Forums > Stand Up Paddle Foiling

900 Mast a worthy investment?.. Prone experiences?

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Created by Vootleg 31 days ago, 21 Apr 2019
Vootleg
NSW, 3 posts
21 Apr 2019 3:30PM
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Curious to hear experiances riding prone with a 900 mast in particular for DW but also other disciplines? Cheers for the input.

Piros
QLD, 5406 posts
21 Apr 2019 4:33PM
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750 is plenty , extra long mast just become so hard to deal with in the water , turning the board getting back on ect. Plus all the water moving around you just gets so much more leverage . It's a real bitch in DW conditions. Just sucks the energy out of you. Yes it can be better at crossing troughs but you need good skills to ride that high , plus it's a long way down from almost a metre be prepared for extra hard face plants .

Windgenuity
NSW, 250 posts
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23 Apr 2019 1:46PM
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From my experience 90cm is very long. As Piros, mentioned the foil gets so much leverage over you, it can kick your ass very fast without you even knowing what you did wrong. I initially started playing with 90cm for DW, but at high speed it is a handful even with my experience. I spent some time on 85cm which was good, but I am currently riding 80cm and 75cm for DW and Surfing right now. Even at 80cm on a powerful day the foil has some grunt, but the extra 5cm for DW'ing is beneficial in my opinion.

Here's where I think is a good guide as you get better at riding,

- 65cm and Under. Great for general riding. Short enough to not be a hinderance on beach/bar style breaks (I find even 62.5cm to be perfect on a prone board for most breaks ridden, everything longer you will start to touch the bottom while you're waiting for waves). Very responsive and easy(ier) to control.

- 75cm. As you start riding faster and more open water areas. Larger chop, and starting to DW/Ocean Foil. Takes a little while to get used to coming off the shorter masts, but is excellent for pumping and clearing the troughs.

- 75 - 85cm. Downwinding auto pilot. Unless you're in perfectly groomed conditions, going longer than 75cm is a positive for DW'ing. Some of the burst speeds you can hit during cross terrain swell and chop linking requires a little more mast to avoid tank slapping and breeching. But these length masts as above do require more rider skill and ability. An 85cm Mast has some power, and unless you're in control, it will control you! Especially if you're coupling it up with a big wing.

- 85 - 95cm (+). This is very hard to manage in many ways. Top riders are using masts in this range and longer, but it is not easy. I would not recommend it to anyone until they are absolutely needing it after riding in the 75-85cm range (which is unlikely). Kai rides a 110cm mast when he's bombing monsters, and likely uses every cm, but his skills are above mere mortals.

In basics, I find the shorter the mast the more responsive it is, and the easier it is to manipulate and get radical with. The obvious limitation is the breeching and reach above troughs. As you get longer a few things happen. You get a longer stroke for pumping, a larger sweet spot for trim, higher clearance above troughs and gutters, but you also create much larger transitions paths for your pendulum (board and you) as you turn as well as increasing the leverage effect in both directions depending on which force is in control (you or the foil).

Here is a high tech diagram,



You can see that for the same angle (the lesser angle or max angle achievable on a 55cm mast) the distance of travel needed is greater as the mast gets longer assuming you were to fly at a "safe/optimal" wing depth of 25cm. These lengths are the distance over the curve to that same first angle. From this diagram you can see that it is also possible to get greater angles with a longer mast, but again the distance traveled from outer edge to outer edge if far greater with the longer mast.

As the distance get further this means you physically need to move more to achieve "rail to rail" riding, and also need to do it faster (i.e. why it is for more advanced riders).

By all means , try going longer, but I suggest going in small increments.

Hope this helps and makes a little sense,

Ride safe,

JB

blueplanetsurf
195 posts
24 Apr 2019 12:09AM
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I agree with the comments above and want to add that in my experience a longer mast can also make it harder to catch small waves as the foil is deeper in the water on takeoff. Most of the energy of a small wave is close to the surface so if the foil is deep in the water it can get passed over by the wave energy. For me, the sweet spot for surf foiling seems to be in the 70-80 cm range.

Windgenuity
NSW, 250 posts
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24 Apr 2019 10:05AM
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Select to expand quote
blueplanetsurf said..
I agree with the comments above and want to add that in my experience a longer mast can also make it harder to catch small waves as the foil is deeper in the water on takeoff. Most of the energy of a small wave is close to the surface so if the foil is deep in the water it can get passed over by the wave energy. For me, the sweet spot for surf foiling seems to be in the 70-80 cm range.



Yes, I think there equation is something roughly like this image below,


At roughly half the wave length, the swell energy is all but gone.

The Wavelength is very roughly calculated (in open deep water ocean) at Period x Period x 1.15. This is very approx. but helps a little.

Therefore, a 10 Second Swell in 100m of water should have a wave length of 115m, and a decreasing swell energy to approx. 57.5m. I don't think there's an actual formula for the actual amount the energy decreases, but if it was to be simply gradual til it dissipates, For every 1m you will loose approx. 2%.

For a much smaller swell/bumj like a 3sec one, like what we would catch DW'ing, The WL = 10.35, there fore dissipates at roughly 5.2m and there fore decreasing in energy every meter by <20%.

A lot of the time we are actually catching smaller bumps again when DW'ing, and like a 2sec bump would be WL = 4.6, Depth of 2.3m and I would imagine in this instance you would loose 43% every meter (or assumingly <22% every 1/2m).

Makes me want to try a shorter mast again DW'ing

Interesting stuff, totally theory and possibly not 100% accurate, but should be somewhat within the jist of it.

Ride safe,

JB

Piros
QLD, 5406 posts
24 Apr 2019 2:34PM
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Clear as mud but good stuff JB got the cogs churning

Windgenuity
NSW, 250 posts
Site Sponsor
24 Apr 2019 3:24PM
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Piros said..
Clear as mud but good stuff JB got the cogs churning


LOL, yeah. But it definitely got me thinking of more efficiency on light DW days.

Basically when you're trying to get up on a small light day, on an 80cm mast, you could be actually getting 7.5% more swell energy on a 65cm mast. Obviously once you're up and flying, this is all irrelevant, and bigger is better again (up to about 80-85cm), but on those days when you're coming off the foil, and working hard to get back up, a short mast could be your saving grace. Food for thought

JB



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"900 Mast a worthy investment?.. Prone experiences?" started by Vootleg