The Multi-role Micro Ultra Stick (MMUS)

Well, I'm not quite sure what has possessed me but for some reason I have set out to scratch build a plane. It all kind of started when Paul Daniels from NQRC mentioned to "the crew" over at Aussie BBQ and Beers at rcuniverse that he was starting on version 3 of his easybox balsa kit.

I mentioned it would be great if we could get a version that could be an indoor/outdoor flyer, enough wind penetration and power to fly in some wind, aerobatic, all in at 30" wingspan etc. Yes in other words all things to all people. I made one tiny, and probably in the long run irrelevant concession to reality. Indoors it could fly on 2s LiPo, outdoors on 3s LiPo.

So, rather than encumbering some other poor person with trying to build the unbuildable I decided to have a go at it myself instead. After all, why shouldn't a novice start with a finely balanced compromise between the best attributes of indoor, outdoor and aerobatic flight...

I haven't tried to dream the whole thing up myself, and have instead decided to loosely base the design on the Eflite Mini Ultra Stick, using its shape and proportions of wing span/wing chord/fuse length etc. The airfoil is a rough copy of the Mini Pulse XT (RIP).

So - without any further ado here are some planned vital stats:

Wing Span: 760mm
Wing Chord: 200mm
Type of Wing: Flat, built up, constant chord balsa wing.
Length: 660mm
Type of Fuse: Box fuse sheeted balsa
Wing Area: 1520 sqcm / 235 sq inches
Power System: GWS 2205 Outrunner and 2s/3s 450mAh Elegance LiPos.
Power Output: 45 watts (2s) / 70watts (3s)
Target AUW: 230g (8.2 oz)
Wing Loading: 4.6 (2s) / 4.9 (3s) (oz/sq inch)
Power to Weight: 100 watts/pound (2s), 135 watts/pound (3s)

My apologies for mixing my units between SI and Imperial - still those that work with SI are used to having to cope with non SI.


The Prototype Wing

Well I have started. The first prototype wing has been built. At the stage of these photos the main structure is done, although I have added some wing tips since this.

Already I have figured out some improvements - namely making the secondary wing spar (the vertical bit at the top of this photo) once continous piece and keying the longer ribs into it (in the prototype it is three pieces). Also, by making the wing spars a fraction longer it is possible to build the necessary support for the wing tips (not shown in these photos) into the spar.


The prototype wing took about an evening and a half of cutting out balsa and putting together. Because the wing is small I was able to do most of this sitting in front of the telly.

The hardest bit is definitely cutting the ribs. The spars are dead simple to make using a balsa stripper (see your LHS). For the ribs I cut one of each type (there are two types of rib) and used that one as a template to cut the rest finally holding them all next to each other and squaring them off with one another as best as possible. Some scratch builders have suggested to me making a template out of plywood - I'll have to look into exactly how they do that.

There's not much to say about assembly (I think). Start by keying all the ribs into the slots in the main wing spar (and secondary spar). Make some approximate 100mm marks on the leading edge block, leading edge support, tubular spars and the unkeyed ribs on the second wing spar. Start with the leading edge support and tack glue the ribs into the correct place. Then secure the back of the short ribs in the correct location along the secondary wing spar. Push fit the tubular spars (lining up as best you can) then tack glue the leading edge block. Tack glue tubular spars to ribs and glue ribs into main wing spar. If you are lucky it will look vaguely straight - if not - don't panic covering can fix many problems.

Fuselage

Watch this space. Will be a boxed up fuse (1.5mm balsa), probably nothing on the bottom. There may be some 3mm stuff just to provide some reinforcing in some places. Getting CoG on target will be vital if I am to be able to easily swap out 3s and 2s LiPos to reduce wing loading for indoor flight.

CAD Files

Anyway, I've done some CAD files - one that shows the wing ribs (there are two types) that need to be cut, and the second with a full plan of the built up wing. Watch this space for details coming soon on how the fuse is put together.

Such as these CAD files are of any use to anyone, you are free to download and modify to your hearts content. You may share them with others, host them, etc, but may not charge a fee, except reasonable costs associated with sharing them. Also you must transfer these same rights to any person you pass the plans onto.