FTFF 2017 92" Ryan NYP

[Tench745]

So, with the stringers installed it's time to begin the skinning process. But wait! We need to add the hard-points for the landing gear before we lose access to these areas.
In this case I'm using a 1/2" x 3/8" poplar block that mounts into notches cut in F4 and F5. There are additional notches at the top of these formers for another such block, but I don't have the wood on hand a the moment, so we'll skip that bit for now.




There; now with that done we can glue in the custom stringer for the upper nose cowl section. There are some complex curves in this area that I'll need to play with a bit to figure out, so we'll come back to those later.




Sorry for the blurry picture, but this is the structure ready for skinning. The fiberglass rods remain in place to hold everything rigid while the skins go on. Once the side skins are glued in place the tail will be pretty stable and we can think about removing the support rods.




How do we attach the side skins? I'm glad you asked. Take a piece of DTFB (I'm using it paperless) and cut it just slightly oversized for the area you're going to be covering. Make a mirror image for the other side. Apply gorilla glue to all the stringers on one side, set the skin in place and tape in at both ends to hold it there while you repeat for the other side.




Now we come back in, pinning the sheet to the center stringer on each side to hold things square. Wrap tape around the edges to pull the skins tight to their respective formers. Check inside for any gaps between the stringers or formers and the skin; pin and tape as necessary to eliminate any you find.




I just want to point out, I'm not using masking tape here. I like to use "drafting tape." It's a little lower tack (less sticky) than masking tape and won't damage the foam quite as much if you leave in on for a while. Plus, I had a bunch laying around from hand drafting in college. If you're like me an hate standard masking tape with a passion, consider this or blue painter's tape. In the end, use what works for you.



More to come when I have time to do the write-up.

 

[wilmracer]

Nice work! Having the central alignment frame like you do really makes these bigger planes easier to work on at this stage. Looking forward to seeing this one in person!

 

[Tench745]

So, these next steps will be presented in a way that makes the most sense, not the order in which I did them. So, if you see inconsistencies between the photos, just know that they're a little out of order.

Now, because of the rather large distances between formers (as much as 11" between F7 and F8) we need to reinforce the edges of those side skins we just installed.
First thing is first, we'll take some of the 3/16" basswood square stock which will become the spars for the wing. This strip is clipped to the edge of the foam stock at each former to force the skin into a fair curve along this unsupported edge. Then we'll take some more of our 1/2" DTFB stringer stock, cut to fit between each former, and glue it to the inner edge of the skins, clamping these stringers to the basswood. The picture does a pretty good job of illustrating the resulting sandwich. Once the glue is dry you can remove all the clamps and the basswood fairing stick. The process is repeated with the upper edges of the skins as well.



Now we'll do the bottom fuselage skin. We rough cut a piece to fit the are we're filling in; in this case I'm doing a piece from F6 to F8. The basswood fairing sticks are taped in place again to help hold the edges of the side skins in a fair curve. Then glue is applied to the edges of the side skins, the formers, and the stringers. A rough-cut piece is then taped and pinned in place, playing the same game we did with the sides of finding gaps and closing them.



The next thing we'll tackle is the lower portion of the nose cowl since these are fairly simple curves. I've done one bay already before I remembered to take pictures.
I decided to make one panel to span between each quadrant made by the formers and stringers rather than trying to bend one large panel around multiple curves.



I'm using the paper I removed from the foam to make a template for each piece. The paper is cut oversized and held/pinned/taped as necessary to conform to the area we're trying to cover. I like to shine a light through from behind so I can see the surfaces and trace them along their centerlines with pencil. The paper template is then cut to that line and held up to check the fit. If all looks good the paper template is then traced onto foam.



The foam is cut out, bent to shape and pushed into place to once again check the fit. If it looks close, cut a duplicate and bend it the opposite way for the other side. If your build is straight and square the two panels should be almost exactly identical. Some trimming will be required.



Cutting the pieces little big is better than too small as you can always cut and sand the edges till it fits.
These pieces of sheeting all need a bevel cut on the edges which will glue to the formers to mate correctly between the one panel and the next.
Once it fits the way we want we do our "glue on formers and stringers, clamp and tape till gaps are gone" thing. I'll usually let one of these sections dry before doing the next so that nothing can move when I work on the next one. I also come in once the gorilla glue is cured and trim away any of the foamy squeeze-out so that I have a clean surface to mate the next panel to.

