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Author Topic: tail weights and tail designs  (Read 1164 times)
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kite_pilot
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« on: April 08, 2014, 08:32 PM »

hi guys,
just want to chat r.e tail weights and tail shape/size on some stunt kites!
have tail weights been around a long time ?
whats there purpose during flite time,slow then down or position weight better e.c.t ?
i see not all stunt kite brands have this idea!
what average tail weight seems to work best ?
r.e the tail nose design on modern stunt kites they all seem to be very simiral in shape,design and size!
does the tail have much to do with flight performance from various designs or do very little ?
how are most tail weights added in some sort of a pocket i suppose ?
i suppose in light winds you wouldnt add weight to tail ?
can much been gained in removing top spreader in light winds ?
sorry for all the questions!,lol Grin
thanks
glen
« Last Edit: April 08, 2014, 08:48 PM by kite_pilot » Logged

smooth,peaceful winds! Smiley,in the bag so far a black/orange skyburner pro dancer,prism 4d, Smiley
BrianS
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« Reply #1 on: April 08, 2014, 09:16 PM »

Tail weights are often added to increase the moment of inertia to make pitch-based tricks (e.g., yo-yos) easier. (It allows the pilot to give the kite additional angular momentum, which helps it roll up.) It also moves the center of mass towards the tail, which can help with tricks like side slides. As you pointed out, it does add weight, which can be a liability in low wind.
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chilese
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« Reply #2 on: April 09, 2014, 01:01 PM »

Tail weights:

Pro:  Increases pitch rotation speed (yoyo for example)
        Helps keep nose up during side slide

Con:  Decreases flatness of spin tricks (who remembers table top flat axels?)
        Detracts from low end wind range

There are some other effects, but those are the main ones.  Smiley
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« Reply #3 on: April 09, 2014, 01:14 PM »

have tail weights been around a long time ? ---- whats your definition of long? Since roll ups etc came around I think they've been toyed with and around as well. Give or take a few years.

whats their purpose during flite time,slow then down or position weight better e.c.t ?
Don't get what you're asking with this one

i see not all stunt kite brands have this idea!
what average tail weight seems to work best ?
Thats dependent on the size of the kite, the cut of the sail, and the model of a certain kite- UL, Std, Vent,etc.

r.e the tail nose design on modern stunt kites they all seem to be very simiral in shape,design and size!
does the tail have much to do with flight performance from various designs or do very little?
Not super sure on that one but now that I think about it all the kites that I like have a wider tail section. I know lam ties his tails back a little. I'd ask him on that.

how are most tail weights added in some sort of a pocket i suppose ?
Most are yes. With brass nuts, valcro, etc.

i suppose in light winds you wouldnt add weight to tail ?
I never take my weights out of my kites. If they come without one, I'll leave it out.

can much been gained in removing top spreader in light winds ?
Honestly I don't really see much of a point in doing this, because you change the basic outline of the kite as well, which distorts the sail a bit. I notice a big difference in flight and I'm not super keen on it. The only kite that I didnt mind doing this to was the NikNak in the 90s. Granted I was a lot less experienced and probably couldn't feel much difference, but that was the only time I did it.

Hope this helps,
Devin
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Doug S
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« Reply #4 on: April 09, 2014, 01:15 PM »

If you are interested, you can calculate the moment arm and moment of inertia for the tail weight using the following formulas:

Moment Arm =  Distance (D in inches) from the center of gravity of the kite to the center of the tail weight, times (X) mass of the tail weight (W in grams).  (D X W) = MA in units of inch-grams or what every units you use for the measurements.

Moment of Inertia = Distance Squared (D X D in square inches) from the center of gravity of the kite to the center of the tail weight, times (X) mass of the tail weight (W in grams).  (D X D X W) = MI in units of inch squared-grams or what every units you use for the measurements.

Please note that as you add more tail weight, the center of gravity for the kite will change and become closer (lower value of D) to the center of the tail weight.  So if you want to see the effects solely due to MI, you would also need to add weight in the nose to retain the location of the center of gravity for the kite.  These equations would allow you to compare the tail weights for different stunt kites.  If I was to update Geokite, these are some of the simple equations that I would add.

