November 29, 2007
Rough Water Driving – Beam and Following Seas
Picking up where we left off in my last posting, if you take too much of an angle to the waves and/or find yourself perpendicular to them, then you are operating in a "Beam Sea".
In a beam sea, you can actually operate at a pretty fast speed. Just be absolutely certain to keep an eye out for breaking waves and either increasing or decreasing your speed accordingly steering for clearer water behind the breaking wave. Breaking waves can be very dangerous and can easily capsize a boat if the operator is not paying attention.
If you find yourself unable to escape a breaking wave you have a couple options. You can turn into and ride it much as I described for a "Head Sea" or turn away from it and run in front of it. Doing this seems to make sense, but it could also be much more dangerous unless you can be sure you can out run the amazing speed these waves can reach.
Going with the waves brings us to the next type of sea condition, the Following Sea or heading down wind (going in the direction of the wind/ waves). Traveling in a following sea can be quite deceiving and seem very comfortable as you will be traveling the same direction as the wind and waves which results in a very calm feeling. However, it can be extremely dangerous should a breaking wave catch the RIB from behind. If it does, there's potential the wave can turn the boat sideways to the waves which could set the boat up for a capsize at the next one.
Waves can move surprisingly fast, up to almost 30 knots, which means that your speed through the water could be very low. For example, if you're moving at 20 knots and the waves are traveling at 18 knots, your actual speed through the water is only 2 knots. If you add this low speed to the prop having problems getting any clean water to bight into in the churned and confused water from breaking waves, steering can be rendered virtually useless. This is one reason why it's important to insure your RIB has adequate power before venturing out in rough conditions so that you have the needed power to outrun the waves.
The way to operate in a following sea, is to ride the wave by staying behind the crest or break. As it begins to break, power up so that you sit on the back of the next wave. Whenever running in a following sea, it is essential that you keep a vigilant look out behind so that a wave doesn't catch up and surprise you. Be careful, because you're not always going to feel like you're moving very fast in a following sea, but you potentially will be, so you want to be careful not to power through the breaking wave too early as it's easy to launch off the crest of the wave into the giant hole on the other side and dive into the back of the next wave – stuffing the bow.
When this happens, a dramatic loss of speed results which leaves the boat exposed to the waves from behind again. Also, if the boat stuffs, there's a good chance those on board will be tossed forward and the boat will be filled with water.
Portions of the above advice were excerpted from RIB International (Dec/Jan 06/07)
Posted by ribcraftusa at November 29, 2007 07:30 PM
Comments
One other thing you should do in a following sea is to trim the bow up. This helps to prevent stuffing the bow.
Posted by: David G. Holmes at November 29, 2007 10:08 PM
Yes, stuffing should be left for Thanksgiving turkeys only. I experienced my first one off Gloucester this fall, right into the back of a 7 footer.
Thanks for the commentary Fred. Nice to keep reading about RIBs even though the season here is over.
Posted by: Piper at November 30, 2007 09:01 AM
I have been known to fold the front cell of my 5.85 in rough seas off Gloucester, right up to my front tow post, but of course she rides fine once through the shock of the wave.
Posted by: Brendan at December 3, 2007 02:30 PM
I have been known to fold the front cell of my 5.85 in rough seas off Gloucester, right up to my front tow post, but of course she rides fine once through the shock of the wave.
Posted by: Brendan at December 3, 2007 02:30 PM
Trimming up is recommended whenever operating in rough weather. It lowers the likelihood of burying the bow. One other thing to remember that will help you to avoid stuffing the bow, is to never throttle down as you approach a wave. Doing so, brings the bow down and naturally burries the boat.
Posted by: Fred at December 5, 2007 09:55 AM
