The ‘hull’ truth about the underside of houseboats

The 'hull' truth about the underside of houseboats

If you make it to our show in Louisville this spring, keep an eye out for the "hull thumper". This is the guy who allegedly decides he's going to throw down $100,000 (or much more) on a new boat just because he likes the sound when rapping the craft's underside with his knuckles.

It's a humorous stereotype and is obviously meant to be a joke. Unfortunately, this example is based on a predicament far more real, and not nearly as funny. A boat company representative we're acquainted with was on hand when this thumping occurred, and could have easily answered the man's hull questions—if only the man had any. "I've seen it before," the salesman later told us. "Some people just don't like talking about the hull, because they see it as a kind of an enigma." Truth is, it doesn't have to be.

Indeed, there may be a multitude of variable twists to the construction of the houseboat hull. Take a closer look, however, and you'll discover that boat-bottom materials, general types of hull design and the applications different designs serve are all pretty straightforward.

You'll find that the materials are especially easy to understand, just as long as you focus more on the end results of application and less on the intricate details of composition. So with this in mind, let's take a look at houseboat hull materials, as well as the major types of hulls on the market.

Fiberglass:"I like the plastic ones," my niece told me when I took her and my brother-in-law boat shopping last fall. "Not plastic, hon," he told her, "It's called fiberglass." Actually, the little girl had it at least part right.

Fiberglass involves plastic, but it is reinforced by glass fibers. The long term is "fiberglass-reinforced plastic," or "fiberglass" for short. Sounds pretty simple, right? A word of caution here: This is an area where you can easily sink too far down in the details, leaving yourself dazed and bewildered when you finally come up for air.

Basically, glass fibers come in three main formats: cloth, woven roving and mat. The first two are both quite strong, with cloth being the smoother of the two. Most common on hulls is actually a combination of the mat and woven types, resulting in an exceptionally strong outer shell.

In addition to format, fiberglass strength is also somewhat determined by the type of resin used--sometimes based of polyester, other times of epoxy. Our understanding is that the latter type tends to be stronger and more watertight, but a bit more expensive and not very friendly to the skin of those applying it. As a result, you won't find too many epoxy-only applications to houseboat hulls, although a final epoxy coat over the polyester can make a big difference in long-term durability and structural strength. But aside from the pseudo-chemical jargon, what is it that really separates fiberglass from other hull materials?

Styling, for one thing. "Look at the boats with the sleek contours--they're glass," says Bill Brummett, Jr. of Gibson Fiberglass Houseboats. "The basic way in which fiberglass is prepared allows for a variety of shapes ... There are far less design limitations" than with other materials.

Any hull made of fiberglass is the product of a mold that it was "laid up" in. The general consensus is that the best fiberglass hulls are actually laid up by hand, although you can still get good quality with modern techniques using chopper guns.

Steel:Compared to fiberglass and aluminum, steel has a smaller following in houseboat manufacturing circles. It is a loyal following, however--mostly due to the notoriety of aquatic palaces from SkipperLiner, based out of La Crosse, Wis.

In addition to these boats, you'll also find steel in a variety of other types of craft, including older model houseboats as well as fishing, merchant and naval vessels all over the world. "Traditionally, hull material is selected based upon geographic conditions of the area (where) the boat will live," notes SkipperLiner spokesman Todd Jordan. Impoundments such as Lake Powell in Utah; Lake Mead, Nev.; and Rainey Lake, Minn. have rocky shorelines and extremely severe weather, making steel hulls a definite benefit to wary captains.

So with this said, why isn't steel more common among private boat owners? Some folks scorn the material for its weight, for one thing. But even though its raw poundage makes it impractical for planing (rarely a concern for boats of this type, anyway), it will endure decades of hard use if properly maintained.

With steel there is also a perpetual problem with rust, but this can be minimized through regular upkeep. Specifically, steel-hulled craft should be sandblasted and painted with asphalt coating, given inspections and pampered with touch-up work about every other boating season. Further maintenance includes repainting and sandblasting on about a six-year cycle.

Aluminum:Currently, this metal is the most widely used material for houseboat hulls, and for good reason. Per square-foot, aluminum is a bit more expensive than steel, but this is often well compensated for. You don't have to worry about stringent maintenance for dealing with rust, and the lighter weight of the hull will surely save your wallet from distress at the fuel pump.

