New Trim Tab Type, Possibly Volvo-Penta QL System

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Author Topic:   New Trim Tab Type, Possibly Volvo-Penta QL System

whaler3 posted 02-29-2008 10:17 PM ET (US)
Saw a new type trim tab the other day which I would describe as a piece of metal that comes straight down from the transom. It will retract or lower to put the bow angle down. It seems to me that it would be very bad for gas mileage as to the amount of drag. At the price of gas today I don't think I would want them on my boat!
jimh posted 02-29-2008 11:58 PM ET (US)
Perhaps you are talking about the Volvo QL Trim Tab system. It was introduced in 2005. It won an award for its innovative technique. Boston Whaler appears to be using the Volvo QL Trim Tab on their new 230 DAUNTLESS. I would take that as an endorsement.

http://www.volvopentastore.com/ QLTrim_tabs_Complete_Systems_and_Spare_Parts/dm/cart_id. 089567208--category_id.344738--search_type.category--session_id. 551718392--store_id.366--view_id.344738
If you have some evidence or strong test results which show that the Volvo QL Trim Tab is not a good product or that it is inefficient and causes more drag than conventional trim tab systems, I encourage you to present your findings here and show us your test results.
According to Volvo Penta, one of the advantages and benefits of their QL Trim Tab system is "less drag." This claim by Volvo Penta is in direct conflict with what I infer to be your claim that they have more drag than conventional trim tabs.
cooper1958nc posted 03-01-2008 09:33 AM ET (US)
I cannot tell from the advertisement how these things are supposed to work.
Usually big manfacturers' claims are not wholly fictitious, but neither do manufacturers have the ability to alter physical laws.
Conventional trim tabs act like alierons on an airplane wing, though they act together. They increase lift, but because they are just flat plates, their lift coefficient is low and their drag coefficient is high. Ease of installation and maintenance make them more feasible than a submerged wing (hydrofoil) with much better coefficients. Even though their drag is high, they can decrease overall drag by improving trim especially during planing transition. Sometimes improving trim is worth the drag as well.
Does anyone know the theory behind these trim tabs?
jimh posted 03-01-2008 10:17 AM ET (US)
A seller of the Volvo-Penta QL Trim Tab system has a web page which shows the installation of these devices on several boats. There are many positive comments from the owners of the boats regarding the effectiveness of the Volvo-Penta QL Trim Tab, as might be expected in a promotional announcement. See
http://www.great-water.com/pages/product_pages/QL_Trim_Sys.htm
One notable feature is the lack of much projection aft from the transom, which eliminates interference with boarding ladders mounted on the transom. This may be one of the most appealing features of the Volvo-Penta QL Trim Tab system.
There is also a publication available which shows the installation details. It appears that there are some electrical circuits which are conducted via a plug-in connector arrangement which have to pass through the transom of the boat at a point which could often be below the waterline. Such an installation technique may limit the applicability of this product on many classic Boston Whaler boats because of the Unibond hull construction technique. Generally there is not good access to the inboard face of the transom below the waterline on a Boston Whaler boat. See
http://www.great-water.com/pdf/QL_Manuals/Trim_Sys_%20install.pdf
for details.
Tom W Clark posted 03-01-2008 11:19 AM ET (US)
That's an interesting design and one I had never heard of before. The Volvo QL Trim Tab system works by creating a small dam, if you will, below the hull at the transom. This slows or stops the flow of water to create what is effectively a "hook" in the bottom of the hull, a fluid hook so to speak, or at least that is how I am reading the illustration.
It does seem non-intuitive to think this could create less drag than a convention trim tab system, but I have to conclude that it could not have been brought to market if it did not at the very least, equal the performance of conventional trim tabs.
cooper1958nc wrote:
"Conventional trim tabs act like ailerons on an airplane wing, though they act together."
No, that's not right. Trim tabs *may* be used together, but their greatest benefit is in being used independently to correct a list while underway. Furthermore, when trim tab are used together, they both travel in the same direction while ailerons always work in sync but always in opposite directions.
Ailerons also travel both up and down whereas trim tabs travel only down. The more accurate comparison in aviation for trim tabs are flaps on the wing of an airplane. Flaps travel down only and change the angle of attack of the wing to alter the lift generated by it but also add drag.
Tom W Clark posted 03-01-2008 11:44 AM ET (US)
There are a couple problem for owners of Classic Whalers considering retrofitting the Volvo QL Trim Tab system. The wire from the Interceptor unit itself passes through the transom near the bottom of the hull, whereas on hydraulically operate trim tabs or electric Lencos, the hydraulic line or electrical cable passes through the transom at the top of the actuator/ram.
On a Whaler hull there will be a lot of foam to drill through and drill through at an angle to have the electrical wire exit above the inner liner of a Whaler hull. The instruction for the Volvo QL Trim Tab system describe how to do this, but on my 25 foot Whaler, for example, it would be tough.
