finally hit something

[MHayes]

thank you, at $415 these seem to be worse than hitting the prop.
anybody tapped or bent out a prop themselves?

You did get the PlanetNautique discount, didn't you?

[Hollywood]

Would you rather have a solid rudder rip off the fiberglass? I'm about to pour a casting right now actually, sometimes "porosity" is a good thing. That actually looks more like shrink. If you want a solid brass casting you can have one, but don't hit anything.

This is the same argument as the underwater gear (strut, fins) being screwed into the hull vs. through bolted. Buy an MC if you want all that "strength" and a hole in your boat.

[tourpro]

Oh yeah Hollywood, its definately a tradeoff. Too much strength and when you DO hit something it's gonna cost even more to fix.


Speaking of which, how do you guys treat unchartered waters when you visit other lakes?

[Andrew]

from a diy point of view, a fiberglass repair would be cheaper than replacing a rudder........ much more work, but still cheaper

[jthooker]

The picture of your rudder shaft is revealing. I’ve seen this type of failure many times in rotating machinery shafts and it looks to me like a fatigue break.

The smooth area you see around the outer face is a progressive fracture zone, or crack, that moved from the outside inward. The crack typically starts at a machining mark around the outside diameter and grows inward from repeated flexing. At some point the remaining interior diameter is no longer large enough to handle the stress and the shaft fails in tension and/or torsion. The interior portion you see that looks like a casting defect was actually the last remaining solid part of the shaft and when it broke the metal tore apart and gave it that appearance. If the rudder shaft had failed due to an impact the entire face of the shaft would look like that.

If you look closely at the picture you can see a narrow dark band (arrows) around the outer edge which is where the crack initially started and became oxidized. As the shaft weakened the crack spread somewhat faster through the brighter area.

My guess is that the “bump” you heard was the rudder breaking off. It probably clipped the prop in the process.

Even the best designed shafts made of special materials can fail quickly due to machining marks if they are under cyclic stress. Our boat rudders are no exception since they are constantly pounded by the beating of prop blades powered by hundreds of horsepower.

[speck]

thanks for all the input guys. here is the followup:
got the new rudder in, works great, yes i got the pn discount and david at white lake shipped it out two day air. great service and price, two thumbs up to white lake marine
i greased the new rudder good with the remote grease fitting, i see a newer thread on this subject. at the end of our ride there was a bit of grease bulged out the top of the rudder assembly.
was having a great ride until i came down hard on my left ankle doing a scarecrow (a routine move for me) so now i am out for two weeks maybe
i can agree with the porsity theory and i am glad the rudder ripped off and the stearn of my boat was untouched. in some intances you want things to give way to save other things.
as far as the crack starting and then growing worse, i have never hit anything ever and the boat is so new that i don't believe the crack was working into itself theory. the shaft was dark on the inside, not on the outside. if it was a bit weak, it probably helped me it this case to just snap off clean, and leave the fiberglass intact. from a casing standpoint i think it just looked suspisious.
the prop i fixed myself had no vibration whatsoever.
i can't see the lastest posts picture/link
thanks

[jthooker]

I'll re-post the picture when I get home tonight.
It got deleted during the server switch.

[jthooker]

Here's the pic with the arrows pointing to the dark band around the outer area. This is what I thought might indicate the beginning of the crack zone.

[MHayes]

Here's the pic with the arrows pointing to the dark band around the outer area. This is what I thought might indicate the beginning of the crack zone.

I think that's just the oxidation on the rudder itself that you are seeing.

[jthooker]

It might be just normal oxidation.
Sometimes hard to tell from a picture.

[hollister]

You do not want a He**-for-strong rudder post. Break away is the desired mode, otherwise that energy is transmitted into your mounts and the boat structure. That kind of damage is far more expensive. CC uses a similar concept with the tracking fins to avoid serious damage to the hull.

[DavidF]

I can tell you from repairing a boat with rudder damage that a properly cast rudder will bend quite a bit before it breaks. Also, the rudder/rudder shaft casting is sufficiently strong to cause hull damage if it hits something strong enough to bend or break it. From that experience, I can confidently say that this situation was the result of a poor rudder casting and that it simply failed. The fortunate part is that it failed going straight ahead and not mid turn.

[speck]

thats what i thought, bad part, but a good result. should they try to do this like a break away derailer arm on a bike? i think so, saves the boat hull damage

[boatech]

the rudder is desighned to snap off when it takes a hit like that so it does not destroy the bottom of your boat. ive changed dozens of them they all look just like yours.