9 Comments

The BD 5 is a very small one man jet made famous by appearing in the James Bond film Octopussy. I like the look of this chubby little plane and found a set of plans on the interweb which I download as a pdf file, Chris got them printed up onto A1 size paper and so this is my blog of the build. This is what it should look like when completed. DB-5   The model is to be made entirely from Depron and is pusher prop driven . The guy who designed this model has made his own blog of the build, I download this to my printer and am using it as a building guide.   I wanted to try and preserve the set of plans so I brought tracing paper and traced around the drawings, I then stuck the tracing paper to the Depron sheet using masking tape and with a sharp blade followed the lines I`d drawn, cutting through the paper as well as the Depron to produce a set of parts. This blog wasn`t going when I started so I have no pictures of the internal formers before they were put together, however I have taken photo`s, although due to lack of light and a decent camera, they are not best quality. I`ll try to do better next time. I`m using a glue called Foam to Foam and a small amount of epoxy to sick this thing together, the Foam to Foam works well on Depron but it is expensive to buy.

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This shows the main body of the model with the horizontal tail plane fitted, I decided to put a balsa platform to strengthen the nose area as this will carry the flight battery.

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This shows the tail plane with rudder fitted, it`s connected by a fancy shaped torsion bar arrangement, you can`t see this very well (crappy photo). 100_0004 (640x360)

Here the wings, they also use a torsion bar system to operate the ailerons. 6mm carbon tube has been used to strengthen the wings, these stuck in place using epoxy. All of the cut out parts have fitted together quite nicely and I have not needed to fiddle about trying to make them go together.

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Now I have fitted and glued on the tail, there is a slight misalignment at the back end but I think I can live with it. Also the wing have been pushed into place but not fixed while I connect up the aileron linkage, this is fiddly and time consuming, once I`m happy with this I will fit the ailerons which you can see behind the model. I  have a small problem and have to make a decision, this is a pusher model so the distance between the motor at the back and the battery at the front is quite large, I will have to extend the ESC cables but which side to I extend?, the motor side or the battery side?, I will hopefully get some advice on this please feel free to comment. Well that’s as far as I`ve got up to now, and will add to this blog as I progress.

UPDATE

I have decided to extend the motor side cables, after looking at various forums, the opinion was that to extend the two battery cables could cause damage to the esc input capacitors, while extending the motor cables may cause timing problems due to the cable length affecting the back emf needed by the esc. This was the lesser of the two evils and the model designer also went down this route, and that’s fine by me.

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I have fitted the servos, connecting up the aileron linkages was fiddly as I thought it would be but got there in the end, once the fuselage top and bottom have been fitted there will be no access to any of the control surface links or the servos, again something I`ll have to live with. So the receiver was fitted and bound and all control surfaces found to be working and adjustments made.

I then fitted the top and bottom of the fuselage, and the front nose block.

There followed an awful lot of shaping and sanding of the model, two things here, the nose block was made from several pieces of depron laminated into a block then glued to the front of the model, because depron is so soft and because of the laminations it is difficult to get a smooth finish when sanding, next time I will use a block of balsa wood for this. Also due to over vigorous sanding and again the softness of depron it was to easy to damage the model, making holes in the surfaces that were adjacent to the ones being worked on. Some light filler was used to correct this.

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This is as far as I have got now, the model is complete and is waiting for a top coat of paint.

further  updates will follow.

UPDATE 2.

Well it`s finished, just need to set the C of G and make sure everything is still working.

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Thanks for following this thread.

Mel.

 

  1. Scott says:

    That’s coming along really well Mel, nice job 🙂
    As for the ESC wires, I had a model in the past which had long wires from the ESC to the motor, so I have always set mine up the same way.

  2. lawtonca says:

    This looks like such a beautifully built model so far.
    I would pick the best ventilated place for the ESC, failing that considering the COG for its location. If both are just as good I’d extend the battery because there are 2 wires to solder rather than 3 (but thats just cos I’m lazy and probably why my models don’t look as professional as yours)

    • Chris says:

      I’ve been trying to find out more information about extending ESC wires.
      The club consensus appears to be that the wires between the ESC and the motor should be extended, NOT the battery and the ESC. I’ve been looking online and found conflicting advice, these are the best 2 arguments for each side I have found:

      ‘Longer motor side lead length does effect the back emf detection of the controller, so the longer the leads, the less accurately and efficiently the motor will be run’ (http://www.rcgroups.com/forums/showthread.php?t=1808287)

      and:

      ‘the wiring from Lipo to ESC carries heavy currents which creates strong varying magnetic fields … The ESC cannot really tolerate long wires to Lipo, the capacitor on ESC will get hotter, will fail sooner, generally you will have more electrical noise.’ (http://www.rcgroups.com/forums/showthread.php?t=1786064)

      Scott mentions he’s had a model with long motor wires, my new Starmax Jas39 has the ESC at the back under the EDF with long battery wires up to the battery hatch at the front.

      Seems whatever you do there are issues, extending the motor wires seems to be the ‘safest’ option, but you can add extra capacitors to counter the increased induction of extended battery wires which will probably give the best performance ultimately.

      I’ve only got this from the internet, not from personal experience or verified expert opinion, and people on the internet will tell you anything

      • Mel Jones says:

        Chris, thanks for that, I did the same research and came up with the same result.
        In the end I have extended the three motor cables I have used a fairly hefty cable (cause it was all I had), so current flow a back emf problems should be kept to a minimum.
        Anyway will shall see, I`m painting it up now so won`t be long till black back time.

  3. Scott says:

    That looks absolutely fantastic Mr Mel, great colour scheme too 🙂
    Will have to make sure you video the maiden, can’t wait to see it!

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