monkeykites / no center strut

[flip]

i haven't heard much about monkeykites (they seem to be more popular overseas) but recently discovered that their designer, saul griffith, works at squid labs, which until recently was two blocks away from where i work in emeryville.

a trademark of saul's designs is no center strut, like what north has decided to do for the 07 rhino. there's a really nice explanation of his quoted at this norwegian forum (third post down - just look for the english) in which he leads up to and describes why it's desirable to have no center strut. i follow it, right up to the point where he actually explains why it's better to have a higher distribution of ribs on the ends than in the center:

"This means that there is less air-pressure sucking the canopy into shape in the tips. That is why it is advantageous to put more of your ribs closer to the tips and closer spaced at the tips. So that is why we choose to have no central strut. By removing the centre strut, we can have more struts at the tips where they count more."

if the purpose of the ribs is to establish a preferred airfoil cross-section and prevent the canopy from getting sucked up away from that cross section by the low pressure above the kite as much as possible, then i would think that you'd want more ribs in the center, where the sucking was the strongest and thus the canopy will be distorted the most by it. perhaps he is talking about very low angles of attack (highly depowered), where the tips would have little, if any, lift, and the struts would be keeping their canopy from flapping the other way - downward/inward - rather than preventing it from being distorted upward/outward.

at any rate, it will be interesting to see what people find its effect to be on the rhino. the strut placement did strangely appeal to me when i first saw it.

[OliverG]

The 2005 RRD Type Wave kites have no center strut and it's worked very well for them.

We see Saul testing some protos and new designs every once in a while in the East Bay...

[adamrod]

basically what he's saying is:

the middle of the kite produces more lift than the tips, this lift causes the kite to stretch in to a C shape. Since the tips have less lift, there is less constraining them into the correct shape. So, since the middle has lift to keep it in the right shape, it doesn't need a strut. since the tips don't have lift, they need a strut to keep the right shape.

also, since the tips are a shorter airfoil, the round leading edge drag is greater, causing the tips to stall more frequently, which means that they would get all messed up without struts. make sense?

[elli]

You know how it goes. Try the kite, and if you like it, it makes sense. If you don't then it does not make sense. :)

[knyfe]

As a physicist I have to completely agree to Ellis comment as all theory fails if not fully understood which is the case for kites. Otherwise we would all stay with foils. Elli and I made the trip through the foils and both decided to give up on them.

Good to see that we have a kite designer here in the bay area. But wasnt Paul active on kite design through the zeroprestige.org webpage? G

[adamrod]

speaking of saul, I came across this website describing his board designs.

http://www.mit.edu/people/robot/zp/zeroprestige.html

one look and it's pretty apparent it's a tad outdated. interesting though.

[Greg]

I like there low-tech approach..
L.M.G.

[narly1]

he was doing some proto type testing of sail boat kites
for the spinnaker, very interresting stuff, of course he would trip on ollie and me ripping up and out of are top secret sail n site
to paly out in the middle of the bay.

my rapture1 didnt have a center sturt .

[Live2KITE]

Imagine what Saul and his buds could do with serious R&D budgets.