Pond Landing

I’m back in the air again! Seven flights with the Mustang, and one accidental landing in a muddy stream.

It was rather windy this morning, certainly at least 20 mph, but for periods of time the wind would drop back to nothing and I could enjoy the wonderful sunny weather and clear blue skies. I thought I was going to be on my own at first, but I was joined by one guy I haven’t seen in a while who has a Mavic Mini and the other guy I know with the DJI Inspire. There was another rogue drone at the end of the morning, but I have no idea where he was actually flying from.

The conditions were rather challenging, despite what it looks like in the photos. I did some trial runs on my first flight to simulate the ESC cutting power and how I could bring the plane down safely in the wind. This is the thing I like least about the Mustang. When the ESC cuts there is no way to re-arm it, so when it cuts you’re coming down. However, on the first flight, after shutting the power off at height as a test, I witnessed the aircraft travelling backwards at quite a rate of knots. OK, so if the power cuts then all I can really do is point it downwards at a sixty degree angle. Yes, I really mean sixty. So, as the power gets used up, keep the aircraft near to me and maintain some height just in case. But, basically, don’t run the power right the way to zero. Most of the flights I was quite good and waited until 10 minutes, after which I landed on the first sign of the wind dropping, but not exceeding 13 minutes. However, the charge held by the packs can vary, and I got a bit distracted on a couple of the flights, so ended up landing dead stick.

It’s funny, but whether the conditions were affecting the aircraft’s trim, or whether it just hadn’t flown for a while, I don’t know, but I had problems doing loops and coming out on the same heading. What I normally do is to kick in a lot of left rudder as it goes over the top, which used to give me perfectly straight tracking on the loop. It just wasn’t working at all this morning, which is weird. I also did some extended flying on manual mode with no gyro. It was hairy, but I did loops, left rolls and half cubans, but no right rolls as its right roll rate is so slow as to be dangerous. I was still over controlling all over the place, but that might just be because these were my only flights so far this month due to the horrendous weather we’ve been having.

And then we come to the final flight, which was going great right up to about 1 second before landing. I got distracted and messed up the timing, which I only realised when the motor cut out on me. This was not in the best place to line up for a landing and the wind was blowing a gale. The problem was that I was heading directly for my bike and the bench, with the wind tending to push it towards the sign board that stands behind the bench. Due to the lack of power there was no real way of going around and the two targets were too big to just sideslip and miss. That was fine, though, because my track was right between the two obstacles, looking to land on the safe patch of grass about 10 metres square right in front of my feet. There is a small stream of flowing water going left to right in front of me which the aircraft has to cross, but that’s fine because my descent angle is going to bring it right to my feet just like normal. Except that, as the aircraft crossed the water about 5 metres from touchdown, the wind dropped. And so did the Mustang. The sudden loss of wind and loss of air speed over the wings caused it to stop flying at that point and fall like a stone straight into the muddy water. Oh, well, I’ve seen that happen before with much worse results. I crashed a glider many years ago when the same thing happened, but at flying altitude and with power still available. That was the second last flight of my old SonataE electric soarer, which I badly damaged and had to rebuild the wings of before flying it again, just because I couldn’t bear to see it finish like that. At least this time the Mustang only got wet, so I’ve put it in the sun to dry out a bit. It all looks fine, though, and everything is still working.

The building of the Mustang’s successor is still progressing. I’m onto the horizontal tail now and making bolt fixings. I need to glue the plate that holds the tail to the fuselage, so that’s tonight’s job. I must be nearly finished then, apart from covering? This is the classic, “the last 10 percent takes 90 percent of the time”. I’m really bad at converting “nearly finished” into “finished”.

45MPH!

The wind is gusting to 45 MPH today. And that’s nothing compared to a few days ago when it was 80 MPH. My little Mustang has a flying speed somewhere under 20 MPH, so that’s not going to happen. The weather in February has been horrible so far, but it has given me time to do some building.

