spec's for brands as soon as I see SDM I move on, once you've had skinny you can't do fat!

Well, I just voted for 460 RDM with my wallet.

Hope that will make Mr Cranky less cranky!

Nigel is spot on, takes a lot to make an RDM break, unlike SDM which i think maybe is an acronym for 'Snapped Da Mast'