Place Diverter and Porpoising/Chine Walking

[rivercrazy]

I can't tell from the pictures but does that boat have any lifting strakes? Sometimes the inside strakes in many hulls are cut off before they meet the transom. Most jet boats have lifting strakes extend all the way to the transom. This is due to the need for more hydrodynamic lift (lift created from the water not air).
Does the boat ride wet or with a minimum of wetted surface?
If not, and you have 2 sets of lifting strakes, sometimes lengthening the inside all the way to the transom will help increase lift and minimize porposing.
The boat might be trying to take a set but there is not enough hydrodynamic lift so it falls off its set and the process starts all over again.
Just some thoughts anyway...

[spectras only]

Your hull looks like it's a cobra sidewinder .Since these boats had the tank up front they ran wet, usually in the max 55mph range.The majority of them were OB or 455 olds/jet powered.I presume you've moved the tanks to the back to loosen the bow for more speed.However this may be causing porpoising and chine walking with the roundish keel.I had several friends in the 70's-80's with a boat like yours and I don't remember them having the problems you have.On the contrary they just popped on plane and set to a level ride .Forcing the bow down, with a relatively deep v up front on this hull would cause bowsteer and possible spin eek! A place diverter wouldn't cause more porpoising that you already have, it would only lift the bow to a degree and stop going any faster [just a bigger rooster] .You should be able to find the sweet spot with one.If you decide on a trim tab ,use a small one only ,it shouldn't cost you much on speed ,but I feel it would stop your chinewalking with your present setup.
[ December 03, 2002, 04:14 PM: Message edited by: spectras only ]

[greg shoemaker]

The problem you are having is being caused by the bottom of the boat espically due to the design of the inside strakes.Post a more detailed picture of the in side strakes and I'll see if I can help. Greg

[diggler]

greg shoemaker:
The problem you are having is being caused by the bottom of the boat espically due to the design of the inside strakes.Post a more detailed picture of the in side strakes and I'll see if I can help. GregHere's the best I can do with pictures of the bottom...
[img]http://free.***boat.net/gallery/Forum_Graphic_Depot/Bottom_paint_3.JPG[/img]
[img]http://free.***boat.net/gallery/Forum_Graphic_Depot/Bow_Complete.JPG[/img]
[img]http://free.***boat.net/gallery/Forum_Graphic_Depot/diggler31.JPG[/img]
The bottom picture doesn't do it justice though. That was only around 55mph. at higher speeds, only about two feet forward of the transom actually touches the water. I'm thinking a ride plate may possibly be the most effective solution, and it's cheap too!
The side strakes extend all the way to the transom. I'm not sure what a lifting strake is though. The strakes I have are all parallel to the keel and do not elevate the boat that I can tell? Can you explain further about lifting strakes?

[rivercrazy]

Greg will be better at explaining it but. Strakes create lift in the boat bottom and help the boat take a consistent set when on plane by catching water and lifting the boat. They also help in turning by catching the water and minimizing the chances for skipping, hopping, or sliding.
By extending the inside strakes to the rear of the boat, you create more lift.
However, most jet boats have 2 sets of lifting strakes on each side of the keel. Yours already has 3 sets.
Perhaps Greg would be able to suggest if extending them all the way to the back of the boat would be a good solution or not.

[HBjet]

rivercrazy:
By extending the inside strakes to the rear of the boat, you create more lift. Yes, and you create a very unstable ride at high speeds.
RTJ

[Liberator TJ1984]

Diggler , David had all sorts of hell with that thing here too.especially the porposing..he could never get it lined out...they did some work on the bottom of the boat the best I can remember ..it had one hell of a hook in it and they removed almost all of it I belive if not all..try to catch Nate( aka:SSTSleekcraft )here on the boards or post to him he can give you all the skinny on what was done to that bottom as he did the work...
Good Luck....Gopherrr
Check your PM ..sent you Nates #s
going back and reading your posts..I think Dave did also have a ride plate of some kind he made put on too..dont know how it worked though
[ December 04, 2002, 11:00 AM: Message edited by: Liberator TJ1984 ]