The total mystery of the 23 Lancer Inboard heavy steel plate ( see photos )

The total mystery of the 23 Lancer Inboard heavy steel plate ( see photos )

Paul
Paul

March 12th, 2012, 6:29 pm #1

Jerry and I have been talking about similar issues on our 23 Lancer inboard projects, and we recall some comments Chris Smith made to me at Bay Harbor a year ago.

Chris said the 23 with the prop pocket had some "noise issues" and I thought that was odd. I did not follow up at the time but I hope to revisit this conversation sometime soon.





Here is a closer look at that thick steel plate




Here is Rickard's 23 inboard now in Sweden, showing the same blue angle iron supports for mufflers I found aboard my 23. I see some bolts for securing the strut but can not tell if the steel plate is there or not in this photo.



The strange thing about this issue, Jerry and I both have the same steel plate on different years of 23 Lancers. Glenn, Mike, Paul M, do you guys also have steel plates at the strut mounting location? On mine you will notice it looks like someone had bolts too long and without enough thread, so as a quick fix they used heavy aluminum blocks to quickly make up the difference. I don't think Chris Craft would have combined aluminum and steel like this with a bronze bolt going through it, this looks more like something done by a previous owner or marina. The fact that the steel plate is there, however, is really strange. It is only secure at the 4 bolts holding the strut, it is not even secure at the starboard and port ends. It looks like it is some sort of a harmonic tuning fork to counter-act some harmonics Chris Craft may have experience when developing this boat. It looks like some sort of a remedial after-the-fact adaptation to solve a problem they discovered after the boats were designed.

In the first two photos above, the rubber mufflers I have were resting on the steel plate just because it was there. It puzzles me as to why CC would put a big piece of steel in a boat like this. It serves no logical application I can see.

Anyone ??

best,

Paul

















Last edited by FEfinaticP on March 13th, 2012, 1:09 pm, edited 1 time in total.
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Paul A. Mathias
Paul A. Mathias

March 12th, 2012, 11:19 pm #2

Paul,
No steel plate in mine.
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Joined: February 2nd, 2007, 5:28 pm

March 13th, 2012, 12:32 am #3

Hello Paul and Jerry,

I too spoke with Chris Smith at one of the events and asked about the "prop pocket" design on the 23.
He did state that he had some customers complain about "noise". Well, I figure he was speaking of possible cavitation in the tunnel. Unfortunatly, I have experienced the noise in my family 24ft PennYan "Tunnel Drive". You only hear it under heavy load. I question the relative "noise" that may come from this design on the Lancer. The PennYan has a full tunnel. The problem starts with the tunnel size and capacity to move water through it. The prop can spin and cavitate. That is the source of PennYan's problem. The Lancer's Prop Pocket should not cause a problem, however, if logic and the facts from Chris Smith dictates... You may very well hear some type of noise that reverberates down below.
I am attaching two photos of the PennYan tunnel drive for comparison.

I know one thing.. Either of these hotrod Lancers will be pulling away from Ghost Rider.

Regards,
Bill http://www.network54.com/Realm/tmp/1331598260.JPG
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Jerry
Jerry

March 13th, 2012, 12:36 am #4

Jerry and I have been talking about similar issues on our 23 Lancer inboard projects, and we recall some comments Chris Smith made to me at Bay Harbor a year ago.

Chris said the 23 with the prop pocket had some "noise issues" and I thought that was odd. I did not follow up at the time but I hope to revisit this conversation sometime soon.





Here is a closer look at that thick steel plate




Here is Rickard's 23 inboard now in Sweden, showing the same blue angle iron supports for mufflers I found aboard my 23. I see some bolts for securing the strut but can not tell if the steel plate is there or not in this photo.



