Doelfin Hydrofoil - Page 2

Manos · 25 March 2003, 17:39

NO NO NO

It was because they advertise that it can fit quote 'ANY ENGINE TYPE' I thought about the drag but never crossed my mind ripping off the cav plate. Interesting!!
Any way as I said will do without this one this time

Cheers

crazyhorse · 25 March 2003, 17:42

Yep dead right my feelings exactly.

Richard · 25 March 2003, 18:34

I'd like to add a cautionary note about the use of Doel Fins. I use a 4m Avon Searider with a Mariner 40HP 2 stroke when teaching sailing to a local Scout group. When we got the new engine last year I took the boat out for a "test drive" starting slow and building up until I was doing everything I could think of to get the boat to misbehave. The boat was perfectly composed throughout. Later on last year against my advice Doel fin was fitted. I have allways thought that this makes the boat plane to high and too early casuing the boat to feel as if it is riding high in the water and is unstable.
A few weeks ago I was driving the boat in a force 3 wind with a following sea of around 1 ft with the throttle at half way and the boat just comming onto the plane. In the middle of a shallow turn the boat was caught by a wave and rolled over.
I am convinced the fin is to blame. I have since had emails fron several people saying that fins cause instability in following seas and just below planing speeds. If someone would like to give another explanation for the incident then I would like to hear it.
I don't think the fins are necessarily a bad idea I just think they arn't a good idea for every boat. If your boat has problems then try them but if your boat works then I think they cause problems.

matiboy · 25 March 2003, 18:57

Quote:

Originally posted by Richard

A few weeks ago I was driving the boat in a force 3 wind with a following sea of around 1 ft with the throttle at half way and the boat just comming onto the plane. In the middle of a shallow turn the boat was caught by a wave and rolled over.

Thats a bit concerning in 1 ft of following sea that a rib can just roll over ?

However if you didnt have a doelfin fitted , what attitude would the boat have just off the plane as you are trying to make a slow passage downwave

Nose high , stern dug in , difficult to steer and the transom now very low ready to be swamped by a following sea

The fact that you could just get onto the plane at a lower speed with the doelfin wouldnt that be an advantage , as the boats attitude would have levelled , making the boat generally more controlled.

Also the fact that you are planning means that you can accelerate from trouble, try doing that when youve got to get planning first

wavelength · 25 March 2003, 19:11

ok the maker's claims ar quicker onto the plane etc etc-but from my experience and obviously others who have used them, worth having with some but NOT with every boat. Could explain the original comment as to why the o/b manufacturers don't offer the option eh.

matiboy · 25 March 2003, 19:37

Quote:

Originally posted by wavelength
ok the maker's claims ar quicker onto the plane etc etc...

As well as quicker onto the plane , which is great for obvious reasons , they also allow you to throttle back and remain on the plane at very low speeds, than if you didnt have one fitted

This must also be fuel efficient, as using lower revs and still planning

DJL · 25 March 2003, 20:19

A little side note. Make sure that when you trail the boat the Doelfins are covered by the orange bag.

The police were stopping everyone leaving Baiter Slip, Poole a few years ago and apparently they claim people might not see them and get too close.

jwalker · 25 March 2003, 20:44

1) How can a piece of ABS plastic rip off your aluminium alloy anti-ventilation plate? Have you no sense for material strength?

2) It's an anti-ventilation plate not a cavitation plate. I attempts to prevent air being drawn down into the prop area. Cavitation is entirely different. And, anyway, you'd probably want an anti-cavitation plate, wouldn't you? If there was such a thing.

3) It's likely that the foils will help to improve the anti-ventilation effect.

4) I've had foils fitted to my 200hp, on my 6.5mtr rib, for years, without problem. Max speed is very slighly higher with the foils.

5) Because they are foils, they can also work upside down. Not very efficiently I grant you, but they will work. Therefore, if you trim a long way out, they can pull down on the stern and help to lift the bow.

6) Since they are one size, it may be the case that they are too large for some boats. Having said that, I had them on a 5mtr SIB for a couple years and they were fine.

JW.

Daniel · 25 March 2003, 21:03

Got em on my 130, no idea what the boat would be like without because they have always been there. She does plane at very slow speeds though, quite useful on rivers and stuff.

wavelength · 25 March 2003, 21:45

Quote:

they also allow you to throttle back and remain on the plane at very low speeds, than if you didnt have one fitted

allegedly-but don't believe everything in sales literature. I know that is not true on every boat - as my previous post.

Cookee · 26 March 2003, 08:12

jwalker - I think Manos may have got it the wrong way round - he was replying to me where I said that it may get ripped off the cavitation plate.

I always thought they were the same thing - but the result is the same anyway!

my experience of these devices is admittedly a little old, and they certainly (to my knowledge) didn't do them for "bigger" engines then! Impressed they give you more top speed on your boat - do you get other benefits as well, such as earlier and slower planing speeds?

matiboy · 26 March 2003, 10:46

Quote:

Originally posted by wavelength

allegedly-but don't believe everything in sales literature. I know that is not true on every boat - as my previous post.

Not read in a sales leaflet - a simple fact from experience of fitting one

When throttling back you can keep it just on the plane at very slow speeds, which is usefull approaching inlets when you need to think about slowing down

Ribald · 27 March 2003, 08:10

Are we talking about the flat fin or the gull-wing shape fin here?

Keith Hart · 01 April 2003, 05:10

I've just noticed that Pepper seems to have a doelfin fitted to his 18hp on his 3.6 SIB (see the for sale section).

Pepper - how do you find it affects the boat and it's performance? Would YOU recommend fitting one to a smaller boat?

I presume that it could be removed if it did not work.

Keith (vested interest) Hart