If you are definitely in the market for a lighter boat, the weight factor also gives aluminum an edge on fiberglass. For example, a 60-foot aluminum houseboat hull will weigh about 48,000 pounds, but the same craft built of fiberglass will run closer to 65,000 pounds. You also don't have to worry about glazing--those little hairline cracks sometimes found on older glass boats.

The downsides of aluminum are minimal. Electrolysis--or stray electric current that is attracted to the metal-can be a problem on aluminum boats (although to a certain extent the same can be said for any hull with metal on it).

Also, cracks and holes found on aluminum may be easily repaired, but it's difficult to fully erase the cosmetic scars they leave behind. Again, these are minor problems. Unless it is painted, there will be little maintenance involved in keeping an aluminum hull looking like it did right out of the factory. The downside of not painting, however, is the aesthetic appeal. And for the sight of raw aluminum, that appeal is scant to nil. Fortunately, there are many products on the market that will easily remove oxidation and chalking that can sometimes occur on this material.

So now that we've looked at the materials, let's dig in a little deeper at some basic types of houseboat hull design: V-Hulls, Semi V-Hulls, pontoons and specialty catamarans and trimarans. V-Hulls Only a handful of houseboats are built on a full V-hull. Some good examples are the Pilothouse 520 from Harbor Master, Stardust's Riveryacht and Lazy Days' Houseboat Motoryacht. V-hull houseboats are great for rougher water. When at rest, they totter easily compared to some other hull types, but can handle larger waves on the move. And as you can easily tell, the bows are usually sharper or more pronounced on V-hull boats a well.

Semi-V Hulls: What's the difference between a V and another hull type-the semi-V? Basically, the two can be differentiated by measuring the dead rise (the angle at which the hull slopes up from the right angle of a horizontal line) at their transoms. If the dead rise is from about 4 to 10 degrees, the hull is a semi V. If it is 11 degrees and above, it is a full V.

Semi-V hulls are commonplace for the more traditional houseboats. Manufactures of semi V-hulls include Gibson, Sumerset, Stardust, Lakeview Yachts, the planing V-bow from Jamestowner and a number of others.

As a general rule, these hulls tend to be more stable than full V-hull boats. Each manufacturer has its own way of getting the best performance out of semi-Vs by incorporating different slopes off the bow, and by use of chines.

It is not recommended to take semi V-hulls out in extremely rough water like the ocean, but in most cases they take rough lake water just fine. In fact, the modern semi-V aluminum hull is stronger now than ever before. Sumerset, for example, has used the aforementioned concept from Linton Cress to produce a patented honeycomb design that incorporates "ribs" every 16 inches across the length of the hull and up to six cross braces between them. The 6-by-10-foot sheets of aluminum used to form the hull are doubled at the bow for extra strength, and cut and shaped to produce every piece required for the entire construction--accommodating boat dimensions from 58-by-14 to 102-by-20 feet.

Beaching a houseboat also holds advantages for the semi-V design, says Bob Kenison of Stardust Cruisers. "On a V-bow, beaching can actually be quite tough. You get a very isolated area of wear, whereas the more rounded area (on a semi-V) spreads that stress out over a wider area." In addition, he says, storage space is excellent on this type of hull. Water tanks, gas tanks, sewage tanks, engines, anchors, life vests, tools, duct work for air conditioning, plumbing, tools, and other items can all be stored in the hull area, thus freeing up the living areas for furniture and more creative decor. Pontoons: Most pontoon or "twin hull" houseboats are built on two tubes, while some are mounted on three--appropriately dubbed tri-toons. Pontoons offer a very smooth ride in rough lake water, due to less surface area to smack the waves. Most of the bad water just goes underneath the boat between the two hulls.

These boats typically don't bank during turns, because the center of balance is dispersed over the width of the boat. Conversely, the center of gravity on V-hull boats is in the center. Pontoons and the closely related catamaran-style aluminum "twin-hulls" are quite safe, says Sheldon Graber of Destination Yachts. Most manufacturers today build their pontoons in 5- to 10-foot separate, airtight compartments. This is to prevent the entire tube from filling with water should one area be punctured. If a section were to become punctured, the compartment would only fill to the level of the hole at which point it would seal off due to its air tightness. This used to be quite an advantage over semi-V mono-hull houseboats, although more recently full-hull houseboats are built in compartments sealed off with watertight bulkheads. Basically, this is the same idea as with the pontoons.

Where full-hull houseboats can store batteries, generators, and the like below deck, pontoon houseboats must have them stored above. This is both a plus and a minus for obvious reasons. They are easy to access and maintain, but do take up precious room and-at least on older boats-can be quite an eyesore.

