QL trim system

This is and has been a fun topic, a little controversy notwithstanding!

This time/ this year, its all in good natured fun, and good for our C-Brats Forum.

Usually by December, we've all got such cabin fever that something turns controversial, but in the past, political threads have caused some hard feelings.

This is good, clean fun!

Thanks, everybody!

Joe. :teeth :thup
 
Tom,

Just a minor thought, and guess what, not on trim tabs. The analysis of compressible fluids (gas) and non-compressible fluids (liquids) uses the same theory. Yes, one is a gas and another is a liquid, but when you make the corrections for the compression of gas (changes due to heat and pressure,) the equations are derived from the same source. Reynolds Number is as applicable to gas as to liquid as an example. Boat propellers and airplane propellers use the same theory. The Wright Brothers spent many an hour in the laboratory to make sure their airplanes flew, along the way figuring out their propeller was a moving airfoil. Bernoulli's law applies to both liquid and gas.

The point of this blog is to point out that things do not "just happen", but there is a reason for it. One can back into that reason, as the Wright Bros did, but there is logic in this world. Except with politicians, and I think there's logic there, they just don't admit the real thought.

So when there's a device that defies logic, one ought to be able to find the logic (think bumble bee) or admit that we're always learning. I hope I'm in the last category and I also hope that I'm willing to listen. For the bumble bee, here's an answer: Bumblebee. Scroll down to Myth which gives an explanation. And maybe that's how those trim tabs work.

Boris
 
I've read the story of the Wright brothers several times, and trying to work out the equations on propeller design confounded them for weeks. They thought they could find a body of propeller knowledge in the marine industry and found that propeller design there was a matter of trial and error. To some extent, I am not sure we have progressed much further since then given all the posts on props.
 
Greg thank you for this report.
http://maritimedynamics.com/interceptor.pdf

After reading it thru I learned a few things. 1) their test boat is the size of a cdory. 2) there was no difference in drag at all, NONE. 3) that the amount of lift was the same up to 55% of deployment of either system AND after that point the QL style tabs stopped producing additional lift while the lenco style tabs continued to produce additional lift up to 100% deployment. Now that is a big surprise to me. ( and is it lift or trim?)

Everyone go read that and then tell me what you think.
 
I didn't see any in fighting, just comments, maybe a little good natured chain pulling which is what makes this site so great. Most folks try and defend their purchases. I said what works for me. My wife walks around the boat and for me that doesn't require the use of my trim tabs. I thought I read something about a pressure wave created in front of the deployed GL gizmo causes the lift. I also thought someone mentioned that unlike trim tabs the QL are deployed in increments and you could not stop them anywhere as you can other devices such as permatrims and trim tabs. I'm sure Lenco and Bennett which will work on almost any kind of transom are not all that worried yet. Everything in print is not always true. I wonder what the long term service history on the QL System will turn out to be. Far be it from me to try and stop the experiment. Have at men! Enough from me. :lol:
D.D.
 
One observation on my CD25 is that at lower speeds, 12-20 mph, I generally use 60-80% of my Lenco tab bow down deflection. The boat is essentially stern heavy and drag not withstanding, gets best fuel economy with a lot of trim tab. Sometimes I wish they were bigger. I am not sure the Q/L system would generate enough stern lift across the operating range to make them a suitable replacement for tabs.
 
I guess your tab indicators work better than mine. I could never tell you a percentage of "tab down" with my Bennetts. The indicator has been replaced once already and is nearly as flaky as the first one. They operate fine but have never really indicated what they are doing. Took me some practice to get the feel of it but now I use them all the time for to correct for loading/movement of passengers.

Do you have a Permatrim or two on your boat? I use much less tab with our permatrims than I did before they were installed.
 
starcrafttom":akn322v9 said:
Greg thank you for this report.
http://maritimedynamics.com/interceptor.pdf

After reading it thru I learned a few things. 1) their test boat is the size of a cdory. 2) there was no difference in drag at all, NONE. 3) that the amount of lift was the same up to 55% of deployment of either system AND after that point the QL style tabs stopped producing additional lift while the lenco style tabs continued to produce additional lift up to 100% deployment. Now that is a big surprise to me. ( and is it lift or trim?)

Everyone go read that and then tell me what you think.
Click to expand...

Tom, Greg, and all-

This article is very interesting and revealing.

