Trim Tab angle on Heat
 

Has anybody experimented with the trim tab placement and angle on a Heat?

When I was racing jet-ski's we discovered that mounting the tabs parralell to the water as opposed to mounting them parallel to the hull was faster on the ski's. That when the tabs are mounted parrallel to the hull, and are trimmed down below the hull line, they act as brakes because they are not only pushing down, but out, at the same time instead of just adjusting the attitude of the boat.

I mounted the tabs in a horizontal position on my 22ft Eliminator, and they reduced chine walk above 80 mph. The boat did a best of 91.2 before I sold it to get my Nordic. When the tabs are mounted in this way, the outside end of the tab is the first to touch the water, and as such is not creating as much hydrodynamic drag.

When I asked the head rigger at Nordic about trim tab angle, his response was that he had always mounted them parrallel to the hull, with the exception of their racing ski boats. I asked him why this was, and he said he didn't know.

I would love some input and discussion.

Here is the example of my mounting the tabs on my Eliminator.

Chris

Chris,
Do a search on trim tabs. You will find plenty of coversation and information.
I switched mine over from the factory Bennetts to Eddies. Mine are mounted out at the chines parallel to the hull. They work great.
You'll see the install on the search threads.
Regards,
Steve

Steve,
Your install looks awsome!. I can see why you used the single ram Eddies. Cutting the edge of the mounting plate off at an angle so you could get the tab out as far as possible is a stroke of genius. I also found out by trial and error on my jetski, that mounting them up aprox a half inch so as to form another step made the ski faster. Sharpening the line where the transom meets the hull so the water doesn't follow the transom up was also worth about .5 mph.

Having said that.... have you tried them mounted in a horizontal manner so that you know for sure that the way you did it is the fastest possible? Or do you know someone who has tried it this way?

I did notice that the really fast Howard Bullet that broke 130mph had the tabs mounted at hull angle.
I also noted that "The worlds fastest V-bottom boat" (The Fountain) has the tabs mounted horizontal (or flat).

I am in no way attempting to be cheeky. I am just looking for information, and test results. I ,by nature, analize just about everything.


I sure do appreciate all your help and information,

Chris

Note: the jetski I built was a Pro-1200 class boat, and took 7th in the world in 2004. (I was not riding it, but it would go 82mph on 1200 cc's in race trim. It wasn't proped for top speed)

Hi Chris,
The reason I recommended you look at the threads is that there are varying opinions on this subject, and I think most of them have validity. No doubt the farther you move tabs away from water's surface (horizontal or high parallel), the less drag they create. At the same time, they also transmit less water energy to the hull, providing less stability, because they have less surface area touching it.
Mine seem to be working well. They retract above parallel to the hull and only contact spray off the hull bottom at speed. However when I deploy them in rough water, they still work well, and mounted out at the corners, they have more leverage to correct chine walking and lateral imbalances.
I have walked around the pits at various offshore races, and looked at the boats. I would say 90% of them have the tabs mounted in the traditional, parallel to hull, manner. The really fast new race Fountains are horizontal, however a friend's here (42' 900SCMerc's/#6, Randy Davis' former Catalina Ski Race boat, 110+) are parallel.
I guess each application is specific. I don't know anyone running the tabs horizontal on a Nordic. Why don't you give it a try and see how it works? Just move them out as far as possible to the chines, whatever you do. The factory likes to mount them in a little too close to the drive on Heats (JMHO), probably due to the tight transom (exhaust, steering, ladder,etc) and swim platform. They do mount them out and parallel on the Flames.
That sounds like a badass jet ski you had.
Regards,
Steve

Hmmmm.... This sounds like my Flame Tab Mount thread.
I too would like to experiment it this area. The thing with Nordic is just like Chris mentioned; the answer you'll always get is "we've always done them that way"
In my "past" experiences with Nordic and tech stuff is that they really don't have any idea. Maybe the new staff will be better but they don't have the hands on time to know any better with stuff like this.
That being said, when speaking in depth with Dana, DesertRage (Jon) was told by the owner there that horizontal is the best for chine walk and speed. The end result of the conversation was to split the deadrise angle for the best overall result. Those tabs are now going on a Rage and I'm sure this will be revisited once again. Stay tuned :)
So it seems to me that horizontal would be the optimum for chine walk but how does that effect the overall intent of the tab?
Seems odd but the Flame must have tabs for all around use. I never needed tab at all on the Heat at speeds up to 100mph; Rock solid! The Rage doesn't really appear to need them either but then I've never been over 80 in a Rage (yet :evilb:)
Where that was going is I still need the full functionality of the tabs on the Flame and not just to reduce chine walk, so I'm toying with the idea of splitting the deadrise angle while my motors are out.