Well, that’s progress so far. A profile Cap 10 (sort of). I spent last night covering the nylon bindings on the fuselage joiner tubes with epoxy to make them strong. The doubled 3mm ply sheet (=6mm thick) that supports the wings originally weighed 20g, which I thought was really heavy. I then spent the whole week drilling lightening holes and fitting the wings, getting the final weight down to 15g. Then I added the epoxy to the joiners and added another 10g of glue. Great, it now feels really heavy, but then maybe that’s just because the fuselage framework weighed virtually nothing before I added the structural items. It weighed in at 85g fuselage, 70g each wing (with one servo each) and 28g tail and rudder. I’m sure there’s a way of building this lighter, though? After I added up all the component weights last night, it looks like my target flying weight is about 440g. Now, that’s suspiciously close to my profile foam RS352, which, I think, is about 450g? I shouldn’t be surprised really, as they’ve got virtually the same equipment in them, although the RS352 is a little bigger. All the removable pieces really add extra weight, but I’ll be perfectly happy just to see it finally take to the air. This can be version one, after which I can refine the design bit by bit as I go along.

Now, I’ve got a bit of a problem because the next part involves cutting the fuselage in half to allow it to pack down for transport and mounting the removable tail. The cutting in half should be easy, so that’s getting done tonight. This will be my first opportunity to see if those carbon tubes do their job properly and hold the fuselage together. As for the tail, however, I’m wondering what angle to set it at? Normally, I would calculate the angle, but the wings are foam board, wrapped around using a technique that I saw on flitetest.com. The problem is that I don’t have any polars for them so I don’t know what angles to set everything at. The wings vaguely resemble a Clark Y with a flat bottom, so I’m going to use that as an approximation. At least that’s the angle I’ve used to set them to the fuselage so that they produce the correct lift to fly at my target flying weight and speed when the fuselage is aligned with the airflow. The tail is a bit trickier, though. I was thinking about trying to run the profile through XFoil to see what I get, but, never having done this before, it might be beyond my skills. I’m fascinated to try this, though, as I can then simulate the plane a lot more accurately. However, I may just guess at 4 degrees, because that works for most planes. Also, the tail mounting means that I can add a shim and adjust it if I need to.

OK, so tonight’s work is as follows: cut brand new fuselage in half, mount tail, simulate foam board wings. It’s probably a bit optimistic to say that it could be ready to fly by next week, but you never know?

Flying would depend on the weather changing completely and so far February has been a blow-out and a wash-out. Next weekend is the last weekend in February to salvage any flying for this month.

Where is the Rain? And Some Building

Where was all the rain this morning? Admittedly, the forecast was very hard to interpret, but it looked like we could be expecting heavy rain that was going to last for hours at around 10am. Although the morning stayed dry and the rain didn’t actually materialise until about 1pm, it was threatening to rain all morning and blowing a gale. It’s now late in the evening and it’s still raining, so it hasn’t been a day for going out.

No matter, I’ve spent the day building, as you can probably see above. My Dimension profile aerobat has now been lifted off the building board and I’ve been adding the cotton thread that secures the paper tubes holding the carbon rods, which is the most critical part of the whole design. Once these are in place, the fuselage gets cut in half just behind the canopy so that I have two bits of fuselage that will fit in my ruck sack easily. Mind you, if I had realised just how long binding those joiner tubes was going to take, then I might have found a different way of doing it. The idea is genius though, even if I do say so myself. The carbon rods double up the spruce centre spar on the left and right sides of the fuselage making a nice stiff fuselage which splits in two for transport. I’ve just spent about an hour threading up to the half way point, so I’ve got a fair bit longer still to go. This threading is quite therapeutic though. And I’m filming it as I go along, so I should hopefully have enough bits to cut together into an entertaining video. I’ve cheated on the threading though. It takes so long that I’m just filming sections every so often as the thread makes its way along the fuselage. I don’t know how it’s going to look on the screen, but that’s all I could manage. I’ve still got quite a lot of work to do, so it’s going to be a late night.

