08-02-2005, 08:11 PM #1
- Join Date
- Jul 2005
Has anyone done a wedge back to back for top speed?
I canít see the difference running a wedge or moving the pivot location for an additional 2-degree nozzle trim is there? When you run a wedge were do you set the trim? Mine has no hook and runs best 2 bars down from top and wonder if the wedge would make a difference in speed.
08-02-2005, 09:52 PM #2
Craig, the wedge is good for 1 mph on my setup. I say give it a shot and see what happens.
08-03-2005, 04:15 AM #3
I wondered about this also, until I studied it closer. With a wedge you have an entire pump assembly of pressurized water being released in a "straight" path out of a venturi that has already been tilted 2 or 2.5 degrees. The steering nozzle is then used for just that... steering (and we all know that turning a ski will slow it down). With VTS, the pressurized water is being released "straight" through the venturi and then "diverted" upward by the steering nozzle. Now the steering nozzle is being used to not only steer the ski, but to change the pitch of the ski. This can be a good thing to a point, but eventually the increased angle creates an inefficient turbulance that overcomes the benefit of lifting the hull.
We all know that decreasing a hull's wetted surface by trimming up usually yields more speed. However, over trimming may create an inefficient diversion of water that circumvents the benefits of freeing the hull.
It would seem more prudent to tilt a bowl of pressurized water (wedge plate) and then release it in it's intended direction, than to release the pressurized water and then try and divert it.
BTW, for those who don't have VTS (RXT/GTX) and are apprehensive about the benefits of a wedge plate... try this. Install the plate (2.5 degree preferably) and then turn the plastic, eccentric bushing (located in the bottom pivot point of your steering nozzle) 180 degrees. This will give you the best of both worlds and follow suite with the concept described above.
It worked for me, but will detract "ever-so-slightly" from the nimble feeling inherent with using a wedge (Phil, I forgot to mention this one).
08-03-2005, 05:58 AM #4
- Join Date
- Jul 2005
Those are very good points and I never looked at it like that. So running a wedge is the VTS set in a middle postion?
08-03-2005, 10:51 AM #5
Yes. Then you start with 2 or 2.5 degrees. VTS gives you the advatage of fine tuning your trim, but the ideal position for speed would probably be closer to the center position (no water diversion).
08-03-2005, 01:12 PM #6
So you use a 2.5, limited ?
I'm using a 2.0. I was told 2.5 has too much porpoising.
Did you try the 2.0 and notice a speed difference.
08-03-2005, 04:34 PM #7
Yes, I use the 2.5 and it's never porpoised. However, when I had the 12/18.5 in the ski the hole shot was so stong that it would launch out of the water and cavitate. I tried a 2 degree wedge and it tamed it a little. Now, with the 12/19.5, the holeshot diminished slightly and is perfect with the 2.5.
Kinchyle, I posted elswhere about using a 2.5 and rotating the steering nozzle's lower eccentric bushing 180 degrees. You might want to try it... that's how I'm running mine right now.
08-03-2005, 04:59 PM #8
I'll have my new impeller in a couple weeks. I'll play with that.
Maybe I'll switch to a 2.5 later on when I'm scratching for mph and buy and return one if it doesn't work.
08-04-2005, 11:04 AM #9
So turning the bushing will angle the steering nozzle up ? and this will help speed ?
I'm still confused on the bushing thing (found it though).
08-04-2005, 11:45 AM #10
Actually, most folks will be leary of turning it because it is already in the "angled up" position.
By turning it 180 degrees it will straighten the nozzle allowing the pressurized water in the pump bowl to exit the venturi and NOT be deflected "up" by a tilted steering nozzle. Now, add a 2.5 degree wedge plate (which is before the pump bowl) and get back the upward tilt needed for increased speed. (See above post for more description.)
IMO, this is the best compromise between upward trim and efficient release of the pressurized pump water... at least that is what my GPS is telling me.
BTW, for those who have a Riva Power Filter, 2.5 wedge, and stock or 12/18.5 impeller on your RXT, you are probably launching your ski out of the water on take off causing cavitation and lost hole shot (frustrating, huh). Get a good GPS reading, then rotate this bushing. Your cavitation should be gone, hole shot restored, and GPS should read the same or slightly higher.
It worked for me, anyway.
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