marc s

I have intended this 'short' build thread to be of help to those customers who have already placed orders for this new jet, and for those generally interested in small 'nano' turbine or EDF powered jets.

The Stinger is essentially a new fully composite sports jet, designed to be smooth over a large speed range, strong and easy to fly with landing gear suitable for use on grass as well as tarmac flying fields. The span is just over 1m and the length around 1.2m.

All parts are composite sandwich construction formed under vacuum, formers are pre-fitted as are ducts, and we have designed from scratch an electric trailing link landing gear system which includes an electric brake system and controller for programming all the functions required from voltage feed to door sequencing and failsafe - we have even incorporated a simple version of ABS which pulses the brakes to help prevent lock up and aids a smoother deceleration.

The build commences with the wings as these are the first items out from the newly made moulds, please note there are a few areas of 'rough' edges around the servo hatches which were as a result of a porous edge to the panel set in the mould to give the recess - this will be modified for final production kits. We also hope to finish the production kits in white rather than the grey of this and the second Stinger which will be built with an electric EDF system.

So wings come with flap and ailerons pre-hinged, servo recess cut and tabbed for the cover retaining screws, currently we live hinge the gear door but we are considering an option to simple cut the gear door opening and mould in a rebate for a separate gear door which the custom can fit or not depending on his choice.

First off is to fit the chosen servos, in our case we have opted to use the MKS 6125 servos, these have nice power, metal gear, great centering and neat accessories. Using one of the servo hatch covers supplied I first needed to position the servo mounting frame which can be purchased with MKS servos to the cover, to make sure it did not interfere with the servo cut out in the wing I turned it upside down and positioned the wooden frame in the mirror position to is actual position, as you can see through the covers its easy to judge this and fit the frame in position without the risk of it snagging.

Once the frame was fitted I fitted a small aluminium servo arm which is also available as an accessory with these servos, and keen to keep the linkage as low a profile as possible I worked out and then cut slots in the cover to conceal the arm, and ball link (which are also supplied in the kit) to the location of the horn. Careful alignment is needed to ensure things line up nicely. The flap and aileron horns which are supplied need to be trimmed, sanded and fitted into slots which need to be cut into the wing skin, balsa blocks are fitted to the inside of the control surfaces to help fixture.

When you are happy with the alignment and throws (these will be detailed later) glue in the horns using a strong epoxy, mask around the horns allowing a few mills of edge to bead some epoxy around the base of the two horns - a cotton bud (Q tip) are great for this.

The servo hatches require a small packing piece of scrap material like thin ply to be glued to the underside to give a good fixing base for the servo cover retaining screws.

Servo leads need to be extended to exit close to the wing leading edge at the root. A hole can be made through the root and then a wire passed up inside the wing to first go through a hole in the first wing rib made for this purpose and then sideways through a slot in the lengthwise rib along side the retract mounting plate position. Servo wires can be run across the retract area as there is space to do so.

The servo hatch covers have small holes pre-drilled in each corner, use these to pilot holes through the wings servo bays, once done open the holes out in the servo covers to suit the fixing screws shank diameter for a relaxed fit.

marcs

marc s

This is the Stinger v1, the v2 is 5% larger with a few alterations to the fuselage profile, duct intakes and a few other small modifications - it will look very similar to the one in the picture flow by Ali at Florida jets this year.

marcs

marc s

After some playing around with linkages finally managed to come up with a system that keeps the servo arm and linkage on this below the wing surface so only the horn is visible, will need to double check the throws with Rich the designer and mastermind behind this little jet but having seen the v1 throws I think we should be good to go.

The servo covers on this version will have additional covers over the top to 'hide' the chipped servo hatch edges, something we hope to fully fix on the production kits.

There is provision through holes in formers to run the extension cables through to the front area of the wing route, the dashed lines show the cable route and the red the position of formers with holes for the run.

Flap servo and linkage, aileron servo and linkage shown for reference.

I am using a 10 way Ashlock connector for each wing, 6 wires for the two servos, 2 wires for the gear up/down and 2 wires for the brakes - no air lines to get in the way

Fuselage is out of the plug in an hour or so will post some work on this next.....

marcs

olnico

Very nice Marc.
Thank you.
Do you have some pictures of the gear?

Henke Torphammar

Sounds good with electric breaks. How much does the airframe alone weigh?

marc s

Pics of the 'revised' gear and airframe weight will be posted soon.

marcs

Jamie C

Marc,

When is the projected release of this model/retract set?

carl.huxford125

Marc,

How do the electric brakes work, i've not had any dealings with them, sounds great not needing air at all

marc s

Jamie,

We are already taking pre-orders, and have quite a few ordered with deposits paid, info on how to do this on my web site. If you pre-order this secures a build number.

When we return from Jetpower the first kits will be made and shipped shortly after this. The gear has already been made and tested however the original in the picture with Ali was air driven, we have changed this to electric and designed a module to drive them, the electromagnetic brakes and the door sequencing which Rich has designed for it so this will simplify the whole installation, reduce pipes and the need for air tanks, valves etc.

