Scratch Build project SM U-23 Class World war one U-boote. Zero Bubble model design.

[Davidh]

Thanks Rob, Its good to see someone likes it.


At this point the U-23 is ready for early testing. At the moment the 2.4 Ghz cylinder isn't ready just yet so I am reverting back to using my old ZB-2 cylinder. (Twin shaft, twin motor) discontinued not that there were many orders. The distance between shafts is constant between both cylinders and length is virtually the same so that fitting between the two shouldn't be a problem. As mentioned in the previous post I have used foam as a means of securing the cylinder and wedging it in place. I have placed a good amount of foam fore and aft and then started placing lead sinkers in the locations that I typically would find these sinkers in my other boats. The box keel at the bottom of this hull is really use full for this as it allows me to place lead underneath the cylinder and ballast tank, something that wasn't easy with my nuclear boats.

At this point I did think about the cubic capacity of the ballast tank and if it would be enough to bring her down satisfactorily. I had though that when making it maybe I should have made it slightly bigger. I could always swap it out. Then again I want a boat that will only just get close to neutral buoyancy and not go beyond it. I've never been good at the maths.



Initial tests showed that she was slightly stern heavy, but overall a little high in the water, certainly above her surface waterline . So do I add more lead or increase the amount of Foam? I would do a mixture of both but found that with cylinder and Battery added she came close to surface trim. The initial dive test showed that she needed all the ballast tank water she could get to submerge and the slight stern heavy was accentuated somewhat. More trimming with foam and redistribution of lead weight.



As seen at this point not all the painting had been completed yet and some of the surface details hadn't been installed either. I intend on making the Radio masts later and having them as detachable masts and stays. At this point I was thinking, how you get the boat to sit as high as you can and yet easily dive to a nice neutral bouyancy? Eventually after some fiddling all afternoon I managed to get her to sit with the conning tower above the water, it is clear that the tank could probably be just a little bit bigger. No big drama, just a redistribution and and a bigger tank, probably only needs to be about 20% bigger.




The props have been effective but need a little time to develop the thrust, she doesn't move away instantly. The rudder has some authority and the push rod mechanism on the top is actually quite use full when seeing what the rudder is doing and that it is doing. I managed to drag my son away from his PS4 long enough to get his go-pro charged and ready for some underwater action. The temperature on the day being a nice 28 degrees and even the water being quite warm for this rather moderate summer. It would be good to get some clear underwater shots a view her behaviour from underwater.



The underwater realm and a really good lens shown up imperfections in a light that you just don't quite get on the surface. Here the torpedo tube doors haven't been installed yet and the Z cut needs some looking into. The bow planes are fixed. I haven never made them operational on any of my models. I probably should. One of the things that I found was that the stern planes were not as effective as I would have liked. The only made slight influence when at speed.



I have know that my pool isn't ideal. It is a salt chlorine pool and I think that Rio in the concrete doesn't help. But its all I got and there are times when the reception is OK and other times it's glitchy. I decided to increase the stern plane surface area by adding clear plastic strips that above the surface of the water are effectively invisible, but under the surface are noticeable.










The radio masts were a distinctive feature of these early U-boats. They made the boat very vulnerable to the slow flying Biplanes of the age and couldn't as a result, dive quickly. I think they look great and mostly leave them on which is most un-scale like when diving but, what the heck. The masts are made of Skewer stick given a coat of resin and paint and the wire is fine gauge wire. You just have to be care full when you haul the boat out of the water that you don't accidentally pull the wire or get tangled somehow in it.



As you can see here the bow it a little high. I haven't made a decision on doing a new improved Ballast tank, I don't have the time at the moment but will consider it in the future.



Once I get some of the bugs sorted out she will be a really nice yet quirky boat. I wondered whether the traditional hull type construction would make her want to plane up towards the surface at speed but this hasn't happened, (not that she's fast, she ain't the Papa) What I have found is that when she dives and the decks are awash the very bow is still above surface and it messes a little with you sense of level.
She looks fantastic with just a little bow ripple on the surface. I am glad that i built her and will find that she will keep me on my toes as I slowly tweak her.



