Late War PT Boat
Late War PT Boat
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Modification to move hatch opening half an inch to the rear. This was shown in the video from MBH. I decided to do it this way rather than later.
Spacers used between siderails and hatch opening.
Hatch modification with spacer in place.
Spacer at rear of hatch.
Deck beams in place.
Deck beams at forward hatch opening.
New forward deck needed to be half an inch longer to allow for hatch modification.
Foredeck in place.
Deck hatch covering in place.
Foredeck and hatch.
Rear hatch cut line.
Side decking installed. You can never have too many weights or too many clamps.
Underside view of the finished deck and hatch assembly.
Finished hatch cut free of the deck assembly.
Hull awaiting correction. Nice stand provided by FMH.
Notice how the bow curves downward toward the water line.
Balsa block added to set the new deck line which is 3/8 of an inch higher.
Additional reinforcement midway down the cut line.
Here you can see the masking tape used to seal the opening at the cut line.
The hull is now ready for the fiberglass mat to be applied. Notice for this step, I am working in the garage.
Light weight mat in place. The smell is why I am in the garage. Don't want to upset the little lady.
I applied masking tape to minimize how much Bondo will have to be sanded away.
First layer of Bondo in place. Now I just have to wait until it is hardened before I start to sand.
This is the instruction manual that gives all the details for using the upgrade parts from MBH. It integrates the Dumas construction with the upgrades.
The spray rails needed to be reduced in thickness. I used my very old thickness sander to accomplish this. The size was reduced to 3/32 from 3/16.
Reference photos for towing eye.
On the right is the screw eye from MBH. On the left is my first attempt to replace the larger part. I decided I would end up breaking this at the solder joint.
I decided to modify a smaller eye hook which you can see at the center. This has a better chance to remain in one piece. I just trimmed it, closed the loop, and added solder.
Marking for the towing eye.
Eye in place.
Let's see, where did I put all those parts. Must be in here somewhere.
From the motors box I need 3 model 5045 12v motors from MACK Products.
Using the dimples already in the hull, makes it easier to get things lined up properly.
MACK Products strut. As you can see it is a very nice part but it does need some work to improve its function.
First step is to countersink the mounting holes.
The next steps are to sharpen the forward strut surface as well as to round over the baseplate edges.
Repeat 2 other times and after about 3 hours you have some nice struts ready to use.
Using a brass rod to mark the location for the strut attachment.
Now it's starting to look like something, right?
This is the bravery test. Just have to make sure the holes are in the right place. Believe me, I've drilled them in the WRONG place before on other hulls.
Orientation marks to make sure I get the plywood plates in the correct place.
Plates laminated into place with mat and resin.
Rudders and mounting blocks. These are resin parts.
First trial fit showed that the bottom of the blocks needed to be beveled so that the rudders would be vertical.
Notches cut in the bottom to help the Bondo to adhere to the block.
Rudder blocks in place. I marked them so that I could remember what went where.
Rudders in place. The next step will be to set up the linkages and servo.
I'm using wheel collars as the first part of holding the rudders in place.
Dumas rudder arms.
Soldering the pieces for the aileron linkage.
Linkage installed on rudder arm.
Now I just need to connect the servo to this linkage rod and I should be good to go.
After I cut holes in the mounting plate for the servo and switch, I slowly removed stock from each end until the plate settled in the hull at the correct height.
I used Bondo to fasten the plate in place. I have the servo linkage centered and tightened down for testing.
Check travel in both directions and all seems to be working well.
I noticed that there was a bit of flexing in the plate so I decided to add a strip of ply to the forward edge as a stiffener.
That took care of the flex. The rest of the plate will be used for mounting of the receiver and whatever else may be required.
First step, remove all of the equipment because there is going to be a lot of fiberglass dust generated.
I used the struts to locate the positions for the slots on the bottom of the hull. I started with a small bit and gradually increased the size of the holes. Finished size is 11/32.
Used the stuffing box to check the size of the holes.
Finished slots in what I fervently hope will be the correct place.
Center strut in place. I wish it could have been easier.
I used nylon locking nuts to bolt the strut in place.
Shaft enters the hull pretty much on center.
Here you can see the Plumbers Goop coming out around the mounting screw. This is great stuff but you have to work quickly.
After all that work I just had to see what it looked like. The propellers were balanced and sharpened by a friend of mine in Brisbane, Australia. His name is Rod Grimes. And he does a very good job.
I tack glued the stuffing box in place with superglue, then covered the opening with masking tape. Yes, I know resin will still leak out, but at least this will slow it down some.
Microballoon and resin mixture poured into place.
I made a slit in a piece of fiberglass mat and slipped it over the stuffing box and shaft. As these were large openings, I thought it best to reinforce this area.
Tape removed from the bottom of the hull and it came out pretty smooth.
Finished at last. Now I need to decide if I'm going to add a support to the front of the stuffing boxes. Still thinking about this.
Just trying to get an idea of what shaft length I should have. This type of thing is always trial and error.
Here you can see the Graupner and the MACK motors side by side. Except for the labeling, they seem identical. I will be using a Dumas coupling.
Taped up the openings and installed the drive cups on the 3 motors after I had ground a flat on each of the shafts. I used blue locktite on the set screws.
Finished shafts with couplings installed.
The first thing I did was drill some small holes all around the stuffing box. I did this from both the inside and the outside.
Next I connected the holes using a cut off wheel. Being careful not to damage the stuffing box.
Stuffing box removed and this is what was left.
Stuffing box is going to need a little TLC but it can be saved.
Not too bad. Just a few nicks and scratches but still useable.
View from inside.
This time I spent a while making sure that it was absolutely correct.
Preparing to pour the resin and microballoon mixture.
Port shaft completely reinstalled. Operates much better than it did before.
