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View Full Version : Hook in the 16 Hull



Rootsy
04-12-2002, 10:39 AM
So that i don't sit and ponder this forever i am just gonna ask all of you that already KNOW! why does the 16 have a hook in the rear and not the 18? is the hook the single greatest speed killer and since i've never been in an 18 does the 18 chinewalk like the 16? the 18 is only 1 foot 4 inches longer, where did they put that length increase?... i know there's history and a good reason behind it... i just don't quite know what it is... so impart your knowledge oh wise ones... please... :)

mattyboy
04-12-2002, 11:14 AM
James,
I'm not an expert but from what I know the hook was to help it plane quickly and also to act as trim tabs @ slower speeds to stop the porpoiseing.
and @ WOT they were not in use as they were out of the water
I was also under the impression that the newer 16 did not have the hook.
when you talk about speed robbing, it's not the hook but the lack of hull that hurts.
my 16 at 55+ is so lite in the ass end I've come real close to spinning it out now twice.
Forrest is the guy you need to talk to from what I hear he's got the quickest 16, it's a trim/no trim, X dimension, and guts thing to go fast in the 16
sorta like driving a Cobra you turn heads,make noise go fast but it don't ride like your daddies oldsmobile!!!

Matt
Matt

Rootsy
04-12-2002, 11:26 AM
ok i typed too soon.. went back and searched the archives and learned a few things... the hook doesn't hurt the top end since it is out of the water... length to width etc etc etc... so maybe my question really needs to be the following...

my boat (1997) has a hook, no mistaking it... beyond that... it bowsteers at idle and the steering is tight and the transom assemble isn't loose... it porpoises (at any speed after planed if any trim is added and it chinewalks like crazy if you give it more than 2 or 3 taps on the trim anywhere above 50... SOOOOO where does the chinewalk come from and how is it eliminated or reduced short of taking trim out? although i have gotten kinda handy at driving out of it wink think i watn to understand it more than anything... knowledge is power!!!!

CDMA
04-12-2002, 11:27 AM
Do you have tabs?

Chris

Woodsy
04-12-2002, 11:30 AM
James...

They all bow steer... and to minimize the bow steer, the porpoising & chine walking you need tabs.... the tabs will also let the hull "think" its longer than it is.....

tabs, tabs, tabs,

Woodsy :D :D

CDMA
04-12-2002, 11:35 AM
This would fix it: :D

http://www.donzi.net/photos/callard43.jpg

Rootsy
04-12-2002, 11:37 AM
nope no tabs... guess thats a key eh... do they actually help that much???

SURE THING!!!.. fire it up Chris.. go big or stay home!!!!

Woodsy
04-12-2002, 11:46 AM
James...

as far as I am concerned, tabs on a Classic Donzi are a must.... once you figure out how much to drop a tab or tabs to correct whatever ill handling is bothering you, you will be much happier...

Bow Steering (low speeds) drop both tabs to induce drag, this will minimize the bow steer, but nothing really eliminates it....

Porpoising (any speed) drop both tabs slightly until porpoising goes away

Chine Walking (any speed) drop one tab slightly until condition goes away

List (any speed) drop tab on low side of list slightly until condition goes away

Tabs will cost you 1 or 2 mph top end, but your ride will be ALOT more controllable. Then you can up your HP, get rid of the hook in the hull and get more speed.

Woodsy :D :D

Rootsy
04-12-2002, 12:02 PM
Think i am gonna look into the tab thing... Thanks Guys... What would you suggest for tabs? how bout the new bennett M80's... 8 wide 10 long... if i can get it evened out and stable and add a tad more trim to level the prop out you might actually get a bit of speed or see no decrease... probabyl wishful thinkin eh! hmmmm maybe i should just sell it and get sagbays 18!!!!!

