Geoff's Rans S9 Chaos build

[Geoff S]

I have a few comments and queries on this build so I thought it best to separate it from Peter's original build article.  I'll also try to take a few photos as it progresses.

 

I've built part of the starboard wing and got it to the point of being able to lift it from the board - ie the 'D' section is complete so it won't twist.

 

First, the drawings show a single R1 at the centre and the Sarik CNC parts only include 1 1/8" balsa rib.  In fact, as Peter confirms, there are, as you'd expect, 2 R1s - one for each wing half.  It's simple job to make another using the provided one as a pattern.  Something else I've just realised is that R1 doesn't have a hole to insert the paper tube to guide the aileron servo connection.  The tube doesn't go that far but you need a hole to insert it!  Luckily, I think my Softbore tool will make a decent hole even in the rib that's already glued into the wing!

 

The trailing edge is an 1/8" x 1/2" piece chamfered to 1/16" glued to the end of the ribs with 3/4" x 1/16" capping top and bottom.  The ailerons are made from 3/16" solid balsa 1.5" wide and chamfered to 1/8" at the t/e.  However, the drawing has a cross section illustration of the wing which is rather different:

 

 

 

 

It's a bit confusing (but I am easily confused)  but I think I'll go for the thicker t/e which allows for a 3/16" width (2 x 1/16" cap strips and 1/16" edge for the t/e proper. That cross section only allows for an aileron of 1/8" balsa which is a bit thin to insert a hinge.  In fact, I used the film itself to hinge the ailerons on my Liddle Stik for that very reason.

 

There will (probably) be more to come and even photographs ?

 

Geoff

 

 

[Peter Miller]

PM me your email address and I will send you my original plans which may help.  They are a little different

[Geoff S]

Thanks, Peter.  I'll do that right now.

[Geoff S]

A little progress.  The starboard wing is mostly complete apart from the tip, which I'll leave until the wings are joined and the aileron.  The aileron servo mount is just about done too.

 

 

 

I remembered to fit the paper tube for the aileron servo lead.  Note the Saril CNC cut parts not only supply just the one R1 rib (I made a second) but there isn't a hole for the paper tube so it's best to cut one before assembling the wing..

 

Peter kindly sent me the PDF files of the drawing which includes a drawing of the port wing which is making it easier to build.  It's loose assembled here.  I gluds the bottom l/e sheet to the bottom main spar before laying it out and did the same with the t/e 1/16" sheeting and 1/8" x 1/2" t/e (this is tapered to 1/16" and easier to plane/sand when it's attached to the wider sheeting).

 

 

I really like my magnetic building board.  There is a discrepancy between the taper on Peter's drawing and the drawing in both the free plan and the one supplied by Sarik (which I used for the other wing) which must be due to the rib sizing.  As I've already built one wing I'm sticking to building the taper governed by the length of the supplied ribs.

 

Geoff

 

[Geoff S]

500I'm feeling a bit (though only a bit) guilty about not keeping eager readers up to date on my Chaos build.  Despite my reticence to post the build has actually progressed to the point where I even started a bit of covering yesterday - only the ailerons but it's a start.  There are one or two unusual aspects to this model and the rest is standard Peter Miller creativity many have come to admire and benefit from.

 

The fuselage front is a bit tricky because it's rather wide and needs to drawn in at the firewall over a fairly short distance. The starboard balsa side cracked on mine but was held together with the ply doubler and I managed to repair it successfully.  Assembly would have been difficult without my ancient and well-used SLEC fuselage jig. See here:

 

 

Incidentally, I opted to adapt the battery tray access slightly to allow the possibility of using a 4S 4AH LiPo (because that's what I have as my standard and I have a few) should it become necessary.  I'm still hoping to use a 3S 2200.  I also cut out the fuselage formers aft of the wing to allow free passage of the carbon pushrods I intend to us rather than the snakes, Peter suggests.  In any case, from discussions elsewhere, it seems it's better to clamp the ends of snakes firmly and leave the intermediate length free to avoid any temperature induced expansion/contraction effects on trim so perhaps it's better to leave out the intermediate snake anchor points anyway?

 

Something else that I pondered over was how to treat the ends of the stringers near the fin. I left them fairly long but they're very vulnerable to my clumsiness and a couple got broken as I manipulated the fuselage on the bench. These are the ones I mean:

 

 

 

I ended up doing this after fitting the fin and tailplane:

 

 

The rudder and elevator are only fitted temporarily, though the hinges are fitted (and pinned!).   The tail plane platform on the drawing and as provided in the set of CNC cut parts ends at the tailplane l/e leaving the front of the rudder unsupported.  I added an extra piece up to the last former. The stringers are supported by very soft balsa blocks or continued to the fin itself.  After having a fin break on a test flight many years ago I'm a bit paranoid about fin support, hence the triangular stock support.

