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Acacia II Review

by Alex McMeekin as seen in QFI 50

The Acacia II is a new model in some respects, and an old one in others. Why change an existing decent design? To improve it of course!

Some History

The original Acacia first appeared at Viking Race 98 in South Wales. This is the number one event in the F3F world and people from all over converge for a weeks fun and fierce competition. The Slovakian team headed by Rudolph Masny appeared at scrutineering with some interesting new all moulded models. In-depth interrogation with the help of an interpreter by the 'UK new model acquisition team' determined that these models were prototypes, fresh out of new moulds and were pretty well being test-flown at VR98! So they looked good, but would they GO good too? Yes they did, Rudolph's own machine recording a 37-second run during the week, quick by any standards. Well the 'UKNMAT' duly placed their orders and a month or two later we received our models.

The Acacia turned out to be very good indeed, fast, responsive etc.... In fact it was hard to level any criticism at it at all, but if one were going to level a little criticism at it where would one start? The Acacia developed a little bit of a reputation for 'flicking'! I hasten to add that mine never flicked ever! One chap however had an Acacia that flicked wonderfully; in fact he was able to perform the most impressive flick-roll/tumble you've ever seen a glider do! His secret? Truly ridiculous elevator movements combined with a rather small tailplane area!

The Acacia 2 now has a slightly larger tailplane sporting a new section that has tamed this behaviour for those of us who simply cannot fly without vast control surface movements! Next criticism? Wing mounted ballast. This can be a pain; if you need to dump your ballast in a hurry, peeling open a hatch in the wing and turning the entire model upside down to empty the tube is a nuisance! Far better to have it in the fuselage where you can just slide off the nose cone and empty the ballast into your waiting hand. Lo and behold, the Acacia 2 has fuselage-mounted ballast!

Now I know one of the reasons for wing mounted ballast in the old days was to 'spread the load' more evenly across the wing, well forget all that, wing strength, or lack of it is simply not an issue with any Acacia! In fact the word 'strong' is a good definition of an Acacia! The fuselage has changed slightly to a low pylon mounted wing, rather than the wing being level with the top surface of the fuselage. This also gives a little more room for the wing servo connector plug, and also makes the fuselage more 'grippable' for launching. So there you go, at least three improvements to an already excellent model

Construction

There isn't any! It's a fully moulded, fully finished model. You merely have to install the radio gear and a few control surface horns. The wing is identical to the Acacia 1 apart from a slightly differing wing seat, and is of Glass/Balsa/Glass sandwich construction. Wing section is RG15 'modified', whatever that means! No Carbon option is available but frankly this is unnecessary, as the model is undoubtedly one of the toughest around. The wing spar is made in a separate mould from the wing, perhaps the best way to do it. The glass skins are laid up at 45 degrees to the span, which imparts maximum torsional rigidity. The wingtips are connected to the centre panel by rectangular carbon wing joiners. Both ailerons and flaps are fully shrouded. The wing is attached by two hex-headed screws.

Tailplane construction is similar to the wing but just on a smaller scale. It is bolted to the fuselage with one hex-headed screw and one smaller locating screw. Elevators are shrouded as per the wings. The fuselage has a slip on nose cone with an internal 'boat hull' that takes the radio gear. With a little care the fuselage will take standard sized servos and a full sized receiver, remarkable these days and cheaper too! The tail boom has four carbon reinforcement areas running the length of it; I don't quite understand this as the original fuselage was very strong anyway, now it's just incredibly strong! Stainless steel pushrods are ready installed with threaded rods at either end. Neither the steel pushrods nor carbon reinforcement seem to have had any adverse effect on my Multiplex radio set-up, glitch or range wise.

Radio Installation

Two standard servos were screwed into the moulded inner-nose and were easily connected to the pushrods with metal clevises. At the tailplane end two lengths of 2 mm rod were glued into the pre-drilled holes in the elevators and brass ball links were soldered onto the lower ends. These were attached to the pushrods with the appropriate plastic ball joint connectors. Stick the receiver, battery, switch harness and receiver wiring loom in and that's the fuselage and tail done.

I glued the servos into the wings having wrapped them tightly with masking tape. I have always done this with wing servos finding no problem with the method. There is definitely room in the hatches though for you to install a screw down system if you want to. The only thing I would recommend is that whatever method you use, make sure the attachment load is evenly spread out and not all running through one or two points. The wiring loom was made up and installed, nine pin 'D' plugs (as used for the serial ports on a PC) were used to connect the wing wiring to the fuselage. They are readily available from many electrical component retailers. I made up some 2 mm glass fibre plate control surface horns and installed them, although the wing is ready drilled for commercial brass horns. The servos were connected to the surfaces by easily made 2 mm threaded pushrods and metal clevises. That's the wing done.

