Saw some comment previously on this but quite old - but any reason not to replace the lowers with Dyneema?  I want to do this because I an replacing the through deck blocks which have corroded and don't want the hassle of making up replica wire ones on the boat.

We have used them for years. I had plain D12 on #3386, but this stretched and needed adjusting for a while. DK78 Maxx (black with red stripe) was better and we haven't needed to tweak these since I put them onto #3626 when I put the one string on. Lighter, easier to deal with and the splice on T terminals makes a nice lead for the elastic that I use for the magic beads for the pole system. Win, win, win.

I have a few hundred meters of DSK90 in 2.5mm can splice up lowers for anyone who needs them.

I have tried and tested this rope on 470s and Lasers for the Olympics and it is the best product around. 

Anyone interested let me know.

If you're going to do that I'd use dynastay which is DM10 fibre, still dyneema but subtly different. However I use wire and if will continue to use wire because you know exactly where you stand with it. Once spliced up its stable and will not require re splicing after creep/splice wander age sets in.

Hi Dave, I have used Dyneema on N12's in the past for lowers and it worked well. easy to splice and to get the length right but a word of caution, I have experienced Excel D12 shrink on my daughters 29er main halyard - up to about 30mm over a season. Its made of Dyneeema SK78, Marlow did admit they had heard of this possible problem but (they said) it was very unusual, they didn't offer to replace my halyard! Anyhow, just keep this in mind. I have never experienced rope shrinking before but I have a feeling it may be realated to UV but I have no evidence to support that theory.

Having looked a bit deeper dyneema is supposed to be insensitive to UV, though the coating could be a different story.

It could be heat as the Marlow rep suggested.

I have just replaced the deck blocks on my boat and went through the same decision process. I ended up with new wire ones as the cost difference was next to nothing and I was concerned about UV degredation and stretch/shrinkage. I decided, as Chris says, to go with the tried and tested option as there is nothing wrong with them in the first place.

Long discussion on stretch in dyneema on this forum - see link below.  Includes a contribution from Marlowe's.

Do the class rules permit full composite rigging?

Yes, you can use what you like. I have seen PBO used as shrouds, but not for a while now.

Cheers Chris..

PBO would be expensive and relatively pointless, too susceptible to damage and too expensive to replace if damaged.

Dyneema is a great option and reasonably priced. Great news as my wire swaging machine is busy.

Just wondering which Dyneema and which diameter people are using