Extensions change the mast curve so you can't have a 4.6 and 6.0 on the same mast with tons of extension.
That is why most sails have a sweet spot in the range also.... liek my wavesails, i get 4.2, 4.7, 5.2 on the same mast and the 4.7 feels best by far as the other two are at the extremes for a 400cm mast.

Sounds like you have a 400?

A 430 will allow you to use 5.2 (just) up to about 6.5 so perhaps that should be your next buy

I am not engineer to consider details, but if you think about first bottom half ? What is the curve and how important is here for sail performance ? It is not very likely that bending your mast below your boom has any effect at all.
So if you have first half 200 cm and second 200 or 230 or 260 properly designed ?
The only problem is linguistic i can see that one "half" is shorter then another "half".
Problem could be easy solved by designing mast consisting of 200cm + 200cm and 30 or 60 cm inserts.
Anyway that is only matter of time that technology will come to mast and parameters will be adjustable - using carbon fiber strings - tightener-tensioners to allow mast to be stiffer or softer on demand. Ski manufactures solved that problem ages ago.

The next should be oval - or "drop shape" cross section instead if circular.
Every sail designer will agree that top of sail should work and behave differently in axis X Y and mast should be say stiffer in longitudinal and softer in lateral movements.

Mark _australia said...

Macroscien said...

I am not engineer to consider details, but if you think about first bottom half ? What is the curve and how important is here for sail performance ? It is not very likely that bending your mast below your boom has any effect at all.

It does bend below the boom and is important.
Indeed if you have a big long 40cm + extension and use that in the mast with your smallest sail, so you have 40cm of extra pipe up inside the mast, it stiffens the bottom of the mast and changes the sail set considerably (worse of course)

Sorry dude, if you could have one mast and 3 cheap extensions to cover 4.0 - 8.0 and it worked, it would have already been done.

I like this reasoning. "everything that could, is or was already invented"...

For those of us that have been around this sport for a long time, much of what you say we have seen in the past.

There was a time when you bought one 460 mast and used it on pretty much everything except the absolute largest of sails. You used long alloy extensions, or extendable turbans in the top of the sail, and that was just the way it was. But now days the sails are much more refined, they are developed around bend curves and rely on the way a mast works to function correctly. Sure you might get away with doing what you have suggested, but you will be asking yourself why the guy with the same sail is going faster, looks more comfortable and seems to get more range out of his sail... simple the mast.

There have also been masts developed to have different bend characteristics on the different axis of the mast, however they used carbon strips on a fibreglass mast... don't see them anymore cause it was tried and of no real value. But it may come back, just like the twin fin did.

Scotty Mac said...

If you buy an ezzy 400, you could buy a half a 370 also. The top and bottom halfs of the different sizes fit, a 370 bottom with a 400 top gives you about 390. That way you could go from 5.3 down to about 4.2 with one and a half masts.....

I did it for a couple of years and it works fine.

I use one and a half ezzy rdm masts to span 4.5-5.3-5.9-6.6 and works a treat!

If using down to 3.7 though you may need two and a half ezzys depending on the biggest sail you plan to use, which will probably need a 430 if its around 5.5-6.5.

I heard some talk of three piece masts a while ago but don't know if this a reality yet!

check out the three piece north mast set up, pretty cool, and they work well, they also make proper carbon mast extensions in 400mm increment, good for your 400 mast if your use a 6.0m sail once in a while, with out having to shell out for a whole new mast, strong??? there will always be sceptics, compromise; an extra 100 grams....

checkit http://www.north-windsurf.com/en/masts/CARBON.XTENDER

Macroscien said...

I have collection already ranging from 3.7 , 4.0 ,4.3 4.6

Curious to know Macroscien where you use a quiver like that? Has Huey (the wind God) delivered more wind than you wished for, or do you weigh around 30kg?

GazMan said...

Macroscien said...

I have collection already ranging from 3.7 , 4.0 ,4.3 4.6

Curious to know Macroscien where you use a quiver like that? Has Huey (the wind God) delivered more wind than you wished for, or do you weigh around 30kg?

