Slalom boat Trim tabs

[Justin]

What are thoughts on adding a small, single trim tab on the transom of an older ski boat to change the wake? I have played with weighting the bow and lightening the rear of the boat which seems to make the wake smaller / better, so I am thinking why wouldn't a trim tab help by lifting the transom at speed and lowering the bow? Seems like a fairly cheap way to go without adding weight to the bow. Has anyone played with this? Jody??

And upgrading to a new boat is not an option.

[oldjeep]

 

That is basically the way the factory moomba v-drives were set up the last time I looked at them. One huge trim tab that can be used to force the bow down and smooth out the wake. Also the same basic principle of those fixed plates fore barefooting.

 

 

Problem is that experimenting requires drilling holes.

[nzwaterski]

My 1996 tige2000 has the taps system works great flattens the wake out to be as good as any late model ski boat

[slvrbulit]

So do you adjust the tab all the way down for a better ski wake?

[nzwaterski]

Yep . Haven't seen what angle it goes to but it sure does work

[oldjeep]

Wouldn't be all the way down, more likely that it would be pretty close to inline with hull bottom. In the case of the moomba it is also what they use to enhance the wake for wakeboarding. What it does all depends on position and ballast.

[nzwaterski]

Well have a look today. To see what angle is at.

[Ed_Johnson]

@nzwaterski .... He is absolutely right..Back around 95, someone brought a Tige with the trim tab system over to Hawaii where we lived..It was better than my 94 MC Prostar at the time. Plus fit and finish on that boat was the best I had ever seen.

[Wayne]

I used the Scarpa Supression Plate (a Ron Scarpa improvised device for Malibus which was essentially a trim tab) on my 2002 Sunsetter. It had both positive and negative effects. At sub 32 MPH speeds it helped knock the wake down quite a bit which is where my wife skis. At 34 MPH and over it made the wake smaller but the crests were a little firmer and the table filled in between the wakes. At the time I was skiing long line (unfortunately back there again) so I remember that I had "2 bumps" when crossing the wake prior to the trim tab. After I put it on there was a "bump" up on the first wake and the second one was kind of a "bump" down. It also seemed to help with 22 off rooster tail.

 

Now all my findings are isolated to that one boat but it was an overall improvement. I know some of the early Malibu Sunsetters or Euro F3 or Malibu Skier had them factory. Those models kind of fade into each other for me from the early 90's. They are certainly a tuning tool worth trying for older hulls.

[Justin]

Thanks guys, yes this is for a 95' Nautique. Not a lot of room with the exhaust location but I may do some experimenting. I would be surprised if this has not been done before on a 90's Nautique.

[rodltg2]

It doesn't seem like that hull would allow for a trim tab.

[Ed_Johnson]

They have Dual Trim tabs you can purchase, one for each side, which would also help in leveling the boat due to load...You don't necessarily have to have one in the middle.

[Justin]

Yes, read somewhere using 2 tabs, 1 on each side reduces the rooster size.

[DW]

@Justin: You could also consider adding some lifting chines/longitudinal strakes and/or also look at adding some hook to the transom (usually done with bondo).

[Greg Banish]

I have a single center tab on the transom of my PS214. It certainly helps the wake at 30-32mph by getting the two rear corners a little further out of the water and pushing the nose in a little more.

[ToddL]

FWIW, it is my understanding that many of the boats which had trim tabs as part of their original design also had hulls which were designed to sit deeper when the tabs were not engaged. In most cases the hull was designed for wake sports when tabs were not engaged and smaller wakes with them engaged.

 

Therefore, adding tabs to a hull which was not designed for them might not achieve the intended result. It is possible that tabs might affect tracking and stability of a hull which was designed to work without them. Also, consider that hulls designed for tabs are likely reinforced at the location of the tab and hydraulic strut mounting points. If you chose to add trim tabs to a hull which wasn't originally designed for them, please consider these aspects.

[RRGR]

I have a 2013 VTX (diamond hull) and am contemplating putting on some trim tabs. Open water skiing, 32/34 @ 14.25.

 

This is in an effort to make a few changes to get the best slalom wake I can. I wanted a TXi, but the wife wouldn’t go for the DD layout. I’ve taken a look at a couple of sites including this one and have seen some pretty good posts, and they seem to somewhat agree that lifting the stern a bit provides a better wake.

 

It seems that the “wake” oriented boats have the single center tab, but having the power wedge would limit the size of a center mounted tab, if it could be done.

 

There are some good kits, but before I go and start drilling into the hull, I wanted to see if anyone had any experience putting two tabs and having a better slalom wake.

 

Additionally, any thoughts on how much the shape and size of the tabs would make a difference? I know some of the aftermarket surf tab guys ran through a ton of prototypes.

 

FWIIW this kit has caught my eye, but I might try to buy it without the tabs so I can experiment a bit.

 

https://www.imarineusa.com/BennettTrimTabsM120ATP.aspx?gclid=EAIaIQobChMIyfDOiNvl5AIVF73sCh28rAA3EAQYByABEgKaPPD_BwE

 

[DW]

Someone once commented to me that when they were tuning a hull, they used bondo spreaders taped to the hull with shrink wrap tape. Did it this way to avoid the typical bondo hull tuning technique. It might be an inexpensive way of testing your changes to see how well they work.

