heavy seas ~4ft waves -- how to navigate safely with speed ??

[zurk]

i have a 10.5ft soft inflatable with alum floor and 15HP. goes ~30kph with two on board + fuel + gear. caught in relatively bad seas (4ft waves). it planes well in 2 ft waves but with 4 ft it was hitting the water pretty hard so i went at 1/4 throttle and 8kph. took nearly 2 hours to return.
any idea on how i can go faster in heavy seas with a SIB ?? is there something i can add (maybe a foam block or inflatable triangular block at the back) to convert the planing hull shape of the SIB to a displacement hull so it rides faster in heavy seas ??

 

[Peter_C]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

I have to slow down, or I get yelled at by the little woman, otherwise I would just let the boat run full throttle and in the air half the time.

 

[fbpooler]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

I will bite and offer you the following. With wave height about half as high as the boat length, you were lucky to be in an inflatable. There are also many factors to be considered such as how steep the seas were and the direction the waves were traveling in relation to your coarse. Were large rouge waves present?

If you will normally face such seas, then a larger boat would be the best answer to the problem.

 

[Katch]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

Would moving the center of gravity make any difference? My RIB slams pretty hard in the rough seas. Would moving the fuel tank closer to the stern (instead of up front) be better?

 

[fbpooler]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

I do not mean to be presumptuous, but from these questions one would get the idea that maybe some are unfamiliar with heavy seas. You might start with reading "Chapman Piloting" and discussing the wave action normally encountered in your respective areas with someone with local knowledge. In this area, the normal sea is in the 3 ft range with distance between the waves being the most important consideration.

Weight distribution and motor trim are important factors plus the light weight vs area of an inflatable makes it subject to being capsized or pitched if a mistake is made. When the going gets tough, you should always be in position to change speed or direction to correspond with conditions. Sometimes you are better off to stay in deeper water until conditions improve.

Depending on whether you are in following seas or head seas, trim or weight distribution must be corrected for the conditions in addition to the angle of attack on the seas.

 

[Katch]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

Thanks fbpooler for the reading suggestion and for being presumptuous. Other than spending a bunch of time on dive boats, operating my own boat is new to me. The only instruction I’ve had (aside from reading the boat/motor owners manuals) was taking the Boatus online course. I just downloaded the Piloting, Seamanship and Small Boat Handling - Vol. V (Nook version).

Sorry to have hijacked this thread.

eace:

 

[Sea Rider]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

Zurk,

Check if you can throttle enough to achieve slow plane, which is the mode achieved right away after passing displacement mode. With high waves, better sit inside deck rather than on tubes. BTW, you must not ride at speed on high waves or choppy seas, could have serious consequences...

Happy Boating

 

[zurk]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

couldnt achieve slow plane. best i could manage was 1/4 throttle so basically hull speed with boiling water around the motor (so i was wasting fuel).
inflatable is very stable. wont flip. it just climbs up on the wave pushed up by the motor and slides down until the next one. without plane it could easily manage 4 foot waves with the odd 5-6 footer once every 10 mins. waves were 45-65 degree angles with 2-3 ft spacing in deep water (21 miles offshore by GPS).
i was hoping for a solution to eliminate the boiling froth around the motor so i could go full displacement speed.
fyi the fiberglass 17-24ft boats in the area couldnt get to plane either, some aluminum jets managed to get up on plane in those conditions.

 

[fbpooler]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

Like Sea Rider said, speed is not your friend in heavy seas. Always make sure you start home with about 2/3 of you gasoline still available in case things get iffy. Rough water drinks gasoline at a much higher rate than flat water.

Katch, handling rough water gets down to seat of your pants feel and seeking the best advice you can find to prepare yourself. You are going about it in a wise fashion. A person never learns it all but has to keep on his toes when faced with a challenge and we have had a few night mare type rides home over the years which seems to be part of the experience. There are old pilots and bold pilots, but not many old, bold pilots, so be patient. The sea is very powerful and a great teacher.

 

[Drowned Rat]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

The more oblique you approach the waves, the faster you can go. Hence, a parallel course, you could achieve full speed and a perpendicular course and you must go very slow. Wave frequency is actually more important than size (breaking waves notwithstanding). Heading into the sea, to maintain a higher speed, tack back and forth like a sailboat keeping the sea on your boat's front quarters. If the wave frequency is long enough, and your boat powerful enough, you can zip from one crest to the next and turn slightly as you approach each wave. In a following sea, you better know what you're doing after cresting a wave or you're going to find yourself overtaken and capsized by the wave. If your boat is or feels underpowered, this is a very dangerous situation to be in. Proper power application is key. You can read all you want about technique but once you're out there, it's actually quite intuitive. Practice helps and taking an experienced friend along will help.

 

[ronaldj]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

Thanks fbpooler for the reading suggestion and for being presumptuous. Other than spending a bunch of time on dive boats, operating my own boat is new to me. The only instruction I’ve had (aside from reading the boat/motor owners manuals) was taking the Boatus online course. I just downloaded the Piloting, Seamanship and Small Boat Handling - Vol. V (Nook version).

Sorry to have hijacked this thread.

eace:

Please tell me I misunderstood and you are not trying to do this in the lower Potomac or Chesapeake Bay. Also please tell me you have a marine radio. The coast guard and dnr are not big fans of having to do rescues because people do not follow the small craft advisories.

 

[fbpooler]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

You have to learn to walk before you can learn to run, and Katch is working to learn the trade in a reasonable fashion. Paying attention to the weather and carrying safety equipment is a necessary first step.

If you are CG, then you probably have much experience with those who just charge ahead without taking necessary precautions. I am happy you folks are available, but I do not wish to ever have to depend on others to pull me out of the drink.

The weather changed without warning twice during my boating days, and it is no fun. Coming back through an inlet with about 8 ft breaking waves in a 20 ft boat impressed me greatly. The self bailing feature saved me a swim. After that, just noting a change always sent me back to the hill.

 

[Katch]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

Please tell me I misunderstood and you are not trying to do this in the lower Potomac or Chesapeake Bay. Also please tell me you have a marine radio. The coast guard and dnr are not big fans of having to do rescues because people do not follow the small craft advisories.

Relax, I wasn't in 4-foot waves. I was just bouncing around the wakes from all the other boats in the river (in Woodbridge) - what makes you think I was in the lower Potomac/Chesapeake Bay? Boats do travel in other parts of the Potomac. Also, please don't assume I was out under a small craft advisory. And of course I carry a marine radio. Thank you for your concern

 

[Squid Boat]

Re: heavy seas ~4ft waves -- how to navigate safely with speed ??

couldnt achieve slow plane.
waves were 45-65 degree angles with 2-3 ft spacing in deep water (21 miles offshore by GPS).

How far off shore were you in the 10.5 SIB ? I would be looking for a larger boat. At displacement speed that would be a easy boat to broach or get swamped by a cresting wave.

Cheers, Squid