Higher speed wobble
Printed From: CorrectCraftFan.com
Category: General Correct Craft Discussion
Forum Name: General Discussion
Forum Discription: Anything Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=49482
Printed Date: March-04-2025 at 11:24am
Topic: Higher speed wobble
Posted By: Bluebarron
Subject: Higher speed wobble
Date Posted: December-13-2020 at 7:36pm
| I recently purchased a 1994 Correct craft Sport Nautique with a 351. When the boat reaches about 34 mph it begins to rock and feel like it’s twisting to the right. Very unstable. It feels like it’s getting on plane plane but very wobbly. Around 40+ The boat gets very unstable. I’m trying to figure out the cause. My thought is it may be a bent shaft or prop. Yes either or it’s not very noticeable. The prop does have some damage but appears slight. Any thoughts or suggestions? |
Replies:
Posted By: 8122pbrainard
Date Posted: December-13-2020 at 7:58pm
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Chad, Welcome to CCfan. Glad you found us. On the wobble, check to see if there's play in the steering especially in the helm itself. If there is play, there are means of removing it. Then at the rudder, check to make sure the rudder post is firmly attached to the tiller arm. Then also the cable linkage to the tiller arm.
------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: MechGaT
Date Posted: December-13-2020 at 8:03pm
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The tolerance on a shaft is 0.003” of runout. You won’t be able to see that, you would have to measure it. If you are seeing damage to the prop that is bad from the imbalance it causes as well as it could indicate damage to the rest of the running gear. Sounds like it is new to you so I would recommend checking shaft straightness and having your prop repaired. Probably should check alignment as well. Don’t know that it is the cause of twisting to the right at 34, but prop damage is a red flag. ------------- '92 Sport Nautique |
Posted By: 8122pbrainard
Date Posted: December-15-2020 at 9:06am
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Chad, Certainly not a bad idea to check for a bend prop shaft or bad prop but I doubt ether will cause the wobble you describe. A bent shaft and or a bad prop will tpically just cause bad vibrations. On the wobble,one other thing to check is the tracking fin at the keel forward of the strut. . Does the boat have a tunable rudder? If it does, you may want to consider adding some preload to the rudder. Without a preload, a hull may not track a straight line. The tunable rudder came around due to maintaining a straight line down a slalom course.
------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: samudj01
Date Posted: December-15-2020 at 5:11pm
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Question on preload...which way should the tunable part of the rudder point towards for the preload? Does it depend on the prop rotation? ------------- 78 Ski Tique, 72 Skier w/302's, 93 SN w/351 & 17 GS22 w/zr409 Previous - 99 Sport Nautique w/GT40 and 87 Martinique w/351 |
Posted By: 75 Tique
Date Posted: December-15-2020 at 8:19pm
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David, Not an expert on this and I am sure there are some on here that are and will set me straight and answer your question. Right rotation (like our CCs) pull to the left, Left rotation boats pull to the right. So it follows that if you want absolutely straight (i.e. no pull) you would point the tab to the right a bit to compensate for the pull to the left. Serious course skiers (well, actually drivers) like a little preload, so that a straight line can be kept just by applying downward pressure on the wheel with one hand. If compensation of boat direction due to the skier's pull is needed, it is achieved just by releasing or adding pressure to the wheel. Congrats on Miss April. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: 8122pbrainard
Date Posted: December-16-2020 at 7:24am
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David, I too am not an expert on the direction of preload but what Larry has stated sure sound logical to me. Let's wait and see if anyone else has some input. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: TRBenj
Date Posted: December-16-2020 at 7:28am
| I’ve had one and can’t recall which way it was tuned but Larry’s mental gymnastics sure sound logical to me... except David’s likely got a LH prop on the new rig, no? |
Posted By: KENO
Date Posted: December-16-2020 at 7:49am
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I kinda figure that since they put an adjustable rudder on his new boat, they must have put something about adjusting it in the owners manual Click on the link and go to page 7-18
 http://www.planetnautique.com/CorrectCraftManuals/2017/2017-super-air.pdf" rel="nofollow - link |
Posted By: Riley
Date Posted: December-16-2020 at 8:03am
| Has the hull been worked on? Does it have stock rudder port and other underwater gear? |
Posted By: samudj01
Date Posted: December-16-2020 at 8:11am
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Correct in the left hand prop and thanks for the link. I have my hard copy manual and that looks just like it. Some info but mainly trial and error unless your boat is pulling to one side already. Mine is currently set dead straight which begged my question if it should correlate with prop rotation. I’ll go with Larry’s thoughts for my first change. I really don’t have an issue at speed but plan to offset slightly like my old boat was. This boat does not like to drive straight at idle which I’m hoping to be fixed with this adjustment too. Not sure it will. Original poster, sorry for the hijack. Back to your question. I agree that shaft runout and prop would probably create vibration and not your issue. I like the suggestions of checking rudder first. We had some issues with our ski tique acting squirrelly coming off the throttle and we had a loose rudder. Drove great otherwise. Also tracking fin and hull work could be issues. ------------- 78 Ski Tique, 72 Skier w/302's, 93 SN w/351 & 17 GS22 w/zr409 Previous - 99 Sport Nautique w/GT40 and 87 Martinique w/351 |
Posted By: 75 Tique
Date Posted: December-16-2020 at 8:19am
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Sounds like my logic may have been sound, except for the fact that I forgot David was referring to his new boat, which for some reason didnt occur to me, also which, if you havent seen it, is a beautiful boat. (Not sure I would have known it rotated left anyway) Since I didnt get up there much this summer due to Greg's broken wing, I never saw it in action. I assume you are happy with it, David. Seems like the perfect boat for your purposes.
