Damaged running gear

[PlayDate]

Some quick numbers on the force of the water against the blade surface area and mass of the propeller shaft (worst case not spinning) including the distance to travel to the rudder the impact against the rudder ends up being incidental. Plus the blade contacting the rudder would be at the tip of the blade which would yield and roll over close to the rudder bearing (lowering the bending moment) further cushioning any impact . Unless the rudder was significantly cracked and ready to fall off I can't see this situation panning out.

Tom, while we are waiting for an update from Lawrence......I had a question for you. How does Algonac attach a stainless shaft to a bronze rudder plate?

 

[techmitch]

Tom, while we are waiting for an update from Lawrence......I had a question for you. How does Algonac attach a stainless shaft to a bronze rudder plate?


View attachment 155156Crazy John, I wondered the same when I saw that pic/post earlier about one for sale. Although inexperienced and ignorant to inboards, I was surprised that the shaft didn't travel further into the rudder. After some serious thought, my guess is, a strike would be far more destructive if that was the case.

# Still learning

 

[ttmott]

Tom, while we are waiting for an update from Lawrence......I had a question for you. How does Algonac attach a stainless shaft to a bronze rudder plate?


View attachment 155156

That's a good question; I'd like to know also. The picture of the one sheared off looks to be bronze going through the bearing. I assumed it was all bronze until I saw the replacement picture. All in my boats are stainless inside the hull.

 

[ttmott]

That's a good question; I'd like to know also. The picture of the one sheared off looks to be bronze going through the bearing. I assumed it was all bronze until I saw the replacement picture. All in my boats are stainless inside the hull.

How it's done -

 

[Lawrence Falco]

I’m still waiting on the surveyors report.

 

[PlayDate]

How it's done -

So it looks like the shaft goes into the rudder plate 4" or so in the video. That definitely is not what I see on Lawrence's rudder shaft. His looks like the shaft is cast bronze where it broke off.

Additionally......maybe it is just me.....I would not have thought pouring bronze on top of a Stainless Steel shaft would create any real bond between the metals unless the stainless was really cherry red hot.

 

[hughespat57]

So it looks like the shaft goes into the rudder plate 4" or so in the video. That definitely is not what I see on Lawrence's rudder shaft. His looks like the shaft is cast bronze where it broke off.

Additionally......maybe it is just me.....I would not have thought pouring bronze on top of a Stainless Steel shaft would create any real bond between the metals unless the stainless was really cherry red hot.

You any see it for a moment but the SS shaft looks to have a machined end with a nut threaded/ welded to the shaft end.
So you have a physical interlock with the bronze as well.

 

[ttmott]

You any see it for a moment but the SS shaft looks to have a machined end with a nut threaded/ welded to the shaft end.
So you have a physical interlock with the bronze as well.

Aside from the connection process his real question is why does the bronze fracture look to be so close to the packing gland/bearing. I agree the stainless should show deeper into the rudder casting below the hull based upon the random casting video. That's not to allude a defect but more an observation.

 

[Woody]

You any see it for a moment but the SS shaft looks to have a machined end with a nut threaded/ welded to the shaft end.
So you have a physical interlock with the bronze as well.

 

[hughespat57]

Aside from the connection process his real question is why does the bronze fracture look to be so close to the packing gland/bearing. I agree the stainless should show deeper into the rudder casting below the hull. That's not to allude a defect but more an observation.

I dont believe his was a stainless shaft

 

[Morgan Jane]

Well.....I will tell you my story.

I was on my way back from Tides Inn on the Rappahannock/Chesapeake Bay/Potomac River up to DC 18 years ago with a girlfriend.

It was a great cruise, perfect weather running 24 knots the whole way. Then directly across from Fort Washington we hit something. The water is 65' deep there and we never saw what it was. If I had to guess.....it was what we refer to as a Potomac alligator which is a large cut piece of wood that is barely buoyant. The hillbillies at the headwaters of the Potomac figure it is just easier to throw tree work into the Potomac than pay to get rid of it.

The problem is this is where the prop tunnels can intensify the damage. I like prop tunnels but if something gets between the prop and tunnel.....both lose.

Anyway.......the port engine dies and the starboard prop is making a clacking sound. The port strut had torqued and cracked the strut mount on the hull and we started to take on water. Fortunately, we were a mile from the Fort Washington Marina that has a travel lift. We headed to the marina with the starboard engine.

About 30 minutes later the boat was out of the water on a Emergency Haul out and the damage was the strut pad, two shafts and two Nibral props (badly damaged). Fortunately we weren't that far from home so we had it blocked and caught a taxi home.

It took almost a month before it was ready to go back in the water. The strut pad had to be completely ground down and rebuilt. The mechanic that did they work did a great job and I sourced the shafts and props. The only advice he gave me was that if I paid cash it would be done in a month. If I used my insurance........it could take 4 months to get the approval to do the work. Allegedly......structural damage to the hull usually requires the insurance company to send out a marine engineer to inspect the hull and write up the process to rebuild the strut pad.

