Hydrofoil Stabilizer

[QC]

Re: Hydrofoil Stabilizer

Well I have probably been the most vocal on this topic over the last coupla years, so I should probably respond . . .

As such, it's stern heavy.

That may be the key to satisfaction with 'foils . . . I don't know.

The Doelfin planed at 4 mph lower speed

That is consistent with all I have read (and trim tabs).

top end was exactly the same

That is not.

cruise speed was at 300 lower rpm

Define "cruise speed", not being sarcastic, but I continue to be baffled by this term, as it appears arbitrary by owner/operator.

gas mileage improved by 0.45 mpg

From what to what? I am curious about the percent improvement and the speed(s) (see above)

If Ole Evinrude had invented a fin, they would probably all have them now. But since the invention came from outside the industry, and is covered by enough patents, I believe that's the only reason they don't come standard. Besides, its not cool to admit that somebody else made your product better.

I submit that if that was true, then you would see them on at least some class of race boats. However, many race boats do have some type of trim tab . . . Especially offshore racers. There is a clue in that fact somewhere. Also, when was the last time you heard of a large corporation giving a rat's arse about a small company's patents? (See Dockside Chat patent thread).

Again, I am loosening up to the possibility that some boats might perform well with them. Your experience with fixed trim tabs is not very indicative or relative to the use of either Smart Tabs, or my preference, Helm Adjustable tabs. It is also fair to mention that there are many stories of how a Doelfin has made a boat feel unsafe and/or broken an anti-ventilation plate. Both are worth considering when discussing this . . .

Oh, BTW, welcome to iboats!!

 

[JimS123]

Re: Hydrofoil Stabilizer

The Stingray turns well with or without the foil, so there is no issue in that regard.

The Sea Nymph presented another problem. I have to run the motor tilted up to the top hole when the family is aboard (can only move people around to so many places). Under that setup, I got severe cavitation when turning above planing speed. The fin eliminated that completely. I can whip her around at any speed withpout loosing hookup.

I put tabs on the Stingray first, then added the Doelfin. You are correct, now it has both. My data was before with nothing, compared to after with both.

 

[Silvertip]

Re: Hydrofoil Stabilizer

You said: "My current rig is a 19' Stingray, 3L I/O, fitted with custom rear seats to hold portable gas tanks, plus a 10 HP kicker on an OMC bracket. As such, it's stern heavy. The prop is a double cupped SS custom re-pitched to 22" to get optimum results. I also have fixed mount trim tabs, which helped by allowing more trim without porpoising (thus faster speed). Still was not completely satisfied, though...had to try a Doelfin."

Apparently you have no data prior to adding fixed tabs other than less bow rise and no porpoising. You don't mention speed. Then you added the fin. Had you installed Smart Tabs or Helm adjustable tabs you very likely would have accomplished the same thing with both tab adjustability, lower planing speed, reduced or eliminated porpoising, good hole shot all with no additional stress on the outdrive. Data is good, but it needs to be base lined, and tracked progressively to the end. I too have been boating for more than 50 years and have removed fins from used boats I've owned because of foul handling. I even added one on my last boat to see if things had changed. They didn't and it too ended up in the trash. My current boat has stainless smart tabs and as I've said before, I'd have to hurt someone real bad if they attempted to make off with them. Being a realist, I don't doubt some boats react positively to a fin. Whether or not that's the best and only solution can only be proven with side by side comparisions. Not by adding one or the other in combination.

 

[JimS123]

Re: Hydrofoil Stabilizer

Re-read my last post. I have baseline data with nothing, after the tabs and after the foil. The comparison I spoke about in my first post was "before" vs. "with both". The only data I don't have is with only the foil and no tabs.

I'm a realist too. I'm sure that some rigs don't need them (I spoke about that before too). But in my experience, a lot of rigs can sure benefit from them. And, at an investment of only 24 bucks, its dumb to not try them.

I have no interest in the company, so I don't care if anybody buys them or not. I was just sharing my experience with others that asked the question in the first place.

 

[JimS123]

Re: Hydrofoil Stabilizer

Well I have probably been the most vocal on this topic over the last coupla years, so I should probably respond . . .



That may be the key to satisfaction with 'foils . . . I don't know.



That is consistent with all I have read (and trim tabs).



That is not.



