Radical Dude

...thats hot!

Following on from the successful motor transplant in the Radjet, I wanted to give its very-battered nose a bit of reinforcing, consisting as it did of fragments of foam superglued and bounded by tape, which basically holds everything together. Due to missing bits, however, superglue wasn't really working anymore, however I had a great idea - hot melt!

I have tried this out and it worked brilliantly - basically I have injected all the cavities between the foam pieces full of hot melt which, due to its bulk, fills the voids and bonds everything together. So now the Radjet nose is about as rigid again as it's ever been, although still not quite as pretty as it once was.

I've also wanted an easier way to fit the chubby 4-cell batteries as, in the past, I've had to forcefully ram these into the fuselage. Having some unused hatch hinges and some recently arrived, and long overdue, magnets I've decided to make a battery hatch a bit back from the canopy opening.

So far I've just fitted the hinges to the hatch, then I'll glue this to the fuselage and finally install the magnets, probably hot-melted in place and covered with felt tape to prevent them pulling out.

That will almost complete a substantial overhaul of the high-flying speedster, the last thing it needs in a canopy. If only they stocked spares for the 800...

DX6i Differential Thrust

...who needs a rudder?

Searching for a solution to the Canadair's pathetic rudder, I happened across some forums discussing differential thrust as a solution to replace rudders, with posts indicating that this thrust solution in fact outperformed conventional rudders.

The idea is that, instead of having two motors always producing the same thrust, when you turn you programme your radio so that the "inside motor" reduces power which assists with the turn. This is particularly desirable in the case of water planes where the plane rudder alone is usually insufficient.

This immediately piqued my interest as a potential software solution to the hardware issues I was facing. If successfully implemented would also allow the rather prone rudder to be removed to the parts box.

There was a minor glitch, however, in the case on the DX6i (and perhaps DX7 as well), as I will explain. The full solution requires three mixes to be used, one to allocate a new channel (usually auxiliary/flap channel) as a second throttle channel, and then two additional mixes which link the two throttle channels to the rudder, thereby allowing the appropriate engine output to be reduced to effect turning (turning right reduces right engine power and vice versa). The issue is that the DX6i has only two mixes available.

Fortunately I came across a forum, including a post by constantmotion on this specific issue, offering a novel solution working within the limits of the DX6i as quoted below:

Mix 1:
Thro -> Flap
Rate D -100% U -100%

Mix 2:
Rudd -> Flap
Rate D +30% U +30%

"If you go into the Monitor mode you can see how the mixes affect the channel outputs. The left motor ESC goes into the throttle channel, and the right motor ESC goes into the Flap/Aux channel. This is important; if you plug the ESC's in reverse your differential throttle will be backwards. 

The first mix makes the flap channel parallel the throttle channel for throttle control, and the second mix causes the flap channel to vary depending on rudder position. Changing the rate on mix #2 will affect how much differential throttle you get while turning."

I've tried this on the Canadair and can happily confirm that it works. The only thing I would add, as I discovered, is that the ESC from which the red wire has been disconnected (as apparently you must with multi-engined aircraft) must be connected to the auxiliary channel, while the full lead is connected to the throttle channel.

I happened to have it the other way around and ended up with one lifeless ESC bleeping plaintively until I figured out what was the problem. As my motors were then swapped, I fixed the issue by making the percentages in Mix 2 negative.

The difference between constantmotion's solution and the 3-mix version is that only one motor gets variable speed, increasing or decreasing as per the percentage set in Mix 2. The only time this would not function is if you were turning away from the aux motor side on full throttle, in which case the aux motor would, of course, not be able to speed up.

I have conducted a bench test of this system and it shows potential, but am hoping to do a water trial soon to confirm just how effective it is. Hopefully it will work sufficiently well to allow me to dump the rather underwhelming original rudder...

Canadair on the Water

...just weeding out problems

Yesterday was the first opportunity to get the Canadair 415 onto the water but unfortunately things didn't go well, to the degree that the Canadair didn't even come close to getting into the air, which was rather unfortunate as it was a spectacular afternoon for flying.

