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Member postings for Devon Slopes

Here is a list of all the postings Devon Slopes has made in our forums. Click on a thread name to jump to the thread.

Thread: Another AB Canberra
06/06/2019 21:05:32

Greetings to two more fellow Canberra builders I have not met before (Paul and Mike). My own Canberra is making slow but sure progress as recorded in my build thread (I'm much slower than Peter Garsden). Like Mike I'm also thinking about a glass finish, but it would be the first time I've done such a thing. How is your's finished Paul?

Thread: S6R receivers
01/06/2019 20:11:12

Many thanks, Mark, for what is valuable information. I still intend to try this, but am currently tied up with other stuff.

Devon.

Thread: Another Andy Blackburn PSS Canberra
01/06/2019 20:06:56

Structure around the incidence tubes and spar. So, here are the inner wing panels almost complete, at the stage of fixing in the spar and incidence tubes. You can see all the strengthening around the tubes Andy talks about. The incidence wires and main spar are slightly over length, I’ll trim them when I know how wide the fuselage is after sanding. You can also see the parallel lines I drew on masking tape on the building board to make sure the wing roots are parallel.

dscf5063.jpg

I made the mistake of scrounging the balsa which fits around the main spar from the wood which the wing tips are cut from, but then realised this must be soft balsa, and so made new ones from some other scraps from the kit. You can also see the hard points for the Multilock wing joiners (one of which has a Multilock plug in it) close to the spars. Also, I have faced the wing roots with 1mm ply. The advice is that this will protect the root from damage, but also you have to force a plastic wedge between the fuselage and the wing to disconnect the Multilocks, and I’d rather do that against ply than balsa.

And this is gluing the main spar to the bottom outer wing skin.

dscf5066.jpg

Thread: Powering X8R servo ports via SBUS port
18/05/2019 19:46:23

Belated thanks for the advice folks.

Thread: S6R receivers
18/05/2019 19:43:22

Many thanks Denis and Til for the advice. This project is on hold for a while, but I think I will start off by trying it on a straight aileron model (my Middle Phase) before trying it on a full house glider. This is because there are assumptions in the software which you have to work around, and so the closer I am to what is expected, the easier this will be. Once (and indeed if) I get the simple case working I can then progress to the more complex ones. My favourite assumption was that the throttle should be low on setup, which for a glider is an amusing concept, especially as I use channel 3 for a lost model beeper! Anyway, I'll write something if I make progress.

27/04/2019 09:02:20

Folks,

has anyone got experience of (or indeed thoughts about) using the S6R or S8R for launching slope soarers? Especially with big models there is that moment when you are recovering from the effort of launch and finding the sticks, and some sort of stabilisation or self levelling would be useful. Should I use stabilisation or self levelling mode? Does self levelling mode try to keep the model at the same altitude (which would be disastrous) or will it let the model slowly gain speed at the expense of altitude (which is what you want at that point)?

I'm just at the stage of having bought an S8R since it was little extra money than the X8R I needed, and worked out that with my old Taranis I have to use model number 8 to get a bind. Next I have to clear my virtual channels used for the trailing edge off channels 9 to 12, and get a firm fixing point for the Rx in the model (previously I've velcro-ed them in). So, any advice gratefully received.

Devon

Thread: Another Andy Blackburn PSS Canberra
08/03/2019 20:38:21

Multiplex Multilocks. A decision almost made. I think I'm going to try holding the wings on with the multilock connectors. I could not convince myself that the magnets would have enough grab (the held 500 grams weight, which is less than my calculation for the likely pull); though they do work for Peter. So, here is the layout I'm thinking of. I have a ply plate that glues onto a former and longeron in the fuselage which holds the barrel of the lock, and a piece of ply in the wing which should transfer any force fairly directly to the wing spar (there is wood to go in above and below the spar, which should help further). I'm going to put the peg into the wing and then try it against a test piece to see if it works. I can't use the fuselage for the test as I don't know how deep to glue the barrel in until I've sanded the fuselage. Thoughts (as ever) welcome.

dscf5044.jpg

Thread: An Electric Blejzyk Mefisto
08/03/2019 20:23:52

My layout IS still nose heavy, David, despite my best endeavours. I'm still trimming but expect I will end up with 20 grams in the tail. The previous electric version I built was done by cutting the front off a slope nose, and that was indeed not circular, which as you say looks slightly peculiar, but only slightly so. Given PatMc's suggestion of routing the wires outside the fuselage, the clever way for anyone else thinking of doing this may well be to shorten the nose as David suggests, and route the wires outside the fuselage if needed.

