Thread: What causes the GPR to rock?
06-18-2007, 11:21 PM #1
- Join Date
- Nov 2006
What causes the GPR to rock?
What causes the GPR to rock at certain speeds? 'As if it's trying to balancing itself on the keel.
Is my craft a "chine walker"? Any way to elimnate this?
06-19-2007, 01:55 AM #2
- Join Date
- Jul 2006
When mine was stock it was bad to do that but it has'nt done it in the last couple years. I beleive it was stepping the sponsons that fixed it.
When the boat is at a slow cruising speed it will be fine for a little while then once a sponson hits the water it pushes that side of the boat up which tilts it to the other side and that sponson pushes it back over and it just goes back and fourth like a pendulum. When the sponsons are stepped the rear of the sponson touches the water or is real close at a slower cruising speed reducing the pendulum effect. At top speed the sponsons dont really touch the water but it is still more stable (I think its because of the spray hitting the rear) others say its due to lift, but I guess it doesnt matter why it works, it just does.
06-19-2007, 03:16 AM #3
You are going to think I'm absolutely out of my mind, but I LOVE it when I can get the gpr to do this, without loosing pump suction. I just balance it and let it do it's dance, back and forth. Wooooohoooooooooo
It's a form of chine walking, but you have to have it at the "right" speed, with just the right amount of rough water, and your balance point in just the right place...otherwise it smooths back out to the standard gpr boring ride.
06-19-2007, 05:57 AM #4
Shimming the trim tabs down will stop it from rocking but, you might lose some of your top speed.
06-19-2007, 07:55 AM #5
Chine walking is a good thing, it means your hull is trying to lift itself out of the water. Make it happy - go faster! All GPR hulls want to chine walk from 25-35 MPH or so, but as others have said various things can be done that will minimize it. Don't change anything just to make the chine walk go away, though! I ride in rough water so have stepped sponsons, shimmed tabs, etc. With a few of the new tricks that are available now (such as Jim's FF mod and Danny's sponsons) the chine walk is back, my ski is faster, and I'm happier.
So... be like hydro... balance some pancakes on your head and enjoy the ride!
06-19-2007, 08:31 AM #6
mine does this to. but here is a good question???
when I get right over 75 the back of the ski slowley rocks left to right. what causes this?
06-19-2007, 09:10 AM #7
Thats what I thought they were talking about.
I call it my GPR-Happy-Dance.
06-19-2007, 01:38 PM #8
Back when Kerry was down here a couple of years ago...we were riding in some smooth, real smooth water...he looked at me and I looked at him and he said "I wish we could find some good GPR water.." Meaning if it's a little 4" chop and your ski is set-up right, you will go faster. If you are doing the Mudbug morning glass then you will have some chine walk. I believe Stan is the master at using this "walk" to go faster as he picks a side to ride on using his weight..shifts the ski more to one side or the other.
I really don't know how Stan does it..I have tried to emulate him..but no go.
I figured Mark would dig this GPR dance.... he's dangerous like that.
06-19-2007, 04:09 PM #9
- Join Date
- Nov 2006
After this weekend I've christened the GPR "chine walker". I noticed this in semi-rough water @ 30-35 mph; once the speed increased it disappered. It's a strange thing: first @ 30-35 you get CW, then @ 35-45 there's that up & down over the chop, finally as you top out, she skims over the wave tops with little fuss. This thing has many personalities.
For the record, the ski has stock stepped sponsons & a Shredmaster plate.
Thanks for everybodies input,
06-19-2007, 06:51 PM #10
Well i can say this about the "chine walk" I Like it My gpr does it about 82mph and starts pickin up speed.Once it hits 7310rpm's I start looking for the "WARP ZONE" directly. I run stepped sponsons 1 inch angle and no tabs 800 grate..... Ya just gotta hang on and let that hull do its "Dance" !
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