Naiad stabs question

[Miss Jamey Lynn]

Woundering how much of a draw on the drive eng there is when the stabilizers are used verses just on center or does anybody run with the unit off? I can feel the drive eng take on a load when i turn the unit on at idle, so i figure the drive eng would use more fuel when the stabs are used.

 

[SKYCHENEY]

The pump is still turning whether in center, on, or off position, so I doubt there is much difference. Why do ask? Do you think you'll burn less fuel in off position?

 

[GJH]

I was told by two different Naiad specialists to never be under way with them off. Obviously it is not catastrophic because I had done so plenty of times in calm conditions. Centering takes as much power to maintain, so why not just have them on? Per Sky's point the pump is running regardless. Turning them on merely activates the solenoid system.

 

[Capt Paul]

The pump is still turning whether in center, on, or off position, so I doubt there is much difference. Why do ask? Do you think you'll burn less fuel in off position?

I don't think that is true. When turned off the only engine load is spinning the pulley. I can feel and hear the engine load when the system is turned on and the hydraulics are pressurized.

 

[captddis]

There is nothing wrong with the stabs in the center position. Running them off can cause issues. Sometimes big issues. While the pump always runs, it does take horsepower when working.
I can easily hear the take the load on a 12v71.

 

[kelpy]

You will have to pin the fins in the center position if you don't have the system turned on when moving either ahead or astern. Never back down or maneuver with the fins not centered.
I can hear (sort of) the engine (16V-92) pick up the load from the pump at idle but the DDEC readout for fuel consumption does not change.
Read the Naiad operation manual.

 

[SKYCHENEY]

Why was the question asked? What is the purpose? I don't understand why you would not want to run your stabilizers. What do you gain by turning them off?

 

[Glory]

Why was the question asked? What is the purpose? I don't understand why you would not want to run your stabilizers. What do you gain by turning them off?

Stabs are an expensive option, why not enjoy them. I run with mine on line all the time, you never know when another boat wake sneaks up on you and rocks your world. For example when one of the questionable skippers that pass you at 20+ knoty just 50' away, 2 miles off shore.


JM

 

[captddis]

As usual I do it differently.
I only use the stabs when really needed. There is a noticable speed difference when they are flopping back and forth. Most MY's that I have run with the stabs on will throw a slug of air into the props and cause a violent cavitation in the props that shakes the whole boat.

When manuvering around docks, locks etc, I always center the stabs. Nothing like the fin being an unwanted rudder and sending you in a slide in a direction you did not want.

 

[kelpy]

Stabilizer fins will not "throw" a slug of air under the boat. At least ones that are properly designed, programmed and installed.
Stabilizer fins that are flopping around will fail and fail expensively. As I suggested in a previous post, read your Naiad operation manual. You will learn a great deal.

 

[Boatsb]

I have to go with Dave. Use then when you need them. Remember to turn them off before maneuvering.

As to the air getting underneath it depends on the sea conditions. Ive put air under my 41c a few times and launched a 34 a few months back. Get the right conditions and stabilizers will do some crazy stuff. While running a large my I found about a kt by centering them. It was a 9 kt boat at wot. Cruised at 8.5 without them and justt over 7.5 with them.

 

[GJH]

Stabilizer fins will not "throw" a slug of air under the boat. At least ones that are properly designed, programmed and installed.
Stabilizer fins that are flopping around will fail and fail expensively. As I suggested in a previous post, read your Naiad operation manual. You will learn a great deal.

Yes, I just did that. They say if you are going to have them "off" for extended periods while running. put in the centering pins. In thousands of miles of cruising I have never observed the slowing down effect described by others of "on" vs off. and due to absent mindedness, I have had plenty of occasion to run with them on, off and centered and switched between the various modes while running. If they indeed put extra load on the engine at low speed, that's a good thing in my book, though I haven't observed a noticeable difference. We cruise 8-10 knots, BTW.

 

[SKYCHENEY]

I have had the air slug phenomenon happen many times on our short period Great Lakes seas but it is usually in a following sea. I was very concerned the first time I heard it. I pulled every hatch looking for loose strut bolts.

But, as stated earlier, I would not run with them off without pinning them. Center position at slow speeds or when transiting some narrow pierheads. Otherwise I use them even if dead calm. It's nice to counter act that wake that might just catch you by surprise.

And as far as speed, I see absolutely no difference whether they are on or centered. I have tried it many times to see, hoping to get my cruise speed over 16kts, but no help either way. Maybe that's because I only have 4.5 sq ft fins. Another 53ED in our marina has the 6 sq ft fins so maybe that would change things.

 

[captddis]

Stabilizer fins will not "throw" a slug of air under the boat. At least ones that are properly designed, programmed and installed.
Stabilizer fins that are flopping around will fail and fail expensively. As I suggested in a previous post, read your Naiad operation manual. You will learn a great deal.

You must be an expert!!
I have run many Hatteras boats that had factory installed Naiad's and they would cause cavitation in certain sea conditions.

 

[Boatsb]

You must be an expert!!
I have run many Hatteras boats that had factory installed Naiad's and they would cause cavitation in certain sea conditions.

Dave remember that we hold ourselves to a higher standard and refrain from outing the "know it alls".

I never burned a neutral cable either.

 

[bobk]

I have a 48MY with NIADs which I suspect were sized for 15 knot cruise. The boat always was about 0.2 kt slower than the test reports W/O stabilizers at my 1000 rpm, 8.2 kt cruise speed. However, I have many times looked for a speed difference between having them centered and 'on' and have never been able to find a change. They stay in the centered position unless I see a need for them. Yes the pump is running, but the seals and bearings are not getting as much wear. Leaving them off to flop is bad as others have said. And by the way, they should be dropped and resealed at three year intervals when painting. NIAD recommends two years, but three works well for me (6000-7000 miles).

Bobk
1981 48MY

 

[GJH]

Glancing through my manual, Naiad, at least circa 1984, had no recommended interval for changing the seals. I'd been told by some independents 5, and conventional wisdom on the HOF here has been three to five as I recall. Can't comment on the cavitation issue, but am curious as to how it was determined it is caused by the stabilizers... trying to figure out how the air gets under the waterline, swooshed by the fin and to the props? Or are we really just talking water turbulence... still trying to visualize that.

 

[captddis]

Cavitation is unmistakeable. When running in rough weather with stabs on and the boat can cavitate Set the stabs to center and it stops. Stabs back on and cavitation, off no cavitation. Seems obvious what the cause is.


I remember back in 1984 a 55C had issues with the ex temp lights going off when the stabilizers were in operation. Removed the fins and capt ran the boat for a month with no alarms.
They can certainly deflect the flow of water.

 

[SKYCHENEY]

My manual states that seals should be replaced every 2000hrs of run time. For commercial applications, that may be yearly. For us, it is not a matter of hours of use, but time that deteriorates them. That is why Naiad recommends changing them every two years.

I know they will last longer. I am on the 5 year schedule. I see no need to do them any more frequently. It's not a bad job to change them. I posted pics on this site when I did it last.

 

[TopHattandTails]

About a year ago, I asked Naiad about servicing the seals. They indicated that they did not make the seals for the 251-1 system any more and that an upgrade would be required. Where are you guys getting the seal kits?