The other problem is that the recommended width of the Interceptor unit itself seems to be greater than the typical trim tab width. I have the ubiquitous 12" trim tabs but the literature for the Volvo QL Trim Tab system recommends the 450 mm units (17") not the 300 mounts (12") for a boat the size of mine. There is no easy to mount the 450 mm units on the transom of a 25 foot Whaler because there is not that much available width on the transom.
Furthermore, the strake which is the extension of the smirk on classic Whaler hulls will effectively block about half the flow of water the Interceptor unit needs. I do not think the Volvo QL Trim Tab system would have enough range of deployment to be effective in this case.
I do see one special situation where the Volvo QL Trim Tab system might be great: Whaler Drive equipped Whalers with single motors. With the Whaler Drive models (less than 27 feet) there is no way to mount conventional trim tabs. The Volvo QL Trim Tab system may be on alternative to owners of such craft who want a way to effectively correct for list while underway.
cooper1958nc posted 03-01-2008 05:49 PM ET (US)
Yes Mr Clark is correct, or at least more precise. Trim tabs do not need to be used together, although they do not work diametrically as do alierons, nor is there a setting to decrease lift as would an "up" alieron.
An interesting point about modern alierons is that the up alieron moves more than the down alieron, to combat adverse yaw that would otherwise arise from higher induced drag due to higher aoa on the down alieron wing.
I am still not sure I get how these Volvo things work though.
Plotman posted 03-02-2008 09:18 AM ET (US)
I have a friend who has these on a Bertram. They work great. Yes, they are counterintuitive to a layman, but if you understand something about fluid dynamics, they make a lot of sense. Full down has a fairly small cross-sectional projection compared to full-down on a standard tab.
We discussed these over two years ago http://continuouswave.com/ubb/Forum4/HTML/003912.html
I haven't put them on my whaler only because of the mounting issue Tom Clark brings up. I don't want that kind of hole in my boat.
andygere posted 03-03-2008 02:01 PM ET (US)
It seems that a spacer plate could be made of King Starboard, fiberglass or a similar material, such that the control wiring could be routed out the back of the QL tab, and up the transom as is done with traditional style tabs mounted on a Whaler transom. It's too bad that it's not available from the manufacturer. In general, the fewer holes below the waterline the better, especially for non foam-filled hulls.
The QL tabs are appealing to me because they do not interfere with kicker motors and the like on an already crowded Outrage 22 transom. I think this is an interesting product.
Plotman posted 03-03-2008 03:27 PM ET (US)
Brilliant Andy, brilliant.
I may have a project forthcoming...

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Author	Topic: New Trim Tab Type, Possibly Volvo-Penta QL System
whaler3	posted 02-29-2008 10:17 PM ET (US) Saw a new type trim tab the other day which I would describe as a piece of metal that comes straight down from the transom. It will retract or lower to put the bow angle down. It seems to me that it would be very bad for gas mileage as to the amount of drag. At the price of gas today I don't think I would want them on my boat!
jimh	posted 02-29-2008 11:58 PM ET (US) Perhaps you are talking about the Volvo QL Trim Tab system. It was introduced in 2005. It won an award for its innovative technique. Boston Whaler appears to be using the Volvo QL Trim Tab on their new 230 DAUNTLESS. I would take that as an endorsement. http://www.volvopentastore.com/ QLTrim_tabs_Complete_Systems_and_Spare_Parts/dm/cart_id. 089567208--category_id.344738--search_type.category--session_id. 551718392--store_id.366--view_id.344738 If you have some evidence or strong test results which show that the Volvo QL Trim Tab is not a good product or that it is inefficient and causes more drag than conventional trim tab systems, I encourage you to present your findings here and show us your test results. According to Volvo Penta, one of the advantages and benefits of their QL Trim Tab system is "less drag." This claim by Volvo Penta is in direct conflict with what I infer to be your claim that they have more drag than conventional trim tabs.
cooper1958nc	posted 03-01-2008 09:33 AM ET (US) I cannot tell from the advertisement how these things are supposed to work. Usually big manfacturers' claims are not wholly fictitious, but neither do manufacturers have the ability to alter physical laws. Conventional trim tabs act like alierons on an airplane wing, though they act together. They increase lift, but because they are just flat plates, their lift coefficient is low and their drag coefficient is high. Ease of installation and maintenance make them more feasible than a submerged wing (hydrofoil) with much better coefficients. Even though their drag is high, they can decrease overall drag by improving trim especially during planing transition. Sometimes improving trim is worth the drag as well. Does anyone know the theory behind these trim tabs?
jimh	posted 03-01-2008 10:17 AM ET (US) A seller of the Volvo-Penta QL Trim Tab system has a web page which shows the installation of these devices on several boats. There are many positive comments from the owners of the boats regarding the effectiveness of the Volvo-Penta QL Trim Tab, as might be expected in a promotional announcement. See http://www.great-water.com/pages/product_pages/QL_Trim_Sys.htm One notable feature is the lack of much projection aft from the transom, which eliminates interference with boarding ladders mounted on the transom. This may be one of the most appealing features of the Volvo-Penta QL Trim Tab system. There is also a publication available which shows the installation details. It appears that there are some electrical circuits which are conducted via a plug-in connector arrangement which have to pass through the transom of the boat at a point which could often be below the waterline. Such an installation technique may limit the applicability of this product on many classic Boston Whaler boats because of the Unibond hull construction technique. Generally there is not good access to the inboard face of the transom below the waterline on a Boston Whaler boat. See http://www.great-water.com/pdf/QL_Manuals/Trim_Sys_%20install.pdf for details.