The first issue was the rudder, which proved almost immediately to be bordering on useless. It appears the thin wire mechanism, incorporated into the tail assembly, is much too lightweight for the job, so the Canadair ended up drifting rather aimlessly around the lake and ending up having to power it through the water weeds as steering it back wasn't an option.

Fortunately, as we know, the Canadair has a surfeit of power which saved it from the indignity of being marooned on the water. This was all the more impressive when one saw the amount of marine foliage that the fixed rudder had gathered as the plane trawled through the weeds.

The second issue was that one wing was heavier than the other so that, despite the plane accelerating on the water, I was unable to get the wings levelled. As a corollary, with the float stuck on the water, the Canadair was progressing in slow circles.

I eventually gave up and ploughed it back to shore. The wing balance is a relatively easy fix, however the rudder function is a more taxing issue altogether, and something I'll have to do some research on...

Funfighterjet

...radical

A while ago the Radjet slowed down a bit, becoming somewhat pedestrian to fly. At this stage I decided to do a battery swap with the Rarebear and run the Radjet on 4S battery instead; the little buzzy being alarmingly fast flying on the high-voltage pack.

Recently, however, the Radjet suddenly regained its mojo and became seriously fast, carving up the sky in a most endearing manner. Unfortunately, this resurgence of speed was short lived with the Radjet reverting to its previous underwhelming state. The bearings in the stock motor being the main suspect.

However on my spares shelf I happened to have a spare Funfighter motor whichwas too good to resist as a parcel-filler with a previous purchase. Deciding this was the time, I set to stripping the old motor out of the Radjet.

This is a relatively simple process although, with the motor mount being bonded in as part of the rear fuselage section, you have to rip it out which is not great. However it came out easy enough nevertheless.

A few minor complications surfaced; the Rarebear motor requiring two sized mounting screws, M3's and M2.5's and, while I had some of the latter, I had none 30mm long so had to improvise somewhat. Also, the Funfighter motor comes with mini-bullet connectors, however I unsoldering the 3mm connectors from the stock motor and fitting these to the new unit solved that hiccup easily enough.

So the Radjet is now all set up and waiting for the glue to dry before I take it out and give it a good blast around the paddock. I'm looking forward to that...

Turnigy Thrust Test

...the Canadair's cooking

Following my concerns regarding the Canadair 415's prop size, or lack thereof, I conducted a rudimentary thrust test using a scale. First up, the Canadair weighed in at 1.25kg all up including a 2200mAh battery.

The Canadair sounded quite impressive running up to full power, with the scales indicating it was developing somewhere in the region of 1.6kg thrust, close to the quoted maximum of the Turnigy L2210's and more than adequate for getting the water bomber into the air...

Performance Anxiety

...how big is your prop?

The only minor concern I have regarding the Canadair 415 is whether the props are sufficiently large; I traded in the 8x3.8 slow-fly props for three-bladed 7x4.5's following the methodology of dropping one size going from two blades to three. However, in this case, the original prop is a slow-fly paddle version, so I'm thinking that going for a regular eight-inch three-blade would have been a better equivalency. 

Anyway, I might do a power test on a scale just to get a rough idea of how much thrust to expect; the 210W bell motors are rated at a max 880g thrust which, pushing the lightweight Canadair 415, would probably give it unlimited vertical performance...

Canadair 415 Ready to Roll

...at last

After a long and tedious episode of head-scratching and problem solving, the Canadair 415 is finally ready to fly, and it looks great!

Hanging in the study it exhibits the nose-down attitude with which I believe it flies, and the metallic spinners finish it off beautifully. Having read some discussions, I finished it off with a clear enamel spray as the foam is a little dry and I'm sure prone to staining, especially as the lake where I fly is actually a stormwater basin...

Searching for Slopes

...get the gliders soaring

I have lately been searching for places to get the gliders soaring instead of just cruising around; more what they're supposed to do. However, unfortunately, good soaring sites aren't to be found in suburbia so I've had to do a bit of searching.

I took the Phoenix for a fly to a great slope soaring site, unfortunately having literally zero wind meant it was just a regular flying session, although with a spectacular panoramic view. Hopefully I'll get to return when the breezes are favourable...