Please ignore the weird stepped former thing going on at the nose here, it was an experiment in ways to taper from F1, which is not actually round, down to a round spinner. These pieces will be different in the plans and I'll cover what I'm doing here in a later post.


The pieces between F3 and F4 are a little tricky because you have to crease the foam almost 90 degrees at the edge of F4. I cracked one piece when pre-bending it. If you support outside of the foam as you bend it and go slow everything should be ok. This is one place where keeping the paper on the outer side until the panel is glued in place can help prevent cracks forming during bending.

More to follow soon.

 

[Tench745]

A little more of the same needs to happen. I'm about to remove the interior sections of the fuselage formers which hold the alignment rods, so I wanted to add a little more structure to the nose, closing in the top between F2 and F3. The section forward of that may get left open for mounting the motor, or I might close it up now to keep it straight/square and cut into it all again later if necessary.




Next it the removal of the former centers. It's as simple as it looks; cut through the couple of support tabs left from the plans and pop the pieces out. Another piece of foam is slid in through the space between F3 and F4 and glued into place as a floor in the fuselage. I'm still debating whether adding sides to this interior box is worth the extra weight and reduced space for the strength it will add.








Now we glue on the little nubbin that will form the structure aft of F9, using a yardstick along the spine to ensure straightness. Glue on the side sheeting and reinforce the edges with our 1/2" stringers just like on the rest of the fuselage.









And this is here because I thought it was a cool photo. Looking down through the fuselage from the nose.

 

[willsonman]

Really coming along nicely! I love this foam sheeting technique. Used it many times and it always looks nicer than a folded box style fuselage.

 

[Tench745]

I know this thread has been dormant for a long time (two months?!) but I haven't stopped building in that time. So let's pick up where we left off. We'd just finished sheeting the sides and bottom of the Fuselage from F4 aft. The top was left open so that we could still get inside for finishing touches.
First things first, the rectangular cut-outs in the formers are lined with foam on 3-sides from F3-F7. The section between F4 and F5 will not have the sides to give a little more room for my mammoth hands, but the bottom piece will remain and later be reinforced with some 1/16" or 1/32" to act as a servo tray. Slightly oversize pieces of foam are bent and used as a wedge to clamp the side pieces in place while the glue cures.


Next, pushrod exits need to be cut for Rudder and Elevator. A pull-pull system would be more scale, but the upper elevator cables on the full scale did weird things where they were routed around the h-stab and I didn't want to deal with that, so I'll be installing some flexible pushrods and tubing instead. Eyeballing from drawings and whatever made the most sense on the model I determined the "proper" exit locations, pierced in with some thin music wire to ensure I had a smooth run, then heated the wire and melted the holes large enough to fit the pushrod sleeves though. This was fairly quick work.


Flexible pushrods must be supported at least every 6-8" depending on who you listen to. To do this I made up a series of little blocks to straddle the sleeve where it ran along the inner foam box. However, the guide sleeve is too far from the side of the fuse aft of F7 so little triangle shaped standoff blocks were made.


This picture shows the pushrod straddle-clamps in place. The triangle blocks are not installed yet.


Here are the 2 triangle blocks installed. The pushrods were epoxied in place in each straddle-clamp, at the fuselage exits, and into a groove cut in the point of each triangle block.


With that done we can close up the top of the fuselage aft of F6 the same way we did the bottom. I forgot to take pictures, but it's the same deal; put basswood stringers along the edge to get a fair curve, glue on a slightly oversize sheet, clamp, pin, tape, etc until there are no gaps, let cure. When the glue is dry, cut and sand to final shape.


The upper fuselage skin between F3 and F4 was not an easy piece to figure out, because there is no former shape at F4 to create a template from. A lot of trial and error created this piece V. The plans will be updated with a foam piece to glue to the forward face of F4 to make this process easier.


Here it is in place. The nubbin which sticks through the sheet forms the forward curve of the wing fillet. I think this bit will be omitted from the final plans as it's hard to work around and probably won't help in the actual forming of the fillet.

 

[Tench745]

I want to go back a minute and just cover closing up the tail before we finish the nose. There's a lot more to do forward than there is aft.
The Spirit had a sprung tail skid which I wanted to duplicate. The full size used bungee for it's suspension, but I have very limited access to this area which would make replacing worn bungees difficult so I opted to use metal springs. The foam structure in the tail is plenty strong enough for flight loads, but I didn't want to be stressing everything with spring forces etc on landing, so I opted to make a self-contained tail skid unit that could just be glued to the forward face of F9. The resulting device is pictured below. It consists of 1/8" Ply side plates glued on either side of a 1/4" basswood spacer. This assembly is then glued on a 1/16" ply backer to tie everything together.

