Hydrofoil Question.

[ProCraft17]

I have a 17.5 foot procraft. Im debating puting a hyrdrofoil try and get a little more of the boat out the water when on plane. Ive heard from some people that having a hydrofoil can cause a boat to flip when turning....What do they mean by this ?? and If not, what are some things NOT to do with a hydrofoil for safety or performance reasons.

 

[ziggy]

Re: Hydrofoil Question.

debating puting a hyrdrofoil try and get a little more of the boat out the water when on plane

a hydrofoil won't do that for ya. it will help ya get on plane, but when running, it'll keep more of the boat in the water due to the water pushing on the underside of the foil.

Ive heard from some people that having a hydrofoil can cause a boat to flip when turning

i've not heard of flipping, but i've sure heard of unstable conditions.

If not, what are some things NOT to do with a hydrofoil for safety or performance reasons.

not really safety or performance, but don't run in debrit ridden lakes or rivers. i had one on my last boat. i hit something on the river and it broke the hydrofoil off, along with some of the anti cavitation plate of the drive.

if i was having trouble planing, or porpoising. i'd be looking into trim tabs or smart tabs.

imho, nothing is gonna get more of the boat out of the water short of trimming up/out. to the point of porpoise or blow out (ventilation or cavitation).

 

[ProCraft17]

Re: Hydrofoil Question.

Thanks Ziggy... So would it be a good idea to have one and install it when im skiing/tubing and maybe take it off when im fishing because i fish in the basin in south louisiana...Very unforgivable terain and i dont want to get stuck at any fishing holes..

 

[ziggy]

Re: Hydrofoil Question.

So would it be a good idea to have one and install it when im skiing/tubing and maybe take it off when im fishing because i fish in the basin in south louisiana..

a foil will give you a quicker time to plane, lower bow rise when going from plow to plane. basicly, it is always trying to push the bow down and the stern up. what i don't like about them is where it's pushing on. all the push is coming from whatever is driveing you boat. be o/b or i/o. imho, it's putting undue stress on transom for both i/o and o/b and on the i/o it's further stressing pivot points that are less duty than if it were solid like an o/b. this along with the breaking off of drive parts is why i don't thing they are a good idea...

trim tabs, be it smart or real. they also push the bow down, but they do it from the transom and are pushing up from the bottom of the boat at a strong point. the transom. real tabs are infinitely adj., controlled by you. smart tabs are always pushing down but automatically retract as you get up on plane and start going faster and faster. some smart tabs can be retracted for no (less) effect also, real tabs can be drawn full up for no (less) effect also.

edit. i think the poor handling of a hydrofoil comes from the fact that the foil tilts with the boat as it leans into a turn, more of one side or the other of the foil is deep in the water, the other side in lack of water. always pushing the bow down too. it makes sense to me that this may cause poor handling in some cases..

 

[smallboatlover]

Re: Hydrofoil Question.

i find that my hydrofoil on the my boat works great it takes little to no power to get onto a plane. now is that just because of my setup. i know that trim tabs wouldn't be any help for me on a 14' boat so do you think on a boat like mine the hydrofoil is a good idea?

 

[JB]

Re: Hydrofoil Question.

A hydrofoil changes the hydrodynamic characteristics of a boat, essentially creating a false bottom extension and moving the center of moment aft when getting on plane and when planing.

When correctly rigged and trimmed this allows quicker planing and holding plane at lower speeds.

The extra forces the foil takes are on the antiventilation plate, not on the hull. Though rarely a problem, the AV plate is not designed for that added force and may fail.

If incorrectly rigged and/or trimmed a foil can produce erratic and dangerous handling, particularly in rough water. I know of one case in which a foil was mounted on a long shaft outboard mounted to a short transom. The operator trimmed the outboard way out, trying to get the foil to the top of the wake. The foil dug in and flipped the light boat by running the stern under the bow.

I have used foils on several of my boats (all Boston Whaler 13s, 15s or 17s), never had a problem and always got on plane quicker and at lower speed without any loss of WOT speed.

You must rerig your boat when you mount one. Just bolting it on and going boating is an invitation to disaster.

 

[Handyman1]

Re: Hydrofoil Question.

14' fiberglass it is like a brick on the water! the hydrofoil will help! in some cases you might feel the boat a little tipsy going from side to side at wot just slow down a bit that will corrected + you can always take it of if you don't like it $50 out the window

 

[ProCraft17]

Re: Hydrofoil Question.

What do you mean by reriging my boat?

 

[JB]

Re: Hydrofoil Question.

What do you mean by reriging my boat?

Optimum outboard height changes when a foil is installed. In some cases, so does best prop.

Most of the time what happens is that the boat was not fine tuned before installation and the foil performs badly.

 

[dockwrecker]

Re: Hydrofoil Question.

Don't bother screwing around with a hydrofoil. Tabs have more surface area, apply lift forces to the structure of the boat (where they BELONG) and provide more stability. It's a simple fact of leverage that the tabs will provide better performance being spaced wider across the transom than some fin bolted to the drive. Tabs will control the boat far better and let the drive function as designed.

 

[Capt'n Chris]

Re: Hydrofoil Question.

A correct prop is all you need and the least understood.

 

[roscoe]

Re: Hydrofoil Question.

You are leaving out some of the most basic and important of information, that must be considered before you make a decision.

Type of hull
weight of hull and usual running weight
Hp rating of hull
hp motor being used
mounting height of outboard, where is the anti-ventilation plate in relation to the bottom of the hull

If it is decided to purchase a foil, the outboard must be mounted so that the foil is out of the water when the boat is on plane.

It may help you get on plane quicker, but not if you are underpowered or motor is too low.