Kites & kiting

[Turtle]

New bridle attached. :thumbs_up Tail attachment loops attached to back longerons. :thumbs_up Two 9 foot strip tails cut and ties sewn on. :thumbs_up :thumbs_up One bright idea which may or may not work outlined below.

 

So I got thinking the 2 long strip tails might tangle when flown just 2 feet apart as the longerons are. Not a happy prospect. :omg: So then I thunk if I put a short bridle string between the longeron loops and fly a single tail from that! Not one to leave well enough alone, I further thunk why not make the kite bag a tail!! I expect it to inflate and I have sewn on a tie so I can try it out. B) The tie makes a good bag closure as well. A two fer!! Attached below is a simulated view of what the longeron-bridled-kite-bag-tail may -or may not- look like in flight.

[DFINITLYDISTRUBD]

So situated as you are near a large body of water, you may be able to take advantage of morning lake breezes and evening land breezes. >>

Oddly, in the morning unless we're seeing heavy weather, the lake is flat as glass and breezes are nearly/to nonexistent....pretty much the same for the evening. Otherwise if there are light breezes they are strongest at mid-day and taper off as the day progresses. When we have bouts with stiffer breezes (which are more the norm) they remain strong throughout the day and evening. Of course if heavy weather is due the stiff breezes are accompanied by forceful gusts.

[Turtle]

Oddly, in the morning unless we're seeing heavy weather, the lake is flat as glass and breezes are nearly/to nonexistent....pretty much the same for the evening. Otherwise if there are light breezes they are strongest at mid-day and taper off as the day progresses. When we have bouts with stiffer breezes (which are more the norm) they remain strong throughout the day and evening. Of course if heavy weather is due the stiff breezes are accompanied by forceful gusts.

 

Sounds like you have a handle on trends. Are you going to fly by the water or what's the plan?

 

Laurie? Do you put tails on your kite?

 

Moontanman? What you flying?

 

Well, better get on with the bad news. Matilda broke a wing spar. :omg: Well...really I broke it for her trying to turn her over on the ground. :doh: So she's out of commission while I rework her. Watching her up close on launches I see her cross spar is set too high as well. That means new pockets and I'm running out of thread.

 

Nevertheless, I flew her broken wing and all while I had some wind and grabbed a little hand-held viddy. I don't think the tube tail inflated so maybe I need a vent in the end? :shrug: With the broken spar she was listing to port and I added the starboard wing-tip tail to even things up. Banners on line every 50 feet. Looks like a rag bag, but she's flyin'!! :lol:

 

http://www.youtube.com/watch?v=vf2VEwmZ4qs

[DFINITLYDISTRUBD]

That the delta-c type can overfly you ie. fly directly overhead baffles the **** out of me! That means somehow it is able to travel into the wind!!! or is it that it generates so much lift with so little drag.....that it in it's desire to go up instead of aft....pulls the line straight up?

 

Not sure, not many local places to fly near the lake....know of a few within 20 minutes drive though, so I dunno just yet, things are up in the air as far as plans go for now.

Edited July 28, 2013 by DFINITLYDISTRUBD

[Turtle]

That the delta-c type can overfly you ie. fly directly overhead baffles the **** out of me! That means somehow it is able to travel into the wind!!! or is it that it generates so much lift with so little drag.....that it in it's desire to go up instead of aft....pulls the line straight up?

 

snip...

 

I'm not sure I can give an adequate explanation. Technically all kites are 'travelling into the wind' so that shouldn't **** us. Little drag lots 'o lift sounds good for getting a high angle, but the drag is dependent on surface area but surface areas on 2 different types of kites can be equal and still have them fly at different angles.

 

I'm thinking its the wide wing span on delta-C's that reduce downwash and give more lift and higher angle of flight. ??

 

Downwash Effects On Kites @ NASA

...

