Hydrofoils

[lakelivin]

Re: Hydrofoils

Ben, Cobra stabilizers have several models. Last I looked, they had a steel alloy for around $45, an aluminum for around $55, and a stainlesss steel for around $90. <br /><br />I have the aluminum one, don't think it's that much more expensive than some of the other decent brand models.<br /><br />Note that I'm not making the case that a Cobra stabilizer is as good or better than tabs (I've never tried them). I'm just saying that for my 17', 175hp bowrider it works so well (for close to $50.00) that I have no temptation to spend the money on a tab upgrade. <br /><br />NautiJohn, I've got a Seaswirl which I'm pretty sure is 3-4" wider than most comparable boats it's size. Maybe thats why I've never noticed any side to side stability issues after I put the Cobra on .

 

[Jdeagro]

Re: Hydrofoils

Lakelivin;<br /><br />You are correct in assuming that not every boat will react the same with the use of a hydrofoil. It depends on the existing hull design, the height of the cavitation plate, the weight of the boat, etc. What I am attempting to point out is that any time you add additional planing surface that is rigid, to the boat (the out drive and motor in this case becomes an extension of the hull) you will change the handling characteristics of the boat. The increased lift is assured, the lower planing speed is probable depending on the size of the hydrofoil, the reduced bow rise is also a given. The loss of top speed is typical (as reported by most users) which simply means that the boat is not running in the correct attitude (not efficient). A loss of as little 2 MPH on a boat has a top speed of 40 to 45 mph is a loss of 5%, which will also translate in an equal loss in fuel economy. In hard number, the average boat owner use his boat 55 to 60 hours per year. The average fuel consumption of an open bow 19 to 20 ft (v6) boat is 6.0 to 7.5 gal. per hour. That is about 450 gal. per season. Times $2.00 per gallon is $900.00, and 5% of that is $36 to $45 per season in extra fuel cost. <br /><br />Obviously the average boater does not run his boat at WOT all the time - in fact rarely, but every magazine boat test shows that the typical cruising speed of 22 to 27 MPH (for these 19 to 20 ft boat) use more fuel than higher speed. If you check the RPMs with and without the hydrofoil at these speeds you will find that the engine turns more RPMs per mile per hour with the foils. Obviously more fuel consumption. <br /><br />In short, if you impact the top speed of the boat negatively you reduce the hull efficiency and fuel efficiency. Where the hydrofoil will help is at the low end of the speed range (17 to 19 MPH) as the extra lift will help the boat plane easier. Once the boat is on plane and running at cruising speed (24 mph and up) the extra lift progressively reduces the hull efficiency. <br /><br />Depending on your use, it is most likely that a hydrofoil will add About $40.00 per year to your fuel cost.<br /><br />Conversely, Trailer Boats Magazine tests showed that Smart Tabs improved fuel economy on a 19 ft Maxum with a 5.0 ltr. V8 as follows:<br />RPMs MPH % Improved w/Tabs<br />1000 5.3 3.6%<br />1500 8.2 18.5%<br />2000 10.3 23.5%<br />2500 24.5 3.6%<br />3000 31.0 0%<br />3500 36.0 0%<br />4000 43.0 8.0%<br />4500 47.0 0%<br /><br />Two important factors:<br />1) The test showed that the boat stayed on plane a 2100 RPMs and 15 MPH but fuel economy was not tested at this range before and after because the boat would not plane at this speed without the tabs.<br /><br />2) The boat reached its most efficient Hull speed at between 31 and 36 MPH. The Tabs did not affect the performance in either direction. However, once the boat was pushed beyond the best hull speed the Smart Tabs helped the speed and fuel efficiency. They also added 2 MPH to the top speed.<br /><br />If you want to average all of the tested speed ranges the Smart Tabs improved the MPG by 7.15%. <br /><br />Hydrofoils may be inexpensive to start with but build in cost the longer you use them.<br />Not to mention that you give up performance improvement in many other areas as well.

 

[BillP]

Re: Hydrofoils

Put foil use in real world terms. 10,000s are used and broken cavitation plates are few and far between. Most are broken because someone used the foil as a step. If we want to talk about breakage there are numbers of trim tabs that get broken from hitting objects while beaching or launching. (I really wonder why is this never mentioned with the anti foil crowd)<br /><br />Top speed loss...is due to the motor height letting the foil stay in the water at high speeds. Unless the boat needs the bow down at high speeds the foil should be above the water while while on a plane. This means raising the motor to achieve correct elevations...after all, we consumers don't want to use poor installation practices to benchmark other products by do we? If it's on an IO then you have to deal with it. <br /><br />Lets also point out that a correctly installed foil lets you trim up the motor and run faster (reduced fuel burn anyone?) and shallower. (and another I know this is an IO string)<br /><br />To each his own but somebody's gotta do it...I/O or not.

