PBR Mark 1 River Patrol Boat by Thistle17 - FINISHED - Scale 1:6 - Model Shipwright Guild WNY

[Thistle17]

Yes Mark thanks it slipped my mind. I will repeat for all these drawings are more or less renditions of the major components and as such have no measurements, cross sections etc. On the other hand the Navy drawings are quite detailed including all dimensions and detailed cross sections that in some cases even define the bolt hole patterns and the like. What has confounded us a bit is to decide what vintage of the model we would undertake. As we have numerous photos from on line ( that are in the field or state side) and other sources, including Patriots Point excellent photos, it has almost become a "TMI"(too much info) situation. So we have leaned more to the "as built" configuration.

 

Now the build posture has been from the outset, to construct a waterline model that will be placed in a diorama like setting at the museum where we meet. The setting will be a dockside setting with all the scale artifacts that the museum has collected. With that framing the model will be as authentic as we can make it "topside" but will not incorporate "undercarriage" detail that cannot be seen by the public.

 

I have related this before I just thought for new viewers it would be beneficial to repeat once again.

 

Joe

[Thistle17]

Shown below is a typical gun tub for the model. It is the best close up image we can find. Now I think this is mounted on a MK II but as best we can tell from the drawings we have it appears identical. Combined with our drawing file and this photo we are going to fabricate the gun tub as follows. We have produced 2 very accurately diameter discs out of 3/4' MDF that will form the top and bottom of a form. The center alignment hole has been accurately placed and will help in alignment when we bolt the 2 forms together. Now the overall height of the gun tub to scale is 3 1/8" inches tall. To fashion the gun tub we will sandwich in between the top and bottom discs separators (of slightly smaller diameter than the two discs of 7" diameter) to achieve the 3 1/8" height. The assembly will be bolted together. The two disc edges will be refined so as to limit the possibility of glue adhesion. One thirty second (1/32") basswood will be machined into staves and mounted to the form. The staves will be edge glued. Clamping bands can be used to achieve conformal shaping of the flat stock onto the form. The overall outside diameter is 7 1/8" Hence a second layer of 1/32" will be repeated.

 

The gun tub rings can be fabricated in a number of ways but the preferred method is to have them laser etched from either suitable thickness plywood or laser board.

 

We think this will work and will be working this over the next week.

 

In looking at the gunner in the photo one cannot help but wonder about his hearing problems as a result of his placement. Did these guys sacrifice themselves or what???

 

Joe

 

 

 

EPSON039.rot (2).pdf

Edited February 11, 2020 by Thistle17

[Thistle17]

We finally got around to fabricating the gun form shown in the picture attached. The form is 7" in diameter and 3 1/8" high. We did experiment with alternate methods of creating the tub surround i.e. a veneer wrap, thicker staves and the like but finally reverted to the original thinking of two layers of 1/32 staves with the outer staves offset from the joint area of the first layer. This is now being fabricated off site. In addition the fabricator has design processing capability and access to laser fabrication to make the tub flanges (rings) and as he says with the bolt patterns included. A test fit of the form indicates we will have no problems with fit into the existing support ring of the model.

 

Joe

 

 

Edited February 11, 2020 by Thistle17

[Thistle17]

I handed off the form to Bill our resident expert at computer design and who also has access to laser etching and to my utter surprise he produced the gun tub in an amazing short time! And to add to the surprise he elected to use styrene sheet  for the tub surround dispensing with a good deal of sanding and filling with the stave approach. In addition he was able to add the bolt holes for further realism. I am sure to many of you that would have been a logical material choice. It certainly was for Bill as his Civil War scratch models employ this material.

 

The challenge now is to outfit the tub with the inner mounts, back rest, ammo cache, spent ammo receiver etc. Unfortunately we only have the Maryland Silver rendering of the tub inner details so there will have to be some "poetic license" determination of dimensions and placement of elements mentioned. We do have the 50 Caliber scale guns so that will be of some help.

 

Joe

EPSON044.PDF

Edited February 17, 2020 by Thistle17

[Thistle17]

Our last posting made the press just about the time we all became accutely aware of the emerging pandemic. Both seem like a long time ago. In the intervening time little was done on the build as priorities turned elsewhere. Well just last week we felt comfortable enough to restart the project with a priority on the forward gun deck and tub. With the on again, off again mode we were in we quickly realized the gun tub diameter was incorrect. Somehow in our haste we neglected to understand its doameter until a composite sketch was drawn utilizing the Navy and Maryland Silver drawings. Sadly the earlier tub is just about 1 1/2 inches in diammeter too small.

