Reviews

Features:

1. HobbyKing Bix3
2. Just Engines ‘Super Quiet’silencer
3. Ripmax ‘Wot 4’
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The HobbyKing ‘BIX3’: an excellent trainer

by Peter Richardson

With more than half a dozen of these models being flown by Club members (all performing excellently), it is safe to say that the Bix3 (aka the Bixler 3) can be safely recommended to novices taking the electric power route.

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Three variants are available – the one you want is the Plug and Fly (approx. $US129). This is supplied with all the hardware and radio equipment except for the receiver, transmitter and flight battery. Servos are pre-installed and you can get airborne after a couple of hours work. The Ready to Fly variant has those ‘missing’ ingredients – but frankly you won’t want their R/C system, and no-one will have a compatible buddy box. You can buy it as Almost Ready to Fly – but that is the basic airframe only and the cost of buying your own servos/motor/electronic speed control/servo extension leads, etc. makes this uneconomic.

The Bixler 2 is also still available, but spare parts are no longer available and the Bix3 comes complete with an undercarriage, far more space within the fuselage to house the R/C gear and a MUCH better quick release wing retention system for ease of transportation and storage.

So what exactly IS a Bix3?

See https://hobbyking.com/en_us/hobbykingtm-bix3-trainer-fpv-epo-1550mm-pnf.html for details.

Moulded from EPO foam, it’s a 1555mm span motorised glider, with the motor mounted above the fuselage in a ‘pusher’ format. It’s more sophisticated than it looks: the two-piece wing plugs together with aluminium joiners inserted into carbon fibre tubes, while the fuselage has a central carbon fibre tube and carbon fibre stiffeners either side of the nose section. The canopy is held in place with magnets and gives access to the battery bay.

Gaith's Bix3 caught in action by Harry Appleyard

Gaith’s Bix3 caught in action by Harry Appleyard

The undercarriage simply plugs in place and can be removed if you wish. And because there is an undercarriage, the Bix3 can be used to take your BMFA ‘A’ certificate, where take-offs and landings are mandatory. It will need to be ballasted up to the BMFA’s minimum weight limit of 1kg to actually take the Achievement Certificate as the claimed flying weight is 890gm – but that’s with a 2200mAh battery and without the optional flaps. My own model has a 3200mAh battery which weighs an extra 60gm and also has about 25gm nose weight, so it’s no big deal.

Flying

With a large wing and low weight, it is easy to fly and allows plenty of ‘thinking time’. The high wing layout and tip dihedral makes it stable. The foam material is actually quite robust, but should you really thump it into the ground (it happens!) it tends to break up in big chunks which are easy to glue back together. But you have to hit the ground really hard for that to happen – and if the worst comes to the worst, you can buy spare parts: a replacement fuselage cost around £16, for example.

My own 'hi-vis' example: not pretty but at least I can see it!

My own ‘hi-vis’ example: not pretty but at least I can see it!

Flaps are pre-fitted, but you will need to buy a couple of extra servos – at under a fiver for a pair. Not strictly necessary, but they do add a little fun and may be useful if you increase the weight of the model.

The Bix will cruise around at a steady height on about a quarter throttle and with a 2200mAh pack will give a flight time of around 20 minutes with mild throttle use. Whack the throttle stick fully open and she will climb at quite a respectable speed. Cut the motor completely and she will glide quite nicely and when conditions are right will easily grab a thermal and climb away.

Should you get bored, then full throttle and big aileron movements will let you loop and perform rather untidy rolls, while stall turns are not that pretty but can be achieved. Inverted flying needs a fair bit of forward stick, but is easily achieved. I have tried aileron differential but it had little effect. Turns can be made equally smoothly with rudder only (the nose does not seem to drop) or aileron only – or together. It really is quite benign. Gain more experience and if your transmitter has the facility, you can set up different flight modes for normal flight, soaring and landing with flap and elevator compensation.

Of course, nothing is perfect. Whether it’s the cheap servos not centring accurately or a basic design characteristic, you will find that you are constantly ‘nudging’ the controls for straight flight to prevent it turning a little to either side. And when making an approach with motor off and then adding a little throttle there can be bit of a delay while it ‘stops’ flying – but it’s all very gentle and nothing to concern you. When I flew Roger’s lighter version it landed noticeably slower/smoother than my own.