Right now, well by sunday.. 325hp @ prop... hook will probably stay unless someone gets me way drunked up one night and we break out the fiberglass and grinders...... eek!

turbo2256
04-12-2002, 12:14 PM
I would recomend the 110s k-planes by merc have broken to many bennets

mattyboy
04-12-2002, 12:20 PM
yeah the tabs help with ride but they also get dry on my boat @ wot, think it is the lift caused by the prop gonna experiment this spring with some new one's .brings up a good point where should the tabs be mounted, I've seen some out by the chine and some in closer to the keel?
good luck James

Matt

turbo2256
04-12-2002, 12:51 PM
Closer to the keel usally gives more control at high speeds be shure they clear the drive when fully turned.

CrackerJack
04-12-2002, 01:37 PM
I have a 16' Classic and installed Lenco tabs.
The reason was alot less cost and ease of installation. They work great, instant response
and able to stop the porpoising. I mounted them
in about 5" from the chine. Recommended was 1-4".
There was a step on my transom that I had to
work around. They stay wet even at wot and I don't have much hull in the water at that time.
The size I used was 9x12. I believe the Bennetts
are sized 12x9. They are the same only stated
opposite. Jack

RPD
04-12-2002, 09:48 PM
I've had the Lenco RT12x9 on order from boatersworld (who I rarely use) for over a month now... they keep telling me they are on the way... another week or so I'll go to the Bennet from West if they don't get them in... Turbo, what about the k-planes, where does one go to look at them?... anyway, thanks for the thread, I've had many second thoughts about trim tabs, my only complaints about the handling on my 16 are: maintaining speed at trick skiing speeds (low: 16-18 mph) which I know the tabs will help... and chinewalking !!!! my major problem, which I wasn't sure the tabs would help.

BigGrizzly
04-13-2002, 12:59 AM
I have all three classics 16, 18 and 22. my son has a 22ZX and i also just recently got rid of a 19 foot Dynasty and they all bow steer at idle. This is a caristic of the outdrive (especially on deep-V) single engine non dual prop configuration. Some Duo-prop types do also. A nose cone helps but only slightly. The tabs will help the porpoising. The chinewalk will be helped at the cost of speed. Don't trim so high. A quick note Our 16 doesn't have tabs and isn't going to get them.It is a all original unrestored 1966 Ski sporster with a H&M Ford(now repowered to a 302) a Volvo drive. The porppoise is due mostly to the rocker hull and the trim angle.

Randy

MOP
04-13-2002, 07:22 AM
Hi and good AM! Guys I have to argue the bow steering term. In actuality it is Tail Wag induced by the deep V hull wash on single out drive set ups. It is only slightly present on most dual instalations (seems to be totally gone on counter rotating set ups, nor is it present on any inboard set ups and V's with Gil type brackets which gets the gear case back out of the wash. And yes dropping one or both tabs which disturbs the flow off the hull makes darn near go away. There are quite a few of us in the group that have had the good fortune to test hundreds of boats in just about any bottom configuration imaginable, only deep vees do it.

Phil / Long Island

CnV & Family
04-15-2002, 06:32 AM
Pardon my ignorance... but I'm learning. I think this bow steer or tail wagging is what we experience while idling or creeping along.

Out little 16 is the first boat that I've ever noticed this occur on so I thought there may have been something wrong. Once past the 10+ mark the bow steer/tail wag goes away. Porpoising occurs from about 10-25MPH and I can usually (depending on the tank level) counter it with a slight throttle adjustment and stablize it. I've yet to experience chine walk, even at WOT, and from what I read I really do not want to experience it... :D I do note a tug to the left (i think) if I kill the throttle suddenly. But I've read this is normal as well...

Glad to know I wasn't imagining things and the Donzi has no hidden problems... :D

-C

clayman
04-15-2002, 07:46 AM
The thing that freaks me out, and really freaks out my wife , is what our 18 classic does in turns. When I am at maybe 1/2 to 3/4 throttle and in a nice gentle turn, the boat is banked over at a normal comfortable angle then all of a sudden it banks severely and I have to either countersteer or get off the throttle. I have never been in a boat that does that , Does any one else have this too? What do we call that?
James

clayman
04-15-2002, 07:49 AM
One more thing, what exactly is hook in the hull??? Does the 18 have it? should I blueprint the hull while am at this restoration and take out any bad , speed robbing bumps and wiggles??
James

Tony
04-15-2002, 07:59 AM
The big lean is typical of deep vee hulls when turning. To see the "hook" take a 4 foot level, or any other lengthy straightedge, and place it under the outside strake of the hull at the stern. It is slight but apparent when using a straightedge. I don't believe any 18's have it, only 16's. Do a search on "hook" and you will read what has been discussed in the past.

