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Mystic 40/60FS


Martyn K
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Most of the mechanical retracts that I've come across have needed a 22mm total throw which is achieved using a low profile 180 degree retract servo fitted with an 11mm radius arm. The dedicated retract servos are flat enough to mount upright inside most wings such that the pushrods are completely under the top skin so nothing protrudes up into the fuselage. The 996 should do the job though, just make sure you are engaging the retract locks in both up and down positions.

Once set up mechanical retracts are rock solid but you will use a separate retract battery won't you? The only issue I've had with mechanicals is with play developing or the trunnion blocks splitting in plastic units.

Ps - with a proportional servo, a touch of servo slow will reduce the loads on everything!

 

Edited By Bob Cotsford on 05/05/2016 10:23:21

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Cheers Bob

 

I have never actually looked at a dedicated retract servo. I probably wouldn't recognise one of I fell over it.

There is already a little bit of play in one leg - it sags very slightly but I can fix that. The revised arms are now enclosed completely within the wing apart from where they are connected to the servo arm. I'll use a separate battery as suggested - a 4x AAA NiMh should suffice,

Good idea about slowing the servo down. On the Taranis this is quite easy to do.

I am quite pleased with that, it seems far more positive and more reliable than the electric retracts that I used on the Magic

Cheaper as well

 

I used these:

RET-LG01/40192 Alloy Based Mechanical Retract Set for 0.40~0.60 Class Model ( UK Warehouse ) = $12.85

They are certainly strong enough for a 60 sized model although the quality of the plasticene metal used in the legs leaves a lot to be desired. I'll probably replace the legs with proper piano wire.

 

Martyn

Edited By Martyn K on 05/05/2016 11:51:48

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A bit slow this week. I am glad to say that apart from Sunday - completed laying a patio I have been out flying. However, some progress has been made

dscn2932.jpg

The wing braces are cut from 1/2 x 1/4 spruce and tapered in both directions to accommodate the dihedral. Webs added etc, tapering from 1/8 from te centre bays > 1/16 from the u/c bays outwards

There is one thick full length balsa rib at the centre. This is slotted for the single LE dowel and sanded to a slight wedge for the dihedral.

dscn2933.jpg

I have now started thinking about the engine. Here it is

Its a rear exhaust and I need to get an extension to the manifold to link to the pipe. Its 17mm outside diameter. I am not sure how to connect to a pipe. Can anyone who has done this before provide me with some guidance please?

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Another view. Nice to see a pressure nipple present

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The wheel wells have been filled out with soft balsa wedges

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Quite a decent sized gap all the way round although the wheel is very close to the inboard wing rib

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Wing tips are quite thick - 4 laminations of 9mm balsa, cut and carved to shape then hollowed out with a dremel. Now glued in place and sanded to final shape

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At the tail, a piece of 3mm ply inlaid to support the tail wheel bracket

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and last night, the wing mounting plate 1/8 ply and 4mm bolts fitted for the wing mounting

Finally, at couple of nights ago, I had my first dry fit and everything fitted perfectly

assmbled-1.jpg

One use for the new patio..

More to come

Martyn

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Thanks for that SN... The planet hobby link shows how the pipe is retained. nerd

Currently discussing with Weston for a custom header and manifold but its likely to be a bit costly - at least now I know how the header is secured so I can have a go at bending my own. Much Appreciated

Martyn

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  • 2 weeks later...

A bit more progress - not much as I am waiting for Servos - which I have yet to order.. frown

dscn2945.jpg

With the wing bolted into place, I can start work on the tuned pipe tunnel and lower fuselage. Lite ply formers and soft balsa cheeks.

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Planed and sanded to shape when the glue has dried.

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The retract servo which was sitting through the wing has now been boxed in..

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The tuned pipe has been test fitted, this is the one I used on the Gangster 63 so is probably too big, I have another shorter option but its unbaffled, I may need to spend some cash on a new pipe. I'll see what it runs like when I get it set up.

