07-24-2006, 03:14 PM #1
???? For all of you with Fast Skis :)
I have had some time to piddle around the last couple of weeks and was wondering.
For all of you guys out there that seem to have abnormally fast ski's Ex....
73MPH Stage I
75MPH Stage II
I was looking at my grate after I pulled it off as it was recessed into the ride plate 1/32" of an inch. I figured I would shim it down flush. Looking at the bolt holes in the grate it appears there has been some stress around the center hole like the grate was trying to pull down and rather than pull the inserts out it put a slight dimple in the mounting hole??
So then I got looking at the rideplate and noticed that the plate is not flush with the hull rather it is recessed up a little causing a slight step up between the hull and rideplate.
So for you guys that run really good speeds on fewer mods than the rest of us look at your ride plate and see how yours is mounted in comparrison to the hull.
As big of a deal as filling the bolt holes are maybe a flat or true ride plate can make up some ground for some of the average skis???
Last edited by 1 FAST VE; 07-24-2006 at 04:52 PM.
07-24-2006, 03:29 PM #2
I have been wondering the same exact thing. I have my grate completly flushed with the hull and rideplate and I saw a speed gain. It took alot of grinding and sanding but I was able to get it lined up.
Now I'm wondering about the rideplate and apparently the RXT and RXP have this issue. Mine steps down, and that has to cause drag. I made a thread called Ideal Rideplate and I was hoping for information to pop up their. Shibbs helped out with some of my questions but it would be nice to know if anyone has there rideplate smoothly lined up with the hull.
Even just shimming the back to line up with the hull would allow for an upward slope would allow for water flow to lift up the nose (less drag) and almost get rid of the need for a wedge which would help pump flow efficiency. Just need input or pics from people with rideplate/hull lined up and performance numbers, which I think is what you are seeking from this thread.
I though Jerry did a bunch of this work but he did it side by side with some other work and wasn't sure on the gain. Shibby did this work and saw a huge gain but it's unsure on rideplate or truing that did the work.
I also wish we could have pictures of people at top speed to see hull placement and angle in the water. I would think the rideplate are and maybe a foot or two above is a huge area for improvement. I mean hell we already see a mph or almost 2 from just skegs on the rideplate.
07-24-2006, 04:36 PM #3
if ur rideplate is lower then the hull, you are losing serious performance. very unusual for it to be like that on a stock machine from the factory, but it does vary depending on the pump support and pump shoe install.
most yamahas have a stepped design rideplate... meaning the rideplate sits alot HIGHER into the hull than the rest of the hull. this is how mine currently is, altho it also makes it damn near impossible to modify the cheesy thin riva grates to be dead flush now... u do open up a huge can of worms that is more than just simple sanding and slap it in. constant on and off, on and off, lining things up, etc.
better that the rideplate sit higher than lower in relation to the rest of the hull, jsut be cautious as this will promote a more squirelly feeling and/or porpoising has been my experience. u'll have alot more enhancing to do in the handling department to safely and stable-ly handle high speeds.
when modding the rideplate, you need to remove it completely and take the meat off the underside... don't jsut sand and sand the underside bc you WILL run into problems... like about 25+ bolt holes being revealed bc u just sanded deep enough to the bolt bottoms that hold the two halves together.
you could spend DAYSSSS on this part of the hull and still not be happy with how it came out, but u gotta draw the line somewhere.
07-24-2006, 07:21 PM #4
I like my rideplate. Its recessed from the hull. Always has been. Nothing like a built in step!
A step by the way causes airation. Real cool word. Just need it where it counts.
Damn, I like Bud Light....................just kinda smooths out the surface,,knowhatimean?
07-24-2006, 08:19 PM #5
we are using words like higher and lower. If I am looking under my ski. My hull is closer to me than my rideplate. Is my rideplate higher or lower than my hull. Higher?
07-24-2006, 09:49 PM #6
It is "recessed" compared to the hull
That's better than the ride plate "protruding" below the hull (into the path of water).
I agree Kinch... different terminology can easily change perceptions
07-24-2006, 10:12 PM #7
So with the rideplate recessed it can cause air bubbles ? and this is better than shimming it to have it even with the hull and have it angle more lifting the nose ?
07-24-2006, 10:38 PM #8Originally Posted by Kinchyle
Yes, it can "aerate" the water causing less drag, but as Hoss said, it's a science figuring out where to introduce the "bubbles". It can also reduce lift (hydrodynamics being ten-fold stronger than aerodynamics)... in the wrong place, this could lead to the bow dropping.
Less drag... or less lift
One thing for sure... you don't want the rideplate protuding lower than the hull.
07-24-2006, 10:44 PM #9
someone needs to strap a RXT/RXP into a clear tunnel and shoot water down it at 70mph so we can see what the water does.
Maybe see the pounds of pressure on the straps then do stuff to the hull and see if it changes the pressure on the straps
07-25-2006, 11:04 AM #10
My thought is that as differant as some of these skis are that it would have to be something in the hull, maybe the rideplate.
I doubt that it is in the engine. I mean for a ski to be 1-2 MPH faster by hp alone you are looking at quite a few add ons.
I know that my ski I feel is average, and my ride plate steps up in the back.
I wonder if bringing it down level with the hull would yeild more speed??
So what is differant about the faster ski's??
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