------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: Riley
Date Posted: December-16-2020 at 8:29am
| Nautique is turning out boats with LH props? like Malibu has always done? How do they do that, reduction trans into VDrive with standard rotation engine? |
Posted By: Bluebarron
Date Posted: December-16-2020 at 8:36am
| Thank you to everyone who gave their input. You guys know your stuff. My mechanic took a look at it and said there is a missing skeg which is likely to be causing the wobble. There should be three and there are only two. He’s ordered one, and I will update on the result. |
Posted By: 75 Tique
Date Posted: December-16-2020 at 10:31am
It would appear, based on reading Ken's link, that I, and those of you that said what I said makes sense, were incorrect, despite the sound logic. Doesnt make sense to me, but what do I know. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: Morfoot
Date Posted: December-16-2020 at 11:17am
What doesn't make sense Larry? The tuning of the tab on the Rudder? ------------- "Morfoot; He can ski. He can wakeboard.He can cook chicken.He can create his own self-named beverage, & can also apparently fly. A man of many talents."72 Mustang "Kermit",88 SN Miss Scarlett, 99 SN "Sherman" |
75 Tique wrote:Posted By: 75 Tique
Date Posted: December-16-2020 at 11:47am
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Just seems counter intuitive Tim. Guidance says if boat is pulling to the left, you rotate the tab to the left. I would think you would rotate it to the right to offset the pull to the left. But like I said, what do I know. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: 8122pbrainard
Date Posted: December-16-2020 at 12:27pm
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Yes, I thought the manual instructions were very vague since they didn't mention anything about prop rotation causing a pull to ether direction. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: 75 Tique
Date Posted: December-16-2020 at 12:46pm
That being said, it is a manual for a GS20 and likely assumes a left hand rotation. Also, I am guessing, just the aerodynamics (hydrodynamics?) of the tab do not change with prop direction. They say, if the boat pulls left, turn tab left and if right, turn it right, independent of prop rotation. Maybe? ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: TRBenj
Date Posted: December-16-2020 at 1:04pm
Since ~2006 on the v-drives. Change must be related to the change in v-drive type, maybe from Walters to the PCM box. ~92-05 v-drives used Lh engines and rh props, prior to that used rh engines and props. LH on both since 06. All use 1:1 transmissions with the only reduction being in the vee, AFAIK. |
Posted By: Morfoot
Date Posted: December-16-2020 at 2:09pm
Its fluid dynamics in this case. By tweeking the rudder just a touch with a trim tab you're adjusting the direction the water traveling over the rudder just enough compensate for the reason the boat is "out of alignment". So instead of turning the wheel ever so slightly to maintain course....the trim tab does it for you. The water traveling over the tab sticking out to the left is going to force the trailing edge of the rudder to the right correcting course. Airplane rudders use the same principal to maintain heading except they can adjust it left or right from the cockpit depending on which way she wants to fly off course. Depending on cross winds and they way she wants to fly on any given day; the pilots can add none, a little, or a lot of trim to keep her flying straight.
------------- "Morfoot; He can ski. He can wakeboard.He can cook chicken.He can create his own self-named beverage, & can also apparently fly. A man of many talents."72 Mustang "Kermit",88 SN Miss Scarlett, 99 SN "Sherman" |
Posted By: 75 Tique
Date Posted: December-16-2020 at 2:46pm
I was picturing that cause/effect in my mind and figured it must be something like that but couldnt get past the idea that the tab was like a little mini rudder, and when tweaked left was forcing water left and therefore the front of the boat more to the left. Your confirming my alternative understanding helped. I assumed it was comparable to airplane dynamics and I have been told you know something about airplanes so I trust your interpretation. ------------- _____________ “So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
Posted By: 8122pbrainard
Date Posted: December-16-2020 at 3:32pm
Larry, I wouln't believe anything Tim has to say since I don't think he knows anything regarding aerodynamics  ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: DVskier
Date Posted: December-16-2020 at 4:52pm
| On my 2004 SN 196 I have the I have the tunable foil slightly to the port side of the rudder. This gives me the right amount of rudder torque to suit my needs. Tracks like a freight train through the course. Everyone has different perceptions when it comes to rudder torque. Very simple to change unlike having to file the training edge of the rudder. |
Posted By: Morfoot
Date Posted: December-17-2020 at 5:50am
I might know a thing or two about airplanes....maybe even three and the FAA hasn't revoked my license as of yet so all those airplanes out there that have parts fixed with some "Foot Magic" must be holding up. Pete....  . I love you too man!  ------------- "Morfoot; He can ski. He can wakeboard.He can cook chicken.He can create his own self-named beverage, & can also apparently fly. A man of many talents."72 Mustang "Kermit",88 SN Miss Scarlett, 99 SN "Sherman" |
Posted By: KENO
Date Posted: December-17-2020 at 7:44am
I'd say you.ve got it all figured out and understood Larry The diagram and instructions work no matter which way the prop rotates. BTW, If you look in the owners manual for a RH rotating Ski Nautique, you'll find the same diagram to help back that up. It's also pretty easy to find that patent that's referenced at the bottom of the page for some more reading.
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