 

We use Clo for the lift coefficient and Cdo for the drag coefficient because there is another aerodynamic effect present on most kites. If we think of a kite as an aircraft wing, and use the terminology associated with aircraft wings, most kites have a low wing span (length from side to side) relative to the surface area. Most kites therefore have a low aspect ratio AR which is defined to be span s squared divided by the area A. AR = s^2 / A

 

Near the tips of a wing the flow spills from the under side to the top side because of the difference in pressure. This creates a downwash which changes the effective angle of attack of the flow over a portion of the wing. For low aspect ratio wings, the portion of the wing affected by the downwash is greater than for high aspect ratio wings. Since most kites have a low aspect ratio AR, we have to include the effect of the downwash on the lift and drag coefficient. The equation for the lift coefficient is:

 

Cl = Clo / (1 + Clo / (pi * AR) )

 

The effect of downwash on lift coefficient is shown on the plot. Low aspect ratio wings (AR ~ 1) have significantly less lift than higher aspect ratio wings (AR ~7). The effect of downwash on the drag coefficient is called the "drag due to lift" or the induced drag of the wing. The equation for induced drag is:

 

Cd = Cdo + Cl^2 / (.7 * pi * AR) )

 

where the .7 is an efficiency factor for rectangular wing shapes.

 

 

 

 

 

 

[Turtle]

I'm not sure I can give an adequate explanation. Technically all kites are 'travelling into the wind' so that shouldn't **** us. Little drag lots 'o lift sounds good for getting a high angle, but the drag is dependent on surface area but surface areas on 2 different types of kites can be equal and still have them fly at different angles.

 

I'm thinking its the wide wing span on delta-C's that reduce downwash and give more lift and higher angle of flight. ??

 

Downwash Effects On Kites @ NASA

 

 

Ok, check me as I try and calculate Matilda's AR (Aspect Ratio). At the above link they give the equation as

Most kites therefore have a low aspect ratio AR which is defined to be span s squared divided by the area A. AR = s^2 / A

 

My wings are each 1/2 of a 6 foot x 6 foot square, and with 2 wings that's 36 square feet. I haven't worked out how to calculate the effective area of angled surfaces yet, so I'll just guess the cells add 4 square feet and add to get a total of 40 square feet of Area. I have a 14 foot wingspan.

 

AR = 14²/40

AR= 196/40

AR=4.9

 

How's that look?

 

Here's NASAs diagram to put that AR in perspective. Top right in Blue.

 

[Turtle]

Well, better get on with the bad news. Matilda broke a wing spar. :omg: Well...really I broke it for her trying to turn her over on the ground. :doh: So she's out of commission while I rework her. Watching her up close on launches I see her cross spar is set too high as well. That means new pockets and I'm running out of thread.

 

snip...

 

So what I saw was the wingtips bending in toward the centerline using the cross-spar joint as a fulcrum and effectively reducing my wingspan. In the attached drawing the Red arrow is the fulcrum and the dark green line (left side of drawing) is the deformed wing-spar position. Rather than getting stiffer sticks or lowering the cross-spar I'm thinking of adding 2 new cross spars indicated in the drawing as Brown 1 stick & 2 stick . Since these don't span the vent, the wings tips could still move up, just not in. Note that I would leave the original cross-spar as it is.

 

The long breaks in Doug fir make for lots of glue surface, so I have glued the broken wing-spar back together. When it's out of the clamps I'll wrap it tight with string and glue that down. Bob's yer uncle. Break images attached. Let's see you do that with carbon fiber, fiberglass, or aluminum! :lol:

[DFINITLYDISTRUBD]

Technically all kites are 'travelling into the wind' so that shouldn't **** us.

