FW Models ASW-17 is here!

[tewatson]

This build log is like a Tarantino movie...out of actual sequence. First thing I did (sometime last fall) was the stab servo, then the retract, then paused a while before moving to the wings where I spent about six weeks off and on, then the rudder pushrod, and finally to the forward fuse area and wiring for the most recent month or so. Now, onward (or back to) the stab.

The servo mounts right beneath the stab, so the linkage is short and direct. The airframe is supplied with two ball joints, one of which is unnecessary if the arrangement is tweaked just a bit. There's all kinds of room in there, so used a Servorahmen bearing frame with an MKS HV747 servo. If I had it to do over again, would have just put in a couple of ply rails and the same HV747R side-mount servo as on the rudder. Simpler for spares, and the bearing frame is probably unnecessary for the stab. But, here we are.

Since the elevator is top-hinged, the actuator rod moves slightly forward with "down" travel. So, the slot in the fin must be cut accordingly, and if the servo is canted to align with the movement plane, the lower linkage ball joint becomes unnecessary. The other consideration, as my pal Mike Smith found out through flight tests with his own ASW-17, is the upper ball joint engaging the actuator rod can move side-to-side if not secured, and thus change the stab trim. Placing a wheel collar on both sides of the ball joint solves this problem, although to be completely effective the actuator rod must be cut to exactly the right length, so as not to move when the stab halves are mounted. Not a big deal and the only negative is the actuator rod hanging out both sides of the fin during transport/storage, unless you want to disassemble every time, which would be a complete PITA as the rudder has to come off as well.

Consideration must also be given to the tail wheel, situated directly beneath the servo. The servo wiring and pitot tube plumbing pass through the area.

[tewatson]

Landing gear setup was straightforward. It is a nice FEMA assembly with CF fender, paddle-style brake and a servo bracket with multiple mounting holes to choose the exact position. It mounts with just two bolts which makes servicing easy, and has rubber bushings at the front for a little shock absorption on landing. Gear door springs are factory-installed.

Only remaining setup task is servo install and linkage configuration. I used heavy-duty 3mm ball links and shrouded the connecting rod with a snug-fitting carbon tube, buttered with JB Weld on the inside. Mike Smith had some bowing problems with his and I want to head off any issues.

The wheel brake setup is fairly simple. Mounted the servo on two ply rails just forward of the LG mounting bracket, and used an aluminum horn. For the linkage, it had to accommodate a ~40mm length change between gear up and gear down. Very fine braided steel cable would work, although it would require crimps and probably epoxy too...besides, I didn't have any on hand. Early on, thought about using braided Dacron tow loop material but dismissed the idea. After a discussion with Mike, he convinced me to give the Dacron a try, and it works perfectly.

Tied one end directly to the brake paddle arm, and the other to a threaded rigging coupler with clevis. Sealed the knots with CA and heat shrink over the exposed tails. Left the tails a bit long, so I can see if the knots start to slip. If this proves to be a non-durable solution, can always install a metal cable. We'll see.

[tewatson]

With the various electrical components positioned, I was able to set the fuse harness lengths and start figuring out wire routes. BTW, the Dymo Rhino 5200 labeler is the shizzle, and prints on special heat-shrink wire labels. Very cool, if you have that sort of time. Battery tray is next...

[tewatson]

The battery tray had to meet several design objectives: Secure, accessible, batteries and tray easily removable (together or separate), allow for tow release access, and provide a nose weight area. Using Duralite EXB Li-Ion packs, with four cells in 2S2P config, 5,800 MAh each.

Did a cardboard mockup first to test sizing and position. Once confirmed, fabricated the tray and forward support bulkhead from 1/4" birch ply, and support ledges for the rear. The tray engages a slot in the bulkhead and fastens to the rear supports with a socket screw on each side. A barrier ledge at the rear and a vertical support in between the packs keeps them in position. The same MGS epoxy, milled glass and silica formula secures the bulkhead and rear support ledges to the fuse.

A small velcro patch under the front of each pack, and a strap around both and under the tray provides secure retention. Nose weight goes in front of the bulkhead. At this point, final wiring connections can be made and remaining components (such as RXs) installed.

