Hull Assembly

With the hull detailing mostly completed, it was finally time to assemble the hull. (That, and I wanted to show a bit of progress.) This was the point where I would see if I had made all the correct measurements for the inner pressure hull and other interior pieces. Once the first bit of glue was applied, there was no turning back.

There were a few minor details to take care of before cementing the hull halves together, though.

Exhaust System

I decided to add the major components of the exhaust system inside the hull, as they would be fairly close to (and visible through) the rear upper drainage holes. Armed with my reference books and some pictures of other U-boat models, I set to work.

The muffler system exhausts to the outside air through the large rectangular opening of the diesel exhaust port. I used thin sheet styrene to extend the rectangular passage inwards, and then used various sizes and lengths of hollow styrene cylindrical tubing to make the rest of the exhaust system.

Exhaust system

 

Bow Torpedo Doors

The U-brass set includes bow “cheek” pieces as well as their corresponding torpedo doors. I took my time to bend the bow torpedo doors into the proper 3D curved shapes, and then used CA glue + thin styrene strip to affix the torpedo doors in place.

Bow torpedo doors affixed in place Complex curves to doors

Painting

Airbrush Equipment

Since I began modelling again with U-625, I have tried various airbrushing equipment before finally settling on ones that I am very happy with:

The Iwata Power Jet air compressor in particular is a dream to work with; auto on/off, built-in pressure tank, and quiet operation. I finally settled on the Iwata Revolution CR dual-action airbrush as my favourite so far; it works very well and is reasonably priced.

Painting Interior Components

I painted the following lower interior components before assembling the hull; these lower pieces would be inaccessible after the hull was assembled:

  • centerline baffle plates (behind the bow & stern lower flooding vents)
  • hull interior (especially around any opened flooding holes)
  • inner pressure hull – bow & stern ends

I also chose to paint the following upper interior components and areas at this time, as it would be easier to do earlier rather than later:

  • saddletank extensions
  • all ribbing
  • exhaust system

I airbrushed everything dark grey:

After the dark grey finish was dry, I airbrused thin bands of the Model Master 2025 Marine Corps Green (using the same thinning ratio & pressure).

When all the pieces were dry, I airbrushed a light coat of acrylic clear flat to ensure there were no overly-glossy areas:

Painted interior parts (showing exhaust system) Painted interior parts (showing saddletank extensions & ribbing)

 

Assembling the Hull Pieces

The moment had arrived, and I found myself pausing (briefly) to reflect on the work that had lead up to this moment. From test-fitting the hull pieces several times, I knew I would have to take a 3-step approach to assembling the hull.

  • Step 1: Glue the centerline baffle plates in place, and then properly place the inner pressure hull inside the hull halves.
  • Step 2: Cement the hull halves together using liquid cement (I use Tenax-7R), apply masking tape to ensure the seams set, and allow to dry & cure.
  • Step 3 is (obviously) the final step in the 3-step assembly process.
    I knew that with the inner pressure hull inside, the top of the hull (where the deck sits) is pushed slightly open. If left like this, the deck would not easily cement to the top of the hull. I needed to squeeze the hull together a bit and make it remain in the proper shape… but how?

Using sections of the kit upper deck as correct-sized spacers, I put those sections in the proper locations, and then used masking tape to squeeze the hull together. With everything set, I then ran a bead of CA glue along the edge of where the saddletank extensions touched the inner pressure hull, and then used CA accelerator to quickly cure the CA. Carefully removing the spacers, the hull stayed in the proper shape and did not rebound outwards. Whew!

After drying, I airbrushed the top of the inner pressure hull using the same Humbrol 125 US Dark Grey as before.

Pre-squeezing the hull to the proper shape Gluing the hull into the proper shape