While kites fly "nose to the wind" I wouldn't call what most kites do "traveling into the wind" unless it's being pulled or line is being taken in and the kite is actually making forward progress. Most are willing to travel "across" or with the wind, but to make headway without being pulled by either the person flying it walking into the wind or pulling in line, I've not seen...which is of course why that Delta-C can actually pull the line straight overhead and even create slack in the line whilst doing so baffling. (I'll have to reread the post to confirm this to be the inspiration for the last post)

 

 

EDIT:

(I'll have to reread the post to confirm this to be the inspiration for the last post)

 

 

This high string angle is a characteristic of delta-Conyne kites. I will need to add tails to hold Matilda back and keep her from over-flying me. When they overfly they get directly overhead, then the kite tips nose down and dives for the ground. Unless you can get tension back on the line and move back in front of the kite,

Yup, that's what I was thinking, I was thinking about.

 

Makes me think,...some sort of force controlled, tension powered flaps on the rear could be devised to "brake" the kite....possibly in the form of a weight attached to a second line that is placed a distance away from the main line...that would as the kite approached the kiter increase drag causing the kite to settle back to a point between anchor and kiter.....Or perhaps instead of an anchor a second line or control rod attached near the bridle that as angle decreases pulls the braking surfaces into action.....wonder why I've never seen a rigid bridle on a kite? (as opposed to cable or fabric)...seems it would make for more stable flight by eliminating the side to side flex at the bridle...to my minds eye, eliminating that flex would increase resistance to "banking" by increasing leverage at the keel forcing the kite to remain perpendicular to the line....I dunno....just being typical me, take something relatively simple and look for ways to make it "better" at it's function.

Edited July 29, 2013 by DFINITLYDISTRUBD

[DFINITLYDISTRUBD]

Neato, you can actually add attachments directly to the post.

 

Ok, on to those yellow lines.

If I were to add additional rigid structures to the kite, I would add them as drawn in yellow. Seems to me it would eliminate flex in the (longerons? Why is it the post you want to find is always the best hid?) while still allowing the wing to take it's airfoil shape and keeping wind resistance caused by additional structural supports to a minimum.

 

The thick black line is an optional support which seems may or may not be necessary...I dunno...though looking at it again it should be in front of the rear green whatchamajig instead of behind.

Edited July 29, 2013 by DFINITLYDISTRUBD

[Turtle]

While kites fly "nose to the wind" I wouldn't call what most kites do "traveling into the wind" unless it's being pulled or line is being taken in and the kite is actually making forward progress. Most are willing to travel "across" or with the wind, but to make headway without being pulled by either the person flying it walking into the wind or pulling in line, I've not seen...which is of course why that Delta-C can actually pull the line straight overhead and even create slack in the line whilst doing so baffling. (I'll have to reread the post to confirm this to be the inspiration for the last post)

 

I think it gets into semantics here. I recently read a tract by a guy arguing it is wrong to consider kites as giving lift as an airplane wing. :shrug: Kites are, as kites do. :D

 

EDIT:

 

Yup, that's what I was thinking, I was thinking about.

 

Makes me think,...some sort of force controlled, tension powered flaps on the rear could be devised to "brake" the kite....possibly in the form of a weight attached to a second line that is placed a distance away from the main line...that would as the kite approached the kiter increase drag causing the kite to settle back to a point between anchor and kiter.....Or perhaps instead of an anchor a second line or control rod attached near the bridle that as angle decreases pulls the braking surfaces into action.....wonder why I've never seen a rigid bridle on a kite? (as opposed to cable or fabric)...seems it would make for more stable flight by eliminating the side to side flex at the bridle...to my minds eye, eliminating that flex would increase resistance to "banking" by increasing leverage at the keel forcing the kite to remain perpendicular to the line....I dunno....just being typical me, take something relatively simple and look for ways to make it "better" at it's function.

 

 

Check this little job by Alexander Graham Bell. Great minds think alike?

 

 

Alexander Graham Bell Kites @ www.design-technology.org

The image below shows Bell holding one of his kites. The kite is made up of two hexagons (a six sided shape).

 

Each hexagon has six radial divisions or wings. The two hexagons are held together with a centre pole having a moveable weight in the centre of it. The adjustable weight could slide along the pole in order to find the centre of gravity. At this point it is perfectly balanced. The photograph is courtesy of the National Geographic Society.

