Jump to content

- - - - -

Issue 9 (May/Jun 1999): BORK - Building

archive rec.kites kite making

  • Please log in to reply
No replies to this topic

#1 Mike Gillard (RIP)

Mike Gillard (RIP)


  • Staff
  • PipPipPip
  • 190 posts
  • Gender:Male
  • Country:United States

Posted 01 June 1999 - 04:00 AM

This page is a summary of postings on the rec.kites Usenet usegroup that our editors believe to be interesting and useful. Opinions expressed in these postings are not those of KiteLife Magazine or its staff.

Once again I'm indebted to the faithful BORK staff:
  • Craig Rodgerson
  • Peter C. Hugger Editor
Building Contents:
  • Reframing rev with UL spars
  • Using 3M 9460 tape in kite making
  • Traction Kite Tech 5
  • Glue
  • Ropemaking for Chinese Flute Kite Trailing Lines
  • Inkjet on fabric, not ripstop
  • Size and material for 1st traction foil
  • Ripstop 3/4 vs. Icky PC31
  • Velcro closures on Foils
  • Getting started making comp. kites
  • Sleeving material
  • Bamboo Sources in the US for Kites
  • Scaling up
  • Quadlining a Rokkaku
  • Original Plans Nasa Para Wing
  • Bol Design Software
Reframing rev with UL spars

A couple of weeks ago, I was asking for recommendations for reframing a rev for zero-wind use.

Well, I've now done this -- ingredients are:

1: Rev 1.5 SLE. 2: 1 Skyshark 2P spar. 3: 4 Skyshark 2PT spars. 4: 6" or so of .2100 spar. 5: (optional) 4 .2000 endcaps.

Recipe: Remove original spars. Cut the 2P spar to the same length as the original central spar. Cut two of the 2PT spars to the same lengths as the outer leading edge spars and two of them to the same length as the vertical spars. (okay, this is obvious..)

Put end caps on the lower ends of the vertical spars and outer ends of the leading edge spars. This is optional; however, Dan Whitney (and possibly other people -- I got these from Gone With the Wind, though) sells some nice rigid (blue) end-caps that fit very nicely _inside_ the original SLE end caps and outside the narrow end of a 2PT spar. Putting the wide end of the 2PTs as the top of the vertical spars winds up with them fitting pretty nicely into the original SLE fittings -- not quite as snugly as the originals, but not loosely enough to be a problem. Shrinkwrap would solve this, I guess.

Ferruling the leading edge is interesting; the ID of a 2PT at the wide end is .2330, but the ID of a 2P is .2100. Taking a bit of 2100 spar and sanding it down a tiny amount means it fits _extremely_ snugly inside the 2P (no glue needed -- it's not going anywhere any time soon. You may not need to sand it down if you're prepared to push hard enough to get it in; however, sanding it a tiny amount removes the odd thousandth of an inch to make this less forceful). .2100 spars fit a little bit loosely inside the 2PT, but the bungy cord at the ends of the leading edge that the Rev uses holds everything together nicely).

I left the bridle and all the original fittings in place; the idea is that if the wind goes away, I put in the UL spars, and if the wind picks up, I can put the original spars back with the minimum amount of fiddling around.

Total weight of this with new spars is about 150-160g. Removing the bridle and using smaller lighter fittings would trim this down another ounce or so, I'd guess. However, I don't see any need to do this -- flying in zero wind, I was pleasantly surprised by how well it flew. The leading edge tends to flex quite a lot when yanked on too vigorously, but that was mainly when I got caught by a gust of wind when launching -- in normal flying it had no problems, and seems perfectly robust enough to not break when crashed. (I tested this.. It didn't break).

I'm not sure exactly how much effort this needs compared to custom-built SUL Revs, because I'm still getting the hang of it -- however, it certainly took less effort than my first dual-line no-wind efforts did. This may be as much a comment on my ability to work out what to do with no wind as the kite, of course.

Flying revs in zero wind is a _lot_ of fun.. I highly recommend this to anyone who's not tried it yet -- doing this as above requires no skill or fiddling around except for a bit of sawing spars down to size, and 2PT spars are surprisingly cheap for how good they are; total cost for the above is about $40-45 or so.

Next step, I suppose, is making extended handles, learning 3-d flying, trying it with no bridle, etc, etc.
-- dan


Hi Dan, hi folks.

