Balsa Wood Hurricane – the first test flight

As you may have guessed from the fact that the title refers to the ‘first test flight’, it wasn’t wonderfully successful.

 

As you see from the video, the plane quickly veers to the left, flips on its back and drops like a stone.

One  potential issue is with the weight. The flightpath suggests that the centre of gravity is too far back, but the problem could be that the nose is too light rather than the tail too heavy. However, all the talk on the balsa modelling forums I have skimmed is about keeping the model as light as possible. Clearly more reading and experimentation is needed. As a result, you may see my Book Diary dominated by volumes on free flight aerodynamics and the like over the next month or two.

Further examination of the model post-test flight revealed that the whole tail section was slightly twisted, which almost certainly contributed to the model flipping as it flew. I think this problem may have its roots in the original construction rather than crash damage. Therefore, the plane may well be doomed from the outset, and I will have to consider the implications before getting too far with the next flying model. Before that though, I will repair this one (the undercarriage took a bit of a battering and needs re-glueing), and try to adjust the tail surfaces to compensate for both the natural tendency to diverge from straight-and-level flight caused by the rotational effect of the propeller and my shoddy workmanship.

The only possible factor which could have led to such a disappointing first flight which is outside of my control would be the wind. As you can see in the video, it’s a moderately breezy day. Perhaps I should have waited for a calmer period. I also launched into the wind (as much as I could – it was swirling a little in the enclosed garden) which should give the plane more lift. The lightness of the plane, combined with the wrong centre of gravity could have contributed to it gaining the lift too quickly and flipping over as it did.

All in all, a sobering experience, but one which has made me more determined to get it right in future. I suspect my repairs will be somewhat in vain and this model will end up on display only, but even if that is the case, I have learned important lessons from it.

Balsa Wood Aeroplane

Back in February, Emma bought me one of these as a present for our anniversary:

As you can see, it’s a balsa wood aeroplane.

I must admit that I had completely forgotten about balsa wood planes until I opened the box. I then remembered that back when I was about seven or eight, I built a couple of these with limited success. (Well, I built some very simple balsa wood kits. The problem was that balsa is quite soft and fragile, and so doesn’t last long when you’re a clumsy sod like me.) The kits I remember building were more like this:

Wind forward nearly twenty years, and I’m back glueing together bits of balsa, only this time with a little more success than as a nipper. The kit is significantly more complicated than the model above.

This is the first stage completed:

Here, the fuselage and wing ‘ribs’ have been glued to the main structural ‘longerons’ and then the whole structure reinforced with ‘stringers’ (the thin strips of balsa wood running horizontally along both the fuselage and wings).

Once the frames are made, they have to be sanded to remove any balsa fuzz and then sealed with a coat of either cellulose dope or a mix of PVA glue and water. I bought the dope and was intending to use it but it really needed to be done outside (to prevent the fumes turning me loopy) and so progress stalled as the weather has been rubbish lately. I then found on the internet a site which assured me I could use a PVA glue and water mix which was much more friendly so I could do it indoors.

After that comes the covering of all the pieces with tissue paper. This is done piece by piece rather than in large sheets, and again I used a 50-50 mix of PVA glue and water to adhere the paper to the frames. This left me with the pieces looking like this:

The pieces are then sprayed with a fine coat of water to shrink the tissue paper over the frames and tighten it. The tissue is then strengthened with a couple of coats of the PVA-water mix (much like papier mache) and left to dry.  After that, they are all glued together using the balsa glue from the first stage, and a card wing fillet is attached to smooth the join between wing and fuselage. After joining the major components, this is what you get:

As you can see from the second photo, I attached the undercarriage structure too. The wooden parts come with the kit; the metal parts are half a roughly straightened paperclip superglued to each ‘leg’. The wing fillets haven’t been attached at this stage, and there is still a little work to be done around the join between the tail and the fuselage. Also, before painting can begin the nose and canopy need to be glued on and masked where appropriate.

At this stage, I was very pleased with progress as there was barely a wrinkle in the tissue. The kit came with a catalogue of Guillow’s kits tucked inside, and they use customers’ own photos to illustrate the potential end result. Several that I saw had wrinkles and slack areas, and I was feeling quite pleased with myself that I had managed to avoid this so far.

Next came the attachment of the various cosmetic bits and pieces, such as the radiator and air intake on the underside of the fuselage/wing join, and I also installed the rubber band for the propeller, and therefore the engine cowling and the propeller itself. I also painted the cockpit canopy, but the instructions insist that this must be the very last thing to be attached.

Ignore Zippy and pay close attention to the white plastic pieces on the underside of the plane.

The blue stripe down the middle of the plane is the rubber band. The wheels have been attached temporarily to see how it looked.

Here’s the canopy masked and painted silver. The real canopies were painted in the colours of the camouflage scheme, but I saw a photo of this kit with a silver canopy and thought it looked pretty nice so decided to copy it.

The painting isn’t too difficult – one of the advantages of this sort of model over an injection-moulded plastic kit is the  significantly lower level of detail. After the underside was painted ‘sky’ (a strange, green-tinted beige colour), the top was given a couple of coats of brown, and the model looked like this before the green went on:

The only drawback  of this sort of model that I have discovered so far is the translucency of the tissue paper covering makes it difficult to get a solid coat of colour on without going crazy with the number of coats. As you can see, there are a couple of patches on the wing and the side of the fuselage where the paint is thinner and streakier.

After a little more painting, it looks like this:

Then, with the decals added, along with the canopy, it looks like this:

(Apologies for the slightly faded colours, there was bright sunlight streaming through the window, which has been such a rare occurrence lately that I didn’t even consider the effect on the photos.)

Essentially, that is it finished. All that remains is a test flight! I’ve had a great time building this plane, and will definitely build more. I am getting wildly ahead of myself, but I’ve seen that some people convert these to remote control…