Zero bubble line up, (mostly) spot the odd one out, hull shape, scale and about 60 years...


David H

[rwtdiver]

Hello all,

The stern is mostly done, all the components are in place, the rudder and the prop shaft all turn. Now starting to look at the internals and the arrangement of the all the internal components and systems. As with all my boats I use a Ballast system that is well known particularly in the UK and that is what is (I believe ) commonly known as the "Sheerline' system. This system uses a pressurized ballast tank where water is forced into a tank with no escape for the air. The pressure is maintained and then used to force the water out. My cylinders use a simple 12v water pump that is externally mounted with a separate isolated Ballast tank that is as far as I know an Australian modification. ( All other designs on the market that I know have the pump internally mounted to an internal tank.)

U-23 will have the Ballast tank slightly forward of the C of G. This is unavoidable because of the amount of space needed for the drive shafts and push rod linkages pushing the Cylinder forward and then the Ballast tank forward as well. I am not concerned as this was a concern on the PAPA and that boat performs beautifully. Forward of the Ballast tank will be the 12 v SLA and then foam. Initially I played around with positioning and location of parts and systems with an eye to looking at making sure that I could get access to everything but also thinking about trim and buoyancy.

Here I am still building the insides of the ZB-1/2. This one will feature a Ghz receiver set up.




I haven't set up the push rod connections yet....



I usually make my Ballast tanks out of PVC pipe. From the start I was kind of entertaining the idea of creating a period type ballast tank and making one out of Brass sheet with soldered sides. Kind of make it look like it was made in 1913, however the effort and detail required was out of my league and time. So I simply went ahead with the PVC pipe. I wanted to heat up the pipe and make it a similar profile to the hull shape with a reasonably flat top section, this would mean I could produce a wider large capacity and yet as a result, shorten the length of the tank to bring it closer to the C of G. However in doing so I would not be able to use a standard PVC end cap. I would have to fabricate one and make it stand up to pressure. This caused a drama as it kept popping off under pressure. I then looked around and found an old Acrylic pipe from one of my old Cylinders form years ago and decided to make a Ballast tank out of that. This is nothing new, acrylic ballast tanks work well ,just make sure they don't crack.






End cap with curved pick up. The curve comes out of my deduction that an abrupt change in direction may slow down the rate of flow? I cut out one Baffle for the middle. And then another end cap at the other end with a horizontal bar on either end to bolt down to an Aluminium cross piece at either end.



Middle baffle small hole at bottom for flow in between chambers and gap at top for air movement.



Aluminium cross braces that the Ballast tank will bolt down to. Yet to be glassed into place.




This photo shows the Ballast tank installed. I carved a chunk of surfboard foam by putting a hole in to big enough for a 12v battery. Wow a clean desk....






The ZB Cylinder has been secured in place by being wedged between buoyancy foam around the sides and a rubber band strapped over the top. The next major steps are mainly cosmetic and comes down to the fun part, spraying and painting. These U -Boats were mostly two tone, two shades of Grey. There was also the light tan color of the Canvas. To get an idea of what these colours where I looked at the colour scheme of the ' Das Werke U9 " kit. Hey , they may as well be use full sometime. I decided to go with these colours.



Some of the masking tape is still in place, I have found that the primer that I use is almost exactly the same as the grey used on the lower hull. I also like the sheen...



I am really happy with how the canvas looks. The 2.4 Ghz antenna will come out the top of the Periscope. Deck two tone was reasonably straight forward to apply.



I have decided to make my boat the U-24. This boat survived the war and wasn't broken up until 1921. I like the rust. I have yet to glue in the Torpedo tube doors.









I should be working on the making the gap between the forward and main hull a bit better. Bow planes are fixed.

Next installment, in the water!

David,

I have really enjoyed following your build from day one! To see it come from a bucket of resin and fiber glass to a full up submarine has been a real learning process for me. I am looking forward to see how well it performs in the water. Nice looking boat, in particular the final photo posted. You should be very proud of your accomplishment with this scratch build.

Thank you for sharing the build with us, and we will stand by for the sea trials!

