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David Hall 9

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  1. David Hall 9
    I found this in a thread elsewhere. It explains the reason for the changing section. " Dr Drela designs airfoils for particular Re operation ranges, which is one of the reasons he uses different sections along the span of a wing. As the cord shrinks and the Re gets smaller, he uses an airfoil optimised for that range." These are fine design changes indeed. So, if I were to adhere to this idea, then my scaling up of a wing that uses a range of AG airfoils by ~25% might change the airfoil sections to a new set of AG airfoils.
  2. David Hall 9
    Posted by Dickw on 25/04/2020 12:39:50: A linear change between sections along the wing is one possible option (and perhaps the most common), but that it really is up to the designer and that depends on what he hopes to gain by using the different sections at different locations. For example, you might use a thicker tip section to try to avoid tip stalling or a thicker root section to give added strength. Not saying either would work - just simple examples. Sites like Airfoil Tools allow you to compare how different airfoils work. Go for it - and lets us know how you get. Dick Thanks Dick, I am considering building a scaled-up version of a glider that I have at the moment. As you say, altering the thickness of the airfoil is something that I might expect. I will have to dig a little deeper. I guess that the different sections incorporate similar features and advantages when compared to simply altering the thickness of a single section.
  3. David Hall 9
    On quite a few gliders, I have seen the wing section quoted as, for example: "AG35-36-37". I guess that this will mean that it varies linearly along the wing...is that what it probably is? is there a design convention for the way this changes? I am considering having a go at glider wing design and wonder how to incorporate this feature.   Edited By David Hall 9 on 25/04/2020 12:11:25
  4. David Hall 9
    Good info... Have you balanced for the CoG yet, having used a motor much heavier than the Hyperflight example? Mine has come out of the box again.. adding wiring then to be covered.
  5. David Hall 9
    Posted by Erfolg on 21/04/2020 13:59:01: ............................. Yet for performance a model glass ship beats anything I have ever built hands down, leagues away in all aspects of performance, if I only had the money.   Apologies, not directly related to the OP, but this comment from Erfolg stirred my enthusiasm..... Last year, I became a bit more serious about competing in F5J and decided to move into open class. I had completed with 2m models and had enjoyed it, but noted that even my 2.5m ship would seem to handle better and (apparently) outperform the 2m. I am building a 3m balsa glider (nearly finished) but in the meantime, I bought a competitive, well used CF 3.8M ship. I have begun to regret my purchase (buying into this a bit too heavily) and have thought that I should stay with my smaller models... I've heard one or two others mention the performance levels of the CF moulded ships, Erfolg's comment reminded me of these... Perhaps, if I am lucky enough to survive the virus, I should at least have a go with it.. If I don't survive it, my wife might sell it for half of what I told her I paid for it. Edited By David Hall 9 on 21/04/2020 16:53:00
  6. David Hall 9
    Thanks for your suggestions.... Looking at the connectors I have to hand, the MPX 6pin looks to be superior to the JST for this purpose. With a little enlargement of the hole, I could use them for the wing outer to centre join. I can leave the main wing to fus connection until later, so a MPX 8 pin or a 9 D type could be used. I recall seeing that many of the CF moulded F5J gliders use this connector in the wings, so I don't have any worries about overrunning the current spec when on this particular model. This allows me to continue the build for the time being.
  7. David Hall 9
    Posted by MaxG on 21/04/2020 13:45:58: Have you tried **LINK** or **LINK** . Alternatively 4Max do multi way connectors now. Alternatively what about 9 pin D sockets. Maxg Thanks for the links.... wow, Multiplex-rc.co.uk, i had no idea. They didn't pop up on my searches. You would think that would be exactly the one... they do the 5 pin socket, but not the plug, as far as I can see, and no 8 pin. The other links to a shop which, like others pops up on my searches because they have the usual 6 pin connectors. But... Nexus models have the 8 pin and are "open" on-line. I have been thinking of the 9 pin D type, that would be a working solution.. I can use the MPX 6 pin for the wing panel connections, the 4 pin JST connector (lipo balance) will be a better fit, if it is reliable... I've never had a problem with the battery balance connectors I use, other than the time I flashed the pins off.
  8. David Hall 9
    My lock-down build of an "Inside F5J" kit has been going well, but is now stalled for the lack of some connectors. Ideally, I'd like an 8 pin Multiplex plug/socket for attaching to the fus (it's a six servo wing) and Multiplex 5 pin (or 4..) for the outer wing panels. At the moment, I am considering the use of a 3S battery balance connector and a 6 pin MPX connector + a JST 2 pin power connector for the fus connection. Does any know of a source for the MPX 8 & 5 pin connectors that can supply?   Edited By David Hall 9 on 21/04/2020 12:39:48
  9. David Hall 9
    I have a need for some balsa strips, and I have a balsa plank that has been in my loft for around 20yrs. It is an offcut from wood used to build theatrical sets. The plank is about a metre long, 100mm wide, is bowed in both length and width and varies in thickness from around 6mm at the ends to around 12mm in the middle. I have 3D printed a balsa stripper and will soon set forth on a stripping andventure, trying to produce a variation of balsa strips... just as soon as I work out how to start on a 6-12mm sheet with a stripper that can manage 6-7mm thickness. Some of the strips will be used as longerons and tips for a vintage model, the wood will be steamed to get it to bend (another adventure for me).
  10. David Hall 9
    I recently bought a complete model Ballerina, it's very nice indeed. It looks to have been built by someone that knows how to do it.... but, it has an OS40FS surpass fitted... I wondered if that is enough to rise off grass.
  11. David Hall 9
