Date: Sat, 22 Jul 1995 16:53:06 -1000 From: fsiegel@linet02.li.net (Frank Siegel) Message-Id: <3usdii$2nj@linet02.li.net> Organization: LI Net (Long Island Network) Subject: Stacking I have been following the posts on rec.kites for some time, and have seen many references to stacking kites (mostly flexis for power). While I've ssen some discussions on radical moves with delta stacks- I'm kind of lost on the basics. To stack 2 kites of unequal size e.g. 6 & 8 ft- how long should the train lines be? Should the lines be equal in length, or do you want slightly longer top lines? What is the best way to attach the train lines to the front kite to prevent distortion of the lead kite? I'm guessing that the best way to make train lines is to sleeve a short length of Spectra- or is there a simpler, easier method? Finally, is the resultant pull about the same as the combined pull of the two, or does the front kite significantly reduce airflow to the back, resulting in less pull? Thanks in advance. (I might recommend that you post a response back to the rec.kite, as I'm sure many other flyers are either ignorant of stacking or not stacking optimally.) Frank = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 24 Jul 1995 09:41:19 -1000 From: jburka@Glue.umd.edu (Jeffrey C. Burka) Message-Id: <3v0t0v$a8b@geog12.umd.edu> Organization: Project Glue, University of Maryland, College Park Subject: Re: Stacking In article <3usdii$2nj@linet02.li.net>, Frank Siegel wrote: > To stack 2 kites of unequal size e.g. 6 & 8 ft- how long should the >train lines be? Typically, six or so feet should be fine if you're stacking a 3/4 and a full size. Some of the common rules of thumb are to use about 2/3 of the wing span or the length of the leading edge. >Should the lines be equal in length, or do you want >slightly longer top lines? Usually if you're stacking just 2 kites you can make all lines equal. If you've got a big stack, pull in the top of the last kite or two to help keep things locked. >What is the best way to attach the train lines >to the front kite to prevent distortion of the lead kite? Make a set of 10 equal-length overhand loops (5 for each kite) and larkshead them around the vinyl/spar where the bridles are connected. It's fairly common to see phantom frames used for big stacks of diamond kites (these are triangles formed out of stiff tubing; the bridle is attached to the phantom frame and the frame is then connected to the lead kite by train lines), but I've never seen anything like a phantom frame used for deltas. If you're going to be stacking a lot of kites, beef up the frame in the lead kite. > I'm guessing that the best way to make train lines is to sleeve a >short length of Spectra- or is there a simpler, easier method? Don't both sleeving the spectra, if that's what you use. Think about it this way -- if you usually fly a kite on 80 pound lines, then the pull is distributed over 2 lines. If the kite is stacked, that same basic pull is distributed over 5 lines, so you could get away with a much lighter line. You can use all sorts of things for train lines -- dacron, old skybond (my favorite use for all those lines I bought back before Spiderline hit the market), whatever. > Finally, is the resultant pull about the same as the combined pull of >the two, or does the front kite significantly reduce airflow to the back, >resulting in less pull? The stack usually won't pull as hard as the individual kites combined, for a variety of reasons. For instance, the stack will usually fly a bit slower. Jeff -- |Jeffrey C. Burka | Pithy, insightful quote to be inserted when one | |jburka@glue.umd.edu | occurs to me. *If* one occurs to me. | |http://www.wam.umd.edu/~jeffy/html/home.html | = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 24 Jul 1995 09:41:19 -1000 From: jburka@Glue.umd.edu (Jeffrey C. Burka) Message-Id: <3v0t0v$a8b@geog12.umd.edu> Organization: Project Glue, University of Maryland, College Park Subject: Re: Stacking In article <3usdii$2nj@linet02.li.net>, Frank Siegel wrote: > To stack 2 kites of unequal size e.g. 6 & 8 ft- how long should the >train lines be? Typically, six or so feet should be fine if you're stacking a 3/4 and a full size. Some of the common rules of thumb are to use about 2/3 of the wing span or the length of the leading edge. >Should the lines be equal in length, or do you want >slightly longer top lines? Usually if you're stacking just 2 kites you can make all lines equal. If you've got a big stack, pull in the top of the last kite or two to help keep things locked. >What is the best way to attach the train lines >to the front kite to prevent distortion of the lead kite? Make a set of 10 equal-length overhand loops (5 for each kite) and larkshead them around the vinyl/spar where the bridles are connected. It's fairly common to see phantom frames used for big