The ins and outs of locating and renting a motor home

It looks like a brown dirigible, moored in my brother's yard here; and it seems to require an equivalent amount of gas to fill. The Southwind motor home my family has rented for a long weekend appears poised for an American journey. Certainly this coach is equipped for one - what with its double and single beds, well-fitted kitchen, bathroom facilities, and other rolling amenities.

Yet, in some ways, the imposing vehicle more nearly represents the end of a journey than a beginning.

It took us a good deal longer and almost as many hours of driving to get the Southwind on the road in the first place as it took to drive here from Boston. Renting a motor home, we found, requires patient investigation and lots of time, to say nothing of advance strategy. Most motor-home rentals are snapped up early. If we wanted to spend our summer rolling around the United States (our ultimate goal), the time to start planning was now.

Gathering the figures and examining the vehicles adds up to a pre-vacation saga of its own.

My family's began in East Providence, R.I., at the U-Haul dealer who had offered us the lowest price.

There, for our contemplation, were two units, owned privately and brokered by U-Haul, a common practice. One was a sleek Jayco 26-footer, lavishly appointed and still new. The other turned out to be a 1975 Empire 20-footer. Rusted in places, frayed in the upholstery, a bit ragged around the edges, it didn't look like a junker, but it didn't look like anyone's dream home either.

The dealer tried to rent us the newer unit, which, according to the owner's specifications, could not be rented to anyone with pets, even after we pointed out that we have a rather large dog. ''I'll take the responsibility,'' he said. My wife politely but firmly refused.

Three hours later we drove out of the lot with the Empire, which had stubbornly resisted the efforts of two mechanics to make it roadworthy and livable. A water pump failed; a sewer hose fitting disappeared; a pilot light wouldn't light. But we were committed to taking out a less expensive model and finding out what the bugs would be.

Before we could hunt up these bugs, we first had to scour through an incredible spectrum of prices.

The differences in a three-day weekend rental between two Boston-area U-Haul dealers, for instance, swings all the way from a modest $180 and 20 cents a mile to a high of $450 and 22 cents a mile.

A spot-check around the country revealed similar dips and peaks from area to area.

It is possible to rent a 1984 20-foot Winnebago for $475 a week and 10 cents a mile in Philadelphia. A 23-foot Squire Tioga of similar vintage in Chicago goes for $400 a week and 10 cents a mile. Not too far away, at a Chicago U-Haul, a 23-foot unit runs $600 a week and 14 cents a mile, with promises of superlavish-accouterments. Winnebago Sales in San Francisco offers a 20-foot unit for $778 a week and a 26-footer at $995, including all mileage, insurance, and chemicals - with a 10 percent discount for long-term rentals.

But it is not until you wander into the thicket of hidden costs and vehicle differences from dealer to dealer that you can appreciate the problems of negotiating a motor-home rental, especially on a long-term basis.

Calculating the actual difference in these prices can be tricky, since variations in chemical costs, cleaning fees, and other hidden extras (promises of 10-12 miles per gallon turn to ashes as you watch the gas gauge plummet in a dizzying free fall) add up to unforeseen differences in total costs.

Not to mention unforeseen problems with the coaches themselves:

An hour after renting the questionable Empire 20-footer, we were, at the beginning of a weekend, in our driveway, in a coach with both a broken horn and emergency brake. A call to the dealer led to a nearby U-Haul, where I waited for two hours to find that the unit couldn't be fixed. After which, the renter suggested that I take it on the road anyway.

Declining this invitation to disaster, we ate a McDonald's meal in the motor home in our driveway and settled on the idea of renting a better unit.

We found one at a dealer halfway between Providence and Boston, where we nodded in approval at the manifold comforts of a 29-foot Southwind, all done up in tan and brown and plush interior. Somewhere between the approving glances and signing on the dotted line, a three-day minimum fee at a promised $59.95 a day mounted to $374.44. (Advance mileage accounted for $120 of the total - added to which were the $21 mandatory insurance, $35 sanitation fee and a $17.59 tax.)

The amount seemed reasonable, if a bit daunting. But, somehow, we were not prepared for the $66 gasoline bill, nor the nearly $30 it cost to fill the liquid natural gas tank. By the time we rolled away from the Holliston area, we had spent almost $460.

The change from station wagon - crammed with children, dog, the collected materiel of a family on the move - to a 29- foot motor home can be likened to the experience of a butterfly leaving its cocoon. It brings an irresistible impulse to try one's wings.

Piloting this vehicle, with its Queen-Mary girth, gives you mingled feelings of power and panic: ''That little Volkswagen better not tangle with me!'' or ''How on earth am I supposed to round this tight corner?'' But one adapts to the ways of a rolling dirigible, as one does to the problems of living in its one long, skinny room: crawling around in cramped spaces shoving sheet corners under recalcitrant mattresses; a bathroom the size of two adjoining telephone booths, compounding the usual morning and evening traffic jams; cooking fumes and heat that cloud up the usual pre-dinner atmosphere of enforced cooperation.

''This is going to take a lot of discipline and organization,'' you tell yourself, knowing that the order of understatement in the comment borders on the cosmic.

Given such restricted space, nice appointments are a must. Happily, the Southwind obliged: wood cabinetwork, brown upholstery and carpeting, cafe curtains, and padded white cushions. Drawers and shelves of various shapes and sizes, rigged with racks and hanger slots, were always within reach. The stereo AM-FM radio and tape deck combination pumped music almost everywhere.

Most things you have to do in a camper are automatic in this coach. And almost all of them work. So that you soon find yourself sinking into a homelike state of comfort about the thing.

Which can be dangerous. Because the more at ease you are with the coach, the more apt you are to forget that although this vehicle may handle like a dream, it is composed of a gigantic amount of singularly undreamlike metal and plastic and glass - all hurtling down the highway at high speeds.

''People get going in these coaches on the highway, and after a while they tend to get overconfident. Then, they back up in a driveway and bash into something,'' my dealer told me.

Unfortunately, he didn't tell me this until after I had backed the motor home into a tree three blocks away from the dealership on my return trip. That little mishap wound up costing $310 in repairs and teaching me a valuable lesson: Undercarriages and tops are not covered in most motor-home insurance, since they are virtually uninsurable.

So, three days and almost $700 after first picking up the coach, we walked away, educated, humbled, determined to master motor-homing.