    Thanks for your input... I like the shape of the Hep Cat (and similar). Although I am thinking of adding ailerons, it doesn't necessarily follow that I must throw it around like a Wot4. I'm looking for a more gentle and slower experience. At best, if it flew in a similar manner to my F5J models (aileron equipped E-gliders), where it could use aileron and/or rudder for gentle turns, I would be very pleased. It will have some other significant changes from the plan version. I hope to keep the vintage police away by having it look the part, even if it is likely to be covered in film (another no-no, I guess) and have radio control.
  12. David Hall 9
    I am toying with the idea of building a scaled-up version of the Hep Cat from a free plan for a 46" version. I am trying vintage airframes for my first time, but I have an electric Junior 60 awaiting a maiden flight, which I am looking forward to. As I might not really take to a three channel plane (the J60 might be enough for that), I am thinking of making the wing as a flat, aileron equipped version. A flat wing will look odd, I guess. What small dihedral can I use (simple straight wing panels) that will look more pleasing but not create control problems?
  13. David Hall 9
    Posted by PeterF on 04/04/2020 21:08:10: The HT PLA is I believe the same as the PLA plus I mentioned above which the Stearman was printed with, I used eSun brand. I have printed ABS on my Anycubic Mega S but it needed a bed temp of 105 degC to stop lifting and the only way I could achieve this temp was by placing some sheets of cardboard around the machine and one on top to make a sort of enclosure. It still had some gaps in so it did not get too hot inside, it just stopped most of the air movement. Yes, I guess that to print ABS, some way of raising the bed temp is useful if it can't maintain it in the open... My machine is the Mega M, so similar issues for ABS I guess. The Stearman looks fantastic... I'd like to know how it flys (and how it bounces), when you manage to try it.
  14. David Hall 9
    Thanks for your input guys... I had a sample of no-name ABS and printed a rib at typical ABS temps. About half way through I noticed it had lifted at the ends and across its width. I guess that bed temp is critical, mine struggled to maintain 85c in an open environment. I hadn't heard of high temp PLA and searched for some spec....it does seem to be one good way to go. I also found some info on annealing the PLA parts which gives almost amazing results... It may not be an issue at all if the models are sensibly treated and there are means to improve it if I think that it needs it.   Edited By David Hall 9 on 04/04/2020 20:09:26
  15. David Hall 9
    Just a little care needed in avoiding leaving them somewhere too hot, which is what we all do anyway, I guess.
  16. David Hall 9
    Wow... that's something to avoid! I haven't printed ABS yet, because so far, PLA has done a good job, but a flat rib is probably as easy a print as can be done, I can try it... Is ABS much better for heat problems?
  17. David Hall 9
    I'm about to build my first wing using 3D printed ribs in PLA. Has anyone used such a wing in strong sunshine. I'm wondering if the ribs might soften in the heat. I guess that I could cover the open structure in transparent or solid coloured film, if that makes a difference.
  18. David Hall 9
    Love these articles, please let us see your build log etc..
  19. David Hall 9
    I see your disconnect now... in the red lead.       Edited By David Hall 9 on 31/03/2020 17:49:18
  20. David Hall 9
    I noticed that your UBECs are wired in parallel  (even more if the ESCs are supplying power too). This is something that I plan to use when I next need to supply more power than one BEC can provide. Not all BECs will do this happily, I understand. Have you tried this on the bench?     Edited By David Hall 9 on 31/03/2020 16:55:40
  21. David Hall 9
    Posted by FlyinFlynn on 31/03/2020 11:18:36: ........................................................ David...indeed...and as soon as you think you have got it something changes! You seem to have a large 'elephants foot there on those ribs, maybe your first layer height is too low or it could be your first layer extrusion level is too high!..either way, changing them could impact the part cohesion to your print bed so perhaps the best 'cure' would be to add a very small radius to the bottom of the holes to just reduce the 'squish' right on the edge...that way the adhesion will not noticeably be impacted. Conversely...you can see a couple of holes in the plastic where the infill is supposed to touch the hole walls..this is a touch of under extrusion - I would try increasing the extrusion rate 1% at a time until it stops. This may well change when you change spools. Edited By FlyinFlynn on 31/03/2020 11:21:40 Yes, i know what you mean, the "flange" around the entire piece.. This was my first part printed with an offset for the "elephant's foot"... I added 0.5mm when it now appears that I should have used a negative value.... every print is different! So far, so good. I am really pleased with the last couple of day's efforts. They will make very practical ribs, they glue well with cyano and gorilla glue... The holes in the print appear where the infill meets a wall... there's an adjustment for that.. overflow or some such option. More to try.....however, the ribs are good as they are, so it's a minor issue for me.
  22. David Hall 9
    Posted by FlyinFlynn on 30/03/2020 09:58:11: Very nice David, I would suggest you add a chamfer to the underside of the lightening holes to combat the elephants foot and add just a touch to your extrusion rate as that last rib looks a mite under extruded. ......................................................... Thanks, 3D printing presents a challenge to get to grips with all that's happening. Interpreting the myriad of options within the slicer settings is a slow process, especially when determining what features and faults can be overcome with what option. It can be a complete hobby in itself.
  23. David Hall 9
    For me, a trad, vintage build using anything I can utilise... ply, foam sheet, printed plastic parts, CF, even some balsa.... A vintage flyer, Hep Cat. (downloaded plan).   Edited By David Hall 9 on 30/03/2020 10:01:03
  24. David Hall 9
    Thanks for your help and suggestions guys... I have a small collection of trial rib prints. It was a good exercise, several new things learned and gathering more experience on the 3D printing side is a plus. Now I have a workable (simple) design for the rib for this project. 2mm thick, 3g and in my wife's favourite filament colour...
  25. David Hall 9

    David Hall 9 posted a gallery image in Member Albums

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