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R25 class Räumboot - building finally


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31 minutes ago, Steve D said:

* To explain that colloquialism, in 1971 the UK went decimal, so changed to 100 new pennies from the pervious 240 pennies to £1.  Hence for years afterwards, people would often talk about prices and then repeat the value "in old money", so 25p or 5 shillings in old money.  That stuck with me and it comes out talking about inches and mm.  Our move to the metric system was set to take place over a number of phases.  The story goes that when the phase came to deal with liquid measures for alcohol, Harrod Wilson (the PM) blocked the move as he didn't want to go down in history and the person who abolished the pint (beer)...  After that, it never got restarted so we are left selling petrol in litres but with cars that measure consumption in miles per gallon :doh:  I love it....

 

Thank you for an interesting digression into history! I didn't know that.

👍

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2 hours ago, Steve D said:

The story goes that when the phase came to deal with liquid measures for alcohol, Harrod Wilson (the PM) blocked the move as he didn't want to go down in history and the person who abolished the pint (beer)... 

Gidday, I didn't know that. "I'll have a 0.473 litre of beer thanks" - doesn't sound quite the same. 🙂       Regards, Jeff.

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9 hours ago, Jochen Barett said:

Yes, that solution implies new beer mugs for the entire UK.

UK's half metrication has many odd consequences.  Timber in the UK is still sold in units of 0.3m (so ~ feet) and still made in nominal imperial sizes (2 x 1 being 2 inches by 1 inch, nominal saw size = 44 mm by 22 mm final planed size, strictly speaking is should be referred to as 1 x 2 but no one seems to do that :hmmm:).. So going to a timber yard today, I will still order (say) "4, 2.4m lengths of 2x1" and be understood perfectly unless the guy is young and new to the job, 2.4 m being 8 feet of course.  You can impose the metric system but you can't rebuild all the houses so plaster board is still sold in 8 x 4 sheets (feet of course) and tapes have diamond markings every 16 inches to mark where studs are placed (1/3rd sheet width)...

 

This thread is a German vessel, being build to 1/4inch to 1 ft scale, and while I think in inches when modelling, I will mostly measure in mm and of course modelling timber sizes are in mm.  1 inch full scale is divided by 1.89 to get its size in mm at 1/48th scale.  RN vessels tended to size things for convenience so hatches would be 18 inches square etc, why make stuff hard when there is a war on....

 

I'm sure this all sounds nuts to people not living in the UK, but to engineers of a certain age educated in the late 60's straddling the change (like me) it is as natural as breathing.  And please don't get me started on SI and metric units as applied to civil engineering,.....

 

Musing over, back to modelling

 

Steve

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1 hour ago, Dmitriy1967 said:

For people living in a single system of measures, this is amazing! I really like the UK for its unusual traditions.

 

The younger generations are incrementally becoming metricated. Beer in bottles is sold in metric measures for instance. It's now difficult to find anyone under forty who know what a chain, rod, pole or perch is in linear measurement, a gill, fluid ounce or a quart in liquids, or a hundredweight in mass.

 

(22 yards, 5.5 yards, 5.5 yards, 5.5 yards, 0.25 pints, 0.05 pints, 2 pints, and 112 pounds respectively.)

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29 minutes ago, Bertie McBoatface said:

chain, rod, pole or perch is in linear measurement, a gill, fluid ounce or a quart in liquids, or a hundredweight in mass.

My personal favourite is a "slug" the unit of mass when talking about pound as a force (or something like that......) :nuts:

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Update on the hull, been working on the brass fittings.

 

First, the prop shaft, end flange and shaft extension to the A frames.  The insert is just enough to maintain alignment, this is fixed in place but the shafts will remain removable at this stage. (they are 1.6mm dia, 3 inches or 75 mm full scale)

 

DSCN2732

 

Next I turned the A frame sleeves and made up the brass cores for the three rudders, also on 1.6 mm brass shafts, 0.4 mm thick.  This is before I'd cleaned up the soft solder, don't judge, 

 

DSCN2734

 

Next stage, the brass rudder cores where lined wiht 1 mm maple and sanded to shape.  Final shaping will be with filler, but this is near finish

 

DSCN2737

 

Now I can locate the A frames relative to the rudder, the 4 bladed props will be cast bronze as the last few models.  With this all made I can ensure these fit properly

 

The A frame supports were silver soldered to the shaft bearings and after plenty of filing and adjustment, the hull mounting plates were attached wiht soft solder to form a good join and create a smooth transition (just noticed the middle rudder is 180 rotated in this shot :doh:)

 

DSCN2739

 

Then onto the cooling water openings.  There are two each side. more or less above each other  The intake is elliptical so I knocked up a simple jig to solder the pipes to the cover plate at the right angle (45 deg)

 

DSCN2740

 

Then they were cut out and files to shape.  The exhaust (above waterline) was a simple square plate set into the planking, it is slightly smaller, here they are mounted

 

DSCN2741

 

DSCN2742

 

Lastly, progress summary shot, the lines are looking nice now

 

DSCN2744

 

Next onto the deck planking forward of the deckhouse to locate the crew flat hatch shield

 

Cheers

 

Steve

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2 hours ago, Dmitriy1967 said:

It is strange that the intake of cooling water, which is under water, protrudes beyond the dimensions of the skin. After all, in this case, it creates additional resistance to the movement of the ship, slowing it down.

