Whoopie slings are spliced adjustable slings but Samson's instructions say that the bury has to be so long for the adjustable eye that it's almost unusable. For our 1/4" or 6mm Amsteel Blue sk75 Dyneema, that is a minimum of 3 feet long. Of course, it can be as big as you are willing to make the tail.
We wanted to test if you can get away with smaller bury lengths and also the strength a whoopie loses because it doesn't have a gentle taper, but abruptly comes out of the side. Samson says you can expect 70% of the average breaking strength which is believable but it is sure fun to test it anyways.
A fid is a splicing tool that is 21x the diameter so 1/4" = 5.25". The INSTRUCTIONS say to bury the adjustable part of the whoopie 3.5 fids or in our case with the 1/4" dyneema, over 18"! Overall, with a 2 1/4 fid brummelled eyed makes 3 feet the smallest this adjustable sling!
I sent 150ft of 6mm or 1/4" Amsteel Blue (yes it was orange, that is a brand name) to Jarod Lojeck and he spliced up 3 samples each of 1 fid, 1.5 fid and 2 fid bury's for the adjustable eye. From quick tests in the past I knew 2 fids was going to hold so we didn't bother with 3.5fids like Samson recommends. The eyes on everything was 1.5fids, shorter than they recommended but as you can see, it had no affect on our results.
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What To Think
I have no idea. It's all super good enough and it's nice to see nothing slipped but it is absolutely surprising that eye to eye was the same range as the whoopies. HMPE products break in a huge range whenever I pull on it so just leave yourself some wiggle room of safety and use the next diameter up if you are that worried about the strength. If you spliced 1.25 fids for the eye and only 1 fid for the adjustable part, the smallest your whoopie would be is 18" and that is way more usable. Disclaimer: the more your life depends on this the closer you want to follow their instructions.
Another manual, by Teufulberger, had splicing instructions that made our Brummell slip!