kite altitude record attempt
Posted 13 September 2010 - 03:01 PM
It has even "Guiness Book of Records, World Altitude Record Holder, 7 Miles High" badge. The kite has just 50" (127cm) span, so is pretty small and does not require strong line
Posted 09 February 2011 - 07:06 AM
#833, the one, the only.
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Posted 22 June 2011 - 11:14 PM
If the Celestron telescopes were able to measure angle of elevation with sub degree accuracy, the telescopes were placed at an accurately measured fixed distance apart, the telescopes were able to be leveled to <0.1 deg and the top kite constantly kept in view by both observers, then this is reasonably accurate method of altitude measurement. However the angle of elevation is not the only measurement required. The top kite's horizontal bearing must also be measured by each telecope using the position of the other telescope as a reference or another fixed reference point such as a tower or tall structure. (see the NASA Glen site for measurement of kite altitude). Gravitational catenary calculations applied to this record are clearly flawed because the role that wind drag on the line plays affects the curvature so much that the presumption of an unequal height attachment gravitational catenary is invalid. The line "absorbed" by the curvature or sag caused by wind drag on the line would be greater. Not only would the line sag toward the earth but the line would curve sideways as the wind direction varied with altitude. (wind shear described by Steve Lyman)
If you look up properties or strength of materials you will find the vertical length these materials will support, that is if you suspend a line of uniform thickness under gravity then these are the lengths in km at which the material will break.
Scifer steel wire 71.2
Spectra fiber 369
You can see that nylon(fishing line will break under it's own weight at 7.04 km or 22,880 ft. The kite line is at an angle and assuming the top kite is at 45 deg then the vertical component of the line weight before the weight of the line will break itself is 22,880/0.707 or 32,362 ft. Remember this is the maximum length of uniform diameter fishing line that can be suspended at 45 deg (WITHOUT kite(s)).
If the pull of 19 kites is 19 lbs (I suggest the net pull would be more than double that) the maximum length of 50 lb fishing line (flying at 45 deg) before line break would be (50-19)/50 x 32,362 = 20,064 ft. The maximum kite altitude before line break would be 20,064 x 0.707 = 14,185 ft
These calculations do not include wind drag on the line which would add to the line tension and cause the line to break much earlier.
If the kites combined pull is double my estimate then the altitude before line break would have been less than 10,000 ft. Also the line's thickness varied, that is, heavier, thicker and stronger line was added so the weight that the thin topline had to support was proportionally greater. There are so many scientific reasons why the altitude record claims are very difficult to support.
1. No 2 scope direct observation (3d triangulation).
2. Flawed catenary calculations based on dubious assumptions.
3. Physical properties of Nylon that make it impossible to support the lengths of line and the number of kites claimed.
Only a few sections of the "train" were recovered suggesting that some kites may have broken away.
While it would be great if Gary Indiana High School students did break the record in 1969, I think my skepticism is justified.
After my single kite record attempts I will prove (or disprove) my claims by attempting to recreate the Gary Indiana "record" flights. Let's see.
The only thing I can't recreate are the exact weather conditions on that day in 1969.
Posted 23 June 2011 - 04:39 PM
I always love your updates Bob, thank you - keep 'em coming!
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Posted 25 June 2011 - 07:49 AM
First I always wanted to know exactly what the line tension at the winch is in real time. With any piece of equipment I add to the winch and reel system, it must not increase the risk of line breakage. With this in mind I have done much research on techniques and devices to measure static and running line tension. The obvious first choice was a spring balance either measuring static line tension or moving line tension. This can be done a number of ways including direct pull opposite the direction of the line pull, at 90 degree angle to the line pull with a 30 degree deflection of the line. The last method requires 2 fixed pulleys which the line passes around and the hook of the balance pulling the line so that a 30 deg angle is formed around the hook. This 30 deg angle is chosen because it results in a quarter of the line tension transfering to the spring balance. Think about sin30 deg being 0.5 the line either side of the balance dividing the line tension by 2. The tension shown on the spring balance is then 0.25 of the actual line pull. The value shown on the scale is then multiplied by 4. This is only good for static measurement, that is, the winch would need to be stopped then the line hooked and attached to a fixed point to give the required 30 degree angle. This is a cheap but cumbersome method and there is some danger that a hook sliding over the line will produce friction and enough heat to melt the Dyneema.
Using a balance attached to an open sided bracket like a walkdown pulley that some of you "normal" kite flyers use, would result in a system that can measure running line tension but the pulley needs to be ridgidly located but free to move up and down within the constrants of the spring tension. I don't want the pulley to be flopping around with the line jumping off track. Ok, that's cheap and do-able but still a little crude and difficult to read line tension quickly.
The next method under investigation is load cells and dedicated tensionmeters. The are a lot of commercial tensiometers but only a few in the tension range of 5 - 500lb. These mostly use a 3 pulley device with the centre pulley connected to a load cell. They are anywhere between $1,000 and $5,000. Some don't cater for really thin lines although they are in the load measurement range I need. Like many kite builders I am adaptable and often will scroung bits and pieces from the oddest places. In this case I found a bathroom scale with 4 load cells and a digital readout. The 1st one was $20 which I hacked but it didn't turn out very good. I have another now for $17 and basically I'm going to remove the glass platform and replace with 4 mm aluminium plate. On this plate I will bolt a kite pulldown pulley and mount the lot on a small platform/bracket above the winch guide pulleys so that the line angle formed around the measuring pulley is 30 degrees. The is a much more robust system than a spring balance. Another simpler way is to use a spring bathroom scale. I won't need to press the platform to turn the scale on from auto off.
The 3rd way is to use an electronic guitar tuner to measure the line vibration then convert the Hz value to lb tension with a spreedsheet imput with the line properties and distance between pulley sopports. I may not get to test this in the field before the record attempts but it is interesting. Why do I want to know line tension. So I can judge how close I'm coming to line breakage and whether I should reel line in slow or can do it faster. Also I may need to delay kite retrieval until the wind speed drops. It also tells me if line broke because of excess pull or due to a line flaw.
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