We put the clocks back last night, so I got an extra hour in bed. Unfortunately, the weather has also changed as we had a very strong northerly wind this morning. It was marginal on whether you could fly, but the wind brought in a lot of rain clouds. I decided not to go flying and ended up taking the door off of a shed. It’s a long story, but the key broke off in the lock. Anyway, around 10am it got very dark and rained for a bit. About an hour later it was bright sunshine again, but I think that’s only because the now gale force winds had scared all the clouds away.
I’ve been progressing the Autogyro repairs this week as I really want to get it into the air again. In the end I decided that the base and sides were too shattered to stick back together like a jigsaw, so I’ve cut new pieces to graft in. Using templates taken from the plan, I’ve made two new sides.
The pictures show the template held up to what was left of the fuselage side. I cyanoed the bits back together first, before laying the side template over the balsa and deciding where to make my dovetail mark. After drawing on the template, I cut along the lines and laid it back on the fuselage side, allowing me to mark it and cut away the old wood. After that I used the other half of the template to make a new fuselage side, which slots into the dovetail joint after just a tiny amount of adjustment with some sandpaper. This was then repeated on the other side using the same template.
Now I have a kit of parts for a new nose, I can start glueing things back together. The main thing to be aware of here is to get everything square. As there is no full-size engineering drawing in the original magazine article, only 4xA4 pages of parts, it’s difficult to find any datum lines to match things up to. The best straight line is the one along the centre of the fuselage base, so I took this as my datum and matched everything up to it. The original pencil line still exists on the remaining piece, so I just extended that onto my new base section. However, I did run into one problem which I’ll have to come back to later. The pictures below show the new base piece being grafted in. I took a lot of care getting this exactly right in all three axes as the base forms my datum.
It’s not a bad fit, and most of all, it’s straight.
I was able to save the plywood undercarriage plate, which saves me a lot of time having to cut, drill and route a new one. This is where I discovered a bit of a problem, though. As I mentioned earlier, there are no full-size engineering drawings, so I took the fuselage base template from the plan and matched it up to the real aircraft. Now, I assumed that the piece went all the way to the back of the fuselage and positioned it appropriately. Unfortunately, this left me with about a 5mm discrepancy as I discovered when I put the ply undercarriage plate in place underneath the new balsa base that I had just glued in. Yes, sure enough the base was too long. The sides are fine, but the base doesn’t extend all the way to the back. Never mind, it’s easy enough to cut the offending extra bit off. I just like to get everything exactly right and this was a bit embarrassing. With a trial fit of all the front pieces showing that everything was now good, I glued the ply undercarriage plate underneath the fuselage base.
As a small aside at this point, I’ve been trying out a new type of glue. For the balsa fuselage base and the ply undercarriage mount, above, I used some “Gorilla Glue” for wood. They also make a cyano Gorilla Glue, which I’ve found to be very good, in fact I used it to piece together the fuselage sides, but I hadn’t tried the wood version before.
The instructions say to make one surface wet, then apply glue to the other surface and clamp together tightly. This is because the glue is rather sticky and forms a layer between the two surfaces being stuck. I’m not really sure whether I like this glue yet, because the curing process involves it increasing in volume by about four times. This results in a sticky foam substance leaking out from between all the joints, which requires sanding off when set to achieve the desired finish. Have a close look at the pictures of the ply undercarriage piece being glued above and you’ll see what I mean. The excess foam from the glue expanding is visible between the pieces being joined. This can be an advantage if it’s something where you need good gap filling properties, but personally, for this job, I think I would use a regular Epoxy. The original Autogyro was glued together with Z-Poxy and a Deluxe Materials PVA, which both worked very well. I’m also quite partial to aliphatic resin.
That’s as far as I’ve got for this week, but later on I’ll probably glue Pete the Pilot’s head back onto his body. I need the top section of the fuselage back together for a trial fit before committing to glueing the sides and front back on. I don’t want to get it all back together and find that the canopy doesn’t fit on any more.
Let’s hope next week brings some better weather.