Way to go Dan. Excellent ideas. What could be done to have a better fit between the .2100 and the 2PT is to increase the diameter of the .2100. I did so with some kites a while back by the following method:

1 - Spread three or four narrow lines of cyanoacrylate glue on the exposed part of the .2100 spar. These lines should be colinear with the spar and evenly spaced around (3 at 120 degrees or 4 at 90 degrees).

2 - Let dry completely.

3 - Sand to obtain a sliding fit.

That way you avoid a loose fit that may provoque spar failure.

Note that if you refrain flying in too much wind this precaution is not really necessary.

Wind or no wind, fly for fun :-)
Jean (Johnny) Lemire

Using 3M 9460 tape in kite making

After extensive experimentation and successful usage of 3M 9460 two-sided tape in kite making, I've added a page to my web site about it.


Perhaps some of you might find it helpful.
Steve Rezac

Traction Kite Tech 5

Hi all,
I just added a page about my latest line of development for traction kites. It's sort of a form of reefing, but with a different goal. Check it out on my page, and let me know what you think...it's in development, and brainstorming is welcome.

Check out http://www.digitalfidelity.com/kites

Enjoy! Gene Matocha


> Hi all,
> I am looking for a strong 'flexible' type (that is, not brittle) glue.
> Would like to bond Icarex to Icarex, and Icarex to carbon
> rods/shafts. Does anyone have any recommendations on
> glues to use.
> Thanks,
> Shane.


Should think that a contact adhesive (a rubber solution) would do it. Clean thoroughly first with spirit and maybe roughen the rod surfaces a little with a fine sandpaper.

If you can't glue it, nail it. If you can't nail it, screw it.

Ropemaking for Chinese Flute Kite Trailing Lines

Made a new page about ropemaking from natural fibres for the trailing lines Chinese Nantong Whistle Kite. Would need your comments/ criticism etc. Address:
Thanks for your efforts
Uli Wahl

Inkjet on fabric, not ripstop

Found this on rec.crafts.textiles - may be of interest...


Size and material for 1st traction foil

Well, I've finally got my Sands Traction Kite Plans and I am going to go ahead and make myself a soft foil or two. However, I have two questions to start with.

1. What should I make the first kite from? I have some P31 iccy, and I may be able to get some P38 also. My initial thought is that I would make the ribs from ripstop nylon (because it is cheap and is less likely to tear) and then make the shell from iccy. Does this make sense?

Bear in mind that I intend to take the kite on holiday with me next month, so the chances are that it will get dumped into the sea a large number of times...

2. Any ideas what would be a sensible size to start with? I am assuming that the winds I'll experience while on holiday will be fair, but not ballistic and with the possibility of low wind.

Chris Sands gives detailed instructions on how to build the 3m^2 (or is it 3.5m^2) so my guess is that he thinks that this is a good size to be starting with. Would this be in line with your (collective) thinking?



I would say: go for icy P38. Nylon will get wet and eats water like hell. Icy doesn't. P31 is probably a bit to light for a 3.5m^2, the tension will get to much if you 'go wild'.

Another real advantage of icy is the way it keeps your foil in shape when it's on the ground, like it's inflated. This means: better control, better recovery from collapses and beter launching. Down side is that it just wants to fly, landing needs special attention.

have fun,

Ripstop 3/4 vs. Icky PC31

Hi all,
SBBB convinced me I need to make smaller, stronger kites for high desert winds. All of my kites so far have been in PC-31 or P-31. I ordered a color sample of 3/4 oz. nylon, thinking it would be more durable, but it doesn't seem that much stronger. It could be that the samples are very small so I can't get a realistic sense of the fabric weight. I know the PC-31 claims to be as strong as 3/4 Icky (P-38), but I am looking for abrasion resistance as well as tear strength. I'm making a 3.7m^2 and a 2m^2 kite. I was thinking PC-31 for the 3.7, and 3/4oz nylon for 2m^2. Should I go for something stronger? I haven't yet found a US source for some of the other new (European?) fabrics, like Carrington, Chikara (sp?) etc.
Thanks, Gene Matocha


