Boat Hull Design

BoatBoat HullHull DESIGNDESIGN

by Alex Zidock Jr.

Flat bottom with hard chines Huck Finn’s raft was a basic flat- The boat began to porpoise as the in- bottom boat. So was Robert Fulton’s creasing wind quickly raised waves, Clermont, the first commercially suc- and the bow of the boat began to scoop cessful steamboat. The design of a water into the boat. Now I could see boat hull does not depend on overall my son’s grip tightening as he watched size, but on the intended use of the chine➜ my reaction. This was the first time I boat, or the results the boater wants to experienced this problem with the attain. Misuse of a boat whose hull little flat-bottom boat, and maybe it was designed for another application was just because of his added weight Flat bottom with soft chines could be costly. near the bow, but I knew I could not When my son was about eight years proceed on course or we’d swamp. old, we took our wide-bowed flat-bot- The wind wanted to blow us parallel tom car-topper to a Van Sciver Lake, to the shore and into a cove that had part of the privately run Penn Warner some lily pads. I quickly calculated Club, in Tullytown, Pennsylvania, for that a long walk around the lower part an afternoon of fishing. This portion ➜ of the lake was much better than a chine of the lake was a result of a sand and short swim, so I slowed the motor gravel operation that left the entire Vee bottom enough to maintain a controlled drift, bottom an almost perfect 20 feet deep and the water no longer came in the with few mounds and very little bot- boat. We floated into the pads, which tom structure. The spring day was were close to shore, and with the help bright with no noticeable wind. of the oars we reached safety. It could Launching the boat was usually an have been worse, and even though the easy one-man operation, except on flat-bottom johnboat was not the these weekend outings when it took problem, it met its match. A high- both of us, “working together,” to get sided “V”-hull design soon found its the boat ready to sail. About an hour way to the racks on the wagon. after we were on the lake, I noticed a Vee bottom with strakes slight wind. About 15 minutes later, I Flat-bottom boats could feel the coffee-can cement an- The one thing you can say about chor begin to bounce as the wind and flat-bottom boats is that with their small waves lifted and settled the boat. large bottom area, the boat is very Nothing to worry about, I thought, strakes➜ stable in calm weather. Characteristi- and probably if my son weren’t on cally, however, the flat, broad bow area board and there was no lightning, I’d creates a rough ride. These boats are just ride it out. usually limited to low horsepower mo- My “time to head for shore” an- Vee bottom with pad and strakes tors because they don’t handle well at nouncement was met by a frown as he high speed. Flat-bottom boats are put his rod in the boat. With some greatly suited for fishing in skinny wa- anxiety in my voice I suggested he ter from the Susquehanna River to the

tighten the straps of his life jacket, and ➜ Florida Keys, where a very shallow strakes

I pulled the 3 HP engine to life. ➜ draft is a must. As I began our 100-yard journey pad Early in our nautical history, boats quartering into the wind, and back to were powered by wind or by hand- shore where the station wagon was illustration-Ted Walke stroked oars. Early boat designers parked, my concern for his safety grew. found that boats went faster, and were

16 PennsylvaniaPennsylvania Angler Angler & & Boater Boater www.fish.state.pa.us www.fish.state.pa.us Tri-hull or cathedral hull easier to steer, if the bow was pointed. modification of the “V”-bottom that They also soon discovered that by low- are called tri-hulls and cathedral hulls. ering the center of gravity, the high sail The tri-hull boat is the traditional “V” masts had better balance, and usually hull with additional outside hulls. kept the boat upright even in bad This design is more stable than the weather. “V”-bottom at rest, but it gives a rougher ride in choppy water because Displacment, planing hulls of the increased surface at the bow. These early boats were constructed Tunnel boats have been designed to with “displacement” hulls. This means trap a cushion of air beneath the hull that the hull would push through or to reduce drag on the outside hulls. cruise through the water. The proper Tunnel vee This design is different from a catama- propeller for a displacement hull is one ran bottom because the inner edges of with a lower pitch when powered by an the outside hulls have sharp corners to outboard or stern drive. With the ad- improve the handling of these boats at vent of mechanical power came boats very high speeds. Many race boats are with “planing” hulls, which lift the constructed with tunnel hulls and are boat partially out of the water to skim sometimes called “hydroplanes.” on the surface. Today, it’s sometimes difficult to tell the difference between Pontoon boat the two, but there are slight differences. Very popular in the Keystone State Propellers on boats with planing hulls are pontoon boats. And just as the often are not fully submerged, so they name implies, the pontoon, or deck need to provide holding ability as well boat, is a flat, raised deck supported as higher pitch and rake, because of with two outer hulls (pontoons) that higher top-end speeds. are usually constructed of aluminum. These boats combine a lot of features Round-bottom hull, of other boats. They ride very dry be- “V” bottoms cause the deck is raised above the The round-bottom boat has mostly a Tunnel bottom floats. They are stable, and with the displacement hull and is usually used transom mounted to the underside of for dinghies, tenders, and some car-top the deck, they are easy to maneuver boats. This boat style is usually easier with an outboard motor. to maneuver at slow speeds than the The boater who is looking for all- flat-bottom boat. around use can make almost any hull Catamaran The “V”-bottom boat is probably the design work for many water condi- most common hull design. Most tions. But even in the broadest manufacturers of boats built today use markets, hull design is a continual re- modifications of this design. This de- search and development project. In sign offers a good ride in rough water specific niche markets, like water ski- as the pointed bow slices forward and ing, and now in the fastest growing of the “V”-shaped bottom softens the up- the water sports markets, and-down movement of the boat. The wakeboarding, the competition for degree of the angle of the “V” is called better hulls is tough. “deadrise.” As the “V” shape extends to When you are shopping for a new the back of the boat, it usually flattens boat, first consider the water in which out until it all but disappears at the you’ll use the boat. Then take into transom. Some “V”-bottom boats have consideration how many people will a flat surface at the very bottom called generally use the boat, and then deter- a “pad.” This pad allows a little more mine how the boat will be used. Boats planing surface and at the sacrifice of a come in a wide range of colors and little softness in the ride, but this addi- cockpit configurations that you can tion increases top speed. Pontoon live with if you like all of the other at- tributes the boat has to offer. But the Tri-hull, tunnel hull one thing that should be at the top of

There are many boats in Pennsylva- illustration-Ted Walke your shopping list is what’s on the bot- nia waters that are a distinct tom of the boat you want to buy.

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