Low end mid length boards

Hi,
I finally got one of these mid length / dw style boards, 5.10 x 22 , 90l. I got this board in addition to my 60l wing board for light winds.
Don't get me wrong, I really like how the carves, jibes and pumps. Almost no regret compared to my small board. Amazing performance board. I tried a normal 90l board and didn't liked it. So definitely in the larger volume sizes, these are the only type of boards I can think of riding.

However, I don't see the super low wind capability, every body is talking about. In 10 to 14kn range all good, the 5.10 allows me to use a foil, one sice smaller compared to my 60l. But below 10 kn...

I am 73kg, with my 60l board , I can go as low as 8kn with an 8m wing and art pro 1201. The 5.10 goes in 8kn as well, but only with an 8m wing, just a little less effort. From all what I have read, I was expecting to be in 8kn on a 6.5m wing. Below 8kn I am struggling. I can only get going with a massive foil, png 1310. again, I was expecting to be on an 8m wing without much of an issue.

So, where is this super low end wind rang? I am very much used to wing with small equipment in low winds.
Still, is it me, or is the board too short / too wide? Shape? The rails are very rounded.

Please, any advice?

Low wind isn't just an equipment decision, it's a legitimate skillset that you have to work on.

I'm 87kg and if the average wind speed is 10 knots or above I ride:
85l Sunova Carver 5'10"x20"
Ocean Rodeo 4mAA
Cloud IX fs1150 with catalyst

There's a lot that goes into feeling the wind, catching gusts, using swell and currents to assist. You will also find that the midlength boards take off at a little more of a downwind angle. Different foils and wings have better low end characteristics. The ability to pump the wing and board is critical.

So, you have the tools and now you just have to develop the skills.

A few weeks ago:
www.instagram.com/reel/C6jPMb9rPVy/?utm_source=ig_web_button_share_sheet&igsh=MzRlODBiNWFlZA==

As said, big skill factor here. Also fitness, it will take more pumping to go with a smaller wing. But it will be much nicer once up. For me, the biggest thing in light winds with the midlength boards vs an older short and fat shape, is that I can maintain speed between bumps or gusts, allowing me to get to take off speed over multiple bumps or gusts, rather than absolutely having to make it in one with the old style board.

Also, length to beam ratio really really matters for these designs especially in light wind. Tail shape, rail shape, and rocker profile also matter, but l to b dominates. 22in is definitely the high end of the width range but isn't high per se. 5'10 isn't short but it is moving toward the shorter end of a midlength style wingboard. End result though is your length to beam ratio isn't all that great as far as this style of design goes, and you have to compensate with more power.

And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Select to expand quote

BWalnut said..
Low wind isn't just an equipment decision, it's a legitimate skillset that you have to work on.

I'm 87kg and if the average wind speed is 10 knots or above I ride:
85l Sunova Carver 5'10"x20"
Ocean Rodeo 4mAA
Cloud IX fs1150 with catalyst

There's a lot that goes into feeling the wind, catching gusts, using swell and currents to assist. You will also find that the midlength boards take off at a little more of a downwind angle. Different foils and wings have better low end characteristics. The ability to pump the wing and board is critical.

So, you have the tools and now you just have to develop the skills.

A few weeks ago:
www.instagram.com/reel/C6jPMb9rPVy/?utm_source=ig_web_button_share_sheet&igsh=MzRlODBiNWFlZA==

Looks like a nice setup. Do you have any on-water riding video footage in those conditions?

i'd say it's your width like someone said. 22 is a monster width in todays comparison.

Select to expand quote

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

Well and also your cold air in the gorge is more dense so a 14kn applies more force to the wing than desert winds in 100F

Select to expand quote

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

More to the cube than to the wind speed square..
Good reference here: solidwize.com/wp-content/uploads/2013/07/7-Understanding-the-Wind-Power-Equation.pdf

Select to expand quote

SlowlyButSurely said..

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

More to the cube than to the wind speed square..
Good reference here: solidwize.com/wp-content/uploads/2013/07/7-Understanding-the-Wind-Power-Equation.pdf

I'm about to post this.

Wind power increase to the CUBE of wind speed.

And drag force in increase by the SQUARE of water speed over foil (like airspeed for plane). And the power needed to overcome drag is the CUBE of the water speed.

In low power condition. Large but efficient foil (like thin HA foil on the larger size) will help a lot. You need less power to sustain the slower foil.

Select to expand quote

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

If you just want to look at an equation, here's one for velocity pressure head. This is conservation of energy, simplified down to just potential and kinetic energy (no heat, work, or chemical changes).
www.engineeringtoolbox.com/velocity-head-d_916.html

If you want to get much further into the weeds, start here and then go through to the derivation of Bernoulli (section 3). This is a more complete form of conservation of energy as applied to a fluid flow.
engineeringlibrary.org/reference/continuity-equation-fluid-flow-doe-handbook#:~:text=The%20continuity%20equation%20is%20simply,the%20mass%20flow%20rate%20out.

However, I can't find anywhere an explanation or derivation of why kinetic energy is proportional to velocity squared. This is a fascinating blind spot, thanks for illuminating it - it was just something I was taught in 1st year and not thought about since. I don't know if it is my Google-fu coming up short or if this is an empirical relation that was determined by experiments rather than a theoretical result.

Select to expand quote

Gencion said..

P.P.S. 6'8 is optimal length which will fit into my car. 7' I can squeeze with some effort. So I am not able to go longer. And for safety reasons I prefer to keep equipment inside the car.

I get and share the issue of in the car vs on the car. However, a pretty middle of the road DW board is something like 8'6 by 20 at the moment. That is a L:B ratio of 5.1. Your 6'8x22 is at 3.63. 22 inches is, for the 3rd time this thread, not at all a narrow board for the design style being discussed. You are looking for extreme efficiency from a board that is miles away from an extremely efficient length to beam shape. If you are stuck at 6'8 long either learn to ride a ~17in wide board to keep the L:B in the required efficiency range, or accept you have to compensate elsewhere (big foil, big wing, big pumping skills, etc).

Select to expand quote

Mark _australia said..

Well and also your cold air in the gorge is more dense so a 14kn applies more force to the wing than desert winds in 100F

Air density does drop about 10% going from 50 to 100F. Not at all insignificant, but compensated by less than half a knot of extra wind speed at 8kn. It becomes a bigger deal in the ~20kn range and up, where it start to be 1 or even 2knots extra wind to compensate the density difference.

Select to expand quote

SlowlyButSurely said..

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

More to the cube than to the wind speed square..
Good reference here: solidwize.com/wp-content/uploads/2013/07/7-Understanding-the-Wind-Power-Equation.pdf

Select to expand quote

Taeyeony said..

Wind power increase to the CUBE of wind speed.

And drag force in increase by the SQUARE of water speed over foil (like airspeed for plane). And the power needed to overcome drag is the CUBE of the water speed.

In low power condition. Large but efficient foil (like thin HA foil on the larger size) will help a lot. You need less power to sustain the slower foil.

Yes, power scales with velocity cubed in fluid flows and power is indeed the more relevant parameter for the matter being discussed. However, I have found repeatedly that in a fluid dynamics context, power is much less accessible both conceptually and mathematically as I've not come across an explanation that works without understanding control volume analysis. That is why I chose to discuss energy, as my main point was that what is available to extract from the wind for propulsion is not linear, and a 1kn change in wind speed at the low end is very significant.

Definitely agree a big, but efficient, foil is a good way to gain efficiency without resorting to very extreme board dimensions.

Select to expand quote

Wingfoil Rentals said..
Mines an 87ltr custom,
gets up with ha780 in 6 knots with some effort 8knots effortlessly
the hull is a true planing windsurf hull. Not much else to write

Yep, putting down the power to get over the resistance hump and onto plane with an appropriate board design is by no means irrelevant. When board length is limited for some reason, limiting possible length to beam ratio, it may even become the optimal approach. I would expect this to be very rider weight dependent though, the efficiency of a planing hull shape and the size of the resistance hump is very dependent on loading - it must be kept fairly low. For a heavy rider, this means a larger wetted surface area and thus a larger low speed drag penalty than a light rider. Would love to know your weight; the board, foil, and wind speeds you posted suggest lighter.

Foil size also matters a lot - the smaller the foil, the higher the speed required for it to engage and start generating a significant chunk of lift. Long narrow boards have their resistance advantages primarily at lower speeds, while planing boards are usually more efficient at higher speeds.

Select to expand quote

Svendson said..

