Erwin 5 DS – Part One

Erwin 5 DS – Part One

Yes, I know it’s an unusual name for a model. I suppose the meaning got lost in translation between the Erwin’s country of origin (Austria) and the English speaking world. However, look up the term ‘man jewellery’ in the 2006 Aeromodellers Glossary of Youth Lingo for Luddites, Curmudgeons and Fogies and there’ll be a picture of this model just after the purple anodised R/C helicopter parts. Sleek, black, pointy, as high tech as you dare and not a scrap of paint to blemish the pristine, hollow moulded, heavy carbon, twill weave cloth finish. The Erwin looks like it’s been stolen from a secret Formula One car testing laboratory and given control surfaces. There really was no other model for me to choose as my next slopey sportster.

WANT ONE
I’ve had my eye on an Erwin since before it had a name. I bumped into a German guy at a DS session at Rushup Edge some years ago and witnessed him piling the prototype into the hillside on purpose to see how easily the wings came off. With its sleek, pointy mainplane and almost stealthy, pre-historic appearance the model instantly went onto my mental wish list. This was bolstered somewhat when German Stefan Sieman turned up to campaign one at the English Open F3F event in 2004.

Fast forward to early 2006 and Dave Wright, ex-UK importer of all things glidery and fast, decided to blow the cobwebs off the old business and start up again, this time under the name of T9 Hobbysports. Included in his new range was, surprise, surprise, the Erwin! With the promise of a fairly short waiting time (models like this are usually built to order) I committed a chunk of my wage packet and waited. Six weeks later Dave called to say the model had arrived in Yorkshire and asked if Id sneak across the Pennines from my native Lancashire to collect it under the cover of darkness… so his mates wouldn’t see him fraternising with a Red Roser!

Article continues below…

Enjoy more RCM&E reading in the monthly magazine.
Click here to subscribe & save.

With the model safely back in Gods country I set about reading through the not inconsiderable amount of information supplied in the instruction booklet. This is unusual in itself; I’ve paid lots more for similar models and all I’ve received with the kit is a bit of bubble wrap! Got some of that with this one too, but it’s in the form of wing and tailplane covers. The exposed carbon finish gets impressively hot sat on the floor in the sunshine so the bags are a must. Remove the model from these in like-minded company and the reaction is always the same, audible ‘oohs’ and ‘aahs’ with a clamber of pilots just wanting to hold it, but concerned by any fingerprints they may add.

BENDY SISTER
Now the Erwin 5 DS has a bendier sister, the Erwin 5. The only difference between the two is in the lay-up of the main spar and, accordingly, the slight weight difference. Outwardly the versions are identical. Both are supplied with a two-piece, tape-on wing, a one-piece V-tail and a two-piece fuselage that has to be joined by the builder. The Quabeck HQW/1,5/7 (modified) section wing spans exactly 2 metres and is braced across the middle by two steel wing joiners (or one steel and one carbon if you want to save a bit of weight). The decision to supply the kit without colour (top surface colour is available at a small extra cost) showcases the quality of the build. Anything that lets the buyer view the intricacies of the completed biased carbon cloth lay-up must have a little attention paid to the detail, and in this respect the Erwin is truly exceptional. It also makes for an extremely lightweight airframe.

More unusual is the physical lay-up of the wing. Balsa or Herex is usually sandwiched between the innermost and outermost layers of the wing skin to provide some torsional strength. This has long been the established way to produce a hollow moulded wing, but from a manufacturing point of view can be quite a pain. However the Erwin, following a modern trend, uses no such material. The lay-up of the wing skins is simply fibreglass and carbon pressed together in the mould with a liberal dose of epoxy. The increased torsional rigidity is provided by both the 45° lay-up of the cloth and the inclusion of additional sub spars and shear webs into the wing. The resultant panel is very stiff and very resistant to twisting. Also with the absence of the ‘filling’ it should be much easier to repair if damaged.

Article continues below…

Span-wise, the slender section means that there’s some spring in the spar. More so than my other DS models and somewhat removed from the current trend to build impressively bullet-proof DS aircraft with many heavy layers of carbon in the wing. Maybe it’s a DS ‘Lite’ model without the frills. That said, the guy on Rushup was ‘giving it rice’ as we say up ‘ere, and the model didn’t look so bendy there. There’s also a little noticeable flex in the skin when it’s compressed between finger and thumb, but this is hardly a force you’d expect to experience in the air.

The wing control surfaces are all bottom hinged and top driven to promote slop-free movement, with gap seals and wipers that produce a nice whine on a fast fly-by and can accent the breaks in a multi-point roll. The ailerons are fairly small, with extra ‘flicky up’ bits at the tips. These are hinged at an angle, taking the hinge line to the wing t.e. and into the wing tip area, thus eliminating an additional drag-inducing vortex from the aileron end. This additional control surface is actuated by the main surface via a floating wire in the t.e.; the wire actuator is fairly easy to fit and can be subsequently engaged / disengaged with the control linkage disconnected and the surfaces drooped to their travel extremities.

Small ailerons mean that the flaps must be slaved via a Tx mix to facilitate a faster roll, and tiny elevators mean that nothing special is required in the servo department. Just as well, because the R/C has to be mounted to a ‘skid’ that slips into the nose of the fuselage, and this leaves little room for high specification gear. In fact the limited space in the nose means that in practice you have to plan your installation way ahead.

Article continues below…

The back end of the DS version is driven by tubular aluminium pushrods supported at the mid-point by a simple balsa former that has to be installed before joining the fuselage halves. The tailplane is attached with steel Allen bolts, whilst at the front youll note there’s no removable nose cone. Some ballast provision is available with a little work on the wing between the joiner tubes.

GOT IT TAPED
I mentioned earlier that the wing is taped on maybe not such an absurd idea, if you think about it. Most in-flight forces follow the wing, and any mounting method is really just designed to keep the fuselage attached. These forces are increased a little when g is applied, of course, but you’re still only really holding the weight of the gear in the body. Try wrapping three or four turns of Sellotape or Diamond tape together, then see if you can snap it in tension without nicking it first or doing yourself a mischief.

The Erwin’s wing seat and centre section is moulded in a way that permits it to slip off and shear the tape in the event of a crash. The lack of steel bolts through the fabric of the wing means that there’s no chance of leaving any of it behind as it parts company. If a shear force is applied the tape does indeed give way readily and the wing pops off nicely, disconnecting the wiring loom as it goes.

Article continues below…

That’ll do for now be sure to check Part Two as I move on to radio gear selection.

Subscribe & Save

Save £s and get RCM&E magazine delivered to your doorstep every month by subscribing to one of our amazing offers here.

Subscribe