June-09

The lasers at the tip will give us the wing twisting with bending data. We are interested in this especially because of the sweep forward. The Mx load test was done and some records of deflection at the cut tip. While the wings were loaded we measured push rod forces to give deflections. These become quite noticeable with wing bending, but are still a lot less than the predicted forces due to aero hinge moments on deflected ailerons.

It's not clear from the photos but we have the unloaded wing angled up at about 6 degrees. This was just to allow more deflection and reduce the tendency of the bags to slide off. The tip deflection (if the tip was re-attached) at limit load was 994mm so we have 181mm/G. Some load tests still to do on the wing and also some more stiffness tests.

June-09

The wing tips are not joined back on yet, but this is an easy local load test to do later.

The first test we did was to check aileron torsional stiffness. The wing tip has a wooden clamp around the section to allow mounting of some laser pointers (from $2.00 shop) and to help stop bags falling off the end etc. This allowed us to clamp the aileron tip and then apply a torque to the aileron root. The applied moment was 13.6Nm for the deflection shown.

The Mx sizing load case, the worst Mx at each spanwise station from all load cases, was basically our gust case at Vd with the heavy pilot with a calculated limit n=5.5. Our n for the light pilot was higher but the net loads were lower. The gust case at Va showed just slightly higher on the outer part of the wing, but as a simple concept, our sizing case was the Vd +gust case. This load was approximated by a distribution of 16 bags of 32kg each. As the real life load distribution is modified a lot by the uneven mass distribution in the wing, we carefully matched the L/dy distribution of the bags as best we could.

May-09 June-09

Various ideas for the wing Mx load testing were considered. The tests with wings fitted to fuselage had too much risk of damage to the fuselage. There are no easy ways on SG-1 to react the loads from sand bags on the upside down wing. So we elected to build a steel test fixture. We chose to test one wing at a time, and react the large moment with an outrigger shape from the root fixture. The test rig was designed to be safe for a later failure test of the wing, so for the current limit load test we have a j=4 for the rig.

The test rig has bronze bushes glued into the steel with the wing in situ. The outrigger goes flip flop to suit the port or starboard wing. Only the rear shear fitting is used for this Mx test. The front shear fitting is designed to react loads in the x axis and any contribution to reacting Mz or Fz or Mt is ignored.

May-09

The wings need to be cured in preparation for their load test. Different components in the wing will be in different cure states, but all will have an assumed HDT of over 60degC, and our cure temperature will be just below that. The most recent resin samples were tested in a crude way for the temperature that made them deform with moderate force. A thermostat and thermometer sat in an electric kettle (shielded element) and the samples were given ample time to assume temperature. So we had some confidence on stability during the cure.

A series of wooden (dry wood) frames cradled the wings and set the geometry for the oven walls. Some old computer fans were set to blow air into the wing interior. This I hoped to enable more even heating on the inside/outside of the wings. We tested some cheap fan heaters in our normal hotbox to see if they were happy running close to 60degC. The only problem is that their thermal cutout switch is set about 60deg, so it is easiest to stay below that temperature. Later we will try disabling or shifting the cutout temperature to enable 60degC.

So in our curing box we had four fan heaters running hot along the bottom, being switched by two thermostats. We also had four fan heaters running cold, so we always had circulation. The internal fans at the wing root also ran permanently. We had about 6 cheap digital fish tank thermometers spread around the interior of the oven and also a smoke alarm. The temperature distribution was quite good. We kept it at just under 55degC for about 36 hours. After cure we noticed slight impressions of the spar cap in the shell on the inboard upper surface. This will add to the work before painting !

April-09


The wing tips were cut off in preparation for the aileron fitting. The gluing looked good inside and all looks good for making the tip connection. The aileron hinge plates were final fitted and glued in place in the wing with the ailerons in situ. The glue for the hinge plates was constrained by foam rubber inside the wing and by shaped plastic pieces on the rear web. Then some glue and tape was applied to the hinge plates to stiffen and strengthen the mounting.

The aileron gap was set by sanding and checked with rotation. The aileron horn, horn clamp and con rod was made. The horn clamp is glued into the aileron just behind the horn hinge pin mount, where the aileron has a recess, extra laminates and a fill of glue as a core. The clamp has a buffer of glass and glue to the carbon. Clearances were checked for the moving parts and the shape of the exit hole in the wing shell was refined a bit. The fairing will have to come later. It will be slightly wider than normal due to the wing sweep.

The available space and moment arms for the aileron mass balance was checked with pastolin and we are struggling to have enough space. Originally the flutter models had a full mass balance along the aileron LE nipple. So we will rerun the flutter prediction process to look at partially mass balanced and also point mass options. Or try depleted uranium?

Jan-09 to March-09
Gregg took some rest so the project didn't make much progress in the workshop.

Dec-08

A static load test was done for one of the hinge plates. A conservative approximation was needed on the stiffness of the hinge mount. Some pieces of wood were used to allow some simulated deflection of the mount. The failure load was higher than we thought, about 840MPa. This was just to reassure ourselves about the strength of this tiny part. The stiffness and glue area issues are more critical.

Dec-08

The carbon hinge plates for the aileron were made. After a very thin glass liner the lay-up has some carbon UD wrapped around the mandrel in a spiral, intended to give better roundness in the bore, better release and a stronger part. But this idea does use up some of the available space for the hinge plate, and the space is small for the hinges near the tip. A little grinding inside the hinge space was required for hinge 6 and 7 clearances.

A squash plate was pressed on with spring clamps to compact the layers and create the fillet shape The hinge plate lay-ups went into the oven fairly early and the parts were very easy to demold. The test part without the carbon spiral wind was definitely harder to remold.

