Seagull Boomerang V's Ripmax Wot Trainer

I've been asked to put together a couple of models and thought it would be an ideal excuse to compare them. First up is the Seagull Models "Boomerang" to be followed by the new Ripmax "Wot Trainer". They are both 40 size, high wing, 'Basic Trainers' with semi symmetrical wings. So which one is better? Well, I'll be the first to admit that I have a soft spot for the Boomerang, but I also have great respect for the designs of Chris Foss (the designer of the Wot Trainer) so I'm starting off with an open mind...

Assembly

Seagull Boomerang

The Boomerang has been around for a while now and Seagull seem to be a company that listens to it's customers, making improvements to the kit all the time. Early kits suffered from weak undercarriage, hardware that didn't fit and a host of other small problems. However, by listening to feedback, they have ironed out many of these problems.

I've built a few Boomerangs in the last couple of years, so the manual was quickly set aside, it has to be said though, one area they have failed to improve on is the build instructions.

The airframe was put together very quickly (under 2hrs) with no adjustments or modifications needed. I noticed that, since I last built one of these models, the design has been altered slightly to increase the glue area for the tailplane. They have also added an antenna tube through the fuselage and made improvements to the weight distribution (it balanced perfectly with an Irvine 46 up front).

I haven't covered the actual assembly of the model in any detail as it was incident free, and is described in detail the "Basic ARTF Assembly" acticle.

 

All the supplied hardware seemed to be up to the task and another 2hrs had the radio installation completed.

The only items replaced from the supplied kit were the wing bands, it is still supplied with a bundle of very flimsy looking tan bands. Although they are now supplying aluminium dowels instead of the wooden ones which can soften after exposure to the burnt fuel oil. I also replaced the supplied wheels with 3" rubber wheels, this is primarily to suit our soft grass runway. Arguably I should also have replaced the spinner as it doesn't meet safety guidelines (the radius at the tip is less than 7.5mm).

So much for the Boomerang. A traditional glued up design, there seems to be plenty of strength to handle trainee abuse but, of course, the strength is entirely dependant of proper gluing of the joints. The method for gluing is (partly) covered in the manual.

 

Ripmax Wot Trainer

The instruction manual is actually pretty good, what it lacks in wordy descriptions it makes up for in clear colour photos - I like pictures

Unfortunately that was the highlight of the build. Unpacking the pieces, I was confronted with loads of wrinkles on the covering, given that both models were bought at the same time from the same shop and stored together this can only be down to how the distributor is storing their stock or the quality of the covering. On the bright side, the fuselage seems to be of fairly solid construction.

First up was the engine installation, I've been asked to fit an Irvine 53 in this model. Should be a bit of a hooligan, but since the crankcase is the same dimensions as the 40 and 46 I didn't see the installation as being a problem. Unlike the Boomerang, the engine mounts weren't pre-installed, though the firewall was drilled and the nuts in place. Fitting was fairly straightforward, but one of the captive nuts was stripped and had to be replaced. I had expected the engine to be a drop in fit, unfortunately though the fuselage has to be cut out to allow clearance for the needle valve and exhaust. The instructions did mention that this might need to be done, and reminded the builder to fuel proof the exposed wood.

With the engine prepared it was time to decide whether to build a trike or tail-dragger configuration, I decided that, as a basic trainer, it should be a trike setup and started to assemble the nose wheel. The mounting block was screwed to the pre-fitted captive nuts, the nose leg fitted with the supplied spacer and installed through the block and secured by the steering arm. The leg is a loose fit in the block and there is no flat on the leg to secure the steering arm - minor points, but they can make all the difference at the field. With the wheel mounted the engine could be finally fitted.

The instructions next describe the installation of the fuel tank, a 200ml unit. Given the size of the tank bay a slightly larger tank would have been useful (plenty of fuel gives an instructor one less thing to focus on). The top of the bay is secured by one screw and a dowel, removing it reveals the engine mount screws protruding far enough to puncture the tank.