Taking it out is a matter of opinion, and, like lots of other topics, there is certainly no shortage of opinions on this board! What's neat is that these opinions come from guys with tons of experience dealing exactly with the situations discussed. That makes the opinions valid and trustworthy!

MOP
04-15-2002, 08:02 AM
Reply to James, I think most of us have had it happen in turns. My thought is that as you turn you encounter totaly different water angles due to waves which grately changes what we percieve to be a constant angle. I find when its glassy everything is pretty consistant, but as the chop builds everthing increasingly HAIRY!

Phil / Long Island

Rootsy
04-15-2002, 08:08 AM
freaked me out when i first got the boat too.. the turning thing.. you turn too sharp with too much speed and you feel like you are almost riding on the side of the boat... if it is too severe you'll almost get the prop out of water it'll suck in the air and you'll lose the speed and it'll come off plane... i only encounter this when i have good speed going and try to turn waaaay too sharp... as for the hook... only in the 16 i do believe... it's quite apparent if you look at the stern of the boat from the side, last foot and a half of teh chine looks like it is concave...

ToonaFish
04-15-2002, 09:06 PM
I had the most hideous time figuring out what the "hook" was... this photo from Owen makes it pretty clear.

http://www.donzi.net/photos/chowardowen.jpg

Forrest
04-16-2002, 09:11 AM
Me thinks there's a hook in that level!!! :p :D

turbo2256
04-16-2002, 09:31 AM
K-planes are from mercury marine and are what most racers use I stay away from the ones with plastic actuaters because they break to easy and are not recomended for use over 60 mph even the twin cylinder ones. The 110 s are the smallest they make which would be all you need. They are more expensive but i have never broke a set.

ALLAN BROWN
04-16-2002, 09:50 AM
Toona,

That ain't the hook that Jim Wynne patented. That is a cradle hook, and is VERY bad for performance.

Ranman
04-16-2002, 10:49 AM
The drastic lean while turning is much easier to induce when making a left turn (right hand drive boat) than a right although you can get it to happen turning either way. I found I can make a faster, tighter, and flatter turn when making a right. I assume this has to do with the prop rotation holding the boat flat during a right and trying to roll me over during a left. Is this correct?

Tidbart
04-16-2002, 11:23 AM
Hey Clayman, that is called handling. There are not too many boats out there that can do what the small Classics can do without kicking out the rearend. Play around with it and get used to it. You should be able to put the rub rail right in the water. It freaks my girlfriend out sometimes also, she thinks the boat is going to tip over. I believe you will only get this type of handling in the 16 or 18. The 22s are much longer and handle differently. It takes a little practice, eventually you will start doing it for fun. 18s RULE.

ToonaFish
04-16-2002, 06:38 PM
Thanks Brownie! I'm not sure which ship in Owen's fleet that is a picture of... I was envisioning a 'hook' as something on the order of a "J" shape and he was trying to set me straight when he sent me that picture.

Bunches,

Celene 'not a hooker til I get a Donzi'

RPD
04-16-2002, 08:34 PM
The roll when cornering is, as stated above, typical of V hulls, the deeper the V the more apparent.... The asymetry may be due to prop rotation but I think in most small boats it's simply a weight issue, if the driver is on the low side it it more apparent unless he has a passenger balanced on the other side.... as for the hook, it can be taken out but since it is mostly out of the water at WOT it probably doesn't hurt top speed much if any... (see previous discussions of this topic).... the hook is quite apparent visually on a 16, simply look at the last couple feet, right at the chine... the hook in the photo includes the first strake and I don't think that is the designed hook, but I'll have to go and look at mine to be sure.