05/03/2019 19:42:37

Hi David,

750g including a 40g battery, that's very impressive, much better than my 850g, which also has only 40g of battery. How did you do it? Most of it will be the motor, my motor is nearly 70g heavier than the 2826, which sounds similar to the one I used to have, but I only managed to get 90W out of compared with your 150W. One of the reasons I wanted rid of the out runner was the tight fit, problems which you seem to have solved. Did you use the Blejzyk supplied electric nose, or make your own in some way. I'd be surprised if you could get the 2826 in the standard electric nose, which may be a warning for others thinking of this conversion. Do you have a picture?

And to answer your question, if you peer closely at the picture 30/11/2018 I laid out the contents of the fuselage in the order I put them in. Things were driven by my need to change the battery through using the cover hatch, and of course that you want to put the battery as far back as you can. This means it has to slide backwards from the hatch, and clear the servos, which dictates how far back you can put the servos. So the battery ends up under the leading edge. The ESC sits almost directly under the hole in the fuselage the wings fit on top of, and then behind the wing are the receiver and finally (pushed far down the fuselage) is a barometric altitude sensor. And after all that, its still nose heavy!

Thread: Another Andy Blackburn PSS Canberra
02/03/2019 22:08:09

dscf5043.jpg

This is how I opened up the holes in the ribs for the wing joiner tubes from 6mm to 8mm. Because the side of the tube has to just touch the main spar, the centre of the new 8mm hole is offset forward with respect to the old 6mm one. So you can't simply open up the hole evenly all round. So I made two ply templates with 8mm holes made in the right place by comparison with the plan. I then "sandwiched" all the ribs together using the incidence tubes, double-sided sticky taped the templates in place and them opened up the holes using sandpaper wrapped around a pencil.

Note quite as elegant as it sounds, as a little more sanding had to be done to get the tubes in once the inner wing panels had been constructed, but more of that later.

Thread: Canberra by Andy Blackburn PSS
02/03/2019 21:56:13

Many thanks, Peter. I'm still wondering which way to go with this, magnets, multiplex multilocks or tape. A decision will have to be taken soon....

Thread: An Electric Blejzyk Mefisto
09/02/2019 18:25:25

Props.

The biggest issue at the moment is the prop. My local model shop didn’t have the recommended prop, a 6”x4”, so I ended up with a 7”x4” Aeronaut prop. When I run with this on the ground the motor starts off by pulling 16A, but rapidly (seconds) fades to 12A. Of course the prop will be less highly loaded in flight, but I don’t have an ammeter on the telemetry (the FrSky one is too large and hefty). However I do monitor the voltage, and it drops pretty precipitately as you power up. In fact it gets too close for comfort to pulling the battery below 3V per cell. Once you’ve been flying for a bit, the drop is not as severe, so my conclusion is that it’s the 3S 450mAhr battery that’s the limiting factor, and it performed better when a little warm. That was easily tested on the ground by connecting a 2200mAhr battery up instead. Then, as one of my friends would describe it, we were cooking with gas – 18 or 19A draw, no obvious fading with time. Oh, and it pulled like a horse.

So, what to do as there is no way that huge battery is fitting in the Mefisto fuselage? The battery is marked 30C continuous, 50C burst, which translates to 13.5A and 22.5A. I’m not sure how long a “burst” is meant to be (does anyone out there know), but I’d hoped it was a typical e-glider motor run (maybe 10 seconds), but I guess this is just the well-known lesson of not pushing batteries to their nominal spec.

So, I bought some cheap props to try different sizes, maybe I could limit the current draw by having a smaller or finer pitched prop. So far I’ve only done 6”x4” (the recommended size remember), but that was even worse. It started at 16A and faded rapidly to 10A. When I tried flying it the pull was so poor that I was worried about clearing some low bushes as I took off! That to me is a victory for the efficiency of the Aeronaut prop, its bigger than the cheapo prop, has a similar current draw, but more pull.

So, for the moment I’m sticking with the Aeronaut prop and limiting the throttle to about 75%. Now, I recall reading somewhere that ESCs are most efficient at that level, is that right? The summer may improve things – I know my old the old version suffered from large voltage drop at winter temperatures.

Thread: Canberra by Andy Blackburn PSS
09/02/2019 08:45:23

Thanks, Peter. Do you have any words of advice on how to fix the magnets for those of us who've not done something similar before?

Thread: Another Andy Blackburn PSS Canberra
27/01/2019 11:05:20

No, this build hasn’t been abandoned, just that nothing has got done for the last two-and-half months due to other commitments, which included the new fuselage for an electric glider.

