QL trim system

[Aurelia]

Anyone have experience with these? Seems like a simple system that would be effective on a dory. I want to check the mounting of my tabs when we next pull it out of the water and could end up replacing my bennetts.

http://www.great-water.com/pages/QL/QL_Trim_Sys.htm

I have the DIY boat article on them as well if anyone wants it.

Greg

[starcrafttom]

Greg, did you get these for your boat? Im thinking of trying them. Anyone have a opinion on these.

[Sea Wolf]

Without doing any research on existing evaluations, I'd think their operation can be summed up in one word: d-r-a-g, which is synonymous with inefficiency, which leads to low MPG, which is to be avoided as a waste of $$$.

Just my SWAG !

On Edit: Here's an article on the installation of these trim tabs from DiY Boat Owner Magazine, 2005-4:

http://www.tcsmarine.com/images/prodDownloads/DIYMagazine%20article.pdf

Joe.

[tpbrady]

Joe,

I think this is best explained as the difference between a flap and a spoiler or dive brake. A flap is meant to produce lift at low speeds and a spoiler is meant to slow things down. A flap has smooth air flowing over it and a spoiler has turbulent air and consequently more drap. This trim tab looks more like a spoiler.

[Sea Wolf]

Tom-

Thanks for the clarification! I agree with you, this is a spoiler, not a flap,

I do realize that the downward foil will produce greater pressure on the hull in front of it, and result in upward lift. The question would seem to be whether one could get that lift with less drag from a traditional angled down trim tab which is more of a flap.

I'm guessing that this downward protrusion produces the upward lift with a much greater penalty of drag than a traditional tab.

And at low speeds, below planning speeds, this would be even more wasteful, comparatively.

It might seem to work well on large, powerful boats, or on some hulls with special needs of extra lift, but the majority of boats would do better with traditional tabs.

But so far, this is all (on my part at least), speculation, and would have to be demonstrated in practice.

Thanks!

Joe.

[Aurelia]

Tom,

I did not order a set of these yet, but I do intend to when we next haul out for some bottom work. Based on my diver's estimation, it could still be another year or more.

The properties of water are very different from air. Compression would be one example. Air=easy Water=quite difficult

The system is actually supposed to produce less drag than convention tabs. Picture the downward angle at which a conventional tab must be projected for the desired effect. Now think of the cross section or how far the rear edge of that tab is below the rear edge of the hull. That measure is very likely greater than the downward extension needed on the QL tabs for the desired effect. Most users note that they use the QL tabs only partially extended (40%) for the needed effect. An added benefit would be the lack of surface drag added by water flowing over the length of the traditional tab as well.

Tom, you are welcome to go first as I would love to know how well it works. Maybe I could even contribute some experimental time helping with the install. I would aim for a set of 450mm units although for trimming with my twins, I think a pair of 300mm units could work. The install looks a bit challenging so I would likely seek some assistance with that primary hole myself. How easy is the inside access of your trailing edge on your 27?

I would still love to see a comparison test on two identical boats with both systems.

Here is some light reading:

http://www.tcsmarine.com/images/prodDownloads/DIYMagazine%20article.pdf

http://www.offshoreonly.com/forums/general-q/97624-volvo-penta-ql-boat-trim-system.html

http://www.boatingabc.com/forums/ubbthreads.php/topics/270570/1/Photos_new_Volvo_QL_trim_syste.html

http://www.ybw.com/forums/showthread.php?t=108057

http://www.ausfish.com.au/vforum/showthread.php?t=130035

http://www.thehulltruth.com/archive/t-258014.html

http://continuouswave.com/ubb/Forum1/HTML/015758.html

[journey on]

Well, its hard to discuss vectors with words, but here goes.

We agree that (according to Newton) a force is produced by changing the velocity of a mass? F=m*a? And changing direction includes both the amount as well aas the direction? Then the force has both direction and amount, which is a vector.

So lets look at the two tabs. The first are the ones which Journey On has: those which stick a sheet angled down from the end of the hull. these deflect the water down, changing its direction down, with a resultant upward force, AS WELL AS some force aft due to drag on the plate thru the water.

Next the thingambob which sticks a plate straight down. The water is just slowed down as the plate is dragged (drug?) thru the water. Thus the major force is aft, producing only drag. There would be only incidental force lifting the stern, from turbulent water.

The QL device seems to be a salesman dream, sold with a disregard for physics. Sorry.

Boris

[Tug]

They kind of remind me of some old trim tabs i used to see around many years ago. They were like Bennett trim tabs but the ( tab) plate portion was always fully extended into the water.Instead of the hydraulic cylinder there was a large, heavy duty coil spring which i presume compressed the faster the boat would go.I am not sure if they was effective in getting the boat on plane quickly but i always liked them just for the fact that it was a simple design,low maintainance and looked like they would last forever. They may of been custom made by a small company because i have never seem them advertised. Tug

[Will-C]

I'm not seeing enough of a reason to do these in place of Permtrims. I have trim tabs (came std. with the boat) and never use them as we can shift weight form side to side to level the boat out. I guess having something,new different is a biggie for some. Drilling less holes in the boat and having some additional low speed steering and the fact that they work as experenced by many is enough for me to stay with the Permatrim(s) on this one.
D.D.