The strange thing about this issue, Jerry and I both have the same steel plate on different years of 23 Lancers. Glenn, Mike, Paul M, do you guys also have steel plates at the strut mounting location? On mine you will notice it looks like someone had bolts too long and without enough thread, so as a quick fix they used heavy aluminum blocks to quickly make up the difference. I don't think Chris Craft would have combined aluminum and steel like this with a bronze bolt going through it, this looks more like something done by a previous owner or marina. The fact that the steel plate is there, however, is really strange. It is only secure at the 4 bolts holding the strut, it is not even secure at the starboard and port ends. It looks like it is some sort of a harmonic tuning fork to counter-act some harmonics Chris Craft may have experience when developing this boat. It looks like some sort of a remedial after-the-fact adaptation to solve a problem they discovered after the boats were designed.

In the first two photos above, the rubber mufflers I have were resting on the steel plate just because it was there. It puzzles me as to why CC would put a big piece of steel in a boat like this. It serves no logical application I can see.

Anyone ??

best,

Paul
















Paul and All:
Here is the plate I took out. It is 3/4 inches thick. The ends were not supported by anything and it was attached only with a wood blocking plate above and below the plate. There was a wood blocking plate on top of the plate and you can see the general area on the plate where there was some rust pitting. I had no aluminum spacers.



Here is a before photo with the plate in place, under the rudder and prop, although it is hard to distinguish. The wood blocking plate with the 4 washers was on top of the plate and in this photo was not set in place. The plate was not supported at its ends.



Also interesting for me to see is how your rudder and steering cable was set up. Mine was different, but had the same parts. The piece of hardware that clamps onto the outside housing of the steering cable in your photo was attached to the wooden plate that the rudder post goes through on my rig. Who knows what was original and what was refurbished?
Jerry
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Mike G
Mike G

March 13th, 2012, 12:45 am #5

Here is a shot of the strut plate. I have 3/4 wood and then same Heavy steel plate

Finishing up the Bulk Heads
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Jerry
Jerry

March 13th, 2012, 12:53 am #6

Paul and All:
Here is the plate I took out. It is 3/4 inches thick. The ends were not supported by anything and it was attached only with a wood blocking plate above and below the plate. There was a wood blocking plate on top of the plate and you can see the general area on the plate where there was some rust pitting. I had no aluminum spacers.



Here is a before photo with the plate in place, under the rudder and prop, although it is hard to distinguish. The wood blocking plate with the 4 washers was on top of the plate and in this photo was not set in place. The plate was not supported at its ends.



Also interesting for me to see is how your rudder and steering cable was set up. Mine was different, but had the same parts. The piece of hardware that clamps onto the outside housing of the steering cable in your photo was attached to the wooden plate that the rudder post goes through on my rig. Who knows what was original and what was refurbished?
Jerry
Paul and All:
I just said that the plate was not supported at its ends, but my memory is incorrect. In the photo, the plate is resting on top, or nearly on top, of the engine logs. However, it was not attached by bolts.

I am beginning to believe Paul's original assessment is correct. The plate is a noise dampner of some sort. It acts to transfer the virbrations of the strut and its immediate area in the prop tunnel hull to the whole hull via the engine logs. Paul, is yours resting on the logs also? The weight of the plate alone, some 38 pounds, would be enough to dampen some of the sound and virbration. This is also interesting because the presence of the prop tunnel would act to stiffen the hull and I would think that there would not be opportunity for much virbration there.
Jerry
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Joined: February 16th, 2012, 3:26 pm

March 13th, 2012, 1:19 am #7

Gentleman,

For what it's worth, my 73 has the plate but I also have an early model 75 that does not. I always figured as you guys have determined that it was some sort of harmonics equalizer. The referenced noise is not something I have encountered on either boat.
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Mike G
Mike G

March 13th, 2012, 3:44 am #8

I have no idea but a 38lb steel plate seems like an over kill for a sound deading device. I would think that a backing plate made of 3/4 wood could oven done a better option. My thought is the steel created a very rigid / strong support for the strut when pressure was from the boat moving in either direction other than straight. For instance a sharp hard to Port/SB. Thoughts on that?
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Joined: October 13th, 2011, 3:05 am

March 13th, 2012, 12:38 pm #9

Lets face it steel was much cheaper back then, and doesn't rot !!!!!!
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Paul
Paul

March 13th, 2012, 12:58 pm #10

I have no idea but a 38lb steel plate seems like an over kill for a sound deading device. I would think that a backing plate made of 3/4 wood could oven done a better option. My thought is the steel created a very rigid / strong support for the strut when pressure was from the boat moving in either direction other than straight. For instance a sharp hard to Port/SB. Thoughts on that?
Harmonics can cause mechanical failure. This is why they don't allow large groups of people in parades or formation to march across bridges, the harmonic can set up a wave that can be destructive.

