wake size and roster tail

[stevedoc]

Hi all,
I have an older tournament ski boat and the wake, when skiing 22 off, has a large bump right behind the boat. My question is would adding trim tabs raise the back of the boat enough to eliminate the bump and flatten out the wake. Any advice would be helpfull.

Thanks,
Steve

 

[H20Rat]

Re: wake size and roster tail

as a random guess, it PROBABLY would fix it...

Without actual testing on the exact same hull, there is no way to confirm. Shaping a wake isn't always a perfect science, sometimes what you expect to get rid of them makes it bigger.

 

[oops!]

Re: wake size and roster tail

i am guessing that the bump is caused by the prop wash.

tabs might help flatten it or bring the bump closer to the boat as the angle of attack of the prop is changed.

ill ask a guru at work about tournament ski boats and see what he has to say.....but i suspect it will be somewhere along those lines.

 

[oops!]

Re: wake size and roster tail

actualy.....there is one other reason for the bump....

is it from where the boats hull "fills in the void caused by hull plaining?....i mean where the water that comes off the transom and gunwhales meets?

if this is the case......i would need to see pics of the under hull to suggest a "fin" deflector to change the shape of the wake

 

[stevedoc]

Re: wake size and roster tail

actualy.....there is one other reason for the bump....

is it from where the boats hull "fills in the void caused by hull plaining?....i mean where the water that comes off the transom and gunwhales meets?

if this is the case......i would need to see pics of the under hull to suggest a "fin" deflector to change the shape of the wake

I belive most of the bump comes from the water comming off of the transom and meets somewhere back of the boat. I changed to a four blade prop a few years ago and the wake was somewhat better.

The bottom of the hull is very flat with a very slight hook.

The beam is only 80 inchs and I think this causes the hull to ride a little deeper than new boats?

Thanks
Steve

 

[rallyart]

Re: wake size and roster tail

Usually a single tab in the center is used to tune the wake. It can be fixed and adjustable with turnbuckles but putting on a Bennett tab is much nicer if you are adding something. Dual tabs on the sides don't keep the wake as smooth.

 

[metriccrescentwrench]

Re: wake size and roster tail

You may want to ask about this in the skiing forum. There are several guys there with competition ski experience who may be able to add some input.

 

[QC]

Re: wake size and roster tail

I moved this over to the Waterski section. Also deleted the other thread, so we have it all in one now. Good luck!!

 

[skibrain]

Re: wake size and roster tail

Many of the tournament inboards have a rooster tail bump at about 22' off. Shortening to 28' off is the cheapest fix if the wake is better there.
And some of them are just not so great.

The prop can make a big difference and it sounds like you've experimented there. I haven't seen tabs on a ski boat but that doesn't mean they wouln't work. Getting weight out of the boat, or adding some toward the bow can help. We always pull the back seat out of the boat when we ski and prefer to run with 1/4 -1/3 tank of gas for the same reason.

Based on the brand and model, you could ask on some of the model-specific boat forums (MalibuCrew, PlanetNautique, Mastercraft Team Talk, etc) and someone may have a solution for you.

 

[86 century]

Re: wake size and roster tail

The size and shape of the wake can be changed by changing the load(move load forward) ajust your wake plate all the way down. It will make the wake smaller and lessen your hump somewhat.