Scoop intake, saves using engine power to run cooling water pumps, speeds it up

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9 hours ago, Dmitriy1967 said:

It seemed to me from the image that the intake was directed backwards on the contrary. Or is it not so?

I admit it is counter-intuitive.  When I saw your first comment last night on my phone, I thought I'd got them the wrong way round but if you look at this picture the raised edge is towards the bow (to the left) as I have made it. 

 

 

5  räumboot - Copy

 

It was the same detail on the S-boote.  I just double checked that detail and realised that these are underwater exhausts to reduce noise,, not inlet pipes.  The water inlet is clearly shown below in this detail shot of an s-boot (IWM picture clearly labelled).  So the pipe above is probably a bilge pump outlet which means I'm missing the inlet opening, not visible on the r-boote picture above and I'll now need to add it :doh:

 

A GERMAN E-BOAT. 24 AND 25 APRIL 1945, PLYMOUTH. VARIOUS CONSTRUCTIONAL ASPECTS OF A RECOVERED SUNKEN GERMAN E-BOAT.

 

On the S-boote the exhaust outlet is ~ 50 mm dia larger.  R-boote were not built for speed but manoeuvrability so less engine cooling makes sense.  The oval shape is probably the pipe intersection angle to the hull aiding flow.

 

Thanks for your comments, building a model generates some degree of tunnel vision and justification bias.  Challenges are always welcome so I can produce the best result 👍

 

5th and 6th holes coming

 

Cheers

 

Steve

 

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18 hours ago, Dmitriy1967 said:

It seemed to me from the image that the intake was directed backwards on the contrary. Or is it not so?

You're right Dmitry, I was reading the comments and not looking closely at the photo's

8 hours ago, Steve D said:

I just double checked that detail and realised that these are underwater exhausts to reduce noise,, not inlet pipes.  The water inlet is clearly shown below in this detail shot of an s-boot (IWM picture clearly labelled).  So the pipe above is probably a bilge pump outlet which means I'm missing the inlet opening, not visible on the r-boote picture above and I'll now need to add it :doh:

That's a good photo Steve and shows how the designers have given thought to improve flow and reduce backpressure in the exhaust, which in turn will help engine power output. Position of the outlet in an area of the hull which is turning in sharply will place it in an area of lower pressure, the protruding fairing in front of the exhaust pipe is there to accentuate this effect, and the pipe angled backwards helps generate a venturi effect to draw the exhaust or cooling water out. The scoop I was referring to on the inlet is placed in the higher-pressure area of water flow round the hull and is used in conjunction to outlets similar to this to induce cooling flow with no or limited pumping capacity.

 

I'm not sure about the large outlet above the exhaust being a bilge pipe, looks more like a cooling outlet to me. One of the small outlets either side looks more of the size I'd expect for a bilge oulet, I would have thought it would be 1-2" diameter, no more. Apart from the emergency bilge suctions in the engine room which were interconnected to the cooling system and used the main cooling overboard, bilge suction pipework on large container ships I was on was no more than 5-6" diameter, the overboard from the treatment plant wouldn't be more than 2".

 

Regarding where the inlet is, there looks to be an opening on the extreme left of the photo, and possibly another one under the piece of wood packing further aft, both are in a good position for an inlet ie forward of the outlet, and lower down on the turn of the bilge.

52109375191-6d214d98d2-h.jpg

 

 

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Thanks David,

 

In the end I chose the area local to the red circle to the left of the outlet, so grouping the openings in a similar manner to the S-boot which came from the same shipyard and shared many aspects of design

 

Priming and finishing filling the hull now, pictures later

 

Cheers

 

Steve

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Mixing it up a little, I made a serious start on the main etching sheet with the sweep winch.  Just thought I'd start with the hardest component and go down hill from there ⛷️

 

So, anyone for a 1/48th scale winch kit, 31 components plus some scrap tube sections and a couple of turned parts.....

 

Prize for anyone who can work out the construction sequence...

 

sweep winch

 

Hopefully, some more pictures of the hull tomorrow

 

Cheers

 

Steve

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Back to building..

 

First, the hull got some serious filling and sanding.  This is after the first coat of white primer which helps show up the defects, so many defects...  

 

DSCN2746

 

Then a final coat of white primer overall (and still more minor filling)

 

DSCN2747

 

Remember, I'm not going for a perfect smooth finish, I want some planking lines to just show through on close inspection.

