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  1. #351
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    My Hawk is well on the way, and all has been well so far, so far !

    Yesterday I glued in the flap hinges and set everything up EXACTLY as per the settings on the CD. The lower surface of the flaps are exactly flush with the lower surface of the wing. This morning, Hysol set, I see that on the left wing the upper surface of the flap is exactly in line with the upper surface of the wing, however on the right wing the upper surface of the flap is about 2mm HIGHER than the upper wing surface. I can also see that the tip section of the flap is rather different to the root section of the aileron, (the flap section rises at greater angle from the lower surface.).

    Considering this over morning coffee the only real solution I can see here is to make a new flap from thin ply etc to the exact section , (it is a fairly simple structure) as I want this model to be as perfect as possible and the flaps on both of my Airworld Hawks, both with flap vanes, fit almost perfectly.

    Has anyone else discovered this problem or have any advice ?

    Regards, David Gladwin.

    PS I notice on the photo CD that there is a similar misalignment on one of the pictures on one of the factory models.

  2. #352
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    David,

    I will take a look at the wings when I get a chance, they are packed away at the moment, so will let you know.

    Progress now as all the making is starting to fit togthter. Added the smoke injector to the bypass, making a small bracket to hold it in the correct place.

    The strobe navigation lights are supplied as kits and even the small LED's are supplied separate to the PCB's on which they have to be soldered (the correct way round!). Got a friend with a good eye and access to decent soldering equipment to oblige, next came mounting the assemblies.
    The two strobes are supplied as vac formed lenses, I cut these almost down to the edge, but left a small lip, then I cut two small pieces of FR4 into shapes that would fit into the base of the covers, then cut two holes to allow the PCB's to slot into so the LED's would be flush to the base of the plate. Two thin strips of FR4 had a hole cut into them to allow the LED dome to slot through, the thin plates were cyano's to the main plates and sanded to shape. These were sprayed silver.
    I dropped the finished plates into the covers so they seated nicely, a small lip was left all round as a result of trimming the lens almost flush, this allowed a bead of 5 min Methacrylate to be run around this lip securing the plate inside the lens.
    Once dry I put a small piece of masking tape over the LED hole to prevent sanding dust entering the light enclosure, placed the unit on a piece of sanding paper flush on a bench and slowly removed the lip until the edges were flush with the FR plate.
    I glued in the LED's into the recess left.
    In the correct position on the fuselage two small holes to match the LED PCB's were made and the units were glued in place. I have yet to do the top beacon as the lens requires colouring red, a friend has some so will spray first and then assemble.

    With the rear belly white strobe in I was able to fit the bypass/pipe.

    After the canopy hinge struggle of last week the canopy 'glass' is now bonded in all round, I have still to do the outer frame but this will be done a little later. Added a wire canopy stay at the rear, using an assortment of brass threaded inserts and clevises, the wire folds into the space behind when the canopy is closed.

    marcs

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  3. #353
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    For those interested I have one glass board set left from the original 6 made for anyone who wants to upgrade the plastic units supplied. (the 4 antenna groups are also included but were not shown in photo)
    I also have one set of the canopy latch closure parts available.

    PM me if interested in either and I can let you know the cost.

    marcs

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  4. #354
    Ali's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    I will take that from you Marc, as it seems as if I have just ended up with another hawk
    Al's Hobbies, Horizon Hobby, Airworld, BVM, Jet Cat, Skymaster, Rc Jet Centre,pull over, Tomahawk, C-ARF, Jet-Teng,Kingtech

  5. #355

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    RE: Skygate Hawk - build (virtual manual)

    Ali,

    What's the latest word on the inlet package final preparation? I've got a gutted fuse just waiting to get started with the new install.

    David S

  6. #356
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    David,

    Updated Ali earlier today, just the bypass's to do so hope to have ready for shipping later this week.

    marcs

  7. #357
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    Pressure tested the air system as it is so far, just so as not to get any unexpected leaks in areas which are more tricky to get to, all well at 160psi.
    Added the two pressure gauges in the fuselage by the view windows so the air pressure can be seen from the jet as a spot check.

    Secured the rear tail pipe with the clamp type holder.

    Started to assemble the cockpit tub. This is fibreglass and has a channel moulded into each side panel to accept the floor sections which are in two pieces. As the edges are thin I decided to add some wooden blocks at the fixing points to give a good fixing base for the securing screws.

    As a separate job the bypass carbon mouldings are now underway for the bypass kit for this jet, the first is shown in the vac process where we are using a rather neat very flexible piece of silicone sheet to act as the vac bag, this conforms to the bypass shape nicely and as a result will not leave lines on the outer case which is often the problem with normal vacuum bags.

    marcs

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  8. #358
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    More work installing the parts, checked over the main door cylinder links to the doors, everything looks to fit fine although rather anoyingly one of the cylinders had a longer throw than the other so had to tweak the threads on the end to get the same throws - why does this happen!
    Ducts seem happy and out of the way of the main stuff, it has always been a worry of mine in making these mods that something major crops up at the later stages, fingers crossed it seems to be working out fine at the moment. The first complete bypass/tank kits is are ready now so Ali will be able to ship them to the eager customers....

    marcs

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  9. #359
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    After 10 days of non-stop work my Hawk is almost on its wheels. Much of this kit is exquisite, some not so good :

    The badly fitting right flap/wing combo has been tracked down to the fact that the rear upper surface of the right wing is cambered and should be flat, as it is on the left wing, this camber takes the upper wing skin below the flap upper surface by just over 2mm, looks awful. Several options were considered including putting flat stiffeners under the rear surface but this had knock on effects to the aileron, the section of which does not match the flap. My final solution, still a compromise, was to build a new flap, with a section 2.5 mm thinner than the original flap. This matches the aileron and is exactly correct at the flap/aileron junction but the lower flap surface is a little above the lower wing surface at the root !

    The bolts supplied for the fuselage joining and stab mounting were all 6 mm too short, very frustrating (and time wasting) !

    The canopy is done, in one piece, a LOT of work but the results are great ! The canopy frame is 2.5 mm too narrow at both sides, strips of balsa were used as a filler. However :

    I have said it before but there is something not quite right about the SkyGate Hawk canopy, think I've found the problem. On the real Hawk the canopy sill is 8.8 cm deep. At 1/4 scale the model should be 2.2cm , in the kit it is about 2.7 cm, trimmed to 2.2 cm it looks MUCH better. Similarly the canopy arch is 60 % of the sill depth on the real jet, say 5.3 cm, 2.1 inches. at 1/4 scale the model arch should be 1.3 cm, the kit is about 1.6 giving a total canopy arch width of 3.2 cm instead of 2.6 . Mine are all trimmed to the correct size and the canopy/windscreen looks MUCH better, exact scale !

    The other thing about the SG Hawk is that long dangling landing gear, doesn't look quite right. I think the problem here is that, unloaded, the gear extend a little too far. I have some BAe drawings so I'll investigate further when installing the gear, beautifully made.

    Marc/Ali. I'll be ready for the ducting by the weekend !

    Regards, David

  10. #360
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    David,

    Can you post some pictures of the canopy work, it would be of interest to many I am sure taking the scale route... did you use the side hinging system as per scale?

    marcs

  11. #361
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    The main cockpit instal is now underway, as the catch system being used utilises width along the opening side of the fuselage side, and the scale D4S hinge system takes width up on the other side the cockpit tube ends up being slightly narrower than the original was intended.
    First job was to find a suitable method to attach the two side panels, eventually velcro was opted for as the length over which is was going to be applied would be plenty for a good fixture, but would allow flexibility for the fit. On the side where the scale hinges were I scuffed the area along the entire length of the fuselage side and glued a thin strip of aluminium along the length resting on top of each of the hinges - this gave a flat surface for the velcro loop to be stuck to and stiffened the fuselage side - I omitted the long heavy carbon strip supplied in the kit as the base of the canopy frame had already had a new strengthener fitted.

    On the side with the sliding canopy catch I fitted the velcro strip under the slider and trimmed the edge of the cockpit side to allow for the lower location. In the process of removing the 12mm or so of cockpit moulding the carbon tow stengthening had to be removed, so I added a thin strip of carbon flat lower down to reinforce the panel after setting the velcro strip in place.

    The resulting change of width requires the base panels to be made narrower, fortunately the seat bases still fit nicely so removing 2.5mm from each edge was not a potential problem.

    The front instrument binnacle looking at images from the supplied build CD looks to be glued in place, its quite a tricky fit but I felt having it removable would make access to the nose gear section easier. I achieved this by adding a lite ply plate to the inside of the front flat face of the instrument cover, then added two strengtheners to this and drilled 4mm holes through each point. I made two 2mm hole towards the rear of the cover in locations which allow fixing screws to locate into the front shield frame near the edges - I added two small washers to the cover to strengthen the areas where the 2mm holes were drilled.

    I slid the cover in, lined it up and drilled through the 2mm holes into the two front shield frame points. I removed the cover and opened out the 2mm holes to 2.5mm to allow servo screws to fit nicely. I added a piece of masking tape to the inside surface of the front shield moulding, then re-installed the cover screwing it into place using the rearward fixing holes, when lined up I slid a suitable pointed rod through the holes made in the cover front face and pushed them so they marked the masking tape on the moulding. On removal the two marks made on the masking tape were drilled out to suit the two 4mm rods I planned on using to locate the front of the completed unit. Finally I re-mounted the cover and secured it with the rear two screws, then slid the sanded carbon rods through the cover and into the location holes - tacked them once in the correct place with cyano. When removed I added more glue to secure the rods.

    The instrument binnacle sits in a location just forward of the last instruments on the side panels, so this position was marked on the cover, the location was transferred to the inside of cover and the area scuffed. I applied some matt paint to the inside of the cover forward of the instrument panel to finish off the look. I tacked the instrument panel to the cover 3/4 of the way round as the edges were not a good fit and extended the matt black paint back to disguise the gap. This also works to allow the sides to flex when fitting so probably a good overall result!
    I added a small support behind the instrument panel to prevent the flexing breaking the bond, used methacrylate to bond all surfaces.

    Next is the rear instrument pod.....

    marcs

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  12. #362

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    RE: Skygate Hawk - build (virtual manual)

    I just received Marc's FR-4 package for the Hawk. AWESOME!

    Thanks Marc, for making your workmanship available to the rest of us, and at such a reasonable cost!

    David S

  13. #363
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    Your welcome David.

    marcs

  14. #364
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    My Hawk is almost complete structurally. Another issue:

    If the stab pivots are mounted as seen in post 124, which I think is correct, according to the photo CD, the stab. pivot point is way aft of the actual pivot point of the real Hawk as marked on the fuselage of the model. Mounted this way the cutaways on the fuelage exactly match the stab beam allowing the stab to move over its whole travel.

    Now , if we reverse the stab pivot assemblies it brings the model's stab pivot point almost exactly to the real machine's stab pivot point, making it possible to accurately model the stab cover plates.

    Moving the stab pivot point will affect the aerodynamic and static balance (it will be less balanced with a forward pivot point.)

    Anyone care to comment?

    Marc, not sure about the opening canopy and I will post a shot of the revised canopy frames when I take the protection off.

    Regards, David Gladwin.

    PS Some quick measurements show that moving the pivot point forward would mean that there is only 15 % of the stab area FORWARD of the pivot.

    On my FC Mig 29 which has a forward pivot point there is almost 25% of thge area forward of the pivot axis.

    Most flying stabs have the pivot point fairly well aft of both of these values.

    I wonder if I moved it forward a couple of JR 6031 servos, 35 kg/cm of torque, would solve any and all problems of balance ?

  15. #365
    BaldEagel's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    David

    There has been a lot of discussion on stab pivot points on the "JL buyers beware" thread would it be OK if I copied you post over to it?

    MIke
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  16. #366
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    By all means Mike.

    I have read the thread and really nothing new in it. Problem is that with scale models of jets the pivot point of the stab is also calculated on the fullsize to cope with the effect of Mach No. when supersonic (C of P moving aft) so, in general, for model use at subsonic speeds the pivot is too far aft.

    On the real Hawk it is relatively forward (stable) as the machine is only just supersonic AND has 4000 psi hydraulics to cope with the loads.

    So far as I can see moving the pivot point forward on my model Hawk will be safe in that it is anti flutter BUT will require more servo torque (no problem there with twin 8711s or 6301s) to overcome aerodynamic loads when deflected.

    The question is: why did Skygate move it further aft than scale, unless to reduce the loads on the servos ?

    A quick look at my AirWorld Hawks shows that the stab pivot point is about scale (although higher than the real Hawk ). I will measure it more accurately tomorrow, so a more forward point on the Skygate SHOULD be no problem if servo torque is increased proportionately.

    That said, I would welcome any knowledgeable comment on this issue.

    Regards,

    David Gladwin.

  17. #367
    BaldEagel's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    Thanks David.

    Just one thing, you are showing your age, I have been pulled over the coals for using C of P it seems now days its refered to as C of Lift??? why did it change, no idea, I suppose so some one could pick on the old guys. LOL

    Mike
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  18. #368
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    More info for those interested.

    C of P (pressure) is still widely used, didn't know it had changed !

    Just ask the newbies what force a stab at high negative angles of attack is generating, the pressure is NOT lift, just the opposite ! Nor is the force generated by a rudder as the C of P moves with deflection !

    Back to the Hawk. The real Hawk has the stab pivot mounted at 42 % of the root chord giving about 18 % of area forward of the pivot so no overbalance. With the original mount location shown on the SG Hawk the pivot is mounted at 48% root chord, reverse the mount and, magic, 42 % of root chord, meaning simply you have to recontour the cutouts for the stab "bridge" to put the stab pivot in the scale position AND allows accurate, scale, cover plates and tracks.

    On the AW Hawk, the stab pivot is at 43 % of root chord and with twin 8711s it is not short of power and the Weatronics data shows no high current drain when the stab is deflected to near max at landing. Large angles are not used at high speed. No drama there. I have not heard of any stab. problems with the AW Hawk but it is essential with the servo setup to EXACTLY match the servos to prevent them working against each other.

    The SG Hawk is 10%, linearly, bigger than the AW meaning the stab has 21 % more area. If we give the stab servos 21 % more torque we have the same torque/area ratio so all should be well, so twin 6301 servos should be MORE than adequate.

    That said, my GUESS is that twin 8711s should be more than adequate as when the angle of deflection increases the C of P (sorry Mike) will move forward easing the aerodynamic load.

    So I am going to reverse the stab mounts, decision made !

    I made some measurements on geometry of stabs. of some other scale jets in my stable, for info they are:

    BVM F4 25 % of area ahead of pivot.
    BVM F16 22 %
    Avonds F15 25 %
    FC Mig 29 24 %

    The first 3 all have lead forward of the pivot to improve mass, static, balance.

    SkyGate and AW (and BAe) Hawk, pivot forward 18%. The SG Hawk has added mass in the stab LE.

    Any comment would be appreciated, perhaps Olnico could use this as a "test case" in his forthcoming article on stabs.

    Regards, David.

    PS Marc, I am ready for you ducting !

  19. #369
    marc s's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    Interesting stuff guys, this is an area where I really do need to study more.
    David, complete ducting sets are with Ali and ready to go - hope you like the results.

    marcs

  20. #370
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    I have now reversed the mounts and it all works, just a little change to the cutout for the stab. bridge and all is fine. The reversed mount gives the pivot point at 41.5 % of the root chord (Close enough to scale !) and brings the pivot point to just about 2.5 mm forward of the scale pivot point engraved on the fuselage which will allow scale cover plates and tracks with just the merest tad of a change from scale to the arcs described by the plates.

    Twin 6301s ordered. giving the whole stab. 70 kg/cm of torque.

    In addition I will beef up the servo mount which will be of 1.5 mm glass board VERY securely fixed to the fuselage.

    Regards,

    David G.

  21. #371
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    RE: Skygate Hawk - build (virtual manual)

    David,
    I sure wish you could post some pics so I could better understand what it is you are talking about.
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  22. #372
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    Right, the first shot shows the flap surface ABOVE the wing surface. The new flap was made so that the upper surfaces are continuous.

    The second shot shows the canopy sill and arches trimmed to the correct size, dimensions as per my earlier post. The gap from my bad cut has been filled and the canopy and windscreen arches have been faced with 10 th glass sheet to produce a perfect fit.

    The third shot shows that wing fences for RAF Hawk T1 need to be reprofiled (and the vortex generators moved forward of the engraved position by 1 cm (BAe drawings and photos confirm ).

    The fourth shot shows the original position of the stab pivot. Note that the pivot point is offset from center of the mount.

    The fifth shot shows the new orientation with the pivots reversed bringing the pivot point forward as the stab must remain in the same position, ie TE of stab. ie 3mm forward of the aft face of the tailbox (may not apply on Swiss Hawks etc which had tail chute)

    The sixth shot shows the correct scale pivot point, black circle, the new model pivot as a black vertical line (less than 3mm apart) and the arcs show the arcs which will be described by the pivot covers. The solid black lines are the scale arcs which will now work, the dotted line are the arcs which would be needd if the stab was fitted with the pivot in the original non scale position, ie pivot aft of scale.

    Regards,

    David.

    PS Some of you may recall that quite a number of builders of the original SkyMaster Hawk had problem with lack of pitch authority, causing some models to crash, as discussed on RCU some years ago. After considering the pivot point on these Hawks in detail I think I can see that with a forward scale pivot point they were simply not using enough servo power. I had NO problems when using twin 8511s and the model was a pure delight to fly. And I still remember the issue of the elevator and rudder servo specs on the original BVM Bobcat were simply too small, marginal at best. I put stronger servos (JR9411s) in mine, never had a moments trouble and they are still flying beautifully after 100s of flights , best sport model ever, and EVERY part in those kits fitted perfectly.
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  23. #373

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    RE: Skygate Hawk - build (virtual manual)

    Hello David,

    Thanks for the info.
    For my Tommy-Hawk, I've received some pictures of the Swiss MK66 and the stabilizer hinge line is located 570 mm from its leading edge (fuselage side).
    As far as I know, this is the same as for the MK T1 and T1A. As the Skygate hawk scale is 1:37548 (if remember correctly), this means 151.8 mm on the model and looks right as the new black line on your picture no. 6, see attached photo.
    For the Tommy-Hawk (scale 1:3,5) this would amount to 162.9 mm and it looks like your method of reversing the mounts would solve this perfectly.
    Reason givven by one of the builders is that the combination of the then used pushrod, thrust tube and servo capabilities has led them to this decision.
    In the past the have used lead in the stabs leading edge, but it required 3-4 times that amount in the nose to compensate for this.

    Do you have a detailed BAE drawing of the fences?

    Regards,

    Remco45
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  24. #374
    David Gladwin's Avatar
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    RE: Skygate Hawk - build (virtual manual)

    I just checked the dimensions, and I make the scale (K) 1: 3.7348 recurring !

    That makes the scale canopy sill height 8.7cm /k which is 2.3 cm,, mine is exactly that. Similarly the canopy and windscreen arches are a total of 101mm, 4inches if I rember correctly, certainly looks right, divided by k means they should be 2.65 cm. What you see in the photo is exactly that.

    Glad to help on the stab issue, I think it will be fine with all the torque I am going to put in and the strong, steel pushrod with supports to prevent bending.

    I dont have any BAe drawings of the side view of the fences, just the wing in planform. I measured them on a Hawk at Scampton, then made exactly scale fences for my Airworld Hawks and I have enlarged and modified them for the SG as shown.

    Any ideas how to exactly replicate tho rivet heads as on the rear fuselage area, pin heads are just a tad small.

    Regards,

    David G

  25. #375

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    RE: Skygate Hawk - build (virtual manual)

    David,

    On the pictures i've received of the Mk 66, the most common rivets are 5, 6 and 7 mm with a height of approximately 2, 2.3 and 2.8 mm.

    I just know of one trick and that is sanding the surface very lightly with very fine sandpaper (grit 3000 or so) and placing drops of white wood glue on them using a fine syringe.
    This takes some practice though to get consistent size drops.

    Regards,

    Remco


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