Trend, it is as Mr Natural described. It is an FLD.
FLD stands for future line of demarcation.
It is exactly the midpoint of a bar moved forward by a certain number of days.
Hurst suggested using an FLD of half of the length of the cycle of interest.
So if you are talking about the nominal 5wk cycle you would use an FLD of roughly 2.5wks.
Now the trick is that cycles can vary in length over time and you have to know the current length of the said cycle.
Currently, I have the 5 wk cycle running about 25 trading days (remember to include holidays). So the FLD for the 5 wk cycle would be roughly 12-13 days.
In the Hurst world:
The nominal cycles include the 3-3 1/2 TD cycle.
Then you have the 6-7 TD cycle.
The nominal 2.5wk cycle runs 12-14 TD, but with variability can shorten to 9-10 or lengthen to 15-16 at times.
The nominal 5 wk cycle runs 24-28 TD.
The nominal 10wk cycle runs 48-56 TD.
The nominal 20wk cycle runs 96-112 TD, etc.
So you see, with Hurst's principle of variability, these nominal lengths can shorten or lengthen over time--though usually slowly. That is why you can't just use a fixed interval and hope to have any accuracy.
The FLDs help you forecast a certain cycles expected move and when the FLDs are in a cascade, you can get a peek at a longer term move that could happen. Anyway, if you are interested, I suggest you get the course. I know that Airedale did not use envelopes at all, other than in a totally separate application called the PEERLESS stock market timing. That is a totally different story.
Slinky
