Another hydrofoil question>

[Rhys_Mav]

107526
i recently bought a new boat it a 455 sea jay side console with a f60 yammie on the back. The f60 is the max hp for the boat but the previous owner has fitted a hydrofoil. My understanding after some research is the i shouldn't need the foil if the motor is set up right. I was thinking about removing it but just wanted some opinions on weather i should or not as I'm new to this stuff.

Thanks Rhys

[scottar]

Won't hurt to take it off and try it but I suspect it is there for a couple of reasons that ultimately go hand in hand. Due to the weight of the modern day 4 stroke, extra boat speed is required to get the boat to climb out of the hole and onto the plane as well as to stay on the plane. In dead flat calm conditions, this is not an issue but in choppy conditions it can make for an uncomfortable and if bad enough, damaging/dangerous ride. I ran a foil on a similar size hull with only the weight of a 40hp two stroke for a lot of years that was fairly heavily used offshore. It could get on the plane down to a speed of 8-9 knots quite comfortably in conditions that without the foil, turned the boat into an absolute pig due the extra boat speed required or burned a stack of extra fuel because I wasn't properly on the plane and was pushing water.

[Harmytage]

Scottar has got it right in my opinion, I have a 4.1m tinnie with a 40hp yammie four stroke on the boat and I have a foil on the back of the boat due to the extra weight of the motor.
Its not so much for hole shot lift but the fact that it helps it to plane at lower speed which is especially helpful in places like moreton bay where the choppy conditions can make for an unpleasant ride home if you have plane at a higher speed or the other option is to drop off the plane and cruise home at 6knts. Some people are against them but I for one have had a foil on the back of my last 3 outboards.

[Dan5]

I've found that with the Sea Jay's in particular that they don't seem to have enough transom angle.....a mate has the 455 territory with the Suzuki 60 and even with the leg trimmed all the way down it was still porposing like
hell.........we fitted 5deg transom wedges to it and it made a lot of difference........we also ended up fitting a Permatrim in the end as well to make it just that bit better with the slow planning in rough conditions.............We were going to experiment with it by cutting back a little of the Permatrim in 50mm increments to try and get it "perfect".......we still have not done the chop but I would like to try it but he is happy enough with it now to not want to touch it.......

Dan

[chocolatemoose]

oh man i get scared when i see hydrofoils on outboards :(

[stockhorse]

Can you expand on that moose?

[Luc]

Had a permatrim on my yamy 25/4 and never had probs.

[scottar]

I assume Moose refers to reports of or has experienced handling traits that have either been created by a foil or highlighted by addition of a foil that are at best unfriendly - at worst downright dangerous. The most common reports are being in a following sea and the wave effectively picking the boat up by the foil and making it broach or boats that will just dive off unexpectedly while travelling along in flat seas.

While there is enough complaints to say there is obviously some truth to them, personally I have never had a vessel do anything untoward due the addition of a foil (ranging from 3.5m tinnies through to 6m glass rigs with a variety of different foils) provided that the trim position was adjusted correctly. Foils will generate a massive amount of lift with the motor trimmed right in. As your boat speed increases, the amount of lift increases as well to the point that the bow can be forced down sufficiently to make the boat difficult to steer and in the wrong conditions dangerous.

As I see it though, on some boats these handling traits can be induced without a foil - if you don't trim the motor correctly relative to boat speed or conditions. Certainly on boats without trim and tilt, a foil can mean that you will need to move the trim pin a bit to find the best compromise dependant on loading and sea conditions and the required boat speeds. I regularly move my pin mid trip on my tinnie to allow for requiring more lift to keep the bow down at lower speeds and then move it if conditions will allow for higher boat speeds. The pin position will also vary dependant on load distribution. By not making the above adjustments, I can certainly see how the boat could be driven to the point of being dangerous.

In your case however, I assume you have electric/hydraulic trim and tilt - this takes all the hard work out of the adjustment side of things. Nothing really changes as far as best practice is concerned when running with the foil but you will notice that trim adjustments will have a greater effect with it on than off.

[robothefisho]

Have fitted permatrims to three of my boats, and they have always improved the performance. Trimming right in will generate a lot more bow down attitude so if you got someone who set trim off a guage number only maybe this could cause dramas for them. I've never experienced any dangerous handling traits with them fitted to boats from tinnies to boats that do 50 knots.

[Seahorse]

I just put a sports 300 on my 50 yammy 4 stroke, which is on the quinny 420 renagade.

before at around 5 knts the nose is right up in air, now sits fairly level.

jumps put lot quicker. No speed loss. Works really well. Happy here.

[aussiebasser]

I've never heard a bad report of an SESport foil. Stingray foils can cause real problems. I'd say it was put on there for a reason. Whip it off and give it a run, but be prepared to put it back on.

[scottar]

I've never heard a bad report of an SESport foil. Stingray foils can cause real problems. I'd say it was put on there for a reason. Whip it off and give it a run, but be prepared to put it back on.

It's a funny one. I ran Stingrays on a Victory 5.9 with a 150 Johno without issue, On my Savage Gull with a 40 Rude ( Started with a Junior size and then upgraded to a full size one) and also a 4.5 Quinnie with a 40 with no dramas. I tried the SE Sport on my Victory 6.0 with a 200 E-Tec and while it had no bad habits, the drag was enough to drop sufficient RPM that a re-prop would have been required - even with the motor mounted as high as possible short of getting a jacking plate. I ended up with a Permatrim which still creates drag but nowhere near as much. Have also spent time in a Haines 17C with a Hydro-Tail one piece plastic foil. All of these products have achieved the desired results of stern lift and thus lower plane speeds.

When it came time to put one on my current tinnie, I decided to give the Solas Laser Foil a go. It's made from stainless and has a very thin cross section compared to the plastic jobs. The thought process was less cross sectional area = less drag. Main reason for this is the keel on the tinnie prevents getting the AV plate above water while on the plane - the prop starts to ventilate due to the water disturbance. The foil was a bit sharp round the edges as it came but nothing a rub with some wet and dry and a buff couldn't fix. Seems to work ok.

Not sure why some guy's have issues. I could understand problems with some of the older glass runabouts that have very fine entries without a lot of buoyancy forward. Maybe if the motor wasn't mounted perfectly straight it would cause issues???? Other than that I could only put it down to incorrect trimming.

[aussiebasser]

The Stingray has a pronounced downturn at the rear, almost forcing the nose down too much. My brothers SavaGe Jabiru was almost undrivable with it. We cut 3" off the back and it was fine. Early on I saw a honda that had the cav plate broken because of the force of the Stingray and a poorly set up motor. I found either the Permatrim or SESport worked on my Hornet.