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ContinuousWave: Post-Classic Whalers
Turbol Lift Fins
|Author||Topic: Turbol Lift Fins|
posted 05-05-2004 01:19 PM ET (US)
Does anyone have a photo of the turbo lift fins that attach without drilling the anti-cavitation plate? I have searched the posts and inspite of all the great comments I couldn't find anyone that posted a photo that shows how they look or attach. I'm specifically interested in a 75 Merc 2-stroke installation but any installation will illustrate the concept.
Thanks in advance!!
posted 05-06-2004 09:11 AM ET (US)
I know this is a topic that has been beaten to death, but after spending quite a bit of time searching previous strings and looking for pics, all the links I found were dead. I would really appreciate it if some kind soul could post a link to a picture of a Turbo Lift fin before I order one.
Thanks again, I promise not to ask a third time.
posted 05-06-2004 09:54 AM ET (US)
posted 05-06-2004 04:56 PM ET (US)
Try this from 4whaler's page:
posted 05-06-2004 08:46 PM ET (US)
Thanks for the links, now I understand how it attaches. Based upon endorsements from this site I ordered one and will give it a try.
posted 05-06-2004 11:15 PM ET (US)
This isn't a joke, right? Someone is actually selling that "fin"?
posted 05-07-2004 12:32 AM ET (US)
check this out...in the course of a week..I install alot of accessories.....doel-phins, stingrays..etc....I personally feel that
that is the manufacturer of the engine be it mercury, honda, yamaha, john-rudes, the motorcycle dudes, thought that these fins were best for their motors performance...they would offer them as an option..
there are other courses of action to correct the problems they claim;and seem to in some instances, fix
more horsepower increases hole shot
a change in prop will decrease "time to get on plane"
extra blades...4 versus 3 will increase stability at speed in the turn and decrease time to get on plane
trim tabs, and triming the engine in the turn increases stability
posted 05-07-2004 02:16 AM ET (US)
To each his own, but I'm sure Yamaha's engineers would be appalled to see that contraption on one of their engines.
What will they think of next?
Perhaps a Big Foot gearcase, with larger anti-vent plate, would be more appropriate.
posted 05-07-2004 07:56 AM ET (US)
I am just trying to imagine the comments that would be made if an OEM engine was shown with such a device as delivered from the factory.
If people saw an OEM motor with a half-dozen bolts protruding from the lower unit in the area that runs submerged--with acorn nuts on them--and a crudely finished piece of bar stock bolted across the back, they'd start laughing.
The other thing that has me scratching my head: I thought these "fins" were supposed to run above the water when on plane? In the linked pictures above, this contraption is apparently being dragged around under water at some speed.
posted 05-07-2004 08:01 AM ET (US)
Interesting concept: what do they cost w/shipping?
posted 05-07-2004 10:05 AM ET (US)
JIM AND LHG
I enjoy your post the most...
you two Crack me up...lol
seasoned boaters....salty dogs...so logical
hahah keep the thought provoking questions coming..I enjoy the responses...good info...great entertainment...later
wish I was down in stuart for the rendezvous, I grew up in that area..used to get a kick outa seeing the mercury guys from lake X, in the ICW running the new mercurys on jack plates attached to old mako marine hulls hauling tail and jumping yacht wakes all day..what a job that would have been.
have a great weekend
posted 05-07-2004 11:51 AM ET (US)
Looks like there are still some questions about the turbo lift fins. I decided to give it a try after reading the experience of JohnJ80 and his 14 foot Dauntless. This is the same boat i just purchased. In about three weeks I'll have it launched for the first time and try all the great suggestions I have read on this site, elevating motor height, adding rabuds, etc. I am powering with a 75 Merc ELPTO 2-Stroke with an 13.25" x 21 three blade aluminum prop. I'll add the turbolift last and post the results. I admit it looks rather like a kludge, but based upon the previous owners comments I think I will need something to lower speed on plane and reduce porpoising. There is not much room on this small hull for the addition of trim tabs.
Regarding manufacturers concerns, I discount them entirely. They are making a product that needs to fit the largest number of applications. They make compromises that may not be the best for a specific installation. I doubt that Mercury designed my motor to be optimally applied to a 14 foot hull. At $165. I thought the turbo lift fin was worth a try. Maybe I can turn it into an anchor if it doesn't work, sort of a high tech danforth :-)
posted 05-07-2004 05:34 PM ET (US)
Actually, the contraption looks like it could make a good anchor. Just hook a chain to the aluminum crossbar, and you've got a high priced knock-off of a lightweight Fortress anchor.
