Bent rudder shaft?

[Searles]

Contrary to popular belief stainless steel is quite soft,and quite easily bent ,from what I can see of the original design there is a bearing above the tiller and ram connection point ,a big rudder going hard astern with no stops or incorrectly set stops using the ram as a stop would bend that shaft ,as I have said ,it’s a poor design .

[jimbunyard]

Just for grins, I've re-oriented the picture.

From the second picture you posted, even with foreshortening, it seems that the shaft is at least 2.5 inches and looks more like 3, unless the arm in the background belongs to Olive Oyl...

From the flats on the top, it certainly looks solid...

The massiveness of the, for lack of a better word, 'quadrant', and the cylinder makes me wonder if the original owner/designer had interests in a mining operation.

Even "contrarially", as before, the force required to bend even a hollow 2.5 shaft (leaving aside that a solid shaft can be easier to bend than a hollow one, depending on the wall thickness...), is tremendous, tens of tons (depending on how the force is applied and measured), and likely exceeds the failure level of the fiberglass structure in which the shaft tube is housed.

Therefore, combined with the lack of any external evidence suggesting other causes, it seems time for a simple 'destructive testing' attempt...

Don't see any rudder stops, so, after removing the bolt holding the ball joint, get a 24" crescent wrench, either have someone hold the rudder or ..., and see if you can twist off the upper portion.

Seems drastic, but it's likely the fastest route to determining your next step...

[boatpoker]

While I agree that the ram is a likely a little oversized, there is not a chance in hell that it would have the power to bend that stock and even if it did it would have destroyed the rudder tube. Also the tiller arm geometry precludes that.

I'm also curious about the boxed in bulkhead and deck going aft from the rudder tube, that does not at all look original. I'd like to see that removed to see whats gone on underneath

Out on a limb ... I think a serious issue has been covered up here and the OP needs a qualified person to examine the entire hull.

[Bowdrie]

Originally Posted by Jim Cate

See post 12 above:"Only thing that comes to mind is the hydraulic cylinder operating against a stuck rudder, or with the rudder up against its stops. Seems unlikely, but sumpin' did the deed!"

Jim

So far, your post has the most merit.
Looking at the pics for a while I'm wondering if the PO originally had the ram and arm mounted up near, or at the top of the shaft.
That tiller arm is really short, indicating a cylinder with a short stroke.
That leads to a very short "throw" from "hard-over to hard-over, and quite acute angles.
In the absence of positive stops, (relying upon the limits of piston stroke,) it is possible to get the rudder in a "dead center" position, where the ram pressure has more effort to push against the shaft instead of turning it.
As if the tiller arm and ram were in a straight line when pressure is applied.
Just thinking out loud,,,

[jimbunyard]

Originally Posted by boatpoker

While I agree that the ram is a likely a little oversized, there is not a chance in hell that it would have the power to bend that stock and even if it did it would have destroyed the rudder tube. Also the tiller arm geometry precludes that.

I'm also curious about the boxed in bulkhead and deck going aft from the rudder tube, that does not at all look original. I'd like to see that removed to see whats gone on underneath

Out on a limb ... I think a serious issue has been covered up here and the OP needs a qualified person to examine the entire hull.

If you look at the re-oriented picture, you'll notice what looks an awful lot like a hydraulic pump to the left of the shaft, with lines appearing to come from the underside of the binnacle, and then leading from the 'pump' to the cylinder.

If that is an electric pump, and not some sort of autopilot, that size cylinder could certainly provide enough power to bend a shaft of that size, were it held correctly.


Regarding the "geometry being wrong", unrelieved overpressure will find the point of least resistance and will relieve itself. Either pushing or pulling (by rotation via a lever at that location) a compromised shaft could result in it being bent as seen in the picture.


Of course, as stated previously,

"...the force required to bend even a hollow 2.5 shaft (leaving aside that a solid shaft can be easier to bend than a hollow one, depending on the wall thickness...), is tremendous, tens of tons (depending on how the force is applied and measured), and likely exceeds the failure level of the fiberglass structure in which the shaft tube is housed."

and even if the shaft was bent by an imaginary Aristotlian lever, the 'fulcrum' (the support holding the tube) would likely be ripped out of the hull...if the other end of the cylinder wasn't ripped from it's mount first.

Unless, of course, there were other 'mitigating factors'; for instance as also stated previously,

"...the upper part of the stock above the intermediate bearing, but below the upper bearing has corroded seriously due to crevice corrosion from water trapped in the rudder shaft tube, and something either jammed the rudder and some zealous cranking on the wheel caused the shaft to bend, or the shaft is so far gone that just normal use put enough load on it to bend it."

hence my 'drastic suggestion'...

