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- Performance (http://www.classicseacraft.com/community/forumdisplay.php?f=5)

- - chine walk (http://www.classicseacraft.com/community/showthread.php?t=18363)

this afternoon, i rode in a buddies '75 20ft master angler with a closed transom and non flotation single armstrong bracket w/200hpdi. the boat ran great up to around 53mph, but when it trims out it really starts to dance- around 57mph it was uncontrollable and had to back off. no combination of tabs/motor trim helped. im in the process of building a '70 20ft SF that has already been enclosed with a hermco flotation bracket, and was curious about this chine walk. do all 20s have this problem over say 55mph or could it be a poor design with the enclosure and bracket? any input would be greatly appreciated!

NOT TO SEND YOU SOMEWHERE ELSE FOR INFO BUT SCREAMANDFLY.COM IS A SPEED SITE. BUT CHINE WALK OCCURS IN ANY BOAT WHEN YOU GO FAST. YOU CAN DRIVE THROUGH THE CHINE WALK BUT IT TAKES PRACTICE AND INSTRUCTION AND A CENTER CONSOLE FISHING BOAT THAT YOU ARE STANDING IN WOULD NOT BE GOOD PLACE TO LEARN THIS DRIVING SKILL. IT PRETTY TUFF EVEN IN A BASS BOAT IF YOUR JUST LEARNING. I HAVE A FRIEND THAT DRAG RACES IN ODBA DRAG BOAT ASS. AND HE COACHED ME THROUGH THIS DRIVING LEASON.
GOOD LUCK
AND HOPE THIS HELPS
RUSTY

its something that ive never really experienced though. ive been in 95mph in v-hulls, 135mph in cats and they will bounce from chine to chine, but still track straight. this gets squirrely going left to right, progressively more each time, and if you dont let off, it feels like the boat will dart to 1 direction, which would be very bad. i dont mind a little teeter from chine to chine, but the left to right stuff is scary...

I don't think that there are too many 50+ mph 20 seacraft around. I know props made a big difference in the handling of my 20MA. Bow lifting props specifically the Michigan Rapture gave my boat really squirrelly handling characteristics (at 40mph). The Mirage Plus and the Highfive gave the boat entirely different handling characteristics . . . The boat was rock solid up to 52mph with the mirage plus. You might try changing props . . .

The bracket is another variable which effects performance. I'm very pleased with the performance of my 20 seafari with a bracket up to it's top speed 48mph. I don't even have trim tabs and the ride is stable (mirage plus 17P, 26" setback, and 1.87 gear ratio). The weight of the seafari is further forward . . . but the hull really lifts out of the water as you can see in this photo (@ 35mph). You might have hit the threshold where you need bigger tabs or wedges . . . I'm sure the bracket and the additional weight hanging off the transom offsets the engineered balance of the hull. . . but I think you're probably charting new territory for the board as far as the behavior of a bracketed 20 above 55mph. Good Luck!! I'm interested to see what you come up with . . .

http://www.wellcraftv20.com/gallery/...023_Medium.jpg

This is a good thread with some info about props and chinewalk.

http://www.classicseacraft.com/forum...r=52369&Forum=,All_Forums,&Words=&Searchpage=0&Limit=25&Main=520 69&Search=true&where=&Name=2409&daterange=&newerva l=&newertype=&olderval=&oldertype=&bodyprev=#Post5 2369

Many time chine walk is caused by a motor that is to deep in the water - try raising it a bolt hole or two...

bigshrimpin, no that is not the boat. i have a feeling the bracket is mounted to high on this boat and the nonflotation really throws it off. at rest and trying to plane off, the exhaust is under water. but once up to speed, you can only trim so much before the motor cavitates.

last Friday I got my girl up to 58 MPH (new record for me) and I am fine at that speed providing that I keep a straight line and don't keep her there for too long

Besides at that speed I think that i am averaging less than 1 mile per gallon, whereas I get 1.7 to 1.8 at 40 MPH.

Quote:

CHINE WALK OCCURS IN ANY BOAT WHEN YOU GO FAST

Well, yes and no. or, not exactly. An Allison XB or XTB rarely chine-walks, and it has fairly definite hard chines. But look at the hull and notice the small transitions at the center pad.