[skihart]

If you have ever looked at the hydro gate on a 200 SN you would be surprised at how little change is needed to make the slalom wake amazing. The amount of surface area on aluminum plate that drops down is surprisingly small. When you are driving and drop the gate the effect is pretty pronounced.

I don’t think you would need a huge wake plate to make a significant difference to the wake at speed.

[iceboating]

Interesting video.

[Skierx]

@Justin this is a 84 mastercraft I have. I cut schedule 80 CPVC plastic pipe. Plastic welded together and epoxied it to the transom. To knock down the spray the power slot was creating and it ended up as secondary benefit it made the wakes even smaller by lifting the back of the boat. I made sure to mount it a little higher than the bottom of the hull so as to not create a wedge effect. also added spray rails to the side to knock down the side spray this boat is known for. epoxied that on too. No drilling extra holes in the boat.

 

[skiinxs]

If you are contemplating adding hook, you can simulate the effect of the hook by beads of silicone at the back edges of the bottom. Surprisingly, once cured it will stay on long enough to test the result. Once you find the amount and location of hook that works, you can duplicate with fiberglass (or bondo if that is all you can work with).

[ReallyGottaSki]

@Skierx cool solution! I also run the oj 4-force on my 82 supreme and they do throw quite the frothy mess.

I'll be adding a plate of some sort over the winter to knock some turbulence down and add very mild lift with turnbuckle adjustment much like the sanger hardware.

 

Seeing our hulls parallel some lineage, I am very interested in seeing your spray rail solution in more detail!

 

I took 141# out of the engine this year with good results and excited to keep the tinkering going.

[DW]

@Skierx - second the comment on pix of the spray rails, a friend has an 85 S&S that could use them.

@ReallyGottaSki - nice, what specifics on the engine weight reduction. Keep going, every pound helps:-)

[Skierx]

@ReallyGottaSki I purchased smart rail from integrity Marine. Kind of pricey. Only 1.5" wide . It did help nock the side spray down but I think I may add a little more to it. The newer boats Malibu, nautique and mastercraft all have 3" to 4" wide bottom of the hull . This will work the same way.My dads 1966 Century resorter had 1.5" spray rail. Chriscraft had 5" spray rail on at least one of their models.

 

[Alberto Soares]

[jalama]

I added a Bennett trim tab to my Sanger v210. It helped soften the wake and removed the hard lip at 15 off 32mph. I just free ski so I stick to that length. There is a bit of a rooster tail at 22 off but that was there before I installed the tab. Not sure how it affects shorter lines. As others have said, it really depends on the boat. The tab also greatly improved the rough water ride. I put it all the way down and plow through the chop.

[Skierx]

@ReallyGottaSki @DW side spray rail from comment above.

[Skierx]

 

[ReallyGottaSki]

@Skierx, thank you for that picture so promptly!

Its must have caused pause to apply adhesive to a sweet ride, but results are results!

oh, I see how width between wheelwells is a consideration and dictated the rail's location

 

@DW, yes indeed! the reduced poundage came from 33# from Iron to Aluminum intake, 2x20# from heads (trick flow 170s/58 cc chamber), Iron PCM pyramid manifolds to Commander SS for 2x27#, and lastly replaced Iron PCM front cover to Aluminum, 15# removed, requiring an Indmar-style Johnson crank drive pump instead of the sherwood, but, bonus was much more water flow.

so its much having like one less person in the boat, all the time

 

I gave it new bearings, seals, roller chain, scorpion rockers and appropriately sized pushrods, etc, and a 214/224 @.050 cam/lifters.

It scoots! and the main mission to lighten the powertrain was very effective

 

Since we're doing pictures...

 

[Dougp]

I had a 92 American (Skier) advance. It had a flat fixed trim tab in the middle at the transom. It flattened the wake significantly compared to the previous model

[skiinxs]

@ReallyGottaSki there was a plate on that vintage Ski Suprene that was used on the barefoot edition(this was the same hull). I had go6kd luck adding the plate for three event use. They did knock the rooster tail down and soften the wake a little. The plates were a simple flat aluminum plate approx. 10 " wide and 12" long. They were screwed to the bottom of the boat

overlapping the bottom around 4". Generally mounted flat, but you could induce a little down angle by shimming at the back edge of the transom. If you have a boat out of the G mold (G in the serial number) DO NOT set the boat up to run bow down. Those hulls need to be free enough to porpoise a little at wide open throttle. If set up to run bow down they had a tendency to chine lock / rudder stall.

[skiinxs]

@ReallyGottaSki I just saw your engine picture (nice!) and noticed your boom bracket. Chine lock when using a boom is very dangerous. There was a death caused from chine lock with someone on a boom with this vintage Ski Supreme. Make sure it will porpoise at wide open throttle.

[ReallyGottaSki]

@skiinxs Thank you!

 

I can report it does currently have just a little porpoise occurring as it is.when above 44 mph. and for now its just a new novelty to exceed 40 occasionally when conditions permit but not with passengers.

