Choosing hatch size and marking trailer
We chose to make our main hatch 1500 x 700mm. It seemed to be a common size for a trailer like this one, and worked because we wanted wall space either side of the hatch for strength, and so that we can later fix lights either side of the main hatch.. Pre-fabricated serving hatches are available for around £600.
The height of the hatch was determined by the how high we wanted the serving bar to be when stood inside, whilst being a good height for customers on the outside. We were also limited by the curvature of the roof, so we ended the top of the hatch before the roof started to curve away, or fitting the hatch could become difficult.
Fabricating the hatch frame and door
Now we knew the exact size of our hatch, we set to making the door and door-frame.
We used 30mm steel angle and flat plate to create both.
A design was drawn, a cut list made, the metal marked, and then cut using an angle grinder.
We mitred our cuts on the angle iron to make all the corners fit together beautifully, being careful of which ways our toes and 45s were facing.
Toes…
45s…..
Once all the pieces had been cut, they were tacked welded together at each join. We then checked and adjusted for squareness of the frame by measuring the diagonals and ensuring they were equal, and checking with a spirit level. Then the frame was clamped in place and fully welded together.
Once the door-frame had been made, we could fit the static frame around it for a perfect fit.
The continuous snail hinge
We wanted a hinge that would be water tight from above for our hatches. In our research we came across the ‘continuous snail hinge’. This is an elegant piece of engineering that we deemed perfect for our serving hatches.
We bought 5m of this hinge from Hinge -AA – Stedall Commercial Vehicle Components . This would be plenty for both the main and the front hatch, with some leftover (for the next food trailer?!)
We marked the hinge at regular intervals for drilling, then used a 5mm drill bit to make the holes for the bolts that would attach the hinge to the frame.
Then we proceeded with a similar method to bolt the moving hatch onto the hinge.
Below you can see the flat steel that we also welded to the hatch to create a watertight overlap.
We then checked the size of the hatch frame on the trailer before proceeding with cutting THE BIG HOLE!
Cutting out the hatch (scary but ultimately easy)
When it came to actually cutting the hole, it took only 15 minutes. But it was lots of fun
And then there was a giant hole… the horse trailer was starting to look like a food trailer!
To insert the frame into the hole we cut off some of the trailers angle iron framing as it would be welded onto the outside perimeter of the hatch frame, whereas the aluminium sheet needed to finish as close the inside edge as possible for gluing, process shown below.
We applied adhesive silicone to the frame, then pushed it into the hole. The frame fit nice and snug, and was then clamped in place and welded in.
We bolted half of the hinge to the door frame, then added rivets to further secure the hinge.
The hatch door
We wanted to use the hatch ‘offcut’ to create the body of the door, so that when the hatch was shut, the trailer looked almost original. Plus we love recycling! So the cut-out piece was reduced in size slightly (to account for the framework that had been added), and then welded and glued back into the inner door frame.
The complementary part of the hinge was bolted onto the door frame.
The hinges then simply slide into one another…
…and here is the hatch with its door!
The door was cleaned up and given a few coats of paint.
Et voila! The main hatch is complete 
Now the trailer is really beginning to take shape. This was very motivating and felt like a good milestone to hit.