 

[LubeDude]

Re: Hydrofoils

Originally posted by BillP:<br /> <br /><br />Lets also point out that a correctly installed foil lets you trim up the motor and run faster To each his own but somebody's gotta do it...I/O or not.

How can something that is suppose to be out of the water at WOT allow you to trim out more and give more speed??? Unless pushing more water onto to prop in some instances. Ive had these fins on two different boats and they do work to a point, but now that I have the Smart Tabs, I wouldnt have a fin up my you know what.

 

[lakelivin]

Re: Hydrofoils

nautiJohn,<br /><br />As you say, usage will impact the effect on gas mileage. With mostly stop and start boating and low speeds (most of my boating is for pulling tubes or wakeboarders, 15-22 mph, depending) I could see possibility of increased gas mileage. Alot of cruising, the opposite. (comparing foil to non-foil only).<br /><br />If I have time next spring I may pull the foil off and take some measurements for comparison. I'll post back with results if I do it.

 

[Jdeagro]

Re: Hydrofoils

Bill P;<br /><br />I am not trying compare any poorly installed product to any other ( including ours) that is properly installed. And I will admit to being prejudice since we are the manufacturer of Smart Tabs, but let me make a few points<br /><br />In our instructions we identify the potential problems with both the improper adjsutment upon installation and the boats themselves. We also identify how to correct these problems. For example, if you install Smart Tabs with excessive actuator pressure the boat will run bow down and slower. We explain this and provide the information on how to adjust the tabs setting to eliminate the problem. It takes but a few minutes. No where in the instructions of any hydrofoil I have seen sold at retail does it say that the foil should run at or above water level, and raising the motor is recommended at part of the installation. This does add a bit to the installation of this product. As you have pointed out the I/O boat has no alternative but to take what he gets. <br /><br />You can increase the speed of an outboard boat by choosing the exact motor height with the foil so that you can trim the motor out without allowing the boat to porpois. This takes some experimenting, and a hoist if you are dealing with a larger motor.<br /><br />On a deep V boat or a Bass Boat with a running pad, the increased lift at the center of the boat will induce chine walking. <br /><br />As for the issue of breaking cavitation plates, I can not comment as we have no first hand experience. However, the added surface of the hydrofoil would likely add stress to the casting that it was not necessarily designed to accomodate. If the manufacturer thought this was a good idea they would make the accomodation or increase the size of the cavitation plate.

 

[tommays]

Re: Hydrofoils

i must be bad at math because in real world use the simple foil inproves my fuel use at the real world speeds i use the boat at but i only have 4 years of records without them and 5 with on the same boat<br /><br />the tabs seam to show no speed inprovement above 3000 rpm<br /><br />i can base my facts on 60 mile round trips up and down the lenth of lake george over a 9 year time frame<br /><br />tommays

 

[Jdeagro]

Re: Hydrofoils

Tommays;<br /><br />I tried to summarize the four page article, which is available on our web site under "product test" (www.NauticusInc.com). We did make the boat go faster by 2 mph and 100 RPMs. Top Speed was 49 MPH. <br /><br />I do not debate the technology of hydrofoils, it is valid. What I do not believe is that you can take an off the self hydrofoil, install it on any boat and achieve the results claimed. It is a rigid planing device that changes the hull design. If your lucky, and apparently you have been, then you will get some good results, and not cause other deficiencies.

 

[tommays]

Re: Hydrofoils

there is no question that any of the systems will inprove low speed performance <br /><br />it would seam inpossable for any device that is contacting the water and makeing some level of drag to increase top speed on a boat<br /><br />i have not driven any small boats that requires tabs or foils at WOT speeds the trim in the drive will balance a correctly built and loaded boat at these speeds and the 0% inprovement listed seams to bear this out<br /><br />tommays

 

[Jdeagro]

Re: Hydrofoils

Tommays;<br /><br />Read the article! Most people can not believe it either, - until they experience it! <br /><br />Have a great Christmas and Happy New year

 

[phaeton]

Re: Hydrofoils

tommays - I agree with your logic but clearly they are not only adding drag; in some way they are improving the efficiency of the hull/drivetrain on this paticular combination. Given the variables this doesn't surprise me!<br />Interestingly most people gold achive a similar gain by simply moving the load in their craft to it's optimum position for any given hull speed too - but I find teling the guys to move away from teh fridge to improve gas milage doesn't go down to well!

