For this weeks instalment I have to report that I finally had a go at flying the 3D printed Typhoon under rocket power. This was with the version with the Rapier mounted, external stores style under the belly.
This attempt, perhaps unsurprisingly, suggested a need for large amounts of down thrust. As motors are in shorter supply than 3D printer filament I went back to the Fusion 360 software and created another Typhoon version this time with a trough. I had tried that before but couldn’t figure out then how to line the trough. This time I made it a bit wider and lined it with balsa.
I’d also discovered that my printed motor holder wasn’t much good. It got soft under fire!
So I redesigned the fuselage with a trough with a steepish curve to introduce down thrust. Moving the motor inside makes for a higher thrust line and thus less thrust induced pitch up moment. And I redesigned the motor mount to leave the motor free to cool.
The trough is lined with balsa and sticky aluminium foil but as you’ll notice things went a bit pear shaped aft of the trough.
This one has a lovely flat glide with a full motor on board and I had high hopes. It weighs in at 40gms with a loaded motor and all necessary ballast! Span 245mm and length 370mm.
But the next trial under power still showed too much pitch up. I did think, as I walked home dejected, that I could raise the thrust line still further by giving it an aluminium lined printed augmenter tube. But then it would need a little hatch for loading and maybe remote electrical ignition. All doable but another rabbit hole to go down.
Another of the problems is the current model is that it is a little awkward to hand launch. Maybe I’m just cack handed but I was wishing that my catapult elastic would arrive. Then I could just have a post in the ground, pull back and let go. And think of the duration boost!
But I think the next move is to sort out the motor mount. So that I’m sure of a consistent thrust line.
While I was waiting for the weather I did start looking at another type. And the Blackburn Buccaneer, the Banana Bomber, came to mind. Compared to the Typhoon its wings are tiny things but it looks like it gets a bit of fuselage induced lift.
I had another 3D model to start from. I immediately started chopping it up according to what now seems a satisfactory formula: front fuselage to be printed with a 2 layer shell, rear fuselage to be printed in single layer spiral mode, wings also in spiral mode and the vertical and horizontal surfaces 3mm and 2mm thick respectively to be printed flat. I had to remove the fin from the original 3D file to have a chance of printing the rear fuselage in spiral mode.
I haven’t tried adding a trough yet. I thought I’d see what I got to with the Typhoon.
I also recall that there was an all white version so that matches the filament colour. Now I just need a set of transfers!
And it does glide rather nicely.