Anyone running a hydrofoil on a stepped hull?
 

Wondering how much a hydrofoil will effect the ride of a stepped hull, my Larson Senza Spectre easily rolls while riding and is very squirrley at lower speeds. I think a hydrofoil will improve all of this. Anyone have this setup?

long tabs are the trick setup 380s really help smaller boats with stability

Well, if the issue is at lower speeds, the easy solution is to not go slow!

+1. There are many go-fast boat's that don't do well at slower speeds. Never seen a hydrofoil on a go-fast and wouldn't think it make any sense financially on a low-cost boat like that. Sounds like you need a different boat.

Sure you hsve :) Max machine cavitation plates :)


https://cimg2.ibsrv.net/gimg/www.off...6fbfb651f.jpeg

That’s on a stepped hull?

That boat new, was like 45k…. It makes sense to me, especially since how it works and how stepped hills work.

Trim Tabs are a better bet on a "performance" hull. Putting a hydrofoil on your outdrive will help it get on plane quicker and maybe maintain plane at a slower speed, but that's about it. It will create DRAG and slow you down compared to not having one.

When you say squirrely at slow speeds, is that off-plane or on-plane? If it's off-plane, that is bow steer which is normal for V hulls. Just don't over correct with the wheel to try to steer it straight that just exaggerates the wander.

Was just replying to what I quoted. Nothing else.

I don’t know why your boat rolls nor the fix. Sorry.

I’ve driven conventional v-hull boats before and they’re not like that. It wanders like crazy at slow speeds, like I would think people would assume I’m totally smashed. I’ve considered trim tabs but that would do nothing for me on plane, since they wouldn’t even be in the water. I would plane faster with a hydrofoil, it still probably will be squirrely at low speeds but not for as long, once on plane.

Good thinking. Maybe that’s why it rolls too. Too much trim down at speed…ie: bow steer.

Was testing someone’s boat this fall and it bow steered so much at 20mph with trim down my right shoulder almost hit the water. Holy fuk i thought i was going out of boat. Never witnessed that before. Little 18ft boat with colvo duoprop.

The roll is an issue at higher speeds, it’s a 25’ boat. I don’t enjoy going down a lake on my side doing 60mph+

Is the outdrive solid at the pivot points?
I have had a couple worn out that allowed "sloppy" steering.
Have the small skeg above the prop?
Have seen those and adjusting those make a little difference, but would not expect too much at all.

Does it have power steering, if so is it bled properly, air in system will cause it to walk at slow speeds

Bow steering is off-plane If the boat is leaning that much at speed, then it has to be a load issue. See if you can move some weight to the non--leaning side. If the boat seems balanced weight-wise maybe you have something else going on. Maybe you have water in the hull on the leaning side?

If all else checks out, trim tabs might be the only way to solve this. They help with getting on plane, low planning speeds, correct for side to side imbalances etc.

Trim tabs work all the time, unless you bring them up all the way and out of the water.

Gimbal Ring

Yeah probably bad advice. I thought you were talking about a real hydrofoil not a pretend foil "whale tale." Many have used on older cigarette hull's with great results in reducing porpoise, but that does not sound like the problem you were trying to fix.

Well a stepped hull doesn’t make balancing any easier. It doesn’t have anything to do with the steering. I’ve even moved my battery to my side to help, which it does but doesn’t fix the problem. Trim tabs won’t help after the boats already planed and it doesn’t take much to plane the boat.

Just laying out some history:
https://www.offshoreonly.com/forums/...y-speed-4.html

Where did I mention a hydrofoil in that??

Trim tabs are absolutely part of the equation when on plane. They should be installed parallel to the bottom of the boat and effectively lengthen the hull length. While under way you can further lower them to help lift bow of the boat. Drop one side to effectively compensate for a listing condition in head and following seas.. The only time they have no effect is if you run them full "up" and they make no contact with the water, this can help with top speed.

For your reading pleasure:

https://www.boatsafe.com/trim-tabs-explanation/

The 'bow walk' at slow speeds is common, the 'trick' is to NOT touch the steering wheel and let the boat do its thing...yes, it will hunt from starboard to port and back again but it WILL essentially run in a straight line.

The cavitation plate mounted hydrofoils like 'Stingray' and others make will only exacerbate handling issues. Years ago a buddy of mine put one on his Mariah, and damned near killed his entire family when the boat heeled over HARD at speed and tossed everyone out.

You didn't, but you did say this in that thread. And here you are.
Saying trim tabs aren't effective once on plane. :bong:

Well Cheech, I’d put the bong down because it’s effecting your reading skills 😂. How do you move your outdrive up and down? 🤔😂

And this is for your reading pleasure lol:

https://www.seabornboats.com/what-is-a-stepped-hull/

Mariah’s make a stepped hull?

Need more detailed information, is this a new issue, what speed does it occur (on a plane or not), what trim position is the drive when it occurs, at what speed and trim position does it go away?

https://www.powerboatlistings.com/view/49850#

Here's a link to a 1990 Senza. Looks like an aggressive step for a 1990 25 foot powerboat. Maybe that's just a handling characteristic of this particular hull. I'd be careful throwing money at it without talking to someone who successfully fixed the issue on the same boat.

Ahhh, stupid me thought he was talking about a real hydrofoil, not a "whale tale." Sure, I've seen them used successfully in older cigarette straight bottom hulls supposed to help the porpoise quite a bit by providing a bit more lift, but that does not sound like the kind of problems the OP is having.

Slight sidetrack but good info for anyone owning these boats. See post #
13 and #14. Have original boat testing article.
https://www.offshoreonly.com/forums/...estions-2.html

Oh OK. :bong:

Trim down for what? :grinser010:

haha yeah, not that kinda hydrofoil. That’s the problem, most people are familiar with just a v-hull, the stepped hulls are much different and most people have zero familiarity with them. And I think the stepped hull is more successful with larger boats, a 25’ boat I think is pushing it. My thought is that the front of the boat will have the most stability since that’s where it’s mainly ridding on, the outdrive is a sort pivot point for the boat. Trim tabs make no sense for what I’m trying to do and I’ve talked to other senza spectre owners about trim tabs. I just didn’t feel like getting into this conversation since I already did the research and I’m not trying to diagnose this problem, I just wanted to know if any stepped hull owners saw or thought a hydrofoil on the outdrive would help. The hydrofoil is kinda like a trim tab anyways but there’s no where to put the trim tabs that would benefit the boat, the step glides on an air pocket, the trim tabs would be literally in the air.

Yikes

Same problem on my Seafari 25. The brain trust doesn’t think the hydrofoil will do enough on the Seafari 25’ that’s a variable deadrise hull. Trim tabs have same issues as you noted above. One guy I know pulled a mold off hull to modify the tabs. I’m planning to install Volvo penta trim tab system that lowers a bar straight down from the transom to adjust ride. I’m toying with making an aluminum mounting plate with slots so I could raise and lower it to fine tune the final mounting point but I’m not sure it’s worth the effort.

For the cost of one, it's worth a try. Beyond that maybe a different style of prop, with less stern lift?

By “hydrofoil” I assume you’re referring to the fins that mount on the drives cavitation plate? What prop are you running now and how deep is the center or the propshaft below the bottom of the boat? If setup properly trimming up should alleviate the bow steering issue you’re describing, unless the prop is not deep enough, or contributing to the issue and lifting the stern because of wrong prop.

I had a step hull 22 DONZI with a 3 blade on it. Can not remember the make or pitch.

I ran one of those hydrofoils that bolt to the cav plate and it did help it get on plane faster. Didn't seem to affect the high speed handling of that hull.

As for TABS not helping because its a short step hull, that makes no sense at all unless you are mounting them ski high on the transom. Post a picture of your transom straight on from the back. What exactly is the boat doing?

If the boat is new, before you start trying things, does the dealer or manufacturer have any advice?

Props can make a huge difference..... On my boat, I was running a 23 mirage, I tried a cleaver and I though I was going to die it was so squirrely. With the mirage it was always predictable and very forgiving.

doubled the hp, raised the drive 2.5" and went to a 4 blade, it runs very flat and stable, if I try to trim it upit starts getting squirrley. I have a different 4 blade to try this summer with the bell cut off to decrease stern lift.

Too much stern lift can be a problem.....

If you guys don’t have or have never had a stepped hull, I’d appreciate it if you just let the guys with stepped hulls talk.
https://cimg0.ibsrv.net/gimg/www.off...7d226752a.jpeg
Not mine but it’s the same hull, rides on a pocket of air… do you see why I’ve said that trim tabs won’t work besides the fact that I talked to owners that said they didn’t help