Joe and Jo McCann are a pair of sailors who like to do things right. When they went looking for a tender for their 34-foot Tartan cruising a sloop a few years back, they wanted a good one.

"We looked for a long time and finally we'd just about decided on a little $500 dink," Mc Cann said. "The salesman was telling us about it and somewhere along the line he slipped and said, 'Of course, it's not a Dyer.

The salesman never closed his deal and the McCanns were on the road to a new world of boats. Now they run the Dinghy Drydock in Merrifield, Va., where they sell and service the immaculate little Dyers. Today they're at the 16th annual Washington International Boat Show with their fleet.

The McCanns aren't easy to find among the sleek power and sailing yachts that dominate this big, impressive show. But a long at a Dyer can tell you something about boat-building that's harder to glean from the splash and polish of the fancy vessels.

Dyers go way back. In the '30s and '40s, they were instantly recognizable for their classy canoe-type ribbing and the glistening, varnished interior woodwork.

Today, Dyer, like everyone else, has switched to fibreglass. But the Warren, R.I., company still understands wood and how to use it.

The eight and nine-foot Dyers are alive with bright mahogany and oak trim. The hulls are hand-laid glass and the spars on the sailing models are sitka spruce. The design is flawless. The fittings are heavy bronze and stainless steel.

The Dyer is a gem, but folds don't pay $3.50 apiece to look at dinghys. Boat shows are for dreaming and there's plenty to dream about at this one.

For starters, it is a monster of a show. Five hundreds boats dtesn't sound overwhelming, but there's more to look at in the D.C. Armory this week than the sedious sailor can absorb in a single day.

The boats cover both floors of the huge, drafty building. The top floor is the main showroom, where big sailboats are fully rigged, their mast-heads poking into the glittering tinsel that's been strung from the arched ceiling.

Down below, the powerboats prevail, scattered across every square inch of gray cement floor.

The range is incredible. For the speed boat freaks, Precision Marine has a spectacle of day-glo glitter racers with giant exposed V8's, sta-right chrome pipes and hull design that guarantees sudden death on anything but mirror-smooth surfaces.

Boston Whaler has a big 21-foot outboard model that looks stable enough to take on Cap Horn in a typhoon. Among the powerboats, there is a pleasing preponderance of deep-V hulls, which is what the Chesapeake Bay demands.

If anything is lacking it's a special section for fishing boats. There are a few bass boats scattered abour and a number of runabouts and open skiffs that would serve nicely for angling, but the fisherman will have to scour the vast floor space to see it all.

That's a source of concern for Bob Anastosio of the Annandale Marine and sports Center. There's really nothing here for the fisherman, bass boat specialist or first-time buyer," he said. "My boss, Col. Myers, has been arguing for years that it's developing into a big-boat show. We sell an awful lot of boats to first-time buyers, and the show just isn't geared that way any more."

Sailors have it a little easier. Because of the low ceiling below, all the sailboats except the tiny Dyer are on the main floor.

The hit of the show will be the Stiletto 27 from Force Engineering. It's a space-age catamaran that will do 20 knots. The hull telescopes, width-wise, for trailering and it has speed-racer cockpits in each hull with streamlined tinted glass roll-back covers. A real shocker.

My favorites among the cruising sailboats are a pair of traditional small yachts that haven't forsaken the time-tested benefits of a full-length keel.

They're off in a far corner of the main showroom - the 23 1/2 foot Alberg Kittiwake and the 25-foot Swedish Marieholm Folkboat.

Both are rigged for the deep blue sea. And that's what dreaming is all about.