Assembly

This is really very simple and though the instructions are brief, they are adequate. Basically all you have to do is glue the tailplane to the fuselage and the fin to the tailplane, plus add the nose cone – then install your gear.

Google ‘Bix3’ and you will find a host of forums with ‘hot tips’ and modifications. Ignore them. Build it like HK intended and it will work fine. BUT it is true that HobbyKing are very mean with their use of glue. On my version the carbon wing tubes were quite loose in the moulded wing slots, and the nose reinforcing carbon strips fell out when I poked a scalpel at them. For the main assembly I used Uhu Por adhesive as the HK glue supplied did not inspire confidence – but a hot glue gun (£5-10 from HobbyCraft) was the weapon of choice for attaching the carbon bits to the foam securely. Use the hot melt glue, not the cool version – that sets too quickly to get pieces in place. The glue gun is also very useful for fixing the plastic plate to the top of the horn fittings where they poke through the wing to stop them working loose, and to retain the control tubes that run along the fuselage sides.

If you use Uhu, remember it is a contact adhesive, so apply to both pieces, allow to dry then bring the bits together: but you’d better get it right first time or you’ll be in trouble. You can use it as a ‘normal’ adhesive, but then allow plenty of time for it to set – like overnight in a warm room. PVA works OK, but again leave it overnight – when bonding foam it takes a long time for the water in the glue to evaporate.

The decals are dreadful: they will fall off as you look at them – and besides in the air they are so anaemic that the model’s visibility is really poor. I pulled them all off with tape, wiping the surfaces with a meths-filled rag to help remove the mould-release agent (others use soapy water) and then sprayed fluorescent paint: it may not be pretty, but at least I can see it! Be aware that paint doesn’t stick too well to the foam, and it will soon look a bit scruffy. The other alternative is to use pieces of Solartrim or Ultracote trim.

The one area where beginners can go wrong is fitting the prop: the front of the prop faces forward which in this application appears to be on backwards. See it and you’ll understand!

I fitted the ESC to the floor under the centre section, and the receiver to the fuselage’s inner wall. Velcro does not stick well to foam, so I first glued 1mm thick ply plates where I wanted these items to go, and then smeared epoxy resin over the top surface to give something for the self-adhesive backed Velcro to grip on.

Ply plate with Velcro strap for flight battery

Ply plate with Velcro strap for flight battery

In the same way, I made a ply plate for the battery to lie on, covered it with a strip of Velcro to match the Velcro applied to the battery, and then stapled a Velcro retaining strip to the underside of this plate. Next I used a soldering iron to melt the foam to give clearance for this strap before gluing the plate in place. You do need the battery to be held firmly in place – and mount it as far forward as possible.

Extended servo leads means easy storage and transport

Extended servo leads means easy storage and transport

Being lazy, I connected up the aileron and flap servos with long extension leads to the receiver so that when I remove the wing I can lay it alongside the fuselage for transport/storage without ever having to unplug anything…

 

The only other ‘mod’ I made was to replace the supplied clevises with metal items as the kit-issue parts seemed rather flimsy – but this involved having to cut the pushrods and solder on adjustable fittings, which requires a fairly hot (65w) iron. If you stay with the items supplied, do use small rings (cut from model fuel tubing) to keep them closed and safe.

Dealing with HobbyKing

Various Forums are awash with comments on HobbyKing: both pro and anti. But you cannot deny the value for money they offer.

I can only speak from my own experience, and I have actually found them good to do business with. My last order (5 items) was placed at 9.45am on a Thursday and received 8am next day.

Once I emailed their Customer Service at 10pm to report missing hinges and received a response half an hour later – and the parts arrived in three days (by which time I had found the missing items: being moulded in transparent plastic I had failed to see them). I have also used their ‘live chat’ to enquire about a delivery when parts were out of stock, and received satisfactory responses.

But the site is quirky and despite (or because) of a major site revision in November 2016, has failings.