Rob
"Firemen can stand the heat"

[Davidh]

Hello all,

The stern is mostly done, all the components are in place, the rudder and the prop shaft all turn. Now starting to look at the internals and the arrangement of the all the internal components and systems. As with all my boats I use a Ballast system that is well known particularly in the UK and that is what is (I believe ) commonly known as the "Sheerline' system. This system uses a pressurized ballast tank where water is forced into a tank with no escape for the air. The pressure is maintained and then used to force the water out. My cylinders use a simple 12v water pump that is externally mounted with a separate isolated Ballast tank that is as far as I know an Australian modification. ( All other designs on the market that I know have the pump internally mounted to an internal tank.)

U-23 will have the Ballast tank slightly forward of the C of G. This is unavoidable because of the amount of space needed for the drive shafts and push rod linkages pushing the Cylinder forward and then the Ballast tank forward as well. I am not concerned as this was a concern on the PAPA and that boat performs beautifully. Forward of the Ballast tank will be the 12 v SLA and then foam. Initially I played around with positioning and location of parts and systems with an eye to looking at making sure that I could get access to everything but also thinking about trim and buoyancy.

Here I am still building the insides of the ZB-1/2. This one will feature a Ghz receiver set up.




I haven't set up the push rod connections yet....



I usually make my Ballast tanks out of PVC pipe. From the start I was kind of entertaining the idea of creating a period type ballast tank and making one out of Brass sheet with soldered sides. Kind of make it look like it was made in 1913, however the effort and detail required was out of my league and time. So I simply went ahead with the PVC pipe. I wanted to heat up the pipe and make it a similar profile to the hull shape with a reasonably flat top section, this would mean I could produce a wider large capacity and yet as a result, shorten the length of the tank to bring it closer to the C of G. However in doing so I would not be able to use a standard PVC end cap. I would have to fabricate one and make it stand up to pressure. This caused a drama as it kept popping off under pressure. I then looked around and found an old Acrylic pipe from one of my old Cylinders form years ago and decided to make a Ballast tank out of that. This is nothing new, acrylic ballast tanks work well ,just make sure they don't crack.






End cap with curved pick up. The curve comes out of my deduction that an abrupt change in direction may slow down the rate of flow? I cut out one Baffle for the middle. And then another end cap at the other end with a horizontal bar on either end to bolt down to an Aluminium cross piece at either end.



Middle baffle small hole at bottom for flow in between chambers and gap at top for air movement.



Aluminium cross braces that the Ballast tank will bolt down to. Yet to be glassed into place.




This photo shows the Ballast tank installed. I carved a chunk of surfboard foam by putting a hole in to big enough for a 12v battery. Wow a clean desk....






The ZB Cylinder has been secured in place by being wedged between buoyancy foam around the sides and a rubber band strapped over the top. The next major steps are mainly cosmetic and comes down to the fun part, spraying and painting. These U -Boats were mostly two tone, two shades of Grey. There was also the light tan color of the Canvas. To get an idea of what these colours where I looked at the colour scheme of the ' Das Werke U9 " kit. Hey , they may as well be use full sometime. I decided to go with these colours.



Some of the masking tape is still in place, I have found that the primer that I use is almost exactly the same as the grey used on the lower hull. I also like the sheen...



I am really happy with how the canvas looks. The 2.4 Ghz antenna will come out the top of the Periscope. Deck two tone was reasonably straight forward to apply.



I have decided to make my boat the U-24. This boat survived the war and wasn't broken up until 1921. I like the rust. I have yet to glue in the Torpedo tube doors.









I should be working on the making the gap between the forward and main hull a bit better. Bow planes are fixed.

Next installment, in the water!

[Davidh]

Hello all,

The next step was to glue down the top stern section to the lower stern main hull. Once the dummy push rod connection had been mounted in place and then glues to the brass shaft that protrudes up through the center. Gluing the two halve together at the very end would allow the whole Z cut assembly to finally work and fit together. Once glued I would then mark out where the gut along the back top hull would occur. This would be just up from the start of the raised stern section, but far enough back to allow for good access to all the internal linkages and connections. It was just a case of filler and sanding along the waterline. I would re scribe the part line later.



Ongoing alignment, filling and sanding.




