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400cm mast with 45cm extension - good idea or not?

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Created by BenAS Two weeks ago, 20 Nov 2019
BenAS
7 posts
20 Nov 2019 9:22AM
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newbie question - sorry, I have searched but not really found an answer

I have a 6.0 Gastra Hybrid with a 445cm Luff and need a mast for it. I have been told that I could run a 400cm mast with a 48cm extension, but I'm just not sure if this is a good idea. The reason I'm asking is I'd also like to buy a smaller (5.3-5.5) sail as expect I'd need a 400cm mast for that.

I have been borrowing a 430 mast, but I need to give it back. Should I look at a 400cm mast, or go for 430 and then find smaller sail (5.3-5.3) that can rig with a 430cm mast?

thoughts?

olskool
QLD, 1579 posts
20 Nov 2019 11:54AM
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Ive run a few big sails (9.5 n 9.8) using 48cm extension, when ive not had correct mast. Didnt seem to make too much difference to sail set. Havnt broken anything bcoz of it either. If youre a race bandit you may notice the difference, but for just cruisin around it works ok.

racerX
NSW, 373 posts
21 Nov 2019 2:14AM
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400 rdm forms the core of my wave sail kit. My wave sails are 4.2,4.7 and 5.3, which I use 400 and a 370 but I can get by with just 400. For bigger masts I use SDM so 430 for 6.2 and 7 then 460 for 7.8 which are all slalom, but could just as well be freeridey sails.


So a 400 rdm and 430 SDM can make a good combination.

48 extension is fine for a SDM NOT used for wave sailing. But if you miles from the correct mast you might find the sail not as stable than if you had a stiffer mast.

Longer masts are stiffer.


forceten
834 posts
21 Nov 2019 12:24AM
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The use of the 400 with that extension, would give it approximately the stiffness of a 430.
the initial post, says you don't have either a 400 nor 430 .

people use long ext all the time, they don't break till they do. The mast whichever should compliment the sail in regard to mast bend curve, older Gaastra took a hard top.

additional option Is to buy a mast extension common called an extendo, that goes into the bottom to make it longer, making the 400 a 430, the regular EXT fits into this, but only goes in so far.

Consideration would be the future sail should be the correct mast bend curve.

Basher
137 posts
24 Nov 2019 1:19AM
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I would never use a 4m mast with anywhere near 40cms of extension.
If the mast is an RDM then any extension over 32cms would not be safe in waves, strength wise.

But the main reason I wouldn't use a long extension is that you end up fitting the boom to the wrong part of the mast - and probably too close to the extension. The mast bend would also be affected.

A sail with a 445 luff length clearly needs a 430 mast as a starting point.

forceten
834 posts
24 Nov 2019 11:39PM
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Select to expand quote
Basher said..
I would never use a 4m mast with anywhere near 40cms of extension.
If the mast is an RDM then any extension over 32cms would not be safe in waves, strength wise.

But the main reason I wouldn't use a long extension is that you end up fitting the boom to the wrong part of the mast - and probably too close to the extension. The mast bend would also be affected.

A sail with a 445 luff length clearly needs a 430 mast as a starting point.


Agree with most. The boom fitting area " may " be effected, it's normally visible cause it's reinforced.
the mast bend yes is effected, making it more like a 430, this case, and that's what it wants anyway.

In bold letters, I would not use a long extension in waves, and prob not at all.
courses for horses.

Basher
137 posts
25 Nov 2019 1:58AM
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The bend thing is perhaps interesting.
If you make a 4m mast 30cms longer then in theory you get the right IMCS stiffness as for a 430 mast.
But the bend curve will not be the same for three reasons.

Firstly if your 4m mast was a soft top then it would be relatively less-so at 430.
Secondly, most extensions have a little play in them, so that they don't jam in the mast, and that tolerance allows extra effective bend at the mast base, with the extension base/tack pulleys sitting further aft.
With a fully inserted extension which is more a 'snug fit' then you may find the opposite is true, with get extra stiffness created in the mast bottom section due to the doubling up of the tubing.

