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So it has been a very long time since I have publicly participated in any with the community, though it does not mean that I have been completely inactive. I have been dabbling in trying to design a receiver, working a conversion of a 1:144 Revell Type-206A as well as having a lot of fun with a 4 year old little one. One of the other things that has always interested me is doing a conversion of the 1/72nd Skipjack into a George Washington class. There are many that have wanted to do more with the GW, but there has always been a lack of information, particularly on the details of the size of the missile compartment, how it was inserted in, and details around the sail and stern planes. I think that I have some pretty good information on this. This is not a perfect understanding, but pretty dang good. Enough that I can start making a model of it in CAD and using some eyeball judgements with pictures to come up with the rest. So let me lay out what I have for you, and I would love to get some input.
My picture references come from a very grainy picture of the hull outline of the GW, as well as Layout drawings from Piping TABs for the 611 and 654 boats, and lastly a document that reported methods of determining resonant frequencies of 598 hull (it really has a lot of great information contained in here) - link to document. I have attached some of my research that I have scaled pictures and overlaid them for comparison. Here is an online link for viewing it. First time I have used this method, please let me know if there are issues. Please be sure to download this and take a good look at it before continuing to read the post below.
So let's start with the basic question of how long is the missile compartment. We know that the boat is 130' longer than an original Skipjack boat. David Merriman had reached out to Jim Christley and published Jim's answer on the subject here. It is interesting that in this answer, Jim references Friedman stating that the insert overall is 141' with the missile section coming in at ~78'. After scrounging through the web and digging through a few books, there are lots of answers for this. I started to dial in, though, on the concept that the missile compartment itself was actually a common design that was intended to be used in later classes of boats. All the 41 for Freedom boats have a 16 tube 33' diameter compartment. This allowed me to use internal layout diagrams from the later boats to see how long the compartment was. Based upon some estimating from this method, I had determined the length to be between 76' and 77'. I later went digging through the report on the Hull Dynamics, and I found it directly stated that the missile compartment was 76.0' long (from table found on page A-14 also shown below).
From this table, there is even more information that can be gleaned. The first is that the boat was "split" at frame 44 of the original boat. The missile compartment also gained unique frame numbers starting with M. It seems, though, that some of these M frame numbers were given to areas of the bow section of the boat that remained from the original Skipjack external shape, but were heavily reconfigured. There is also a hint here of how long the compartment really was, but you need to look at the next chart to really start to understand this, and then be able to go back to the chart and recalculate a final answer. So without further ado, here is the next chart from page B-8.
This chart shows the actual shape of the hull plotted in a graph. Because the axis of the chart cause the hull length to be shown in a compressed fashion, it highlights a few key facts. The first is you will see there is a dashed line (a centerline dash, not the regular dashed line) that shows the hull centerline with respect to zero. You will notice that for a length of approximately 140' there is a deviation from center. This is caused because the hull insert was aligned at the keel to the Skipjack hull shape and not at the top of the boat. You will also see the length that were used to fair this into the hull. From a hydrodynamic standpoint, this allowed some of this offset to be hid under the decking that was already going to be used to fair in the missile tubes. Referencing this back to the previous table, one can begin to compare the station position with the graph of the hull shape, and you find that the total hull insertion, including the forward and aft fairing lengths was 140.92' long.
This length actually is very close to what Friedman stated it was. How does this square up with the boat only being 130'. I believe that ~10' were cut out of the original Skipjack bow shape to accommodate this. The accuracy of the Dynamics Report have no reason to be doubted, especially given their mission, and the overall length of the boat has no reason to be doubted either.
In my research (documented in the PowerPoint) I also came across the interesting observation that sails of the 41 for Freedom boats essentially were common in their shape. The sail planes, the sail cross section, and the sail planform all appear to be the same except for minor modifications. The location of the sail with respect to the missile compartment also seems to be within 1' of one another. The main difference is the waterline at which the sail planes were located. Each of the major classes seemed to have a different position. This, now allows a modeler to create an accurate sail and sail planes.
One last tidbit that came from the Dynamics Document was the propeller diameter. The diameter (assuming the later style prop) was 16', and it weighted 23,550lbs (found on page h-14).
So what is missing to create an accurate conversion of this boat? The deck fairing forward and aft of the immediate missile section would have to be done by eye. I think that this would not be too difficult, but it would be done only with the very grainy planform views, and pictures of the boat. The other item is the shape of the stern appendages. These once again can be estimated from the very grainy planform views, but the lower rudder length is cut off in these views. I do think, though, that one could make a good estimate of these, and the airfoils used are going to be a NACA 0016-22 range. Even, I would not be surprised if the sail used a NACA 00xx airfoil cross section.