G'day Gene,
Most of my power/traction kiting is done in stronger winds and consequently, I tend to make smaller kites (Buggying with a 1.8m2 in over 30knots on short lines the day before yesterday! Yaahoooo!!!). I have only ever used ripstop nylon (Carrington K42, Bainbridge Dragon, Dimension and whatever else my undiscerning hands can grab), mostly because of the expense and unavailability of ripstop Polyester (Icarex) locally. I have found that nylon is good in terms of durability to everything other than U.V. exposure. I've done a reasonable amount of rollerkiting with my kites and have had them in contact with ashphalt without any real abrasion problems. Nylon is good for parafoils in that it has more stretch than polyester and consequently is less susceptible to bursting or ripping. The downside is that stretch is less desirable for aerodynamic reasons - although it may, overall, be slightly less important that we think IMO. I have used 3/4 oz. without problems on kites up to around 5m2. I haven't made any kites from Chikara but will probably do so soon as I can lay my hands on some. It is apparently inexpensive, has double sided coating (hydrophobic) and seems to last (friends with C-Quads made in it are not having problems after a fair bit of use). I have also heard about the new Skytex Porche Marine (impregnated) nylon. This sounds VERY good and probably can beat anything else for water resistance. I would love to get my hands on this for my amphibious parafoil project. Good luck with your new kites, Gene!
Smooth Winds,


> We were talking kites, and they asked if we use
> Spectra fabric. I hadn't heard of this, does anyone know if it
> exists in a kite-usable form?
> Enjoy!
> Gene >

There is a rip-stop polyester with Spectra reinforcement. Construction is similar yo .6 oz polyester, with double lines of Spectra in place of the larger denier polyester fiber of the rip-stop. It is further reinforced with 1/4 or 1/2 mil polyester film (Mylar). final weight is about 1.25 -1.5 oz depending on film thickness. This was originally made for Whitbread offshore racing spinakers. It is obscenely expensive (try 2x icarex), and the supply is exhausted. There is the possibility that it will be milled again depending on the course layout for the America's cup races. I made a modified Hagaman 80 with this for University of Colorado researchers, who needed a kite that would work in winds in excess of 50 knts. They hope to fly this kite to record altitudes of 35,000 ft this summer. Oh, one other thing, it's only available in white. The stuff is bullet-proof, but is probably overkill for most kite applications.
Stan Swanson, Condor Kite Co.

Velcro closures on Foils

Hi traction kiters,
Reading Jean Lemire's idea about using velcro sections in a traction kite to "blow out" instead of the cells raised this thought: how about lengths of velcro in the trailing edge hem?

Instead of sewing the whole hem shut, have sections fastened with velcro. I'm not certain this would help, as the failures I've seen were in the risers, the stress at the trailing edge is probably lesser, as the crash tends to balloon the cells outward.

Just a thought...


Been there...done that. My first Sputnik has sections of velco along the TE. I posted about this (after completion) and was informed that Peter Lynn had tried the exact same thing...and then did something I won't - he deliberatly "poped" some Peels to see if it'd work. It didn't.

The velcro does, however, provide a nice drag-free way to attach the tow-points when you pack the kite - open up a few cm, tuck in the end, and close it. Very handy. other possible benefits: - read Andrews experience w/ zippered TE and it's effects on luffing. - Easy to get sand out. ....not that these are a huge deal or anything. I don't use velcro in the TE anymore.

Enjoy! Gene Matocha

Getting started making comp. kites

> I would like to start making kites so hopefully be able to make a
> traction one. Are there any good sites, books, etc. to help get
> started? More then just the plans but how to do the sewing, like
> making the pockets for the spars, etc? Any help would be greatly
> appreciated.
> Jim

Get the books... Stunt Kites and Stunt Kites 2 by Nop Velthuizen and some other guy (sorry, too lazy to get up and check)

Go to Andrew Beatties page (there's a link on my page) and read the Chevron construction article. In fact, print it out, it's a great reference. I swear, every time I start sewing ribs, I have to go back and check "now, which side does the seam allowance go on?" :)

Then start following links...and you are off!
my page is: http://www.digitalfidelity.com/kites
Enjoy! Gene Matocha

Sleeving material

> Would someone tell me what material Sleeving is made of?
> I have several different sizes of braided dacron for my single
> line kites, and was wondering if the larger ones (#150 & up)
> would make suitable sleeving for Spectra or Kevlar (yea, I still
> have some of that stuff, but I don't use it unless I'm all alone.)
> on my stunters.
>Many thanks,

Hi Jerry, Yup heavier braided dacron line works great for sleeving on spectra. I use 80# dacron for my lighter lines50#, 60#, 150# for my 80 to 100# lines, works just fine and I get both black and white so I make sets that are color coded so to speek.

