Hydrofoil on the 2120

[Claymar]

One my first discoveries when I put my 2120 SC on the water was that she drug her tail and slammed pretty hard uphill without full tabs and the 150 tucked all the way in.

After watching some of the post here on CP on hydrofoils I decided to give it a try going for the SE sport primarly for cost, 50 bucks as compared to 100+ for some of the sexier models.

For anyone else thinking along those lines I thought I might share my experiance and repeat what most have said about installing one.

The boats performance, without splitting hairs, was dramatic. With both tabs full up and the motor trim at a little greater then 50% I could feel her butt pop right out of the water. I didnt try to time how quick it took to plane but judging the distance out of harbor that it usually took me I would say it was on plane in half the distance.

One of the things others have said is that the foil makes the tabs more sensitive. I found that to be true as well. I found I was using about half the tab and that it took only a slight amount to even the keel in quartering seas or wind.

I know some folks speak of increased drag and lower tops ends but I have a hard time shedding a tear over one or two knots less at top end wihen the boat rides so much better. I actually had it up to 33 MPH @ 5300 rpms which, I think, is pretty close to Yamahas numbers.

Getting more of this boats bow in the water definatly made a good boat better.

I am now thoroughly sold on hydrofoils. Might quibble on brands and designs but the concept sure seems sound.

 

[Porkchunker]

5,300 rpm is low...if that is your WOT rpm, the motor is bogging and stressed more than it should be.

WOT rpm should be almost touching the max rpm. In my case, Yamaha says my F-115s max rpm should be between 5,000 and 6,000 rpm. I'm propped to reach 5,800 when the water is glass, the tabs are fully retracted, and the motor is trimmed up as high as I can get it without causing ventilation (where the prop pulls air from the surface above).

Even with a hydrofoil on each motor, my WOT top speed only dropped by 1 mph. But...as you discovered, my tabs are now much more sensitive, and run in the fully retracted position a lot of the time. I pop up on plane and can stay there at a much lower speed (down around 12-14 kts).

With the weight of two 4-strokes on the back, I believe the center of gravity of my boat moved to the rear enough to make the 12"x12" tabs ineffective. Adding those two plates made her a different boat.

Glad to hear it all worked out for you.

 

[Bryan 2530]

Porkchunker - what hydrofoils did you use? I'm trying to decide to go with bigger tabs or plates like you guys are talking about. On some days it seems the tabs on my 2530 are almost non existent.

There is some discussion about whether or not there is room for bigger tabs with twins. Some think the big tabs would cause the props to grab air.

What does the Parker population think? Tabs or plates for twins???

 

[Claymar]

5300 is not my WOT. On the test run with the hydroifoil that number represents my ENT , End of my Nerve Threshold.

This time of year in Southern California one tends to become airborne somewhere around 25 to 30 miles an hour in a boat the size of a 2120. Happen to have made the foils maiden run on a good day but still not a WOT day.

Havent checked the Yamaha site but I seem to remember the data scale at various RPM's had their test boat doing around the same speed at those RPM's.

I tend to speak in general terms as I'm not much into nit-picking performance, if that were the case I probably would have something other then the 150 bolted to the butt-end.

From all I've read here on CP and my own experiance with the 2120 she comes butt heavy out of the chute with a bias towards a pounding porpoise. Good news is that it is an easily corrected problem.

 

[Outta Here]

On some days it seems the tabs on my 2530 are almost non existent.

There is some discussion about whether or not there is room for bigger tabs with twins. Some think the big tabs would cause the props to grab air.
Tabs or plates for twins???

You can measure for larger tabs. Bennett says stay 8" from centerline of o/b. The tab can go to your reverse chine (the 3-4" turndown at each corner of transom). You can get 9' or 12" Bennetts (to compensate for a possible lack of width on transom), and you can get the tabs w/fins. I would try this first. Why not contact TabMan at Bennett?

As far as things added on the motor....well, the've been around over three decades, never been big sellers. Used to be sold as "WhaleTails", later as "DuelFins", now the've been re-invented by someone in Finland (?). The've caught on here at CP faster than a California Wild Fire.

 

[captbone]

I got the standard $29.95 Doel-fins that you can get a West Marine.

They made a huge difference and I would bet that they give the same results as the more expensive ones.

 

[Porkchunker]

Porkchunker - what hydrofoils did you use? I'm trying to decide to go with bigger tabs or plates like you guys are talking about. On some days it seems the tabs on my 2530 are almost non existent...