 

[Richard Petersen]

Re: Hydrofoils

Phaeton's statement of shifting passengers,is the only intelligent statement on this page!! Do that, relocate people for balance, FIRST. Wide rear seat area, oversized engine, gear stored under and around rear bench, chicks laying on the rear deck. Hmmm, why do I need TABS or FOILS? Once you trim the tabs below LEVEL, you are really driving the boat with dragging BRAKES!!

 

[Jdeagro]

Re: Hydrofoils

Richard;<br /><br />Sorry but you misunderstand the Smart Tabs system they are active like the suspension system on your car. They help compensate for load imbalance and other handling issues. They are not the same as helm controled trim tabs.

 

[BillP]

Re: Hydrofoils

Originally posted by LubeDude:<br />

Originally posted by BillP:<br /> <br /><br />Lets also point out that a correctly installed foil lets you trim up the motor and run faster To each his own but somebody's gotta do it...I/O or not.

How can something that is suppose to be out of the water at WOT allow you to trim out more and give more speed??? Unless pushing more water onto to prop in some instances. Ive had these fins on two different boats and they do work to a point, but now that I have the Smart Tabs, I wouldnt have a fin up my you know what.

Hehehe, so that's where your old foils are, now I understand the problem. <br /><br />Guess what, you will feel the same about cockpit controlled tabs if you try them...do you think there's enough room for a couple of tabs with the fins? My palm reader said you are almost ready for the next level...teeheehee<br /><br />About trimming higher...the foil captures/contains water being slung off the prop and lets the prop ride higher before venting. It acts just like the stock cavitation plate but at higher trim. Next time you come to Florida I will show you performance with and without a foil on the same rig. I will show you cockpit controlled tabs too.<br /><br />OH, OH, the HORROR of it all...foils n tabs.<br /><br />Peace.

 

[Richard Petersen]

Re: Hydrofoils

Nauticus Inc.. As I see it, after I install and trim it for just me and a 1/4 tank full it will automaticly give the same pop up when 5 more people come on board and a full tank. I don't see how it can give the same effect for 5 without increasing the plate area. Unless I always balance the load. If I balance the load, I should not need any trims. Balanced is best? Am I making sense?

 

[John_S]

Re: Hydrofoils

Richard, You need to go read on how these tabs work and read the magazine test reports. Your wife's boat sounds like it is probably stern heavy (V8 in light bowrider). After reading the articles you might find it worth trying. You will also find many buyer testimonials on this board. And they have a money back gurrantee if you are not happy.

 

[Jdeagro]

Re: Hydrofoils

Richard; <br /><br />That is like saying your car will perform the same with five passenger as it does with one. If you down load (from our web site www.NauticusINc.com )and read the booklet that we published to help people understand how balance and performance effect the overall handling, you will see that we do not disagree on the issue. <br /><br />Obviously the larger and heavier the boat the larger the trim tabs should be, but you don't change tires, shocks and springs on you car every time you add more passengers, and neither do you need to change the tabs.<br /><br />There is not much I can do to convince some people that there may be a new widget that actually works, especially when they are so satisfied with what they have. To some people "the devil you know is better than the devil you don't". <br /><br />I love my Dad and he loves his black and white TV, so I let it be.<br /><br />I hope we all appreciate the country we live in, one that allows us to debate such trivial things like who's widget is better. God Bless those who defend our life style, let's pray them. And pray that those who have less will someday enjoy similar luxuries. Merry Christmas to all, and our sincere wishes for Peace in the coming year.

 

[Richard Petersen]

Re: Hydrofoils

JOHN & JOHN I am spinning my wheels on this. I will wait until next spring when we all re-group at the river. Ask lots of our boaters and dealers for rides and opinions. Been away from boats to long to know whats right today to help boaters. Thanks for using kid gloves on me. Rich --I would rather put 3 60# bags of sand under the bow seats then flaps on the pipes or or plates on the stern. If the bags don't work. You get me. Best I can do.

 

[Richard Petersen]

Re: Hydrofoils

These forums are great. Went to Web design, one guy described my boats habits better than I remembered. There are some very sharp people floating around.

 

[Ralph 123]

Re: Hydrofoils

You are never going to get a definitive answer on this topic except this: Try it. Start simple and cheap and work your way to the most expensive solutions. For $40 (or less) and 5 minutes of work, put a foil on and see how it works. If it doesn't and you have a smaller boat, try smart tabs. If you have a larger boat, go buy Bennett tabs... simple. If you're worried about mounting, get Doel Fins which is two independent fins that allow you to adjust the mounting location.<br /><br />No solution works in all cases. Your only decision is which one you try first.