Made a 61" flemish string - one of the loops keep slipping loose re-did but continued having it slip - what did I do wrong - I have made dozen of strings but have not haved this problem before

I don't make my own strings. (dumb thumbs)

However, I've been using flemish twist strings for 20 years or so. I rarely have the loops "slip" however I have had the ends fray... A few years ago, I started using "Hard as Nails" clear nail polish on all of my new strings.

I string up my bow, make sure the tag ends are laying flat, then put a little drop of polish on the tag ends smooth it out with the brush. I also do the ends of the serving, to prevent any possible unraveling.
I guess you could also put a drop under (or over) your nock point, to prevent fraying and wear.

I'd be willing to bet you accidently twisted a loop up backwards.

Don't ask me how I know:)

If the sections that were turned back into the main bundle to form the loop are too short, the string could slip. It's more likely that there just aren't enough twists in the string to hold it in place.  That could be caused by untwisting one end too much to arrive at a longer string length, as Roy suggests.   

Now a days when you look at tutorials teaching how to tie a string they don't teach you how to back lay a string. Back laying takes extra time but prevents slippage in the loops. I'll see if I can find a pick of the difference.

This ^^^^^^^^ 2X
Most people skip the back lay step.

Look up clay Hayes Flemish twist string method.....easy peasy
Tim B

Roy from Pa x 2

I've made hundreds of Flemish strings and sitting there twisting one up and having a few beers and the mind starts to wander thinking about that big buck walking past your tree stand and the next thing ya know I reversed my loop twisting process on the second loop without knowing I did..

Put the string on the bow and it was a tad too long, so I take the bottom loop off and start twisting the string to make it shorter and the darn string loop literally started to unwind.

So could we say that you were starting to unwind when the string started to unwind, Roy?

Lets just say the string and I both came unwound:)