I went with the "CoBra" plates from Cabela's They are a fairly straight plate (very slight down turn at the tail), that bolts to the bottom of the anti-ventilation plate of the lower unit. They are not the same as the "Whale Tails," "Doel Fin," or "Hydrofoils," that bolt onto the top or ends of the anti-ventilation plate. The style that bolts onto the top or ends of the anti-ventilation plate were notorious for breaking the plate. These CoBra plates go on the bottom, so the upward pressure of the plate is spread across the entire surface of the anti-ventilation plate.

With twins, you cannot go as wide with the tabs without inteferring with the water passing past the motor, as you could if you had a single. Most of those 18" and 24" plates folks are installing are on singles. In my case, I had just purchased the boat and discovered that it was butt heavy and the tabs ineffective. I didn't have the money to swap the tabs, so I went with a cheaper solution...the CoBra plates. Since I had done my homework, I chose those plates over all other manufacturers and models because they bolt to the bottom of the anti-ventilation plate. They have been there for 4 seasons, and have performed great. You could probably install 18" wide tabs on your boat, move the batteries forward, move other weight forward, and accomplish something similar. For me the CoBra plates were easier and cheaper.

Dave

aka

 

[Megabyte]

But ya know...? If it works for a member, that's a good thing. :wink:

 

[grouperjim]

Brian:

I have the bigger tabs and the Permatrim. Get the hydrofoil/Perma, forget the bigger tabs. With a foil or Permatrim the smaller tabs are more than adequate. The Cobras are pretty sexy looking, the Permas are not as sexy but sure are effective as they act more like an extra trim tab than a foil.

jim

 

[Claymar]

Porkchunker - what hydrofoils did you use? I'm trying to decide to go with bigger tabs or plates like you guys are talking about. On some days it seems the tabs on my 2530 are almost non existent...

The style that bolts onto the top or ends of the anti-ventilation plate were notorious for breaking the plate. These CoBra plates go on the bottom, so the upward pressure of the plate is spread across the entire surface of the anti-ventilation plate.

aka

I've had a couple of people mention the fear of breaking the anti-vent plate but have never had anyone say it actually happened to them or had actually seen it happen, any real reports of that? These things sell like hotcakes, seems like if it were that prevalent a problem sales would come to a skidding halt.

 

[grouperjim]

Mine and my buddies' boat are holding up well with the Permas. Their website says there has been no reports of any damage caused by a Perma. There is also a thread on THT dedicated to Permas. No one has reported any damage to AV plates. You know that if there was a problem, people on THT would be screaming bloody murder about it.

jim

 

[MIQ]

Porkchunker,

How do you attach the Cobra Plate? I looked in cabelas and the illustration doesnt show any bold holes to hold it on... am I missing something?

 

[Porkchunker]

There are six holes in the plate. I used two Vise-Grips (the kind welders use) to hold the plate in place and then drilled the anti-ventilation plate using the Cobra Plate as the template. The SS bolts and nuts come with the plate.

Dave

aka

 

[greatcir]

I installed a Doel on my 2120 150 and it helped get on plane quicker with a cost of 1 or 2 MPH WOT. It scared me the first time I put it in a hard turn at speed because it snapped the boat around quickly. Then someone here posted a photo (maybe a link?) to a cracked cavitation plate with a Doel still attached on top. (I could not find it under Search) That also scared me.

I took my Doel off and installed a Cobra on the bottom of the plate. To me it performed about the same as the Doel but it was much stronger and a bit larger. No question it is better installed under the plate since all these hydrofoil plates generate so much lift on the motor.

I also ran with 100 pounds of lead in the bow and no hydrofoil plate and got about the same performance - quicker to plane and the bow stays about 4 degrees lower.

I did not like the snap turns or the extra width of the hydrofoils and I did not like toting around an extra 100 pounds in the bow so I removed all of it.

Next I had my factory supplied 3 blade ss 14 1/4 X 16 prop cupped and again I get better performance (lost maybe 200 rpm wot) but the boat still tended to porpoise at WOT.

Waiting now (should be here this week) for a Yamaha Reliance prop which the Yamaha engineers think might be the best compromise as it will be 14 1/2 X 15 ss 3 blade. They told me it was designed for the 150 specifically.

If it does as they think it will, I will again check to see if the cavitation plate finally rides up flush on top of the water and if the porpoising stops at wot. If not my last gasp will be to raise the motor a notch.

Love boat research with good tech support like this forum, Yamaha, and Parker. .............Pete

 

[Principal Reeler]

I have the same CoBra unit from Cabalas and agree with Porkchunker.

I feel more comfortable knowing that by being attached to the bottom of the lower unit plate there is less stress.

I do notice a difference in performance and handling, AND it a lot less expensive than PermaTrim.

Mac

 

[Principal Reeler]

P.S.

I have a 2310 with a 2-stroke 150 hp Yammie.