 

Yes, da boom! I'm not a frequent footer at all anymore, and would only foot 36-37 mph anyway. I can assure the boom is primarily for instructional skiing

However given your report, that coincides with others i've heard, if someone wanted to foot 40+ on my boat, i'll now more solidly refuse.

 

Now most curiously, this IS a G-boat, '82. It has not YET acted irregular in 25 years i've had it.

I grew up with a non-G '83, that would rudder stall if you sneezed too hard at 26 mph and had some wind chop.

I've been in a sn2001 when it swapped ends at 40+ and it was violent, so i certainly heed your warning!

Given it s a G boat, it may be best i call it a win and put away the turd polish.

If i build a plate over the winter, it will be set very neutral

 

I built the engine for very strong slalom rpms , and it delivers, and aware its the wrong hull for speed.

 

Sorry for the detour men!

[Jetsetr]

Request enlightenment: I know what “chine walk” is, what is “chine lock”?? Assuming (VERY dangerous) the chines lock the boat down and you’re unable to steer?

 

[ReallyGottaSki]

@Jetsetr Im sure there are interpretations but one scenario is the wetted surface lets go one one side of the boat, and the new wetted surface changes to 1/2 the hull bottom and one side of the boat. The waterline is now in at the gunwale its listing to. One can be going straight when this occurs, and all this while the rudder is ineffective, and throttling back is the only recourse, if you're still in the boat. After slowing the boat settles back in and acts like nothing happened afterward leaving you quite perplexed

 

Swapping ends is a different scenario, a low bow get pushed out of the thrust centerline first in a trough of a diagonal wave, and when spoons into next diagonal wave, the forces exceed the rudder's holding power and boat swaps ends in an instant.

[skiinxs]

@Jetsetr the steering starts to get vague, followed by a really hard left turn with the boat leaning really really hard to the right. Trying to counter steer to the right as it is happening makes it worse as then the rudder stalls. It will throw passengers out of the boat if they don't have a strong grip on something. The only recovery is hammering the throttle (if you have any left) to get the bow up, followed by gradually initiating a right turn as you gradually back off the throttle. In other words your intuitive reactions are all wrong. @ReallyGottaSki if it porpoises a little, someone probably already fixed it by taking some hook off the port side to free it up and bias it to the left side. You should make sure you never run the boat with it leaning to the right.

[RRGR]

Holy great stuff. I wasn’t expecting this much response, and great ideas. Makes me wonder how many boats out there would benefit from some tinkering.

 

I too am going through some weight reduction exercises, starting with the tower.

[Alberto Soares]

My experience with a 2011 Malibu LXI: wake was terrible from 15 to 28 off @34mph, I added about 40kg (88 lbs) in the bow, never use more than half of the gas tank, wake and tracking improved a bit. Bought today a pair of MINI TAB from HYDRO TAB, will try different configurations early next month and inform progress here.

[DW]

@Alberto Soares - You might also go after removing as much transom weight as possible, that will improve your slalom wake.

[ReallyGottaSki]

@skiinxs thank you for your valuable insight!

 

Ugh, It always listed starboard, even at rest still with noone aboard! This vintage is not cavity foam filled so its not wet and heavy, so its not water weight inbalance

 

Upon reinstalling engine, i nudged it over to port an 1/8" and it helped some but its not enough.

This winter i'll nudge it over another eighth if the log permits it, but will have to rebed the strut to go that far.

 

I recently put 25# under the passenger seat to assist (my gf is 105#) and its barely enough to keep it flat if she sits way over. I'm not all that heavy at 170

 

Our tinkering and hobbying is intriguing but must stay aware there are lives entrusted to us when out there.

So its great to have access to your history and knowledge with the type. much obliged

 

[ReallyGottaSki]

@Skierx ,

 

I read the smart rails install instructions, it directed to grind away the gel to the mat, if exceeding 30 knots.

 

heh, i take it you said damn the torpedoes, and both exceed 30 and didn't grind your gel?

[Skierx]

@ReallyGottaSki , you got that right. No grinding for me. Just made sure good clean surface. It's been 3 years no problems yet. I ski it 34 I have a friend that skis at 36. I've had the boat up as high as 43 and still no problems.

[Jody_Seal]

@ReallyGottaSki

How do you nudge the engine over and still make aligment??

Asking for a friend!

[ReallyGottaSki]

@Jody_Seal

 

[ReallyGottaSki]

Heh ,Im not telling you something you don't know already, alignment at the flange is easy. At the log, there is a little leeway where one places it

[BraceMaker]

Pft... Awesome

[BraceMaker]

Years ago my buddy had an old MC where someone redid the shaft log and stringers but it was way off. To get the engine in alignment and shaft in center on the log we removed all the screws on the strut dropped a few 1/4-20 screws to clamp the strut loosely, then aligned it,d grinder to relieve the fiberglass until the strut bolts could be reinstalled.

 

Wasn't ideal but way easier than cutting out the log. Gross strut movement less than a 1/16"

[RRGR]

@Alberto Soares were you able to test out some different configurations for the tabs? I am thinking about pulling the trigger here soon.