The skid itself is 1/8" music wire with a smaller music wire loop soldered to one end as an attach point for the springs. A piece of brass tubing soldered on lower acts as the pivot for the skid. A 3mm button head machine screw is the fulcrum which holds this brass tubing into the wooden frame.

Once that was assembled it could be glued in place.

And once in place the last piece of skin on the tail was installed. Same process as all the others, align, tape to hell, trim and sand once dry.

 

[rockyboy]

That's a really nice setup for the sprung skid - I'm going to keep this in mind next time I do a tailwheel on a bigger build too - I fly from a pretty rough field and this could help!

 

[Tench745]

Before I can attach the motor, I have to know it's centered in the nose of the fuselage. Now, I suppose I could have just made some kind of template and stuck everything together, but this way I can kill two birds with one stone.
It has always bothered me seeing a "scale" spirit model with some stock spinner on it. They don't match the fuselage curves and just look goofy. I am modeling her in her Atlantic crossing configuration which has a rather blunt, rounded spinner on the prop.

I drew up the correct profile in Cad (in 1/6 scale), then drew lines every 3/16" to represent the thickness of foam board. I used the lengths of each of these lines to draw the diameter at that station. The green line is where the spinner will separate to insert the prop.


These diameters were then printed out as a template,


which was used to set a compass,


which traced the diameter onto paperless foam board...


for every single section.



Every circle was then cut out and reference lines were drawn onto each piece. It doesn't really matter where these are, just so long as they're all 90 degrees from one another. The circles were then glued and stacked in order on a piece of music wire, taking care to align all the reference marks. This makes sure they are centered on one another and the stack isn't leaning to one side or another. A 1/16" plywood circle was glued to the bottom for reinforcement after this picture was taken.


Now the fun part. Once your glue is dry, take this whole thing to your belt sander. Hold the music wire on both ends at a slight angle to the belt's direction of travel. Let the belt sander spin the piece, adjusting speed with pinch-force on the music wire and angle to the belt. The goal here is to have the sander sanding away on a face while also imparting a rotational force to keep the whole thing symmetrical. It's hard to explain, but makes a lot of sense the first time you see someone do it. Sand until the stair-steps are gone and you have a smooth, even profile. A few of the pieces will have some misalignment so there will be little gaps that need filling.


Once your filler is dry and sanded smooth, you can remove the little flat spot on the very tip and lay up a few layers of 1/2oz glass cloth.


With that done grab a razor blade and split the spinner along the green parting line indicated on the template.


Cut a hole the diameter of your prop hub through the lower layers. I'm afraid I didn't get any pictures of the cutout fitting steps. Basically, cut down to about where the prop should sit, set the prop in place, trace the lower face of the blade with a sharpie, cut to that line, repeat until the hub sits flush on the plywood backer. More work was done on this after these pictures were taken and the plywood backer was reamed out to fit the motor shaft.






The first offcuts from cutting the prop notch are then glued to the forward part of the spinner which is set in place. These offcuts are then trimmed to fit the front of the prop blade just like the back was.

Two pairs of 3/16" neodymium magnets hold the front of the spinner in place. The front plate should be drilled as necessary to accommodate your prop shaft and prop nut.

 

[DamoRC]

What patience and attention to detail! That spinner alone must have taken ages. Really looking forward to seeing this one continue.

DamoRC

 

[Tench745]

Actually, the laminating and basic shaping of the spinner only took an hour or so. Belt sanders make things fast. The prop fitting took longer.

 

[Tench745]

I just had to jump ahead of my build log's narration to post these.
I mocked up the wings and tail surface and it was just too cool not to share.
FYI, my build table is 8' long.

 

[Tench745]

Motor and motor mount

The motor mount is a pair of 1/8 x 3/8 poplar sticks, drilled to accept the motor mount. They look skewed in this picture, but I promise you they are parallel.


This could be attached horizontally or vertically, but I chose vertical. It made the most sense to my brain and it should resist flexing with higher G maneuvers better this way.
I left the upper forward foam off the fuselage so I could get the mount in place easier. The fuselage was then closed up. A pair of foam rings gets mounted to the front of F1 and sanded to match the contour of the fuselage.