 

Not shown here is the new form constructed, as before, to aid the new tub build.The new tub is presently under construction utilizing .040 styrene. Once we are satisfied with the result it will go off to our Corel Draw guru to use as a guide to update the file for a rerun of the laser machining of the tub flanges. I am told it should be a straight forward update and we should be back in stride to complete the deck soon.

 

I had quiered a number of MSW folk on conformal coating for the hull once we are finished with this phase. All suggest use of epoxy resin without glass fiber to fair the hull. That will be the next phase once past the tub detail.

 

Joe

[Thistle17]

Pictorially the difference between the earlier gun tub and the soon to be new one (just the form) can be seen in the attached photo. This time I made a full form out of stacked MDF scrap. The glued up assembly was bandsawed to near diameter and then sanded on the shop disc sander which has a convenient way to make perfectly round elements. The new form is 3 3/8 inches high and sits on the sub deck. It will be wrapped in .030 polystyrene. Luckily one of our group had 3 foot long polystyrene stock so there will be just one joint. I am thinking of wrapping the upper part of the tub once again with .020 stock just from the tub top to the upper deck level and offset from the layer joint beneath. This should give the completed tub more integrity and it will also serve to place the bolt ring which will abutt to its lower limit. Again as soon as I finish this tub it will be handed off to have the cap and bolt ring design modified and sent off to our laser machinist. Both rings will be made from 3/16 inch ply wood.

 

Joe

 

[Thistle17]

As we delve into references for the gun tub innards we find a number of different configurations for the gun mounts, the inner catch tubs and even the ammo feed elements. One can only suspect that there was quite a bit on "in field" retros and contrivences. Shown below in order is the Patriots Point forward gun tub followed by what is obviously a in field shot. In the latter one note the 50 caliber shell trays and the relative gun spacing. The tubular frame overhead here is likely weather shielding framework. In  looking at the multiple pictorial sources one has to assume that it does not matter which side of the weapon shells are fed into the chamber. Not having a difinite reference we have decided to mimic the Patriots Point configuration.

 

[Thistle17]

The gun tub is turning out to be quite a guess work project. In a recent conversation with a naval officier I asked why we were unable to secure the gun tub drawings. He reminded me that the Navy Bureau we dealt with held a few drawings back. Given that it is related to armament we suspect they may have erred on the side of caution. So for whatever the reason the construction of the tub innards has become a head scratcher.

 

With the aid of more photos The tub structure was assembled and a cardboard model of the tub shell casing and gun mount steel works was constructed. Admittedly it is crude but does seem to give an elemental sense of the tub innards. As there are two of these the cardboard model has been taped together and will be taken apart enabling the fabrication of  both. Basswood is likely the material of choice. Further elements will be added to replicate those shown in the photo such as the cross members, gun trunions, sheilding and the like.The second photo while depicting the actual shell catch tray reasonably well it marginally shows its internal placement.

 

Joe

[Roger Pellett]

For many years, the Navy was managed by the “Bureau System.”  Up until 1966 ship construction involved at least two bureaus- The Bureau of Ships and the Bureau of Ordnance, and like many bureaucratic organizations each defended their turf.

 

In 1966, the bureaus were reorganized into commands, the Bureau of Ships becoming the Naval Ships Systems Command, but the general idea stayed the same.  Each organization involved in designing a ship worked under a formal document defining their area of responsibility.  Our slang term for this was the “ball definer,” in other words, “Who’se  got the ball.”

 

This organizational approach would have affected the Navy’s filing system and the information appearing on their drawings.  If NAVSHIPS built the gun tub and NAVORD outfitted it details would be shown on drawings produced by two different organizations.

 

Roger

[Thistle17]

Thank you Roger for that insight. It certainly makes sense. Unfortunately our contacts in the Navy are no longer available to us as we did try, pre pandemic, to reach them. So we muddle on.

 

In the last few days I have attempted to fashion the tub out of 3/64" basswood and it was a huge disappointment. The height of the "catch or holding wells" was guesstimated to be about 2 1/2". Pre bending the basswood along its grain turned out to be a mistake. At that thickness the curved side acts somewhat as an archer's bow. The resulting tension distorts the assembly to such a great degree that it is a nightmare to assemble and the end result is unacceptable. I am now driven back to polystyrene as the preferred material.

 

If at first you fail try, try again seems to be my mantra these days.

 

Joe

[druxey]

One should be able to wet-bend 3/64" basswood easily, with the grain at right angles to the diameter.

[Thistle17]

Yes David you point out what I should have told myself. You would think I would learn from my past experiences. Admittedtedly this is not an endeared project for me. Out of duty and a sense of 'get er done' I am in a forced function mode. Again you would think I know better.