[tewatson]

On to the wings. There are three servos per side - outer aileron, inner aileron, and flap. The wing is delivered clean (no linkage cutouts, etc.) and also comes with separately-molded scale top linkage blisters. In the event the builder chooses an all-internal system, these can be left off. After the JS-1 wing debacle, I had no desire to try and keep all the top-side stuff internal, as doing so would result in less moment arm at the control surfaces, plus the top blisters are scale anyways. YMMV.

The outer wing at the servo bay is quite thin, and since the covers are all flat, keeping the servo arm inside is required unless one wants to cut holes in the covers. I didn't, so a slightly modified IDS setup was the ticket. The "modification" was simply mounting the surface horn slightly above the wing skin for added mechanical advantage and more servo throw.

Bruce DeVisser provided the CNC carbon IDS horns and links, plus servo arms for the MKS HV6130 servos. Servorahmen bearing frames were used, modified for socket head machine screws as detailed here: https://forum.scalesoaring.com/forum...ounting-screws

Prepping the outer ailerons for the horns required some root canal-like surgery...the thin section means proceeding slowly, out of the pure fear of seeing a Dremel bit poking through the skin. It required a real skin-to-skin excavation for proper fit and ensuring enough horn structure is left for good strength. Once the surface horns were reasonably located, then the path through the upper skin had to be defined, again going slowly because you can't put back what you cut away. Before installing the servo, added a 1/4" vertical grain hard balsa rib just outboard of the servo bay, for insurance.

It was a very fiddly, tight install but works flawlessly with zero slop and perfect centering. The servo and linkage JUST fits under the cover, and the top blisters will conceal the exposed linkage.

[tewatson]

For the inner wing panels, I went with conventional top-drive linkages for the same reason as before - more moment arm and no desire to keep them concealed. The inner aileron and flap servo bays are roomy in comparison to the outer ailerons, so installation was easier. The airframe comes with nice G10 wing surface horns and I used them, along with MKS HV6130 servos in Servorahmen frames, MKS aluminum servo arms, and 3mm linkage hardware.

There were two basic install constraints. The top skin cutouts could be no larger than what the molded blisters cover, and the servo arms had to fit under the flat covers. Apart from slightly different surface horn positions and servo arm lengths, the inner aileron and flap installs were identical. Inner aileron horns were positioned with the link pin holes even with the hinge line, flap horns with the holes ~2mm forward.

Prepping the control surfaces for the horns was simple since the install is through slots in the upper skin, but care is still required since there is also a carbon tube sub-spar in the surfaces, and having a Dremel cutoff disc spinning across your shit is not cool. Again, with surface horns positioned, the path through the upper skin and carbon-sheathed drag spar had to be defined, still going slowly so nothing more than necessary is removed. Before installing the servos, added an extra layer of carbon cloth in the servo bays. The same MGS epoxy, milled glass and silica mix secures the surface horns and servos. Finally, the servo frames have a beefy shelf above the outer bearings, so added a 1/4" vertical grain hard balsa rib between it and the lower skin.

Throws are good, the linkages are very stiff and center perfectly. Oh, and the flap throws match perfectly side-to-side throughout their range, without funky programming tweaks...I was most happy about that. The servos and linkages fit nicely under the flat covers, and the top blisters will conceal the exposed linkages.

[tewatson]

That brings us up to date for now. Currently working on small punchlist details like CG and seat pan/pilot. More later on.

[tewatson]

For the wing wiring, used PowerBox harnesses with DB9 connectors. They use high-quality wire with aviation-grade insulation, nice tight connectors, and a very cool molded strain relief. Saved a ton of time (I hate soldering DBs). Only remaining work is setting the proper lead lengths, and crimping on the servo connectors. The same wire is available in bulk, so also used it for any required extensions, and to the tail for the stab servo.

The outer wing panels use three-pin Molex locking connectors I had on hand. They can only be mated one way and the female connector mounts flush, so it's protected during transport and storage.

[Scalesoaring]

There is a whole lotta' great info in this thread, but it is costing me money - now I gotta' get a Dymo Rhino 5200 now with heatshrink tube cartridges - engineer's love tech toys! The latest generation of moldies offer some great hardware, but it is not always a clearcut installation, as Tom makes clear. Thanks so much for all the great info. I'll bet Mike Deleo will be happy to see this thread! BTW - I put his new FW 17 together before I shipped it to him - I haven't seen anything nicer or better built. I can't wait to see his 17 with the newer profile fly next to yours and Mike Smiths.
Bruce DeVisser

[yyz]

Mike is in fact very happy with all of Tom's hard work!

