Hydrofoil query again..............sorry.

[guy74]

Re: Hydrofoil query again..............sorry.

Well you answered this well in your next line . . . it is cost . . . With that said, almost anything decent, above 23 ft. or so, and helm adjustable tabs are standard

First off I'm not attacking the use of trim tabs like so many of you are the use of a foil. I think they are both good tools to make your boat do what you want it to do, either one will help in some cases, maybe not in others. I like the results that I get from my foil, and the price is much less than helm adjustable trim tabs. I'm sorry for my lack of experience on boats longer than 20ft, we don't have very many of that size around here. Each to their own, I just thought he was asking for opinions which is what we all are giving him and others who read this thread. And a little disagreement between the two sides is good fun

 

[wca_tim]

Re: Hydrofoil query again..............sorry.

I bought an 18 foot boat with mercruiser outdrive and blown engine, replaced engine, etc... There was a hydrofoil on it and I left it there at first. After taking it off, I gained a couple mph on top end that I think was a driect result. It DID make a huge difference in bow rise and low end planing speed. I think it takes much tighter turns without the whale tail on it all other things being equal. I'm going to try tabs in the next month or so - especially since I get a significant amount of mid range porpoising with my faster props in the current configuration.

in short, my very limited experience was that the hydrofoil improved planing and stability in a straight line significantly,perhaps knocked off a mph or two on top end and detracted from cornering - especially hard turns at higher speeds, i.e 40-50 mph range.

 

[Nandy]

Re: Hydrofoil query again..............sorry.

Bigmax, as you can see, the group is very divided. Some love it, some hate it, some haven't even try it and hate it. If you can live with 4 holes in your cavitation plate go for it. Heck, you can always put some marintech and paint those holes. I had it and made a huge difference in my boat.

 

[Drowned Rat]

Re: Hydrofoil query again..............sorry.

Even if they do allow planing at lower speeds, why would you want all that energy transfer going into your outdrive? For less than $200 you can have real trim tabs mounted to the hull that really make a difference. I've used both and Smart Tabs are night and day compared to hydrofoils.

 

[QC]

Re: Hydrofoil query again..............sorry.

guy74,

I wasn't attacking you either, just noting that cost is the answer to why the not standard deal. On the other side of the coin, it would cost IO and OB manufacturers next to nothing to install foils, or cast new wider cavitation plates, but they don't. They all compete for fuel economy, speed, etc. so why not? NO race boats use foils, but many have trim tabs . . . Just clarifying the question you were clarifying . . .

 

[guy74]

Re: Hydrofoil query again..............sorry.

QC,
No harm meant by me either, I think the two sides on this are beating a dead horse. Kinda a Chevy--Ford thing. I got both and they are both good.
Good Day,
Brian

 

[BIGMAX]

Re: Hydrofoil query again..............sorry.

Jeeeeez guys (and gals if any), now you have me "itching" to get the boat back in the water in winter just to "try" a foil out. But I don't think so - I like the sound of the tabs and will more than likely give that a shot. Thanks for the feedback, you have all really kinda sort of helped me.

 

[Nandy]

Re: Hydrofoil query again..............sorry.

Based on the advised posted here I would say that if you have the money go with the tabs. That would be my "common sense" advise. If you dont have or dont want to spend the $200.00 plus or dont want to make holes in your transom try the foils.
Im done, the Chevy guy! lol!

 

[Black Snow Slide]

Re: Hydrofoil query again..............sorry.

I posted on another boating forum if anyone has ever had a bad experiance with the Smart Tabs. The main problem I heard back was they ordered the gas ram too strong. The customer service at Smart Tabs was top shelf and got people the correct ram for there boat. Also heard that if they called them prior to ordering they would have ordered correctly the first time. Instalation is strait foward.
The performance gains are unanimous across the board. Much better out of the hole. Better plaining at low speed. Torque steer drasticly reduced. Headway speed handleing improved. Strong improvements in chopy water. One thing that suprised me was not a single person said my boat ran better without them.
I helped a friend install them on his Glastron SX195 just prior to his last run of the year. I had never heard of them untill I saw the box. I have been out on his boat many times without them. The performance gains other people have said about the Smart Tabs are reality on his boat as well. It was increadable.
I have the Smart Tabs for my boat sitting in a box and will be installed befor the first run in 2008.
Continue to do your reasearch and you will come to the right decision on your boat.
My personal oppinion on Hydro-foils. I think the motor is desighned to propell the boat foward and backward, not to lift it up. Good luck with your choices.

 

[sickwilly]

Re: Hydrofoil query again..............sorry.

My personal oppinion on Hydro-foils. I think the motor is desighned to propell the boat foward and backward, not to lift it up. Good luck with your choices.

Then why do we trim our boats with the out drive?

The logic usually goes, if foils are such an improvement, then why doesn't merc or volvo offer them?

Same logic applies to tabs -- if tabs are such an improvement, then why don't boat manufactures make them standard?

There are just too many variables -- preferred use of the boat, type of prop, prop pitch, length and weight of the boat, load of the boat, horse power, etc, that no one size fits all solution is optimal.