Very little lead was needed in the nose, probably due to my use of a 5-cell 1350 mAh battery pack. This allowed every control surface to have 3.5 kg/cm or 48 oz./in. of torque available to it. This level of torque has proven quite satisfactory under extreme conditions including some very fast Dynamic Soaring. A week of evening building sessions should be more than ample to see an Acacia II flyable. Anyway, that's enough construction stuff lets go fly the thing!

Flying

The test flight was nothing to worry about. Being essentially identical to the earlier Acacia meant I could use a well defined transmitter memory from my Mk1 Acacia, and know it was likely to be nearly spot on straight away. I added a little extra nose weight just for good measure and lobbed it off into the wide blue yonder (yup, it wasn't raining!).

No surprises, it was just as good as the old one, but what about that larger tailplane? Well, the only way I could ever provoke anything that vaguely looked like a flick with my old Acacia was to get to height, heave it onto a wingtip, and fly a knife edge circle gradually pulling in more and more elevator until I reached full up, then, just very occasionally it would tumble out a little, so how would the new one fare? It wouldn't do anything at all, and ever since then no amount of hard pulling or tight turning has produced a flick.

Also, the Acacia II feels a little more directionally stable and requires a little less attention when you 'park' it in the sky whilst wandering off to find the landing zone. Nothing has changed with the roll rate though. There are a few things the Acacia does exceptionally well and one of them is roll. The roll rate is fast and precise; it can be stopped and started very easily making four and eight point rolls a doddle. It's also a great bonus when racing close to the hill, perhaps in turbulent air, the wings being easily levelled and finely adjusted.

Landings under full crow are also a pleasant experience due to the excellent response. I have yet to fly another model of similar span and weight that has the roll control of an Acacia. Pitch response is good, yet not twitchy at speed. There is always plenty of bite to pull hard around a turn at speed, even when flying slowly. When flying with a fairly rearward CG, as I tend to do, there is an element of tucking when diving from height. This is easily controlled though, even at the highest speeds, with the merest hint of back stick, and it disappears as soon as the model is levelled off. This is a small price to pay for having a rearward CG!

I should point out though that the model performs superbly even with a forward CG. As far as racing in F3F goes, the Acacia is perhaps a little wider around the turns than some others. It can be pulled tight, but tends to bleed off speed a little if you do this. Every cloud has a silver lining though and in this case it's acceleration. Show it a bit of lift and it's off! Stick the nose down and the Acacia will convert height into speed very quickly.

Aerobatics are easy with this model; vertical stuff merely requires adequate lift, with the negative manoeuvres being easily achieved with little down elevator travel. Rolling manoeuvres are easy due to the excellent response; even rolling circles are easy for an Acacia. Flicking manoeuvres will require you to have stupid elevator movements, or rate switches! I have also used both old and new Acacias for Dynamic soaring, a discipline that can be hard on airframes due to the enormous speeds and g-forces, and the Acacia accepts this with ease. The acceleration means it winds up to speed quickly, and the roll response and precision is a great benefit when travelling at high speed relatively close to the hill.

The ballast tubes are not huge and definitely smaller than other equivalent models. However, this is no disadvantage as the Acacia rarely needs full ballast even on very windy days. In fact there is an advantage to this in that when it comes to landing on a windy day you have a model which isn't too heavy and any unscheduled arrivals aren't made worse by the model being extremely heavy. This points to the model being naturally slippery.

One week after test-flying the Acacia I took it to a UK Winter League F3F event. This particular event was being held on the Bwlch in South Wales. The easterly wind meant using a cliff face known as the 'Crest'; this is truly an awesome slope and produces monumental lift. On this day the wind speed was probably a constant 45/50 mph on the edge. Three quarters ballast was adequate and I was rewarded later in the day with some excellent lift allowing me to fly around the course in 33.48 seconds, the fastest time of the day. The Acacia was up to the job, the only limiting factor being the available lift and my thumbs!

Summary

The Acacia II is an excellent machine. There is very little I can find to criticise about it. I have said before that no model is perfect, they all have some failing somewhere, and the perfect ones tend to be very expensive! That's their failing I suppose. The Acacia II is very reasonably priced and is immense value for money. It's definitely a 'Hot Rod' rather than a 'Fast Cruiser' and perhaps if your looking for a relaxing ride it might not be the model for you, but if you want to go fast and have a blast, then it's ideal

Specifications
Span:       2780 mm
Section:   RG15
Weight:    2400 g + 1000 g
Price:       500 (see note below)

The Acacia II is available in the USA from Composite Specialities, 2195 Canyon Dr #D, Costa Mesa, CA 92627, USA 949-645-7032, tom@f3x.com http://www.f3x.com

A deal is currently being struck that should see the Acacia imported into the UK by Europa/Soarhigh Models 01888 560446 guy@soarhigh.co.uk as the terms aren’t yet final the quoted UK price may vary slightly.

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