HELICAL SENNIT

Here are some photos showing how to make a helical sennit with 4 "ribs". It is an enlargement of an already well known sennit which has 2 ribs.

The eye is a square knot bar (white) which has a 4 strand core (black). 
When the eye is formed there are 12 strands for the sennit, 4 white and 8 black. 
Make an 8 strand MW around the 4 whites and then a standard crown with the whites. 
I use a core for these sennits, in this case a bamboo kebab skewer.
Interweave 2 of the blacks as shown. Choose the ones closest to the white end and bight.
Do the same with the other blacks.
Tighten all strands, particularly the white crown. For maximum neatness I tighten all strands almost to the nth degree, particularly the crown strands.
Everything will be congested at the start but things will get easier as more strands are added and the sennit starts to flare outwards.
Form another crown.
Same as before with the blacks.
This shows how new strands are added. 
Introduce them on the inside where the start will be hidden. 
Tuck the ends as you see here.
Three other reds added on the bight, giving 8 new strands.
All tightened up.
 Another set of strands added (light blue) inside the reds.
All tightened up.
Here you can see the helix starting to form. 
Don't give up if you get a bad start. Everything gets easier as you progress. 
Practice with scrap cord first!!


HELICAL SENNIT BELLROPE

This is a helical sennit bellrope with 6 ribs. The sennit is made with 42 strands and is a slow build!!

Also shown is the 6-strand o2,u2 crown required for this sennit.

SPHERICAL CORES

 Lately I've been experimenting with different sizes of cord and spherical cores to find the best combinations to completely cover the cores. 

The photos show a knot started from a 12 strand crown that I'm satisfied with. The cord is 2.5mm. and the spherical core is 50mm.

HELICAL SENNIT BELLROPE

This is my Christmas offering, a helical sennit bellrope. The helical section is made with 28 strands, the triangular knot below is ABOK#3047 in grommet form and the globe knot is made from a 16-strand crown.

Something a Little Different!

This board has kept me going through illness.
The width is 28 inches (approx) and the maximum height is 22 inches (approx).
With a large area like this to be covered problems occasionally occur and it is best to have a plan B and sometimes a plan C!!

 This is a 16-strand Belt made with 1.4mm polyester cord.


SCK

This is the 12-strand crown that will be used to start the knot. This is just a guide should anyone have difficulty in forming it.

Here is a taped over piece of dowel which represents, for example, the end of a sennit in a bellrope. I have glued a 50mm. diameter wooden bead to the end to keep it steady for this tutorial. I am using 12 cords(2.8mm.) Ideally you will have made the sennit with the same cords.
This is (using Ashley's method) a piece of thin card with the 12 holes numbered to make things easier if you haven't used this method before. The diameter of the circle is 3 inches.
Thread the 12 cords through the holes as shown.
With strands 1,4,7 and 10 form the crown shown. It is just 2 interwoven overhand knots.
Using strands 2,6,8 and 12 , tuck as shown.
With the remaining strands 3,5,9 and 11 finish off the 12-strand crown.
Remove the card. I find the easiest way is to tear around the circumference of the circle. Arrange as you see here. Keep everything slack. 
Helix the cords as you see here. You may have to draw some slack out of the crown to do this.
Try to duplicate what you see in all the photos. Lead all strands to the left out of the way then taking each strand in turn, go O1,U1.
All strands tucked O1,U1.
Take all strands to the left. Again go O1,U1.
All strands tucked O1,U1. 
Make sure there is plenty of slack in the knot and that each compartment is roughly the same size. Try to keep everything neat at all stages. Now form a Wall knot and arrange the ends for following below the original lead.
With each strand go O1,U1,O1,U1. 
Take each strand in turn and fully double the knot, bringing the ends up ready for the third and final pass.
This shows the knot fully doubled and the ends ready for the final pass.
Again, take each strand in turn and make the final pass.
Everything tripled except for the Wall. My preferred method is to not triple the Wall and bring the ends out underneath the knot at the bottom. This can be seen in the bellrope at the end of the tutorial. I'll finish here by tripling the Wall.
Everything tripled.
Take each strand in turn and fully tighten it all the way to the end.
Before trimming the ends it will greatly improve the knot if you "roll" it with a flat piece of stout wood or something similar on top of a flat surface. Trim the ends and that is the knot finished!! Just take your time and you should get the result shown here. 
Good luck!
~~~~~~~~~~~~~~~
This shows the knot on the end of one of my bellropes. 
The cord used was 2.8mm. venetian blind cord ( K range ) from English Braids. It is neither too "hard laid" nor "stiff". 
It is a good general purpose cord. The core is a 50mm. wooden bead. Everything is the same as in the tutorial, just a different cord.
The whole bellrope.

Latest Belt

Here is a recently finished belt. It has 20 strands and slightly scalloped edges. The excellent 1mm. cotton cord was made by Sue Pennison.

GROMMETS

Here are 2 grommets that I've adapted from a sennit by ,I think, Ron Edwards.

Red and blue has 12 parts.

Blue and white has 16 parts.

Both have 13 bights.