Bamboo Sources in the US for Kites

> I am planning to build a kite the 'old-fashioned' way with
> bamboo. Are there any bamboo sources in the US that I
> can purchaes from? I live in Minneapolis and there does
> not seem to be any around here.

I am sure I have seen an occaisonal posting of an URL for a bamboo lovers group...try putting it into a search engine...... Here in Australia I find that plant nurseries / gardening sections in discount department stores carry bamboo tomato stakes in lengths from 2 ft up to 6 feet......they make great spars and can be split....... I know that Elain Genser from Canada uses similar bamboo poles for ground displays....so I assume they can be purchased reasonably locally and cheaply.......


When we were at Long Beach in August one of the Kite makers told me that he took apart old bamboo window screens for his. (He would look for them in shops with caried products from Japan.)
Paul Manning


A good source for bamboo is Aligator Alley in Oklahoma City... They have bamboo poles that are about 1.5 inch's in diameter and about 6~7 feet long... These can be split for smaller bamboo rods... They would make a very nice Rok or Cody. Sorry don't have the phone number but iformation will have it... I think the area code is 405...
later :-)


saved an article by Bob Harris that names bamboo suppliers around the US.


There have been a lot of discussion about bamboo in the past on rec.kites Check into the DejaNews complete archives using 'rec.kites bamboo' as the search terms.


Just tried it out and from the main page you only get a couple from the last two months. But down at the bottom of the results page there's a button to selet "Past" archives. Pick that then run the search again. It does not appear on the Power Search page. Gets about 100 articles from the last couple years.
-- Brian Johnsen



On a couple of occaisions I have attempted to locate sources for bamboo for use in kite making, psrticularly for traditional Asian kites. The results of these searches are compiled below. (Note: I have not contacted all of the sources listed, so some may be out of date or not appropriate.) I hope this will be of some help to the kiting community, and, perhaps, save you some search time.

I- Sources:

I-A- Canes:

I-A-1- Tonkin:

Tonkin cane is regarded as the premier cane for building split bamboo flyrods, an application that is far more demanding than the building of kites. Thus, the prices for Tonkin can be expected to be higher than for other varieties.

Charles H. Demarest, Inc. PO Box 238 Bloomingdale, NJ 07403 phone: 201-492-1414 fax: 201-838-6538 e-mail: <76116.2065@compuserve.com contact: Frank Demarest Canes are available in 12' lengths and in diameters ranging from 1 1/2 to 2 1/2 inches. Prices, F.O.B. NJ, range from $19.50 to $29.00 per piece depending on diameter, with a minimum order of 3 pieces. Canes may be cut in half and shipped UPS for an additional packing and shipping charge.

Searching the Web sites of bamboo flyrod manufacturers might yield some sources. For instance, Orvis claims that only 20 to 30% of the cane they purchase ends up meeting their quality standards. They must do something with the rejected cane.

I-A-2 other cane

Frank's Cane & Rush Supply 7252 Heil Ave. Huntington Beach, CA 92647 714-847-0919

A super source, with very reasonable prices. Canes are available in diameters from 1/4" to 6" and in lengths from 2' to 12'. Prices vary according to diameter and length, e.g., 1/4"x2' = $.70, 2"x6' = $7.10, 6"x12" = $60.00. Black and "Turtle" bamboo also available.

Bamboo Fencer 31 Germania St. Jamaica Plain, MA 02130 617-524-6137 617-524-6100 fax Fences, gates, bamboo constructions, poles; wholesale and retail, will ship anywhere.

Bamboo People 322 North 82nd St. Seattle, WA 98103 206-781-1437 Consults and designs bamboo plantings on farms and acreage nationwide. Brokers bamboo shoots and poles in Western Washington. Non-profit corporation

Bamboo & Rattan Works 470 Oberlin Ave. S. Lakewood, NJ 08701 908-370-0220 908-905-8386 fax 800-4-BAMBOO Custom bamboo fencing, gates, poles, rattan & other related items. Wholesale & retail; will ship worldwide.

Progress Trading 2301 Tomich Road Hacienda Hts., CA 91745 818-913-2888 818-965-6774 fax Bamboo poles imported from Guangdong Province, China. Minimum order is one bale (about $50 to $100).