Dave

Some added thought. If the tabs are mounted horizontal they will lose a lot of effectiveness when deployed for planing, slow running or balancing the boat at slower speeds. At high speeds I've never run the tabs down at all. I've been mid 90's in a 28 and near 100 in a 25. The 25 was pretty squirrely above 90. Lowering the tabs enough to settle it down scrubbed a lot of speed. In that situation they may have worked much better mounted parallel. My 35 doesn't go fast enough to worry about it.lol.

This thread already has a lot of good information in it. Offshore Only is an awesome Knowledge Base! :grinser010:

When I spoke with DMP (Bob), he suggested that if the perspective boat had good manners at speed and doesn’t need help planning the horizontal mount would be the fastest. I think Chris is right on when talking about the hydrodynamic drag a parallel to the hull tab can create. The function of the tabs in my application was to create a new flat running surface. With the chines out of the water at speed and no pad my V hull had nothing to keep it from walking.

After scouring the forums for tab info I settled on ½ the dead rise (11 degrees). I used an inclinometer to position them and had very good results with them in this orientation. The tabs didn’t lose any effectiveness, at slow speeds it felt like I could roll the boat over with one tab. The HP1000’s were on the large side for a Mirage 232, but I wouldn’t change anything if I was to do it again. Once at speed I would drop them just enough to stabilize the boat in slightly rough water. If they slowed me down I wouldn’t be able to tell since I would be forced to back out of the throttle with out them.

I also feel the furthest away from the drive (increase in leverage) and still be at water level would be best. If the tabs are above the running water level they would be at more of an angle when deployed to contact the water.

When my Eliminator is at speed (above 82), it would start to chine walk slightly. The boat was sitting on the very end of a small pad. I have a video of the boat going 90, and you can see that it is sitting on the back of the pad, and the very outside tips of the tabs, thus creating a tricycle effect. I would lower them just enough to stop the chine walk, and then continue to throttle up.

Chris

My thoughts exactly!

Hey Chris,

Did you end up mounting tabs on the new Heat? I have a set of HP1000's heading for the Rage this weekend. I am considering around 1/2 dead rise (9 deg). My inclinometer reads 19 at the transom.

Jon

I will be mounting my tabs (also Dana 1000's), horizontally, and over the inner strakes. I have video of my boat going 90+ mph from the rear of the boat, and you can see the boat start to chine walk when the boat is lifted above the inner strakes, on the pad. keeping the boat trimmed so that the inner strakes are still wet, nets me about 88-89 mph. Trimming up beyond this point, gains me an additional 4-5 mph.

Chris

I can see why your tabs would work in a horizontal position on the Eliminator hull. Big pad, flat hull angle,more lift. probably the most efficient way for that application. On a deeper v hull, it may not be.

Some info I have gathered in my quest for an answer:

The following is from Tegque on tech, Power boat mag.

I have a 1999 21' Baja Hammer. It is equipped with a 7.4-liter MerCruiser engine, and has a top speed in the 65 to 70 mph range. It is great for the lake we live on, but occasionally my son and I take it to a much larger lake for a poker run.
While the top speed is OK to run with most of the boats, the handling gets a little out of shape especially when one of the much larger boats goes past and we cross its wake. My question is would trim tabs help or do I just buy a bigger boat?
Alan Gonzalez
San Antonio, Texas
Answer: Adding trim tabs would help to settle the boat down in the cross wakes. Using them will result in a reduction of your top speed, though. When they are up, the boat will be the same as it is now. They can be lowered just enough to improve control without scrubbing off too much speed. I would install them toward the keel, a little in from the traditional mounting location out by the chine. This will allow them to still be effective when the boat is riding high up on the keel and the chines are pretty much out of the water. I also would consider mounting the tabs horizontally as opposed to parallel to the bottom surface. This will allow the outside tips to touch water before the whole plane does. Sometimes, when the planes are mounted parallel to the bottom, the angle of the plate accentuates the chine-walking motion as the boat launches off each plane alternately.

