Bolger Illinois. It is BIG.

Design #630


A residence 63’l x 10.0′ x l’6 overall dimensions,

11’ 3 bridge clearance and 31,000 pounds designed displacement.

Illinois (our drawing board name; the boat has not been built so far) was designed for a Chicago man who wanted an affordable Florida houseboat. He intended to build her himself and she was designed to be assembled from diagrams on the plans, a giant “instant boat” using a minimum of tools, but some rather large rental equipment, and time. If constructed all solid ply as proposed, vs. ply-foam-ply laminate in places, she needs on the order of 450 4×8 sheets of 1/2″ plywood. The effort is comparable to building a small house, the foundation on which she’s erected being the 5-1/2″ thick center bottom. Once assembled, that bottom, and her whole structure, are strong and stiff enough to lie on comparatively rough bottoms so that she can be moored in places not fit for either conventional boats or most raft type houseboats. The 18″ draft opens up mooring possibilities now vacant, be it up the tidal creek or behind the sandbar. Her style was intended to avoid the usual protests by owners of shore property in the vicinity of such places. They will fight hard, and usually successfully, against intrusion on their views of house type houseboats, but often actually welcome the presence of a yacht, especially if she goes away occasionally. This craft is a reasonably convincing representation of a large power cruiser of 1920’s vintage. Given a good finish, attractive small craft, and a knowledgeable display of flags, she’s an interesting addition to the scene rather than a threat of an accumulation of floating shacks.

She is actually little if any more difficult or expensive to build than many of the shacks, and likely easier to maintain, aside from her mobility. The mobility is real, if limited. Her main engine was specified to be a 45hp Honda four-stroke outboard motor. Today it would be a Yamaha T-50 high-thrust on account of its bigger propeller. Two of them would actually give her some legs to stride along and stop with some authority. Other drive options are clearly possible, as long as the budget does not get busted, her layout compromised, your maintenance schedule does not mushroom, and she is not turned into a bonified I full-fledged cruiser after all. Then you’ll start nit-picking about her unsophisticated headsea behavior, her marina length, etc., etc.

There is not much data on how fast such a hull will go with such a power plant. The resistance is practically all wetted surface, and the displacement speed of a hull this long is 10.6 knots. Perhaps two large-prop SOs will get her near that in riverine or ICW smooth water. The hull is extremely narrow and shallow for its length and weight, and she will be faster than most people would expect of her simple shape and construction. For most of her speed range, she’ll make no wake whatever. At any rate, if pushed and called for, she should be able to get around faster than most sailing cruisers.

With her reasonable range of stability, a good weather report would be a prerequisite to a passage over to the Bahamas, as with her shallow lower units this far aft she would be likely to lose power in certain length waves if her stern cannot hold the flow. She could, of course, be given more and deeper power and would not be very inefficient up to 15 knots or more, but the cost to outfit and run her would jump in a lot higher proportion than the added speed. That kind of boating was not the point of this houseboat anyway.

For maneuvering, she has a bilgeboard amidships to allow the shallow hull to be swung without skidding and to mitigate blowing away in a beam wind, wherever there’s depth enough to lower it. For finer maneuvering, she carries a bow thruster in the form of a 9.9/l5hp outboard motor in a well in her bow, mounted facing aft. This has numerous advantages over the usual bow thruster:

  1. It lifts clear of the water when not in use, saving drag. corrosion, and electrolysis. The hole in the hull is faired over by a swinging gate which is held open by the propeller race and closes by its own buoyancy and the water running under the hull.
  2. It gives much better thrust than the usual feeble tunnel-mounted thruster and is not limited in how long it can be used at a time as many thrusters are.
  3. It is directional through a 90° arc, too bad outboard motors can not swing 90° or more each way, but a 45° thrust forward can be combined with a 450 thrust on the main engine aft to move the boat straight sidewise or at an angle ahead or astern. Very pretty maneuvering should be possible, even in quite strong winds since she does not actually have very much wind resistance. She’s low-sided and has little top hamper by current standards.
  4. The bow motor can serve as backup power in case of main engine failure. She even could proceed backwards, very slowly and not against much wind or sea, but for an indefinite distance…

On deck, the off-center deckhouse leaves a good passage fore and aft on her main deck with high and stiff railings. There’s space for a powerful and fast tender to make anchoring off reasonably convenient. In fact, Illinois’s stability would allow heavier larger craft to be hoisted up her sides.

The large afterdeck with its fixed awning makes a pleasant place to set up chairs in good weather, while the deckhouse windows are low enough to give a seated view in bad weather, as well as a good view in all directions from the helm. The bilgeboard and the bow motor can be operated from inside the deckhouse. There’s a large cargo hatch for lowering bulky objects and supplies into the cabin, and a bow well for anchor work. We would replace the 45-pound anchor shown with 2×75 pound for hurricane duty, plus a power capstan. Below we tried to keep the furniture as cheap and flexible as possible. The 14’ x 9’ living room would have portable chairs and tables with lanyards to secure them if, by any chance, rough water is expected. Of course, with her midsection she won’t roll as, for instance, a traditional round bilge Trumpy would.

There is a generous galley with a large top-opening refrigerator or ice box, stairs to the deckhouse with a shore-grade tread and riser, a king-sized bed with ample sitting headroom under the deckhouse and two ports to look out by rising on an elbow, one large washroom fit to double as a darkroom, with a 200-gallon holding tank to stretch the pump-out intervals, and a small forecastle for visits from the grandchildren. Not a bad place to live for people with quiet tastes. The underlying principles of both that type of liveaboard philosophy and the matching structure and overall layout stand up in larger and smaller sizes.

Plans for #630 Illinois on six sheets are $400,

available from Phil Bolger & Friends, 29 Ferry St., Gloucester, MA 01930 


Originally posted 2012-06-11 08:17:04.

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  1. Interesting design, though in this size it would probably be better to
    build it in steel. The plywood is cheaper, but sufficient epoxy to pickle
    might make steel cheaper. You wouldn’t need very thick plate as this is
    fairly light displacement for it size(length). In a river environment and
    proper coatings this could last many decades without a lot of maintenance.

    I also think fixing the thruster outboard in
    a tube/circle mounted on casters might allow swinging through a much larger arc.

    While this dimension of hull is relatively easy to drive, unless you expect
    to spend little time in marinas, you are better off shorter with more beam.

    It might be cheaper to buy an old fishing boat and make a trawler/houseboat.

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