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Sep 10, 2013, 05:41 PM
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Build Log

Eurofighter Typhoon - 64mm from HobbyKing (Rating 7/10)


When I needed to grab a few things from HobbyKing (Aust) I checked the 'specials' and there was a 64mm Eurofighter Typhoon for $49.99 (normally (83.20). These 'older generation' 64mm designs are OK in terms of the foam, but always underpowered and cheap in parts. So at $49.99 it was not such a bad deal and I grabbed one....
It even has a rudder as it comes....

Unfortunately (???) they do not have any more at Hobbyking anywhere. I think they were clearing the remaining stock.

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Last edited by PeterVRC; Jan 06, 2014 at 05:49 PM.
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Sep 10, 2013, 05:45 PM
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Too small to have decent retracts, and I hate fixed landing gear - unless the real plane has fixed gear too - so it was going to have to be hand launcher. I have had two other of this type of 'older generation' EDF and they are underpowered and lack lustre to fly, so it will need a power system upgrade! I haven't decided 100% but most likely I will use a Mercury all alloy 3700kv 64mm EDF in it. This is to stick to 64mm, whilst having 8 blades and a very cool 'turbine-like' sound, and quite good power level from 4S. I don't mind using 4S in smaller EDF's.... any cell count is ok if not huge Amps being used.
I wanted to keep the mods to the bare minimum required to make a great little jet.....

https://www.hobbyking.com/hobbyking/s...it_3s_5s_.html

I hacked out the front nose gear assembly and removed the joint rudder/steering servo, which is mid way down the plane. The rudder servo to go at the base of the fin instead.

The foam is high density EPS and that is actually a much nicer foam to work with than EPO.
On a lot of these 64mm "older generation" foamies it is quite pock marked, not smooth, so the paint finish is a bit lack lustre - closer up. So once the main items (wings) were all attached I gave it a nice lavish coat of WBPU to deal it all up. It will need more later.... and sanding, then repainting, if I want it to be 'perfect'. Without repainting it will always show the 'pock' marks to a visible degree. But it would still look gleaming and acceptable if just left with the few coats of WBPU.

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Last edited by PeterVRC; Sep 10, 2013 at 07:14 PM.
Sep 10, 2013, 05:52 PM
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Wing Spar


Pretty well every plane I have, especially 1000mm upwards, have a carbon fibre wing spar added (many smaller aircraft don't come with one at all). So in went a 5mm CF tube spar...

As it comes the servos are mounted under the wings, and for belly landing that is not such a great idea. It also has them quite a long way from the elevon surfaces, and they give you thin flimsy pushrod wire - another great (not) design aspect of it!! So that had to be changed.
Moving the servos much closer to, and in line, with the control horns, I found the wing thickness matched the servo thickness. This meant I could cut the servo hole right through the wing, to utilise alloy plates top and bottom as the servo holders - allowing easy servo removal in future. Small plywood 'screw mount plates' are epoxied into the wing to have self tappers hold the plates on.
I used 30tho (?), about 0.5mm, aircraft aluminium sheet, and the covers are lighter, yet stronger, than any plastic or plywood would be... whilst being paper thin!

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Last edited by PeterVRC; Sep 10, 2013 at 07:11 PM.
Sep 10, 2013, 06:27 PM
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Hatch-Battery area


Next was to make room for a decent 4S battery.
4S 2650mAH 35C 222g
The cockpit/hatch area is ALMOST large enough as it comes. But the foam design in there is perfectly suited for a bit of hacking/trimming to make the room required. So that was quite easy.

The ruder servo is mounted after the cockpit area, under a plastic cover, so when I removed that I could see a great place for the RX! But access into there was a bit small and difficult, so I cut the 'backbone' plastic to make a large "cover" for that area.
So far all aspects of this plane have made for PERFECT solutions for the required modding!! That makes this a very good base 'foam block' to build up from!

A plywood "floor" plate for the RX area closes up the hole the rudder servo leaves, into the ducting below(!). A bit of the usual velcro put onto that plate to hold the RX down....

The battery area will also get a 2.5mm plywood "floor", so the battery can be velcroed down and also strapped.

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Sep 10, 2013, 06:29 PM
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Rudder servo


The fin is thick enough to fit the servo within that, and not come out the other side. The servo wiring, extended, has a nice run down the "backbone" of the Eurofighter, to end up right in the RX area. Another nice, make things easy, aspect of the plane...