Later,

Doug
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Allen Carter
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« Reply #5 on: April 09, 2014, 02:15 PM »

As slack line tricks evolved in the late '90s and early '00s, there was a constant struggle to design kites which could easily do radical tricks and expand the range of what was possible with a stalled kites while retaining favorable in flight characteristics. A higher aspect ratio wing would have more mobility in the pitch axis (flip onto it's back or belly or even roll up) but would generally be more difficult to fly smoothly and precisely. Many trade offs are evident in early tricky kites like the Stranger or Box of Tricks and even in somewhat later designs like the Prism Elixir. Absolutely great kites, but unabashedly shed flight quality for tricks to some degree.

In the early '00s some flyers, especially in Europe, started modding existing older designs like the L'Atelier Masque (a successful ballet & team kite) to get more pitch capability while still providing satisfying flight characteristics. Tail weights and adjustments to upper spreader positions and widths would often allow a previously "old school" kite to roll up, while changes in standoff placement improved other trick aspects. Within a very short period of time these mods to existing kites were incorporated into new designs and became the standard.

For years people fiddled with adding weights to kites and tuning kites by changing the amount of weight and or placement on the spine. A few years ago there were a lot of kites out with variable weight systems. Seems like getting the right amount of weight in the tail of kites has become a more normal part of design and there are fewer reports of having to "tune" tail weight, but it is still common. I tend to remove weights on some UL kites for the lightest winds. Some folks add more weight for heavy wind tricking.


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Allen, AKA kitehead
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« Reply #6 on: April 09, 2014, 05:24 PM »

About the only mod I make to a kite is the amount of weight at the tail, usually adding a little more to settle in on what I like.  I don't adjust it after that however - low wind, high wind, I keep the weight the same and the upper spreader in.

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« Reply #7 on: April 09, 2014, 08:25 PM »

I first used a tail weight, about 1992 or 91. i was trying to reduce the overstear in a silent kite and improve its precision. The effect I desired was there, but it was small compared to the weight. So i dropped the weight again.
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kite_pilot
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« Reply #8 on: April 11, 2014, 05:11 PM »

hi guys,
thanks for your explaination on tail weights!
cheers
glen
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smooth,peaceful winds! Smiley,in the bag so far a black/orange skyburner pro dancer,prism 4d, Smiley
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« Reply #9 on: April 12, 2014, 01:57 PM »

Yes, this discussion helped me to understand tail weights too.
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« Reply #10 on: April 12, 2014, 03:08 PM »

Doug S:

Adding weight to the nose can retain the c.g., BUT it will change the Moment of Inertia.

Adding weight to the nose will slow down the rate of rotation of a yoyo.
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John Chilese: Las Vegas, NV
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Doug S
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« Reply #11 on: April 12, 2014, 04:37 PM »

chilese,

You are correct.  What I was pointing out is that adding tail weight not only helps the moment of inertia for wrap up tricks, but it also lowers the center of gravity and increases the kite's negative static margin.  If the lower center of gravity allows you to perform other tricks the way you like, then everything is great.  If one is not happy with the potential loss in performance with a lower center of gravity, then they need to make other changes to see if they can have their desired center of gravity, while using higher density material in the tip of tail.  If you have a two piece center spine and the joiner is in the lower section, one could flip the center spine.  Everything is a tradeoff in aerodynamics.  When you make one attribute better, you may give up performance in another attribute.  The goal is to balance the various performance attributes to suite your flying style for the current weather conditions.

Doug
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kite_pilot
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« Reply #12 on: April 27, 2014, 12:26 PM »

i have noticed that all kites designs/manufacture seem to have the same shape,design and size of the rear tail design!
why is that?
any particular reason for this ?
what does a tail design shape have to do with flight in any way ?
if you have 2 differen shape design size tails willl they perform any diferent in flite time ?
cheer
glen
« Last Edit: April 27, 2014, 12:29 PM by kite_pilot » Logged

smooth,peaceful winds! Smiley,in the bag so far a black/orange skyburner pro dancer,prism 4d, Smiley
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« Reply #13 on: April 27, 2014, 12:45 PM »

Tail design influences the flight characteristic a lot.
A broad and wide tail catches more wind, meaning the kite will fly earlier, but it also produces drag which slows the kite down. And in a trick kite it is a lot of sail area that works against stuff like yo-yos.
While a small tail is pretty much the opposite.
So, you have to find a compromise in that you want to want from the kite in its design.
And of course then you have speedkites that more or less have very small tails or no tail at all.
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Allen Carter
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« Reply #14 on: April 27, 2014, 12:53 PM »

The shape of the tail area can vary a lot as seen in these photos. Not only in the outline, but in the width and depth.  (determined by standoff placement and length) The overall profile of the tail area is often referred to as the 'keel", similar to the bottom of a boat.











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