Import stores, such as Pier 1, frequently stock 8' lengths for less than $10 per cane. This is where I obtained my current supply. The diameters seem to be limited to about 1 1/2 inches.

I-A-3 miscellaneous

Most garden supply stores stock bamboo stakes. The good news is they are cheap. The bad news is they are thin with closely spaced nodes. When quartered, the split pieces, obviously, are not very large.

A far out possibility is local landscape services. If they ever thin bamboo plantings for clients, they might be persuaded to set some aside.

Though of no help if your need is immediate, bamboo is easy to grow in most of our climate zones. I have some planted but have not harvested any yet. I have had the best luck with Japanese Arrow, a vigorous grower with 1 to 2 inch canes. Golden Bamboo, the most commonly available variety, looks as if it won't be good for much more than garden stakes.

I-B- Split Bamboo

I-B-1- bamboo suppliers

Frank's Cane & Rush Supply 7252 Heil Ave. Huntington Beach, CA 92647 714-847-0919

Any of the canes they supply can be split for a nominal splitting charge. 2' x 1/4" square or round sticks are stocked at $.10 ea. or $5.00 for a hundred. Also available are cut sticks (no taper) in 3 or 6 foot lengths, 1/2 to 1 1/2 widths ( 1/2"x6' = $1.05).

The Chinese Kite Shop (541) 446-7326 kite@bbsi.net www.bbsi.net/kite contact: Viviane

Has contacts in China. May be able to procure pre-split pieces. (Nice selection of traditional Chinese kites.)

I-B-2- flyrod makers

Have queried a couple with no luck. Still, a net search might produce something.

I-B-3- import stores

I keep hearing about those bamboo shades. All I have been able to find are reed shades.

II- Tools

II-A- Splitting

The ideal tool for splitting bamboo has a hard sharp edge beveled on both sides and tapered to a thick back to relieve pressure on the edge and to act as a wedge. With such a tool, splitting the cane is a surprisingly easy task.

II-A-1- bamboo splitters

Japanese tools with radial spokes encased in a ring with handles. 3-way to 8-way splitters are available from Frank's Cane & Rush Supply (714-847-0707). Prices range from $20.25 to $40.25.

II-A-2- bamboo froe

This is a carpenters tool specifically designed for the task and which has been in use for centuries. Bamboo froes are available from "The Japan Woodworker", 1731 Clement Ave., Alameda, CA 94501 (800-537-7820) for $21.95. (As an aside, anyone with an interest in fine woodworking and woodcarving hand tools will find their catalog is the world's greatest wishbook.)

II-A-3- knives

A bamboo froe or a splitter is on my wish list. For the time being, I get good results from an old knife with a hefty 6" hand forged high carbon steel blade sharpened to a razor edge. A thin bladed knife is not recommeded. I have seen references to the Opinel folding knife in the rec.kites archives. Two things about this knife: it comes in different sizes and some use stainless steel blades. This is a good old-fashioned working knife, but you would want the largest model with a high carbon steel blade. The Opinel is available from "The Smoky Mountain Knife Works" (800-251-9306) and from "Woodcraft" (800-225-1153) for about $10.

II-B- Shaving

II-B-1- knives

Bamboo is quite abrasive. Using a good knife, with a finely honed edge, as a scraper is a crime (at least from the perspective of a woodcarver). That finely honed edge will be destroyed in short order. There are better alternatives available.

II-B-2- scrapers

Sears carries a UK made two blade scraper for under $10. Sandvik carbide blade scrapers are available from The Japan Woodworker and from Woodcraft for just a little more. These work better than a knife and will save a good knife from unwarrented abuse.

II-B-3- block planes

These work much faster and better than a scraper. The flat sole of the plane keeps the tool from digging in and running with the grain. Inexpensive ($15 - $20) block planes are available from building material and hardware stores. Trimming and tapering a stick to size goes very quickly with a plane.

II-B-4- shaving planes

Probably overkill for this application. These are used in making bamboo flyrods. They range in price from $70 to $150. If you absolutely have to have the very best, they are available from The Japan Woodworker and from Woodcraft.

I hope this post proves useful. If you have information on other sources, you can e-mail that information to me at chrisl@oregon.uoregon.edu. If enough additional information comes in, I will include it and repost at several month intervals.

