stabilizers on a 55c

[34Hatt]

Rob, thanks for all you put into that post. I appreciate it.

The side which generated the most vibrations was stbd, and prior to alignment, the coupler/shaft was found to be too low. That was adjusted and rechecked in the water. In the process of doing that, the mounts were all gone over, and in some places some bolts and shims replaced/adjusted. As recent as a month and a half ago it was dial-indicated while I was watching. You also don't preceive any hop at all in the shafts when the boat is trucking along.

We once again checked everything connected to rudders while the boat was doing a fast cruise just last week, and nothing was vibrating back there. I didn't think it would after the work done on rudders.

My prop guy does a totally manual process where he scribes them and lays them out by hand in a really painstaking method. The running gear subcontractor that referred him to me originally years ago explained that his is the only true way of getting the right setup from root to tip and everything in between. When I explained that maybe we should send these wheels out to another shop he told me I'd just be wasting my time, and that the shops reliant on computer methods just compare root and tip measurements and anything variable or out in between likely wouldn't even get picked up. He also said that they don't do any hammer work, but rather just turn the root of the blade red-hot and do a quick tool bend. It's quick production work and it's fine if you're not too fussy, is what I was told. It's not S2 conditioning. I'm no prop guy and don't want to be, but I've heard too many locals in the boat industry around here say that if High Seas said to use this guy on props, use that guy. They know what they're talking about.

With all that being said, if it didn't do pretty much the same thing with 2 completely different sets of wheels, I think I'd still spend the money and have another shop look at the wheels, but there you have it. And this same combo of High Seas and Preferred Propeller had my old 45c dialed PERFECTLY. Not a hint of any vibration at any speed. I used to get comments on it regularly by inboard boaters that knew what to look for.

I've got one fin off and once I've got a good high tide tomorrow AM I hope to have the other off. That should tell me plenty. Tell you what, you end up standing on that cheater bar every bit as much as you do on a prop nut! I was using a 4 footer, and I was happy for every inch. It's just tough to get any decent leverage in 6' depth when doing it.

I'll let you all know how the 1st check ride w/no fins goes. I'm hoping for smooth sailing and lots of rpms. It makes sense -- these 6 1/2's are some big honking fins.

So how did it goe with the Fins off???????

 

[Paul45c]

Hi, Dan. Sorry, I forgot to finish the story. With the fins off, the vibration is gone. I think the problem was that the oversized 6 1/2 sq. ft. fins just reached too deep down and fouled the water flow to those blades. FWIW, I've heard that some 4 and 5-blade props really shine in applications where getting "dirty" water flow to the props is an issue. Regardless, I know now that the fins were making it turbulent back there.

Oddly enough, I really didn't see a speed or rpm bump pretty much at all after removing the fins. I'd expected to at least pick up a knot and maybe 50-100 rpms. Not so. If anything, I might have gotten a half a knot and no appreciable rpm pickup.

But, I added an extra variable. I had my blower drive gears changed up to the stepped up gear (37 teeth vs. 40) and now I'm making rpms just fine (about 2350). That finally did the trick. She just needed more air stuffed in.

I think I'll put the 3 sq. ft. fins back on and call it a day.

 

[Paul45c]

Just as a more recent follow-up to this whole long story, does anybody know of a source of used Naiad fins? I still haven't hauled out yet to effect the change to smaller fins I was talking about.

 

[aksong]

I have 6 sq fins and would like to buy/trade for 9's

 

[GJH]

Try Stabilized Marine in FL for possible used fins.

(954) 797-7330

Bigger is not always better in this case. Naiad has good guidelines for proper fin size. You also want to make sure your system can handle them even if they are theoretically right for your boat. The folks at SM above could guide you, or call Naiad. It depends on boat size, hull form and speeds. I went through the drill last winter when I had to replace one of mine and could possibly get a pair of larger. I ended up staying with 6 footers; I have a 252 system. A new fin is close to three grand.

http://www.naiad.com/