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Wheel Time

Looking for a new boat? Here’s one way to conduct a sea trial
A high-speed turn can help you determine if a planing hull heels in just the right way.

A high-speed turn can help you determine if a planing hull heels in just the right way.

For those shopping new boats with planing hulls, the sea trial is often more of a ritual than a trial. But the truth is, you should make the time to put a boat through its paces before deciding if it’s the one you want to own. When you get behind the wheel for a run around the bay, consider these things.

Start by checking out the boat while the lines are still tied ashore. A planing hull sitting at the dock doesn’t have many challenges, though it can be too narrow and have excessive deadrise, making it tender. If that’s the case, it will be rolling around like it’s half full of water when you step on one side. Away from the dock, a planing boat changes its behavior as the hull transitions from being supported by static buoyancy at low speed to dynamic lift at planing speeds.

One way to determine if the boat is designed well is to run it at speed, with the loads you expect to have on board. If you plan to run around with full fuel and water and five or six people, then that’s what you want on the test ride. Next, prepare to run a specific maneuver to shine a light on the boat’s conduct. Is it good, bad or so poorly behaved you won’t want your family on board?

Start with a high-speed turn. You want the boat to heel into it in just the right way. Think of riding a bicycle around a corner. You don’t feel any side force at all. On a boat with a planing hull, you shouldn’t get thrown outboard or fall inboard in a turn. The centrifugal forces should balance out nearly perfectly. We will call this a true turn,  and the bicycle is really our model for your boat to imitate. If you’re running down a channel at 30 knots and change course suddenly, anyone standing up is sure going to care that the forces are properly balanced. If the boat has a true turn, the maneuver will be a nonevent. Everyone will still be speaking to you back at the dock.

Here’s how to test for a true turn: Once you’re up to cruise speed, say 25 to 30 knots, warn your passengers and then put the wheel over halfway to the stops, so the boat is turning at a brisk clip. With a standard six turns lock-to-lock (full left to full right), you’ll be putting the rudder over 1½ turns from centerline.  In a good boat, there will be little discernable sideways force as you do so.

I often encourage people to hold onto something and close their eyes, and tell me when we’re in a turn. In a good boat in calm water, you can’t tell, though in a lively chop, you’ll feel the turn intermittently because the boat will be bouncing around. The closer you get to neutral, to the true turn, the better the boat is, since everyone will feel safer, and actually be safer, out on the water.

Absent a true turn, there are two possibilities. The first: At speed the boat turns flat, or even heels outboard, throwing your passengers outboard. Two types of hulls are known to cause a flat- or outoard-heeling turn: the pontoon and the boat with a full-keel design, such as the Maine lobster boat.

The pontoon boat, especially the twin-tube version, has too much initial transverse stability to allow it to heel inboard in a turn. (The inboard tube keeps the boat on the level.) With the Maine lobster boat, the keel can counteract the heeling effect of the rudder and propeller thrust by blocking water that’s trying to flow sideways across the bottom of the boat.

The second possibility is a boat that heels too much in a turn, making passengers fall toward the turn instead of away from it. This is what happens with planing hulls that are too narrow or too high, have too much deadrise aft, or have pod power with inadequately sized chine flats countering the heeling effect.

If you are sea-trialing a planing boat with the intention of buying it, try not to settle for anything other than a true turn. I feel that doing so carries the potential for danger, and that’s non-negotiable for my family. Maybe it should be for yours, too.

This article originally appeared in the April 2019 issue.



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