[golfbulldog]

...is MOI the same thing as 'straight line frequency matching' ? If not, what is the difference between the 2 ?

I am no expert but no.. the frequency matching refers to the shaft frequency ...a straight line relationship between the shaft frequency from club to club.

MOI matching is a variation of swingweight matching.... but real swing weight!!

If swing weight is the "heft"of the club...what a club feels like to swing...ie. in motion.... then simply matching the static swingweight to D2 ( for example)...will not give a similar feel whilst swinging the club in real world.

MOI ( moment of Inertia )refers to a measurement of the WHOLE CLUB.... dynamic measurement... it is measured in some weird unit ...but basically you find a club that feels right when you swing it.... measure the whole club MOI of that club.... then use that as your target MOI and alter the shaft length and or weight so that the other irons feel the same when you swing them...that is the key...static feel will not be the same ...it is the swing feel in motion....


SO try swinging your 3 iron and 7 iron...( i assume they are not MOI matched) and you know which one is the 3 iron....

Appparently ...with MOI matched set then they feel the same when you swing them

Never tried it myself.

Note that MOI can be measured for the clubhead and this is the thing that i s quoted in drivers... higher MOI means less clubface twisting when you strike the ball away form the centre of gravity. The sweetspot ( representation of the centre of gravity on the face of the club) does not get bigger...the COG is a dot/pinhead in whatever club...so "enlarged sweetpot" or "sweet ZONE" is marketing.. it just mean higher clubhead MOI... so it feels like the sweetspot is bigger because you get less dispersion and less distance loss on off-centre hits.

Like i said ..no expert ...so correct if details are wrong...but that is my digested knowledge after reading Tom Wishon stuff.