 

Then a coat of grey primer below the waterline

 

DSCN2748

 

And finally, black spray and matt varnish

 

DSCN2749

 

DSCN2750

 

So, below the waterline is actually a fine base now but it will be re-touched with weathering.  Above the waterline I've left it in white primer.  This will be covered in Kriegsmarine pale grey overall and then the camouflage dark grey pattern added, this will of course be much later, time to move onto the deck

 

The deck has a 3 mm margin plank that the planks cut into.  3 mm x 0.5 mm planks don't bend in that axis so I made the margin planks up from 2 x 0.5 (which could just be persuaded at the bow) and 1 x 0.5.  Then I started the rear deck planking from 2mm (4 inch or 100 mm full scale) planks.  I had a big debate with myself (no one else was interested) about plank lengths and joins.  Staring at the pictures, I really can't identify plank joins at all so that was no help.  I know in the RN, plank joins were staggered to repeat every 4 planks, with lengths of 16 or 20 ft generally used.  That's a lot of joints as 20 ft 4 staggers gives me 5 ft between joins on adjacent planks.  Didn't want so many joins showing so I've gone for 24 ft planks and a joint stagger repeat of 3, making the joins 8 ft apart.  Excuse my thinking in imperial, old habits

 

The sides of each plank are sanded and then edge lined with a Sharpie permanent marker to indicate caulking.

 

Here is the start, framing is for the rear deck skylight which will be slotted in later.  Galley hatch is still removable, it will be lined with wheel-rivet marked aluminium sheet later

 

DSCN2751

 

And later (actually much later...)

 

DSCN2753

 

One of the very many challenges with this approach of individual planks is getting the edges the same.  Here I am at the boundary of the steel anti-slip decking more or less perfectly equal.  I'm sure my luck won't hold at the bow.  I've also been very lucky at the deckhouse intersection without needing to split planks, none of this is intended, it was pure luck, still I'm not complaining..

 

Forward we will have the fun of chopping the plank across the outer 1/3rd and cutting it into the margin plank.  I've done this before with 2 mm planking, fiddly doesn't express the right level of frustration generated by this process..... Still, the result will (I hope) be worth it

 

The exposed timber deck is one of the reasons I chose this vessel, its a slow steady process but actually very rewarding

 

Cheers

 

Steve

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2 hours ago, ArnoldAmbrose said:

I think that's a nice looking hull shape

Thanks Jeff, she is coming together now, you can start to get a feel of the boat building it this way.  The hull form has a very narrow entry, quite a pronounced "belly" and a long flat tail (probably required by the original V-S propulsion system) with pronounced tumblehome at the stern.  Three very distinct sections to the hull.  I think she would have been uncomfortable in any kind of bad weather, no bilge keels to assist roll damping.  Designed to go reasonably fast for the power available.

 

Enough musings, that deck won't plank itself

 

Cheers

 

Steve

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Slight change of topic from endless hull pictures (even I'm bored) so I made a start on the 3D print files for the build.

 

First simple job, the engine room side vents that sit beneath the open bridge.  This picture is a really clear shot of what these looked like (the flappy things underneath the life buoys are what I'm referring to).

 

R40f

 

Actually quite hard to make in brass due to that mastaba shaped pressing in the centre so I've been lazy and opted for a print file.  We'll see how well these come out, I might change to brass if they don't look right

 

Here is my finished model.  I'd love it to be a little crisper but material limits are at play and it needs to be printable (for reference the model size is 15 mm by 6 mm overall) so that eyelet is really tiny

 

engine room vent

 

Next the DC racks.  These Kriegsmarine racks are complex due to the rocker mechanism, RN ones are simple roll-off ramps

 

Here are a couple of pictures showing them, the first on an R25 class R-boote in Norway (later war model, note gun shield in the background on the 2cm flak).  See the chain that replaces wire where the handrailing needs to open to release, interesting little detail to incorporate in the model

 

depth charges on Räumboot R238 in Norwegen

 

And a good shot of the back, not an R-boote this time but the rack is the same

 

aYkeFPo

 

Here is my model

 

depthcharge rack

The ends are different, note the lifting eyes on the ribs at each end.  The three cross rods will be added using brass rod, very flimsy if printed.  Again, the thickness is required by the material limits of the printing, it will look OK panted.  The tie will be added from fine cotton

 

It is printed in two parts, the DC and its cradle rockers are one piece and the rack is the second.  This is what the actual print parts look like though they will be saved as separate models as the rotation and supports are different

 

dc rack print

 

More boring hull pictures later, deck planking is complete (finally.....)

 

Cheers

 

Steve

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2 hours ago, ArnoldAmbrose said:

Now that's a nautical term if ever I heard one

You're right Jeff,, I should have said marine flappy things... 

 

I actually think they may be Motorraum-Lufteinlassgitterabdeckungen , :book: what say you @Jochen Barett?  You gotta love German portmanteau words

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