Now I can screw the motor to its mount from inside the fuselage using a long screwdriver. This part is tricky. Now I can put some wood glue on the wooden mounts, thinned slightly with water to retard drying. The spinner is then slid onto the motor shaft and the whole assembly is centered so that the spinner is fair with the fuselage. Stand the fuselage on its tail and let the glue dry once everything is straight and true.


There's about a 1/8" gap between the backplate of the spinner and the front of the fuselage. Hopefully this gap will allow enough cooling air for the motor.

 

[Tench745]

This build has kind-of stalled. I'm feeling burnt out and lost as to what the next step is.
I should take a break, but I have less than 90 days to get this thing flying before Flite Fest.
Wings are built with aileron servos almost ready to go in, but I'm unhappy with the ailerons.
Fuselage is glassed, but the wing-strut attach points haven't been finalized.
None of the fairings have even been mocked up yet.
The landing gear to wing strut connection has me baffled.
I don't know how the ESC will mount or get enough cooling air.
Seven of nine cylinders have been glued up, but how to mount them is still a mystery.

In short, I'm lost and because my build log is so far behind the build, I don't even know how to ask for advice.

 

[Tench745]

In an effort to catch this thread up to where I am in the build, the next few posts will be a photo dump until I can come back in and add descriptors, assuming anyone wants them.

 

[Tench745]

Wheels and tail surfaces

BBQ skewer reinforcement in h-stab.


Melted grooves for Elevator joiner.


Measure in for bevel. Rough cut with knife then sand to lines.


Sand a rounded transition between bevel and flat.


Round Leading edge of rudder and trailing edge of v-stab.



EVA foam floor tile blanks. Stick rough sides together with spray contact adhesive.


(1) EVA blank, (2) 1/8" plywood hubs with, (1) 5/32" brass tubing bushing, (2) rings of 3mm craft foam.


Install plywood on one side, then bushing. Verify bushing is square, install second piece of ply with grain 90degrees to first. Lock bushing in place with thin CA. Add craft foam rings. All assembly with super 77 except where noted.


Sand like spinner on belt sander.


First sanding pass on wheel 2


Mocked up on fuse.

 

[Tench745]

Wings Pt 1

Lower wing skins. 2 sheets of foam edge glued into one. Rough cut chordwise, spars laid out square to root. Rib stations drawn in.


Tape removed from edge-gluing. Spars glued onto lower skin.


Add ribs and upper spars. Clamp heavily with sand bags. Hard to keep ribs plumb when clamping this way.


Add foam sheer webbing to main and secondary spars. Modified clothes pins make great clamps.


Cut out ribs between spars to insert wing joiners. Glue in place.


Add 3/16" basswood stock to tops of F4 and F5 to receive wing joiners. Cut notch for center section rib.


Try them on for size.

 

[Tench745]

Wings Pt 2

Cut out hole for servo pocket. Holes cut in ribs for servo extension with sharpened 5/8" brass tubing. Trailing edge from ribs tapered to point; top skin prepared the same. Sand LE of lower skin flush to ribs. 3/16" spar doublers on both sides of spar where struts will mount.
Tape TE together. Glue TE taper with carpenters glue, both spars and all ribs from TE up to main spar with white GG.


Support with wood battens and weight heavily.


Once dry, glue ribs from main spar to LE and tape heavily. No gaps.


TE is very thin and tore out. Glue in foam as necessary, fill with filler, and sand to shape before glassing.


Add 1/8" ply pads where spars will bolt in.


Rabbet out edge of servo pocket to receive servo mounting plate.


Servo mounting plates.


Reinforce screw holes in foam with inner tubing of Golden-Rod pushrod epoxied in place.


Wire cut wingtips and sand to near final shape. Finish shaping once glued onto wingtip.




Mock everything up for a photo op. and smile to yourself.

 

[Tench745]

Dummy engine and Landing gear.

(9) Williams Bros. 1/6 scale, Wright J-5 cylinder kits. 1 down, 8 to go.


All glued up. Pushrod tubes, intakes and exhaust are glued up separately and not pictured.


Crankcase made of foam board for layout purposes. The motor diameter can fit inside, but I don't know if it makes sense to use it that way.



The four fuselage-side landing gear brackets scribed out on brass sheet. (Second attempt)


Earlier version of same brackets. These were just a little too small.


Music wire landing gear and custom shock struts all bolted together. She's standing on her own two legs for the first time.

 

[JimCR120]

Wow! You do excellent work! Not only is the work excellent but just the fact your posting with so much detail.

Thank you for sharing the process. Looking forward to more.