Actually, Tom, the boat used is " a 7-meter monohull model", not a full sized to scale boat, and one hopes the model performs as does the real boat, which is always something to keep in mind, or account for. Modeling is done a lot in aero and marine studies, and the tests and results have to consider any differences in scale and how i t would effect test results.

The measurements and performance results seem to indicate the following to me:

The interceptor type plate works OK at planing speeds up to that 55% deployment point, as mentioned.

This is because (theorizing now) the vertical plate acts as a flow "dam", creating stalled flow in front of it , and the water flow along the hull flows over this wedge shaped stalled flow, pushing upward on it and causing "lift", which is upward pressure (not to be confused with aerodynamic lift, as on a wing, but more "kite effect" like.)

I thought this might be true earlier, but nowhere was their any mention of this "how it might work" theory, and the 55% figure is an interesting determination.

While up to the 55% point the drag and lift effects are similar, past that point, the interceptor plate does not produce more gains, while incurring similar drag increases like the trim tabs, but without benefit. This, in itself, defines the limits of good performance with the interceptor plates.

The trim tabs have several advantages: 1) they work over a longer range of deployment without loosing their effectiveness ("up to 66% more lift at maximum deployment", 2) they also add increased planing area (similar to that added by a hydrofoil), resulting in A) increased control over pitching (longer hull effect) and B) quicker/earlier planning during acceleration. (The last two conclusions are not from the article, but generally accepted understanding.)

There are a lot of other practical/employment considerations discussed in the article, which is aimed at large boat/ferry/ and even jet boat considerations, most of which don't apply to our situation.

So it's up to you, individually, to choose, but I think mine would be for trim tabs, and hydraulic ones at that, considering the electric motor/salt water/seals/corrosion issues. I've got Bennetts on my 22 year old Sea Ray, and they still work well.

Joe. :teeth :thup
 
I have a Permatrim on my single Yamaha 150. It reduced the amount of trim tabs I use by about 15%, and also helps the boat track straighter at low speed. Together I can get the bow down as low as I need to go in chop. As speed goes up, I back off tabs and bring the motor up some to where at about 24-26 mph I have no tabs down and the motor more or less parallel to the bottom. At the top end, I can hit 32-33 mph with a light boat, but it is starting to get squirrelly and even with the Permatrim, the boat starts to porpoise. I have a little throttle left but can't use it due to the porpoising, but 30 is plenty fast enough. My most economical cruise in my current configuration is at 22-24 mph.
 
Joe, that's what I said. and I was very surprised at the results. This is the first good reason for me to change my mind about installing these tabs. It was the proof I was looking for. That said I may still get the QL tabs. The amount of lift at 55% deployment may very well be more then enough for my boat and use and I would never need the extra lift of the other tabs. I do know that I never use the last 20% of tab deployment on my 22. Its not needed to get the bow down and in fact if I fully deploy my 22's tabs it cause's bow steer. So now I have to decide if its enough.

My need is mainly trim from side to side. I can control my bow angle with the motor trim just fine at any speed. My time to plane is great and my top speed is 40 mph which I like to have but rarely use. its the side to side that I have to correct and to tell the truth I really just need one as I always tilt to the port. but they sell them in sets so that's what I will get.
 
I agree and could easily live with the 55%. With dual permatrims out back, I can get some serous bow steerage with my current tabs deployed much less than 100%. A can actually do it with the Permatrims alone as well. I am like Tom and mainly need it for side to side and a little bow tuning sometimes. The QL design would have the added benefit of saving me a set of Zincs multiple times per year and also shave a foot of length off my bottom service every three months becuase the current tabs collect the most growth.

Less weight
Better control panel
Likely better following seas handling
Possibly better backing handling
cleaner stern for fishing (if I ever get around to it)
less marine growth issues
simpler maintenance and reduced complexity of system

Some negatives exist no matter what you do and the reduced overall trimming potential could be addressed by increasing the width or number of interceptors if space is available.

I think that comparison document was comparing two types of the same width so the overall trimming potential could be increased with wider/more interceptors. Depends on the boat and use of course.

Anyone know off-hand how wide the trim tabs are on the standard 25?
 
Tom-

Sounds like we've come to some agreement! :hug :rose :hug2

As you know, the engineer & science types are never satisfied until they think they've got it all figured out, quantified, and designed and engineered with a 400% safety margin, and , finally, all the $$$ accounted for an in the bank! (overstated only slightly) :wink

Besides the gas weight issue, you probably have some torque tilt from the engine/prop twist.