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Sep 18, 2013, 10:36 AM
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64mm Mercury 3700kv EDF


I was going to give the stock EDF a go on 3S...... but then decided that was a pretty silly idea, seeing it is so lack-lustre in power and pretty much 'junk' stuff.... So I changed it out for the Mercury 64mm 3700kv EDF, as planned for later anyway.

It needed a bit of foam 'drum sanding' out to fit it in, and also the EDF hatch needed to be longer to allow even getting the EDF unit in and out. Those mods all went fairly easy really, but there might be a thrust-line effect of the way the fan sits in the EDF space a small amount 'tilted'... so I might need to fine tune the thrust output path later, to 'correct' any strange efflux pattern and direction it might cause.

I decided to use a HobbyKing 80A ESC, seeing the fan can run into the 60A's on 4S, and it is a smallish ESC anyway. Thus it gives some leeway for safety, plus it still fits well too.
I used HXT4mm connectors, as per the 4S 2650mAH 35C Nanotech batteries, that i will use, have. Plus I used 3.5mm bullets for the motor connections, rather than soldering them fixed, because the wiring path required means you need to be able to disconnect the ESC from the EDF to get the EDF out ever.

I gave it a medium power test run and it all ran fine, but I have never run it to full power so I don't really know what it will do in the plane yet (Amps and Thrust).
I have not fixed in the EDF with anything yet - I will most likely make some flanges for its mounting points, so I can bolt it into the EDF bay, and thus allow easy removal for the future (as I usually do).

The assembled weight of everything except battery was 628g. Pretty good really. AUW flying weight is approx 960g.... also quite light really.
All parts sitting together it even balanced dead on the recommended CofG point! That was a good fluke, seeing I have only roughly tested that with the stock EDF in it once before - though if it was amiss I would alter ESC and/or battery position as required anyway. But it was good to be just right already.

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Last edited by PeterVRC; Sep 18, 2013 at 10:41 AM.
Sep 19, 2013, 05:37 PM
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Nose-cone filling - with Water Based Foam Spray


The plastic, hollow, nose-cone is causing some delay....

I decided to fill it with 'spray foam' (from the Hardware, made to fill cavities in walls etc) to give it some decent support - rather than being quite easily 'softly dented' by hands/fingers, or handling/transporting the plane, which in a worse case could crease/dent it permanently.

At the Hardware there were two choices of spray foam... PolyUrethane based, and Water based. PU is what GorillaGlue is based on too, and seeing I have used/seen that I had an idea of what it would be like. But Water based allows much easier cleaning.... so I picked that.
Hmmmmmmm.......

When you fill a 'container' (eg something with one open end) it means air can only enter, or escape, from that end. So when you use something that needs to DRY, it is not as quick compared to the substance being in more open air. A nose-cone is this case too.
The foam is "fully cured in 24hr".... but in this case 12hrs later it is 'spongey'. Even the seemingly dried outer area is spongey, which is not like PU when it is dry. So the Water based version might be a bad idea...... I suspect it is never going to go remotely 'hard'.
Possibly fine for its intended use in walls etc, but not looking promising for this nose-cone job. I will see.....
If I have to i wil remove it and get some PU based foam..... sigh.

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Last edited by PeterVRC; Sep 19, 2013 at 05:44 PM.
Sep 22, 2013, 05:51 PM
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Nose Cone - PU Spray Foam


Well, I was worried about the WATER Based foam spray.... and rightly so.....
It never got much harder than foam rubber = softish, spongey. So out it all came and I headed to the hardware to get some PU foam spray.
This set HARD.... much more like polystyrene foam, not foam rubber! Not quite as good as real foam, but a huge improvement over just AIR inside the nose-cone! It is not light and very resilient to pressure applied.

Washing the PU spray nozzle etc was a little bit painful - you really need acetone or something(?). I washed the majority out with warm water - which does not truly 'melt' it, but does wash 90% of the soft/liquid stuff out. Then once set I 'rammed' out the hard stuff with a wooden skewer, seeing PU doesn't stick to plastic very well.

Which also means it is possible to use the stock nose cone as a MOULD to make PU noses from. Just fill... let set... extract... done...
Then make another.... so you have a few spares. They could probably be used just as they are, but it would be better to make a harder outside skin for it from something. Maybe even just silkspan with WBPU, or something light and simple like that.