At this point I decided to work on the ballast hull vents. I have virtually no information on the location of Ballast tank vents on pre-world war one U-boats. As a result I have effectively had to guess what these vents look like and where. I have looked at photos of washed up U-boats on the English coast line and such however have only had fleeting references to where these vents may be. As a result, the placing of these vents may very well be out and this is the reason why I didn't scribe any vent detail into the hull masters.




I went with long vents along the sides of the keel and will drill small holes in the bottom of the Keel as this is where water will undoubtedly pool.



Back to the stern, I now created the brass push rod horn for the horizontal plane. This brass rod simply fits between the two planes and is uninterrupted. (yes!) I cut out two small brass sleeves to were glued into the sides of the hull to give support to the shaft and make sure that over time it does not wear into a larger hole. I cut out a small rectangular piece of 2 mm thick brass sheet to make the horn. Drilled the appropriate holes and like the rudder horn, soldered it in place and painted over. The clevice will be a plastic one.



Above the stern planes is the brass push rod for the rudder. The dummy brass push rods are evident sticking out the front of the cut. One 3 mm shaft is in place. The Sleeves have been glassed over.



Brass sleeves about to be glassed in place.



The rest of the stern section is pretty easy and just external features. The stern plane guards needed sanding and then filling, sanding and then the shaft brackets also needed the treatment.The brass shaft for the stern planes stopped just short of the outside of the plane as the guard would stick into the plane just a mm or two.




The propellers were given a coat of brass enamel.



Still more fine filling and sanding to be done especially around the joint between the top and bottom hull halves, but getting there.



I will be giving a coat of a Matt finish, here the stern is seen with a still wet coat of primer. This primer is actually very close to the actual colour used on these U-Boats.

[Davidh]

Hello all,

The stern of this boat would feature more parts that would be the case on my nuclear boats. Glands, brackets and guards are no usually features that adorn the more modern Soviet Nuclear boats. One of the first things that I needed to do was to drill out the location of the shaft exits. I had determined these positions way back when building the original masters and had created divits in the the sides of the hull where the shaft would exit. I used a template to make sure that these holes would line up a shaft exactly to the shaft out puts on a ZB-2 or ZB 1/2. I simply took a drill and then drilled out these exits and with a fine file made the holes just a little bigger.



The shaft exit points will feature embedded brass shafts that will be glassed down at the transition point between the inside and outside of the hull but wont extend through the gland as such. I needed to use a small file to widen the area for this shaft tube to be fitted. As can be seen the location for the stern planes and the relevant shaft is already in place. These will also feature small brass shafts to reinforce their position and stop ware on the hull wall.



The first bit of stern hardware to be glue in place however would be the Rudder and then rudder post at the bottom of the transom. This was a small cast urethane piece that holds the rudder in position. (It sits in the step in the below pic) I needed to then start sanding around the rudder support area and also make sure that the rudder itself is presentable. The rudder shaft would extend up through the top of the upper hull just before the raised deck starts. It will be terminated in a push rod mechanism that was used on pre-war U boats. This mechanism has been discussed earlier. By installing this section I could then glue the top Upper hull to the lower stern section and complete the hatch arrangement for the whole boat.

The Rudder would be secured by a small brass tube that sits just above the top of the rudder (seen below) and secures the shaft in place before it extends up to the push rod system . In between these two components there is a push rod horn that is made of brass and is soldered in place and this is the actual push rod mechanism of the rudder. The above deck one is purely cosmetic.



Here you can see the rudder post in place with holes directly aligned for Rudder shaft. Stern glands in place. Divits and holes can be seen for the stern plane guards , hole for the stern plane and the locations of the two attachment points for the shaft brackets.




Once all this was done all I needed to do was to glue the rudder in position. Tricky to glue as you need superglue in some parts of the shaft and rudder and not others. Superglue along the main section of rudder and a trough of lanolin at the bottom of the rudder. I had earlier made up the brass push rod. This was soldered into position and given some extra encouragement to stay put with the use of some black cotton thread and superglue. A throw over to me Gliding days. A very secure means of attaching push rods. Topped off with some paint. As with the bow i have added blocks of foam int the areas that I will soon not have access to. Note the brass rod sticking up for the fake push rod mechanism.




