Ok. Am happy to be shot down on this one... but just wondering...
I'm 70kg and have always used a mast one size smaller (rdm) than that recommended by the sail manufacturer. I have always found this setup has more forgiving characteristics when I'm sailing and a gush hits. I usually use 30cm tip extension of conduit or have tried carbon tube from SUP paddle. I have experimented with 15cm tip extension + 15cm more on the base extension also.
My question is... on my sail that needs a luff of 465 and a 460 mast recommended (imcs 25), would it be at all possible to use a LONG base extension (Streamlined) out to say 35cm + a 30cm tip extension coupled to my 400 mast (imcs 19)... or is that just too flexible to work at all?
(Both sail and mast are constant curve. )
Select to expand quotemikey100 said..
or is that just too flexible to work at all?
Worth experimenting with. No matter what anybody says, the circumstances won't be exactly the same as what you intend.
My head has come up with a 50/50 chance of success.
Or maybe you could look for a softer constant curve mast?
Select to expand quotedecrepit said..mikey100 said..
or is that just too flexible to work at all?
Worth experimenting with. No matter what anybody says, the circumstances won't be exactly the same as what you intend.
My head has come up with a 50/50 chance of success.
Or maybe you could look for a softer constant curve mast?
Softer??? Thought the 400 mast at a stiffness of 19 replacing a 460 with a stiffness of 25 means it would already be too soft. But then again, a stiff alum base extension has got to stiffen the bottom section.
...or did you mean a softer 460 mast... do they make them?
I take it you don't have a 430? I assume you're using a camless sail.
I use a 370 in a 4.7 with 46 extension and it feels verging on noodly but I like it particularly as it releases the gusts without pulling me over. I'm light too. That's 12.5% extension. The equivalent on a 400 is 50 extension and you want 65. My guess is it will feel too noodly. You can but try.
Just my 2c
Have a 430 that I use with extension on tip (15cm) and base at 20cm... but was just wondering if using the 400 with 30 on tip and 35 on base would be far too flexible or 'noidley'.
Select to expand quotemikey100 said..
...or did you mean a softer 460 mast... do they make them?
Yes, thay's what I meant, but no idea if there are any.
My friend uses one of these North mast extensions, and it seems to work for him. I think he uses it with a 400 mast and rigs it with a 4.7m up til a 6.7m (I think).
I have not used it so I don't know if the combination has any limitations. I tend to use the exact mast for the sail, only because I have them.
I forgot to include a link:
www.surf-store.com/windsurf-bases-extensions/
Select to expand quoteFormulaNova said
I tend to use the exact mast for the sail, only because I have them.
That's probably the best unless your under 60 kg or over 110 kg.
Isnt 80 kg what things are designed around ?
Its odd that EVERYTTHING windsurfing is biased on wind strength and skill and absolutely nothing on other than average weight ?
I think I have ideas on boards that would work for heavy guys but they don't make them .
Select to expand quoteImax1 said..FormulaNova said
I tend to use the exact mast for the sail, only because I have them.
That's probably the best unless your under 60 kg or over 110 kg.
Isnt 80 kg what things are designed around ?
Its odd that EVERYTTHING windsurfing is biased on wind strength and skill and absolutely nothing on other than average weight ?
I think I have ideas on boards that would work for heavy guys but they don't make them .
With the Ezzy masts I use, in theory I could cut down the number of masts I need.
I should be able to use a 490 tip with a 430 base to get a 460. So, I could get by with a complete 430 mast and a complete 490 mast that would do me for all sail sizes from 5.0m up until 8.5m. I have the 460 anyway, so I use that, but in theory I don't need to. I should actually rig the combinations and sail them to see if I notice any difference.
In retrospect, masts are a non issue for me these days. Before, I had SDMs and I use to break them. Since getting the Ezzy RDMs, and adapting my sails to use them, I haven't had any breakages. From memory, maybe the 490 on the 8.5m is a bit softer than an SDM, but its a compromise I can live with.
as a heavyweight ... i keep RDM under 490
Bruce Peterson of SailWorks agrees with me
"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."
So, what is the difference that I will see when using an RDM versus SDM in the larger sizes. I'm about 95kgs, so I often use the larger sails.