Kia Orana,
Chris Luneski

Scaling up

Hi there one and all, I have a kite I made as a test object and now I want to scale it up by a linear factor of 2. This will quadruple the area. Can I then assume that in the same wind range the forces will be quadrupled too? If this is so then can I also quadruple the area of the rods or alternatively quadruple the stiffness?

Nasa winging today, they don't bounce off trees. 3Ding as well today, not in the same wind I might add. It is fun. Guess what, it bounces off trees But I wouldn't recommend it


Hi Tel, hi folks.
This simple question can lead to a very complex answer. Just to give you a taste of it see what follow. Otherwise, bye and go fly a kite :-)

I would guess that yes, the forces will be quadrupled. Then for the spars, you must factor the stresses they will be subjected to.

A spar may be subjected to tension or compression, plus flexion, plus torsion.

For example, a greater bending force will tend to flex a spar more, unless you increase the spar resistance to bending. The amount of flexion and the stress involved here depends on the bending moment and the moment of inertia of the spar.

In your case (and simplifying by considering a beam simply supported at both end with a force exerted at the beam center):

1 - the force is multiplied by 4
2 - the moment arm is multiplied by 2 (since the kite is twice as big)
3 - the moment is multiplied by 8 (moment = force * moment arm)
4 - the stress is multiplied by 8 (bendind stress = moment * half spar diameter / moment of inertia)

Then, if you want to maintain the same stress than in the smaller kite, you will need to use a bigger spar that will give you a larger value for the moment of inertia (it goes with the fourth power of the diameter), but also a larger value of half spar diameter (it goes linearly with the diameter)

For a hollow tube, the moment of inertia (I) is:
I = pi / 64 * (OD^4 - ID^2)
pi is the greek letter having a value of about 3.1416
OD is the spar outside diameter
ID is the spar inside diameter
The ^4 means to raise to the fourth power.
And the bending stress (S) is:
S = M * c / I
M is the bending moment
c is half the spar diameter
I is, of course the moment of inertia.

So the aim is to obtain a ratio of : c / I that is eigth time lower for the larger kite.

If you factor all that in an equation you will discover that you have to find the roots of a fifth power equation and then I only took into account a change of diameter (neglecting any change in spar wall thichness). But, hey, with computer so easy to use, lets try some calculations with a spreadsheet software.

Suppose we have a spar that is 5 mm (O.D.) and 3 mm (I.D.).

The values will be:
I = 26.7 mm^2
c = 2.5 mm
c / I = 0.0936

I will try to see what spar is required to obtain one eigth of that number.

Going to spreadsheet, please wait .......................

I am back with the following:

You need a spar of 10 mm with an inside diameter of 6 mm, hence a wall of 2 mm. You migth say, that the diameters were doubled. Well, I tried simple numbers. Suppose you can obtain a spar with a wall of only 1 mm as the original one then you will need a spar of 11,85 mm (about 12 mm). On the contrary, if you want to limit the spar diameter at, say 6 mm then you will discover that even a full rod (ID=0) will not work. The mimimum diameter in this case would be about 9,5 mm.

Anyway I neglected the tension or compression and shearing stress and torsion stress that all add up vectorially to give a combine stress.

It can become quite complex. But usually the flexion is what is more important, with a check for compression to avoid buckling. Also, the mode of spar assembly will make the formulas plus or more complex.

But dont despair, kites can be scaled. Ask any good kite builder and they will certainly give you simpler rules of thumb I am not yet familiar with.

Wind or no wind, fly for fun :-)
Jean (Johnny) Lemire


Hi Jean, You're sharp tonight. Even a bit of pi throwing in there. Great, I'll take that as a "yes". Seriously, doubling the spar OD and ID does seem to give a stiffness ratio greater than 8 times. Some of the spars are solid CF and I'll be going to more tubular spars on the larger version. That'll throw a spanner in the works too no doubt. I've also been alerted to Dave Lord's spar selection guide which is for scaling!! http://www.techline.com/~lord/


Speaking of breaking spars......Have you heard about hemp filled carbon spars????

No this is not a drug importing scheme...Was talking with Peter Lynn in Adelaide and he was saying that he had seen some 1 metre hemp filled spars that could be almost be bent into a circle without breaking......

Honest it was not April Fools Day. Now I am no engineer but to paraphase Peter's comments......

It seems that spars break because they fracture as their circular cross section becomes distorted and bends in on itself...by ramming them full of hemp or presumeably other products the spar maintains its circular profile and can be distorted more without fracturing.......