If you’ve not dealt with the company before, the first thing you notice is that the pricing is (usually) in $US. After opening an account, click on the ‘Add to cart’ button and you are taken to another page. IMPORTANT. Under the ‘Warehouse’ heading click on the arrow and make sure you select United Kingdom – if not the item will be sent from the warehouse shown – and that can  mean both big postage costs and customs payments due! Refresh to make sure that the Stock heading for the UK warehouse states ‘OK’ too – because if you order several items and one is out of stock, then your whole order will be delayed until that missing item is available. Many items are listed as out of stock, and sometimes you can place an order, other times not. How long do you have to wait? You can ask for email notification when items are back in stock, but often this does not work. Also be aware that items seem to come into then out of stock quickly, so if there is something you really want, keep checking.

Click on the box advising of postage costs too: often you will find that 24 hour delivery is only pennies more than 48 hours, or even less.

If the item you want is not available from the UK, then check the European warehouse and then check the cost of postage. Sometimes there is not much difference, other times substantial. Delivery is usually a few days longer.

Be aware that as all prices are usually in US dollars and with the pound sinking, prices are rising. When I bought my Bix the cost in sterling for the Plug and Play version with postage and four extra servos was £95. Today that would be around £118…

 

 

 

 

 

 

 

 

 

 

 

Just Engines ‘Super Quiet’ silencer

by Peter Richardson

When the Thunder Tiger 36 in my ‘X-S’ fun-fly failed the noise test, I was not surprised: these lightweight models need a fine-pitch prop and lots of revs to get their fast climb rate. More surprising was that it only failed in one direction, and then by just 1.5dBA.

A phone call to Just Engines brought me their Super Quiet muffler, described on their website as being a three-part unit (front, middle and rear sections), having a thin baffle with punched holes that could be placed either in front of or behind the middle section. This gave the option of variable noise/power restriction – with further ‘adjustment’ being possible by either hammering the punched holes closed to reduce their diameter, or opening them up long-nose pliers.

A little crude, perhaps, but at least it allows some tuning. They also suggested that passing a bolt through the outlet pipe would further reduce noise simply by adding an extra restriction – though cautioning against increased back-pressure/overheating.

They offer three different sizes (depending on distance between muffler mounting holes): the advantage of the Chinese manufacturers all copying OS engines is that items like this become virtually universal: the TT36 required their smallest unit (35mm bolt spacing) and cost just £16.50 plus postage. Other sizes available are 37mm and 42mm.

On arrival, I pulled it apart and found that the design has clearly moved on since the web site was written (at least in respect of this smallest unit): in place of the crude-sounding baffle plate was a cast cone, complete with some 24 drilled holes each of a mere 1.17mm diameter. That means a total of 25.8mm2 for the gases to pass through. Not a lot. Once past that, they can exit via the outlet pipe – much bigger at 27.3 mm2!

Compared to the stock silencer, this new unit was at least twice the volume, weighed 144 grammes instead of 66 grammes, and had an outlet pipe diameter of just 5.9mm compared to the original’s 8.2mm.

Frankly, looking at the size of the holes in the cone, it seemed that this was going to be VERY restrictive: I had to blow through the unit to convince myself that any exhaust gases could actually pass through…

There were no ‘instructions’ with the unit, though it appeared well made and came nicely packaged with three Allen keys (two of which were of no use as they were of a different size to the cap-headed screws provided (!), and a gasket.

Expecting the unit to be over-restrictive in terms of power output, I went to the flying field armed with a drill and numerous bits so that I could enlarge the holes in the cone.

First though I left the old silencer on and ran the engine on its usual 11×4 APC prop, recording 12,200-400rpm – just what it usually delivers. The worst noise level recorded was 83.5dBA (tail). With the new silencer in place, and with the cone mounted in front of the centre section to give the smallest initial chamber, the needle was screwed in until it peaked at 11,600rpm – but now it tested with a worst noise level of a mere 75dBA!

Richening the needle one click, a test flight showed that the initial acceleration from take-off was a little down, but nothing to worry about. And despite my worst fears it ran fine – starting easily by hand, throttling being unaffected.

Before the next flight I moved the cone back behind the turned section to give a larger initial chamber, then re-tested without touching the needle. Now the rpm was up to 12,000-12,200, and the noise meter peaked at 78.2dBA. In flight, the performance was no different from the original: it climbed vertically from take-off – what more can you ask? The model did require an extra 28g of lead on the tail to counteract the extra noseweight, but that made no discernable difference.