I overcame this by adding foam around the front of the tank. The instructions ask for foam to be fitted below and behind the tank, unfortunately, a thorough search of the box failed to reveal and foam. Fortunately, this isn't my first model, so I have foam kicking around the workshop, I'm sure that even a first time builder wouldn't get stuck for too long with this.

Refitting the cover was somewhat tricky as the tank was sitting in the way - this would have been more of a problem if I hadn't already packed the tank away from the protruding screws.

With the front end taken care of it was time to attach the tail. The vertical fin has long studs which slide through tubes in the fuselage, the tailplane then fits over the end of the studs and is held in place by two nuts. The instructions tell me to fit the tail skid - even for a trike set-up as this spreads the load of the two nuts.

The quality of the fit isn't great, with a big gap between fuselage and vertical stab:

The two piece wing is a nice design. I used the same system when I designed my "Biggerang" trainer

The centre rib of the wing is plywood and has a lug protruding from the front edge to locate into a slot in the fuselage former, a single ali tube and a location dowel keep everything aligned while two screws secure the trailing edge. I have to say - I really like that bit. The slightly odd part is that it uses a single servo in the centre of the wing. Surely two servos would have been more practical. The single central servo is mounted on two ply plates protruding from one wing half, this seems to me to leave the servo exposed to damage in storage and transit.

Finally I attached the main undercarriage, this is a stiff 'dural' unit which secures by 4 screws to a somewhat under engineered plate in the fuselage. A common enough design on ARTF's, and invariably the first bit to fail. The undercarriage can't absorb a heavy landing, and often this design will rip the undercarriage and mounting plate out of the fuselage.

Once assembled the model has a somewhat aggressive nose down attitude, looks mean, I'm not convinced it's what a beginner needs when learning to take-off. It seems apparent that the model was meant to be built as a tail dragger, the tricycle gear being an afterthought. In addition to this problem, I couldn't persuade the screw together tail to sit straight.

Before I set out to remove these problems I'll test fit all the radio equipment.

Installing the supplied pushrods was a struggle, the rods are very tight in the pre-fitted sleeves. The real danger here is that a novice could be forgiven for thinking this was normal and subsequently overloading the servos and putting a heavy drain on the receiver battery.

It was also noticed that the nose wheel steering rod would connect to the elevator servo!

According to ripmax, this was a problem on "a few early models that should have been rectified" They were surprised to find out that this was still an issue. The actual problem is that the elevator and rudder push rod tubes have been installed the wrong way round.

I was advised that this could be corrected by slackening the mounting clamp for the pushrods and rotating it through 180deg - In fact there was not enough clearance to do this and it would not have cured the problem of the over-tight pushrods anyway.

In fairness to Ripmax, they did accept the return of a second model that had been purchased at the same time and even offered to take back this partially built model. I have elected to continue the build and finish what I started.

Also, it really does pay to use your local model shop instead of mail order at times. All this was sorted out in one return visit to Uddingston Model Centre, and the proprieror was even persuaded to supply the parts required to make the nessesary repairs FOC

My to-do list includes:

Probably a few other small jobs too.

The first task was to strip down the airframe and remove the top of the rear section to access the pushrods:

While I was dismantling the airframe I handled the fin by the rudder:

Another task on the 'to-do' list - re-glue all the hinges

Removing the pushrods turned out to be simple enough - a little too simple actually, they were not very securely glued in place. With a good view of the fuselage assembly though, it appears to be a fairly robust construction, and plenty of glue in all the joints I could see.

The pushrods were replaced with Sullivan "Gold-N-Rods". Before the top was glued back in place, I cut out the guide tubes for the rear fin and added some blocks to allow the fin to be securely glued in. The studs in the fin are very secure, I eventualy had to settle for cutting them off.

With the top refitted, and the fin glued in square the stabiliser was glued to the fuselage after a little sanding of the mounting area to ensure it would sit straight. While the epoxy was out I also glued the wing halves together.

I bent up the new undercarriage from 8swg piano wire and fitted it into a couple of blocks glued into the fuselage (there is more detail on this method in the "More ARTF Advice" article). The main legs were made a little shorter and a little wider than the original unit, along with an extra spacer on the nose leg this lets the model sit at a more neutral angle.