posted 05-08-2004 09:44 AM ET (US)
I believe a 14 Dauntless should have a 75 or a 60 Bigfoot. The bigger lower unit and lower gear ratio 2.33:1 make sense. I have a 14 with a 75. I run a Powertech 19" SS prop. My wife can drive the boat with my son as an observer and pull my 208 Lb. butt up on one ski from a water start. Check the new E-tecs from evinrude. They are all essentially big foot lower units.(or petty close). Bigger lower units with a 2:1 gear ratio. You can run a steeper pitch and a larger diameter prop.
posted 05-08-2004 09:50 AM ET (US)
By the way, My boat came with 3 props. The 19"SS I mentioned before and 2 21" aluminum props. I know they say you can subtract 2 inches for SS but the performance of the 21 aluminums were terrible(bad hole shot and coming loose in the turns). The 19 SS works great and for dangerous waters (rocky) I just traded up one 21" for a 19" aluminum. I'll be sacrificing some top end but I'll get a better hole shot.
posted 05-08-2004 10:37 AM ET (US)
If the price of this "fin" is really $165, then I know this is a joke.
When a boat is on plane, most of the drag of the hull is gone. Only a small pad at the stern of the hull in in the water, and the hull drag is minimal. The biggest contributor of drag is the outboard motor's lower unit and the propeller itself. Take this test:
Get your boat going at 30-MPH. Take a length of 1-inch diameter pipe, hang over the side, and hold the pipe at 90-degrees to the water surface, submerge it about a foot, and hold it in place. The force required is substantial, probably more than can be held by most. Now scale up this drag to something of the size and shape of the lower unit. A lot of thrust is used just to push the lower unit through the water at 30-MPH.
So it seems counter-intuitive that you would want to increase the cross-section of the lower unit. However, perhaps there is something to be said about these appendages--they work because there is already so much thrust being used already to push the lower unit itself that a little extra to drag this fin around, too, hardly makes a difference.
The folks that use these fins all seem to be enthusiastic about them, so they must do something.
posted 05-08-2004 10:51 AM ET (US)
IMHO, a well-designed and properly loaded boat (which is what outboards are designed for) shouldn't need a "fin" to prevent porpoising, to get up on plane, and to remain on plane at lower speeds. But from what I read here on CW, that "well-designed" must not include the Dauntless series, and the Venturas based on them. And it seems the smaller the Dauntless, the more frequent the posts about porpoising and planing problems. Having the motor mounted as high as possible appears to be critical on these hulls. And it is also critical when using a fin, which if run submerged, can CONTRIBUTE to porpoising when trimmed out.
Again, IMHO, the Turbo-Lift is about the most butt-ugly thing you could put on a Whaler, but it appears to me it would be more effective than a Doel-Fin or Stingray, and has the advantage of no holes in the AV plate. One of the advantages of the Doel-Fin and StingRay is that they are black and tend to disappear rather than stand out. Would powdercoating the Turbo-Lift help there?
I'm not going to poke fun at, or bad-mouth Dauntless owners who use a fin, even the crude-looking Turbo-Lift. If it resolves the problems that appear to be inherent in that hull design, and makes their boat enjoyable, then it's definitely the way to go, and money well spent.
posted 05-08-2004 03:19 PM ET (US)
I see this type of rig most often on light weight, tunnel hull flats boats built specifically for use in shallow water such as encountered in South Texas. I believe it is supposed to allow you to raise your engine up higher with a jack plate while preventing blowouts. If used right, it is not supposed to create more drag. This page for another brand,(made by the push pole guys) explains it better. As you can see, they aren't cheap:
posted 05-08-2004 04:24 PM ET (US)
You all may think it is ugly but the Turbolift works very well. My 17 Dauntless has always porpoised in the 25 to 35 mph range unless the motor is trimmed in. I have the engine raised as high as it will go and have done all the things one could do. I ran a Bob's Machine shop plate one summer with marginal results.
Last summer I put a turbolift on and it really makes the boat operate much better in that 25 to 35 range. The boat comes onto the plane in a smoothe continuous fashion.
If you notice how it is built you will see that at higher speeds the fins will be out of the water and therefore not contribute drag. In by boat at high speed the center of pressure moves far enough aft so the boat's trim angle is reduced below the porpoising range.
I am sure that trim tabs would do the same thing as well as allowing for side to side trimming but the Turbolift works very well.
By the way the unit is pretty well built. The pictue in the ad is certainly a turn off and would have kept me from buying it except for JohnJ80's glowing endorsment last year.
posted 05-08-2004 09:26 PM ET (US)
A fin, properly installed needs to be at the very surface of the water when on a plane. If it is too low, it will increase the drag, probably really screw up the performance and probably make handling a mess. The fin, when on a plane, needs to ride at boundry of the water and the air.