 

I quite like carving soft balsa, so I enjoyed making the cowl but it's a bit knife and fork - almost like sculpture ?   I'm quite surprised how easy it is to attach or remove for motor access using Peter's keyhole method.  I reversed the hatch catch and dowel positions from the original design. The catch is at the back and dowel, now at the front, extends into the hatch and acts to prevent its sliding down and becoming loose in flight (actually it's quite tight anyway but it's better safe than sorry):

 

 

 

 

 

 

 

I used 3mm liteply for the front.

 

 

 

 

[Geoff S]

Another feature of the model is determined by the mid-wing design.  The wing attaching bolt is accessed through a hole in the bottom sheeting to screw up in to the wing. Unusually the captive nut is in the wing rather than the fuselage.  Here's the bolt, held in place with a 'O' ring which lies in a recess when the wing's fitted:

 

 

Note that the rear part of the canopy is fitted and is thin ply rather than transparent because the full-size I've chosen doesn't have either a rear window or spats - both plusses for me ?

 

It's easy to access at the moment because I haven't fitted the bottom sheeting and I can get my hand inside.  The bolt is about 3" from the bottom and I'm expecting it to be difficult to centre the screwdriver on the screw slots, blind and inches from the access hole.  I think I may have a solution.  I thought a lightweight tube guide from the bottom sheeting to the screw might help but what to use for a tube.  It's over 70 years since I made a glove puppet at school using papier mache.  Then I used flour and water paste, to make my papier mache tube I used newspaper and PVA wrapped round a length of aluminium tube protected with cling film.  It seems to be a success so far and weighs less than 5 grams.  It cost almost nothing in either time or cash.  In fact I'm wondering what else might be made this way as it seem quite strong. 

 

 

 

Here's the wing.  I've checked the incidences when attached to the fuselage and taking the tailplane platform as a reference and everything is zero degrees.  The top of the wing is flat and only the underside taper provides any dihedral:

 

 

One reason I haven't been posting is the difficulty of taking decent photos in my cramped workshop as you can see here.

 

Anyway, that's all for now.

 

Geoff

 

 

 

 

 

[Geoff S]

Well, despite the lack of posts my Chaos is now flyable, though there's still a few scale/cosmetic additions to be done - wing struts, tail rigging and a pilot as well as some decoration like registration letters etc.  The undercarriage is in need of some cosmetic work, too, but, fortunately, no spats.

 

 

 

I've set up the control throws and CoG, with a 3S 2200 LiPo comes out exactly as the drawing - 3" back from the L/E at the wing root.  However, the text in the magazine quotes 2 3/4" back, so for safety's sake I may need to do something about that. 

 

As it stands it weighs 3.62 lbs ready to fly.  With a 12x6 propeller it draws 30 amps for 330 watts consumption.  That's a bit less than 100 watts/lb. However, the motor has a maximum current rating of 46 amps and the ESC is a 50 amp one so I can easily up the prop size either by diameter (13x6.5?) or pitch (12x8?). I prefer low pitch props for acceleration rather than coarse for speed but I'm sure the 12x6 will fly it OK so I'll stick to that for the maiden.  Lots of options there.

 

 

 

This shows the papier mache screwdriver guide tube and the wing bolt held in place with an 'O' ring (as well as the 3mm carbon push rods).  It's still a bit fiddly to access the 6mm wing bolt but it seems to work OK and the wing fits well.

 

The model is far from perfect but it looks OK from 50 feet ?   I tried Peter's rudder covering method but found a hot air gun too much (at least with mine).  I had better (though not perfect) results using my covering iron set to 150 deg C, I think because it was more local heat and limited the edge pull back. 

 

I'll be fitting the struts and rigging wires today.  I have a pilot that came with a Hangar 9 60 size P47.  I replaced him because he is grossly too big.  I think he's nearly 1/4 rather than 1/5th scale and ugly to boot but, like the covering film, he's what I have in the drawer and I'm trying to avoid buying new and use up my clutter.

[Lucas Hofman]

Have you already flown Geoff?

 

Lucas

[Trevor]

I've only just caught up on this one Geoff. I like the idea of using the hatch dowel to lock the cowl in place. If you do need to go up a prop size, the APCe 13 x 6.5 is a favourite of mine for 4s models but then, like you, I'm generally not on a quest for speed.

 

Good luck with the maiden.

 

Trevor