Reef and Granny
Have a look at what happens when you pull a reef knot and a granny knot tight. Which do you think is best for securing things together? Why?
Problem
This is a reef knot:
And this is a granny knot:
Before you read any further, it might be a good idea to make a reef knot and a granny knot. You do not need coloured string - it can even be done with shoelaces!
Can you see any differences between them?
When a reef knot is pulled tight it looks like this:
When a granny knot is pulled tight it looks like this:
... or this:
or this:
Which do you think is the best knot for making things secure?
Why?
Getting Started
To tie a reef knot you take an end of the string in each hand and do 'right over left, left over right'. A granny knot is 'right over left, right over left again'.
If you want to make things secure with a knot, what do you think is important?
It might be a good idea to try tying two things together using each knot to test them for yourself.
Student Solutions
James from Blue Mountains Grammar School said:
I think the best knot to make things secure is the reef knot. Why I thought that way is because the blue string is tied on the red string and the red is tied on the blue. So it will not disconnect under any circumstances unless you cut them or manually disconnect them.
I can see exactly what you mean, James. Alex from Hutchins School agreed with James:
I think the reef knot is the best because it stays in the same shape and so it will be less likely to slip.
Raj and Tom from Norfolk House School added:
The reef knot is strongest because the harder you pull the tighter the knot gets.
Natasha and Katy from Banbury School thought that the fact that the reef knot is flatter than the granny knot might make a difference too.
Phillip from the Hutchins Junior School thought that the conditions might make a difference too. He decided that:
These are good reasons, well done.
Teachers' Resources
Reef and Granny
This is a reef knot:
And this is a granny knot:
Before you read any further, it might be a good idea to make a reef knot and a granny knot. You do not need coloured string - it can even be done with shoelaces!
Can you see any differences between them?
When a reef knot is pulled tight it looks like this:
When a granny knot is pulled tight it looks like this:
... or this:
or this:
Which do you think is the best knot for making things secure?
Why?
Why do this problem?
Key questions
- How do you think you can tie that knot?
- If you want to make things secure with a knot, what do you think is important?
- Why don't you try tying two things together using each knot to test which knot stays in the same shape?
- Do you think that this will make it less likely to slip?
Possible extension
Learners could have a go at this problem
Possible support