Mmmmm...must try putting a tight fitting piece of fibreglass into a spar and see what happens..... Any body else heard about these spars.......


The failure mode for a hollow spar in bending occurs when the spar can no longer maintain hoop or circularity. The thicker the wall for a given Outside diameter the more the spar can bend without losing hoop. Fishing rod tips and tapered kite spars have a thick wall relative to their o.d. at the small end and can bend quite a lot before losing hoop. Packing a hollow spar tightly with hemp would increase the amount it could be bent before losing hoop, however a much better way would be to increase the wall thickness, you would end up with a much lighter spar that could bend the same amount. When one uses graphite it is usually to prevent bending, fiberglass spars bend much better.
Dave Lord


Studies of naturally occurring tubes (eg; porcupine quills) show that they have a honeycombed interior rather than being entirely empty and that they demonstrate far greater resistance to breakage by bending because of this.

You could concievably fill spars with an aerated material which would then set hard to achieve this but the generally narrow guage of spars would probably make it extremely uneven.

For strong spars external reinforcement, like a kevlar wrap, is more practical although this may, of course, change.


If you are interested in re-sizing a kite, either up or down, I suggest you read and re-read the book, "The Tao of Kite_Flying" . Part philosopical, part mathematical, but full of gems. Like, if you double the size, you cannot double the weight and expect the same performance.
Barbara Meyer


What Jean says is correct. On my webpage there is a chart of the various spars available that are listed with their relative stiffness values. The equations Jean cites were used to develop this chart and make the job easier. Various types of spars are included so one doesn't have to take into account the modulus of elasticity. Since the user will undoubtedly buy an off the shelf spar in lieu of having a special one manufactured you can forget about wall thickness and diameters and go straight to an existing spar that is closest to meeting your requirements. Using the chart it is quite easy to play "what if" games and size your scale factor to exactly fit an existing spar. Ripstop sails can be made any size but spars are discrete items. In all of my experience I have only once found anything other than bending loads to be important. On a particular kite using a 2 wrap carbon spar for the spine I kept getting torsional failures. Wrapped graphite spars, especially 2 wrap are quite weak in torsion. For large kites one needs to look at the loads on the frame. On an intermediate size kite (15 to 20 square feet) the frame can be improved by using a connector to tie the upper spreader to the spine. For large framed deltas you need diagonal braces from the center "T" up to the upper spreader connection point on the leading edge. In the Nov 1991 issue of Kiting I wrote an article giving more detail.
David Lord


Hi Tel,
I'm no expert, but if you can add more bridle legs, you can often get by with less stiff spars. An example can be seen at: http://www.lekite.com.au/osprey.htm

The kite maker has used a 14 point bridle to distribute the load. A similar approach is used for a suspension bridge. The advantage of many bridle legs is that line isn't as heavy as or expensive as large diameter spars. You do pay a price in drag and complexity, tho'.

good luck, keep us posted on your kite.


Hi david, hi folks.
Quite true. Why do you think the leading edge spars of the new Revolution Speed Serie (Shockwave and Supersonic) and the 1.5 SLE are so big ?

To provide a much greater stiffness while keeping the weigth increase to a minimum. Well .. that's my thinking.

Wind or no wind, fly for fun :-)
Jean (Johnny) Lemire


Mike While some internal structure in a tube makes it stronger in bending it is a minor effect. Stiffness increases as the fourth power of outside diameter minus the fourth power of inside diameter. If the effect on stiffness is not imediately apparent then a sample calculation or two will make it so. Filling up the center of a tube with the same material the rest of the tube is made with has a minor effect on stiffness. If one uses a material that has a much smaller modulus such as some kind of foam then you would have difficulty measureing the increase in stiffness but the increase in weight would be there. Any time you need more stiffness in a spar think of going to a larger diameter not filling the inside of what you are already using.

To make a spar more robust increase the ratio of the wall thickness to O.D. A material like foam with such a low modulus will have a very small effect in helping the spar maintain hoop. If you take the best materiel (highest modulus in this case) to make the spar then to have an appreciable effect by filling the center the modulus of the filler must be in the same ball park as the spar.