In the process of mounting my tabs:

Chris

Lookin good Chris. Careful of my drive while you're back there. :)

You going to have that all wrapped up for the weekend? Supposed to get some good weather in Seattle finally.

-Ned

Ned,

The goal is to be on the water on Sunday.

I will give you a call this weekend.

Chris

sounds good. i'm planning on sunday too.

TTT
az350 here you go
Steve

Be cautious mounting your tabs and following the guidance of this thread. I believe Chris has remounted them since these pictures due to some undesirable characteristics. Chris knows his boat very well. It might be worth searching on his most recent posts.

Just an FYI...

I am pulling up some old posts for az350 on tabs for his information (and his request) if you guys are wondering what this is about.
Best Regards,
Steve

After doing a significant amount of testing..(mounting the tabs in four different locations)...and actually taking video of the rear of the boat with a go-pro camera mounted at the rear of the boat and watching the water coming off the hull while under way...I ended up mounting the tabs parralel to the bottom of the hull...as far out as possible...about 1.25 inches up from the bottom of the hull.

Chris

Hi, I'm kind of new to OSO and have a 2000 heat I bought last may. I love my nordic and that's all I ever hear from other nordic owners. Mine is pretty much stock 502 mpi/bravo1 except EMI thunder exhaust came with it.
I recently came across some 280 k-planes for a good deal and pulled the trigger. Kind of funny these trim tab threads found their way to the top at such a convenient time.
Chris, do you have pictures of where you ended up mounting the tabs? Besides the exhaust, is there any difference between your boat's hull and mine? Will the 280s be good on my heat? I mostly need them for pulling kids around on tubes without falling off plane, when the channel gets really rough at powell and I seem to have a porpoising issue when trimming the drive up. I don't have to trim it very much before it starts porpoising. Tabs will help with that, right?
I've read a whole bunch of threads on OSO, specifically this nordic forum and have learned a lot. To be honest I don't know much about "go fast boats" but I'm learning and would like to be able to upgrade and do my own work on my boat.
Thanks
Eric

The only difference between his hull and your hull is Chris' is an all composite hull, yours (and mine) still utilize wood in the construction. Other than that they are the same shape. Chris I am sure will pop in with more information for you.

I will take some pictures of the rear of my boat this next week and post them for you...I ended up using the Dana 900 tabs...as the 1000 would have a signifcant amount of spray hit them even when fully retracted.

Chris

Would you care to elaborate?

I hope this helps,
Chris

That is how mine are mounted from Nordic. Dana HP900

Hey Guys..... It's been a while...I'm ordering some tabs for my '06 28 this week.So, the HP900's are the ones to have? Chris, I can get pretty close to that spot by the pic, but do you have any specific measurements? THANKS!!

Also, Mike at Nordic Said they put Eddie Marine tabs on now. Are they the same as the Dana's? What about indicators? I really would like a little round Electric Gauge instead on a huge cable indicator?

Derek

I ended up mounting the tabs parralel to the bottom of the hull...as far out as possible...about 1.25 inches up from the bottom of the hull.

Chris

I Ordered Red HP 900's Last week from mike.... I'll post pics on the install.....

Derek

I will be adding some to my heat pretty quick as well. Take some pics and document, please. Thanks.

Hi. I am ordering Eddie marines this week. how long are the Dana 900. Eddie marine are 18" and 24"
Thx. john

I have 18" single ram Eddies on my Heat. They work great.
Steve

hi where did you mount the gauges. do you have a picture? i am having a problem finding a spot. thx john

Since my boat came with an XR drive it had a single slot mechanical indicator on the dash.
The original Bennett tabs did have electric indicators, but I didn't like the way they were mounted in the top of the dash "tray".
I added a 3 horizontal slot mechanical indicator for my tabs and drive. It has worked well since then.
I also like the vertical mechanical indicators that come up through the dash.
I'll see of I can pull up an old thread with that information.
Steve

Thanks Steve.