Anyway.....stuff happens ......it is just part of boating. I hope your damage is minor.

I think I hit the same log you did this summer. I was directly across from Fort Washington and BAM!... Real hard, thought I knocked a hole in the hull. limped back to the Occoquan and had the boat hauled a few days later. Just one bent prop was all. I did win this years Bent Prop Award this year though from my cruising club.

 

[Lawrence Falco]

Ok so the marina sent a surveyor down and here is there response:

Larry,
This picture shows the set screw is sheared off.. The screw originally had a rounded point on it to seat into the dimple in the shaft. So, the rounded point got sheared off and dragged out with the shaft. I can see the drag marks on the coupler where the tip of the screw that was sheared off scratched the interior of the coupler. This assures us that, that set screw did not come loose.

An Independent 3rd party Marine Surveyor visited the boat on or about Dec. 5 and inspected the damage. The findings were as follows. It appeared that the boat "had an allision with a submerged object". While everything else was checked the Marine Surveyor reported the following.

"It is the opinion of this surveyor that the vessel picked up a rope or line. As it tightened up and
pulled the shaft out of the coupling and out the bottom of the vessel.
The set screw threads were seized and no moment was sighted
The set screw shoulder was sheared off and scar was sighted on the coupling as the shaft exited the
shaft coupling.
The brass key was sheared."
"The coupling bolts were tight."
We recommend you contact your insurance company and file a claim for this damage. It is the result of an accidental collision with an unseen submerged object and not the result of poor craftsmanship.:

I don’t get it we didn’t hit anything and if we picked up a line that would pull the shaft out. Not sure how to proceed. I paid by credit card. Insurance sent me the check.

 

[ttmott]

Ok so the marina sent a surveyor down and here is there response:

Larry,
This picture shows the set screw is sheared off.. The screw originally had a rounded point on it to seat into the dimple in the shaft. So, the rounded point got sheared off and dragged out with the shaft. I can see the drag marks on the coupler where the tip of the screw that was sheared off scratched the interior of the coupler. This assures us that, that set screw did not come loose.

An Independent 3rd party Marine Surveyor visited the boat on or about Dec. 5 and inspected the damage. The findings were as follows. It appeared that the boat "had an allision with a submerged object". While everything else was checked the Marine Surveyor reported the following.

"It is the opinion of this surveyor that the vessel picked up a rope or line. As it tightened up and
pulled the shaft out of the coupling and out the bottom of the vessel.
The set screw threads were seized and no moment was sighted
The set screw shoulder was sheared off and scar was sighted on the coupling as the shaft exited the
shaft coupling.
The brass key was sheared."
"The coupling bolts were tight."
We recommend you contact your insurance company and file a claim for this damage. It is the result of an accidental collision with an unseen submerged object and not the result of poor craftsmanship.:

I don’t get it we didn’t hit anything and if we picked up a line that would pull the shaft out. Not sure how to proceed. I paid by credit card. Insurance sent me the check.

That's my takeaway also based upon the photos and narrative.
I suspected also a rope or chain as the strut was not damaged.
It now seems no fault of the work that was done.
This would be a separate insurance claim.
Man - if you didn't have bad luck.....

As an edit also take a close look at the engine mounts and mounting hardware as well as the gear case and bearings.

 

[PlayDate]

That is consistent with what I see as well. It is a new claim for you and your insurance to deal with.

As to what did it…I come back to the damage on the boat bottom. No repair facility would have splashed the boat with that damage.

I assume you hit a marker of some kind that fouled the prop and was just at the right angle to rip the prop, shaft and rudder out of the boat. @ttmott probably can calculate the force required to do it. 10 tons of boat moving at 10 mph is a lot of force.

It doesn’t matter what the obstruction was since it is now officially an accident.

 

[ttmott]

That is consistent with what I see as well. It is a new claim for you and your insurance to deal with.

As to what did it…I come back to the damage on the boat bottom. No repair facility would have splashed the boat with that damage.

I assume you hit a marker of some kind that fouled the prop and was just at the right angle to rip the prop, shaft and rudder out of the boat. @ttmott probably can calculate the force required to do it. 10 tons of boat moving at 10 mph is a lot of force.

It doesn’t matter what the obstruction was since it is now officially an accident.

It would be difficult as we don't know the friction coefficient from the coupler clamping force. It's easy to calculate the shearing of that little set screw - It's ultimate strength times the square inches in cross section. Lastly, there is a phenomena called "stiction" or static friction; that force required to start the initial movement which can be significant. So there would have to be quite a shock force then the pulling force.
What's interesting is the OP said he didn't really feel anything when it happened - I would have thought it would have been a significant bang. Consider the carnage if the coupler didn't release.....