Give me your thoughts. Make sure to take a look at the PowerPoint as well. It has a lot more picture analysis that would be hard to add here. I have added a teaser below, but there is a lot more in there.
Adam
My picture references come from a very grainy picture of the hull outline of the GW, as well as Layout drawings from Piping TABs for the 611 and 654 boats, and lastly a document that reported methods of determining resonant frequencies of 598 hull (it really has a lot of great information contained in here) - link to document. I have attached some of my research that I have scaled pictures and overlaid them for comparison. Here is an online link for viewing it. First time I have used this method, please let me know if there are issues. Please be sure to download this and take a good look at it before continuing to read the post below.
So let's start with the basic question of how long is the missile compartment. We know that the boat is 130' longer than an original Skipjack boat. David Merriman had reached out to Jim Christley and published Jim's answer on the subject here. It is interesting that in this answer, Jim references Friedman stating that the insert overall is 141' with the missile section coming in at ~78'. After scrounging through the web and digging through a few books, there are lots of answers for this. I started to dial in, though, on the concept that the missile compartment itself was actually a common design that was intended to be used in later classes of boats. All the 41 for Freedom boats have a 16 tube 33' diameter compartment. This allowed me to use internal layout diagrams from the later boats to see how long the compartment was. Based upon some estimating from this method, I had determined the length to be between 76' and 77'. I later went digging through the report on the Hull Dynamics, and I found it directly stated that the missile compartment was 76.0' long (from table found on page A-14 also shown below).
From this table, there is even more information that can be gleaned. The first is that the boat was "split" at frame 44 of the original boat. The missile compartment also gained unique frame numbers starting with M. It seems, though, that some of these M frame numbers were given to areas of the bow section of the boat that remained from the original Skipjack external shape, but were heavily reconfigured. There is also a hint here of how long the compartment really was, but you need to look at the next chart to really start to understand this, and then be able to go back to the chart and recalculate a final answer. So without further ado, here is the next chart from page B-8.
This chart shows the actual shape of the hull plotted in a graph. Because the axis of the chart cause the hull length to be shown in a compressed fashion, it highlights a few key facts. The first is you will see there is a dashed line (a centerline dash, not the regular dashed line) that shows the hull centerline with respect to zero. You will notice that for a length of approximately 140' there is a deviation from center. This is caused because the hull insert was aligned at the keel to the Skipjack hull shape and not at the top of the boat. You will also see the length that were used to fair this into the hull. From a hydrodynamic standpoint, this allowed some of this offset to be hid under the decking that was already going to be used to fair in the missile tubes. Referencing this back to the previous table, one can begin to compare the station position with the graph of the hull shape, and you find that the total hull insertion, including the forward and aft fairing lengths was 140.92' long.
This length actually is very close to what Friedman stated it was. How does this square up with the boat only being 130'. I believe that ~10' were cut out of the original Skipjack bow shape to accommodate this. The accuracy of the Dynamics Report have no reason to be doubted, especially given their mission, and the overall length of the boat has no reason to be doubted either.
In my research (documented in the PowerPoint) I also came across the interesting observation that sails of the 41 for Freedom boats essentially were common in their shape. The sail planes, the sail cross section, and the sail planform all appear to be the same except for minor modifications. The location of the sail with respect to the missile compartment also seems to be within 1' of one another. The main difference is the waterline at which the sail planes were located. Each of the major classes seemed to have a different position. This, now allows a modeler to create an accurate sail and sail planes.
One last tidbit that came from the Dynamics Document was the propeller diameter. The diameter (assuming the later style prop) was 16', and it weighted 23,550lbs (found on page h-14).
So what is missing to create an accurate conversion of this boat? The deck fairing forward and aft of the immediate missile section would have to be done by eye. I think that this would not be too difficult, but it would be done only with the very grainy planform views, and pictures of the boat. The other item is the shape of the stern appendages. These once again can be estimated from the very grainy planform views, but the lower rudder length is cut off in these views. I do think, though, that one could make a good estimate of these, and the airfoils used are going to be a NACA 0016-22 range. Even, I would not be surprised if the sail used a NACA 00xx airfoil cross section.
Give me your thoughts. Make sure to take a look at the PowerPoint as well. It has a lot more picture analysis that would be hard to add here. I have added a teaser below, but there is a lot more in there.
Adam
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