An easy way to make a flail head is to make a cylinder head:
1. Take a full length of blue foam, measure over on a short side however long you want your flail head to be minus about an inch. 2. Cut it evenly down the entire ~6ft of the mat at that distance. 3. Put glue on one side of this strip. 4. Roll it tightly until the diameter reaches the desired amount. 6. Trace and cut out a cap for both sides and glue them on. 5. Tape it for reinforcement.
You now have a flail head.
After this you need a cover/chain. I only know how to many cloth chains, and I've found them superior to rope chains in a lot of ways.
When sewing the cover for such a thing, make sure that the seams are as reinforced as you can possibly make it. Your head will eventually rip at this seam. No matter what.
If you are using pvc for a core, you can thread this cloth through the center and attach it to the pipe before you put on the pommel.
If you aren't, or you would prefer a more easily fixable method, you can use it to cover the incidental padding and attach it via tape below that.
The cover and chain are one and the same. They are NOT seperate pieces.
The chain rings are just made of scrap foam wrapped in tape. They're just there to prevent the chain from binding up on arms/weapons.
Either way, the covering method is much easier shown than told.
P.s. If your friend hasn't used a sword yet, you might want to have him try that first, just so he gets the fundementals down. The problem with starting out with a flail is that your skill with it will plateau. At first, you will seem to own newer players on the field as you insta-wrap their shields, but after awhile you will notice that it never gets better than that. You will learn a few good shots that work some of the time, but most will be predictable or easily countered by more veteran fighters.
I'm not saying this to bash flail-fighters, as I want to make a flail myself, but I am just saying this to let you know. I know there are ways to do skill shots with a flail, I just also know that newer players won't be able to figure these out without having first been taught how to do them with a sword.
Ain't no reason you can't touch DAP. I've done flail heads both ways we're talking about here, and both got me just as gluey. Also the spray glue head turned hard as hell within 2 months. Only reason I can figure is the spray glue done it.