According to Graber, however, consumers should look closely at the market in the next few years for more utilization of space in twin-hull compartments. The key criterion here is safety, which should be well satisfied with the continuing development of quality materials and modern construction techniques.

Indeed, looking at both the attributes and limitations of the full-hull and twin-hull designs, wouldn't it be great to have the best of both worlds? "A hybrid of the two is what the market is calling for," says Dave Stevens of Utah-based Desert Shore Houseboats. This company's response to the challenge is a "tunnel" hull-a variant of the popular ocean-going luxury catamaran. It was specifically designed to incorporate the stability and economy from pontoons along with the protected utilities on the mono-hull boats, Stevens said. Such a craft makes a good match for inland waters involving long-distance exploration and lower fuel costs. (Look for a more detailed discussion of this hull in the Fall Issue of Houseboat.The twin/tunnel hull “catamaran” concept also has some excellent applications in the world of fiberglass. Catamaran Cruisers, for example, builds its catamarans of glass to allow designers to shape the hulls any way they want right from the initial mold. The idea is to incorporate chines into the hulls so they get better bite and lift.

In addition to makers of pontoon, twin and twin-tunnel hulls, a few companies build tri-hull houseboats. Tri-hulls are as the name suggests--three mini-hulls built to form one large hull. The idea here is to allow channels for the water to flow out the back. Some companies have the channels extending all the way back; some taper them to utilize the water to get better lift. If you're interested in a good specimen for tri-hull study, take a look at a recent Barracuda from the now-defunct Holiday Mansion. On this boat the understructure is actually called a "cathedral" hull. The difference is that the middle keel is the lowest of the three. This design allows the craft to perform like a radical V-hull boat while underway, and like a semi V-hull while at rest. So with all this information under your belt, what would be the perfect hull for your houseboat? One that is virtually maintenance-free and performs like a dream, of course.

Fiberglass applications are always evolving, so you can be sure that lines from Gibson, Harbor Master, Monticello and others will be improving in design and aerodynamics on an annual basis. Also look for boats that are making the move between aluminum and steel, with hulls comprising both materials. According to George Petrie's 1997 Custom Yacht Buyer's Guide, this involves joining an aluminum superstructure to a steel hull, and using an "explosive bonding procedure" to eliminate electrolysis. Interesting stuff.

Are there any better materials and construction techniques existing in addition to what we've covered here? Yes, but unfortunately, not too many of us would throw down an absurd amount of money for a space-age designed titanium hull with a gold finish! The fact of life for any hull-no matter what material it is made of or how it is designed-is that it's going to require preventive maintenance to fully serve its purpose. "And that's really the whole balancing act," says Ricky Comardelle of Louisiana-based cat-hull builder Fiberglass Unlimited. "Decide what you want that boat to do, where you want it to do it and how you'll have to maintain it. That's how to decide on the best houseboat hull for you."

Material Summary
Basic Pros & Cons
Aluminum
+ light material compared to fiberglass and steel
+ most widely used material for houseboat hulls
+ costs less to fabricate than fiberglass
- material costs more up front than steel
+ does not haave the rust problems of steel
+ holes are easy to repair
+ more difficult than fiberglass in repairing with a clean finish

- less strength than steel, but weakness minimized by proper design and bracing

Fiberglass
+ corrosion resistant

- Blistering is still a concern among some consumers, although it is far less a problem now than in the past due to special epoxy and vinyl ester coatings.

+ excellent at absorbing sound, toning down vibration

- less flexibility in modifying a specific boat, as a new mold must be built for each new style of hull

+ more flexibility in design for performance, sleek contours and a sharp finish

- more expensive than an unfinished aluminum hull, although the latter can end up costing more if nicely finished

+ Using the same mold ensures consistent quality from one hull to the next

+ Start-up cost is high, but once the initial mold is set, hulls can then be produced quickly, less expensively and in large volume

+ Usually not difficult to repair-a hole or crack can be "re-fiberglassed" leaving little evidence that the damage ever occurred

Steel
+ variably stronger than aluminum and fiberglass
- weighs 20 percent more than aluminum, adding to fuel costs
+ weight provides lower center of gravity for stability and better tracking

- Rust can be a problem, particularly on boats that are not properly maintained

+ can stretch up to about 30 percent before a fracture or tear
+ flame resistance makes it an excellent choice for fire safety

+ stability and strength make it ideal for long-range cruising