Andy's Drak

[Andy Sayle]

I did done a bit more last night.  The first bit, was to cut and glue in a block of epp to support the ends of the two piece correx covers for the main fuselage bay.  Mr Ritewing supplied a nice chunky lump of EPP moulded to fit snugly in the forward section of the fuselage bay.  I wish more kit suppliers did this, it's a cracking idea.  Anyway, I cut the back end off to sit where the covers meet in the middle, around 55mm thick.  I gooped it in place but cut a few channels to clear the spar tube, and wiring channels down the edges of the fuselage bay (did I mention them?  Another cracking idea from Mr Ritewing, recessed wiring channels down the full length of the fuselage bay).

Once this was dry, I made some little holes for the threaded inserts using a bit of hot wire.  The inserts screw into the foam with a hex key, and should be plenty strong enough to hold the covers in place.  I added a small amount of goop to the threads biting into the epp foam, just to make sure they stay put.

Another little job completed was to cut a few slots in the servo bays in the wing so that my servos of choice drop straight in with a nice snug fit.  I used a bit of 1.5mm wire heated with a gas torch to melt some channels through the foam for the wiring too, and then made corresponding channels into the fuselage saddlebays, and through to the main fuselage bay.  I may add more holes there for other stuff in the future.

Finally, I made a couple of servo extension leads to the vector FC that I am intending to mount in the rear bay for the fuselage.  I layed it all out using some pins to hold things in place to see how to route everything.  The ESC fits aft of the rear spar tube, Vector main unit and current sensor in front of the rear spar tube, and the gps puck thing sank into the foam I mounted above.  I'll probably bung the receiver in one of the saddle bays, and the vtx in the other saddle bay to give them a bit of separation.

I also had a tinker with a bit of spare foam.  I had this idea in my head of doing some tribal design type thing on the wing, using some black markers.  It turns out that Laminating film doesn't stick well at all to wherever the ink is, so it's back to the drawing board for that idea.  The lam that came with the kit sticks fantastically well to the bare EPP though, so the other idea of laminating and then using either profilm or printed vinyl is looking favourite at the moment.

Oh, and has anyone got any experience of mounting the vector about 5 inches aft of the CG location.  The manual says it should be as close as possible.  That's not going to happen here though...

More tomorrow night hopefully...

Andy

[Andy Sayle]

So after a week or so interlude on holiday, I'm back on the Drak build(s).  As the drawn ink under the lam wasn't going to work, I've made a start on laminating the elevons and wings.  Only a couple of pictures, as it is damn difficult to hold a chunk of foam, and covering iron, and a camera with only two hands.  I used the laminating film from Mr Ritewing, it is marginally thicker than the stuff I am used to, but on a test piece it doesn't half stick well to bare EPP.

I started with the elevons, and used a couple of pieces, wrapped around the hinge side of the elevon.  I found it was important to start in the middle of the elevon, and work outwards, to minimise any distortion.  This seemed to work well, although there is a slight bow that has been introduced.  Nothing to worry about though, a bit of heat and the hinging process will sort that out.  The laminated elevons are amazingly stiff, certainly comparable to a half decent chunk of balsa that hasn't been covered, so I have no worries about using these on a fast FPV machine.

As the iron was warm, I laminated a pair of wings too.  These were wrapped around the leading edge so the seam was at the trailing edge.  The width of the film wasn't quite wide enough to cover the entire wing in one piece, so I figured I would rather have the join running chordwise.  The wingtip was a bit tricky as there is a little flange for supporting the tip fins.  Again, the addition of the laminating film increased the weight by a few grams, but vastly increased the torsional rigidity of the wing panels.  For a fast FPV ship, it is a great addition.  For my mapping ship, I shall probably just run a 6" strip along the leading edge of the wing to save a few grams.

Mr Postman also came whilst I was away, with a new v2 gps, an airspeed sensor and an alerter module for my Vector.  I think I'll mount the pitot tube at the join between the fuselage and the wing, in a removable housing.  I'm wary of it catching in transport and general use, so this seems to be reasonably well protected.  I did think about putting it in the nose for the cleanest airflow, but this is just asking for damage (Both in transit, and on landing!)

Next job is to get some elevons hinged, control horns and servos/linkages sorted.

[Andy Sayle]

Not too much done last night, I got distracted refurbing my TBS Caipririiiiininnininha ready for some possibly nice weather this weekend.  I ran the servos on a sweep test for 10 min to burn them in (I always do this to check they don't go pop, or have any other problems.  The last thing you want is a duff servo that you have just installed).  I'm using Hitec HS5665MH servos.  Overkill for this plane, but they are reasonably priced, perform well, and can operate directly off a 2s lipo if needed.  Part of me is contemplating running the electronics off a separate battery pack.

I installed the servos in the wing using a smallish dab of hot glue.  The pockets were relieved for the lugs on the servo (I did wonder about cutting them off, but that's just adding work for myself) and a clearance hole/channel cut for the wire.  I also found I needed to chamfer the edge of the bay to allow the servo to obtain the maximum throw.  The hotglue works well here as it can be pulled out using a bit of alcohol to loosen the bond.  Perfect if a servo ever needs replacing.  I also started the control links.  I'm using Robart 1" bolt through horns.  These are nice and robust, have a three bolt through design that will clear the elevon sparring, and also have an integrated ball where the clevis is installed.  This will alleviate any bending in the control link, due to the misalignment of the hinge and control link.  The control links are 3mm solid carbon rod, with m2 ends bonded on with some Loctite gel CA.  I've only glued one end, as the other needs to be trimmed to size once the horns are installed.

