Date: Mon, 8 Aug 1994 01:44:09 -1000 From: andrewh@holly.harvard.edu (Andrew Hawken) Message-Id: <3255q9$q0f@beta.qmw.ac.uk> Organization: Queen Mary & Westfield College, London, UK Subject: Mixed Spar Selection A colleague and I (mostly him) have built La Hembra from SKII. We are not happy with the spars we have used (infact it turns out that Kite Store did not sell us what we asked for. 6.3mm turned out to be only 6mm, but we bought 6.3mm fittings....) So some re-work is necessary. We have decided to replace the cheap carbon with Beman, either 15 or 16. At the moment the spreaders are Beman 16, the spine 15, but this is only so beacuse that fits the fittings we bought/was to hand. Would making the leading edges from 15 seem like a strange idea? If starting again once again, would people advise against mixed spar selection? If it is a reasonable idea, where would you put the strong ones, and where the lighter ones ? What takes the stress? We believe that there are some quirks in the plans for this and other kites in SKII. Anyone who wants our thoughs should mail me. Andy -- ____________________________Andrew Hawken______________________________ "However many ways there may be of being alive, it is certain that there are vastly more ways of being dead" R Dawkins. Home : 0895 420110 QMW : 071 975 5542 AIIT : 0494 677045 Email : A.Hawken@QMW.AC.UK = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 8 Aug 1994 12:38:45 -1000 From: salanne@convex.csc.FI (Simo Salanne) Message-Id: <326c5l$lot@pobox.csc.fi> Organization: Centre for Scintific Computing Subject: Re: Mixed Spar Selection In <3255q9$q0f@beta.qmw.ac.uk> andrewh@holly (Andrew Hawken) writes: >A colleague and I (mostly him) have built La Hembra from SKII. We are >not happy with the spars we have used (infact it turns out that Kite >Store did not sell us what we asked for. 6.3mm turned out to be only >6mm, but we bought 6.3mm fittings....) So some re-work is necessary. Andy, on page 57 the authors say: "Caution: this kite quite complicated to construct" *********** I have not built La Hembra, but to sew the right amount of camber in the sail & make it work with the frame & bridle, believe the authors. (BTW The Kite Store has never sold RCF brand sticks...) >We have decided to replace the cheap carbon with Beman, either 15 or 16. What's the "cheap carbon" - RBJ? >At the moment the spreaders are Beman 16, the spine 15, but this is only so >beacuse that fits the fittings we bought/was to hand. Would making the >leading edges from 15 seem like a strange idea? please, read the instructions: "Regarding the carbon fibre rods for the frame, preferably choose a High Modulus carbon fibre type (e.g. RCF-Ultra or SkyShark, except for the cross spar. It is better to make this part >From a standard rod." I guess "standard rod" means RCF-6, or like... If you can't get Exel RCF or SkyShark sticks, have a look at spar comparison table (available on hawaii). >If starting again once again, would people advise against mixed spar >selection? If it is a reasonable idea, where would you put the strong >ones, and where the lighter ones ? What takes the stress? It's more complicated... - stiffness - strong (robust) - light/heavy - cheap/expensive "What takes the stress?" I like the advice Dave Lord gave me a couple of years ago; he said something like: the airplanes are not designed for crash loads - why should kites? (Dave, please correct the wording if necessary:-) >We believe that there are some quirks in the plans for this and other >kites in SKII. Anyone who wants our thoughs should mail me. I like to hear your thoughts (and I believe Servaas & Nop would be interested, too). [ If you have not flown-sewn-flown-sewn-flown think again:-] Smooth Plans Simo -- Simo.Salanne@csc.fi STACK Finland = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 8 Aug 1994 13:47:07 -1000 From: mgraves@leadingedg.win.net (Michael Graves) Message-Id: <846@leadingedg.win.net> Subject: Re: Mixed Spar Selection >If starting again once again, would people advise against mixed spar >selection? If it is a reasonable idea, where would you put the strong >ones, and where the lighter ones ? What takes the stress? It really depends on where the frame receives the greatest stress. I generally use the same rod thoughout, but sometimes upgrade the spine one size. There are times when a controlled amount of flex is desirable, so rod selection gets more critical in these places. Beman Strong 15 and 16 are both good rods, though the 16 is more common in commercial kites. A friend has a Stinger 1000 framed in S16, and is very happy with it. He also has a few Stingers in SkyShark IIIp and Vp, which were breaking regularily in team use. The S16 seems to handle accidental impact a bit better, though at the expense of low end wind range. Michael Graves = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 9 Aug 1994 03:38:52 -1000 From: andrewh@holly.harvard.edu (Andrew Hawken) Message-Id: <3280tc$gsc@beta.qmw.ac.uk> Organization: Queen Mary & Westfield College, London, UK Subject: Re: Mixed Spar Selection Simo Salanne (salanne@convex.csc.FI) wrote: : "Caution: this kite quite complicated to construct" : *********** : I have not built La Hembra, but to sew the right amount of camber : in the sail & make it work with the frame & bridle, believe the : authors. As it stands, the kite looks like a good stunter, but we cant tune it