Tom W Clark	posted 03-01-2008 11:19 AM ET (US) That's an interesting design and one I had never heard of before. The Volvo QL Trim Tab system works by creating a small dam, if you will, below the hull at the transom. This slows or stops the flow of water to create what is effectively a "hook" in the bottom of the hull, a fluid hook so to speak, or at least that is how I am reading the illustration. It does seem non-intuitive to think this could create less drag than a convention trim tab system, but I have to conclude that it could not have been brought to market if it did not at the very least, equal the performance of conventional trim tabs. cooper1958nc wrote: "Conventional trim tabs act like ailerons on an airplane wing, though they act together." No, that's not right. Trim tabs may be used together, but their greatest benefit is in being used independently to correct a list while underway. Furthermore, when trim tab are used together, they both travel in the same direction while ailerons always work in sync but always in opposite directions. Ailerons also travel both up and down whereas trim tabs travel only down. The more accurate comparison in aviation for trim tabs are flaps on the wing of an airplane. Flaps travel down only and change the angle of attack of the wing to alter the lift generated by it but also add drag.
Tom W Clark	posted 03-01-2008 11:44 AM ET (US) There are a couple problem for owners of Classic Whalers considering retrofitting the Volvo QL Trim Tab system. The wire from the Interceptor unit itself passes through the transom near the bottom of the hull, whereas on hydraulically operate trim tabs or electric Lencos, the hydraulic line or electrical cable passes through the transom at the top of the actuator/ram. On a Whaler hull there will be a lot of foam to drill through and drill through at an angle to have the electrical wire exit above the inner liner of a Whaler hull. The instruction for the Volvo QL Trim Tab system describe how to do this, but on my 25 foot Whaler, for example, it would be tough. The other problem is that the recommended width of the Interceptor unit itself seems to be greater than the typical trim tab width. I have the ubiquitous 12" trim tabs but the literature for the Volvo QL Trim Tab system recommends the 450 mm units (17") not the 300 mounts (12") for a boat the size of mine. There is no easy to mount the 450 mm units on the transom of a 25 foot Whaler because there is not that much available width on the transom. Furthermore, the strake which is the extension of the smirk on classic Whaler hulls will effectively block about half the flow of water the Interceptor unit needs. I do not think the Volvo QL Trim Tab system would have enough range of deployment to be effective in this case. I do see one special situation where the Volvo QL Trim Tab system might be great: Whaler Drive equipped Whalers with single motors. With the Whaler Drive models (less than 27 feet) there is no way to mount conventional trim tabs. The Volvo QL Trim Tab system may be on alternative to owners of such craft who want a way to effectively correct for list while underway.
cooper1958nc	posted 03-01-2008 05:49 PM ET (US) Yes Mr Clark is correct, or at least more precise. Trim tabs do not need to be used together, although they do not work diametrically as do alierons, nor is there a setting to decrease lift as would an "up" alieron. An interesting point about modern alierons is that the up alieron moves more than the down alieron, to combat adverse yaw that would otherwise arise from higher induced drag due to higher aoa on the down alieron wing. I am still not sure I get how these Volvo things work though.
Plotman	posted 03-02-2008 09:18 AM ET (US) I have a friend who has these on a Bertram. They work great. Yes, they are counterintuitive to a layman, but if you understand something about fluid dynamics, they make a lot of sense. Full down has a fairly small cross-sectional projection compared to full-down on a standard tab. We discussed these over two years ago http://continuouswave.com/ubb/Forum4/HTML/003912.html I haven't put them on my whaler only because of the mounting issue Tom Clark brings up. I don't want that kind of hole in my boat.
andygere	posted 03-03-2008 02:01 PM ET (US) It seems that a spacer plate could be made of King Starboard, fiberglass or a similar material, such that the control wiring could be routed out the back of the QL tab, and up the transom as is done with traditional style tabs mounted on a Whaler transom. It's too bad that it's not available from the manufacturer. In general, the fewer holes below the waterline the better, especially for non foam-filled hulls. The QL tabs are appealing to me because they do not interfere with kicker motors and the like on an already crowded Outrage 22 transom. I think this is an interesting product.
Plotman	posted 03-03-2008 03:27 PM ET (US) Brilliant Andy, brilliant. I may have a project forthcoming...