Conclusion at the end
 Plans
 

If you just want to make an ESP then you only need to read the important bits which are put in tables like this with a yellow background. You can skip through the following section looking for the yellow bits then move on to the plans for mod 2, this is the one to make. Mod 3 is still in the planning stages.

From the results of ESP mod 1, I've decided to reduce the width of the nose for mod 2.

This should help prevent nose collapse.

This model will be about 2m wide and so I've reduced the number of panels to 7 on each side. No point making a bigger one until it's flying well. The panel widths are around15cm. This works out quite well to fit the panels on A4 printouts in sections.

The trailing edge (TE) has also been changed to reduce the amount of air that spills from it.

The blue line shows the original which stopped at y = 0. The new version continues to y = -1.32 which is the lowest point of the underskin. I've changed the elliptical shape of the rear of the foil in order to achieve this but the change is slight when viewed over the whole foil. This changed trailing edge will need careful adjustment to find the optimum length. I've marked every 1/4 cm of the extension on the patterns. This way one will be able to unpick a little then fold in or cut off 1/4cm at a time until the best length is found. When I came to drawing the patterns onto material I only took every other line of the extension. It looks like half cm adjustments should be sufficient.
 
 
 
 
 
 
 
 
 
 

2001-02-11 Turns out the maximum flap seems right so no adjustment should be necessary.  If you seem to have too much flap (it won't take off) you should simply be able to roll up a cm at a time after construction (in the middle, taper off to the edges) until it will move forward. You do need the leading edge (the junction of upper skin and lower skin) marked. Use this as the reference point when measuring out the distance to the nose tie position.

The bridle will also be changed to a lower angle as the flaps should enable flying at lower angle. Time will tell. From Mike's observations that the original is reluctant to move forward it could be that this may be improved by moving the bridle focal points further towards the trailing edge. The attachment point will then be further behind the centre of lift which should drive it forward.

Here are the plans for mod 2.
Last updated 2000-03-1
 

It would be rather nice to know how many ESP's are made and where they are. So please mail me if you make one. Tell me the town and country where you live and send a pic if possible. I'll do a gallery of them, perhaps as a map of the world with flaglinks to images.

 

If you have problems with the plans then let me know what resolution and size you'd like and I'll send them by e-mail.
 
 

2001-02-28 Added an excel file (format excel 4) for the above full image panel plans in x,y coordinates. You can scale the coordinates as you wish. Don't forget, multiply both x and y by the same factor. Multiplying by 1,414 (square root of 2) gives twice the area. Download Excel file

 

Other sizes and formats available There is now a file available for the ESP mod2, 1.5 sq m, in autocad format. Contact me. Ditto an autocad file for a 2.7 sq m.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Nose tie lengths and positions I forgot to add these points to the plans so here they are, it's fairly easy to measure from the leading edge, ie the junction of the upper and lower skins, which is marked on the plans. All measurements in cm.

Junction of panel #'s	3/4	4/5	5/6	6/6 (left and right)
Linear distance from LE along seam	2,9	5,1	4,8	4,8
Nose tie length	2,7	5,0	5,0	5,0

Construction tips You need lines on the patterns on alternate sides for left and right sides. I've drawn the plans onto the kite material (chikara) using carbon paper. I cut around the patterns leaving a cm all round. This way I could draw on the plans exactly on the lines and transfer through the carbon paper to the material. I either put the carbon paper, carbon side up, underneath the material or on top of the material, carbon side down, to produce left and right panels. The alternative is to cut out the pattern exactly and draw round it. There is no nose reinforcement line, you just need a few cm of reinforcement where the nose ties attach to the upper skin. I left an allowance of 1cm at the leading and trailing edges and 4mm along the seams before hot cutting. The seam allowance depends on how you do the seams. When it comes to sewing it seems easiest (and most exact at this critical area) to start from the nose on the left side of the kite (with the kite facing you as when flying). This way you only ever have one panel inside the "u" of the sewing machine. Start with one line right down the seam, straight stitch, 4mm stitches or more. The most important thing here is to get the first stitch dead right. Overlap the seams and start at the very edge of the pattern lines. Don't worry about sewing over the allowance at the leading edge yet. Just put in one stitch then pull the seams into line, do about a cm more then check again. Keep on like this, gradually increasing to sewing no more than 3cm at a time so that the lines don't go out of sync. Be careful to get the same tension in both layers as any difference here accumulates to the trailing edge so they won't match up exactly. On the next design I shall put markers along the sides of each panel to make alignment along the chord easier. Remove the kite after doing the straight stitch seam and go back to the beginning and go over it with a zig-zag, this time covering the leading edge and trailing edge seam allowance. I used the widest zig-zag I have which almost covers the seam allowance, still at 4mm stitches. It's not so evident at first but it's nice to see the kite begin to curl up into shape when you've done a few panels. Andy B. has a good description of flat felled seams if you want to try this method. It'll be a stronger seam and probably necessary for larger kites. You'll find the pictorial description from his index page. http://albums.photopoint.com/j/AlbumList?u=19203 I decided that plain overlapped seams would be good enough for this small one.