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A couple more dry assemble shots, the rudder has been fitted

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There is a lite ply cap under the fin extension to add a bit of strength. Still needs a bit more sanding down here

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Ailerons fitted - laminated from 2 x 3/16" balsa

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The observant will have noted that the retract legs weren't seating properly when retracted. This was because the axles were too long - now shortened and wheels retained using collets - I preferred the Nyloc Nuts that were previously used as the axle had a threaded end which needed to be removed

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And the Canopy fitted - this came off another model and has been trimmed to fit. I may take a mould using plaster of Paris in case I need to make another in the future. Small balsa triangles added to blend the cockpit edge into the fuselage.

dscn2954.jpg

Finally, a front view. the wheels are straight, the camera distortion isn't

More to come - but probably not until after the servos arrive,

Martyn

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Thanks, Nice to have a bit of feedback

Not really sure on the tunnel. I am half inclined to leave it as is, there isn't a lot of space available and I am also trying to keep the weight down. My original plan was to widen the cheeks from the fuselage sides up to the point of almost touching the pipe and then leave it as is. However, now you have triggered my conscience, I may go for 1/32 balsa sheet with a 60g glass covering for toughness. I am not intending on glassing the fuselage on this model - I have had far too many problems with paint recently and I am also a bit concerned about keeping the weight right down at the rear end. However, the tunnel is around the CG and a little extra weight should not be too much of a problem.

Mounting the servos for the elevator and rudder looks like it may be a bit troublesome. I was originally intending on fitting them behind the angled former that delimits the end of the cockpit but it is very tight for space. I may need to install some midi sized servos here, they will be powerful enough. The space problem has been compounded because I am using a closed loop for the rudder

Alternatively, I can fit them through the cockpit floor and have a painted canopy...

Martyn

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Corona 339MG servos are rated at 5kg.cm and are midi sized Martyn. I've got them in my 60 size electric ARTF Curare. Only around a fiver from HK, and there's a HV version available too. Of course with the work you're putting into this you may want to go upmarket with HS225MGs though so far the Coronas haven't let me down.

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Thanks Bob

I have been very happy with Corona servos in the past, I find them to be one of the better cheapie brands..

I was considering using these again - TGY-306G - they look and feel good quality - a bit like an MKS clone TBH but I'll take a look at the servo you have suggested as well.

I am using 2 of the 306G for the elevators on my Aurora (one each) and also got them in the bubble dancer glider as well. They are fast and seem to centre OK but too early to say how reliable they are.

Martyn

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The spec looks good on the TGY-306G, metal case so they should be sturdy but they don't look to use mounting grommets. I'm a bit wary of mounting anything rigidly in an IC model - it's the way I was brought upsmiley. Mountings do seem to be a weak point with plastic bodied Corona servos, the lugs do seem quite brittle.

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That's a very good point Bob. I normally mount this type of servo on a strip of rubber and don't over tighten the securing screws so they float slightly. I think a better way would be to mount the servo tray on grommets. I have just checked the Aurora though and I have simply screwed them directly onto a plywood plate. I'll need to keep an eye on them

Martyn

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  • 3 months later...

A bit more progress. The rudder and elevator linkages have been done and the model has been covered.

dscn3175.jpg

The photo doesn't do it justice. it looks like a nice Daffodil yellow, the reality is that its somewhere between sulphur and chromium yellow and looks far more caustic. It is really horrible

But too late to worry about that now.

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Underneath its a much more user friendly sort of Man Utd colour scheme

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Next job is to fit the aileron servos and linkages then mount the engine to check the CG and finally make a plug for the cowl

Getting there slowly. Need to get this out of the way so I can get on with the chippie.

More to come

Martyn

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  • 6 months later...

Not yet, but getting very close.. I waited 3 months for the header to be made (appears my original order did not get processed or got lost somewhere) and then other builds just got in the way.

I fired up the motor for the first time a few days ago and woke up the neighbours.

It is just about ready to go, Just needs a better retainer for the pipe at the rear end
Possibly tomorrow.
Martyn
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I actually made it out of 3/16 balsa with a lite ply inner. It was much easier than I thought it would be and allows very good cooling ventilation and access. It also maintains the original profile as well although its obviously more open from the bottom. I can also remove the engine easily as I have used self tappers into a nylon mount

I am amazed that I couldn't find any completed photos of it. I'll redeem that this weekend.

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Gimg_0369.jpgMaidened it today. Flew very well but the CG was too far forward.  Apart from that it was a absolute deam albeit very fast with superb vertical performance. Prop is an APC 10x8 running on 10% nitro.

Down in one rice but lost a wheel collet on landing which prevented a second flight today. Just needs the A and E throws reducing slightly. I can see this being a favourite. Didn't seem too loud either

img_0371.jpg

 

Finito

Martyn

 

Edited By Martyn K on 25/03/2017 18:12:23

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