correctly. Extensive experiments last night had it at best with excessive overstear, and at worst spinning like a Rev and taking 1.5 turns to stop! I think that the spreaders may be too long? : (BTW The Kite Store has never sold RCF brand sticks...) : >We have decided to replace the cheap carbon with Beman, either 15 or 16. : What's the "cheap carbon" - RBJ? Good question. Yep. RBJ. : "Regarding the carbon fibre rods for the frame, preferably : choose a High Modulus carbon fibre type (e.g. RCF-Ultra or : SkyShark, except for the cross spar. It is better to make this part : from a standard rod." : I guess "standard rod" means RCF-6, or like... : If you can't get Exel RCF or SkyShark sticks, have a look : at spar comparison table (available on hawaii). OK. I am on the case. One FTP comming up.... : "What takes the stress?" I like the advice Dave Lord gave me a couple of : years ago; he said something like: the airplanes are not designed : for crash loads - why should kites? (Dave, please correct the wording : if necessary:-) I agree. Not crash but flight loads. At the moment the wing tips are clearly moving, and therefore the leading edges are not stiff enough? : >We believe that there are some quirks in the plans for this and other : >kites in SKII. Anyone who wants our thoughs should mail me. : I like to hear your thoughts (and I believe Servaas & Nop would : be interested, too). [ If you have not flown-sewn-flown-sewn-flown : think again:-] I phoned Nop about a profile error on the Krypton-S. The first point is given as 36 and he confirmed it should be 26. Similar problems with La Hembra have been passed on to him (I hope). The rest I am not sure about, some are clearly mistakes I made, some are yet to be resolved. Still sewing.... Thanks, Andy -- ____________________________Andrew Hawken______________________________ "However many ways there may be of being alive, it is certain that there are vastly more ways of being dead" R Dawkins. Home : 0895 420110 QMW : 071 975 5542 AIIT : 0494 677045 Email : A.Hawken@QMW.AC.UK = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 9 Aug 1994 02:26:15 -1000 From: russ@ac.wfunet.wfu.edu (W. Russ Hundley) Message-Id: <327sl7$ifo@eis.wfunet.wfu.edu> Organization: Wake Forest University Subject: Re: Mixed Spar Selection Andrew Hawken (andrewh@holly) wrote: : We have decided to replace the cheap carbon with Beman, either 15 or 16. : At the moment the spreaders are Beman 16, the spine 15, but this is only so : beacuse that fits the fittings we bought/was to hand. Would making the : leading edges from 15 seem like a strange idea? : If starting again once again, would people advise against mixed spar : selection? If it is a reasonable idea, where would you put the strong : ones, and where the lighter ones ? What takes the stress? Mark Cottrell's SWEPT WING STUNT KITES contains a reference chart showing which spars take higher amounts of curshing stress, based on the wing planform. I don't recall the specifics (having loaned my copy to a kite buddy), but in a dart-type stunter, the spars requiring the greatest strength are the spine and the lower spreaders. The leading edge rods take a moderate amount of crushing stress, and the upper spreader takes a light amount of stress. Mark is careful to warn that "high stress" is not necessarily a multiple of "low stress", but is used as a comparative measure. I highly reccomend Mark's book as a good treatise on stunt kite DESIGN, in contrast to stunt kite CONSTRUCTION... There are some commercial kites that use different weight spars in different locations. T.C. Powers' Ultra uses Beman 16 Strong for the spine and lower spreaders, 16 Light (I think) in the leading edge, and 13 Light for the upper spreader. I've abused mine pretty badly while learning quad flying, and haven't had any spar failures. LIkewise, my three year old Jordan PRO uses both .2400 and .2200 AFC's. Russ Hundley russ@ac.wfunet.wfu.edu = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 15 Aug 1994 11:11:10 -1000 From: sasaki@netop3.harvard.edu (Marty Sasaki) Message-Id: Organization: Harvard University OIT/NSD Subject: Re: Mixed Spar Selection I've meant to respond to this for a while. The news server deleted the original posting, so I'm going from memory. Anyway, I've made quite a few kites with different spars in different places. As has already been mentioned, it is common to have a stiffer/stronger spine. Some use a lighter top spreader. I use a heavier top spreader in some kites to change the center of gravity. If you are using wrapped graphite with internal ferrules, you can use a heavier/stronger/stiffer rod for the lower half of the leading edge. This will strengthen the rod tip and will allow more violent tip stabs and such. One thing that I didn't see mentioned here was changing the stiffness of the bottom spreaders for varying wind. If the spreaders take a bend while the kite is in forward motion, you can change the bottom spreaders to change the effort needed to get the bend or to remove it >From a kite. This will go a long way to changing the wind range of a kite without having to reframe the whole thing. -- Marty Sasaki Harvard University Sasaki Kite Fabrications sasaki@noc.harvard.edu Network Services Division 26 Green Street 617-496-4320 10 Ware Street Jamaica Plain, MA 02130 Cambridge, MA 02138-4002 phone/fax: 617-522-8546 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =