Hydrofoils... do they work?

Back when I had my 18' Marada, it made a huge difference in time to plane and stability at plane.

I took it off for one day, noticed a dramatic decrease in performance, and put it back on.
 
Why?

Do you have handling problems? Do you need more sturnlift? If so add or bigger trimtabs.
These hydrofoils are really not mend for your style and size boat and besides that they create all kinds of drag.

Cor
 
Made a huge difference getting my 18 footer with a 3.0L 4 banger up on plane rather quickly.
 
quote:
Originally posted by sabrejocky

Why?

Do you have handling problems? Do you need more sturnlift? If so add or bigger trimtabs.
These hydrofoils are really not mend for your style and size boat and besides that they create all kinds of drag.

Cor

Click to expand...


+1.

I also have to ask if your props are getting you to the engine mfg recommended WOT? Is the bottom clean? Are the props damaged?

While I do not have I/O's, enlarging my tabs was an improvement that has paid for itself in fuel savings via improved performance.
 
Hydrofoils are made for smaller/lighter boats. What they do is lift the boat higher out of the water. Worked OK for my 20' but not the 24'.
 
Rick, try switching to 4 blade props. I was running 3 blades on my 310 dancer, and where i boat on the south shore, its a lot of stop and go stop and go (meaning on plane off plane on plane off plane..)

I switched to 4 blade alum and I can hold plane at a lower speed. Helps with docking as well.
 
Thanks all... just getting back to reading this now.
I had problems this past season sometimes getting up on plane with me at the helm, my m-law and f-law, wife and 2 kids all sitting aft. Sometimes... not able to at all. Also, I have the 350+ lb genny on my boat that is coming out... I'm certain that has some affect on it. My boat is 32.5 feet LOA but the twin mercs are 210 hp each... not the 250 hp others are. So I think with the 350 genny and 4 adults and two teens on it (all sitting aft), I was not getting up as quick as wanted. When it was my wife and two kids and myself coming back from Montauk, we really had no trouble getting up on plane, but I wasn't happy with the amount of throttle necessary to stay on plane. I will remove the westerbeke this spring, tune the engines and take it out to see how it behaves. Will make any changes after that.

Thanks regarding the foils... didn't realize they would hamper a boat my size.

--Rick
 
I don't think they will generate that much drag, larger trim tabs probably create more drag.

That said first thing I d check is that your tabs work...

Years years years ago i added a Doelfin to a 25' single stern drive which was hard to get on plane with more than a couple of bodies sitting aft... It made a big difference although at the same time I upgraded the drive lower unit to the then all new Duoprop.

Considering the cost, a foil is worth trying before messing with expensive props

Or you can ask the In laws to temporarily go down below to the vee berth while you accelerate then have them come back. Not only moving some weight temporarily will help, it may also help with the in laws being on board :)
 
I had the same problem getting on plane 5 years ago so I put a hydrofoil on my Carver 2557. My only regret was that I didnt put it on sooner...Works like a charm and I'm on plane in no time and can stay on plane at slower speeds...
 
Rick,

What is your power set up in your Larson? is your hull a full stepped hull?
 
quote:
Originally posted by Ken34

Rick,

What is your power set up in your Larson? is your hull a full stepped hull?

Click to expand...


Hi Ken.
Twin merc 5.7L 2 barrel carbs (not the 4 barrel) Thunderbolt 4 or 5 (can never remember). Duo-Delta Conic notched hull.

--Rick
 
Alphas? 17" props? Aluminum? 3 blades?
What type of tabs do you have.

How long have you owned the boat?
 
The set up you have has been a pretty efficient performer. I am wondering if there is an underlying problem here.

What are you seeing for cruise rpm vs mph on GPS
 
Agree with Ken34.

There is a fellow at my former marina with the same problem you are experiencing. He cruises with his boat (your boat) bow so far up he might as well be sighting the space station. He cruises at 2500 RPM's, no tab, drives out. I would venture to guess I burn less fuel at 24 knots than he does at 18.

Make sure you are reaching WOT RPM as indicated in your manuals. Tuck the drives in. Cruise at the proper RPM.

I would recommend a Piranha composite 4 blade prop for your drives. It made all the difference in the world on my Regal.
 
quote:
Originally posted by Ken34

Alphas? 17" props? Aluminum? 3 blades?
What type of tabs do you have.

How long have you owned the boat?

Click to expand...


Alpha 1 gen 2, prop size.. I don't know, Aluminum -Yes, 3 blade -Yes

1 year last month.
 
I don't know what the cruise speed is supposed to be, but I bring it up on plane and then back the throttle down a bit to about 3/4 and I run at around 25 mph on gps. This is with two adults and two kids and the 350 genny (not on centerline). I've run the boat full throttle with just my son and I to see top speed and I hit 38 on gps. I've read online elsewhere this boat could supposedly hit 50 mph... I can't see that happening... not on mine at least.

I'm just looking to make sure this next season the boat runs as efficiently as possible.

--Rick
 
Rick, the lag on getting on plane when you have people sitting aft is nothing to worry about, just throttle it up more and play with the drives to help it plane easier. Thats what I do when on my 310 when I have people sitting in the aft.

What makes it worse, is our boats have IOs so the motors are right under where people would be sitting. If we had inboards, the motors would be another 2-3 foot towards the bow, which would help with the weight distribution while planing...
 
Fellas please give some slack in here.
Small boats are much more affected by trim factors than bigger boats.
Having said that, it is not a matter of thrust. It is a matter of lift,
and this hydrofoils are a huge improvement to boats without tabs.
This is why folks with smaller size boats will notice huge increases
in performance. Tabs will do the same, but tabs are more $$$ and more
complicate to install, hence the preference for hydrofoils on those
applications.
H
 
To followup... I have bennett hydraulic trim tabs and they work very well. Just wanted to know if foils improve things that much more because the writeup on them says "get on plane faster, faster top speed, lower fuel consumption, better handling, better looking, better sounding and world peace". But again, on a boat my size, it sounds like they would not be helpful. BoatCrazy, your approach is how I handled the Montauk trip and it worked fine. I guess I was a bit surprised that the boat appeared to be a dog with 4 adults and 2 kids (and the genny) when trying to come up onto a plane... but that was earlier in the year and I hadn't quite had a feel for the engine trim and the trim tabs yet.

--Rick
 
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