If you really only need the extra lift on one side, why not put both tabs one the same side? :lol:

Or just forget the trim tabs/adjusters and get a second, additional wife (a really big one!):
She should also be good a baiting hooks, netting fish, and raising crab pots and anchors, too!
What's not to like? :smilep

Joe. :teeth :thup
 
additional wife (a really big one!):
She should also be good a baiting hooks, netting fish, and raising crab pots and anchors, too!
What's not to like?
Click to expand...

the really big part :shock:

in the words of my lovely wife. " I dont care what you look at but anything of yours that touchs is subject to removel... :shock:" besides she can fish bait clean drive and trailer the boat.
 
Well, with the boat needing a haulout soon for some motor work, the opportunity is presenting itself to switch tabs but I am not going to do it.

Why?

I still think they are likely a great product and would do the job for our boats but after much thought and more importantly some reflection on our local boating conditions, I am sticking with traditional tabs.

The reason is debris in the water. We drive through small debris all the time in the puget sound and no matter how hard I keep watch, there seems to be an occaisional larger bit that contacts the boat as well. We have coasted over a 30ftX 6inch piece of wood and very recently got a boomerang shaped piece about 5 feet long and 4 inches in diameter hooked on the transoms at speed. I can tell you that was a strange feeling and it makes me fear for the health of a pair of interceptor trim devices on my boat at least the way we are using it thus far.

I think a good chunk of wood could easily torque one of those tabs and knock off the alignment enough to cause binding issues and I am not pulling it out of the water just to fuss with that. I have this fear because I have read reports of their sensitivity to mis-alignment.

Smooth stainless it is for now simply for durability sake. Good discussion and thanks for your willingness to fight my persuasions.

Greg
 
Gregg,

I think you are onto something there. The T-tabs are sure less likely to get ripped off by some piece of flotsam. This thread has gotten me to thinking I might need to look into the Permatrims though.

Thanks,

Harvey
SleepyC :moon
 
hardee":9s95h6du said:
Gregg,

I think you are onto something there. The T-tabs are sure less likely to get ripped off by some piece of flotsam. This thread has gotten me to thinking I might need to look into the Permatrims though.

Thanks,

Harvey
SleepyC :moon
Click to expand...
Harvey, I went for years without the permatrims on my 22 and only added them when Les suggested them as a solution to fixing a missing piece of my starboard engine's cavitation plate (it got knocked off a few summers ago when a down rigger ball launched off the back in big seas).
After i had them installed, I wished I had done it much sooner. The two things you'll immediately notice are:
1) an ability to push the nose down some when going into modest chop - this smooths out the ride considerably. Is it great like a deep V? No, but it's much better than before especially at those "awkward speeds" between 10 and 16kts where the boat transitions to planing.
2) A MUCH faster transition to being on plane. W/o the permatrims, there's considerable bow rise prior to it rolling back down as you get on plane. With the permatrims, the bow rise is minimal.

The cost wasn't too much if I recall - around $200/ea and a fairly minimal install fee. Give EQ Marine a call and ask for a quote. You'll be happy with this mod.
 
Funnythat no one mentioned the need for trimming the boat when dealing with side forces of wind. Many of the worse trim conditions I've encountered was when I was tacking against a port or starboard wind. That would cause my boat to have many trim difficulties that I'd address with tabs...however, as I tab to flatten the boat it had the effect to exacerbate the steering requirement (sort of like dragging one foot on a sled or ski to steer in that direction). Gusts were the worse. Anyway, since this subject seemed to be coming to closure, it only seemed fair to throw another log on the fire. Ron :smile
 
it looks I too will go with the standard tabs. after a lot of looking and figureing and tape measure work I dont think the QL's will fit the boat. I would have to alter the the plug on the tabs or alter the boat. I feel fine doing both but it makes susan queasy when I stand to close to the boat with the welder or the grinder.
 
Joe mentioned lengthing the hull in effect with standard tabs, and I believe that is a valid point. My sense is that tabs take up some of the shock when going into chop, not just the bow. Another feature that tabs have when fully extended at slow speeds is to reduce hull speed ever so slightly when docking which almost always is helpful.

John
 
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