stacks of diamond kites (these are triangles formed out of stiff tubing; the bridle is attached to the phantom frame and the frame is then connected to the lead kite by train lines), but I've never seen anything like a phantom frame used for deltas. If you're going to be stacking a lot of kites, beef up the frame in the lead kite. > I'm guessing that the best way to make train lines is to sleeve a >short length of Spectra- or is there a simpler, easier method? Don't both sleeving the spectra, if that's what you use. Think about it this way -- if you usually fly a kite on 80 pound lines, then the pull is distributed over 2 lines. If the kite is stacked, that same basic pull is distributed over 5 lines, so you could get away with a much lighter line. You can use all sorts of things for train lines -- dacron, old skybond (my favorite use for all those lines I bought back before Spiderline hit the market), whatever. > Finally, is the resultant pull about the same as the combined pull of >the two, or does the front kite significantly reduce airflow to the back, >resulting in less pull? The stack usually won't pull as hard as the individual kites combined, for a variety of reasons. For instance, the stack will usually fly a bit slower. Jeff -- |Jeffrey C. Burka | Pithy, insightful quote to be inserted when one | |jburka@glue.umd.edu | occurs to me. *If* one occurs to me. | |http://www.wam.umd.edu/~jeffy/html/home.html | = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Jul 1995 01:56:47 -1000 From: Chuck.van.Eekelen@net-engine.nl (Chuck van Eekelen) Message-Id: Organization: NLnet Subject: Re: Stacking fsiegel@newshost.li.net (Frank Siegel) wrote: >I have been following the posts on rec.kites for some time, and have seen >many references to stacking kites (mostly flexis for power). While I've >ssen some discussions on radical moves with delta stacks- I'm kind of >lost on the basics. > To stack 2 kites of unequal size e.g. 6 & 8 ft- how long should the >train lines be? Should the lines be equal in length, or do you want >slightly longer top lines? I fly my 6 and 8,6 flexi's on a 6 - 8 foot line (variable). It's my humble experience that the "rule" that says your trainlines should be two-thirds the length of the preceding kite doesn't apply here. Because of the rather large difference (over 2,5 ft) in span between the two kites, I got the idea that the spar-ends of the 6'-er were being pull outward thus preventing the frontkite to achieve its optimal arched form. >What is the best way to attach the train lines >to the front kite to prevent distortion of the lead kite? > I'm guessing that the best way to make train lines is to sleeve a >short length of Spectra- or is there a simpler, easier method? I've used Dynacord/Skybond with knots where I connect the control-lines ( about 2 feet in front of the frontkite) and marks at the point where the trailing kites should be attached. The line thickness is a little bit thicker than equivalent strength spectra/dyneema, but it saves you the process of sleeving and it's easier to vary the distance between two or more kites. I'm not sure who much the drag created is a bother, I haven't tried flying the stack with dyneema/spectra lines yet. > Finally, is the resultant pull about the same as the combined pull of >the two, or does the front kite significantly reduce airflow to the back, >resulting in less pull? According to Nop Velthuizen in Stuntkites II, the combined pull would be close to the individual pull's added up. >Thanks in advance. (I might recommend that you post a response back to >the rec.kite, as I'm sure many other flyers are either ignorant of >stacking or not stacking optimally.) >Frank Your right, I myself am interested in other opinions especially on the issue of line-material. Chuck Hang 'm high! = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Jul 1995 11:14:26 -1000 From: doyle@gdc.com (Sean Doyle) Message-Id: <9507252114.AA07923@mailhost.gdc.com> Organization: Harvard University Office of Information Technology Subject: Re: Stacking I fly Dyna-Kites which are diamond shaped and have no cross-spar therefore some of the things that I do are not applicable for others. > how long should the train lines be? Should the lines be equal in > length, or do you want slightly longer top lines? LINE LENGTH We use 3' (3 foot) and on some stacks 4' interkitelines (train lines). Our leading edge is about 3' long. There is a noticable difference in stack harmonics with the longer length lines but the stack flies about as well with either length. By harmonics I mean creating wave with the kites happens at a frequency of left and right turns. The reason we choose 3' is for competition or for small flying fields. The purpose of 4' is to spread out the stack and make it more impressive in the sky. Hardware Hank's stack is 25 kites x 4' which is