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

If you just want to look at an equation, here's one for velocity pressure head. This is conservation of energy, simplified down to just potential and kinetic energy (no heat, work, or chemical changes).
www.engineeringtoolbox.com/velocity-head-d_916.html

If you want to get much further into the weeds, start here and then go through to the derivation of Bernoulli (section 3). This is a more complete form of conservation of energy as applied to a fluid flow.
engineeringlibrary.org/reference/continuity-equation-fluid-flow-doe-handbook#:~:text=The%20continuity%20equation%20is%20simply,the%20mass%20flow%20rate%20out.

However, I can't find anywhere an explanation or derivation of why kinetic energy is proportional to velocity squared. This is a fascinating blind spot, thanks for illuminating it - it was just something I was taught in 1st year and not thought about since. I don't know if it is my Google-fu coming up short or if this is an empirical relation that was determined by experiments rather than a theoretical result.

Gencion said..

P.P.S. 6'8 is optimal length which will fit into my car. 7' I can squeeze with some effort. So I am not able to go longer. And for safety reasons I prefer to keep equipment inside the car.

I get and share the issue of in the car vs on the car. However, a pretty middle of the road DW board is something like 8'6 by 20 at the moment. That is a L:B ratio of 5.1. Your 6'8x22 is at 3.63. 22 inches is, for the 3rd time this thread, not at all a narrow board for the design style being discussed. You are looking for extreme efficiency from a board that is miles away from an extremely efficient length to beam shape. If you are stuck at 6'8 long either learn to ride a ~17in wide board to keep the L:B in the required efficiency range, or accept you have to compensate elsewhere (big foil, big wing, big pumping skills, etc).

Mark _australia said..

Well and also your cold air in the gorge is more dense so a 14kn applies more force to the wing than desert winds in 100F

Air density does drop about 10% going from 50 to 100F. Not at all insignificant, but compensated by less than half a knot of extra wind speed at 8kn. It becomes a bigger deal in the ~20kn range and up, where it start to be 1 or even 2knots extra wind to compensate the density difference.

SlowlyButSurely said..

BWalnut said..

Svendson said..
And lastly, remember wind energy scales with wind speed squared. Going from 10kn to 8kn is a ~40% drop in available energy, you need to move into the realm of extreme efficiency at this level so as said a proper dw board is with its very high length to beam ratio is a good solution.

Do you have links to any literature about this? I'd like to further educate myself.

More to the cube than to the wind speed square..
Good reference here: solidwize.com/wp-content/uploads/2013/07/7-Understanding-the-Wind-Power-Equation.pdf

Taeyeony said..

Wind power increase to the CUBE of wind speed.

And drag force in increase by the SQUARE of water speed over foil (like airspeed for plane). And the power needed to overcome drag is the CUBE of the water speed.

In low power condition. Large but efficient foil (like thin HA foil on the larger size) will help a lot. You need less power to sustain the slower foil.

Yes, power scales with velocity cubed in fluid flows and power is indeed the more relevant parameter for the matter being discussed. However, I have found repeatedly that in a fluid dynamics context, power is much less accessible both conceptually and mathematically as I've not come across an explanation that works without understanding control volume analysis. That is why I chose to discuss energy, as my main point was that what is available to extract from the wind for propulsion is not linear, and a 1kn change in wind speed at the low end is very significant.

Definitely agree a big, but efficient, foil is a good way to gain efficiency without resorting to very extreme board dimensions.

Wingfoil Rentals said..
Mines an 87ltr custom,
gets up with ha780 in 6 knots with some effort 8knots effortlessly
the hull is a true planing windsurf hull. Not much else to write

Yep, putting down the power to get over the resistance hump and onto plane with an appropriate board design is by no means irrelevant. When board length is limited for some reason, limiting possible length to beam ratio, it may even become the optimal approach. I would expect this to be very rider weight dependent though, the efficiency of a planing hull shape and the size of the resistance hump is very dependent on loading - it must be kept fairly low. For a heavy rider, this means a larger wetted surface area and thus a larger low speed drag penalty than a light rider. Would love to know your weight; the board, foil, and wind speeds you posted suggest lighter.

Foil size also matters a lot - the smaller the foil, the higher the speed required for it to engage and start generating a significant chunk of lift. Long narrow boards have their resistance advantages primarily at lower speeds, while planing boards are usually more efficient at higher speeds.