The push rod mechanism needs two inlet points on both sides of the raised stern section. This area is outlined on the side and simply needs to be cut out. Once cut out and filed then the inserts can be placed. These tiny inserts need to be drilled and filed out before two small brass rods are mounted. The push rod head is also cast and it features three holes, the main pivot and the holes for the brass shafts either side.










Till next time...

[Davidh]

Hello all, Thanks Gantu.

In the interests of keeping this build log complete , I will continue with the build up to have a complete build, even though the launch of the kit has gone ahead.

The lower bow section needs to be joined to the upper hull. Firstly however I sculpted and shaped the foam that would go in the front section just below the waterline. I glued this in after having fixed in the aluminum attachment plate. I aligned up the bow section and also the rest of the hull was clamped securely to the top and bottom hull to check how they have all been aligned and then cut some narrow strip of glass weave and glued up the two halves.



The curve at the bottom of foam is to move the air bubbles in to the center of the foam and then up the holes drilled along the middle. I have already been playing around with the Foreplanes.



Below pic shows the hulls taped together. Before I did this, I pressed sticky tape down along the flat rim of the lower hull. I then pressed and taped the top hull down and then pressed filler into the gap between the two hull. The filler will stick to the rim of thr top hull and create a tighter seam line between the two hulls.





The stick tape was pressed down along the sides of the lower hull, this means that any filler on here would lift off and the only filler left would be on the top hull and sanded flush.



I taped with masking tape the areas around the joint areas. I also screwed down the bow lower and main hull to help with alignment.



Glass weave laid down. The gap was where the clamp was. A lot of sanding back. Reinforced form the inside too.


Some extra filler and sanding back.



After the font section I then looked at how to secure the top and bottom hulls together. Because thr top hull is mostly flat the way I secure the two hulls will be different. All my previous boats have had round hull sections and the so the use of a lip that slides inside another was quite realistic. This hull with its mainly flat decks won’t really work plus the use of the rim or flange along the top of the lower hull means a different approach. I decided to use stainless steel rod to create drop lugs that will drop into slots in the lower hull.



These were epoxies into place and then had some glass reinforcement. I had to create a slot to accommodate the lugs as I need to drop them in place and then slide them forward for the front lip to push in under the bow. Below, the filler creating a level lower rim on the upper hull.



I then returned to the bow section and after attaching the main hull and top, I realized that there was a gap between the lower bow and main hull. So I then did a similar thing as with the main hulls in that I masked off and filled , screeding smooth the filler and then resanding.





Back to the stern, I started working out the arrangement for all the stern bits. The glands, shafts, props, brackets, rudders and planes. The small parts needed sanding down after coming out of the molds. A little bit of filler here and there. I also had to make sure that the alignment of each piece corresponded with its opposite. Very happy with the alignment of the notches and dimples In the mold.



I use a 3 mm shaft. Checking placement of the hydroplanes is easy. What is great about the stern planes is that I can use a continuous rod. I don’t have a prop shaft right in the way as with most nuke boats. The overall arrangement of thr stern components will make access to all the stern controls the easiest of any of my models.



More next time….

David h..

[Davidh]

Thank-you lads.

Its been a long year of development. Joerg, you are probably right about the bow planes. One day…. Your boat is nearly ready.
Thanks Rob. I still feel as though there are things I need to work on with it’s finer detail. I am however, happy with the video, the Go Pro makes a huge difference. I am just working on the 2.4 Ghz cylinder at the moment.

Regards,

David h.

[JHapprich]

Happy New Year! A nice video! Given the slow speed of the U-Boat, making the bow planes functional should improve the longitudinal stability so you wouldnt need full planes up/down to keep her level.Might be worth trying this time?
Jörg

[rwtdiver]

Hello all,

A new video.

https://www.youtube.com/watch?v=r2GNVSl0PUA

David,

Your SM-U-23 class submarine really turned out nice! You put in many hours of design and work into scratch building this boat, and it was time well spent! The end result really look great David! It almost looked like a full-scale sub in the video. Thanks for sharing the build with us on the forum, it's a joy to watch a master at work!