Although I’m only part way through my current build, I had forgotten just how much I like building in wood and I’m already thinking about my next build. Going back to the 1980s when I first started flying, I remember my friend buying himself a 2.5 metre Algebra. It’s so long ago that I can’t remember whether he ever actually finished it and flew it, but I do remember the day we went out and bought it and sat on his living room carpet making the fuselage. I distinctly remember him getting it back home and wanting to build it immediately, so there we were with two sides of fuselage and doublers being glued in when his dad comes in and says, “why have you made two left fuselage halves?”. Oops. More haste and less speed next time, but I’ve now got rather obsessed with building a smaller version and making it electric. Really, I just want a small glider for summer flying, but I love the gull wing shape of some of those old gliders. Now, some research on Dick Edmonds Products (EMP) and Algebras shows that there’s been a bit of a resurgence in the design in the last few years. There was a build thread on the BARCS site and some fantastic videos. It seems that the basic Algebra design went through lots of changes over the years, resulting in a plethora of different variants. My friend’s one was the 2.5 metre with the fibre glass fuselage, but they started out with rolled ply fuselages. There are smaller versions too, with the 2 metre one having straight wings which were swept back. The fuselage is basically a stick with a straight edged bottom and a fin sticking out the back. I’ve also read that the wing sections varied between S3021, E205, and E193, with other suggestions of RG15, MH32, HQ1.5/9 or SD6060. There are plans available, so it’s very much an open source design. The originals were designed to be simple to build and fly after all. This is really going to have to wait until after my current build is finished, though.

So, there were go, one aircraft at least half way to finished and I’m already thinking about the next. I really have missed building aircraft. I don’t know why I didn’t do it for so long. And with that, I’m off to bind the rods into a plane. Here’s hoping for good weather next week, as it’s been a while since I missed two weeks running.

Wild Weather

Wow! That’s a sky I want to fly in.

There was no flying this weekend. Although it absolutely hammered down with rain all night, by 10am it had almost stopped and sunshine had broken out. Looking at the image above, what is not apparent from the still is that those clouds are moving appreciably fast. The lower level rain carrying clouds moving at speed beneath the seemingly stationary high level clouds. The wind was gale force, so it was not the sort of weather to be flying a UMX plane.

I had planned a building session instead…

Can you guess what it’s going to be? It’s not the greatest photo, but it’s my slightly modified Cap 10 B, as a profile plane which I’ve called “Dimension”, just because it lacks one. The photo makes it look really short coupled, but it never looked that way on the plan. Perception is a strange thing, but it’s designed to split in half right down the middle so I have two 40cm sections which will fit perfectly in my ruck sack for transport.

I’ve decided to film the build, although I nearly didn’t bother because of the difficulty, set up time and just the sheer amount of planning and effort that it takes. Have a look at the next picture and you’ll see what I mean.

In order to build, I have to manoeuvre myself around the camera position. Also, the lighting is terrible. I need to get a proper lighting rig if I’m going to do any filming in the evening, which is the only time I ever get to do any building. And then there’s the reflections and shadows. I gave up trying to fiddle the lighting to get rid of the tripod shadow on the work bench. Also, once you cover the plan with plastic, that’s just one huge reflective thing that ends up putting bright highlights where you least want them on the video. Just trying to fit and glue all the pieces together is hard because you can’t see what you’re doing. Of course, once it’s done it’s done and you can’t do a second take if something went wrong because it’s glued. You have to plan your shots and your build in meticulous detail. However, I’m obsessed with the idea of showing the build right through to the point where I throw it into the air and it flies. Hopefully this one really is a quick build as I’ve only spent two weekends so far and I’ve nearly finished the fuselage and tail. As we all know, though, it’s the little bits that take the time and I’m currently working on the carbon tube that allows the fuselage to split.

That’s all there is this week as I’m going back for another few hours of building before the working week takes over again.