Measuring Kite Power

Windstoked · Since 21 May 2013 43 Posts Norcal

Anyone know of resources or have experience with measurement of kite power? Having kite power specification data would be very helpful for objective comparison of kites.

registered · Since 12 Jul 2005 1319 Posts tsunami Sandbagger

try to enjoy it and not overthink it.....it may disappoint ...

because it may have the best of one spec does not make it good in overall......compromises.

the foils would be the power houses but they are no good Twisted Evil

Windstoked · Since 21 May 2013 43 Posts Norcal

Point well taken, Registered, however power specs on kites would be helpful when shopping for kites for specific situations, especially light-wind kiting.
Admittedly turning responsiveness is more important for freestyle, and that's how a pro can get bigger air on a 6 than me on a 12 in the same moderate wind conditions. The kite speed that can be achieved by those guys is incredible (it would be interesting to measure that), and power goes up with the square of speed so twice the speed is 4 times the power.

Weaz · Since 23 May 2012 360 Posts Beaverton Obsessed

There are too many variables to just say a kite has x amount of power. As you just said a pro did more on his six meter than you did on your 12. I bet if that pro took your 12 he could boost high also.

Even if you had the two kites tied to a pillar and looped the hell out of them they would pull differently than when the anchor point is moving also. The apparent wind effect should have been covered in the first lesson you took.

Windstoked · Since 21 May 2013 43 Posts Norcal

Apparent speed can easily be measured at the leading edge, Weaz. Combine that with tensiometers at the line attachments and you could get objective kite data even the pros would appreciate. Measure data at various speeds and depower to analyze kite range. Leave the subjective reviews for responsiveness, relaunchability, durability, etc.

beech · Since 21 Aug 2010 485 Posts Longview, WA Obsessed

call the manufacturers. maybe theyll give u a job

MarkWorth · Since 02 May 2011 149 Posts Hood River Stoked

The force in the lines for a particular kite at a particular is speed is impacted by the angle of attack of the kite, the angle of board across the lines, the amount of edge applied, the percentage of pressure on the back foot vs. front foot, the type of board and the weight of the rider.

Kiteboarders that are flying their kite well are rarely sheeted in all the way because that increases the drag in the kite and kills kite speed. Loss of speed = loss of power. Pulling the bar all the way in on a kite that has front lines that are not trimmed, should stop the kite, allowing it to stall while you are riding waves.

Therefore it’s not possible to generate a single force number for a kite that is relevant for kiteboarders.
The force will be dependent of the actions rider and good kite flyers will maintain sufficient kite speed to generate appropriate forces. Up wind ability and the ability to jump are the only issues when the kite it way to small. I often kite up wind on a 4 meter kite during lessons when others are flying 9 and 10 meter kites. When everybody is on 12’s and 14’s I cannot go up wind or hold my ground on the 4 meter, but I can go fast slightly down wind, by keeping the kite speed high and keeping the power stroke deeper in the window.

Learning to fly the kite well only takes a little time and focus and I would encourage anyone who “hates being underpowered” to learn how to do a proper power stroke. The idea is to keep the kite in a narrow vertical column of sky. Keep the top turn forward in the window and the bottom turn back in the window to maintain power in the bottom turn. The turns should be stacked one above the other. The dive is steep because the kite accelerates in a dive. The climb should be at a shallow climb angle to compensate for the slowing of the kite as it climbs and kinetic energy is stored in the kite. At kite speeds near stall speed, a 45 degree angle dive and a 15 degree climb will increase kite speed more than 50 %. As the wind backs off try a 60 degree dive and a 20 degree climb to double air speed of the kite. In the extreme case, a vertical dive with an 85 degree climb with an adjustment of the climb angle to 60 degrees in the last third of the climb, will allow you to triple kite speed. This will generally pull you down wind because of the apparent wind shift at low wind speeds and high board speeds.

Most kites provide plenty of power and good kiteboarders are not using the maximum power until they go for big air or the wind drops two kite sizes

registered · Since 12 Jul 2005 1319 Posts tsunami Sandbagger

better go play in a wind tunnel with fixed attachment with fixed line length,same bar length ect. Each kite has slight different angles ect ..... I think that kiting has not needed this kind of scrutiny in regards to power. Maybe when the bay racing hits the big money and steez MAYBE someone else will jump on your wagon...... but for most its a luxury of a sport with no need for over thinking .

You need to PM bulae 99 he could help you I think with the heady end.

