Go Back  Offshoreonly.com > Owners Forum > Nordic
Trim Tab angle on Heat >

Trim Tab angle on Heat

Notices

Trim Tab angle on Heat

Old 08-12-2008, 09:52 PM
  #1  
Chris
Gold Member
Thread Starter
 
CB-BLR's Avatar
 
Join Date: Sep 2005
Location: Snohomish, WA
Posts: 1,426
Likes: 0
Received 1 Like on 1 Post
Default 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
Attached Thumbnails Trim Tab angle on Heat-elimxx-017.jpg  

Last edited by CB-BLR; 08-12-2008 at 10:12 PM.
CB-BLR is offline  
Old 08-12-2008, 11:19 PM
  #2  
Registered
 
Steve Zuckerman's Avatar
 
Join Date: Nov 2002
Location: Nashvegas, TN
Posts: 2,621
Likes: 0
Received 1 Like on 1 Post
Default

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 Zuckerman is offline  
Old 08-13-2008, 01:26 AM
  #3  
Chris
Gold Member
Thread Starter
 
CB-BLR's Avatar
 
Join Date: Sep 2005
Location: Snohomish, WA
Posts: 1,426
Likes: 0
Received 1 Like on 1 Post
Default

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)

Last edited by CB-BLR; 08-13-2008 at 01:36 AM.
CB-BLR is offline  
Old 08-13-2008, 09:03 AM
  #4  
Registered
 
Steve Zuckerman's Avatar
 
Join Date: Nov 2002
Location: Nashvegas, TN
Posts: 2,621
Likes: 0
Received 1 Like on 1 Post
Default

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

Last edited by Steve Zuckerman; 08-13-2008 at 01:24 PM.
Steve Zuckerman is offline  
Old 08-14-2008, 08:15 AM
  #5  
Registered
iTrader: (4)
 
Nordicflame's Avatar
 
Join Date: Mar 2002
Location: Layton, Utah
Posts: 1,546
Received 4 Likes on 4 Posts
Default

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 )
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
Nordicflame is offline  
Old 08-14-2008, 05:42 PM
  #6  
Registered
 
Join Date: Oct 2000
Location: Spicewood, Texas USA
Posts: 1,382
Likes: 0
Received 3 Likes on 2 Posts
Default

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.
bobl is offline  
Old 08-15-2008, 12:21 PM
  #7  
Gold Member
Gold Member
iTrader: (2)
 
DesertRage's Avatar
 
Join Date: Feb 2007
Location: SL,UT
Posts: 374
Likes: 0
Received 0 Likes on 0 Posts
Default

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

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.
DesertRage is offline  
Old 08-15-2008, 09:16 PM
  #8  
Chris
Gold Member
Thread Starter
 
CB-BLR's Avatar
 
Join Date: Sep 2005
Location: Snohomish, WA
Posts: 1,426
Likes: 0
Received 1 Like on 1 Post
Default

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
CB-BLR is offline  
Old 08-16-2008, 09:38 AM
  #9  
Registered
iTrader: (4)
 
Nordicflame's Avatar
 
Join Date: Mar 2002
Location: Layton, Utah
Posts: 1,546
Received 4 Likes on 4 Posts
Default

Originally Posted by CB-BLR
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!
Nordicflame is offline  
Old 04-07-2009, 01:23 PM
  #10  
Gold Member
Gold Member
iTrader: (2)
 
DesertRage's Avatar
 
Join Date: Feb 2007
Location: SL,UT
Posts: 374
Likes: 0
Received 0 Likes on 0 Posts
Default

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

Last edited by DesertRage; 04-08-2009 at 07:46 AM.
DesertRage is offline  

Quick Reply: Trim Tab angle on Heat


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.