It was at this point I realised I need to have covered the elevons before installing the horns.  I'm still undecided on the colour scheme, so onto the cairprprprriiriirnha it was.  I can't decide whether to use a bit of profilm on the elevon (Black) and do a fluorescent green leading edge, or whether to take a leaf out of Mutley's build, and use some fancy printed vinyl all over.  Obviously in a different pattern though!  And there is a roll of rather nice carbon effect vinyl sat in the corner of the workshop too...  bit heavy that mind...

I'll ponder that at work today....

[Andy Sayle]

Just a quick 30 min on the Drak last night.  I started off the electronics install properly.  First up was the Pitot tube.  I've decided to mount this at the join between the fuselage and wing panel.  So I melted out a channel in the root of the fuselage to drop the tube in, and then melted some channels for the tubing that go back to the saddle bay.  This will allow the tubes to be taped in place (maybe with a dab of hot glue too) for easy replacement.  The sensor will be mounted in the saddle bay, and the Vector bus cable routed back in the main bay alongside the servo extension.

I then thought I better update the firmware on the vector and check it works, but I had a little issue.  I don't know if it was my heavy handedness, or a fault in the products, but when I removed the cables from the GPS v2 unit, and pitot sensor, the cables took the outer connecter shells from the sensors with them.  Not ideal really, so I've pinged a support email off to RC-Log (where they were bought from) to see what they recommend.  I reckon I can probably get the shells back in place, and maybe put a dab of adhesive to stop them coming loose...

Still no decision on the colour scheme.  Anyone know of any good printed vinyl suppliers (Not really heavy vinyl either, nice light stuff please!)?  I also can't decide whether to have a go at laminating the fuselage.  I want to, but the complex curves, and high chance of me ending up with a wrinkly mess is putting me off...

[Andy Sayle]

The build has been on hold for a short while, other things getting in the way of building time.  I'm still no closer to a colour scheme, so I'm going to have a crack at laminatification on the fuselage, and go from there.  I can always put some decorative vinyl on at a later date..

Andy

[mutley2]

Hey Andy, I think Lam is the way to go but the part where the wing joins the fuzz is a real 3d shape and needs to be thought out, I used some thin lam I had from the Z3 build and it turned out ok but was hard work. I also went for the Ritewing balsa control surfaces, top grade balsa and worth the few quid extra IMo.
Keep the build pic's coming  :D

[Andy Sayle]

I'm going to get the flight controller and electronics installed for now.  I only have the fairly thick laminate that came with the Drak kits, what thickness is the Z3 stuff?  Any ideas of a UK supplier?

I think I'll use the thicker lam on the underside, that is going to take a beating on some of the rocky sites I have planned to fly from!

Cheers
Andy

[Billy_boy_2010]

I would always always lam something which I wanted to last. I bought some lam from flying wings. They had two levels of thickness which should suit you. I suspect both are thinner than the Ritewing stuff though.

People spend far too long on the appearance of their planes IMO. I wouldn't get obsessed about colour. Having said that- I'm going to iron some ooracover onto my wing post lam which should prove pretty quick and easy im hoping!

[mutley2]

Hey Andy, what batteries are you going to use?

[Dave G]

Hi Andy, I notice your servo leads have a nice twist in them, did they come like that or did you do it?

[Billy_boy_2010]

Hi Andy, I notice your servo leads have a nice twist in them, did they come like that or did you do it?

Use an electric drill and it's a doddle.

[Andy Sayle]

The servo wire was twisted when I bought it, this is the stuff I use:  http://www.componentshop.co.uk/3-way-heavy-duty-hitec-jr-twisted-servo-wire-20-awg.html   I have twisted the wires myself in the past too, using a drill and that works good too.

Battery wise, one of the Drak's will have the Ritewing SS motor, and a 5s setup.  I'll start with a 5000mAh pack for the maiden to keep the weight down a little (unless I need some more weight in the nose!) As for the other one, I'm not sure yet.  I'll see how the first flys, before deciding on a motor/batt combo.  I'll lean towards a 6s setup for that one though, mainly because I already have a lot of 3s and 6s packs I can use..

I should really get back on to this build, i got distracted by some little quads!

Andy

[Dave G]

Use an electric drill and it's a doddle.

Really! a drill - you and Andy do this, could you let me know how?  :o

[Andy Sayle]

It's easy.

Get tour untwisted servo lead, or separate wires and hold one end of then in a vice, or pin them tightly to a workbench to stop the end flapping about.  With the other end(s)  clamp them together in the chuck of your drill.

Now hold the wire(s) fairly taut,  and set the drill going to wind it up.  Start slowly, and don't over twist them.  Whilst you need to hold the wires quite tight,  be aware the wire length will shorten as you twist.  The last thing you want is a load of broken wire from over twisting and over tensioning.

Once you have the desired twistyness you need to hold it for a few seconds.   Then unclamp the wires from the drill chuck, and be reAdy for them to unwind a bit.  Then you are done!

I normally do them in 5 or 10 metre lengths, and wind it onto a reel to store...

Hth.
Andy

[Dave G]

It's easy.

Get tour untwisted servo lead, or separate wires and hold one end of then in a vice, or pin them tightly to a workbench to stop the end flapping about.  With the other end(s)  clamp them together in the chuck of your drill.

Now hold the wire(s) fairly taut,  and set the drill going to wind it up.  Start slowly, and don't over twist them.  Whilst you need to hold the wires quite tight,  be aware the wire length will shorten as you twist.  The last thing you want is a load of broken wire from over twisting and over tensioning.

Once you have the desired twistyness you need to hold it for a few seconds.   Then unclamp the wires from the drill chuck, and be reAdy for them to unwind a bit.  Then you are done!

I normally do them in 5 or 10 metre lengths, and wind it onto a reel to store...

Hth.
Andy

Thanks very much  :D