Chine walking is caused by the hull being in an unstable hydrodynamic state. This is usually caused when transitioning from one hydrodynamic state to another, generally when the hull lifts/is forced higher in the water, and the primary hydroplaning surface is changed from one surface or pair of surfaces to another, usually from a wider planing surface and narrower together, to the narrower alone.

During that transition, the hull is not yet fully able to achieve primary plane on the smaller surface, but is going too fast to maintain stability on the wider an the narrower at one time. So it tries to plane on just 1/2 the wider surface and the narrower. That creates a turning, out of trim hydroplaning situation. We should all remember that an object in motion will travel in a straight line unless acted upon by an outside force, and the P factor from the motor and propeller act like a slightly out of balance gyroscope. So when the hull falls off from the smaller, narrower planing surface alone, and begins to plane on it AND one of the wider surfaces, whereupon the gyroscopic effect and forward momentum cause it to begin to right itself. But remember, we don't have enough speed to plane on the narrower surface alone, yet, so, the righting motion which began continues, forcing the hull to try to plane on the narrower surface, and the wider surface on the other side, and the sequence begins to repeat itself.

At this point, you can only do one of four things: 1, You can accelerate to a speed at which the smaller, narrower surface is capable of supporting the hull as the primary planing surface (called pushing through or driving through)
2, you can counteract the oscillation with predictive steering input (a necessary part of pushing through),
3, you can reduce speed until the hull regains stability, or
4, you can bail out at very high speeds, either voluntarily or involuntarily.

Quote:

A CENTER CONSOLE FISHING BOAT THAT YOU ARE STANDING IN WOULD NOT BE GOOD PLACE TO LEARN THIS DRIVING SKILL.

Actually, a center console is the BEST place to learn to handle chine-walk, provided you have a stand-up wrap-around racing bolster. With your feet set about shoulder-width apart, you can feel and predict the hull oscillation much better than if you are seated. The danger with a chine-walking center-console is losing balance and/or grip on the controls as oscillation increases. If you are flung sideways, over you go. That danger is lessened quite a bit when you are seated in a wrap-around seat bolster.

I began racing hydroplanes 40 years ago as a boy, since the days of the spade-hulled "B" outboard "knee-boats" with a Mark 7 Merc. I've driven a wide variety of boats at great speeds, and crewed offshore racing powerboats of 22' and 30' as a throttleman and driver, and I've driven on the water at speeds greater than 100 mph. That's my credentials.

So, given the option, for learning or teaching purposes, I would choose a center console with stand-up racing bolsters.

Two more things Fr. Frank,

Stirrups and a kill lanyard. ;)

See ya, Ken

You guys are all nuts pushing a 20' boat that fast!

I remember my boat started to "Chin Walk". Thats when you launch off a good sized wave and your "Chin Walks" from Starboard side and slams on something on the Port side! :D

Quote:

I began racing hydroplanes 40 years ago as a boy, since the days of the spade-hulled "B" outboard "knee-boats" with a Mark 7 Merc. I've driven a wide variety of boats at great speeds, and crewed offshore racing powerboats of 22' and 30' as a throttleman and driver, and I've driven on the water at speeds greater than 100 mph. That's my credentials.

Fr. Frank curious on when you joined the priesthood?
Was it during or after or both? :)

- Nick

Quote:

Stirrups and a kill lanyard.

ABSOLUTELY!

cSickNick said

Quote:

curious on when you joined the priesthood? Was it during or after or both?

Long after. I became a priest in 2000. I stopped trying to exceed the speed of (fill in the blank) on the water back in '86. I learned that no matter how fast you go, you can still hear yourself grunt and scream as your body bounces and skips across the water at 80+ mph :D

Yes, it was MY body.

Why would anyone want to go that fast in a 20foot SeaCraft?I hit 50 one time in my skiff in a foot of water on a slick calm day and it scared the you know what out of me.I guess I'm getting old!

I don't really like going too fast, but I sure do like a 35mph cruise when I have to go long distances.

Quote:

Why would anyone want to go that fast in a 20foot SeaCraft?I hit 50 one time in my skiff in a foot of water on a slick calm day and it scared the you know what out of me.I guess I'm getting old!

