goldberg007

I recently purchased an 03 Shockwave 25ft Tremor that was purchased new with the 575sci/Bravo XR1. It's moored up at the lake right now but I believe it has a 28 pitch Bravo I prop. I grew up on boats so this is nothing new but the chine walk about 75mph+ is.

It has the Dana 1000 tabs on it which i thought would prevent it from walking. I'm sure they do help but I starts walking pretty bad once you get close to 75. I've had it touch 86 but at that point its walking so bad you have to slow down.

Any thoughts on how i can prevent the chine walk? Would a prop change help? I think I could actually push a 30 pitch prop because I'm at 5200 rpm at about 84mph but with as much walking as it does whats the point?

Any input is appreciated..

Too Stroked

Ah yes, chine walk. The dark little secret of many non-stepped v-bottom hulls. Get's your attention doesn't it? It's soiled many pairs of underwear over the years. It's also great for keeping a certain muscle in your bottom well toned from puckering up.

There are a number of things you can do to minimize it, but you may never end up getting rid of all of it. The first thing you want to check is your steering. Is it stock? Is there any play in it? Is it hydraulic?

The reason I'd start with your steering is that if you have any play at all, it's going to make the chine walking worse because the drive will literally be flopping around side to side. Worse yet, the more it flops around, the worse the slop (and the chine walking) will get. At the speed your boat runs, you should have full hydraulic steering.

Another thing that sometimes works - but apparently not for you - is dropping both tabs just a bit. The problem with this is the more you drop them to reduce chine walking, the more speed you loose.

One of the more time tested cures - if your steering is in top notch condition - is driving your way through it. As the hull lays over on its port side, steer slightly to starboard. If you have hydraulic steering, with some practice you can use fairly minute steering corrections to keep the boat from chine walking - or at least minimize it.

andychb

+2 on steering input..... My 25' chine walks like crazy over 80( I have hydraulic steering..it does help) some steering input and correct trim usually cures it. Mess around with it until you find what works on your boat.

Jimboat

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Jimboat

Chine walk is pretty common on performance hulls like yours.
As the hull accelerates, lift increases and the wetted running surfaces that are required to support the hull are reduced (more Speed = more Lift = less Surface). As the speed increases throughout the velocity range, the hull often gets to a point where the lifting surfaces become very much reduced and the hull is now "balancing" on a small area of the vee-portion or the "vee-pad" of the hull.

When that surface becomes sufficiently small, it becomes very tricky to "balance" the hull on its vee or pad. The result is a rocking of the hull from side-to-side. This rocking can tend to get a little more extreme with each motion, and so the "balancing" must then be provided by additional driver (steering/throttle/trim) input in order to maintain the hull in a balanced state.
With some driver input, the condition can be stabilized. With changes to hull setup and/or changes to the driving technique the condition can be alleviated.

Chine walking is predominantly characteristic of vee-hulls with deep Vees (more deadrise), hulls with deep or narrow running pads and hulls, with a Veed pad or no pad (straight vee). These bottom designs are just more inherently difficult to balance at higher speeds. Another contribution to chine walking can be seen at higher speeds from "propeller slap" (usually seen more with props of fewer blades). As the prop turns, each blade enters the water and another exits the water. This irregular in/out of every blade, changes the dynamic forces at the location of the propshaft, repeatedly putting an imbalance on a hull that is trying desperately to balance on it's vee or pad, and ultimately initiates chine walking.

Setup of your hull and driver "seat-time" are the best solutions to the problem. Usually an alteration to the hull, or hull setup and/or modification to your driving methods (read seat-time) will improve the problem.

Some established steps toward minimizing chine walking include:
1. Check & adjust steering
2. Use solid mounts
3. Clean Hull Lines
4. Weight balance of hull
5. Motor height
6. Propeller selection
7. Seat time (experience)
8. Minimize Trim Angle

Summary: Optimize Hull Setup and Driver "seat-time"!
Some established steps toward minimizing chine walking include:

Also, see full article on "Chine Walk"

/Jimboat
AeroMarine Research
'Secrets of Tunnel Boat Design' book
'Vee Pad Design' paper
'Tunnel Boat Design' software V7.14 with "Vee Hull Design" & "Porpoise Analysis"

Steamin Rice

If you have not already done so, you may want to call Shockwave and see what they say. The 25 doesn't really have a reputation of being a 'driver's boat' so to speak, so maybe they can help you figure this out.

goldberg007

Well, went back up to the lake and took the boat out a few times. Again, I've been around boats my whole life but not 75+mph boats really. This boat doesn't have hydraulic steering. Why in the world would the original owner special order this boat with a 575sci and not include hydraulic steering?

He ordered Dana 1000 trim tabs and Dana seat brackets and had everything anodized red to match but no steering. Am I wrong in saying that the reason that boat walks like crazy once it gets close to 80mph is because it doesn't have Hydraulic steering? You would think the trim tabs being like 14" long would help but obviously not enough..

precisiondetails

You are correct on it needing hydraulic steering, but then u will need some seat time on driving it!

Randy Nielsen

iTrader: (4)

My Eliminator 25 Eagle does the same thing above 80mph. I have been told everything from a standoff box to K planes to a blackhawk drive will cure this all from such noted professionals as Tom Dick & Harry on the dock. I have a buddy with the same hull as mine only a stock 502 & 2" Imco shorty his boat tops out at about 80 & running side by side there is only about 2 feet of hull touching the water if that. I have about 200 more hp, teague platinum 2" shorty, add on hydraulic steering,& a 30 pitch labbed bravo 4 blade prop. I am definately interested in this thread cause my seat cushion has grab marks on it & I would like to fix it the first time instead of experimenting. Not trying to hijack but the boats sound pretty similar. Randy

LTZCrew

So i got this beast now and have come into some of the same issues, she runs hard but as you trim up to get the motor to rev out and kill some of the lysting, i think it becomes over trimmed and over lifted. the tremor has full length strakes right to the transom and where they are on the hull combined with the boat being set up with ITS - from what i gather it can add to stern lift??? - it gets to high out of the water and chines, trim it right down and it smartens up but kills speed, same with setting the tabs to just touch the water, am i out to lunch here or could i be on the right track? maybe add wings to her like a vector and let it fly?