With the slightly different mast curves, sail types and personal preferences, who here uses a mix of 370/400 on sizes around 4.5-5.0 (resp .400/430 on 5.x) and what do you look for when doing so?

I do that with my Ezzy 4.5, as its the recommended mast. I used 400 to start with, but it felt a little stiff. The 370 bottom does soften it up a little. Its not a massive difference, but noticeable, easier to use in stronger winds.

In a Gaastra Manic 2014 4.5 (recommended mast: 370 hardtop)
I use a Naish Firestick (pre 2011 hardtop ) 400 base with an (leftover) Gaastra (pre 2016 hardtop) 370 top : 387 cm
Only needs an 4cm. extension instead of 22.5cm with the 370 mast.

3 reasons:
1. When 4.5 rigged with the 400 base/leftover 370 top, the Gaastra 370 (a complete base + top) can simultaneously be used for the 4.0
2. Spare mast in case of broken complete 370
3. I imagine/think it has a tit more power because of the stiffer 400 base when it's light (low end).
reality: I'm not skilled enough to feel a difference

Thanks Phil and thanks for the details Ice.

Phil, do you remember if it changed anything such as rigging cues, harness lines position and such?

Ice, I rigged a shorter top but never tried on the water. It looked quite flex top, no?

The 4.7 I have needs 407 flex top.
Today, I tried a 370 base with a 400 top and 22cm extension. The planing was vastly improved, like shocking. The sweet spot moved forward slightly. The pumping excellent and responsive.

Yet, I felt like the sail moved a bit (maybe lacking a touch of down haul?) and still felt a touch top heavy.

For tomorrow I'm going to try with a mast tip extension which seems to increase the flex top moving the curve a bit farther down the sail.

Bonus point is that I'm saving weight on mast half and bottom extension (using a short one). My mast tip extension is very light.

Will update after tomorrow.

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Manuel7 said..

Phil, do you remember if it changed anything such as rigging cues, harness lines position and such?

No, it was 5 1/2 years ago. I had the sail for nearly 2 years (16 sessions) before buying the 370 bottom section. So it wasnt as though the sail on the 400 was dreadful or anything like that. But it felt better with the 370.

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PhilUK said..

Manuel7 said..

Phil, do you remember if it changed anything such as rigging cues, harness lines position and such?

No, it was 5 1/2 years ago. I had the sail for nearly 2 years (16 sessions) before buying the 370 bottom section. So it wasnt as though the sail on the 400 was dreadful or anything like that. But it felt better with the 370.

Thank you. It makes sense and is what I heard from other Ezzy users as well (that the 4.5 works better with 370/400 than 400).

Please do CORRECT anything that may not seem right below!

I experimented and learned something about FlexTop masts. They are actually more flex both up top and down low.
This explains why when using a constant curve mast in a flextop sail we have less looseness up top and less pocket down low from the lack of bend in both places for the same tension. We usually use less outhaul as a result.

Using a shorter base softens and brings down the bend. creating some looseness up top while retaining a good pocket below.

Adding a mast tip extension increases leverage against the mast making it more bendy for the same tension and therefore even more flextop. Using less mast base extension also makes it more flextop. Therefore the combination of both the mast tip, a shorter base and less base extension will render a CC mast more flextop.

Using a shorter top will loosen the sail up top but move the bend higher up at the same time with a stiffer bottom and flatter pocket. So it'll feel softer but with not much grunt and pumping.

Here is a video where I'm trying different mast types and lengths:



Using a size up longer top and an even shorter bottom {i.e. 400 top and 340 bottom in a 370 sail) will turn it into a... hard top! I tried a 370 hard top (Naish) mast and a340+400 Ezzy, on a hardtop sail, and got the exact same result.

Finally, using more mast base extension will stiffen up a mast (moving the bend up)

I hope it makes some sense. Results will vary depending on sails, masts and sizes, for sure.
In the video above I was shocked to actually hear me say the sail looks the same rigged but completely different on the water! That summarizes our sport pretty darn well, hahaha !

Yes, I do that with a mix of 340/370/400m Caas masts and Severne S1 sails. I find that anything around 15cm extension feels best. So 370 base with 400 top in 4.8, then full 370 in 4.4, 340 base and 370 top in 4.0, and full 340 in 3.6. Works nicely and increases the amount of backup options when you break a mast. I find the shorter base with longer top works best in the mixed sizes, likely due to the mast bend curve relative to the sail shape.

Thanks for the additional feedback.

Today I tried with the tip extension and wasn't convinced fully. Had a bad session for one. It rigged well but still I think the sail doesn't bleed wind.

If I pull anymore downhaul then it won't breathe properly and becomes twitchy and dead. Also it already lacked lift anyway.

Tomorrow we should have a nice session let's see.

Had another session, light this time. Tried a touch less downhaul and more outhaul. Wasn't convinced either.

When I pull to the dot, the batten above the boom just about clears the mast, doesn't leave much breathing room.

Confirmation going from a short bottom to the matching length one that the sweet spot moves backward when using regular mast.

So short bottom sweet spot is farther forward and regular bottom sweet spot is farther back.

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On the 4.7 using a mast tip extension + short bottom, I have the bottom batten about 1/2 way across the mast while the batten over the boom is about 1/3 across when downhauling to the dot.

Another finding is that the power comes from higher up when using a shorter bottom.