| One of the biggest problems many boaters face is | | | | speeds less than or equal too the above formula. |
| wake management. Admittedly this is a very | | | | That is the simple physics of hydrodynamics. Any |
| sensitive subject about which most boaters have | | | | more speed produces more wash, period! |
| their own opinion. Some boats traveling through a 'No | | | | Note: Catamarans and hydrofoils fall into another |
| Wake Area' merely reduce speed. This may work for | | | | category. |
| some boats, but for others it appears to actually | | | | Now the above formula applies only to perfect |
| increase the amplitude of the wake. Why is this so? | | | | design and lines, for most boats, true no wake speed |
| To begin with let us first look at the three basic | | | | will be slightly less, with performance being adversely |
| types of boats when discussing wake or wave wash. | | | | affected by load, draft, wind and sea conditions |
| Full Displacement Hulls: This type of boat never climbs | | | | turning choppy. |
| up out of the water no matter how fast it goes. | | | | Smaller boats that plane will leave a bigger wake at |
| This is usually a heavy large boat with minimum | | | | high speed than at displacement speed, however |
| horsepower, (think Trawler). The faster it goes the | | | | even then the wake can be much less than a full |
| more water it pushes out of the way and the bigger | | | | displacement or semi-displacement boat trying to full |
| the wake it leaves. | | | | power above the waterline hull speed. |
| Semi-displacement Hull, (also called semi-planing): | | | | Bottom line, this is only a guideline, although usually |
| These boats have hull designs and enough power to | | | | pretty accurate, a boat operator needs to pay |
| lift some of the boat above the water in order to go | | | | careful attention to the wake his boat actually |
| faster, (think Cabin Cruiser, or Sport Fisher, and some | | | | produces. The best way to learn your boats wake |
| Houseboats. This usually reduces the first wake or | | | | signature is have someone else operate the vessel at |
| Bow wake, but leaves a propulsion wake that can be | | | | different speeds while you stand on the shore or |
| quite excessive and frequently so far behind the | | | | another boat at rest and watch your boat go by. |
| boat that the operator is completely unaware of the | | | | Try different combinations to get the best idea. |
| wake he is leaving. | | | | All this not withstanding, while the rules state a boat |
| Planing Hulls: These boats at cruising speed frequently | | | | operator is responsible for his wake, nowhere do the |
| have 75% or more of the waterline above the | | | | rules exonerate a vessel owner or a dock owner |
| water, ( think Bass boat), and leave a very small | | | | from being responsible for having a seaworthy |
| wake, at least when traveling in a straight line, | | | | vessel, or from building a dock or other waterside |
| although tight turns immerse the waterline and | | | | facility that is not appropriately suited for the |
| increase the wave wash. | | | | particular environment. Along commercial waterways |
| Although all three types of hull can produce a | | | | it is more common than not for dock permits issued |
| damaging wake, it is usually the Semi-displacement | | | | by the U.S.A.C.E. to specifically state that it is the |
| hull type that most people associate with big waves. | | | | dock owner who is responsible for securing his dock |
| How fast is too fast? A good general guideline for | | | | and vessels moored there in such a way as not to |
| maximum speed with minimum wake is: Take the | | | | be vulnerable to wakes from passing boats. In almost |
| square root of the length of the waterline of the | | | | all scenarios there is at least a shared responsibility. |
| vessel at rest and multiply that by 1.2. The result is | | | | Example: a canoeist who gets swamped on the |
| the speed in knots that most hull shapes should be | | | | Mississippi River by an up bound towboat is a victim |
| able to move through the water with minimal | | | | of his own lack of experience and has little if any |
| disturbance as well as maximum energy and fuel | | | | recourse through law. |
| efficiency. Multiply that by 1.15 to get the speed in | | | | However, remember being legally correct is not |
| MPH. | | | | always good enough. The rules require a boater to |
| Example: A 25 foot waterline has a square root of 5, | | | | depart from the rules if compliance will not avoid a |
| which when multiplied by 1.2 yields a 6 knot speed | | | | collision or accident. When all is said and done, if you |
| that this boat should be able to manage without | | | | are in a hurry, take a plane or drive a car. Despite |
| creating havoc. Multiply this again by 1.15 yields 6.9 | | | | the rules, a lot of people on the waterway are |
| MPH. A 36 foot waterline yields 7.2 knots or 8.3 MPH. | | | | recreational users that simply do not have enough |
| A 49 foot waterline yields 8.4 knots or 9.66 MPH. | | | | experience to always be where they should be when |
| ALL conventional boats, regardless of type, leave the | | | | they should be. When in doubt slow down to |
| smallest wake when cruising at full displacement, at | | | | displacement speed, everyone can live with that. |