Snowgoose-1
Well-known member
Just for info, do you sew by hand, and how many rows of stitches.
Ta
UV damage and webbing jackstays
- Thread starter NPMR
- Start date
Ta
Neeves
Well-known member
Dyneema has no elasticity, the shock loads could be enormous damaging the jack stays, specifically the stitching, the individual and the points of securement of the jackstays. You could use nylon tethers - but they are so short as to have minimal stretch.
Jonathan
zoidberg
Well-known member
Snowgoose-1
Well-known member
Well found.
The breakage seems to be where the webbing is attached to the trailer . Difficult to tell if the stitching was the weak point when it is held up by the Shrimper owner.
Even if you have numerous rows of thread , the thread will still not save the day if it is susceptible to UV damage.
What if you used a stainless buckle then stitching for extra security ?
thinwater
Well-known member
A. Does anyone have documented (link) or personal experience of jackstays failing? I only know of two and I am collecting data. It is very rare. I am NOT discounting or judging risk, ONLY collecting data.
B. DIY stitching is touchy subject unless you can pull test your work. There are articles you can Goggle. It is not as simple as how many rows or what thread, because the material you are stiching is also a very large factor. Too much to cover in a post. That said, there are reasons, beyond economy, for why webbing is bar tacked; it gives a stronger, more repeatable result.
C. Dyneema single braid is an option. As Neeves pointed out, the impact forces are greater, so make DARN sure the anchors are as strong as the line. Also, you probably want to go up one size from World Sailing requirements to 6 mm. Part of this is increased strength to handle impact loads, and part is for durability (more allowance for UV damamge). I wrote this up for PS (including testing of geometry and the rolling under foot of various options) but it has not been published. Curiously, Dyneema covered in webbing did poorly. Fat and slippery.
D. The jackstays should be easy to differentiate from other rigging. You don't want to clip a halyard running along the deck by mistake. Something about them should be very different.
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The important things are:
B. DIY stitching is touchy subject unless you can pull test your work. There are articles you can Goggle. It is not as simple as how many rows or what thread, because the material you are stiching is also a very large factor. Too much to cover in a post. That said, there are reasons, beyond economy, for why webbing is bar tacked; it gives a stronger, more repeatable result.
C. Dyneema single braid is an option. As Neeves pointed out, the impact forces are greater, so make DARN sure the anchors are as strong as the line. Also, you probably want to go up one size from World Sailing requirements to 6 mm. Part of this is increased strength to handle impact loads, and part is for durability (more allowance for UV damamge). I wrote this up for PS (including testing of geometry and the rolling under foot of various options) but it has not been published. Curiously, Dyneema covered in webbing did poorly. Fat and slippery.
D. The jackstays should be easy to differentiate from other rigging. You don't want to clip a halyard running along the deck by mistake. Something about them should be very different.
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The important things are:
- Location. The lines should end ~ 4-5 feet from the bow and stern. Locate them inboard if practical, but mostly, hold on when moving.
- Slack. Minimize.
- Clip hard points. Nearly all MOBs are when the person is NOT moving, but is working on something and not paying attention to the motion of the boat. Clip short before working, particularly at the bow and mast. In fact, this is probably more important than using jackstays. People seldom fall when moving, holding on, and paying attention. It's when their focus is somewhere else.
Roberto
Well-known member
I use webbing with 1.5x 2x the (usually suggested) 2t breaking load, whatever I find, and sew them with the Sailrite. Loose a bit of maximum load here and there, there will still be a comfortable safety margin. A bit like soft shackles, if in doubt go oversize, after all it's for personal use and not to be sold, no Breaking Load guarantee or whatever.
Type of stitches, I use both the 7 rows and the "W" patterns indicated/tested here (note the "boxed-X" does not seem particularly good)
dansaskip
Well-known member
Ah but you wouldn't use stitching - that is why I specified using a splice. The strength of the right size of dyeema is 4,800kg for 5mm - I would use 6mm instead as against strength of 2,100 kg for webbing . So there is a much greater safety margin and less likely hood of shock force damage .There again webbing is not very elastic and there are different varieties of webbing some of which are not suitable for jackstays -really only high tenacity polyester is suitable.