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Sep 29, 2013, 06:32 AM
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Nose cone filling, completion


A bit of trimming and hacking of the PU spray foam filler and the nose cone was ready to attach. This was nice and firm stuff, but still very light and easily cut and trimmed. It really firms up the nose cone a lot!

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Sep 29, 2013, 06:40 AM
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RX and Guardian positioning


I moved out the RX to place an Eagletree Guardian in where the RX had been. This is so it is on a "platform" that is stable. I still use velcro for mounting stabilsiers too - that same as RX and most things.
For now the RX 'floats' in an area in the hatch area, but it stays where it is very well. I am thinking whether or not I need to make something better to mount it up there.

At first the RX was behind the Guardian area, but I have been testing FPV setups to use in smaller aircraft (eg as small as 800mm) so to set teh Eurofighter up for FPV the RX will go forwards of tha Guardian to allow the FPV VTX to go down the rear end of the plane - to keep it away from the RX region. The weight of the VTX is fine there, because the Eurofighter struggles not to be nose heavy as it is anyway. So there is plenty off leeway to have some extra rear mounted weight.

Though FPV won't come until the plane is flying and all sorted out 100% anyway. And the cockpit structure is a bit tricky to work out the best way to have it easy to "plug in" either the FPV camera, or the pilot.... so I need to work that out too.

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Sep 29, 2013, 06:42 AM
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Canards & Tip tanks(?)


I CA'ed the canards on, and the wing tip tanks. Just some small dobs of CA so it does the job, but can break free if required for any crash!
Interesting that the canards have quite a bit of positive incidence (like Up elevator).

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Sep 29, 2013, 06:45 AM
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Removable Top Deck


The Eurofighter has a long one-piece plastic Top Deck down its back, which suits making it into a total hatch area. So I added some plywood plates to allow screwing the Top Deck down, and have it removable - which should not need doing too often. But the two screws are easy enough, and quick enough, to remove anyway.

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Sep 29, 2013, 06:46 AM
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Rudder


I CA'ed the Rudder servo in, and dug up a thin pushrod for it.

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Sep 29, 2013, 06:48 AM
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Servo covers


Seeing the stock servo positions are not used, and they leave quite large chunky holes, I had to make up some balsa wood covers for them.

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Sep 29, 2013, 06:59 AM
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Inlet, Exhaust & Cheaters


I ran up the Mercury EDF to full power....
Hmmm... 40 Amps, ONLY.... which I thought was half good (to keep Amp needs down), and half bad (as it means the Power level is LOWISH).
A "Vertical Hand Hold" Test showed the thrust was a fair way under 1:1... which the numbers suggested it would be.

I figured it was either the quite smallish inlets and initial ducting area.... or maybe even the exhaust area. Seeing the plane was really designed for a low power 64mm system it would very likely choke a higher power system.
I used a Dremel with Drum Sander to open out the rear of the exhausts as much as I could (like I had done for my 64mm F-15 also), and when I was doing that I looked at the Inlet area - which is all plastic and cannot be enlarged(!) - and decided it would likely need some Cheaters added too!
So I did that. They are easy to cover up, close,if required anyway.

Seeing I did both those things (Exhaust and Cheater) at the same time, the next test was with them both and it was 44Amps. 10% more... still a bit low.
But the "Hand Hold Test" had it MUCH closer to able to hold its own weight.

On the scale, the thrust was 720g.... and AUW is 950g.That is 0.76 : 1 Thrust to Weight... that is what a typical jet needs to fly 'properly'... 'jet fast'...
The Eurofighter being a Delta Wing, and also quite a slick shape overall, should go quite fast with that ratio.... though I would have liked to see 50Amps and more like 850g Thrust. I wills ee if I can "Find" that somehow....

I can't say that is overly like the MOTOR SOUND of the Mercury. It sounds a bit 'ratty'.... like a cheap motor sounds. I would say I could have done a better "Home Assembled" 64mm unit myself, for less cost too.
It LOOKS fantastic... especially the metal blades... but doesn't sound any better than well balanced 'plastic' does anyway.
Power/Thrust-wise.. I have no idea if another form would do better in the ducting it has. (eg use a Lander 64mm rotor in some 64mm housing, with a decent motor).

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