I still have SDMs for the larger sails, so I could try them back to back, but it never seems easy to swap back and forth given that wind conditions change so much.
Am I going to be losing power in the 8.5m sails with an SDM versus an RDM?
Yeah, I wonder. Its not like the sails are noticeably spilling wind out of the top, but without the same sail rigged with a different mast, its hard to compare them back to back.
Since going to RDMs I find rigging is so much nicer. Gone are the days of some masts not fitting easily into some sails. Another positive is that I use the Ezzy mast shim with a boom setup for a SDM mast, so the boom never slips. I don't miss those things at all, and just thinking about it now makes me appreciate them even more.
Changing the topic slightly, has any manufacturer had a decent run with a 3 piece mast? It would seem like a good idea for transport if nothing else.
I love a 400 rdm(imcs 19)with a tip extension in my 6.3 which recommends a 430(imcs21).
Have set up a 430(imcs21) with tip extension in my 7.1, which recommends a 460 (imcs25).
Guess I will have to just try that 7.1 with a 400 + 30cm tip extension + 35 on base to give recommended 465... and see what happens.
Ok. Rigged my 7.1 KA Race on a 400 rdm with 30cm mast tip extension and a base extension to 36cm giving correct luff length. (Recommend mast 460)
It looked good. A little flexible in the upper half! Next step will be to try it on the water and see how it goes when there is wind on it.
Select to expand quotemikey100 said..
Ok. Rigged my 7.1 KA Race on a 400 rdm with 30cm mast tip extension and a base extension to 36cm giving correct luff length. (Recommend mast 460)
It looked good. A little flexible in the upper half! Next step will be to try it on the water and see how it goes when there is wind on it.
Keen to hear how that goes,
Breaking news.
Johnski just broke his mast extension rigging a sail at close to max extension. He just stepped on the board and it snapped.
Select to expand quoteImax1 said..FormulaNova said
I tend to use the exact mast for the sail, only because I have them.
That's probably the best unless your under 60 kg or over 110 kg.
Isnt 80 kg what things are designed around ?
Its odd that EVERYTTHING windsurfing is biased on wind strength and skill and absolutely nothing on other than average weight ?
I think I have ideas on boards that would work for heavy guys but they don't make them .
Im curious Imax what ideas?
Mikey100 I think all that extention top and bottom would be way to soft and flexible.
how can you get the MOST out of your sail when you play around like that ??
sail manufacturers give us recommended mast - to use it to it's fullest
there is some leeway, but like this ?? 
NOT for me !!
As I said in my opening comment, am thinking WAY out of the box and am happy to be shot down on the idea. I think it is too far from what the manufacturer designed as being the 'perfect' setup. But I just had to rule it out as an option before completely discarding the idea.
Dry rigged it looked good, but the proof will be in the sailing.
Totally with you mikey, if you don't experiment you don't learn.
If you happen to be the same weight and height as the testers the recommended stuff should work OK for you, but even then you could find a better set up for your particular conditions.
If you are in the light or heavy weight divisions, then it's more likely a non recommended set up will suit you better.
guess my "experiments" with masts were less than ideal
and this one pushes the envelope
and i am true heavyweight too
I'm not even a heavyweight, 165Lbs. (whatever that is in metric), and I stay away from long base extensions, I've bent 3 of them in the past, using manufactured holes near the top (never add holes past the manufactured ones). Only medium length ones for me, with the proper length mast, and even with those, I don't like to use the holes near the top.
I agree that a long extension with too little up the mast is courting disaster... but I feel confident with 28cm up the mast.
Select to expand quotedecrepit said..
Breaking news.
Johnski just broke his mast extension rigging a sail at close to max extension. He just stepped on the board and it snapped.
Carbon or alum extension? What brand so I can keep away from it?
Select to expand quotejoe windsurf said..
the looong one 
Which 'looong one' broke. - Severne, North, Chinook....? I am using the 46cm Streamlined. It seems bulletproof.
Select to expand quotemikey100 said..
Carbon or alum extension? What brand so I can keep away from it?
It was certainly carbon. But I didn't take note of the brand.
Cool. Mine is alum. ?? I feel safe with it. Could use is as a weapon in a zombie apocalypse.