You can say what you want about controlling chinewalk at that speed, but that hull was not designed for that speed. Somebody is going to get hurt...

Quote:

Why would anyone want to go that fast in a 20foot SeaCraft?I hit 50 one time in my skiff in a foot of water on a slick calm day and it scared the you know what out of me.I guess I'm getting old!

You can say what you want about controlling chinewalk at that speed, but that hull was not designed for that speed. Somebody is going to get hurt...

I really hesitate to post on this, butIMHO, either the guy going 55+ mph in an old 20' seacraft doesn't know that he is exceding the design and safety limits of that boat, or he has a death wish.

staying on topic.

what i am trying to figure out is how much bracket postition/flotation and motor weight/prop/trim/shaft length play into causing this chine walk on this hull. i really appreciate the on topic input so far, i just want to do all i can in setting up this hull to help relieve the chine walk.

Well i dont know if it matters but i have a 73 20 SF with the original 20" transum and a 225 EFI merc and im hitting 69MPH on a GPS. And without the wind, chop, and weight on boat, being perfect I'm chine walking pretty easy at 3/4 throttle.

Ok that is probably faster than anyone needs to go BUT, with his statement that the motor can't be trimmed much and he thinks the bracket may be too high - is it possible that the nose actually is not high enough and the boat is running too flat thereby causing the chime walk ??? Dr Frank

I beg to differ with you guys.....
But when Mr. Moesly was in "My 20SF at Anclote"
His words to me and keep in mind, He
Invented, designed, and patented our boats.
THEY WERE DESIGNED TO BE RUN HARD AND FAST !!!!!!!!!!!!
Sooooooooo, with that thought, being I top out above 60mph
with my 20 SF. He knows what these boats will take...
And they will take it!!!!!!
And his lovely wife Jeanne also who raced these boats while
most of us were just wet behind our ears......
I do not recommend for the novas or weak at heart to
try to run these boats at that speed. You have to know your limits in what you can handle. I did not just jump in my boat and go balls to the walls without knowing what I and the boat could handle!!!!
End of story! :)
http://i7.photobucket.com/albums/y273/krn54/a11.jpg
http://i7.photobucket.com/albums/y273/krn54/a10.jpg
See ya, Ken

i dont think his boat was running too flat. when it ran flat and the bow was in the water, it ran great, just couldnt get any more than 52-53mph at the same rpm. thats motor down and no tab. trim the motor with no or little tab, and the boat instantly lifts and picks up 3mph, and a few seconds later starts to walk. if you tab the boat flat and trim the motor to rev, it cavitates. this particular boat probably needs a 30", but surely that cant be the end all? i should have enough motor to run 60 with the tabs buried, but i really want to be able to stretch it out if conditions permit.

Quote:

is it possible that the nose actually is not high enough and the boat is running too flat thereby causing the chime walk ?

The chine walk may be exaggerated by a nose high position, but probably not by a stern high or flatter planing pitch, unless only one side of the center deadrise angle has some serious hook in it, like 1/16" to 1/8" per foot in the aftermost 5' of the hull.

As the hull speed increases, it tries to find the point of least resistance, and rises up out of the water until only the aftermost center of the hull is the primary planing surface. The problem with that is the transitions, and the fact that a pure V is inherently unstable. It wants to fall off to one side or the other and plane on the smaller flat surface on one side of the V, rather than the whole V. A VDH hull running flatter, or nose lower, will be more stable than one running nose high, because it will plane on more than just the center angle.

would overpowering the hull speed the process up and plane out sooner, or make it worse? im looking at a 25" 300hpdi.

mikeym, I'm over in Bluffton and would like to check out your operation. I'm over in Thunderbolt pretty often at Southeast Boatworks where the two-seater Champ Boat series hydro is kept. I'll be working with the promoter for the race on River Street Nov. 3rd and 4th. I could come to Sav. by SeaCraft, or if you really want to experience chine walking I'll bring a 15 Whaler w/jack plate and F60. Talk about violent! Thank God for kill switch lanyards. More important than the one in our Jersey Speed Skiff! Part II.