Like “The Full Monty,” a popular Broadway stage musical, “Calendar Girls” is based on anticipation and expectation of nudity. Naughtiness sells tickets.

In the former, out-of-work blue-collar dudes figure out there’s moolah in stripping, with a brief bare-all scene at the final curtain. In the latter, now playing at Diamond Head Theatre, a group of middle-aged women figure there’s incentive and appeal in a calendar where posing in the buff might yield much-needed bucks to finance a settee for a hospital. The peeling happens prior to intermission.

Mission surpasses modesty, in this slight, often trivial based-on-real-life anecdote, about Yorkshire’s Women’s Institute, which Brits know as WI, and how its “alternative calendar,” comprising middle-aged women concealing the obvious body parts, managed to become a viable fundraiser to ultimately finance a hospital wing, so the legend goes.

And the rest of us might wonder: Why?

Why make a mundane show about a not-so-outrageous idea, particularly one in which the clothes (or lack of ’em) encounter of the worst kind occurs in act one, leaving a huge vacuum as the plot thins, not thickens, toward the finale?

There is a musical version of “Calendar Girls,” which might have had some valid tuneful relevance, but this isn’t it. So the challenge is: How long can you tease the spectators over hurdles of ageism, grief, compassion, community disdain and plain-and-simple shame?

The play offers some laughter as it explores multiple facets of humankind. But mostly, this is a stifling comedy of British mores and manners, requiring distinctive accents and tone, unevenly spoken here with a lack of conviction. In a word, it’s marginal.

A grieving Annie (Colleen Parlee) and her overt and persuasive friend Chris (Betty Bolton) support this calendar project with nudes, in lieu of church scenics, to raise funds for the hospital after Annie’s husband, John (Shane Noel), dies of leukemia. Four other BFFs — Jessie (Holly Holowach), Celia (Susan Hawes), Ruth (Liz Stone) and Cora (Dawn Powell) — join the rally, a few reluctantly, to become monthly pinups to pose for photographer Lawrence (Jesie Rocetes).

Like those erotic and suggestive but successful firefighter versions, this calendar supports a worthy cause. Oh, George Clooney’s name is dropped here, but seriously, he’s not ever going to engage in this sort of fluff.

The well-intentioned women hide behind buns, balls of yarns, fruits, teapots and cups, but not very convincingly, to shield the obvious, and there’s a lack of other candidates to represent other “months.”

Further, the alleged widespread response from world media to the calendar seems woefully overstated.

Marie (Lisa Konove), the outspoken WI leader, has a few humorous moments, but most of the roles are not defined with relatable idiosyncrasies, making it a task for a cast that is eager to please. But they have a good time anyway.

Ahnya Chang’s direction is straightforward and serviceable, considering the lack of meat in the script.

Willie Sabel’s set — tall, windowed panels and lofty overhead beams — frames the story with its own sense of glory.

For a nonmusical, “Calendar Girls” has quite a bit of atmospheric tunes for scenery and mood changes, begging the question: Wouldn’t it have been prudent to do the musical version instead?