Just patience and wait for FAT BIG GREEN ARROWS

Last time I used small grear conditions were like that ,

Wind gusts > 40 knt on Shearwater, Gold Coast
I am 80kg and I took JP 92L wave, 4.0 mast and 4.2 sail KA Kaos
My son 62kg , Naish crossover 84L , 3.7 mast and Naish 4.2 sail

To be fair I had difficulty to control everything, and was so fad up with conditions. Conclusion was everybody could reach or over reach limit or his competence at some point. Chop, speed , gybes, waterstart- everythinkg seems to be a problem suddenly.
My son was happy and doing ok at same time. At the end we decieded to swap a grear and suddenly its appear that everything is as it should be .
Sail easy to control, chop manageable and even gybe possible. Son give up instantly on my rig.



So this same size sail 4.2 but different masts 3.7 and 4.0 made all this tremendous difference. I suspect that sail shape is also better

Sails KA Kaos 4.2 on 400mast - no so good; and Naish Force 4.2 on 370 - OK
I wish to have smaller sails in my collection but as you said ; How often I am going to have 50 knt?

^ Just to be sure I also sail on the Gold Coast and my most commonly used sail is a 7.2. Then there's a jump down to the 5.4 as second most used, then in-between. I'm 80kg.

Sometimes you'll get 30+ SErs, but there's a pretty good chance you'll be at work or a prior engagement you can't get out of.

I can cover 4.7 to 6.2 on my 430.

I need a 460 for the 7.2

One boom for all.

I like having a few different masts for sails, it means that the sail works as designed, no extra drag from the mast poking out the top. Using the huge mast or tip extension ends up wreaking the mast or breaking it at the boom. Using different bits to make up the right mast will involve a compromise in the mast curve and the sails performance. The other thing that i like is i can rig several sails at once and get more sailing done. Your masts last a lot longer too as the work load is shared around

Macroscien said...

So this same size sail 4.2 but different masts 3.7 and 4.0 made all this tremendous difference. I suspect that sail shape is also better

Sails KA Kaos 4.2 on 400mast - no so good; and Naish Force 4.2 on 370 - OK
I wish to have smaller sails in my collection but as you said ; How often I am going to have 50 knt?

Could depend a lot on the bend curve of the two masts. For example, if you happened to be using Naish Firesticks, which some of the specs I have seen would suggest an IMCS bend curve of between 8 and 10% for the 400cm, then that brand/model of mast would probably be too stiff for the Kaos resulting in it being a handful in high winds (KA sails usually set best on a constant curve mast with an IMCS bend curve of around 13-16%).

So what brand/model are the 370 & 400 masts?

Also, have you actually tried the 4.2 Kaos on the 370 mast and the 4.2 Force on the 400 mast? Would be an interesting to hear how the sails handle and perform!

GazMan said...

Macroscien said...

So this same size sail 4.2 but different masts 3.7 and 4.0 made all this tremendous difference. I suspect that sail shape is also better

Sails KA Kaos 4.2 on 400mast - no so good; and Naish Force 4.2 on 370 - OK
I wish to have smaller sails in my collection but as you said ; How often I am going to have 50 knt?

Could depend a lot on the bend curve of the two masts. For example, if you happened to be using Naish Firesticks, which some of the specs I have seen would suggest an IMCS bend curve of between 8 and 10% for the 400cm, then that brand/model of mast would probably be too stiff for the Kaos resulting in it being a handful in high winds (KA sails usually set best on a constant curve mast with an IMCS bend curve of around 13-16%).

So what brand/model are the 370 & 400 masts?

Also, have you actually tried the 4.2 Kaos on the 370 mast and the 4.2 Force on the 400 mast? Would be an interesting to hear how the sails handle and perform!

OK, well,

if you are going to sail in 50 kn wind, there is not much room for mistake, mate

I used recommended by manufacturer length
370 for Naish and 400 for Kaos
( not so sure about recommended carbon content but as the poorest man on the planet ( self acclaimed) I could afford only 30%C)

jsnfok said...

aaahhhhh



should just get a kite

sorry for the blasphemy

i shall watch what i type....

Would agree with that response to some extent, particularly with all the mast/sail compatibility problems experienced by many! Much easier with a kite, no stupid IMCS bend curve ratings to deal with which most manufacturers won't come to the party and place on their products! Not going over to the dark side though, finally got the whole bend curve thing worked out (sort of).