Joe

[Thistle17]

You may have heard that RBG never said "umm" before she spoke. She always thought and then spoke. Well had I paused and followed good sense I would have done so on the catch assemblies and construted them as druxey suggested. So before I went for the polystyrene approach. I manged to build up the 2 trays as suggested. They assembled quite easily and have no distortion due to built in wood fiber stress..

Joe

[Thistle17]

Dry fit prior to final assembly of the inner trays came out reasonably well owing to the lack of structure stresses of the new substructures. The back rest has also been dry fitted. Without dimensions or scale drawings the juxtaposition of the back rest is almost correct when the photos we were given are compared. The support brackets will have to be adjusted to accomadate the difference.

 

We have had a bit of luck as one of the members working on the model found in his archive of photos an oblique "head on" shot of the gun tub. Much to our surprise there is an added plate in the forward part of the gun tub, at rim level, that supports all the gun brackets and cradles for the 50 calibers. It is just behind the armament plate. We could not clearly see this in any of the other photos nor do any drawings even hint at this.

 

This week we will be testing gun placement to determine the plate size and bracket locations and from then on I think we will be able to move forward with more certainty.

 

Joe

[mtaylor]

That plate looks like a field upgrade, Joe.  Very similar to what we did for the gunners in the CH-53's.  On the window side it was riveted to the fuselage, on the door side, it riveted to the gun mount.

 

As a field upgrade there probably isn't any "official" drawings. Probably just some sketches done by the metal shop so they could make what they needed and also replacements.

[Thistle17]

Mark I am coming around to the same conclusions about in service versus "as delivered and subsequent field changes". Who would know better than the end users of what worked or needed refinement!

 

After I submitted my entry last evening I happened to recall that I had a cell phone picture of a Tamiya PBR. Sure enough it is configured as the Patriots Point gun tub. Just a bit more evidence that makes us feel more at ease about our build configuration.

Joe

[Roger Pellett]

Joe,

 

Maybe you have already answered this question but do you have access to Norman Friedman’s book Small Combatants?  If not, it has a lot of material about PBR’s.  It’s one of his design series about US Navy Ships.  It’s out of print and expensive but if you can get it via inter-library loan it might be worthwhile.

 

It has a lot of large photos.  While these are too grainy due to book publication choices to show fine detail, a determined researcher in your group could probably track down high resolution copies.

 

like any small craft in combat zones, these pictures show many field modifications.  I’m sure that these were made on the spot by crews just trying to get the best of a resourceful enemy.  No one was waiting for a NAVSHIPS bureaucrat to issue a SHIPALT.

 

Roger

[Roger Pellett]

The pictures taken in the combat zone show a large light attached to the gun tub that would swivel with the guns.  I don’t know whether this is a night vision light or a conventional spot light.

[mtaylor]

4 hours ago, Roger Pellett said:

The pictures taken in the combat zone show a large light attached to the gun tub that would swivel with the guns.  I don’t know whether this is a night vision light or a conventional spot light.

 

I don't recall having "night vision" available to us in Vietnam.   Possible there was.

[Roger Pellett]

You certainly know a lot more about this than I do, so it’s probably a spotlight.

[Thistle17]

Well Roger my first attempts to locate a copy of the book have failed. It is available on various sources for nearly $100. A bit pricey for our budget. Our county library system does not have it either. So for the moment that reference is not available to us.

 

And yes Mark it is a search light.

 

Last night I "tacked in" a plate that seemed to be of the correct size but after sizing it up against one of the scale 50 caliber guns it is a bit too wide to accomadate the outer support brackets so they end up correctly positioned in relation to the tub rim flange. So out it comes to be modified, reinstalled and readied for the twin gun try out later this week which is being done by another modeler.

 

This "by guess and by gosh" way of modeling is a bit frustrating I must say. We are striving for a fairly accurate rendition but with such scant information at the detail level some interpretation is creeping in.

 

Joe

[Thistle17]

We have all heard that a picture is worth a 1000 words But to some extent that is failing us and driving some do overs. This has been the case as we advance through the elements of the gun tub. The latest do over has been a modification of the inner tubs/that either hold ammo or catch spent shells. I am in the process of modifing them to make the width about 1/2 inch narrower. The left hand unit has been reduced. What drove this is a more detailed study of the machine gun trunion/mounts (see entry of 9/27). They are the elements that protrude above the tub flange. In our latest study we find that the model guns we have do not mount to the shaft through the gun body. The guns rest in a carrier and that carrier has flanges that support pivot points for both guns. The gun mounts must be spaced to accomadate the trays. We arrived at this by scaling one of the pictures so as the gun profile was the same as our 1/6 scale guns. 