The Bridle

If the skin shape is right then the inflated kite should hold it's shape by means of wind pressure so I started with just two lines on the leading edge.

The wind does hold the kite in shape and all that's needed is four lines on each side.  No spine lines at all and you still have full control in turning and braking.

The 2nd line in the table below is the LE bridle and the 3rd and 4th lines together make up the TE bridle Lengths in cm. Finalised 2001-02-25. 2-3 changed to 133cm.

Flight testing.
2001-02-10
18:00. Minus 4c. Small puffs of wind now and then. Flew on bridle only first time. Takes off easily, turns and moves forward easily. Some signs of nose collapse. LE looks at bit odd. Check.
I'd used the wrong line length on the forward line, 126cm instead of 136cm. Changed it.
Second flight test.
21:00. Minus 5c. Even less wind, well actually the same but fewer and further between puffs. Shape looks better. No signs of nose collapse now. Still accelerates forward when the wind picks up. It's fast. Turns ok.
No possibility of checking with longer lines as it was too dark to see the lines to unwind them.

2001-02-11
Today we have a snow storm. I went out nevertheless for more testing. Managed to test on 5 metre lines. As the angle of attack is in the bridal lines the main lines should all be the same length. Very gusty today but I managed to fly it for a while.
It seems the nose tie positions are not quite right but this should be simple to correct. It's probably just a case of making the tie position symmetrical around the leading edge.

Beats me how I did the first calculation, the nose tie lengths and positions in the table above are now corrected. Yet to be flight tested for the new positions.

2001-02-13
Changed the nose ties lengths and positions, looks much better now. The calculated values look right so I won't experiment with them. Takes off even easier. Pulls a little more too. Turns very well using a combination of TE lines and turning the handles like a steering wheel. No sign of nose collapse except when flying forward fast into a dead zone with no wind. Well I am flying in the woods as usual so it's gusty!

The calculated bridle lengths are fairly close. Make sure to attach longer lines for the bridle than you need, except for the wing tip which can be the reference. This will allow you to adjust for any differences in the way you've sewn it together. I've said before, ideally the panels should be joined to the outside of the pattern lines. This is practically impossible when you have 2 layers overlapped. Get as close as you can and you will have less to adjust. A very small difference in overlap or butting will influence the curvature a lot and this in turn will change the bridle lengths considerably. I'd allow at least 25 cm over for each bridle line.

It's easy to knot the line at different positions and adjust simply for a smooth curved outline. This I find easiest to do at the bridal focus. Use a lark's head knot to attach the main lines. When all the adjusting is done you can tidy it up if you wish and cut off the superfluous knots. Use good quality line for the main lines and bridles. Preferably dyneema or spectra. Melt the cut ends to seal them against fraying.

Planning on a short movie to demonstrate it soon. Meanwhile here's a few pics, 2001-02-17.
.............
 

These are pics of mod2 from the plans above which gives an area of 1.5 sq.m. Not completely adjusted yet. Taken on a very gusty day, hence the partial collapse on one of the images above. It still looks like the nose needs to pulled down a little more. It's obvious now that it's not possible to get rid of the attachment bumps on the leading edge completely. As it is now it seems to fly very well. One surprising thing is that the control inputs are very small. It doesn't take much pulling on a brake line at all to turn it. My 25 cm handles for 4 line flying seem almost too long but one adjusts to it fast. The lack of spines isn't affecting the controllability, seems almost the reverse is true. There's a short movie of flying the ESP-2 in a low gusty wind on the index page. Worth the download just to hear the music which is by kind permission of Nåid.

2001-02-23
Experiment.
Added a line through the channel in the trailing edge of the underside of the nose, fortunately there was one. If you look closely at the pic above (wing by house) you'll see the nose is tending to get pushed up. The line is anchored at the end of the nose where it has tapered away. Made one end adjustable to start with and pulled it in until the nose didn't get pushed up anymore. Seems to work fine.
Now if the wind would just stay in one direction for more than a few seconds I could perhaps get to fly this thing. Minus 8 deg C and bigger gusts. Northerly winds, that means another part of the woods...
Managed a few minutes with 10m lines though it was easier with 5m.
2001-03-24
Removed this line again. It's not needed. The distortion is caused by the reinforcement line behind the nose on the upper skin. Removed this reinforcement.
Result:- Flies better. Flew today in walking speed wind. Takes off even easier than before. Getting used to keeping my hands together. Very necessary to be able to control it.
Flew it last week in a running speed wind, it nearly lifted me and it's only 1.5 sq m!

2001-02-25 Wind NE and minus 8C, that's means another site, a frozen lake. The wind was still gusty but a little longer between changes in direction. Had to wait minutes between gusts. Flying on 15m lines. Conclusion. Seems to fly well when it gets a steady wind. Pulled nicely too. 25cm handles are however too long for this kite. It's so sensitive that shorter handles, say maximum 20cm would be much more appropriate for this size kite. As it was I was continually overcorrecting and causing it to spin. Further experiment has shown that a distance of 19cm between anchor points for the flying lines works well with the 1.5 sqm kite. Scale up or down linearly if you make another size.