PM me if you want to chat over it as I appreciate any purchase from a small company like ours is not a simple decision

Picture of the PCB Rich designed attached, this tiny module when loaded with components will drive three main gears with current protection, it will sequence doors with the gear which will be user programmable, it has a voltage failsafe so if the supply pack voltage drops past a selected level the gear will deploy. It has a simplified pulsing brake system to help reduce lock up and aid smooth braking, which can be switched on or off depending on user preference. Status LED's, voltage regulator to cope with various battery input supply.

marcs

marc s

Carl,

In essence its an electromagnetic coil which sits inside the wheel hub and is fixed to the leg so it cannot rotate, then fixed to the wheel via the spokes is a special 'floating' metal disc which is kept close to the coil, as current passes through the coil it starts to apply a magnetic force on the metal disc which creates a braking force which can be amazingly large at very low voltages - subjet to enough winds of copper wire which I believe is around 500 or so!

Rich who designed it might be able to chip in with a more technical explanation when he sees this.....

marcs

carl.huxford125

Cheers for the info Marc,

Carl

marc s

Nose gear fitting is a simple process, the gear is not quite complete but wanted to test everything fitted so this was the process.

The formers for the gear are all 4mm ply, so solid and more than up for the job. The formers are all pre-fitted for this and pre-drilled. First job is to insert the four brass captive inserts, I found this easier by first screwing in an M3 cap head a few turns into the brass fitting and then to hol dthe protruding bolt with some long nose piers, this allows you to get the brass inserts part was into the pre-drilled holes (which are slightly undersize). You then remove the bolt, repeating for the other three brass inserts.

Once this is done you need to 'draw' the inserts into the former, again using an M3 cap head with a washer to spread the load on tightening you can screw in the bolt until it has pulled the insert into its fully located position. Wind out after this is done, and repeat for the other three inserts.

The gear can then be slotted in from the underside through the door opening and secured with 4 x M3 CS cap heads (provided in the kit).

marcs

marc s

Fin servo mount fitted to cut out in tail, with servo resting in place for reference.

Wing securing is via two M3 bolts which pass through pre-drilled holes inside the wing root in the wheel well area through into the fuselage. Two 4mm ply washers are supplied with two small brass M3 inserts, first file flats on the tops and bottom of each 'washer' so they fit into the root recess inside the fuselage. Press in brass fittings. Apply vaseline to an M3 bolt, add a washer and slide this into the fuselage. Apply aeropoxy or similar to ply washer on the side where the flange of the brass insert is, then offer up the washer to the bolt head inside the fuselage and tighten the bolt to pull the washer against the fuselage - make sure the washer sits flush and is not left to straddle the root moulding area.

In addition to the wing securing hole pre-drilled in the root area there is also a forward access hole provided which mirrors the same hole in the leading edge of the wing root itself, provided to pass cables etc through to inside the fuselage.

Each Stinger will carry its own ID label, and this one is the 0001 version with worts, pimples and all ;-)

marcs

BaldEagel

Great stuff Marc.

Forgive my comment, but for correct geometry should not the servo output for the rudder be at 90deg's to the hinge line? this would also help with the rotation of the rudder horn and strain on the linkage.

Mike

marc s

Yes indeed but we are using a nice ball link so this will be fine, the throws on this little jet are really very small.

marcs

marc s

Rudder linkage now set up and so are the stabs, the rudder cut-out will be re-positioned to give the best linkage geometry.

We are going to add a servo slot in the inner rib inside the stab so that should you wish to house the servo inside the stab itself there is an option to do this, although not finalised yet this may be a customer option on the kits. For me I am happier to mount them in the stab trough a cover, the MKS servo mounting plates fit spot in inside and make for an easy servicable method, the covers are only 0.4mm thick so once painted they will hardly be seen. I can also glue the stabs to the fuselage using this method rather than leaving them removable as would be the case with in-built servos.

I have a couple of comments on the MKS servos which are all positive so far, all work out of the box, the gear is tight and slop free, spare fitting hardware is also supplied which is a nice touch. I have found that the 2mm metal clevis connectors require the tiny metal arms to be skimmed a fraction to get them to fit as they should, a simple little job on the minature mill, or I am sure some sanding would do to. Splines are very fine so you can get nice arm locations and the arms fit very well, infact the metal arms take some work to get them off once screwed down!

We will be supplying a central spine former set, which will be fitted by the builder, this group of formers runs from the back face of the nose gear rear former back to the former fitted to the wing tube, it adds strength to the area underneath and also provides two bays for equipment, mounting plate for fuel tank or batteries depending on power system. I have opted to fit the powerbox switch to one side of the forward bays, so it can be accessed either through the canopy or up through the nose gear door when the gear is down. On the other side I have mounted a tiny 3kg torque MKS servo which I intend to drive the nose gear door with. Its an experiment currently but hope it will do the trick and keep things light and simple.

Once the new cnc'd base plate arrives I will glue this former set in.

