H-Maskinen is going to fly again, after almost 90 years.

This time as a model.

H-maskinen was an aircraft designed and build by Orlogsværftet (Naval Dockyards) in Copenhagen. The first flight was in 1917 and was in service from 1917 to 1924. A total of 9 were built.

Very little is known about the aircraft, and only a handful of photos exist. However, after a lot of research at the national archives, other museums, and with help from private individuals, I have managed to acquire enough information to build a 1:5 scale model.

For more information about this aircraft, look here.

As noted earlier, I have a fairly complete set of plans for the full-scale aircraft, which I will be using for this build.

This plane had a wing-span of 11.54 m, length of 8.0 m and a height of 3.15 m.  As always, my models are to scale 1:5, giving this model a wingspan of: 2.308 m, length of 1.60 m and a height of 0.63 m – a fairly nice sized model.

This aircraft is a bit unusual, in that I have the construction drawings, and instead of trying to add more details to a 3-view based on photos, I now have to do it in reverse, i.e. I have way too many details and need to reduce the complexity of the model. So, in this case, there is absolutely no guesswork.

This aircraft is pretty simple to build. I will enter all the blue-prints into the PC and make a 3D-model of them, trying to figure out how all the different parts fit together. Since the actual assembly drawings are missing, it might be a bit of a challenge. However, I hope I can figure it out.

The fuselage of the H-Maskinen was of standard design for an aircraft of that period, and consisted of wood and canvas. Metal brackets were used to hold it all together, and turn-buckles and piano wire were used to true it up.

The canvas would have been silver-doped, like all the other Royal Danish Army aircraft of its day, and thus slightly see-through. I therefore have to design the model in that fashion too. If the canvas had been painted, and not see-through, it would have been much easier to make the model.

Anyway, I have first drawn the fuselage in Alibre CAD. It is not very detailed this time, as I do not imagine that I will be selling any of these plans. They are after all only relevant for a handful of Danish large-scale enthusiasts.

I then printed out the side-view on a sheet of paper, and glued all the spruce stringers together based on the drawing.

Next, I added the internal stiffeners in the cockpit area, exactly where the real aircraft had been reinforced. I then added some 0.8mm plywood where the actual aircraft had plywood sheeting.

Since the H-Maskinen had an open cockpit, it is possible to see its inside it, and it must be decked out with all the right details, including the internal reinforcements.

I then built the other fuselage side on top of the first one, to make sure they came out 100% identical. A piece of plastic sheet was placed between the left and right sides, to prevent the two sides getting stuck together.

The next step will be to join the two fuselage sides and add some top and bottom formers.

Here is what the CAD looks like.