2001-02-25
Experiment.
Tried skipping the tip bridle lines, I just left panel 0 to flap about. Worked fine and I couldn't see any difference. The curvature of the leading edge is such, however, that it's not possible to skip the foremost bridle line.
2001-07-02
Further testing shows that it is not a good idea to skip panel 0, it works fine in a low wind but not in a higher wind. The kite then shows a tendency to flap about and gives signs of nose collapse.

2001-03-28
Removed the reinforcement line behind the nose on the upper skin. This was to be used as an anchor point for the nose ties. This line, however, caused the upper skin profile to be a little distorted. A slight indentation visible on one of the pics above. It could have been caused by a different stretch in this line or by a little tension in it caused by the sewing.
This line is not needed. Removing it has removed the distortion and the result is that it flies even better and in a lower wind.

The wind really does hold the kite in shape so well that I thought the nose ties may be unnecessary. I haven't removed them on the 1.5 sq m mod 2 but had suggested skipping them. I've now had a report back from Matthias S who has tried it without. I'd thought that without these ties it would be possible to fly the kite forward fast then tilt the handles towards yourself at the top quickly so that you remove all tension to the trailing edge whereupon the nose collapses and the kite turns inside out and upside down. You should then be able to continue flying in the other direction with the controls reversed (the le and te lines twist)          This is not possible when there are nose ties as the nose won't reverse but you can flip it inside out and recover. Matthias found that launching was a lottery as the kite could be inside out on takeoff. Trying to take off with reversed controls proved to be murder. The recommendation now is, DON'T skip the nose ties.

Conclusion Be careful with scaling up as this kite really pulls in a good wind. The max/min ratio is high. From nearly stalled at the window's edge with virtually no pull to almost lifting 75kgs in I'd guess a 15 or so kph wind.  That's the 1.5 sq m, so don't give it to children in anything over a light breeze. The wind window decreases much less than the npw as the wind increases. This is probably due to the kite shape not getting as distorted as the npw and the result is a smaller decrease in lift to drag ratio. This is a challenging kite to fly. It has a pretty steep learning curve but I think well worth it if you persevere. Part of the difficulty of flying it is due to the drag changing with speed (presumably the trailing edge has a greater influence when moving faster) and the result of this is that you need to adjust the angle of attack as it takes off and picks up speed. If you don't then it slows down again and the nose can collapse. The control with four lines is excellent and it is really manouverable. When the wind drops it will stay stalled much longer than the NPW and kind of float down which gives you plenty of time to manouver if the wind returns. The basic thing when learning to fly it is to keep your hands together out in front of you. It doesn't take much control input at all to turn it with the brake lines. Just change the angle of your handles and keep your hands together. Change the angle of attack by angling both handles forward or back together. You can also steer it by rotating both hands together as if it were a steering wheel. This makes a slow graceful turn whereas angling one handle to manipulate one brake line makes a much quicker turn. The biggest mistakes beginners make with this kite is that of moving the handles apart or making too big a change in handle angles. This results in the kite going into a spin which initially seems impossible to get out of. It is possible, however. Go back to the basic position of handles together at the same angle and the kite will stabilise. Don't worry about which direction it's pointing just get it stabilised first then try a smaller correction. It's good practice initially to just lift the kite off the ground in a steady wind then try to keep it under control without worrying about shooting off anywhere. You'll learn to control it with small movements which pays off when you come to really take off. Also examine the shape of the kite and see if the wing shape is smooth or if the bridle lines need a little adjusting. The kite needs to collect as much fill-air as possible and this is enhanced by a smooth outline with as small bumps in the wings as possible. This will keep it inflated best and help it's performance. The problem when going for a real take off comes as it picks up speed and the angle of attack needs changing. This is a fairly fine line between too much and too little. Get it right and the nose doesn't collapse. The other problem here is the distribution of pull between le and te flying lines. As it gets up speed I think the trailing edge contribution increases and in a higher wind the pull on the brake lines can increase to the point that it changes the angle at which you are holding the handles without you realising it. The angle changes and suddenly there's not enough brakes anymore. The pull on the brake lines decreases and the angle you're holding the handles at changes back resulting in more pull again and so on. The result is the kite flaps about, alternating between too much brakes and too little. The way out of this is to concentrate on holding the handles steady even when it's pulling like mad. The situation is aggravated of course by a higher wind, a gusty wind and a larger kite which has more pull. Finally, I hope the flying advice above doesn't put you off but serves instead to help you learn how to control it. I wouldn't recommend this kite if you haven't tried an NPW first (preferably with four lines) but if you have and want a bit more of a challenge then it certainly will give you that. Don't forget to send me a pic, if you can, for a map of the world with ESP flag pics stuck in it. Could be fun. Two line flying still untested. Last update - 20010810.

The biggest ESP mod 2 I've heard of to date is one made by a young man by name of Michael in Illinois. He was 14 when he made it and succeeded without any help whatsoever. He wrote to me a year later (been too busy having fun with it I guess) to send some pics. Here he is flying on a beach with his 100 sq. ft. esp, and inset, 100 sq.ft esp flying with him. He also uses it to skate on gravel with.
Stroll about, 100 sq ft that's around 9 sq m !