kite question

I built my first kite yesterday. I believe it is a form of Delta kite. It did fly but then it would spiral rapidly and crash to the ground. My kids are keen to get this thing airborne but I at a loss on how to fix this problem. The only thing I can think of is that the center of balance is off. Is the string attachment point the center of balance? Should I use tape? pennies? to correct any imbalance?

The problem that comes first to my mind is that you have the attachment point for the line too far back. Here is a page that shows where you should attach the bridal for the line:

Delta Kite Plans

Can you give us an image of the kite? Delta kites usually have significant keels to which one attaches the string; there’s usually no option of where to attach. Does yours have a big keel coming out of the bottom? If so, check the spars in the wings. they should both be pushed down as far to the end of the wing as they’ll go. There will be a gap between the spars on the wings and the tip of the kite, which is as it should be.

A description or photo of the kite would be helpful. Based on the behavior, it almost sounds like you’ve got a fighter kite, which is a completely different animal; however, they’re a lot more fun and easy to fly.

Please fill in the details.

Okay, the dime-store kites I flew as a kid weren’t nearly as nifty, but from what I remember(and it has been a long time) that was the reason we always attached a tail to our kites.

A note on tails:

A lot of people think the purpose of the tail is to weight the bottom of the kite so it stays pointing down.

A more important function is to add drag to the downwind point (which is also at the bottom) so that the top of the kite remains facing into the wind. A string with some paper bows along it weighs little, but adds a lot of drag, so makes an effective tail.

The keel on a typical delta kite does this. If the crossbar on your kite is fairly short, then the sail will form into a shape with lots of dihederal, which mimics the function of the keel. If your crossbar is long enough that the sail is tight, the you have a fairly flat wing, which needs a proper keel for stability.

The kite link from DAFFYDUCK above is the exact kite I built. I didn’t use fabric and sewing. It’s made from plastic sheeting and tape. The string is attached to the point of the keel.

Either change the shape of the keel so the nose keeps down more, or else give it a tail.

Okay, so you actually made it yourself? Right. Make sure the wing spars are not tight against the tip, they need some play. As Kevbo noted, the wings need to bend backward with the pressure of the wind, this creates the effective keel, because when it leans one way or the other, it exposes more surface to the wind and thus self-corrects.

Fighter kites work by being flat, so that they spin wildly when there isn’t a lot of wind pressing on them. When there is, the wings bend back creating the keel, and the kite shoots in the direction it’s pointing. To control one, you give it slack to make it spin and when it’s pointing in the direction you want, you start pulling it in to make it go. It sounds like your problem, rapid spiral into the ground, is what you get when a fighter kite is not under enough wind pressure to bend the wings back. So, you might try shortening up the crossbar to allow the kite to bend a bit more.

Now hold the kite by the spot where the string connects. Does it balance, more-or-less? If so, then weight distribution isn’t your problem. What is the angle of the kite relative to the ground? IIRC, it should be about 15º (with the nose higher than the rear — you want to get laminar flow over the back of the kite, so it should lean into the wind a bit), but it’s been a while, so I’m not sure. Anyway, take a step back and pull on the kite. It should essentially fly right there on the end of your hand for the moment you’re pulling. (Attach a foot of string for this if you like.) You can do most your diagnostics this way.

Just in case you don’t know, to launch a kite, you have someone hold it quite a distance down wind, and then pull it in, hand over hand, very quickly. It should shoot straight up. If you’re flying alone, stake the string into the ground, walk down wind and set the kite up, ass down and leaning away from the wind, so that the wind holds it in place, semi-erect on the ground. Walk back to the operator-end of the string and reel the string in hand over hand.

Hope that helps.