My cruising boat has lazy Jack's about 10mm dia.I have always viewed them as high windage and unnecessarily thick. I have been looking at 3mm spectra or 2mm dyneema for the next set of lazyjack (no blocks, tied). Considering they take very little load and the biggest issue appears to be abrasion from the lazy jack to the sail, why would be making my next set out of 2mm dyneema be a poor idea?

FWIW i went with 3mm spectra on a 30ft'r. A tad less likely to abrade, and a tad more comfortable on the hand when you do need to handle the lines.

Sorry Azure was compiling the below when your post came in so have said the same thing - apologies for the repetition.

Yes 10mm way too thick. For what it's worth see here same question on SA - the OP used 4mm dyneema in the end.

forums.sailinganarchy.com/threads/lazy-jack-topping-lift-line.186556/

Imho 2mm may be too small and be a chafe issue - iirc I used some sort of 4mm rope for lazy jacks 10 years ago and am going to do the same again soon but probably in 3mm or might stick to 4 will view it

4mm dyneema not cheap

www.ropegalore.com.au/o4mm-dyneema-sk-75-rope-sold-per-metre-free-delivery/

Donaghys spectra a lot cheaper

www.sydneyropesupplies.com.au/product/3mm-x-100mtr-donaghys-spectraspeed/

Mine are 3mm spectra and don't really touch the sail till I drop the sail. Not sure where the abrasion is going to be.

Thank you for the responses, makes me understand I'm on the right track.

What about 3.5mm starter cord? Relatively cheap, uv stabilised. $38 for 100m

www.sydneyropesupplies.com.au/product/3-5m

For some reason that link jumps to per m price not roll price.

Yes perfect.