 

 

Neato, you can actually add attachments directly to the post.

 

Ok, on to those yellow lines.

If I were to add additional rigid structures to the kite, I would add them as drawn in yellow. Seems to me it would eliminate flex in the (longerons? Why is it the post you want to find is always the best hid?) while still allowing the wing to take it's airfoil shape and keeping wind resistance caused by additional structural supports to a minimum.

 

The thick black line is an optional support which seems may or may not be necessary...I dunno...though looking at it again it should be in front of the rear green whatchamajig instead of behind.

 

Mmmmm...I think the yellows would flex too. The black is just one of at least 6 which would be necessary to fly simply the triangular box with no wings & I may try some variation of it. An airfoil shape, i.e. curve in the fabric is not necessary for a kite, as seen in tight-strung kites such as square box kites or those snowflakes for example. That NASA modeler I mentioned makes a point of saying all surfaces are considered flat plates as the math involved in calculating forces on a curved sail is daunting. If it daunts NASA, I daunt want to try it myself. :lol:

 

Off to watch some glue dry and ponder my next experiment.

[DFINITLYDISTRUBD]

I think it gets into semantics here. I recently read a tract by a guy arguing it is wrong to consider kites as giving lift as an airplane wing. :shrug: Kites are, as kites do. :D

Wasn't trying to get into semantics...was trying to keep the two concepts straight in my head.

 

An airfoil shape, i.e. curve in the fabric is not necessary for a kite, as seen in tight-strung kites such as square box kites or those snowflakes for example. That NASA modeler I mentioned makes a point of saying all surfaces are considered flat plates as the math involved in calculating forces on a curved sail is daunting. If it daunts NASA, I daunt want to try it myself. :lol:

While it may be unnecessary to build in an airfoil shape, fabric kites seem to adopt one anyway (well from what I've seen flyin em...in fairness my experience with kite variety is extremely limited).

 

Mmmmm...I think the yellows would flex too. The black is just one of at least 6 which would be necessary to fly simply the triangular box with no wings & I may try some variation of it.

I would expect some flex regardless of how the kite is built. That said I believe the triangles created by the longerons, spars and the braces (the yellow lines) would prevent the wingtips from bowing in as described here

So what I saw was the wingtips bending in toward the centerline using the cross-spar joint as a fulcrum and effectively reducing my wingspan.

but would not effect vertical movement of the tips. The black brace was to counter the inward force that most certainly would be applied (I now wonder if there is a brace there already, as there certainly must be something that keeps the green section from collapsing). Back to the yellow for a second: bowing in the braces could be reduced and guided by adding a "tie in" similar to the "laces" in the roofs of dome tents that secure the rainfly to the crossed main supports at the center of each brace.

 

 

I dunno, probably over-thinking things.

Edited July 29, 2013 by DFINITLYDISTRUBD

[Turtle]

Wasn't trying to get into semantics...was trying to keep the two concepts straight in my head.

 

Trying to keep concepts straight in one's head is semantics as I have used the term.

semantics

2. Linguistics The study of relationships between signs and symbols and what they represent.

 

 

While it may be unnecessary to build in an airfoil shape, fabric kites seem to adopt one anyway (well from what I've seen flyin em...in fairness my experience with kite variety is extremely limited).[/size]

 

A flat rigid board held at an angle to the wind is also an airfoil shape because it creates drag & lift. I agree fabric never behaves as a flat rigid board in practice.

 

I would expect some flex regardless of how the kite is built. That said I believe the triangles created by the longerons, spars and the braces (the yellow lines) would prevent the wingtips from bowing in as described here but would not effect vertical movement of the tips.

 

I agree the yellows would limit tip flex.

 

The black brace was to counter the inward force that most certainly would be applied (I now wonder if there is a brace there already, as there certainly must be something that keeps the green section from collapsing).

 

The cross-spar [blue horizontal in drawing] already in place holds the rear longerons apart & otherwise the tension of the wings fastened to the 2 rear longerons pulls the forward cell sails taught against the leading longeron and the tension of the flying line to shape the triangular box part. You may notice in some of the videos that when the kites are on the ground they are completely flat, as the triangular cell has no internal braces. [This stick-less triangle box is at the core of Conyne's patent.]

 

Back to the yellow for a second: bowing in the braces could be reduced and guided by adding a "tie in" similar to the "laces" in the roofs of dome tents that secure the rainfly to the crossed main supports at the center of each brace.

 

 

I dunno, probably over-thinking things.

 

 

I actually did add tie-ins where the cross-spar crosses the longerons. They aren't standard that I can tell from pics & plans and the cross-spar is usually allowed to flex. Without ties is how I broke Alida's spar as it wasn't strong enough for my hard tugs trying to make the light blink. I figured if I tied it down then it couldn't flex and if it couldn't flex it couldn't break [in the middle]. :shrug:

 

Anyway, I could put in rigid aluminum tubing for my wing-spars and that would stop the excess flexing. Not affordable on my budget I'm afraid so I'm just cobbling together what I can with what I got. I can't imagine overthinking that! :hammer:

[DFINITLYDISTRUBD]

Semantics, was assuming the more negative use of the term. Really trying not to be a PITA.

 

I agree fabric never behaves as a flat rigid board in practice.

Ok, so I seem to have managed one correct thought and statement.

The cross-spar [blue horizontal in drawing] already in place holds the rear longerons apart & otherwise the tension of the wings fastened to the 2 rear longerons pulls the forward cell sails taught against the leading longeron and the tension of the flying line to shape the triangular box part. You may notice in some of the videos that when the kites are on the ground they are completely flat, as the triangular cell has no internal braces. [This stick-less triangle box is at the core of Conyne's patent.]

I knwe that the lower portion was floppy, did not know that the portion between the wings had no bracing other than the cross spar. I suspect that any effort to stop the wing from using the cross spar as a fulcrum would cause the rear triangle to compress unless it received a full span brace or a shorter brace between the two red braces...I'm probably wrong (no experience with Delta-C's). EDIT: Ehrmm, Uh DUH!! I can't believe I missed that! The tension from the bridle holds the bottom open...and for a second (I forgot no bracing between the wing for the aft triangle)....so what...oh yeah the longerons and the cross spar...so it could flex and deform the rear triangle.....I dunno over-thinking and/or under-thinking again.

 

Again not trying to be a PITA or question/dismiss any claim, just offerin suggestions and attempting to grasp some of the concepts presented (like a kite that is capable of pulling the line true vertical).

 

Plenty wind today...also plenty rain...only flight, my umbrella.

Edited July 29, 2013 by DFINITLYDISTRUBD

[Turtle]

Semantics, was assuming the more negative use of the term. Really trying not to be a PITA.

 

To be sure, nothing you have said strikes me as PITA-ish. On the contrary, I think your postings and this thread in general epitomize the spirit of this forum. :thumbs_up

 

Ok, so I seem to have managed one correct thought and statement.

I knwe that the lower portion was floppy, did not know that the portion between the wings had no bracing other than the cross spar. I suspect that any effort to stop the wing from using the cross spar as a fulcrum would cause the rear triangle to compress unless it received a full span brace or a shorter brace between the two red braces...I'm probably wrong (no experience with Delta-C's). EDIT: Ehrmm, Uh DUH!! I can't believe I missed that! The tension from the bridle holds the bottom open...and for a second (I forgot no bracing between the wing for the aft triangle)....so what...oh yeah the longerons and the cross spar...so it could flex and deform the rear triangle.....I dunno over-thinking and/or under-thinking again.

 

Again not trying to be a PITA or question/dismiss any claim, just offerin suggestions and attempting to grasp some of the concepts presented (like a kite that is capable of pulling the line true vertical).