The Dauntless is very sensitive to motor vertical height adjustment -- I mean VERY sensitive. As with any boat, always a collection of compromises, you make to get the performance you are looking for. In the case of the smaller Dauntless models, the tradeoff is the very great seakeeping ability that boat exhibits and its handling on bigger water. For that, you need to make sure you set up your motor correctly. Whaler doesn't help much with this, they recommend the motor to be mounted, IMHO, far too low. The Dauntless hulls perform exceptionally well in chop or rough conditions than almost any other hull in that size of boat - especially the smaller ones.
The Turbo Lift must be mounted on a motor that is mounted relatively high. It will not work well if it is mounted at Whaler's recommended height (heck, i don't think Whaler has it right on their height specs anyhow). When it is mounted properly, the trim range is greatly increased, the hole shot is very much improved and the boat performs very much better in the cruising range of 25-35MPH. Above that, it isn't needed.
The manufacturers of motors can't possibly anticipate the loading, the sea conditions, the usage or the hull configurations of each of the boats their motors eventually get mounted on. The amount of lift required at the stern varies greatly over all of these applications would be my guess.
So, this must cost me an enormous amount of performance to have this fin since my boat outperforms the prop calculator and gets 41MPH out of a 75HP engine at 5100 RPM with a 13x15 stiletto prop. If there is significantly more drag there than without the fin, then there must be some other mojo that makes up for it. My bet is that overall, the drag is reduced much more by raising the motor than it is increased (if at all) by adding the fin on a properly adjusted motor.
I did a whole bunch of internet searches on porpoising. There are a number of engineering studies (white papers published and IIRC, a PhD dissertation), but none of them nail down the cause of porpoising and it is still largely speculative as to the causes.
Additionally, all the collective wisdom of those that haven't dealt with it is also all over the map and largely incorrect and often contradictory. The only thing I think one can say on this subject is that it needs to be solved experimentally but that it can be solved with great results (been there and done that too). In the case of the smaller Dauntless hulls, the performance with proper adjustment and a fin will significantly exceed that of the boat set up to Whaler's specs.
You just have to experiment. Takes about 2 hours.
posted 05-08-2004 11:36 PM ET (US)
My neighbor had those 'fins' on his 25hp Merc and took them off last week. He stated boat performed better but now he's stuck with all those holes in the cav plate. Sad, how so many can be fooled with this prosthetic 'device'.
P.S. They are now in the custody of Waste Management.
posted 05-08-2004 11:42 PM ET (US)
Oops, my neighbors was one of those black hard rubber jobs, can't recall the name, if I heard it I'd want to forget it.
It appears to have the same principle in mind, that is making ones OEM motor FUGLY, while creating a conversation piece for the nautically infirm.
posted 05-09-2004 07:17 AM ET (US)
I always get a little confused (or maybe amused) when I read the threads on fins.
It seems to me there are at least two types on the market...the airfoil design (doel fin, sting ray, etc) and the enlarged cavitation plate design (the original subject here).
The airfoils or hydrofoils are shaped to provide lift. That is the top surface is rounded and the bottom is more flat. To work as intended it must be submerged so that water is flowing over both surfaces. It should generate lift even when its position is almost parallel to the direction of the boat (like an airplane wing). I am not saying it is always operated in its intended fashion... just that is what is intented.
I am not sure what principle is behind the other design, but it in some cases appears to act like a trim tab attached to the engine. In other cases (like on the Texas flats) these things are needed becase the engines are jacked up so that the props are at water level. In either case it seems desirable to operate them so that the top surface does see a lot of water.
As far as drag is concern, I think jimh's pipe example is a little extreme. A cylindral shape produces a large drag. If you take the same 1" pipe and add a gradual taper to the rear (a fin?) the drag will be significantly reduced. Then make the thing a little thinner (say 1/2" or the largest thickness of the doel fin) and the drag will be reduced further.
I do agree with jimh, that most performance problems can be improved by changing prop pitch, adjusting engine position and redistributing boat load. I wish I had read his comments before installing the doel fin.
posted 05-09-2004 08:21 AM ET (US)
Here is a link to a photograph mentioned above. This shows the "fin" in operation:
Compare to this photograph showing a similar engine with no fin, mounted high enough so the anti-ventilation plate on the engine runs at the surface when the boat is on plane:
In the first photograph, if there is a fin or other appendage attached, it must still be submerged. In the second photograph, there is no fin or appendage attached. The engine in running with the OEM anti-ventilation plate just at the surface of the water.
posted 05-09-2004 09:14 AM ET (US)
In the first pic the engine is in a high position, but there is no jackplate. The fin is submerged generating increased drag. To get more lift, wouldn't you have to adjust the trim, which in turn would generate more drag? Seems like you could calculate just how inefficient you where operating through the prop calculator in the reference section.
In the second figure, is the engine on a jackplate? Is the goal here to generate lift or keep water on the prop?
By the way, is there any text related to the second figure?
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