I found out doing first time research at Vanderbilt University for their FEL (Free Electron Laser, a peacetime application of Reagan's Star War Program adapted to medicine) years ago, that eveything in the sub-micron world is moving more than we think, and even a concrete slab can assume an S-wave like a bed sheet when a 60-cyle motor is bolted to it, but you don't see it because it is sub micron. Doing work with lasers discovered that even a cool rain on the roof would cause the roof structure to constrict and throw off all the instruments that were attached to the walls. At the time we were doing work with a beam that had a moment arm of 3 microns at 100-feet, and it could cut the Vanderbilt logo out of a single human cell of 19 microns wide.

Okay I know this is getting off topic, but harmonics can most certainly cause metal fatigue. Ultrasonic vibration cutting (UVC) exploits this in a positive way. Uncontrolled vibration at the strut would probably have an affect at the prop shaft and I figure it would be right there between the prop and the strut with a conchoidal fracture. I have seen them before, and they look like a piece of glass with a big smooth tear and no sharp edges; it can happen to glass, steel, and hard rock.

Now that we know this steel plate is not something of a junk-yard engineering feature because it has shown up on several boats, it simply must be there for vibration control. It does make sense too, because as I and some others (Jerry) have confirmed, the plate is only bolted at the center and the ends stick out there several inches on each side in a "tuning fork" manner, most likely intended to vibrate in a way to counteract the harmonics set up by the prop in the pocket.

Not being aware of this at the time, but having a fear of re-engineering a boat this size, I decided to stay with the same gear reduction package Chris Craft used instead of going off on a tangent and using direct drive and a smaller (13") propeller like some people have done with 23 Lancer hull conversions. I got reports of speed but I like the fact that the shaft is turning a bit slower with a larger prop (stock prop on a 23 Lancer is a rather monstrous 15 x 15 cupped). In optimum conditions spinning that particular prop (for all purposes it is a 16 pitch) at 4500 rpm and 3000 shaft speed, the 23 Lancer would be in the 35 to 36 mph range maybe a bit more, once you factor in 15% slippage/drag. I figure if CC chose the gear reduction and prop sizes for a boat this hefty, it would be risky to try to re-engineer it because something would likely be lost. In the gentlemans racers that use the direct drive and 13" props spinning much faster, I think what they lose is the ease of getting out of the water and the ability to carry a loaded boat without bogging down. Those gentlemans racers generally only have two people aboard, but with 6 or 9 people on board GOOD LUCK getting out of the water with a 13" prop sort of thing. The smaller props on the direct drive setups may not have the harmonic issues encountered by the big prop. Chris Craft probably saw the need for the big prop first, encountered the vibration issue, and fixed it with a steel plate, in that order. Newer boats that do not have the plate may actually have a slightly different shaft length, perhaps a different profile on the prop pocket, perhaps a bit more clearance from tip of prop to fiberglass hull. Since I have encountered a chonchoidal fracture of a 1" stainless steel shaft before on a 17' wood speedboat with a 95 horse flathead, I am really wondering how long a 1" shaft is going to last with the torque of a 427 in my project boat. Therfore when it comes time to get that new prop shaft, I'll need to take a long look at the yeild strengths of the various stainless steels available, monel, aquamet, etc., because some of the harder materials are actually more prone to fracture. Probably in the end the highest yeild strength will offer the best longevity.

I think it will be especially prudent for all inboard Lancer owners to be aware of the prop balance and shaft alignment, as any faults there may be amplified by the inherent tendency of this particular boat to vibrate.

??

Best,

Paul






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