DESIGNING "game improvement" in an iron used to be a matter of give and take. Give distance, take away control; give forgiveness, take away feel. But new materials and methods provide engineers more freedom.

It seems today's give doesn't take as much as it used to.

"Modern technology isn't as overt," says Alan Hocknell, Callaway's head of research and development.

"You can show up to the course with irons that look classic and beautiful, and there's still so much technology packed under the hood."

Game-improvement irons are primarily designed to launch the ball higher and improve ball speed on off-centre hits. This is achieved by changing the way weight is distributed in the clubhead.

"The main limitation with designing irons is weight," says Michael Vrska, Wilson Staff's global director of research and development. "All of our head designs weigh about the same, but the thinner we can make a face, the more we can move that weight to the perimeter of the clubhead, which automatically increases ball speed and forgiveness."

However, the benefits of a thinner face don't occur in a vacuum. Players still want an iron that feels good.

"Feel always makes us sweat," says Benoit Vincent, chief technical officer for TaylorMade.

"It's one of our biggest challenges as we start to redefine the structure of an iron."

Understanding what happens to the club at impact helps designers produce the desired feel.

"We study how the head vibrates," says David Llewellyn, golf-club research and development manager at Mizuno.

"By strategically making areas of the head more rigid or less rigid, we can get those frequencies that we're looking for."

That knowledge can make feel more of a given, leaving the degree of forgiveness tied to things like clubface size and offset (the amount the clubhead is set behind the shaft).

Better players, for example, might want a compact head with little offset without sacrificing forgiveness on off-centre hits. Other players who struggle with a slice might need more offset and a larger clubhead. But even those irons aren't as "oversize" as they used to be.

"Game-improvement irons today defy classification," Hocknell says. "They're distance irons that don't look like distance irons."

media_camera Creative control with irons.

1. Callaway Apex

The Carpenter-steel face insert, which is designed to flex at impact, is welded into a forged-steel frame. The purpose is to control vibration for improved feel. There's also tungsten in the soles of the 3- through 5-iron to lower the centre of gravity.

media_camera 2. Mizuno JPX EZ

2. Mizuno JPX EZ

The thin, multi-thickness face is designed to increase ball speed. A deep, undercut cavity in the 4- through 7-irons lowers and deepens the centre of gravity. The set can be combined with JPX Fli-Hi hybrids, which feature the same lengths and lofts as the irons they replace.

media_camera 3. TaylorMade SpeedBlade

3. TaylorMade SpeedBlade

The redesigned slots in the 3- through 7-irons are three millimetres longer than those in last year's RocketBladez, and the slots become thicker near the toe and heel for improved performance on heel and toe mis-hits. The face gets as thin as 1.5 millimetres.

media_camera 4. Titleist AP1 (714)

4. Titleist AP1 (714)

The long and middle irons have a thin face, a low centre of gravity for a higher launch and a tungsten toe weight to improve off-centre performance. The short irons feature a slightly thicker face for a slightly higher CG and a more penetrating ball flight.

media_camera 5. Tour Edge XCG7

5. Tour Edge XCG7

This 431 stainless-steel cast iron has tungsten weight pads in the heel and toe of the sole for a low centre of gravity. The weighted heel and toe is bridged by a cavity in the sole to enhance feel at impact and improve turf interaction by reducing its contact area.

media_camera 6. Wilson Staff C100

6. Wilson Staff C100

The C100 is more compact than its predecessor (Ci11) and features a thinner face designed to yield higher ball speed. The external frame is similar in concept to the Ci11 but weighs 75 per cent more for improved perimeter weighting and stability on off-centre hits.

Originally published as Creative control with irons