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Basics On A Planing Hull
This is just one of many, question and answer format, articles which you will find at www.ask-boatcat.com. This one deals with some questions concerning bringing a boat up on plane.
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Hi BoatCat,
We have a 2002, 18 ft. Glastron 185GX runabout, and
we are certainly new at boating. In fact, we’ve only
taken our new boat out twice since we’ve had it. Frankly,
I love the boating experience, but I get nervous since we
have our 10 month and 9 year olds on the boat with us. I
am hoping you can explain a few of my worries away.
As my husband is taking off, why does the bow go up and
become hard to see over the bow? In fact, my husband has
to stand to see the water in front of him. Is it because
we need more speed or because the boat contents are too
heavy? It seems when he gains a higher speed the boat
does level out but then I’m not comfortable going that
fast, I’d rather cruise.
When we are moving along and the waves come, should he be
driving into the wave or against the wave? I don’t like
the bouncy feel as we hit the wave.
Thank you for this website! ID
BoatCat Answers:
You're quite welcome ID, and thank you for your questions. As always, I'd like to
first recommend that you and your family enroll in, and complete an approved
Boating Safety Course. You can find links to a number of these right here on this
site on the Boating Safety page. It may be a little soon for the 9 month old to get
involved, but your 9 year old will likely love the pictures and specially designed sites
that many of the links on this page point to.
I urge you to follow the links for the Coast Guard Auxiliary and find a class near
your home. Here you will meet others, interested in boating, with various lengths
of experience, and can get questions answered as they come up. You might even be
fortunate enough to meet someone who would take the time to show you some of the
finer points of small boat handling. Doc, at BoatDocs1, gets several requests a year to
take newcomers out, for a few hours, to show them the ropes and help get them over
the "jitters" which come with starting any new activity.
Glastron is one of the oldest and most highly respected of the "runabout" style
boat companies and their safety design is top notch. I will give you a few of the
basics in the hope that by knowing what's going on your worries will be turned
into boating enjoyment.
In order to answer your first question I feel a need to give a brief, and not too
technical, explanation of what you boat is doing when the bow goes up.
A planing hull, which your boat has, rides on top of the water after reaching a
given speed. In order to "climb up on plane", or get on top of the water, the boat
settles in a bit at the stern and rises up at the bow until planing speed is
reached. Think of an airplane taking off and you'll have a pretty good idea of what
is happening.
On your boat, depending on the size engine and boat load, this should only take
between 2 and 3 seconds. In order to minimize the time it takes to get up on plane,
and therefore the time with the bow up, these tips might help.
TrimThere is a trim switch on the dashboard which has an UP and DOWN position.
This switch moves the prop closer (DOWN) or farther away from (UP) the boat.
When you first start off, you should trim the engine all the way down to raise the
transom up and push the bow down. Once you feel the bow settle, trim the engine up
to a point where the boat is at its best running angle. Books have been written on
this subject, but if you listen and feel as you make small adjustments, you'll be
able to tell when the boat is running it's best.
If you over-trim (raise the drive too high), you will hear more exhaust noise than
normal and the boat may begin to vibrate. This situation is called cavitation and
can be easily fixed by trimming the engine down slightly.
By lowering the power, after reaching planing speed, and adjusting the trim, you
should be able to find a comfortable speed to cruise at. It takes a lot more power
to get the boat up on plane than it does to keep it there.
WeightThe manufacturer lists the maximum cargo weight for your boat at 1200 pounds (lbs.).
Now gasoline weighs about 6.25 lbs per gallon. So if you have a full tank of gas
(29 Gallon tank) that's about 180 lbs. To be on the safe side, figure on about
1000 lbs. of usable cargo weight. Add up the passenger weight and all of the gear.
Don't forget the ice chest, toys, life jackets, etc. Anything added to the basic
boat after you've filled the gas tank will count against your 1000 lbs. A good
rule of thumb for any small boat is the lighter the better. Even a few odds
and ends, say 50 lbs., will be noticeable in terms of ride and acceleration. Don't
scrimp on the safety gear, life jackets and First Aid Kits are light weight, but
avoid unneeded items, especially if they are heavy.
The other part of the weight factor is distribution. Any heavy items (ice chest,
anchor, water jugs, etc.) should be kept as close to the center of the boat as
possible. Avoid placing anything (or anyone) far to the rear of the boat (aft)
as this will add to the bow rise on acceleration.
Don't Make Waves. Doc and I had a little chuckle over this one.
The answer all depends on several factors that I'll try to hit on here. The first
thing to consider is the size of the waves. Doc said, "if they're over 20 feet,
it's time to come in." Seriously though, if we are talking about small swells,
1-2 feet, or the wake from passing boats, then the real question is
"which way are you going."
If you are just out cruising, it's usually the softest ride to take the swell
going into it at about a 45 degree angle. To reduce the bump of the landing,
reduce speed as you crest the wave, being careful to keep up enough speed to
maneuver the boat.
When you are going from point A. to point B. it becomes a matter of not always
taking the shortest course but the one most comfortable. This usualy involves
taking the swells at a 45 degree angle, rather than head on. While this will take
a bit longer, the advantage of a smoother ride are often worth the extra distance.
These are just a couple of tips, to help get you started. The best teacher, in this
as well as most other pursuits is of course, experience. Perhaps you could schedule
some time to take the boat out with just you and your husband, leaving you without
the added worry of the children. Choose a calm day and learn just what the boat will
do under different conditions.
Take turns at the controls, try new things and really get to know your new boat.
If you know someone with experience, ask if they'd come along and show you the
basics. The main thing is to look and listen to the boat and learn how it responds.
In this way you will build your confidence in the boat, increase your enjoyment,
and be able to pass this wonderful lifestyle on to your children.
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