29 April, 2013

Catalina - A Watery End ?

After the maiden flight
Here's my Hobby King Catalina after it's maiden flight.

The weather was a little breezy but not bad and well within the conditions I would expect to be suitable. I decided the maiden flight should be over land or really more to the point, the maiden landing would be on land so that recovery in the event of any power problems would be straightforward.

The aeroplane was pleasant to fly after a little trimming and had sufficient power to combat the breeze. After the necessary trimming out, low speed and stalling tests I was satisfied that landing would not be difficult and carried out a few runs through the landing strip. Only one problem, that breeze was building up and the sky was becoming more overcast. 

On my first landing approach the dull visibility meant that when I descended after passing the hedge at the end of the field the mostly dark front of the model seemed to lose itself in the leafless hedge so an abort was an easy decision to make. The second approach, with a proper breeze now, was proceeding fine except as I neared the landing strip the breeze lift  the model up and slewed it sideways... another abort. Third time and all went well, I had to work the throttle a lot to maintain a good descent and approach over the strip. It did try to float up again in a flurry of a breeze but this time I was ready for it a good landing followed in the middle of the strip. The model looked elegant in the sky and flying from water should provide an interesting alternative to field and slope flying.

Box Contents
All sounds great doesn't it? Well it's not so bad now it's built but as you will see I experienced many problems getting ready for flight. It was a budget buy stated as being "PNF" which I presumed to mean plug and fly, that is plug in a receiver and a battery and it's ready to fly. The idea was that I could quickly get this model in the air inbetween other builds however when I opened the box and surveyed the parts it's clearly more of an ARTF (Almost Ready To Fly).

Okay let's argue that PNF means that you have to plug in (and glue) the parts and then it's ready to fly. Well let's not because to be able to plug in the parts they would have to fit together properly and accurately; they didn't. There were other issues too, so much so that in my opinion whatever PNF is supposed to mean this wasn't one, it's more of an ARTF with issues. I can't criticise the kit enough and just to give an idea here a list of the main issues:
  • The wing halves couldn't be joined because the one of the spars was longer than the other preventing the joining surfaces from meeting. This problem on it's own perhaps isn't too great an issue but it it wasn't on it's own. 

  • The instructions state to fit the ESC (Electronic Speed Controller) in the servo bay, near the front of the aeroplane. There's actually two ESCs, one for each motor and as supplied they can't go in the nose because the wires are only long enough to reach the middle of the wing. Worse still there's nowhere mid wing to put the ESCs, I ended up mounting one on each side of the battery bay so I had to buy suitable wire to make extensions.

  • There was nowhere to put the wing servo wires and motor wires. In some parts the main spar was deep enough into the wing to allow the servos leads some recessing but it wasn't clear whether this was intentional or not. I had to make a channel for the motor wires which wasn't the end of that problem as the wires also prevented the wing from seating properly and more cutting away was needed to sort that out.

  • There's another thing about these wires under the wing - they have to have joins in them and they are not sealed against water. It's intended to be used on water! I have fitted heatshrink tubing over the joins.

  • The model is intended to be used on water so one might reasonably expect a waterproof hull but expectations were dashed when I found that it leaked. I had to seal it myself with thinned down epoxy which found the gaps and sealed them up.

  • These spinners are supposed to round! They are both for anti-clockwise rotating propellers too. I tried to get them back in shape by pushing them into a tube and then warming them up with hot water. It didn't work, so I had to throw them away.

  • On the subject of quality, care and attention, is the glue intended to fill the channel the spar is in or not? Sometimes it does, sometimes it doesn't. Glue was splashed on the wing surface too. The spar at the front in the second photograph below is not fitted level with the underwing surface. That's a problem in that same spar rises through the top of the wing where it forms the mounting hole for the motor bearer. So that wasn't level either and that caused problems fitting the motor bearer because the low corner was below the surface of the foam.So I had to fix that.

  • The mounting holes for the other motor bearer had a different problem, they were not aligned correctly resulting in a misaligned bearer. To accommodate side thrust? No because the the other bearer was at 90 degrees to the wing and Hobby King had provided clockwise and anti-clockwise rotating propellers - the purpose of which is to eliminate the need for side thrust. This makes water taxiing so much easier.

Those then were the main problems, there were others and all in all it took far too long for a model that should have been quick and straightforward to assemble. I'm just going to make one more point for now though - the floats. In themselves they appear to be okay but how are they supposed to be fixed to wing? One might quickly say glue and that would work but Hobby King do say that the model is intended for field use too - just by removing the floats, erm not if the are glued in! I've fitted neodymium magnets; it seems like a good job but I haven't tested them out yet.

17 April, 2013

Two Tucanos

In 2011 I took part in the Radio Control Models & Electronics (RCME) magazine's website Webbit Mass Build. That was a non-scale model, this year is a stand-off scale model of the Shorts Tucano designed by Nigel Hawes.

I've always wanted one of these, actually I've got another designers rather more scale like  version still in it's box but that's another story. Not content with building one for the 2013 Mass build, I've set out to build two! One as you might expect with a 2 stroke glow engine; the second one though will not have a power source, it will be a slope model.

I'm a bit late getting started and I may have taken on more wood than I shape but I'm going to give it a good run. Since the original design was for electric power there will be much customisation as I go along. The slope version will be built from a laser cut kit and the IC version will be built roughly to the plan - using the kit for templates where possible.

The slope version is coming on well as shown in this photograph.
I have most of the main parts for both models cut out but in many ways that's the easy bit, kitting them out with control snakes, servos, receivers, power and batteries and then the final finishing is likely to be far more demanding especially since the centre of gravity must work out right without having to add too much weight.

Once again RCME Mass Builders will be meeting up at Greenacres near Walsall in June 2013.

The full build story is here.