IMHO, this is one the things great about boats and boating.

 

[mfcoloradonf]

Re: Hydrofoil query again..............sorry.

Bigmax, Did you finally get the Smart tab SX? I have to say that I used both. I have had some positive experience with the foils on two of my boats, but I always lost a couple of mph on the top end. On my current boat 16 alum bass boat I needed quicker lift and was not impressed with the Stingray foils. The doelfins foils worked better but that was on a different boat. I figured I would try the SX, all I wanted was to get on plane faster. All of the other claims on their site I thought was just hype. Boy was I stunned on how these sx performed. Everything they said came true and they were a breeze to install. I like the plastic sx cuz you can go on fresh and saltwater. My boat powered with a 40hp goes on a plane in about one second, no lie. I boat out on the Potomac River which is a huge tidal river that can get really choppy. I had it out there on some moderate chop a month ago and at full throttle my boat didn't bounce hard at all. It was almost like a whole different boat. It will be hard saying goodbye to this boat when I change up for a flats boat.

 

[stevens]

Re: Hydrofoil query again..............sorry.

A boating site over here just tested three foils on the same boat ("Foils - almost a complete waste"). Here's a link to the test: (link) (all in Norwegian, I'm afraid).

Conclusions:

"Tests show time after time that foils or hydrofoils yield very little. The top-end speed goes down and the gas consumption is not reduced." and ...."The alternatives to foils are a bigger engine or trim tabs."

 

[sickwilly]

Re: Hydrofoil query again..............sorry.

since I can't read the article, can you help with two things:

What size and HP boat?

Did they address how they foil affected minimum planing speed?

 

[stevens]

Re: Hydrofoil query again..............sorry.

OK, here's a complete translation of the article:

--- quote ---

Foils - almost a complete waste

Published by: Paul
04-dec-2007

Tests show time after time that foils or hydrofoils yield very little. The top-end speed goes down and the gas consumption is not reduced.

A heavy boat planes out more easily and accelerates better with foils, but the differences are marginal.

The three foils in this test were tried on a 4.5 meter RIB with a 40 HP engine. There were two people aboard. In addition, the boat was loaded with 100 kilos aft and 30 kilos up front. The engine struggled to get the boat on plane. Without the foils, 0-16 knots took 9.6 seconds. With the small Attwood foil, it took 8.6 seconds. If you are to mount a foil, this is the best of these three. But, our advise is not to do it. You have to drill holes in the cavitation plate. That ruins the corrosion protection the engine has from the factory.

This and other tests show that it is of minor importance how the foil is shaped, but that the foil mustn't be too big. A loss of top-end speed of 3.5 knots is not acceptable. Probably, the loss of speed increases with lighter boats. The foil creates added water drag without contributing to the boat going more lightly in the water.

If the boat is always heavily loaded and barely gets on plane, you may think about mounting foils. You should however check that the prop is right. Regardless of load, the outboard engine should reach the RPM the manufacturer prescribes at full speed. Normally, there are two people aboard during a test. If there's always six people aboard, it would be better to use a lighter prop (with less pitch). The alternatives to foils are a bigger engine or trim tabs.

Acceleration 0-16 knots:
Without hydrofoil: 9,6 sec
With Attwood small: 8,6 sec
With Attwood large: 9,6 sec
With Doelfin: 8,8 sec

Top-end speed:
Wthout Hydrofoil: 24,8 knots
With Attwood small: 23,8 knots
With Attwood large: 21,3 knots
With Doelfin: 23,2 knots

Lowest consumption:
4500 rpm, approx. 19 knots
Without hydrofoil: 0,46 l/nm
With Attwood small: 0,46 l/nm
With Attwood large: 0,50 l/nm
With Doelfin: 0,50 l/nm

--- end of quote ---

I have no opinion on this as I have never tried a foil myself (but I did like my Smart Tabs). I linked to the article because it is the first time I've seen published a test of foil vs. no-foil, and a test of different foils on the same boat. For all I know, there might be other boat/engine/load/speed combinations where a foil actually works well.

 

[roozterdvx]

Re: Hydrofoil query again..............sorry.

Bought my current boat with a Stingray foil installed by previous owner...took it off when I found the anti-vent plate BROKEN from the stress! It must have been cracked for some time, the chunk which broke off showed fresh break as well as some which was oxidized.
Lucky for me I can weld aluminum and was able to repair it.
Granted, I own fairly good sized boat, 25+ feet, and it did make a noticable difference. I don't know why the P/O installed it, the boat has hydraulic trim tabs.
The foil did make a noticable difference as I said. The boat came up on plane easier and I would guess it would help economy.
I also had installed a 300SE foil on a Tahoe Q4S 19+ ft. bowrider which I used to own. Bought the boat new and it had a Merc 3.0 135hp I/O. Used to get 43mph without the foil, and in similar conditions, 42mph with the foil installed. (GPS verified speeds). The boat was borderline on power and the foil really helped holeshot and planing. The advantage to that motor/drive...burned a little more than 1/2 of the fuel of the 4.3 Merc I/O and only 3-4mph less top speed, as advertised by Merc. I'm sure the 4.3 accelerates quicker.

