Mark, This is a good news bad news kind of note...
At 12:54 PM 4/17/2005, [EMAIL PROTECTED] wrote:
I'm wanting to MOI match a set of irons, 6, 7, 8 & 9.
Using a spreadsheet I created with a formula for MOI that was circulating recently, I came up the the following headweights to match the the rest to the 8 iron at D-2.
6 iron- 268 gms 7 iron- 276 gms 8 iron- 284 gms 9 iron- 293 gms
Using Wishon 991 heads, weights of 259gm, 266, 273 & 280., Interflex graphite shafts, cut shafts weights of 78 gms. Wishon reg grips, weight 50 grams. Standard lenghths, 37.5", 37", 36.5" & 36".
First the bad news.
As Alan Brooks already posted, the sort of formulas that predict either swingweight or MOI have errors in them that can easily be 2 swingweight points. Such formulas are good to use to decide what parts to order, but you need more direct measurement (like a swingweight scale) when you build.
Also, as Alan posted, there are only 1.5 points difference between the 6i and 9i when they are MOI-matched. So the possible formula errors are more than the total difference between an MOI-matched set and a swingweight-matched set.
But there is also good news.
Since few golfers could tell a difference of 1.5 points (in either feel or performance) it is unlikely to make a difference whether you MOI-matched or swingweight-matched the set.
Even better news.
I bet you really want to MOI-match the set. Most clubmakers, myself included, tend to put tighter requirement on their work than they believe the golfer will be able to make use of. If that's the case, there IS a measurement you can use as you make the clubs, to guarantee a good MOI match.
Match to the clubs to a sloped swingweight instead of a single swingweight. Use a slope of one swingweight point per inch of length difference. If you use the same shafts across the set, and build to swingweight BEFORE putting on the grips, then the result will be a good MOI match. It is much better than if you built to a spreadsheet formula, and it's just about as good as a more direct measurement (e.g.- Wishon's pendulum) will give you.
Hope this helps. DaveT
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