I suspect that I could improve performance over the original silencer (there are lots of possibilities, ranging from removing the cone and/or centre section to enlarging the holes in the cone and/or tailpipe) and still be under the noise limit – but see little point. It goes as well as ever, has no noticeable adverse-effects such as increased back pressure or overheating. And morally, shouldn’t we make our models as quiet as we can?

Noise levels:

 

Standard                     Super Quiet                 Super Quiet

12,200-12,400rpm       Cone in front               Cone behind

A (nose)          81dBA                                    74dBA*                      77dBA

B (RH)            75dBA                                    75dBA                        78.2dBA

C (LH)            80dBA                                    71dBA                         73.5dBA

D (tail)             83.5dBA                                74dBA                         74.7dBA

* Engine bit cold and not on full song

Incidentally, Just Engines also sell a range of ‘Quiet’ silencers which are effectively the same as the ‘Super Quiet’ but without the centre section.

 

Ripmax ‘Wot 4’

By Peter Richardson

I’ve never really understood the ‘cult’ of the Chris Foss Wot 4, but when I needed a quick-build winter hack, the ARTF Ripmax version looked like it would fit the bill, especially with a price tag of just under £90.

Certainly, there’s little to complain about. Build quality proved fine, instructions detailed and accessory pack adequate – though I chose not to use much from its contents. My first thought was to fit an ASP52 four-stroke, but the engine mount supplied was too wide for its crankcase, and being in bit of a rush, I couldn’t be bothered to fit an alternative. Instead, an Irvine 53 fitted just fine, though at the top-end of the recommended range.

A simple glass fibre cowl is provided that fits-where-it-touches and does the job, leaving much of the engine/carb exposed for easy access. Nothing wrong with that, and contributing to the rapid assembly: a week of (short) evenings saw it ready to fly.

The dural undercarriage offers very little ‘spring’, and is mounted at an angle on the bottom of the fuselage so that the shock of landing is transmitted straight to the plywood mount. It looked a bit vulnerable, so I used plastic bolts to hold it in place. Unfortunately, these have a thread that is close to that of the supplied T-nuts – but not the same. Consequently they tended to strip if over tightened.

In practice, if ‘arriving’ off the landing area (!) they snapped – but at least the fuselage did not get damaged. Finally, I gave up replacing the bolts and instead installed a piano wire torsion-bar style undercarriage which was very successful in withstanding even hard landings without any damage. Other users in the Club have reinforced the area with glass fibre: clearly the undercarriage is a weak point – as with most ARTF kits.

And the flight performance? Fine – but in my opinion it failed to live up to the hype. Nothing wrong mind you, and it would fly impressively slowly without stalling. But the old-fashioned and rather narrow strip ailerons deliver a relatively mild roll rate, and the rudder and elevator are under-sized compared to modern counterparts. This is no 3D machine, though it was used by the pioneers of prop-hanging to achieve this ‘abnormal’ flight practice. They will tell you that it was good training for this – but more modern models will achieve prop hanging far more easily. Not that i can pass an opinion on this…

Incidentally, the ARTF model is the Mk2 Wot 4 with a parallel chord wing, while the build-it-yourself version (ironically considerably more expensive than the ARTF!) is a Mk3 with a tapered wing.

On my version, I need a significant amount of up elevator trim (3mm) to maintain level flight on mid throttle, suggesting an error in the wing or tailplane incidence, and I also needed to move the CG back at least 15mm than suggested. This was achieved by fitting the five cell battery pack below the servos (tight squeeze!) at the rear of the radio bay.

With a 12×6 prop fitted, the Irvine 53 gave sufficient performance with low noise output – but certainly not in ‘hooligan’ mode.

Would I recommend it? Yes, no question – it would be a fine second model after a trainer, and certainly met my need. But do look at improving the undercarriage. Or learn to perfect your landings.

And if you are wondering why there are no pictures and I am no longer to be seen flying it, then that’s because I had a fly-away with it. No problem with the radio: I simply looked away too long when moving from the take-off strip to the pilot’s box, and by the time I ‘found’ it again, it was too late…