Oct 18, 2012, 10:34 AM
Post #1 of 8
i was asked a question today that kind of stumped me. is there a minmum no of stiches that need to go into that bartack? does every bartack mashine have a different amount of stiches???i gave my dan poytners manuals out on loan so cant look it up there. i know i can adjust the size of the stiches but i never counted how many are actually there. lets say i want to bartack a line that i have replaced,does there have to be a minmum no of stiches that have to be there?
so any help would be appreciated
(This post was edited by irishrigger on Oct 18, 2012, 10:35 AM)
I just purchased a Juki 1900A electronic bar tacker that is programmed to do a number of different bar tacks. In addition I obtained from MEL an EPROM programmed with those used by parachute manufacturers. This includes many different bar tacks.
Mechanical bar tackers can only do one stitch. They come in many different configurations and can be customized for any pattern Camatron in New Jersey and Jaffe in New York, and probably others. In fact the 1900A I bought had a custom clamp and patter done by Camatron.
To replicate the factory stitch (which can be considered the best standard practice and considered required by some) you would need several customized machines for different bar tacks or a machine like the one I just got that can do many different tacks. As a practical matter lots of lines have been replaced with zig zags or bar tacks that vary from the original. I let others with more line experience comment on whether they think that it makes a difference. But the damage to the line from a bad needle, bad stitch formation, bad placement and line length are probably bigger issues than the pattern used.
Hi Roger - Thought I'd chime in here and try to give you a puurfectly muddy answer. The answer is that there are tons of different types of bar tack stitches. If you are asking about bar tacks on lines then as was explained above PD uses a 42 stitch center start - stop stitch on mains and reserves. Truth be told there is a method for doing main line sets that doesn't even require stitches but that's a different thread (no pun intended). There are other manufacturers that use 42 stitch left or right start stop. But that depends on how you orientate the line to the machine :-) 28 stitch bar tacks are commonly used as well. The commonly accepted definition of a bar tack is that there are straight stitches covered by zig zag stitches. Can be 8 or 80 stitches. There are also those that call the stabilizer stitch a bar tack. Often times it is. I've relined plenty of canopies just using 304 or 308 zig zags too with no center straight stitches. They never seem to come undone but a bar tack is certainly preferable. The very cool programmable bar tackers can be programmed to do all kinds of stitches that are or resemble bar tacks. But 42 and 28 are the two more common out there right now and have been for years. Personally i have a couple of 42 left start stops that get used on mains all the time. Can't go wrong there. If you can find an analog bar tacker that does 42 center start stop buy it and if they have two give me a call. So I guess my final answer is to put as many stitches into a finger trapped main line as you see fit. It's the finger trap that does the work of holding the line mating anyway. The stitches just hold the line in place while the line is slack. (But i would strongly recommend at least a 28 stitch bar tack or stitches. Hope that clears things up a little ;-)
(This post was edited by aironscott on Oct 23, 2012, 10:38 PM)
PD: * 28 for leading edge bartacks & Stab. attachment to A4 (7 cells) or A5 line (9 cells) tab - could be center start/stop or side start/stop. * 42 for lines work center start/stop & some inside canopy bartack on the center cell tapes & PCA attachment point. * 42 center start/stop on the VR360 lines & line attachment points to stab - lines runs inside the warped around 1" Ty.3 * 72 or 73 center start/stop for line attachment to stab. & on the main slidres kill lines. (EF blue thread)
AERODYNE: * 42 side start/stop on lines, stab. & leading edge bartacks. * 42 center stop/start on lines tabs to canopy & PCA. ** On older canopies all were 42 side start/stop.
ICARUS NEW ZELAND: * 42 center start/stop on lines, lines tabs & leading edge bartacks. * 73 center start/stop for lines to stab. attachmnet points. ** Older canopies had 42 side start/stop bartacks. *** #60 nylon thread for lines work.
ICARUS SPAIN: * 42 center start/stop for all bartacks. *** #60 nylon thread for mains & #40 for reserves.
PRECISION: * 42 center start/stop for all bartacks. ** Older canopies had 42 side start/stop bartacks.
There are more mfg. most use 42 bartacks - see the original product.
*** The bartack design & the locking points method of the bartack are very important.
(This post was edited by RIGGER on Oct 24, 2012, 12:57 PM)