The Wake from a hull's design?

[wakeboarder]

I am a wakeboarder who is interested in finding out how the hull design effects the wake. Is there a boat hull design around 23' that would be ideal for making a really big and clean wake?

[Willallison]

Heavy, deep vee, with lots of weight in the bum

[wakeboarder]

Yes all wakeboard boats use a ton of weight to make a big wake, but is there a hull design that doesn't need weight to make the big clean wake. So deep vee hulls make good clean shaped wakes? Could there be any special designs to make the wake?

[SailDesign]

In _very_ VERY simplistic terms, the wake is a function of how much boat is in the water. High weight means more boat in the water (displacement) and hence more wake.
I _did_ mention that was a simplistic explanation, didn't I? But it is the basis for what happens.

Steve

[wakeboarder]

I think that a displacement hull would be to slow but would a semi-displacement hull work? Do you think that a pumpkin seed hull would work good?

[boogie]

hi wakeboarder,

i've seen in a wakeboard video once a device for ski boats called the wedge.

it's basically a fold down hydrofoil that pulls the back of the boat down at speed.
no unnecessary weight for acceleration, but maximum wake at wakeboarding speed. their slogan was something like "all the wake without the weight".

i heard plenty of stories of boats loaded up in the back with water tanks to produce more wake, only to be run over by their own wake when stopping and sinking them...

good luck
boogie

[SailDesign]

I think that a displacement hull would be to slow

Wake, I was not talking about displacement hulls, but about the displacement of the hull (displacement = weight)

Steve

Isn't the size of the wake governed by the shape/efficiency of the hull for the same displacement (weight) of a vessel ?

Crouch's formula for planing speed has lead me to this conclusion as for the same size/weight displacement of a vessel it has a different a different constant value depending on the hull type. Quoting the constants from Dave Gerr's book:

150 - average runabouts, cruisers, passenger vessels
190 - high speed runabouts, very light high-speed cruisers
210 - race boat types
220 - three-point hydroplanes, stepped hydroplanes
230 - racing power catamarans and sea sleds

Wouldn't a deep-vee hull (for the same displacement/weight) be less efficient through the water and throw a larger wake than a hydroplane (or flat bottomed boat) of the same displacement or for a small wake a seasled which pushes the wake underneath itself ? (Take into account that all three hull types mentioned are to be considered having the same displacement.)

Would pushing a flat fronted box through the water make a bigger wake than a vee hull if both had the same displacement (weight) ?

[SailDesign]

Guest - I suggest you look up "simplistic" sometime.

Yes, the size of the wake is governed by an amazing array of things - so much so that even with the most sophisticated CFD codes out there, the wake can still be mis-calculated.
Soooooooo.......... All other things being equal (i.e. hullform) a heavier boat will tend to produce more wake.

Steve

[MarkC]

Look at the Boesch motor boats

from Woodenboat Magzine 164 - feb 2002:

'They have a small but sharp wake at 15-18 mph for trick skiing, and a flat wake for slalom skiing at 35-36 mph'

[Chester]

I have a deep vee 20' bracket boat. It produces a great wake. A Jetski can get air jumping the wake. If i trim out the motor the wake will increase. When the speed is increased to between 30-40 mph the wake is reduced. It seems to be a function of the degree of vee and the speed.

[san.dam]

When the boat is in planing regime,the generated lift due to hull shape make virtually decrease the displacement... and the result is a smaller wake.
I guess we have to stay in the limit of 1,34(froude)
And only a really big displacement (water ballast?)can do the required job. Look at Saildesign's post.
Your speed will be vinculated to the lenght.
If not,you have a smaller wake.

Wakeboard boats that are currently sold appear to be between 20ft to 24ft in length. Due to the nature of the sport that means a trailerable boat.

Yes, displacement is the way to go for a large wake but we have to then get the boat home from the river or bay on a trailer behind the suv.

The amount of displacement applied to the 20-24ft size should be within limits cause we'd rather stay afloat than sink due to excess weight.

Can someone suggest something that can be used for wakeboarding within the above constraints, please?

Information wanted: either a suggested hull shape and/or a added wedge shape and/or what maximum displacement to go to for 20-24ft.

Thanks.

[boogie]

hi guys,

the wedge hydrofoil is doing exactly what you are asking for...

it creates a down force under the stern of the boat. it pulls the boat into the water as if it has a lot more weight to carry.
it only works by the speed through the water. there is no extra weight to trailer or to accelerate with the boat on the water.
the force a hydrofoil creates is mainly governed by the square of the speed you travel. if you double your speed the force increases 4 fold.

here is a quote from an article i found:
<<Lowering the Wedge or Wedge 23 behind the transom provides the equivalent of
over 1,000 pounds of down force, without exceeding passenger weight
capacities. This creates the wake riders seek, without adding weight to the
boat. Safe and convenient, the Wedge and Wedge 23 can be lowered through the
access panel in the swim platform, providing a handy alternative to fat
sloppy water sacks. >>

or have a look here:
http://www.wakepics.com/view_feature.php?featid=77
http://www.wakepics.com/view_feature.php?featid=86
http://www.wakeboarder.com/images/miswegb.jpg

cheers
boogie

[Willallison]

The biggest problem I see with both of the current methods of increasing wake size - ie foils & water bladders - is that you are placing stresses on the boat that it (generally) wasn't designed to cope with. You are effectively increasing the boat's weight by 50% and anyone familiar with scantlings calculations will tell you that this requires a sturdier structure.