But the answer, as ever, is to use the correct mast length and recommended extension in the first place. And there ARE other 6m rigs that will fit on 4m masts - with just a 30 cms extension required.

On topic, has anyone here actually ever run a 4m mast with 48cms extension?

mathew
VIC, 1779 posts
25 Nov 2019 3:48PM
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^^ did people read the question?.... "newbie question".... what is this "going out in the waves" stuff ?

Short answer - yes it is possible. You are a newbie, so you are likely just uphauling and sailing on flat'ish water. Try not to be too abusive the gear.

The single most important reason to not use a long extension -> the location where the boom fits the mast, has extra reinforcement so that it can handle more stress. Using a long extension results in the boom-connection being outside of that reinforced region.

The real answer is that it depends on lots of factors, so it could go either way - with a preference to "no", all things being equal.

If you are learning to uphaul and going out in wind up to 10kn, then "yes". If you are a light-weight (say < 70kg) and going out in wind up to < 20kn with somewhat flat water, then "probably yes". If you have more money than God, then "no... and go buy 3 masts", and so on.

When you say "newbie" - what kind of skills do you have and what are you looking to achieve this season?

mathew
VIC, 1779 posts
25 Nov 2019 3:55PM
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Select to expand quote
Basher said..
On topic, has anyone here actually ever run a 4m mast with 48cms extension?


not 48... yes to 44cm (before I lost that extension). Only when sailing flat-water in light-medium wind strength, and I was quite careful to not over-stress the boom-clamp.

NotWal
QLD, 7129 posts
25 Nov 2019 3:45PM
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430s are stiffer than 400s. Extending a 400 doesn't make it stiffer like a 430.
One of the tricks practiced by lightweights (like myself) is to use short masts on max extension in order to enjoy a little more gust friendly behaviour.

Grantmac
80 posts
26 Nov 2019 1:05AM
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Is he talking about an RDM or SDM (unclear), because I highly doubt an RDM would care where you clamp the boom.

mark62
329 posts
26 Nov 2019 1:44AM
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benAS, have a look on the GA website, depending on which year Hybrid you have, 5m, 5.6m and 6m can set on 400 and 430 rpm and sdm. Basically the6 list ideal mast and alternative mast. Pick the ideal mast for your most used sail size, the alternative mast size will be fine for those rarer days. At some point, you will buy 400, 430 and 460 masts, we all eventually get addicted to buying new gear, even stuff we don't need!!!

leto
45 posts
26 Nov 2019 2:23AM
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Been using 45-46cm extension for years on some sails and here is my take on it that may be helpful for you. Afte15 years of windsurfing I feel all of us find what works for them and there is no wrong or right once you reach a certain level.

I never heard of 48cm RDM extension. You can drill a few holes but max I saw is 46 RDM. I have 3 masts: 400, 370, 310. All Nolimitz. (strange combo I know). I use my Naish Boxer 6.2 and HotSails KS3 5.8 on 400cm and all rest Naish Choppers on 370. Chopper M and S I sometimes set on 310cm mast to add softness. I'm not planning to buy 430cm mast ever nor buy a sail larger than 6m. Nor I will buy a sail that needs > 400cm + 46cm extension. If my 6.2 sail breaks, I don't care to replace it.. will foil..

My typical long extension usage:
----
Boxer 6.2: 400 + 46cm
KS3 5.8: 400 + 38cm
Chopper M: 310 + 42cm

I never had any problems. I sometimes sail in the ocean too. I jump a lot. Agree with people that if your sail gets trashed in waves good and in wrong position under water, it may break easier with very long extension. Also I feel that other factors are at play here or at least for me:

1. My level of windsurfing is pretty good.
2. I'm tall.
3. Fairly light weight and light on my feet.
4. I don't race (meaning I prefer to be a touch under powered than massively overpowered)

I also agree with a person who said that for RDMs higher boom attachment point probably not as critical. Again, all my experience.



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"400cm mast with 45cm extension - good idea or not?" started by BenAS