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Ripmax’s Acro-Wot by A Wall

The Acro-Wot was first designed back in the ‘80’s by Chris Foss as a build it yourself kit where you completely assemble the model from all the components inside the box, ahhh the good old days!

But now on my building boars, oops, assembly board, is the Mk2 version (with some slight mods over the original) coming in as an ARTF (Almost-Ready-to Fly), oh how times have changed. Is that for the better or worse? You, the buying public can be the judge of the shift away from kits to ARF’s.

Acro-Wot #252 04I’ve seen my fair share of ARF models from years gone by and there has been some real beauties brought into this country by The Hobby Headquarters (Sydney), and this one is no exception. There’s a bit of info on Chris Foss via the ‘Net, go have a look and see his designs that go back many years. The quality is first class and you can tell as it’s built to take on the rigors of some serious flying!

What’s In The Box
To start with, the model is very well packed and free from any damage. Constructed mainly of lite-ply and quality selected balsa and all covered in quality iron on covering, the model stands out already. Included are two fully symmetrical main wing panels completely built and expertly covered, a tail group consisting of the horizontal stabiliser and the vertical fin, all complete with control surfaces. The fuselage, like the wings and empennage is completely built and covered and has a nice pre-painted fibreglass cowl up front and a tinted stylish canopy complete with a pre-painted pilot on board ready looking ready to impress you with his flying skills! The rest of the parts make up the undercarriage, the fuel tank and the necessary hardware to complete the model ready for your own engine and radio gear. All standard fair really, but it impressed me with the quality of the package as I unpacked all the bits ready to assemble.
The instruction manual is comprehensive enough with numerous colour photos and basic assembly instructions, well laid out for those that have tackled an ARF or two before. Towards the end of the booklet is as section on setting up your Acro-Wot, so there’s guesswork here.

Getting Started
The final assembly starts as per the manual with final fitting of the canopy. I actually fitted this last so as to keep it from getting knocked around during final assembly of the entire model. No point in going into too much detail here with any of this as I am sure most want to read how it flew so basic stuff about ‘togetherness’ here then we shall get on with the fun part, flying it. Used during the final assembly where Zap CA glues of both medium (green) and thin (Pink), my favourite instant glues, and a bottle or two of this stuff is never out of reach on my building bench.

The ailerons are glued in place with thin Cyano glue, a typical arrangement on all the control surfaces on this model. The ailerons are controlled by a servo for each surface and the fitment of them is easy using standard sized 3 kg servos, 6 inch extension leads and the supplied linkages. The two main wing halves are joined using a pre-cut hardwood wing joiner and gluing the lot with epoxy glue. Now it’s time to set this aside and allow the mating surfaces to dry. The wing is held in place using a locating tongue up front of the wing and nylon hold down bolts at the rear of the wing, bullet proof and fast to assemble and remove.
The main undercarriage is simply screwed directly to the bottom of the fuselage just forward of the wing LE; this pre bent arrangement is also bullet proof and damned strong! Wheels, axels and all mounting hardware again are supplied. The tail wheel assembly is also screwed directly to the lower rear fuselage.

Acro-Wot #252 03The fitting of the tail group is straight forward as one would find on any ARF model of this type. The removal of the factory applied covering needs to be cut as shown in the manual and then the tail-plane can be slid into place and glued using epoxy. The two elevators are joined by a spring steel ‘U’ shaped joiner (read the book as to when to fit this as not doing so will end in tears!), this arrangement is common when using just one servo for pitch control such as this Acro-Wot. The vertical fin is now glued in place, the elevators hinged (same as for the ailerons) and then the rudder along with its tail-wheel wire. The rudder is controlled by the very familiar ‘pull-pull’ cable set up (all supplied) and this works a treat for positive yaw control of this very capable aerobatic model.
A supplied pre-made single elevator pushrod is thread from inside the radio bay of the model out the back along the pre-installed outer pushrod tube, ending up connecting to the plastic elevator horn; too easy!

Three standard sized servos are fitted into the dedicated servo try already glued in place ex-factory. There’s plenty of room within the main cabin area of the model for the remainder of the usual radio gear; IE: receiver, battery and switch harness. The exact location of these last three items depends on the models centre of gravity, so I suggest fitting these in a temporary fashion ‘till you are happy with the models final balance point. I used a Sanwa 6 channel 2.4 GHz radio that set I did a review on some time ago and this level of radio set was perfect for the task.