Rob
"Firemen can stand the heat"

[gantu]

Hello David very nice work and video.

Gantu

[Davidh]

Hello all,

A new video.

https://www.youtube.com/watch?v=r2GNVSl0PUA

[Davidh]

Thank you David.

[He Who Shall Not Be Named]

A most ambitious project. And the quality of your work gets better and better.

David

[Davidh]

Hey Redboat, I'm with you,

I really don't get this whole Northern Hemisphere snow white Christmas thing. I went slope soaring at the beach yesterday, (Christmas day, for about an hour, the sand was soo hot ,30 degrees, dripping).

Hello all,

The conning tower is coming along. I sprayed the Canvas covering with a tan beige and then carefully painted the inside of the railing structure with a dull grey colour. Did this with a small brush. Once the two railings were done I then gave the final touch ups to the rest of the conning tower especially the areas around the tower deck and the raised housing for the Periscopes in the middle. The helm was painted a flat grey colour as there is very little information on the colours of this unit. I drilled out the recess and glued in place. Once these parts were done them I got around to gluing the sides onto the conning tower.








I added some extra scribe lines along the sides of the conning tower and a small hatch at the bottom. I will be weathering the conning tower and giving her some rust here and there. I'm also going to add the periscopes later. One of them will be the antenna mast for the tip of the 2.4 Ghz I intend on using.



I had to fill in a small gap between the two railing sections at the front. This was done with a fine bead of filler and some sanding. I also had to give some light filler around the base of the railing section to blend a little more with the sides of the conning tower. I have had a hard time with the drainage holes. However I have made a start on the drainage holes along the sides of the main deck. After working on the Conning tower I continued on with the main hull. As mentioned in the last write up there is actually a slight lop sided-ness in the hull amidships. One side of the hull approaches the widest point with a slightly more pointed curve. The other side, less so. You really have to look to notice however I have determined that with a little aggressive sanding on the 'pointy' side I can give a more gradual curve that comes very close to the one on the other side. As mentioned, you have to look hard. So as a result I thickened up the rim on the pointy side to give extra material and then sanded back a more gradual radii and it looks better.

The next step was to work out the joints between the top and bottom hull. As is my custom I decided once again on the "Z' cut arrangement. This would see the bow bottom section glued to the main top hull and then very stern upper section glued to the stern lower hull. This has worked well on all my boats. The main thing at the moment however is the sand the top and bottom hulls level with each other. So I got out my sanding board and sanded till I had a nice horizontal flat surface for both.



I had to level the lower surface of the lower bow so that it would mate up the top bow. There was some room for gaps here as I would use fine weave and resin as glue. I just needed to make sure that the lower bow and main hull aligned up perfectly. This design is an unusual departure for me as I usually have the lower bow as a one piece mold. The way I have assembles the Aluminium attachment plate on previous models has been to make the cut in the forward lower section and the rest of the hull after the a plate has been attached. Here the cut has already been made and it means that there are more pieces that have to be aligned simultaneously.

In the mean time lots of filling, sanding, filling ,sanding......



I created the aluminium attachment plate out of 3 mm thick 10 mm wide aluminium bar. Drilled a hole and tapped a thread. Then drilled some holes at the other end for some weave and resin to work its way through. Then resin'd in place. I would then have to work out how to align the bolt hole for the forward part of the main hull. Whiles setting this to dry I cut and started shaping the piece of buoyancy foam (from a surfboard blank supplier) that I would stick in the front section below the waterline. Drill a few drainage holes to let the trapped air upwards and be ready to glue into the lower bow section.




Drilled the holes on either side for the forward planes placement. These planes will be fixed.



Once that I had got the two main surfaces level I would need to tape them up and get them precisely whereI wanted them for the glue up of the lower bow to the top hull. This involved marking out where the drill hole would need to be for the main aluminium plate at the front and making sure that the lower hull and forward section met at the right spot without a gaping gap between them when the bolt is affixed. Lots of converging geometries needing to line up all at the same time.



More next time. I hope every one has had a good Christmas. For those up North, keep warm, for those in my part of the world, crank up the Air conditioning.

David H

[redboat219]