[tewatson]

The seat pan was a dilemma...first, it is somewhat poorly designed as it is too wide for a one-piece unit. Has to be inserted in the fuse without the pilot and turned 90 degrees, then fiddled into place, all while bumping against the wiring and equipment. Not conducive to convenient field ops or quick inspections. Any sort of support/retention system would be even more in the way.

So, at the start of the build I was toying with the idea of no pan or pilot at all. In fact, if there was a clean way to tint the canopy, I probably would have done just that. However, there was the box with a brand new Axel pilot inside, and a scale plane looks better with a pilot (I think so, anyways). Larry Jolly says "racers don't put dolls in their rides" so there's that...but ultimately the decision was made to give the seat pan and pilot a go.

My objective is simple: The ability to pull the pilot and seat as a unit, so batteries and connections are readily accessible, plus a quick internal once-over can be done each day at the field. Not so much concerned with uber-scale cockpit detailing, just a clean looking arrangement without any fiddling around required. A three-piece setup accomplishes this - side coamings fastened in place (but removable when needed) and a lift-out center section.

To make this work, the pan has to be split in the right places and some sort of support flange arrangement for the center section must be fabricated. First step was to strip the pan, so all the OEM seat belts, upholstery and control lever details came out. All of this was secured with hot glue, so removal was easy. After deciding where to make the cuts, but before cutting, I laid up some rough glass flanges using the pan bottom as a mold. Once cured, removed them and marked the pan for the precise cut lines, then used a razor saw to cut it apart. This step required care to ensure the cut lines were straight as possible, and parallel to one another.

The center section is more or less flat chord-wise, so it ended up kinda flexy once cut loose. To add some rigidity, taped the pan back together to ensure the correct shape and reinforced the center with several layers of glass. Next installment will cover the mounting arrangement and rough setup.

[lenb]

Hi Mike,
Nice thread, thanks for documenting the journey.
We've both been to countless scale soaring events and can agree that a beautiful scale sailplane taking off or landing without a pilot figure just plane looks wrong. After all, this is scale soaring, not pod and boom soaring. Isn't the reason for GPS racing with scale sailplane to represent the full scale racing? Try racing a full scale without a pilot. lol

Ok, rant over.

Im in the midst of starting the cockpit/seat pan installation on an Air Academy DG 1000. Thanks for the hints.

LEN

[tewatson]

With the seat pan cut, the next step was a mounting arrangement. Decided to keep it simple by securing each side panel fore and aft with screws into lite ply mounting pads just under the canopy lip. First step was to add a thin ply reinforcement on the reverse side of the side panels, at each mounting point. Then, with the mounting pads screwed to the side panels, used the belt sander to profile them for a snug fit to the fuse. Finally, glued each side panel in as an assembly, to ensure the mounting pads were properly located.

The result is nice strong attachments, and removal / reinstallation is simple. Next up is installing the flanges which were fabricated earlier, and a center section retention scheme.

[tewatson]

"Small punchlist details like...seat pan/pilot." Egad. This has turned into a project of its own, but worth it. Next step was to install the center section support flanges molded earlier, using MGS epoxy thickened just a bit with chopped glass and silica. These were clamped in place and left to cure overnight, then trimmed to final size.

Wanted to use some sort of locating pin arrangement fore and aft to secure the center section, and after some head-scratching, settled on aluminum pop-rivet shells. These are perfect...lightweight with a flat, unobtrusive head. After matching the center section and flange holes, used a couple drops of CA to glue the pins to the center section. The exposed heads will be less visible once the pan is repainted, and be more or less concealed by the pilot anyway.

Next is painting and re-installing the small details.

[tewatson]

Finishing up the seat pan... After all the fitting work was complete, removed the remaining upholstery and control labels (which are surprisingly detailed, BTW) and prepped the main components for painting. A coat of high-build primer and a bit of glazing putty here and there, followed by a finish coat of Krylon Fusion in satin pewter. Allowed everything to dry for two days, then reinstalled the upholstery and detail bits with hot glue. FW Model is sending me a replacement set of scale cockpit labels.

One other detail bit I ordered with the plane is an instrument panel. Not sure who makes it, but it is exquisitely detailed and looks really nice. New Axel fits snugly into his space, and I will probably add a simple headrest to the center section.

It takes about 10 seconds to remove or install the center section. With all the cockpit details settled, it's now on to a final CG check.