The wing joiner. Andy Blackburn says that “if you’re planning to play rough with your Canberra” you should go up a size in the wing joiner. Slopes Junior thoroughly enjoys his slope aerobatics, so I suspect I need to do this. The standard joiner is 6mm OD carbon tube with 4.5mm carbon rod inside it, so I’m going to 8mm OD carbon tube, with 6mm carbon rod. This means I will have to open out the holes for the joiner in the wing ribs.

dscf5022.jpg

Attaching the wings. I’m also wondering how to attach the wings onto the fuselage, which Andy recommends doing by tape, but says you can also do it by using a Multiplex Multilock plug and socket, but if you do so you need to make hard points to put them into. Not quite sure what this involves, but it looks like I need to work out how to do this before I complete planking the fuselage. So, I’ve dry assembled the starboard wing laser cuts parts so I can see what’s going on. It all seems to go together nicely, though you have to make another rib R4, which is easy to do using the sandwich method, with the laser cut R4s as the templates.

Thread: Canberra by Andy Blackburn PSS
26/01/2019 16:51:57

How did you hold the wings on in the end, Peter? Earlier in the thread you mentioned some wing retaining plugs, and I was thinking of going a similar way, rather than putting tape along the join. But, Andy B. suggests some strengthening around the plugs if you go that route, and I was wondering what you had ended up doing.

Thread: An Electric Blejzyk Mefisto
26/01/2019 16:31:07

dscf5021.jpg

(Does anyone know how to rotate a picture?)

And here is the completed model. You can see the hatch, secured in the traditional way using wire epoxied to the inside. The nose area looks empty, as all the gear is as far back as possible, and the battery slides over the servos to sit well behind them under the leading edge of the wing. I’m fairly sure it is nose heavy, but have not yet started seeing how I can improve the performance by adding weight to the tail.

The all-up weight is about 830g and will probably go to 850g when its trimmed. That’s a bit of a disappointment, as the old version was 750g. On the other hand its really nice to operate, not having to take the wings off to change the battery (and worry about flexing solder joints on plugs so they break). Furthermore, its easy to change between electric and pure glider, just take the wings and tail off one fuselage, and screw them onto another. The old method of changing the nosecone was difficult, and stressful on a Saturday morning when I’d decided to go flying, but then had to spend 20 minutes changing the Mefisto into the appropriate mode.

I’m still fiddling to obtain the right prop, but more about that in a later post. But it has answered the problem about power. I well remember the first time Slopes Junior saw the old version of this model working. I opened the throttle and he said “Is that it?” in a derogatory reference to the power output. Those days are gone.

30/11/2018 19:01:28

dscf4783.jpg

Here you can see the electronics laid out alongside the fuselage in roughly their intended positions. Starting at the front is the prop and motor, then come the servos placed in the tray I’ve made for them, and the battery which will go behind them. Next is the ESC, hidden beneath which is the battery voltage sensor. This is followed by the mass of wiring for the multiplex connectors which go to the wing. Finally comes the receiver, and variometer. The two small black rectangular bits, one amongst the wiring and one beyond the variometer are the aerials. The whole layout is about getting as much weight aft as possible, though I believe I am still going to end up with tail weights.

An unexpected time sink was making up the cables. Its the first time I've crimped up lots of cables for a model, but I think it has really paid off in terms neatness and compactness because all the cables are the right length, no excess lengths being pushed into spare space.

Thread: Powering X8R servo ports via SBUS port
09/11/2018 08:12:59

I've finally filled up all the available servo connectors on an FrSky X8R by adding a tow release to "full house" glider (it also has a lost model alarm). Now, whilst I could power the rx by putting a Y-lead on one of the servo sockets, that SBUS (or indeed the RSSI) socket looks very tempting. I opened up the rx to check if it was on the same positive and negative buses as the servo ports, but its hard to tell (I suspect connections are buried in the PC boards somehow).

So, my question is, has anyone powered the servos connected in the normal way to the X8R via the SBUS or RSSI ports? Or, does anyone know if the internal connection of the SBUS and/or RSSI ports is similar to the one between the servo ports.

Thanks, Devon.

Edited By Devon Slopes on 09/11/2018 08:13:37

Thread: Canberra by Andy Blackburn PSS
07/11/2018 07:29:49

Many thanks for linking the videos, Peter. Inspiring me to continue my build, I just have to complete the changes I'm making to an electric glider first.

23/10/2018 19:47:37

Well done Peter. Encouraging to hear that it flies well in modest winds. I do hope you find some pictures of it flying to post.

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