Here you can see one of the motors mounted to the sliding plywood plate. I used a piece of brass tubing to align the ends of the couplers.
This is the track that the plate will fit into and hopefully slide easily.
I decided to reinforce the glue joint of the rails on the sides of the motor mounts with wooden pins. I just wanted to make sure they would stay in place.
Pinned and ready for sanding. This pair is for the center motor. It is slightly different from the outboard mounts.
Mount in place in the hull. It will be fiberglassed into place with some mat and resin.
This is the MACK Products motor mount.
Here you can see all the motors mounted. Notice that the port motor has been shifted to compensate for the new alignment of the stuffing box correction which was needed to allow the shaft to spin freely.
Styrene sheet and center hatch ready to be joined.
I've applied a layer of epoxy and used a notched epoxy spreader which I got at West Marine to make sure I got a nice even coat. I also sanded the underside of the styrene.
When the epoxy was almost dry I used this roller to make sure everything was nice and smooth.
Templates provided by MBH.
Here is the thin sheet of plywood coated with epoxy ready to be joined to the styrene sheet.
Parts were covered with a piece of pressboard and then weighted.
Templates glued to styrene/plywood sheet.
Here you can see the changes between the two parts. The thickness of each part is the same.
These are the completed replacement parts. I weighed the original parts and compared the weight of the new parts. Overall there is a difference of 8 grams between the parts. The new parts are heavier by this amount. I will be attempting to save some w
I exchanged the thick Dumas plywood bulkheads for some 1/16 plywood. You can also see if you look closely a strip of wood used to keep the side of the cabin flush with the edge of the hatch.
Center bulkhead is faced on both sides with thin styrene.
Cabin roof temporarily in place just to see how things are fitting.
Roof clamped into place.
Forward center brace in place. Just need to add the forward cabin walls.
Going to have to do a lot of sanding to get all the edges nice and flush.
Dumas parts replaced with much lighter ones.
Test fit looks good.
Thin styrene added to the parts.
Forward windshield needs to be fitted and glued in place.
Dumas parts laid out for transfer on the styrene/plywood sheet.
Parts cut out and ready for assembly.
Temporary spacer blocks used to make sure the center support was parallel to the front of the cabin.
Test fitting to the center hatch.
I added temporary side rails to make sure the cabin was centered correctly.
Roof glued into place.
Going to need a lot of sanding to round the corners of the cabin at the roof line.
Drip edge added.
First test window frame proved to be correct. Now all I have to do is make a few more.
Easier to make single corners at first, then allow to dry.
All the corners joined together.
Steel rule used to make sure everything lines up. We hope.
Jig that will be used to form the styrene strip to the proper shape to be added to the cabin roof.
I put the styrene strip into some very hot water for several minutes and then clamped it in the jig. We will see tomorrow if it holds its shape.
Drip edge above window frame.
Flag box to be mounted later to the front bulkhead of the day cabin.
After I removed the styrene piece from the clamping jig I found it a lot easier to attach to the roof line of the day cabin.
Here you can see the difference in the thickness of turret walls.
I used my oscillating spindle sander. The bad thing is I had to hold the part in my hand and this is not the safest thing.
MBH provides templates so that you can correctly orient the turrets.
This is the key mark.
It is going to take some fitting and sanding but it will fit in the end, I hope.
This is the jig I used to help make parts that will be added to the rear of the day cabin.
I needed to construct a small part that needed to exactly fit the diameter of the tube seen here.
The part was built oversized and trimmed to fit.
If I told you how many hours went into this part you would be amazed. The hard part was fitting the base. There are 2 of these on the rear of the day cabin.
I just need to do a little sanding and add the final piece and then they are ready for install.
This is the pile of parts that were discarded during the build. If I knew how to use a lathe I'm sure it would have taken only a few minutes to produce.
Details added to cabin roof.
I made this jig to bend the brass tubing for the conduit on the day cabin roof.
I heated the brass rod to red hot and allowed it to cool.
Trial fit to the cabin roof.
Another jig used for the bending of the conduit on the rear bulkhead of the day cabin.
Setting things up just to see how the fit goes.
Here you can see the joint between the two structures. I know some would say just slap some filler in there. But the gap is rather large.
The fit around the cabin roof is not as bad but still it will require some work.
In the first step I used a piece of styrene to close the gap between the parts.
I then added a second layer of styrene over the first so that it would be even with the cabin sides. I also extended the drip rail with a tiny piece of styrene.
I have no idea what I am going to do about this curved section yet. Like I said, I just do not do this part very well. Filler? Styrene scrap first? I am going to think on it some.
Sides in place, ready for cross members.
Notice the cutout for the turent on the upper right.
Here I modified the framework to the correct outline. No cutout for the turent.
There is a crown in the top of the hatch. I decided to make this by adding four small pieces of brass rod.
Top glued in place.
Note stain on the piece.
The reason there is no cutout in the hatch is because the turent has the cutout. I'm using this to get the correct angle for marking the cut lines.
I don't mind saying I was sweating bullets over this. I had one chance to get it right. I would have been bad to have miss cut this.
This is the framework for the deck area between the day cabin and the engine hatch.
I enclosed the bottom part of the turent with some styrene sheet.
Deck area between the day cabin and the engine hatch.
Air scoop parts from MBH.
Here you can see the radius at the corner of the molded air scoop. This should be a nice square corner but it's hard to get those in molded pieces.
The first step was to determine what part was actually square and how much did I have to trim off to get to the square part. I used styrene so that I could mark a line on the part.
Once I had a cut line I removed the styrene strips and trimmed the part to the line. Then I added styrene to the inside to give me a lip so that I could glue a new styrene edge all around the part.
The styrene strip is just slightly proud of the surface of the scoop. I should be able to sand it down flush with the surface.
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