Add On wings for Outboards

Do these hydrofoil like attachments that attach near the anti cavitaion plate actually do what they claim? if yes, why are they not fitted as standard?

[Tom Lathrop]

First, they are anti ventilation plates, not anti cavitation. Commonly wrongly named. They help prevent air from being entrained into the propeller from the surface. Cavitation is another matter altogether and only ocours on high speed heavily loaded propellers.

If a boat is properly designed and the engine is correctly installed, there is no need for them.

They can also help get a boat onto plane and/or help prevent porpoising if it needs that.

If a boat is well designed and set up, they will probably just slow it down a bit.

I have a 33 foot center console with twin 200 outboards and thought I'd get benefits from the "dolfin" type wings but found the follwoing:

1) longer and heavier boats barely notice they are there
2) when on plane, my deep Vee rides pretty high - the "wings are literally out of the water so dont slow me down
3) I could change the attitude of the boat when on plane better
4) she seemed to plane at a slightly slower speed (3knots)

Bad news is the type I purchased needed stainless screws/holes in the cavity plate and when I cruised into some shallows (sand bar) while heading into Boca inlet, I broke one off. It took a chnk out of the cavity plate so I had to get some repairs done...dohhhh

On smaller boats- I think the plates are great. Try to get the ones that do not require weakening the cavity plate with holes.

[Willallison]

I would have to agree with Tom here - in general, a well designed boat shouldn't require the addition of 'foils'.
However, if a vessel is somewhat marginal in the power stakes - as was my 27ft Searay Sundancer - or is a little fat in the weight department - as was my 27ft Sundancer! - then it can make a difference. I installed wings to the cav plate (I know Tom) of my Bravo 2 leg and saw simialr improvements to Guest - an ability to plane at a slower speed, faster onto plane and interestingly better dynamic stability (though the boat still tended to bow steer in a following sea).
An o/b ski boat that I used to drive in tournaments was absolutely transformed by the addition of foils. It went from an absolute pig to being a pleasure to drive. Conversely another ski boat I drove was changed from a well manered boat into a bit of a dog.
In other words - if your boat goes well now - probably best to leave it be - if not, try the foils.....

[Tom Lathrop]

Of course you are correct Will. The foils can transform the performance of some boats. Those will be boats that were marginal in power or performance. They will also improve turning ability in some boats by preventing over-reving from ventilation in turns. I think they are best on deep V's where they can lift a heavy or underpowered stern onto plane.

I was mainly trying to say that they will not improve performance of a good boat although the marketers say they will always do so. I think they get away with the claim because there are not too many boat/engine combinations that are optimized.

Guest, I'm not sure I understand how you can run well with the plates/wings out of the water. That could be the recipe for a blown engine unlessyou are careful.

Thanks for the replies! My actual problem is that I get prop ventilation in turns and that I am finding it near impossible to trim the boat with a good planing performance. I have a 14ft Zodiac Rib (Pro 420) with a 2cylinder Mariner (aka Yamaha) 30.

The ventilation problem is my fault as I raised the engine 2inches as I could not get on a plane at all - I'm now going to put it back but this will put the anti-"ventilation" plates 2 inches below the hull bottom. I'm just hoping that the rather coarse trim adjustment on the motor will be OK at max position.

I wish I had power trim and more power!

The other issue is finding consistent smooth water for the trials!

Hi
I have one on my G3 115 merc, 1978, it works great it lifts the back up and improves my hole shot by 2 seconds, stops the boat from porposing and reduced the cavation in turns, for the price i WOULD RECOMMEND IT

STAN

[Tom Lathrop]

As the boat makes a turn, the stern actually goes sideways. If there is a keel or deep V in front on the prop, it will This suck in air from the transom and if the "anti-cavitation " plate is too high, the prop will be ventilated and the engine will over rev. If you can't get rid of the problem with the boat, you need to lower the engine. If it won't plane then, you need more power.

[yipster]

bought one once for my volvo penta runaround sterndrive but never bolted it on. my marine guy said it could break lose damaging the ventilation plate (thanks Tom for setting that rite once again). on outboards its liable to tilt the whole engine up and more comments against it, still i think the claims are valid...

[gonzo]

What we always tell our customers, is that if it was such a performance improvement the manufacturers would build lower units with giant cavitation plates. However, they don't. Manufacturers spend millions of dollars every year in R&D. The problem is with bad hull design and improper installations. I agree that it is possible to have more lift with an add on foil. It also has more drag. Trim tabs are a better way to fix a design problem. Also, they don't break lower units like foils often do.

[yipster]

...
i quickly typed "trimtabs" in the search button and got no result. so here pics of the ad on wing and a trimtab, i like the trimtab, not the wing in this form but the trimtab claims i dont really belive eighter (or it must be the extra ft lwl).

trimtabs are -for what i know- for pitch/nose down behavior and maybe even more for sidewind heeling correction. not intended for bad design coorection or have benefits named here with -bigger- engine(s) trimmable doing the same job better. wanted meters -they do exist- for the tabs but first time out everything went intuitive and very well and wont be without trimtabs, but come to think of it side wind heeling correction is what they do best and even that must be trimable in a dual system. multiple -counter- trims only adds -a lot of- drag.

i'm confused, like to hear you explain the -sort of double i think- trim systems a little better...

yipster

[gonzo]

Many boat owner find that they can get a better "hole shot" with either trim tabs or a doelphin. The trim tabs are better because they are independent from the shaft angle. Trim tabs can correct some problems caused by bad design. For example, porpoising, squatting and listing. The cavitation plates designed by the manufacturers do their job well. An outboard or outdrive installed to high cavitates because air (mainly bubbles) enter under the cavitation plate. A wider plate won't fix that problem. They do improve cavitation in tight turns. It would be better if the boat operator trimmed the drive in during the turn. I find that the factory settings give the best overall performance.

[Willallison]

I would agree with you to a point Gonzo. The additon of tab angle theoretically has the same effect as adding foils to the cav plate - greater lift at the transom. However, in practice, adding more tab also tends to drive the bow lower, whereas the foil doesn't seem to do this. My own experience with foils is limited to the examples I listed in an earlier post, but in the case of my 27ft Sundancer (equipped with both foil and tabs) I saw a a substantial improvement - particularly in slow planing ability. True, you can add more tab angle, but this tends to 'bog the boat down'. Then of course you have trim angle to throw into the equation as well.....

[gonzo]

It definitely helps the low speed planing capabilities. However, you pay with the top end. My biggest concern is with all the broken lower units I've seen.

[Willallison]

Yes, I was warned about that. Thankfully no such disasters befell me. And as a cruiser, I wasn't too concerned about top speed loss - in fact I don't think I ever even checked to see if the boat was slower!