I'm guessing the boat is at least 30 years old, plenty of time for crevice corrosion to do it's evil work.

As for there being a big cover up, it certainly looks like the structure supporting the rudder shaft tube is original, at least to me...

[jimbunyard]

See also https://www.cruisersforum.com/forums...-129234-3.html

[sv_pelagia]

Looks like a Wagner hydraulic steering RAM (which would make sense for a BC boat of that age).

[Manateeman]

Maybe it’s not what is in these photos, but what is NOT in them.
Was there at one time an emergency tiller or tiller arm attached to the very top of the shaft on the square surfaces ?
Was this area...the square top end...used as an attachment point, as suggested , for pulling the engine aft?
One of those portable band saws and a can of beer as lube will cut that shaft...maybe it’s corroded quite a bit already...key way?
Well at least they can’t blame this on an ORCA attack. LOL
Mark

[Bowdrie]

Originally Posted by Manateeman

Maybe it’s not what is in these photos, but what is NOT in them.
Was there at one time an emergency tiller or tiller arm attached to the very top of the shaft on the square surfaces ?

In the drawing posted it does appear that the squared end of the shaft was to be used for an emergency tiller, (probably a deck plate above it).
Perhaps there WAS some kind of external load applied.
We search for clues, just like Inspector Clouseau, excuse me, that's Chief Inspector Clouseau.

[TrentePieds]

Right you are, MM :-)!

I looked at the pic again, and I think now, as I did before, that the top of the stock is bent forward in the boats vertical centerline plane. Your diagnosis - that the stock was used by an ignoramus a an anchor point for a chainfall - may very well be correct!

Doesn't seem to me that the steering geometry is such that the ram coulda caused it. Seems to me also that even if it were powerful enuff to have caused it, with the pressure required to do so the hose or its fittings would have burst before the stock woulda been bent.

Another thread, active just now, addresses pitting/crevice corrosion in a rudderstock where it was embedded in the rudder blade. SS, used where you cannot inspect it, is apt to give you surprises :-)!

Cheers

TP

[Nord Sal]

If the ram caused the shaft to bend, there would also be evidence (there might be, can't tell) of torsion having also deformed the shaft, not just bending. The ram's mount on the other end would also have to be robust enough to not fail first.

[ggray]

Of course it is important to determine how this happened (may end up being a guess), but as far as correcting it, the rudder has to be removed, which may not be too difficult. The bottom gudgeon should be removable, and with this done, and maybe removing the top bushing, the rudder should be able to slide out.

I'm going to leave out all the details as it would take too long, but our first keelboat (brand new, too) came with a bent solid SS rudder post. A slight kink right where the rudder post exited the rudder blade. I took it to a machine shop that we did a lot of business with, and his press straightened it right out.

[trashpad]

Has anyone thought that that is just the angle of the rudder shaft and it is not bent? If you go from lock to lock does the top of the shaft move in an arch at all?

[jimbunyard]

It's bent. Look at the picture in post 20 above.

For those imagining that the weight of a 4108, about 500 lbs if I remember correctly, is enough to bend a 2.5 inch shaft, even if applied to the very tip end of a lever that appears to be about 16 inches long, doesn't that imply that a reverse force would straighten it right out?

Surely something could be arranged inside the boat to safely provide 500 lbs of resistance to a force directly aft. If a 'cheater' bar were used, looks like there's enough room to just about double that force, if a( ) suitably strong place(s) is(are) found...

Would be much less likely to rip the rudder tube from the hull, since the hull structure resisting such a force is correctly aligned.


And yes, I'm only being about 60% tongue-in-cheek...

[Celestialsailor]

Originally Posted by jimbunyard

It's bent. Look at the picture in post 20 above.

For those imagining that the weight of a 4108, about 500 lbs if I remember correctly, is enough to bend a 2.5 inch shaft, even if applied to the very tip end of a lever that appears to be about 16 inches long, doesn't that imply that a reverse force would straighten it right out?

Surely something could be arranged inside the boat to safely provide 500 lbs of resistance to a force directly aft. If a 'cheater' bar were used, looks like there's enough room to just about double that force, if a( ) suitably strong place(s) is(are) found...

Would be much less likely to rip the rudder tube from the hull, since the hull structure resisting such a force is correctly aligned.


And yes, I'm only being about 60% tongue-in-cheek...

I had to laugh Jim...here we are all trying to figure out what happened and you come along with this great solution. You're probably correct in just reversing the force. If it worked, at least it might be straight enough to remove the shaft.