Date: Tue, 24 Jan 1995 21:04:21 -1000 From: lord@eskimo.com (David Lord) Message-Id: Organization: Eskimo North (206) For-Ever Subject: Advantage 1.5 wrap spars I have seen reference to Advantage 1.5 wrap spars used in ultra light kites. They can"t be what the name implies. If indeed it is actually 1.5 wraps then it is carrying a 1/2 wrap that adds practically nothing to its stiffness or robustness. It could logically be a total single wrap with a spiral strip wound around the single wrap. The spiral strip would have a total area of 1/2 that of the single wrap. Such a configuration would have some additional stiffness and robustness. Does anyone know what the configuration is? A preferable configuration would be a 2 wrap in a smaller diameter to get the weight down and retain more robustness. Dave Lord = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 28 Jan 1995 09:32:45 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Advantage 1.5 wrap spars In article lord@eskimo.com (David Lord) writes: >I have seen reference to Advantage 1.5 wrap spars used in ultra light kites. >They can"t be what the name implies. If indeed it is actually 1.5 wraps then >it is carrying a 1/2 wrap that adds practically nothing to its stiffness or >robustness. It could logically be a total single wrap with a spiral strip >wound around the single wrap. I've never made a spar, so I could be completely wrong here, but: I don't thing so. I think that the spars are made from a helical wound ribbon of fibre. I don't know how wide the ribbon is, but let's say for example that it is 1/4 inch wide. For a 4-wrap spar, you would ensure that for each wrap round the spar, you move down the length of the spar by 1/16 of an inch, providing a thickness of 4 wraps down the spar. Likewise, for a 3 wrap spar, you would move down by 1/12 of an inch for each turn. A 2-wrap would, of couse require 1/8 inch per turn. Note, however that in each case, there is an *overlap* between each turn. If you were to move 1/4 inch down for each turn, the wraps would be joined by a but-join rather than a lap join, which would be extreemly unreliable. I guess that 1.5 wrap is about as far as they can take it. Like I said, this is guesswork. They might get better performance-to-weight (at the expense of more labour...) by having a 1 wrap clockwise then using a half-width wrap running anti-clockwise to hold it together, but if that were the case, then it would be obvious from casual observation. Hmmm... Perhaps a "cross-ply" spar would be considerably stiffer. This would even open up the possibility of spars with holes... Consider a 1/8" wide clockwise wrap with a 1/8" wide anti-clockwise wrap, both at a pitch of 1/4 of an inch... Andrew -- Read the Kite FAQ's: ftp.hawaii.edu:/pub/rec/kites/faq o /\ Kite Jumping: For sale: Prototype Keelless Rowlands Flowform. 2.3m^2 |_ \/ If you want 2.3m^2, Spectra Bridle, Flo-Yellow Carrington Fabric, US$80 (_\ to fly, use a >>Kite Fliers Site: http://www.kfs.org/kites<< andrew@tug.com Hangglider = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =