The very simple answer is to build a "tapered" halyard. That would be covering a small diameter high tech core with a less expensive Dacron sheath over the part that is handle and cleated. The strength of double braid line is in the core.
The most common core is UV treated Amsteel ... it's dymeena line that is stronger than steel. I have presented this suggested many times in this forum so I won't repeat. You can see examples at
www.apsltd.com in the rigging services section.
Another method is to purchase the complete line with dyneema core, such as Samson Warpspeed, then strip away the cover that is not needed.
On my 27 foot boat, I replaced 3/8" rope x 1/8" wire with a 3/16" amsteel core covered with 5/16" Samson LS.. Cost was around $100 for 80 foot halyard. The 3/16 dyneema has a much higher strength rating than the 3/8 sta set... but if you want to move up a size, the difference between core and cover is 1/8" , so a 3/8" line would have a 1/4" core.
If you do it yourself.... it's quite an easy and rewarding project. The splices are at the Samson website. You'll need to make the taper between core only and covered line by performing a "bury" or taper splice. You use the core of the inexpensive cover line to messenger the new dyneema core into place. At the shackle end most will recommend a "luggage tag" eye splice. Very easy single braid splice that is large enough to bend on or remove any closed loop shackle.
12 Strand "Luggage Tag" Splice
Applies to single braids (Vectrus 12, Ultrex 12 and AmSteel Blue) or the uncovered cores of strippable high tech double braids (Crystalyne, Maxibraid Plus) Basically, a large eye splice that attaches like a luggage tag to a suitcase handle. Use it to attach your halyard shackle for convenient replacement, or to securely attach a sheet directly to a sail's tack or clew, avoiding the weight of a shackle. Includes Whiplock™.
Used with Dyneema and Vectran single braids:
Note: This splice will consume two feet of line, so make sure you order your line long enough.
Stripped Cover
A simple way to save weight aloft is to strip the cover off a portion of your halyard. We strip the cover from the head of the sail to the point just before where it's handled. From that point down we leave the cover so that the halyard can be winched, cleated, clutched or even jumped during the hoist. Also, good for spinnaker sheets in low wind conditions; mainsheets to aid running free; and any control line that would benefit lighter weight and freer running.
Used with high tech double braids that have a 100% Dyneema, Spectra or Vectran core that is coated during manufacturing.