With the modifications complete the model is sitting nicely:

The radio installation was now fairly simple. The only slight issues were the positions of the servo mountings in the tray:

As you can see, the Elevator and Rudder servos are too close together to allow a straight run for the push rods, with hindsight, I should have cut the tray to allow the servos to be repositioned. More annoyingly, the throttle servo is so close to the end of the pushrod that there was not enough room to properly smooth out the arc of the servo arm.

With the battery and receiver mounted in the suggested position the Centre of Gravity is only slightly behind the recommended position.

Flying

Seagull Boomerang

It's good, actually it's great!

With plenty of control throw it is capable of flying the SAA Silver schedule. Though there are easier models to do it with.

How many "basic trainers" get out there and mix it up with a Sukoi? Definitely VERY Aerobatic (AKA Hooligan) with an Irvine 46.

As for Training, well, enough people have used them in the club to attain their Bronze that there is no doubting it is stable and predictable enough for new beginners. Switching the rates down to 45% and no amount of reckless stick stirring can upset it.

Ripmax Wot Trainer

It's always a sign of a good model if I feel comfortable enough to roll it on the climb out of the maiden flight! Hardly any trimming needed and the 53 engine is ballistic.

As far as the aerobatics are concerned I've no complaints; Stall turns need a fistful of opposite airelon, Bunts need some fast thinking with the rudder thumb and rolls need constant variation to the airelon to keep the rate steady - much as I'd expect from a high wing trainer.

Dropping the rates it is a very capable trainer, the tapered wing means it needs a little more concentration in slow turns but nothing to cause problems and the long wingspan (67") and plenty of dihedral make it stable and predictable.

All in all, once it's flying it does just what it says on the tin. So, does it "redefine the meaning of the word 'trainer'" - Well, to be blunt - No!

With the rates reduced it's almost as good for training as the Boomerang, perhaps with the C of G moved forward a little it would be just as good. On high rates, especially with the overpowered engine, it's very capable - but the longer wing and slightly steeper dihedral angle that make it stable for training really start to work against it. An experienced pilot can make it work, but it needs constant correcting to keep it on track. The Boomerang also needs correcting, but not so much.

The bigger engine really showed up the small tank too, limiting flights to 7-8 minutes. I don't think it would be any less capable with the 46 up front and this might help flight times slightly. Really though, with all that space up front it should have been supplied with a bigger tank.

Summary

Seagull Boomerang

A well proven design that goes together well and will reward the trainee with a stable platform to learn basic flight, but won't loose it's usefulness as you progress to simple aerobatic maneuvres.

Ripmax Wot Trainer

Fairly new to the market at the time of building, lots of problems, some of which should never have make it to production versions.

However, once it has been built it is a very rewarding model to fly, every bit as capable at the Boomerang for basic training, but lacking a little of the Boomerangs confidence when it is pushed to the limit.

  Seagull Boomerang Ripmax Wot Trainer
Specs    
Retail Price £65.99 £79.99
Wingspan 155cm (61ins) 1710mm (67.3in)
Wing Area 39.5sq.dm (612 sq.ins) n/a
Length 43.7ins (111cm) 50.4in (128cm)
Weight 2.6-2.8kg (5.7-6.1lbs) 2.6kg (5.7lbs)
     
Reviewers Rating
Value For Money
Build Manual
Ease of Assembly
Build Quality
Flying

And My Winner is....

No surprises that my money goes on a Seagull Boomerang - Ohh, and I've got enough change left for a gallon of fuel.

Sorry Ripmax/CF, maybe you should have flown a Boomerang - it'd already defined 'trainer'. You've made a good copy, just sort out the bugs and you'll be ready to join the party.

Out of interest, I think the Wot is probably the better looking model. It needs some high definition marking on the top to help with orientation, but I think any trainer benefits from a liberal sprinkling of florescent orange trim anyway.

As ever, these are the observations, opinions and ramblings of one deranged individual. My opinion does not necessary represent the views of HRMC.

copyright 2010 HRMC
Website Created by EDC WebDesign | Content © 2010 HRMC