Engine Installation
The business end of any model is where we get serious and what we do here can make the difference from a well behaved model to a monster that’s unreliable.

The firewall (where the engine mount attaches) has already been fuel proofed at the factory, and is a great move if you are going to power this model with a glow engine. Also the thrust line is built in (right side thrust) on the firewall. A two piece engine mount is supplied and should fit pretty much all of your garden variety 2 and 4 stroke engines in the size range as suggested.

I ended up fitting a Saito 82 four stroke with a 13×7 prop, probably a little overpowered but as they say, you can never have enough power. The fitting of this motor was straight forward with no surprises bearing in mind that there are some basic engine installation messages in the assembly manual; I again suggest you don’t skip these steps as they are helpful.

The supplied fuel tank slips into its own spot with the fuel supply tubes protruding through the firewall between the engine mount itself. This tank will need final assembly and a photo of how it goes together is shown. A throttle wire is included and should be of sufficient length to accommodate any engine in the suggested range. One advantage of a 4 stroke engine is that there is less work for the muffler installation although there is a cut-out already built into the lower forward part of the fuselage for a large more bulky 2 stroke muffler. The nicely shaped fibreglass cowl should house most engines leaving only the top of the cylinder assembly protruding. As always with any engine installation, allow plenty of opportunity for the hot air to escape within an engine cowl; in other words don’t make the engine too neat a fit where it protrudes from the cowl, we don’t like working in the heat and neither does an air-cooled engine. The provided spinner really sets off that streamlined nose shape.

There’s not a lot else to do here apart from a few decals to finish off the already impressive model. The very last page shows 3 views of the completed model for decorative purposes. Control surface deflections, the balance point (CofG) as well as some other handy info are all shown at the end of the manual which is logical as we are now ready to check these and then go and punch a few holes in the sky!

Test Flight
Now if I had a dollar for every new model I’ve assembled, built, constructed, put together and test flown over the last 40 plus years I’d be rich, but it still gives me a thrill to do it all over again here. Assembled and ready to fly the Acro-Wot has a real presence to it, and I’m itching to get it into the air. Fuelled, checked and we are ready.

Full power from the Saito .82 yielded a rather spirited outcome, that’s a nice way of saying ‘man where the hell did the model go?’ Perfect tracking, oodles of power and a brilliant colour scheme meant this was no lazy Sunday flyer! Having a somewhat long tail moment meant the model was super stable in the air, much like the pattern ship.

Straight up was the get-go and then into some fairly aggressive aero’s. Loops, rolls, inverted flight, spins, snaps and a few manoeuvres that kind of aren’t in the book! You name it and the Acro-Wot was up for it, and trust me (I’m a pilot you can always trust pilots they say) if you have the skills then you will have a lot of enjoyment with of this beast.

Stalls where predictable although a true stall isn’t easy to achieve with that large propped Saito still producing a fair amount of residual thrust even at idle. However the model lost height as expected but quickly recovered with standard stall recovery procedures, so no nasty surprises there. Having a nice thick-ish full symmetrical wing meant point it anyway you like and it goes there so hang on to that transmitter as this model isn’t for the faint hearted!

Landings where solid and predictable providing you remember that any plane, even a 1oz foam ultra-light model will stall and fall from grace if flown slowly enough. I always try to keep a constant decent going whilst landing, even if I am turning a corner to line up the runway, but if you must level off prior to touchdown then make sure power is applied to compensate for the loss of airspeed; this goes for any plane actually. Ground handling was excellent due the direct relationship of the tail wheel and the rudder and that rather long tail moment of the model.

Well there you have it, the Acro-Wot from Ripmax and distributed by The Hobby Headquarters of Sydney, is a sleek, fast and very agile all round sports model and as they say, “if it isn’t broken then don’t try to fit it”, meaning the Acro-Wat is a perfect design so we’ll leave well alone and not try to reinvent the wheel here. I suggest you get smart (no, not agent 86!) and join me out there to impress your fellow aviators!

This was your Captain speaking.

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