Define "cruise speed", not being sarcastic, but I continue to be baffled by this term, as it appears arbitrary by owner/operator.



From what to what? I am curious about the percent improvement and the speed(s) (see above)



I submit that if that was true, then you would see them on at least some class of race boats. However, many race boats do have some type of trim tab . . . Especially offshore racers. There is a clue in that fact somewhere. Also, when was the last time you heard of a large corporation giving a rat's arse about a small company's patents? (See Dockside Chat patent thread).

Again, I am loosening up to the possibility that some boats might perform well with them. Your experience with fixed trim tabs is not very indicative or relative to the use of either Smart Tabs, or my preference, Helm Adjustable tabs. It is also fair to mention that there are many stories of how a Doelfin has made a boat feel unsafe and/or broken an anti-ventilation plate. Both are worth considering when discussing this . . .

Oh, BTW, welcome to iboats!!

My definition of cruise speed is the point where you get optimum fuel economy. My own personal level was derived from Powerboats Magazine's performance evaluation of the boat I have, plus the manufacturer's data.

My top speed is 51 mph. At my defined cruise speed (30 mph and 2800 rpm), my mileage was 8.2 mpg before, and 8.65 mpg after.

As far as losing speed, believe what you will, but my aluminum fishing boat lost no speed when I added the fin either. I admit my GPS is not a $500 model, but I don't doubt it's accuracy.

 

[jaxnjil]

Re: Hydrofoil Stabilizer

I seriously doubt your tri-hull was designed to perform that crappy. There is most likely something wrong with the boat, motor or overall setup.

Get the fin if you want, but then you will never know how the boat was meant to handle.

I know that some folks posted how well their boats handle with a fin. But the bottom line is boats and outboards were not designed to run with fins. If it was an accepted and proven addition, all outboards would come with them standard.... but they don't, do they.

Fins mask problems, they don't fix them.

______________________________________________________
i dont realy care one way or the other- fin or tab

the fact "out boards dont come with them" is lame as all boats dont come with tabs either.

but they don't, do they.

 

[QC]

Re: Hydrofoil Stabilizer

Well . . . hmmmmm . . . I have never seen any test data from any boat manufacturer, magazine, engine manufacturer etc. that achieved 8+ MPG with an I/O on anything over 16 ft. on plane. Stingray's own data on-line for their 18 footer with a Merc 3.0 is 5ish MPG, which is outstanding. I don't want to doubt this stuff, but the only info I could find on the 19 footer did not test the 3.0 although they do have a 4.3 that gets 6.2 MPG Also, their own site shows a max of around 48 MPH for the 3.0 in the 195 LR, that's with 1/4 fuel and one person. I am not trying to cause a fight, I just want to understand this stuff.

"Believe what you will" does not work for me. I want to "believe" in the data, but I am struggling . . . I do believe that your bow rise and planing speed have improved, and I did find some supporting stuff on improved cruising fuel economy with a Doelfin from an old Trailer Boats mag. Still not bolting anything to any of my AV plates

 

[JimS123]

Re: Hydrofoil Stabilizer

Oops, that's what I get for trying to work on a project with a deadline and go surfing when I take a break.

I stand corrected. My fuel efficiency figures should have read: 6.2 mpg before and 6.65 after the foil. Even that's not too shabby is it?

You are right about the figures not agreeing with Stingray's web site. That's because they don't publish data back that far. My boat is a SVB 190 SS, and the engine is the old 140 HP 3 liter. The hull is quite light for it's size, and it's a pre-ZP design with a shallower deadrise. If I recall correctly (and don't quote me with my track record today...LOL) I believe the bare hull was only about 1200 lbs. In fact, I do recall that PB Mag. criticized all of the Stingrays they tested that year, saying that the hull sides were too light. I liked it so I bought it anyway. Nevertheless, 23 years and 1600 running hours later (Some in Lake Erie), there's not a crack anywhere.

In any event, I was in too much of a hurry when I typed that post. I'm sorry if it caused any confusion.

 

[QC]

Re: Hydrofoil Stabilizer

Still impressive numbers Jim. Thanks for the clarification. I noticed that the existing 19s are more efficient than the 18s as well. Stingray's numbers have always been very good.