[Aurelia]

A salesmans dream that won a NMMA innovation award and MAATS award and is strong enough to lift the tail ends of 30,000 lb+ fishing boats quicker than conventional tabs. Also convincing enough to be installed at factories including one making a few models under the obscure name of Boston Whaler.

I am not sure Volvo-Penta is a small enough company to make such a mistake if the first place, much less still be selling and installing it 6 years afterward.

I agree its hard to wrap your mind around, remember, we are not plowing a field here, its water we are talking about and they can only descend 1.37 inches downward. How far do you think your tabs descend below your hull?....drink the coolaid.

My permatrims are the best thing we ever added to the boat. I'll bet there were a few skeptics concerning those as well.

http://www.volvopenta.com/sitecollectiondocuments/penta/parts%20brochures/ql%20-%20boat%20trim%20system%20(eng).pdf

[Will-C]

I hope you enjoy the cool aid, I'm not drinking it. "We are not plowing a field here" whats that mean? Farmers are stupid? Volvo Penta if I'm not mistaken mostly is famous for outdrives (inboard outboards) none of which I would never own either. Boston Whaler great boats if money is no object, but I'm not sure I would copy everything they do. I'm not a proponent of trim tabs, like I said I never use mine. Your obviously right about these things being the greatest thing. I just said why I liked Permatrims. If I were to buy new or used boat I'm pretty sure I would try to avoid drilling any new holes below the waterline. But that's me. Enjoy the new gizmos.
D.D.

[Aurelia]

I was primarily responding to Boris. And I was so slow in finishing my message that you and Tug snuck in before my post. No knocking farmers, just commenting on drag concerns. A design that causes drag in the soil may not cause the same type of drag in a fluid like water. I don't have these QL tabs but I am trying to keep an open mind.

I have Bennetts on the boat which also create lots of holes that were likely not sealed well from the factory based on feedback from other owners. When our boat next comes out of the water for engine/bottom work, I plan to pull the Bennetts just to check on that situation at a minimum. While I have them off, I may as well consider my options, one of which would be the QL tabs.

It's fun to gather new information and try to verify/justify/demistify/or smash my attempts at progress. I tease about drinking the coolaid because I enjoy trying to run with an idea. Whether in ends in failure or success is normally only a small, nearly meaningless portion of the overall exercise to me.

[journey on]

OK, if you're convinced that a plate at right angles to the fluid flow develops lift, I'm all for you. I'd be interested in your explanation of the forces involved. Your references said it was great, but didn't present why or tell how it worked.

But that's not what I learned in fluid flow 101. As Sea Wolf discussed above, the difference between dive brakes and flaps, for a simpler analogy. I thought that dive brakes shouldn't cause lift, because that would disturb the planes trajectory. Flaps, on the other hand are there only for lift, and some drag is accepted. I want trim tabs that give the maximum lift for the least drag. I don't believe those QL tabs do so.

And in plowing a field, you shear the soil which requires a force. Through the water, yes you shear some water, but that's viscosity, a much smaller value. Lift comes from newtons second law, F = m*a.

If you want to use them feel free. I'm happy with the Bennett's and use them often.

Boris

[Sea Wolf]

Aurelia-

I read ALL of the posts on the links you mentioned above!

Thanks for the migraine!

I think it would be fun to list all of the possible pros and cons, and legitimate and uncalled for comments regarding their lineage, operation, and suspected falsified claims, but I'm too old to write another thesis right now.

What's surprising to me is that Volvo-Penta has not taken the initiative in offering either a logical, theoretical, or empirical explanation of their functioning, which seems to be the stumbling block for most of their critics. Any system will have its practical limitations and drawbacks, and those are pointed out in the readings, but nowhere is their an offering of how not only do these work, but how, and especially, in the process, the drag factor is less. (Those of us who consider ourselves science and engineering types, at least, won't rest without the logical process in hand, or head, really!)

Another surprising development, or, really, a lack thereof, is the absence of a counter-argument from the Bennett, Lenco, and/or other manufacturers. But I guess it's hard to argue with something that isn't there.......

Joe.

[hardee]

"It's fun to gather new information and try to verify/justify/demistify/or smash my attempts at progress. I tease about drinking the coolaid because I enjoy trying to run with an idea. Whether in ends in failure or success is normally only a small, nearly meaningless portion of the overall exercise to me."

Sounds like a good project for "MythBusters". I have Lenco tabs, use them occasionally, and like the results. I have yet to add Permatrims to my twin 40's. maybe sometime, but they haven't gotten high enough up the priority list yet.

I'm not the scientist or engineer you guys are, but for me, the logic doesn't work. Looks like more drag. Yes, my tabs may extend lower than the 1.??" that the QL's do, but it it not at the 90 angle of the QL's, hence, less drag, as the water continues to move on by, (though it does have to change direction, providing the stern lift), it does not have to stop, or change direction in a 90 angle. Also, less torque on the attachment screws with the tabs, (I think, maybe, IMHO). BTW Gregg, if you and a hundred others try them and it does work, I'll be considering it then, but I'm not one to be first in line, especially at crossing an intersection on the first flash of the green light.

Harvey
SleepyC