Dave Lord

Quadlining a Rokkaku

I was out playing with with one of my Rokkakus yesterday. The bridle on that five-footer is a relatively long one, about 15 feet or so, with four points on the kite. I was able to fly it by the bridle alone in relatively light 6-7 mph winds while holding it by the tow point. While fooling around, I noted that by splaying my fingers and using both hands, I could make the kite go up and down, and, to a slightly more limited extent, from side to side, merely by adjusting my fingers, much like a Rev or other quadline. I was reminded of comments by Johnny Lemire and others in respect of experimentation in flying single line types as a dual-liner.

Now, there's food for thought for someone who wants to try something a little different.


Hi Michael,
That's funny, cause I was out yesterday four lining my 5' Rokkaku also. I built the Rok myself and when I bridled it I used pigtails around the cross bows. I then larks head the bridle on to the pigtails, this allows me to remove the bridle and replace it with my quad line set. I used my Rev handles with 75' lines, it was alot of fun but quite different from the Rev. Since the Rok sheds wind off to the sides the side movements were much harder than the up and down. With a little bit of practice I had it flying all over the window, interesting.
Just Fly It Mike Coons

Original Plans Nasa Para Wing

At last, here you can find the bibliografics of the original reports on the Nasa Para Wing. They are public and can be obtained in some specialised librarys. In the Netherlands you can try the library of the Polytechnical university Delft (even online): and keep looking and you will find lots more of relevant documentation there (and at the Nasa sites).

The original plans of the nasa para wing can be found in a series of testreports by Nasa. Uptil this moment the titles have not been published, because there seem to be some commercial kitebuilders that think that they can forbid this. I donot agree with them. The man who has credit for finding the NPW and make/use it as a kiI'm getting in a little late on this one but here's what I do to install the tension line: I use a "T" handle tool that I had for installing and removing exhaust header springs from motorcycle engines. It's a very compact tool with a small wire hook and it works perfectly - especially during winter here in Tehachapi when its 50 degrees and my hands are freezing.

Enjoy your Illusion - I've been spending more time with my new Prophecy (practice, practice!) but still break out the Illusion from time to time.

Have fun, Stevete was Cees H. a dutch kiter that was active in the early 90's. Now he doesnot fly anymore, for as far as I know. It took me a long time to find out in which reports of Nasa the NPW's could be found. I had to make several telphonecalls in which I got little pieces of information: becauso no one wanted to give the titles. It was Cees H. who gave me the right keywords, so that I was able to trace the originals. I've seen the two most interesting reports and I garantee you, it is nice to see and read what they did. For example I saw some pictures of a test using a scale model of the Apollo-capsule (1:4) with the NPW5. They tested it using a high platform and also they made helicopterflights. It appears that the NPW's are a variety of the parawings of mr. Ragollo, but with a double keel. Number 5 was tested in several ways and also they made some different versions.

If you just want information on the number 5, then I advise you this report: I'm getting in a little late on this one but here's what I do to install the tension line: I use a "T" handle tool that I had for installing and removing exhaust header springs from motorcycle engines. It's a very compact tool with a small wire hook and it works perfectly - especially during winter here in Tehachapi when its 50 degrees and my hands are freezing.

Enjoy your Illusion - I've been spending more time with my new Prophecy (practice, practice!) but still break out the Illusion from time to time.

Have fun, Steve Nasa Technical Note D-5199 Windtunnel investigation of the aerodynamic characteristics of a twin-keel parawing by George M. Ware, may 1969

If you want all different types (nr. 1 up to 10), then take a look at this report: Nasa TN D-5936 Low-speed windtunnel investigation of a series of twin-keel all-flexible parawings by Rodger L. Naeseth, october 1970

By the way, I wrote mr. Ware and had a short correspondence. He doesnot remember these specific tests. It was only one of a long range in history. What a shame. He confirmed the idea that the 'mental-father' is mister Rogallo. It was a wonderfull time to do the research, Cees H. gave me the right tip. And a lot of kiters gave short rumours out of which I could get the right information. Now John Larson and I try to find out what a kiter can do with the information. I am making a number 1, based on the specifications in the reports. For as far as we can see now, the number 5 seemes to be the best model: power and steerability. So if you want to make some NPW, just use the specifications on the sites that we discussed already several times in this newsgroup. If you want more.... mail me/the newsgroup.
douwe jan joustra

Bol Design Software

> Am looking for some software to use to design or give layout

Have fun rotoring at: http://home.plex.nl/...ites/rotor.html

author: Frans Nijhuis.

Mike Gillard

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

Sign In