Just my $.02....with the boat I now have, no foil.
Foils have their place, some boats need a little help, and money is definately a factor, but I would be careful about checking the A/V plate for stress cracks before breaking off a chunk like I did. (The only thing holding the broken piece of plate, was the foil bolts). It's much easier to repair a crack than to replace a missing piece.


Good luck.

 

[180shabah]

Re: Hydrofoil query again..............sorry.

...Bought the boat new and it had a Merc 3.0 135hp I/O.......The advantage to that motor/drive...burned a little more than 1/2 of the fuel of the 4.3 Merc I/O and only 3-4mph less top speed, as advertised by Merc...

Are you suggesting that an upgrade to the 4.3 on this boat would have nearly doubled the fuel use????? AND that it was Mercruiser that said this????

Sounds more like some cleavor data manipulation(showing some gph graphs, which without speed or other data are mostly irrelevent) by a salesperson who wanted to sell the base boat that was in stock rather than deal with a special order.

 

[180shabah]

Re: Hydrofoil query again..............sorry.

OK. I went and did some searching, seems there were not many tests of 3.0 powred Tahoe's, so I couldn't find identicle boats except for power. I ended up with a Q4SF, 18'1" and 2270lbs w/3.0L and a regular Q4, 19'5' and 2346lbs w/4.3L. Since the 3.0 is in the smaller and lighter boat, the comparison, although not perfect, will be close.

The best cruise economy,5.08 MPG, on the 3.0 was achieved at 3500RPM at 27.7MPH. The best economy on the 4.3 was 4.78MPG turning 3000RPM and running 2MPH faster at 29.7MPH.

WOT performance for the 3.0 was 4700RPM, 41.1MPH and 3.56MPG
WOT performance for the 4.3 was 4850RPM, 51.1MPH and 3.41MPG

The economy numbers are very close, but that is expected, any given hull will require X amount of power to go Y MPH, in a perfect world both boats would get identicle economy at the same speeds, but in the real world we have to deal with weight differences, volumetric efficiency(that changes with different engine speeds), etc....

If the data was more detailed you would find that the MPG number would be even closer if we could compare at the same speed.

Also, on a real world note, the 3.0 has a narrower window where it achieves more than 4MPG from 20-35MPH(ish) while the 4.3 does this from the same 20MPH to 43MPH(ish), That should add some confusion - the 4.3 gets better economy going speeds that the 3.0 can't even get to.

*All numbers were taken from tests on boattest.com(it was the only place I could find 3.0 data)

**All tests were conducted without hydrofoils(and you thought this was off topic)

 

[Mr Happy]

Re: Hydrofoil query again..............sorry.

Just got into boating 7 years ago. First boat was Four Winns 170 Freedom(3.0 4 cylinder, 2,300 pounds) with a hydro foil. I thought it was good but I really had no reference point. Two years later bought a Sea Ray 175 (3.0 L. 4 cylinder, 2,300 lb) it also had a hydro foil that ran great. This boat is a Sea Ray 225Br (5.7 L 8 cylinder, 4,500 lb.). This one has bennett trim tabs. There is a world of difference.

I am sure we all have had 4 to 8 people on our boats. When you have 3 or 4 adults and 2 of them are sitting on the same side as you are(500 to 700 + pounds) you KNOW it. With the use of trim tabs you can level the boat. Same as when you are going against/across the tides or winds you can press the tabs and level the boat out.


I do not know about smart tabs, therefore I can not comment one way or another.

 

[JimS123]

Re: Hydrofoil query again..............sorry.

I replied to a thread similar to this before, so rather than post all my data again and be subject to ridicule, this reply is for the person that asked the question in the first place.

My two boats have foils, and this past summer we installed one on my son's brand new cuddy as well.

I can tell you this...we will never be without them. On my big boat, I put on tabs first, and when I still wasn't satisfied with the results, I added the foil. Together, they are fantastic.

I laugh when anybody talks about breaking the cavitation plate. My goodness, if that was a big problem the foil would have been out of business 20 years ago....LOL

Oh, btw, my first Doelfin has been on for 23 seasons now.

 

[MikDee]

Re: Hydrofoil query again..............sorry.

My 19' Bayliner Ski boat (Cobra style copy) with a 125hp Force outboard came with a Doel fin hydrofoil. I ran the boat a coupla times just the way it was, then at a later date took the Doel fin off. I noticed it took longer to get on plane (even though this hull design is made to plane off fast & easy for skiing), it also appeared that the boat had more lift without it, causing it to become airborne from the chop, and slam down hard more easily, and finally in turns the boat leans quite a bit now, and I might have lost 1-2mph, but it is negligable, considering the disadvantages I experienced without it. Next season I intend to put the Doel fin back on, because I like the out of the hole improvement, plus the boat staying more planted in the water (instead of going airborne at times at higher speeds), and finally, staying more level in the turns on plane, and I'll accept scrubbing a bit more speed. It appears to work for me, at least for now, until I get smart tabs to compare.