# Help understanding coefficient formula

1. Jun 11, 2014

### andyfive

Hi,

I am trying to understand an equation which I have come across for determining a coefficient based on the size of dimples on a golf ball :

CD_Size = R1·(-3.125·(c/d)+0.25)

In the description, it indicates that R1 indicates a weight ratio of CD_Size.

Can anyone please explain what R1 is and how it is to be calculated?

FYI. the paper this came from can be found on this link :

http://www.ijimt.org/papers/419-D0260.pdf

Many Thanks,

Andy.

2. Jun 12, 2014

### Benit13

A quick look at that paper suggests to me that R1 and R2 are just fitting constants. R1 can be calculated by taking values from figure 5 and substituting them into equation 8 (or better yet, doing it for all values and then taking an average). R1 looks to me to be very close to 1, perhaps slightly less.

3. Jun 12, 2014

### andyfive

Thanks for your reply Benit13. I see what you are saying. Effectively, working backwards from the results in figure 5 to obtain R1. I have not come across the term 'weight ratio' (or as you describe it, fitting constant). They do not seem to explain how they have derived these 'weight ratios' in the paper or why they are used. Still, many thanks again, your reply has really helped.

Andy.