There's a lot for me to unpack and learn here, I'm going to dive in and try to grasp a better understanding of all of this. Straight away though, thanks for taking the time to write this out and I'm sure I'll be asking more questions!

Select to expand quote

DWF said..
I'm seeing some similar trends to windsurfer light wind skills. Those who own giant sails, never develop the light air skill set of those who refuse to go big.

22 inches wide in a 5'10, is not going to be magic. Should be 20 wide max, and probably 19 wide for your light weight.

I think this is a critical element that most people struggle to get past. They buy a big sail at the start of their journey and then it hinders their lightwind development, possibly forever.

I guess I was fortunate in a way that coming from kiting, I despised the wing from day one. As such, I refused to buy something bigger than a 4.5m when I started and have desperately sought to never ride larger than a 3.5m since. I've eased on this a bit with some of the ultralight fabrics making my current 4m fun to ride, but still aim for 3m every day. As such, I've started to come to terms with the fact that 250+ days of trying to use a smaller wing has seriously altered my ability to recommend sail size for anyone any longer.

Select to expand quote

SpokeyDoke said..

BWalnut said..

I guess I was fortunate in a way that coming from kiting, I despised the wing from day one. As such, I refused to buy something bigger than a 4.5m when I started and have desperately sought to never ride larger than a 3.5m since. I've eased on this a bit with some of the ultralight fabrics making my current 4m fun to ride, but still aim for 3m every day. As such, I've started to come to terms with the fact that 250+ days of trying to use a smaller wing has seriously altered my ability to recommend sail size for anyone any longer.

You are also fortunate to be in the Gorge, which is a total outlier in terms of conditions.

You know, the biggest difference that I came to realize about the gorge vs other locations is the stability of the water. Everything is moving in a very linear setup for current and swell. There's not 3-4-5 different swells plus wind chop all moving at different angles. As such, my perspective on narrow board stability is drastically different than ocean riders. I can paddle an 18" board in the gorge no problem. Paddling a 21" board out past the break in the ocean was painfully eye opening.

Going narrow is not that hard. For me, it it easier than going from long to short board with similar volume. I think 2-3 sessions in extreme chops and you will get used to it.

But for me. I will not buy anything less than 18" the reason is the foot placement not the stability.

Doe it make sense to change from 6'8x22" to 7'2x20"?
Or the difference would be too small?

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eppo said..
be interesting what we are discussing width wise in another years time !

Absolutely.
Go back only two and a half years and everybody was about going shorter and shorter. That's when the AK Compact and Naish Compact were new and all the craze.
I still have my wife's 115 Naish Compact which is quite fun in super light wind as with a little pumping it takes off quite well and below that threshold is pure joy for mucking around and trying all the wing manipulation I'll never learn to accomplish in serious wind.
It's almost exactly two years ago that I saw Chris McDonald's father paddling up on one one of the first Cruzaders out there and people started wondering whether those things would ever play a significant role in super lightwind winging.
Remember when race bike tires were 19mm wide and glued to the rims, windsurfers were held back from boards wider than 100cm only by race regulations after there had been a hype about no nose boards and before everybody needed a stubby board? Countless iterations of the theme of going to the extreme and swinging back to a reasonable compromise suggest we're right in the phase of experiments in a comparatively new sport.
My humble guess would be that after a while a few freaks will be out thre on 18" narrow torpedoes with most people settling at something between 20 and 22 and a length of not more than 8 feet as a compromise.
Is it only me or do others also hesitate to go back and strap a cumbersome treetrunk to the roof of their van after years of chucking everything in its back?

@Beached, yeah a thinner board is a great feel, but how much you feel the foil is also a matter of construction. An really stiff board like an Appletree feels imo more direct and has a better foil feel as an "softer" glassed EPS board.I think the max width at some point will be rider size dependent. With EU shoe size 47/ US13 I need simply more room to fit on as a lot smaller rider with way smaller feet. On my KT5.4x22x56l there is a little bit of room to wiggle around but not that much so I don,t see me going under lets say 20 by a lot.

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Gencion said..
Doe it make sense to change from 6'8x22" to 7'2x20"?
Or the difference would be too small?

6'8"= 3.6 AR

7'2"= 4.3 AR

Huge change IMO.