Windian · Since 28 Apr 2008 899 Posts Newport, OR NEWPORT OG

You are getting too technical. The best system is simply the size rating of the kites. A 12m kite from one company is comparable in power to a 12m from another company, it is that simple. Most of the companies also have the windspeed range that they claim the kite is designed for when kiteboarding. Go to the company websites and do some looking.

Confused

MarkWorth · Since 02 May 2011 149 Posts Hood River Stoked

Nope.
The wind tunnel will not give you valuable info except perhaps for a parked kite.

The power of the kite in low wind is dependent on carrying the momentum of the dive through the bottom turn, which is dependent on the weight distribution of the wing relative to the center of the kite and pivot point in the turn as well as how much of the wing needs to stall to create the kite rotation.

BigR · Since 05 Jul 2005 372 Posts White Salmon Obsessed

So, do you want to measure minimum power which is what you measure in a wind tunnel , or maximum power, which is what you measure when you turn the kite violently?

Or, average power when you maybe sine the kite sometimes slowly?

maybe you could install a contraption between your chicken loop and harness to find out what the forces are and make a chart of force of different kites in constant wind in different kitesurfing activities. Cruising, jumping , turning etc.......

registered · Since 12 Jul 2005 1319 Posts tsunami Sandbagger

It would almost need to be digital meter on chicken line to remember high/ low reading so you could focus on flying in some constant way .

I thought wind tunnel for a constant. Otherwise constant real world variability would jeopardize true comparisons from wind , kites , current , aspects , edging, ect.
So you would need to strip down as many variables as possible to focus on accuracy for the power readings with kite set at different orientations across different kites ect in a tunnel or not.

You could never replicated the power of real world sine'in with the tons of other variables related to the actions in a wind tunnel obviously or not.

Nak · Mon May 27, 13 4:45 pm

Are you really interested in power, or do you really mean force? (Lift.) Power is going to be rather difficult to measure, force could be measured with a force gauge relatively easily. The problem is, would the measurement provide useful data? Even if you measured the force from a parked kite, you'd need to know the airspeed at the kite for it to mean anything. For instance, let's say you measure the parked force of a kite at a measured 20mph wind speed at the beach. Then you measure the force produced by a different kite at the same 20mph on the beach. No comparison is possible, because you have no idea what the wind speed was at the kite. So, to have any meaning, you'd need to be able to measure the IAS (indicated airspeed) at the kite. You'd have to measure force while sining and time to sine the kite as well. Next, you'd need to add rider speed, etc, etc. It is certainly possible, but so difficult to do that it wouldn't be worth it. A more realistic goal might be to measure minimum force the kite generates when the kite is fully de-powered, and also with the safety deployed. That would be far easier to measure and would provide useful information. Max power or force is best measured subjectively, considering the myriad of variables involved.

cosmodog · Since 06 Oct 2005 203 Posts Stoked

You could sine a kite in this tunnel at Nasa Ames in Mt View. Might be a tad expensive...

cosmodog · Since 06 Oct 2005 203 Posts Stoked

Here's how I would do it on the cheap:
- get 3 digital force gages for center and outside lines.
- fly a second kite next to the test kite with a wind meter attached to get wind speed.
- measure force at full power/depower and a bunch of spots between
- use cameras to measure L/D ratio (deduce from kite angle)
- now the tricky part - while moving the kite measure bar angle and kite speed and turning speed using cameras.

I think you could get some really interesting info from all this.

kitezilla · Since 22 Jun 2006 453 Posts gorge Obsessed

You just need to pit your kite against something with a know horsepower, like a "tug-o-war". See which one wins... get 'em both stalled out, and there is your answer.

On dry land you would need a team of horses... if the team starts to win. then, cut one horse loose, at a time, until you have just the right number of horses, and they stop moving forward.

On the water, you need a 17 foot boat with 3 outboard motors on the transom... 3 HP, 5HP and 7&1/2 HP....same deal as with the horses... but you don't need a vet standing by.

Weaz · Since 23 May 2012 360 Posts Beaverton Obsessed

The main thing is the amount of variables involved it would be better to develop a mathematical simulation based on the shape of the kites. Just some of the variables would be:
Aspect ratio
LE shape
Depth of trailing edge
Canopy shape (lift from the wing)
Surface area hitting the canopy (drag)
Speed of wind
Speed of kite
Current water speed
Water direction
Rider speed
Rider angle relative to kite
Rider angle relative to current
Rider angle relative to wind
Rider weight
Kite weight
Line length
Line elasticity
Turning speed

The main things to look at are the shape, flat area, chord, aspect ratio, projected area, projected aspect ratio.

Honestly find a kite designer who is willing to shed some light.