There is another thread above concerning a 16 footer and a 140 OB and a hydrofoil. My guess is that this boat is setup for high speed and conversely suffers with hole shot and bow rise. Ever see an OB race starting when most of them stand on end before they take off? I have read a lot about severe bow steer etc. when using a hydrofoil on high speed boats, so in that example it may have fixed an issue, but I am pretty sure led to another . . . In that example trim tabs would solve the bow rise and then exhibit none of the high speed issues except helping with any propoising if needed. I am sure, like I said above, that there are combos that can benefit from 'foils, however, in most cases dynamic trim tabs are a better solution (dynamic is my new word for trim tabs that move, helm adjustable or Smart Tabs as opposed to fixed, I was sick of writing both in every sentence . . . ) .

 

[EricR]

Re: Hydrofoil Stabilizer

I think since politics is now off limits in the dockside chat people have to go to war with the hydrofoilists.

Those who have success with them are either given the smackdown for not having technical data to back up the claims, or told they would do better with fixed tabs.

Diffrent strokes fer diff'ernt folks! Some boats do well with 'em some don't, JimS123 seems to have done good with them and has the data to back it up.

I will beat a hasty retreat to the sidelines now.

 

[JimS123]

Re: Hydrofoil Stabilizer

Here's an interesting addendum to the thread...

As I said, I couldn't be more happy with the 3 boats I now have Doel-Fin equipped. What got me started on this thread in the first place were the comments about breaking cavitation plates. With 23 years behind me on one boat, I wondered if I was on borrowed time.

Soooooo, I sent an e-mail along to the manufacturer asking for their comments. Their reply was short and to the point. As long as the foil is installed properly, meaning tight on the plate with no possible movement, then no damage should occur. In other words, any movement causing vibration may crack the lower unit.

Take it for what it's worth, I thought I'd pass it along.

 

[Hitech]

Re: Hydrofoil Stabilizer

...breaking cavitation plates...Soooooo, I sent an e-mail along to the manufacturer asking for their comments.

You didn't really expect the manufacturer of the fin to tell you not to use it as it could break the drive, did you?

Or did you email the manufacturer of the drive?

 

[scottfromoz]

Re: Hydrofoil Stabilizer

I havent read the thread, just this last page.

I have had Doelphin wings on an old boat. I then we-powered that boat (16 footer fiberglass half cab) and stuck on the latest Singray - it was very good. Then I got a 21 foot glass half cabin - much heavier boat. I put a SE Sports on the 115 Yamaha 2 stroke and it made a big difference. I then got smart and stuck on Bennett sport tabs and took off the fin and what a difference - ultimate control and none of the negatives of the fin (and there are a few including some safety issues in some conditions, such as a following sea). On any boat around the 19foot on mark (perhaps smaller if it has trim problems) made of glass in particular, I would have to say that trim tabs are not a luxury.

Cheers

 

[JimS123]

Re: Hydrofoil Stabilizer

You didn't really expect the manufacturer of the fin to tell you not to use it as it could break the drive, did you?

Or did you email the manufacturer of the drive?

No, and No!

But since this is such a widespread and massive problem, I was curious to hear what the manufacturer felt the cause was. Their Answer worked for me.

Once and for all, I totally agree that Bennett tabs are without question the best answer to the "problem". The only reason I didn't (haven't) bought them is because of price, plus the fact that it adds another button to have to fiddle with and a system that needs maintenance.

As far as my my little $600 aluminum fishing boat, the 24 buck fin was a no brainer compared to the tabs....plus the little critter doesnt even have a battery to power them.....ROFLOL.

 

[Hitech]

Re: Hydrofoil Stabilizer

But since this is such a widespread and massive problem, I was curious to hear what the manufacturer felt the cause was. Their Answer worked for me.

But, I could have told you their basic answer BEFORE you emailed them. They were going to say, "If installed and used according to the directions they will not cause any damage to the drive". That is basically what they said.

 

[JimS123]

Re: Hydrofoil Stabilizer

But, I could have told you their basic answer BEFORE you emailed them. They were going to say, "If installed and used according to the directions they will not cause any damage to the drive". That is basically what they said.

Not really!

They cited a specific installation deficiency and that's what I was looking for.

Time to give this thread a rest. Whether you are a proponent of tabs or fins, or couldn't care less how your boat performs, as long as you are happy with what you have, that's all that matters.