Final item is the gear/brake and door controller which Rich has designed and today he finished off adding the components to it - measures 30mm x 35mm, weighs almost nothing and a few mm thick. It will allow user programming for gear sequencing, brake control (with pulse if required), door sequencing and a few other nice touches - a bank of 4 LEDS give indication of status, two push buttons select choices and a multi position switch selects the function. A user guide will be supplied.

marcs

marc s

few more pics.... added one of the fuselage which is not looking its best as I have attacked the seams in preparation for painting but hey nothing to hide

marcs

Bob_B

My Feedback: (11)

Marc,
Looks fantastic! Come-on October.

marc s

Been frantic every evening and weekend working to get the P20 and EDF versions ready for the painter this week, so sorry for the lack of post but the EDF fuselage build up is essentially the same as the Turbine version.

New items worked on are the canopy, this is a moulded glass unit which requires final shaping to get ot he desired it, there is a line around the moulding to which to trim to. Once you have sanded and adjusted to get a relaxed good fit onto the fusealge opening you can assemble the frame. This comprises of 5 lite ply parts, the easiest way to get them to the correct position is to lay them in the correct order flat on the table and tape the pieces together, if you then lay this into the fuselage cutout the frame will shape to fit, carefully and best to use a second pair of hands here is to lift the corners of the tape while your helped holds the frame in position and wick some cyano along the joints, working you way around the frame corner to corner.

Once tacked the frame can be removed and additional cyano applied to the joints to fully set the canopy frame to shape. It will need a small amount of sanding to leave around a 1.5mm gap around its edge so the canopy will sit on the frame but flush with the fusealge.

I then tacked the frame into the canopy at the top of the front and rear (pre-sanding the areas), I applied some wax to the canopy mating surfaces on the fuselage, ran a bead of aeropoxy around the inside of the canopy against the frame, sat the canopy on the fuselage and taped in place making sure the edges were nice and flush - masking tape applied it was left to dry.

We will be supplying a clear canopy section which can then be added after removing the coresonding section of the canopy, in addition a small vac formed cockpit kit will be available to fit into the opening in the frame base.

The EDF version fuselage is being prepared, with the base formers fitted in place after adding the switch cut out and nose door servo mount as in the P20 version. I plan to install the ESC in the area behind the cockpit, in the spine section so added two openings here for some airflow which will be fitted will aluminium grills once back from paint.

Also a general pic of the revised rudder servo position, EDF fuselage and first set of ducts which were fitted in the P20 version late last night! - pics to follow.

marcs

Bob_B

My Feedback: (11)

"The EDF version fuselage is being prepared, with the base formers fitted in place after adding the switch cut out and nose door servo mount as in the P20 version. I plan to install the ESC in the area behind the cockpit, in the spine section so added two openings here for some airflow which will be fitted will aluminium grills once back from paint."

Marc have you considered small NACA ducts on the sides of the fuse directly in front of the inlet ducts for cooling air for both the bats and esc?
Bob

marc s

0001 & 0002 are back from the paint shop in the base colour schemes, later some vinyl magic will be added to further complete the final appearance.

The red version is for the P20, the green for the Schuebeler/MGM Compro/SLS 'eco' version - this sports the vents behind the canopy for ESC cooling.

Will give the paint a day to dry off and then start to do the main installations....

marcs

Couch Potato

Should be green wing, white fuselage, red wing, for the Italians !

Geoff White

Looking forward to seeing the finished versions at JP.

schroedm

My Feedback: (1)

Good going Mr S! I see your Italian roots are creeping out

marc s

Italian, now you say it...........

Was wiring up the wings for the final servo installation and although Rich had placed holes in internal formers for routing the servo and gear cable it was not a simple job to get cable through these holes so out came the trusty bath plug chain and in short time (Rich actually0 the cable runs were laid with draw strings. We may look to add these in the production kits as it would make the builders life very much easier.

One draw takes the aileron and flap servo leads to the wing root, the second the gear and brake cables to the same point, in all you end up with 10 servo wires exiting the wing, no air lines and very much more simple to work with.

After fitting the servos I packed in a small piece of foam into each servo well to make sure the slack leads would not get jammed under the servo arm during flight.

The retracts are mounted to 4mm ply plates, these require the small M3 brass inserts to be fitted by the builder. Holes are supplied pre-drilled in the correct place for these. The easiest method to instal the brass inserts is to hold one in a pair of tweezers (bent nose version) pop an M3 bolt with a washer under the head and screw the brass insert up on the bolt by turning it with a hex driver, once the brass insert starts to enter the hole in the ply it will lock and get drawn up until flush with the top of the ply rail.

Gear can be simply slid into position and bolted down with 4 x M3 CS bolts.

Internally the base of the forward section of the fuselage has two rails which extend between the first nose former and the main wing spare former, the wing spar former has two wide slots, the lower one allows the rudder and elevator cables to pass through from the rear section, the upper slot is to secure the cover plate and also the provide the tabbed fuel tank (turbine conversion option) base plate a rear securing point, more on this later.

The cables feeding each wing also pass into this channel via slots in the two rails place in line with the openings in the wing roots (pre-made). This neatly brings all the wiring to the front area of the cockpit tub for connection to the Rx.

marcs