I was looking at a kite yesterday and came up with a question that you folk may be able to answer.

Why aren't struts on the outside of kites, or built into the middle ( a little like split strut)? It would seem more aerodynamic?

I really like this this question. Although I don't know the answer. My first guess would be that it has something to do with the structural integrity of the kite. My second guess is that it's the same situation as boat propellers, in that it took hundreds of years for someone to turn one around and discover they're much more efficient when they're not hampered by prop shaft turbulence. In saying all that, I have continued to fly kites while inverted and although it's like comparing apples with oranges, I don't like them apples.

The foil guys might the the ones to ask as they understand aerodynamics a lot better.
I'm only guessing but I would say due to the same principles as an aircraft wings. Its the drag of the air over the top, larger surface area that drags it up? Its the top of the wind that lifts the plane, not the underneath.

Slingshot is at least one manufacturer who integrates the strut into the canopy. I think maybeFone too.

Quick guess -- struts under the canopyallow the canopy to stay smooth; put them on the back, and it'll billow around the struts a la kite with a rigid frame, like Revolution stunt kites. Integrating them into the canopy surely necessitates stronger seams at the joins, and more work to sew them, so I'd guess weight and cost don't confer a comparable benefit on performance...?

Note the front several inches of struts aren't directly attached to the canopy either...

I was actually marvelling at the wonders of the Slingy Split strut.

Looking at that wondering why the aero dynamic side is the top.

Para gliders may get it.

Another guess.. Air flows faster on outside of wing so wind resistance from top struts would create more drag than bottom struts

Yeah. Dunno.
That's a good question.

I think I now want one of these new kites with the struts on the top.
Game changers!

I like this, very cool to think about. So why even have the bulky struts when some kind of carbon batten could be used? Seems like it would make more sense but I'm not the sharpest tool in the shed by a long shot.

From my understanding you want laminar airflow over the canopy. The air flows faster over the top of the canopy due to the profile of the leading edge creating a low pressure.
The air flowing below the canopy sees the profile at the leading edge and basically ignores everything in between to the trailing edge. There is some turbulence but it is a high pressure zone and not as critical. The air flows in a straight line from the leading edge to the trailing edge.
Double skin helps but the turbulence on the bottom tends to keep the wing flying in a forward direction rather than side slipping. Not so critical on a kite

The strut / leading edge / canopy need to connected in an efficient way to create a nice profile (creating lift/power), but also need to stay as rigid as possible to keep the aerodynamic characteristic given by the designer (profile depth / chord / angle of attack)

I am not saying your idea wouldn't but just pointing at few issues you might run into

- the profile of the canopy is given by the convex shape of the outside of the strut. If you decide to place the strut on the extrados then the inside seam of the strut will give the profile. this seam is usually really hard to stitch and its hard to control the quality of the curve as the curvature of the inside seam is higher than the outside

- then the leading edge needs to be connected to the front of the strut to keep the structure rigid and allow to get the right angle of attack on the struts, which means the leading edge aswell would be on top of the canopy. this is going against aerodynamic principle as the leading edge is the base of making any profile. It defines air entry and curvature of the following profile.

en.wikipedia.org/wiki/NACA_airfoil#/media/File:Airfoil_geometry.svg

- also having outside structure where the airflow needs to be laminar as possible for less drag and more lift wouldn't be a great option.

Other than that, you might be right and the world needs people thinking outside of the box!

Waiting for the pictures :-)

So then what would happen if you set the struts into the canopy like slingshot, but half way through? How would the kite perform?

@bjw,

I know what you mean. Not too sure, I still think the front of the strut has to be underneath the canopy to connect to LE.
The strut/canopy connection could start at the LE like the slingshot (split strut), then around 30% of the chord start to be half way of the section...

When you look at planes, the flap activating mechanism is not on the extrados but on the intrados. they act as a strut, supporting the flaps system mechanism. The pods also act has anti-shock body for better airflow at high speed. We can probably learn from the plane industry ... they have been doing R&D with more budget and longer than the kite industry!

Yes look at aircraft and all the drag crap is underneath.
simple solutions are to use less struts.
but also consider that there is the pump effect where the profile of the canopy redirects air in a laminarish way downwards which results in the opposite force lifting up against your kite lines pulling you harder.

Out of interest @Ben are you the Ikon designer?

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bjw said..
Out of interest @Ben are you the Ikon designer?

Yes.
I used to design kites for Airush from 2005 to 2010, then I started Ikon here in Perth in 2011.