From Ptil Tekhelet:
This method defines a chulyah as a group of three twists. It has 13 chulyot, and alternates white and Tekhelet between them, starting and ending with a chulyah of white. Those chulyot are distributed between five (double) knots with four chulyot between the top four knots and one white chulyah between the fourth and last knot.
‘יהל אור, פרשת פנחס רכ”ז ע”א
גר”א (ר’ אליהו בן שלומה בן זלמן, 1720-1797 ווילנא) … ואמר ח”י קשרים כו’ מכאן דאף בי”ג חוליין רק ה’ קשרים והוא בד’ חוליין קשר א’ וזאת קשר האחרון והוא שמא די”ב בחוליין ג”פ ד’ בחיות ושבטים ותקופות וכיוצא וכן בכל קשר בכריכות וז”ש והפוחת ב’ חוליות לכל קשר לבן ותכלת. ומ”ש וצריך לקשור על כו’ היינו בפוחת אבל צריך לעשות לכתחילה כהמוסיף כמ”ש כאן וקאי אחוליות ולא אכריכות כפירוש ראשון שבתוס’ .
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Notes
Notes from Ptil Tekhelet:
- A “Single Knot” is made by taking the four strands from one side of the garment and the opposing four strands from the other side of the garment and tying a simple knot.
- A white “Chulya” is made by taking one white strand from the total of eight strands and wrapping it around the remaining even strands three times. This “wrapping” strand is designated “Shamash” and is used for all subsequent white chulyot (though it is not halachically imperative that the same Shamash be used).
- A blue “Chulya” is made the same as a white one, but just using a blue strand.
Personal notes:
From Micha Berger (who is one of many contesting the assumed string ratio of 2/8):
Did the Gra indeed hold like the Raavad on tekheiles count? We know the he writes in 3 places, each time looking like a different shitah. R Eliyahu Tevgar (https://tekhelet.com/pdf/hagra.pdf) concludes the does hold like the Raavad, but it’s a “nir’eh yoseir”, with the Radziner and R Moshe Sternbuch concluding the Gra held like the Rambam (as explained in that article). (My own read of the Gra on OC was like RMS’s — that the GRA was ruling out “gedilim” for “pesil” — but not specifying whether the Rambam’s pesil or the Raavad’s. I don’t have opinions on the Gra’s peirushim of the Zohar.)
So it seems RMS doesn’t feel the alternative stripe chuliah implies holding like the Raavad.