about 100' with 100' long tails. Its very impressive. When field size permits we fly these large stacks on 200+' flying lines. As you can imagine 100' of kites would look kind of silly flying on 80' of line. EQUAL LENGTHS? The diameter of the Dyna-Kite keel has been made a fraction of an inch larger than that of the leading edge. By using equal length interkitelines the distance between the keels of adjacent kites will be slightly smaller than the distance between the leading edges because more of the keel line is used going around the spar at each end. The difference is slight but I believe it adds up to about an inch and a half (or more I can't remember) for 12 kites. Using this fact, we briddle the kites to lean the lead kites into the wind more so they get a bit less pull but, because the keel line is 1.5" shorter, the back kites will face the wind providing more pull. This helps the kites to track better because the back kites have more pull and keep the front kites in line. Before changing the Dyna-Kite design (the keel diameter) we shorten the keel line on the 2nd to last kite by about 2 inches (this is for a 12 pack.) The thing to watch out for is the back kites leading too much, especially on turns. If this happens you have shortened the keel line too much. > What is the best way to attach the train lines > to the front kite to prevent distortion of the lead kite? USING A PHANTOM We use a 'phantom' as mentioned in another posting. The phantom keeps the flying lines where they would be if there was only a single kite being flown (the name 'phantom' is used because it takes the place of a lead kite.) By stacking kites we increase the pull and because we have no crosspar the lead kite would collapse without support. Dyna-Kites are designed to collapse (somewhat) as the wind increases so we don't stiffen the kite we just keep the flying lines out where they belong. LINE MATERIAL We use spectra or kevlar for interkitelines. Be careful that all your lines between any 2 kites are equal. If using line which stretches be careful that it all stretches evenly. > Finally, is the resultant pull about the same as the combined pull of > the two, or does the front kite significantly reduce airflow to the back, > resulting in less pull? >From my experience, I would say its pretty much the combined force. Sean Doyle DK Breezin = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Jul 1995 02:21:57 -1000 From: mabrow@most.magec.com (Matt Brown) Message-Id: Organization: Magnavox Subject: Re: Stacking In article <3v0t0v$a8b@geog12.umd.edu>, jburka@Glue.umd.edu (Jeffrey C. Burka) wrote: > : To stack 2 kites of unequal size e.g. 6 & 8 ft- how long should the > :train lines be? > > Typically, six or so feet should be fine if you're stacking a 3/4 and a full > size. Some of the common rules of thumb are to use about 2/3 of the wing > span or the length of the leading edge. I fly a 6 & 8 ft stack of two kites and used this rule of thumb successfully. It did require quite a bit of "tweaking" to get them to track together. Final lenght is just a little more than 6 ft., but your performance may vary depending on the flying characteristics of the two kites. > :What is the best way to attach the train lines > :to the front kite to prevent distortion of the lead kite? > > Make a set of 10 equal-length overhand loops (5 for each kite) and > larkshead them around the vinyl/spar where the bridles are connected. It's This is how I did it and it works great! It's quick and easy, and you can just leave the loops on the kites all the time. I used 150 lb dacron for my train lines; probably overkill but that's what I had handy. > > Finally, is the resultant pull about the same as the combined pull of > >the two, or does the front kite significantly reduce airflow to the back, > >resulting in less pull? > > The stack usually won't pull as hard as the individual kites combined, for > a variety of reasons. For instance, the stack will usually fly a bit > slower. My stack pulls considerably harder than either of the individual kites, but I don't think it pulls as hard as the two added together. BTW, the first time I flew the stack in a moderate wind I broke the bridle on my 6 ft kite. I don't think it was ready for the extra pull. I didn't have "good" measurements of the bridle and it took a while to re-bridle the kite (with heavier line) so it flew satifactorily again. <<< Moral of the story: Make sure you have measurements of your bridles and spars in case they break and you have to replace them.>>> Seems kind of obvious now, but in the hurry to fly that new kite it's pretty easy to skip. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Jul 1995 06:24:08 -1000 From: irving@sys.toronto.edu (Irving Reid) Message-Id: <1995Jul25.122408.16407@jarvis.cs.toronto.edu> Subject: Re: Stacking jburka@Glue.umd.edu (Jeffrey C. Burka) writes: >Usually if you're stacking just 2 kites you can make all lines equal. If >you've got a big stack, pull in the top of the last kite or two to help >keep things locked. I'm not sure if this is a slip, unfamiliar terms, or a change in conventional wisdom, but usually the train lines to the top of the last kite or two are longer, so the nose is farther back. I'm used to hearing this described as "pushing out" to top of the kite, but I could be terminologically confused. - irving - = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Jul 1995 10:40:50 -1000 From: jburka@Glue.umd.edu (Jeffrey C. Burka) Message-Id: <3v3ksi$fvk@geog25.umd.edu> Organization: Project Glue, University of Maryland, College Park Subject: Re: Stacking In article <1995Jul25.122408.16407@jarvis.cs.toronto.edu>, Irving Reid wrote: >jburka@Glue.umd.edu (Jeffrey C. Burka) writes: > >>Usually if you're stacking just 2 kites you can make all lines equal. If >>you've got a big stack, pull in the top of the last kite or two to help >>keep things locked. > >I'm not sure if this is a slip, unfamiliar terms, or a change in >conventional wisdom, but usually the train lines to the top of the >last kite or two are longer, so the nose is farther back. Whoops! Good call. I should have said "drop back the top of the last kite or two". Sorry if I confused anyone else. Incidentally, there *is* another way to stack deltas, which involves building a sort of reverse bridle on the back of the lead kite. The rear kite is then attached via its own bridle pick points. This arrangement is not nearly as stable, but it's something fun to play with if you're looking for some new excitement. Jeff -- |Jeffrey C. Burka | Pithy, insightful quote to be inserted when one | |jburka@glue.umd.edu | occurs to me. *If* one occurs to me. | |http://www.wam.umd.edu/~jeffy/html/home.html | = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 26 Jul 1995 02:41:02 -1000 From: doyle@gdc.com (Sean Doyle) Message-Id: <9507261241.AA08000@mailhost.gdc.com> Organization: Harvard University Office of Information Technology Subject: Re: Stacking Jeffrey C. Burka writes: > >Usually if you're stacking just 2 kites you can make all lines equal. If > >you've got a big stack, pull in the top of the last kite or two to help > >keep things locked. > Irving Reid writes: > I'm not sure if this is a slip, unfamiliar terms, or a change in > conventional wisdom, but usually the train lines to the top of the > last kite or two are longer, so the nose is farther back. I'm used > to hearing this described as "pushing out" to top of the kite, but > I could be terminologically confused. > I agree with Irving. For our kites, pushing out the trailing kites works better. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 26 Jul 1995 13:02:13 -1000 From: jcampbell3@msmail3.hac.com (Campbell, James E) Message-Id: Organization: HAC Subject: Re: Stacking In article <1995Jul25.122408.16407@jarvis.cs.toronto.edu>, irving@sys.toronto.edu (Irving Reid) wrote: > jburka@Glue.umd.edu (Jeffrey C. Burka) writes: > > >Usually if you're stacking just 2 kites you can make all lines equal. If > >you've got a big stack, pull in the top of the last kite or two to help > >keep things locked. > > I'm not sure if this is a slip, unfamiliar terms, or a change in > conventional wisdom, but usually the train lines to the top of the > last kite or two are longer, so the nose is farther back. I'm used > to hearing this described as "pushing out" to top of the kite, but > I could be terminologically confused. > > - irving - Agreed, the last kite(s) in a long stack need to lean back just slightly compared with the kites in the front of the stack. The purpose is to increase the pull on the back of the stack which helps keep the stack "locked". The decrease in attack angle is a function of the profile of the kites used in the stack. In order to find this angle on new stacks, I've used sheet bend knots on the train lines of the last kites so I could quickly adjust line lengths. Once the length has been found, I replace the test train line with a traditional train line of the appropriate length. BTW, I only use the sheet bend knots for testing in light wind conditions. Good luck with your stack. -- James E. Campbell (jcampbell3@msmail3.hac.com) Hughes Aircraft Company Leading Edge Kites = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 27 Jul 1995 00:56:30 -1000 From: gaffer@pat.rec.com (Andrew Beattie) Message-Id: <806842590.28379@pat.rec.com> Organization: I need to put my ORGANIZATION here. Subject: Re: Stacking Jeffrey C. Burka wrote: >Whoops! Good call. I should have said "drop back the top of the last kite >or two". Sorry if I confused anyone else. I'm sorry Jeff. I still don't get it. How do I get the last flexi to drop back? Andrew = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =