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98" Depron C-130 Hercules Scratchbuild


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Good evening,
Mark, thank you. I wouldn't mind betting youve almost finished your Vulcan by now wink

Hi again SImon, - thanks . We stock Depron in the shop and when it's ordered from the suppliers, the 700x1000 sheets (grey or white) are of the heavier variety and the larger grey 1280x1000 sheets are the softer, lighter grey depron. When I refer to 'grey', I mean the lighter 'Aero' quality as you call it. You're absolutely correct, it is about 20% lighter but I struggle with it a bit in that not having a skin' like the standard Depron, I've only got to touch it with any abrasive paper and it irritates my lungs.I have mentioned this before in earlier blogs about the lighter grey depron seeming to cause more dust. Again, I agree, white does seem to cover better too when it comes to painting. More so with this build in that the aircraft is white!.
Cheers cymaz!

Stu, when I first started looking into the possibility of building the Herc', I did look at some plans but on closer scrutiny, found them to be way off scale in most areas. Useful though for sparking off the thought process. So, I resorted back to the good old 3 views of which there are many on the 'net. One problem I did encounter though was through using more than one 3 view, I caused myself problems when I was creating the drawings because I was referring to two different variants of Hercules.

John, how very sad observant!
You're correct. I do tend to remove my best watch when I'm creating dust. So, the black one is the 'Tonka' work watch and the stainless one is my favourite.

img_1592.jpg

Got a bit done today on the nacelles. By a bit, I mean ' a bit'!
This part of the model has to be one of the difficult bits to date and I've got to make 4 of the blighters. The two inner nacelles sit perfectly flat on the level centre-section of wing. The port and starboard outers are hanging from a wing that has dihedral. Serious amount of head-scratching......
I am cutting 6mm horizontal slots into each foam block that makes up each nacelle. This way, they can slide onto the depron wing plate as a starting point for ensuring correct alignment. The 6mm slot in the outer nacelles had to be cut 2 degrees off horizontal to ensure they hang at 90 degrees from the wing. img_1588.jpg
The foam nacelle blocks in situ

img_1589.jpgimg_1590.jpg

The motor mounts I made yesterday have a 16mm plastic tube which will push in here. 15mm brass tube cuts a nice neat hole effortlessly into the pink foam,

img_1591.jpg
About 4 hours later, they're starting to take shape.

I cut some 15mm diameter holes into the foam blocks (Brass tubing with a serrated edge) to take the 16mm tubes on the motor mounts. With the motor mounts pushed in place in the foam, I had a good reference point to sand to and so set to with sanding block. Took a while and although not finished, are looking quite good.

Hoping to start introducing the wing ribs to the wing plates tomorrow.....wifey might have other ideas...
For now
Regards

Roy

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Saturday 19th July
Hi again,
Terry, welcome - thank you.
As I mentioned previously, I could now start to introduce the wing ribs onto the wing plates. Each rib had to be notched out to accommodate the piece of 6mm depron strip that covers the carbon tube but no big deal. Again, I used PU glue to secure the ribs. Wing ribs 3 and 4 sit each side of the outer nacelles and so I fitted them with the nacelle pushed in place. Not yet glued, the foam nacelles would be sorted later. Care was taken to ensure that each half rib (upper and lower) was fitted directly above each other and alignment checked on each. It didn't take too long before all ribs were pinned in place waiting for the glue to cure. In fact, I left them overnight and removed the pins the next day.
As you're aware, I have built a 6m carbon tube into each wing plate and similarly to the Spitfire build previously, intend to 'trap' the carbon tubes in a box section along the centre part of the wing which would be part of the dihedral brace.
The dihedral brace was made up of 2mm plywood running full length across the wing centre section and kicking up on each end into the wing up to the location of the outer nacelles. 2 were made and I measured and cut a piece of dense blue foam to fit between the 2 ply braces. Once glued between the ply, made for a strong yet light 40mm square box section that would also sit aside and support the carbon fibre wing tubes.
img_1594.jpg
The 2mm ply wing braces before the blue foam was sandwiched between.img_1595.jpg
The 6mm carbon fibre wing tubes now nestle in a blue foam seat between the ply wing joiners.

img_1598.jpg
The view from the underside of the wing.
img_1597.jpg
Alignment checked before glueing on the outer wing panels

img_1599.jpg
Finally, before filling the blue foam (Above the carbon wing joiner) with PU, I measured and cut a section of 5mm balsa sheet to cap off the box section. Once the glue was drizzled onto the carbon tubes, the balsa top was pinned in place before any expansion of the glue took place. Result - 1 very rigid , light box section that captures the carbon tubes and adds lateral strength across the wing.

 

As the outer wing sections were curing, I checked the dihedral angle and ensured that I achieved the desired amount of dihedral. (44mm rise from root to wing tip). Pleased to say that once everything had dried, the wing looks level, without warp and to say requires skinning, is remarkably rigid.
Needless to say, a pretty important photograph had to be taken. I held the wing in place whilst the good lady took the photo and img_1606.jpgimg_1607.jpgthen had it stand on its wheels for the last picture.

I'm quite chuffed with the results so far.
That's about it for the moment but I'm sure it wont be long before I update you again soon,
Regards

Roy

 

Having just read this log update through, I forgot to mention that I have cut some airfoil sections, the same size as the wing ribs in the centre section from dense foam, 2 of which I've used at the joint point of the outer and mid wing section. I will be adding more dense foam 'ribs' to the mid section of the wing  to beef up this area which sits into the wing seat on the fuselage.
Edited By Electriflier on 19/07/2014 21:06:06

Edited By Electriflier on 19/07/2014 21:27:20

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Cheers guys,
Too hot to work indoors, too hot for me to work outside. Being folically challenged, the vinyl roof gets burned quite quickly if you know what I mean. 'Wear a hat!'. Yes I always do but it's been so hot that it's been unbearable wearing a hat. 'Mad dogs and Englishmen'....... not me I'm afraid, fair skinned and all that.
Anyhow, little odds and sods have been done over the past couple of days like drilling out the motor mounts and fitting 3mm captive nuts etc. Motors have now been securely bolted and thread-locked.
img_1612.jpg
The elevator and rudder servos have been fitted into the rear of the model. The elevator servos (one each side) are fastened in using the servo covers that I use on most of my builds.img_1613.jpg The rudder servo is sunk into a laminated depron section of the keel through a plywood facia mount.img_1618.jpg

I have made the rudder 'torque' rod controlled rather than the normal control horn, It's just that I didn't want to see the actuating arm and control rod whilst the model was on the floor. So, the torque rod passes through the rear of the fuselage and will link to the servo underneath the back end of the model.
The rudder has been skinned with 3mm depron since I fitted the torque rod and using cyano hinges, was glued in place. Obviously, to allow the torque rod through when fitting the rudder, I had to remove a slither of depron from the fuelage which was replaced once the rudder was in place, img_1619.jpg

The rest of today (well this afternoon after it cooled a little) was spent applying 3mm depron skin to the back end of the fuselage which is now almost complete.
Until next time.....
Regards
Roy

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Hi again,
Roy, as ever, thank you and John, thanks for the invite. I might just take you up on that

A major part of any build to me is when you're ready to give the model a little colour. OK, I'm building in white depron and the model is predominantly white but it's amazing just how nice a few coats of white makes. I used acrylic undercoat as a starting point. 3 coats in fact with a light rub down between coats. (the aircraft that is).
The orangey-red colour that flashes through the US Coastguard version of the C130 was a little more difficult to source however. Good ol' B&Q to the rescue once more and their Valspar range of emulsion paints. I spent quite a while deliberating over which shade of red/orange was closest to the photo I had of the actual aircraft and once I was happy with the colour swatch, asked the assistant to make me up a tester pot. The tester pot is 250ml and cost around £2.40 (can't remember exact amount). Great value for money and you get the exact colour you require and enough to complete the whole model - result!
The white undercoat was given one last rub down until a lovely smooth finish was achieved and then 'frog' tape (no bleed) masking tape applied to the nose and tail sections.upd1.jpg
A couple of coats later and the tape was removed to reveal this.......upd13pg.jpg

upd12jpg.jpg
Well chuffed!!!

Time now to spend some time on the wing. I decided that the best probable location for the quad ESC was atop the centre leading edge section of the wing. If i was careful, I could create a 'seat' in the dense blue foam that would allow airflow around the ESC once I get around to skinning (more on this to follow).
So, the ESC was sited here and now I could take measurements for the endless lengths of silicone wire that will be required to feed the motors..upd14pg.jpg
I know there are arguments for and against lengthening the wires to the motors but I really have no choice now I'm using this single quad ESC.
upd14pg.jpg

The motors and their mounts could now be glued into place on the wing. Before doing this however, I glued 4 x 6" lengths of hardwood dowel into the foam nacelles.upd16pg.jpg
With these dowels glued in at their base only, it allowed the plastic tubes that are to the rear of my motor mounts to slide onto the dowels thus adding further strength across the length of the nacelles. Once PU glued into place, would be extremely strong and offer great support for the outrunners. One thing I did have to be careful of at this stage though was keeping the captive nuts free of the expanding PU adhesive. Blu-tack came in handy here. A little stuffed into each exposed hole at the rear of the motor mounts ensured they stayed clear of glue.upd15pg.jpg

Anyhow, without boring you with fine detail, stood the wing on it's trailing edge with the nacelles pointing upward and flooded each dowelled hole with PU before sliding on each motor mount. Once they were on, pinned them down to stop the expanding glue pushing them back out. The Blu-tack did it's job! The motors were then bolted back onto the wing and this photo opportunity arose...
upd17pg.jpg

upd18pg.jpg

upd19pg.jpg
So, the end of another day. A little more progress and still enjoying every minute !
Regards
Roy

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Mark, Tony, thank you gentlemen.
Saturday 26th July
Busy day in the shop today but with the help of Charles, was able to get the extension leads to the motors made up - Thank you Charles!
Whlst things were a little quieter this morning, I drew up some shapes for the cockpit windows and fed them through the Roland vinyl cutter.upld1.jpg Cut from black gloss vinyl, reflect light well and look quite good against the stark white fuselage. Also, painted the nose with black satin finish acrylic. upld2.jpg

12 leads of 18SWG silicone wire were soldered up with 3.5mm gold plugs and sockets which enabled me to hard wire the motors to the ESC for the first time.
Once they were routed, the temptation to go for a test 'spin-up' was too great. 9x5 2 bladed prop's were used for the test as I knew they were safe to use with a 4S lipo from earlier tests. The earlier tests showed each motor individually produced around 340W of power with a constant 25-6 A draw.
To be safe, I promised myself that I would simply spool the motors to check their direction of travel. OK, 3 out of 4 wasn't too bad. Only one motor required its wires swapping. At the moment, I'm happy to run all 4 motors in the same direction of rotation. I have yet to decide about the merits of 2 x CW and 2 x CCW prop's. - No rush just yet!upld3.jpg
With the wing seated on the fuselage, Charles held the wing, ESC and Wattmeter in place whilst I connected up the battery. The 4 ESC sang out in unison. Encouraged by the total lack of vibration, opened the throttle gently. The sound was AMAZING!!.
1150 Watts of cummulative power from 4 very sweet -sounding brushless motors. At well under half-throttle, the Herc' moved effortlessly under it's own steam for the first time.upld4.jpg
I have added a further 6mm depron spar to the wings (Just in line with the leading edge of the aileron) to lessen the possible tendency for the wing to twist under the torsional effect of the outer motor. It has made quite a substantial difference to the stiffness of the wing.
upld6.jpg
For now, that's about me up to date.....
Regards

Roy

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"I have yet to decide about the merits of 2 x CW and 2 x CCW prop's."

My somewhat smaller one flew on four brushed 400's with Gunther props all going in the same direction. There was no torque reaction or effect that I could notice. Going from cruise power to full power showed no noticeable change in attitude except for a climb, which was usually what was intended in that part of the flight pattern anyway.

As you say, the sound on yours is awesome. Can't wait to see it fly. What a super piece of work!

Just for inerest, could you put the two pairs of motors (port and starboard) on separate channels mixed together for full control, then mix with a bit of rudder so that you could get asymetric thrust for assistance in ground handling? Or is that a step too far!!

Edited By Toni Reynaud on 28/07/2014 09:35:06

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Tony, thanks! - The Quad ESC hopefully will be a success. Can't see why not....time will tell
Ian, cheers mate.
Daz, What WILL be next??
Cymaz, cheers. Dont' know about bigger. It'd be quite refreshing to have a go at a shock flier or something like that next.
Toni, Thank you for the info and kind words. I will be following your lead and keeping the prop's spinning in the same direction (for the first flight at least). As for the mixes, using a quad ESC as I am, I would not be able to attempt it. Nice idea though
Will...... indeed!!

Anyhow, over the past few days, I've jumped from one job onto the next whilst the glue dried on various parts.
I do admit to not updating my log regularly enough but finishing late on the build has left me a bit knackered and the last thing I wanted to do was sit in front of the PC in my West-facing bedroom/office sweltering in the heat of the late evening sun. They're my excuses and I sticking to 'em.
Progress has taken place though in the form of ailerons being constructed. These were made from 1/8" balsa sheet in the shape of the aileron and the rest of their construction from 6mm depron and 3mm depron for the skinning. Sadly, no photo's of this process but pretty straight-forward. I used balsa sheet for the core of the aileron so that I could use the mylar hinges and Cyano as well as to provide a solid surface to secure the control horns which are of the bolt-through variety.
up1.jpg

Again, to facilitate, the mylar hinges, installed 1/8" balsa strip to the trailing edge of the wing just ahead of the aileron.

Aileron Servo installation
I am using the same servo holders in the Hercules build that I have used successfully in past builds such as the Sea Vixen (See pic below). I apologise for not taking any photo's of this procedure but.......... I forgot!blush
The servos will be installed later in the build .image.jpg

The servo extension leads ( 2 x 600mm extensions per wing) were routed to the location of the aileron servos and presented at the central leading edge where the ESC wires are.

The central trailing edge of the wing was finished in some fibre-glassed trailing edge I had left from an earlier build. This area does need to be reasonably sturdy in that the wing-mounting bolts will pass through at this point later on.up2.jpg
The rear of the wing centre section where the wing bolts will eventually go through.

There really was no excuse now why I couldn't start the skinning of the wings in 3mm depron. I checked around every 6mm rib for imperfections and gave the whole wing a light rub down with fine abrasive. Any lumps of hardened PU glue were flicked off so as not to cause bumps in the finish.
I really always struggle to describe any part of the skinning process in any of my builds so you'll forgive me for simply saying, 3mm depron was then applied to the wing's upper and lower surfaces.

up3.jpg
The wing with the external section skinned. The centre section is quite busy with wires and so they had to be safely stowed before I was able to apply the skin. Where cables passed over nacelles, I cut grooves into the pink foam to allow them to sink beneath the surface and applied a tiny drop of foam-safe CA to keep them in place.

The wings were skinned in 6 separate pieces of 3mm. 3 on the top, 3 on the underside. Fitting around the nacelles was quite fiddly but I got there in the end.
Anyhow, cutting a very long story very short, I ended up with this..........up4.jpg
up5.jpg
A bit of ligthweight filler applied around the joints and the nacelles and it looked half-reasonable.

Thursday evening and my room was at a reasonably comfortable temperature so I set to drawing my decals. decals.jpg

Log Update part 2 being uploaded now.........

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Log Update Continued.......
I dropped the design into my local printer/signwriter this morning and he delivered them to me this afternoon!!!! - Now that's SERVICE!
OK, so I was busy sanding the wing down and fitting foam wing tip blocks when he came and obviously, I had to try them out......immediately!

See what you think.up6.jpgup7.jpgup8.jpgup9.jpg
And yet another gratuitous photo of yours truly.....up10.jpg
And yes, I did rub down the wing tip foam blocks before I came home.
For now......
Regards

Roy

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