The individual hinge plates were sliced off the stock The ones inboard on the aileron are for 6mm pins and are a bit heavier. The one at the horn location is also wider. The hinge plates outboard of the horn are for 5mm pins and are built a bit lighter. After being debured a DU type bush was pressed in each. These are clones of the Glacier Garlock bushes, A split bush with a steel back, sintered bronze liner impregnated with teflon. The pin fit was good and quite consistent.

Dec-08

The aileron cutout in the wing was trimmed and the first aileron trial fitting was done. Initial checks on the fit of the carbon fiber hinge plates were made. They have to fit neatly into holes under the rear spar during the gluing. On the ailerons each hinge area had a notch cut at the front to allow clearance for the hinge plate during rotation.

Nov-08

The hinge jig was used to drill a hole into each hinge form for the pins. Then the pins were fitted into the holes again with the jig and a small amount of glue used to fix them. Then the jig was removed and the glue applied around the exposed pin to form it's mount. Cardboard dams were used for this, the aileron being placed vertical and a ladder used to reach the hinges.

For closing the aileron shells cardboard strips were used to control the glue at the front flange or nipple. We also tried this at the sides of the hinge shapes, where the glue wants to run off the top too easily. The shell closing went well and the amount of glue was well controlled. The hinge pins looked good with almost no glue seepage from inside the shells. The remolded aileron was about 1600g then about 1380g trimmed. The mass balance may weigh as much as this.

Nov-08

The upper aileron shells were laid up. Then the lower shells were prepared with styrofoam forms at each hinge. The shell laminate was wet cut around the forms, with a patch over the form area done in the same lay-up. This was to give the best overall drape, fiber orientation, stiffness distribution. The hinge at the control horn (hinge 3) has a little extra reinforcement and there is a form used to allow the steel fitting that bolts the control horn on.

Nov-08

The work on the ailerons begins with some cleaning, repair and grinding of the gel coat.. For the hinge pin alignment our concept is to make an alignment jig referred to the mould surface with contact points on the mould flanges. One jig does both ailerons. Small plastic collars sitting in the moulds set the hinge location. The aluminum jig can allow a curved splined line between the hinge points, but our axis was in the end quite straight. The hinge pins we cut from ejector pin stock and the metal sleeves in the jig we cut from ejector sleeve stock, so the fit was very good. Wooden struts in the jig set the height and position relative to the mould flanges. The jig will be used for drilling the holes for the pins in the hinge forms, then for holding the pins while they are glued in.

Nov-08

The rear shear fitting for the wing root was made from 4130, welded by Nicholas at NC Welding Services and plated. For this prototype the fitting is being set reasonably accurately to the wing and then the glued in carrythrough bearings in the fuselage are set to that.

Oct-08

The first rigging of the glider wings in the paddock by the barn. Was fairly easy with two people and one sawhorse for a wing stand.
With proper supports, one man rigging shold be possible.

Sept-early Oct-08


A drilling fixture was made for the front of the spar bridge box. This allows an orthogonal pilot hole, with some checking and adjustments at the rear wall. After the drilling of pilot holes the big holes were quite easy, done one at a time with a hole saw.. To check hole alignment a 1mm cardboard spacer was put over each bush, the bushes inserted, the wing assembled and the main wing pins were fitted. So the minimum glue gap was good (mean glue gap 1.3mm at that stage). The spar bridge box (bulkhead) bushes were glued in first, then the gluing for each wing was done separately. Some turned plastic parts made the insertion of the bushes easy. A little glue got onto the pins but they broke out by hand with very little force.

Sep-08

The outer shear wrap on each wing spar was laid up, an almost continuous layer of glass, with as close to 45 deg orientation as possible. Then we were ready to work on the wing connection fittings.

The front shear pins will be done first, then the main wing pins, then the rear shear fitting. The front shear pin looks like a common type which takes all the loads between wing and fuse on a normal glider, but on SG-1 this fitting just takes the shear force Qx and some of the wing torsion Mt, so has relatively low loads.

For the front pins we made a drilling and alignment block that fits the wing roots and the fuselage. Wooden bearing blocks were laminated into the wing root LE and the hollow stainless steel shear pin was set into that. A brass bush was set in the carbon bearing block on the fuselage side and cured with the wing properly aligned. A wooden spacer was also made to shift the rear shear fitting closer to the fuselage.

Sep-08

A cradle for the fuselage was made using wood and carpet scraps. This will allow the fuselage to be fixed while the wings are fitted. The wing was approximately fitted and the dihedral and sweep checked. The clearances in the spar bridge box and the errors in the wing to fuselage joint were measured. After a final check of the minimum glue area calculations for the root rib an offset line scribed onto the wing root set the desired edge for trimming.

Archive 5
Fuselage ergonomics mockup.
Cockpit bulkheads and front wheel box. Seat pan and seat back fabricate.
Fabricate main gear, peddal assembly, sliding pushrods, connecting rods, control column, wing main bolts and bushes.
Control column mountings, pushrod and linear bearing mountings. Fit main gear and cockpit controls.

Archive 4
Wing root ribs fit, wing internal hardware build and fit. Brake box.
Close wing shells.
Fuselage control hardware mockup. Build and fit. Close fuselage shells.

Archive 3
Wing spar web tape join, root rib forms, moulds.
Fuselage / fin shell layups.
Main bulkheads for fuselage. Forms / moulds, parts, glueing, bearing areas. Fin spar web.

Archive 2
Wing shell, wing spar bridge, web gluing flanges, aileron spar, brake box forms.
Controll surface moulds, tail plane plug.
Canopy sill mould process.

Archive 1
The wing and fuselage plugs, moulds.
Test wing section, spar bridge moulds.
Test spar.