The original backstay of the Olson 30 was -4 rod which terminated about 7 feet above the transom and the backstay adjuster was a split wire design with double purchases to the aft corners of the cockpit. The split wire adjusters of most boats have been replaced with cascades or other adjuster configurations. Cascades provide a lot of purchase and are easy to make. Some boats have installed below deck adjusters to maintain a clean deck. Many boats with modified backstay adjusters have also replaced the backstay itself with dyneema or spectra line which saves on weight aloft.
Victrix / Surfer Girl
A new version of the ‘through-the-drains-double-ended’ system. Inspired by the backstay adjuster of the J/99, it requires a sturdy custom bracket at the middle of the transom/deck joint. This setup is similar to the Victrix/Surfer Girl system but has one significant advantage – it is truly double-ended so it can be adjusted from one side of the purchase. The Surfer Girl system uses two purchase lines that are independent of each other. Purchase is 48:1 and full backstay can be pulled on with this setup very easily.
Below Deck Systems
Several boats have installed below decks backstay adjusters. The cleanliness above decks is somewhat offset by the complication below, as well as possibility of water ingress through deck openings, but these systems show ingenuity and clean up above the deck. Photos below from Fast Company.
Backstay cascade diagram courtesy Bill Vosteen.
Here’s an old backstay design from the early 90’s. I knew I had it kicking around, I just had to dig it up. It lists the cable lengths and Harken blocks. I know the Harken 1752 is no longer available, it was a 3 inch block that was way overkill for this application. I know of Olson sailors using the 309 in place of this. The only problem was that they would need to be replaced every so often depending on the usage as the bearings would give out. I never heard them of having a catastrophic failure. The Harken 304 is still a good part.