Thanks Capt. Mellow. That really helps.
As payback I'd like to pass along a short vid of some fall colors I
shot in our new surroundings.
http://vimeo.com/groups/16610/videos/7164984 .Added some gentle music
that I wrote. It'll go along well with your final glass (if you're
not dozing on the couch by now, this will help).
John
John,
So far, you're working on how frequency will change with head weight
and length. I'll address that (you're close, but not quite right).
I'd also like to address two other factors you are ignoring:
(1) How flex changes with frequency and length.
(2) How heft changes with length.
HOW FREQUENCY CHANGES WITH LENGTH:
1cpm per 2g of head weight is pretty close. That's a fairly good
rule of thumb.
8cpm per inch of length is a good theoretical number (assuming you
are lengthening from the butt, not the tip). But it tends to vary
substantially from shaft to shaft. You really have to measure it for
the shaft you are using. Frequency meter clamps are generally pretty
good at doing this.
Anyway, if the rules of thumb hold for the components you are
citing, then the light head is offset by length at about 1 5/8" to
give the same frequency. (Not quite the 2" that you cite.)
HOW SHAFT FLEX CHANGES WITH FREQUENCY AND LENGTH
You may be a believer in flat-lining frequency -- or you may have
just forgotten about slope. But if you do believe in slope
(specifically, the slope that most experiments on the subject come
up with, from Joe Braly to today), then you have to allow 8cpm per
inch or so for that. So the 1 5/8" is pretty much eaten up by the
slope, and you need to soften it by an additional 13cpm.
HOW HEFT CHANGES WITH LENGTH
It won't be much of a difference between MOI and swingweight, so
let's use swingweight as our measure of heft.
Reducing the head weight by 27g reduces the swingweight by almost 16 points.
To restore 16 points by lengthening the club, you need an additional 3 inches.
If we were talking about MOI, the additional length needed would be
2.5 inches.
Both of these numbers were easily obtained from the tables at
<<http://www.tutelman.com/golf/design/swingwt3.php?ref=>
http://www.tutelman.com/golf/design/swingwt3.php>.
So, in order to use the 175g head instead of a 202g head:
* Lengthen the club by about 2.5-3".
* Get a shaft that's about a flex and a half softer.
I'll be glad for anybody to review my calculations, because I'm
halfway through my evening glass of wine and feeling mellow. I hope
it isn't too mellow for numbers.
Hope this helps,
DaveT
At 12:07 PM 11/5/2010, j...@clubmaker-online.com wrote:
I'm experimenting with some of these lighter clubheads and longer
drivers and wonder if I'm on the right track when making
adjustments for clubhead weight and driver length.
A frequency decline of 7.95 Hz per inch increased club length (so
add about 8 per inch increase in clubhead length)
Subtract 1 (one) CPM for each 2 (two) grams a head weighs under
202 grams (I pulled this from an old chart from Composites
Dynamics).
So with a 175g head:
202-175=27 g divided by 2 = subtract 13.5 cpm for clubhead weight.
Add about 8 cpm for each inch increased club length.
It looks like you could play about the same flex if you increased
driver length by 2" or so as the length and clubhead weight will
cancel each other out.
If about one inch longer then go about 1/2 to 1 flex softer.
If the same length as you typically use but with the lighter 175g
head, go at least one full flex softer.
This would assume the same BBGM in both heads.
--
Thanks!
John Muir
shoptalk
--
Thanks!
John Muir
skype: jhmuir
AIM: golfcas...@mac.com
810.923.7396
http://clubmaker-online.com
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