 

[Stee6043]

However you end up with your insurance claim(s), I recommend you make an offering of some sort to Poseidon before you get splashed again

 

[Flyer5]

Ok so the marina sent a surveyor down and here is there response:

Larry,
This picture shows the set screw is sheared off.. The screw originally had a rounded point on it to seat into the dimple in the shaft. So, the rounded point got sheared off and dragged out with the shaft. I can see the drag marks on the coupler where the tip of the screw that was sheared off scratched the interior of the coupler. This assures us that, that set screw did not come loose.

An Independent 3rd party Marine Surveyor visited the boat on or about Dec. 5 and inspected the damage. The findings were as follows. It appeared that the boat "had an allision with a submerged object". While everything else was checked the Marine Surveyor reported the following.

"It is the opinion of this surveyor that the vessel picked up a rope or line. As it tightened up and
pulled the shaft out of the coupling and out the bottom of the vessel.
The set screw threads were seized and no moment was sighted
The set screw shoulder was sheared off and scar was sighted on the coupling as the shaft exited the
shaft coupling.
The brass key was sheared."
"The coupling bolts were tight."
We recommend you contact your insurance company and file a claim for this damage. It is the result of an accidental collision with an unseen submerged object and not the result of poor craftsmanship.:

I don’t get it we didn’t hit anything and if we picked up a line that would pull the shaft out. Not sure how to proceed. I paid by credit card. Insurance sent me the check

It would be difficult as we don't know the friction coefficient from the coupler clamping force. It's easy to calculate the shearing of that little set screw - It's ultimate strength times the square inches in cross section. Lastly, there is a phenomena called "stiction" or static friction; that force required to start the initial movement which can be significant. So there would have to be quite a shock force then the pulling force.
What's interesting is the OP said he didn't really feel anything when it happened - I would have thought it would have been a significant bang. Consider the carnage if the coupler didn't release.....

I wonder if the clamping force would be lessened if the set screw were tightened before the clamp bolts were tightened? Or would the set screw just crush? I would think a properly tightened clamp on coupler having the shaft ripped out would take significant force. It that is the case I would think the transmission should also be thoroughly be inspected before proceeding on the journey. I really hope your trip gets better from here.

 

[Skybolt]

That is consistent with what I see as well. It is a new claim for you and your insurance to deal with.

As to what did it…I come back to the damage on the boat bottom. No repair facility would have splashed the boat with that damage.

I assume you hit a marker of some kind that fouled the prop and was just at the right angle to rip the prop, shaft and rudder out of the boat. @ttmott probably can calculate the force required to do it. 10 tons of boat moving at 10 mph is a lot of force.

It doesn’t matter what the obstruction was since it is now officially an accident.

It would be difficult as we don't know the friction coefficient from the coupler clamping force. It's easy to calculate the shearing of that little set screw - It's ultimate strength times the square inches in cross section. Lastly, there is a phenomena called "stiction" or static friction; that force required to start the initial movement which can be significant. So there would have to be quite a shock force then the pulling force.
What's interesting is the OP said he didn't really feel anything when it happened - I would have thought it would have been a significant bang. Consider the carnage if the coupler didn't release.....

And what I was saying from the start. I can't imagine running the boat and not feeling this happen. Seems unimaginable for that to have happened.

The force needed to rip/pull the shaft from the boat like this is also unimaginable. One would expect more damage to have happened, but does explain the rudder being sheared off.

 

[Lawrence Falco]

And what I was saying from the start. I can't imagine running the boat and not feeling this happen. Seems unimaginable for that to have happened.

The force needed to rip/pull the shaft from the boat like this is also unimaginable. One would expect more damage to have happened, but does explain the rudder being sheared off.

Again hitting a stationary rock ripped nothing off. I just don’t get it. Anyway time to get her repaired.

 

[PlayDate]

It would be difficult as we don't know the friction coefficient from the coupler clamping force. It's easy to calculate the shearing of that little set screw - It's ultimate strength times the square inches in cross section. Lastly, there is a phenomena called "stiction" or static friction; that force required to start the initial movement which can be significant. So there would have to be quite a shock force then the pulling force.
What's interesting is the OP said he didn't really feel anything when it happened - I would have thought it would have been a significant bang. Consider the carnage if the coupler didn't release.....

Okay.....I will admit this has been rattling around my head today. I think this is the right Force equation to use:

If I use 20,000 lbs (weight of the boat) and 12 miles per hour of speed ....I get 96,276 foot pounds (48 tons) of Force. I am sure I am missing something but that is a lot Force to exert on clamp coupling. I can't imagine any clamp coupling holding up to that.

Certainly geometry and a host of other variables could reduce it but I will bet if I set up a hub on my 50 ton press with a shaft locked in place.....it would push it out of the hub and shear the lock bolt without even getting close to 50 tons of pressure.

As Tom noted earlier......I would expect the initial amount of Force needed to shear the lock bolt to be one value and the Force needed to push it out of the hub to be far less.