 

Had we left the inner tubs at the original width the spacing for the supports in relation to the inner tubs would have been way off. That is probably not very clear possibly this will show up when we get closer to final sub assembly.

 

Joe

Edited September 21, 2021 by Thistle17

[Thistle17]

We have advanced a bit farther in the build of the gun tub. Jim our project manager has taken the tub which was outfitted permanently with the modified inner catch/ammo trays. He has been working on the 50 caliber gun carriages. We continue to glean tid bits of information about the Patriots Point PBR. We have been told of late that the guns are not real but apperantely resin cast. No wonder they don't look exactly like our 1:6 scale units.

 

Here is a mockup of the tub with guns.We will be removing the handles aft as they were not "handled" from that point. I would add that the tub now easily supports the scale figures that are planned for the model.

 

Joe

 

[Thistle17]

 

I viewed progress on the gun tub carriages and beginnings of the frameworks for mounting the carriages and subsequently for the guns. At this point we have a question for anyone out there that served on a vessel like this. In studying the geometry of the mounting we have come to the conclusion that the carraiges were mounted to the swivel frameworks, not the guns. Our study of the photos we have does not reveal to us how the guns were secured to0 the carriages.We have to assume that the guns were easily attached and removed so how was carriage securing dealt with?

 

While the gun tub work progresses I have decided to start the final fairing of the hull. It has been a hard lesson in construction as we used full bass wood sheet of 2 and 3 inches to "plank" the hull. Even though the bulkheads were fairly benign in terms of contour the result was that the hull has a number of valleys and/or end sheet butting that needs a good deal of fill as well as fairing. Although I have a lead on a product used in fiberglass hull fairing I have been reluctant to buy even a quart to experiment with. In the mean time I have resorted to our standby product Rage, Easy Sand. Its one limiting behavior is that it has an open time of just about 5 minutes so one has to work quickly and in small batches. It is advetised as sandable in just 15 minutes but I find the sanding gums up the sandpaper quicker than if one waits a bit longer. Nitro Stan glazing compound is being used to fill in the smaller imperfections but as related earlier in tends to shrink so multiple applications are needed.

 

 

[mtaylor]

Joe, 

A quick Google got me these with a lot more hits.  Maybe it's starting place.  I used ".50 cal machine gun mount for PBR".  Hope it helps or sends you in the right direction.

 

https://www.eugeneleeslover.com/USNAVY/COASTAL-RIVERINE-CRAFT-ARMAMENT.html

https://nara.getarchive.net/media/a-close-up-view-of-twin-mounted-m-2-50-caliber-machine-guns-on-a-pbr-mark-2-d9fa9b

 

As I recall.... and memory may not be so hot, the gun was mounted to the mount using a pin-lock bolt.  The pin to release the bolt had a ring and had to be pulled first (spring loaded).  Once the bolt was pulled the gun came off.  Mounting was the reverse and usually required a bit of acrobatics to get the bolt in.

[Thistle17]

Mark your second reference iis quite helpful and more so supported by your text. Thank you.

Joe

[mtaylor]

I'm happy that the link is useful and the description.  I realize that A/C mounts were somewhat but not entirely different than boat mounts.   I only wish I still had my album from 'Nam.  Had a lot of photos of things like this.

[Thistle17]

Thanks Mark, we move on.

 

The hull fairing is nearly complete but still remains tedious. I hated automotive body work in my younger years and this project is no different. Embarrassement  of a poor result is all that drives me on.

 

Took a break from that work and made the elements of the rub strib for the hull at deck level yesterday. After finding nothing at the hobby shop of suitable form I decided to make them. Using my 3/8 inch beading bit for my router I machined 3/8 basswood stock with the bit raised to just the bead height. (A smaller radius one is shown). I machined both edges to a bead on the stock and then ripped them at the Byrnes saw. Working with 24 inch stock I will have to join elements. A scarf joint should hide the junction. I haven't got a good close up picture of the rub rail so it may be after some searching the profile will need further hand work to comply.

Joe

[Jorge Diaz O]

Fantastic!!!!

[Thistle17]

&*%#! I found a photo of the hull that didn't pixelate too much that displays the rub rail. That is the good news. The bad news is that my interpretation was wrong. I had assumed a more modern style but the picture that is shown in page 1 of this build log exhibits a much different rail that is proud at the stern and through midship but then intergrates itself into a splayed upper bow. I picked up some tapered balsa made for model airplane struts but in experimenting with it I have my doubts that it will suffice. Back to the drawing board!

Joe