 

Plenty wind today...also plenty rain...only flight, my umbrella.

 

 

While I flew a large delta-Conyne with a camera 30 years ago, I never built one so I'm learning right along with you. :smart: There is supposed to be flex in the wings, just not as much as my light sticks are allowing.

 

Another mistake I made was not providing closures at the openings where the wing-spars slide in and so they were riding up out of the pockets. I have some Velcro scaps from the original cover and will be rectifying this problem. It will take me a bit as I have to rip out some stitching to be able to sew opposite sides of the pocket. No worries, no hurries.

 

To Matilda's credit, she flies in spite of all the minor glitches. As to the overflying, this is not the behavior of the kite in a steady wind. It seems to happen when the wind slacks off, the kite loses lift and starts to fall and as it does it tips forward and descends into the wind as a diving glider would/could. Most sources I've seen give the angle of the flying line for these kites as 50º. This is an idealized line from the anchor to the kite, but as you note the line is actually a curve -called a catenary- which is shallower toward the anchor point and steeper near the kite. Properly tuned and flying in a steady wind these kites hang virtually motionless & with a strong pull on the line.

 

I also note that back in the early 80's there was no internet and so much of what I am currently finding is new. Back then it was all about talking to other kiters and trips to the library. (That a big building full of books, magazines, newpapers & photographs for those of you who don't know. ;) )

 

So, onward & upward!!

 

 

 

[DFINITLYDISTRUBD]

Ooooooooh

 

 

 

 

 

It dawns on me that I've been a doofus with that whole the bowing of the wings could compress the rear triangle. um, Uh duuuuuuuh! they aren't rigid wings they're fabric!

 

In my eagerness I'm overlooking obvious flaws in my logic....getting light in the head in my increasingly old age I think

[Turtle]

Ooooooooh

 

 

It dawns on me that I've been a doofus with that whole the bowing of the wings could compress the rear triangle. um, Uh duuuuuuuh! they aren't rigid wings they're fabric!

 

In my eagerness I'm overlooking obvious flaws in my logic....getting light in the head in my increasingly old age I think

 

Of the most knowledgeable kiters I have met, 78.3% merit(ed) the moniker 'geezer'. :santa3:

 

I may have some other video of the kite flying steady if that would clarify your wooziness. I didn't upload them because it's rather boring as a video to see nothing going on. Nevertheless they are useful for studying the performance at leisure. I guess now I'll go try & upload something even if it doesn't help you. No skin off my fanny as the geezers used to say. :lol:

 

PS Moontanman? Do you copy? ...

[Turtle]

So I guess I did upload the vid showing steady high flight; Matilda 2 . I did find a video of her flying low before I broke her wing and I see all the problems even in a light wind.

 

The vid:

 

http://www.youtube.com/watch?v=U8foCsVoPdQ

 

I grabbed a still and marked it up & have it attached.

 

Pink arrow upper right is the wing-spar coming out of the pocket.

 

Red curve under wing on right to show how exaggerated the 'cup' is. (I'm tempted to call this wing-curve 'camber', but since the sail is the same thickness throughout I don't think that's technically correct. Must be a good & proper term for it out there somewhere. :shrug: )

 

Blue arrow on right points to a fold in the sail that should not be there. Didn't notice this in flight. :(

 

Green curved line at back of bottom cell to show it's not straight like top cell. I honestly don't recall if this is normal or not but I'm inclined to think not. . Didn't notice this before either. :blink:

 

Yellow line on left is parallel to the 'normal' leading edge when the kite is flat. See the wing-spar on that side is also creeping out of its pocket, and the fulcrum of the cross-spar is easily seen.

 

Well, got my work cut out for me.

 

Moontanman? You got yer ears on? Surely you have flown a kite in your many years amblin' on this 3^rd rock from a star. Come on...spill it... B)

Edited July 30, 2013 by Turtle