Building my Sig Astro-Hog Kit

Update 10-22-19 Repair after damage…

I find the fuel tank is mounted too high and so, when full, the fuel dribbles into the motor’s crankcase causing hydro-lock when I try to start the engine. Recently the prop torqued-off during one of these events and stabbed a hole in the left wing! … I was ready to fly, so I made a “field repair”: I simply taped-over the hole, reinstalled the propeller and spinner, cleared the engine, fired it up and enjoyed the flight.

See all the pics… Jump to REPAIR.

 

UPDATE 9-27-19: SURGERY!

After NINE flights, I noticed that the left main-gear strut was crooked, rocked-back from the vertical. A close inspection showed that… the landing gear mount block was loose? … ?

JUMP to the Surgery Section to see the “fix”.

IT’s Finished… my Astro-Hog is Finished!

Eric Reinhart poses with his brand-new Sig Astro-Hog!

… and it flies BEAUTIFULLY!

This BLOG ARTICLE…

… was written as I went along with the build of my Sig Astro-Hog. NOW that the model is complete… and flown… I have reorganized this article into proper chronological order… the earliest info at the top, from when I first ordered my kit on eBay, working through to the completed model and the Maiden Flight at the end of this piece.

I took a TON of pictures… and wrote like a madman… Enjoy my Sig Astro-Hog build… !

If you want to just JUMP TO THE MAIDEN FLIGHT, click this link.

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Original Post: June 3rd, 2019…

I bought a Sig Astro Hog kit from a dealer in Oregon on eBay. On the Sig website, the model is $124 + unknown shipping... on eBay it was $120 + $25 shipping... Sold!
I bought a Sig Astro Hog kit from a dealer in Oregon on eBay. On the Sig website, the model is $124 + unknown shipping… on eBay it was $120 + $25 shipping… Sold!

I bought a Sig ASTRO-HOG kit
…Let the love affair commence!

I am not kidding… dreaming, starting, building, completing, flying a large model you build from a kit… the experience can only be compared to a love affair! Once the decision is made and the first monies are spent, the thing goes straight to your heart and soul.

This model was designed in 1957 as “the first” full-house RC model airplane; swept all the contest events in 1958… 4-channel, 71-inch wingspan… over 7-1/2 pounds… supposedly flies well with an OS .46 at sea-level… recommends a 60 for higher altitude flying sites… and I have that nice OS 65LA “left-over” from my Decathlon. “Will fly every maneuver in the book and flies slowly enough to give you the time to enjoy it.” … looking forward to it! This newer version of the kit includes updated building methods, wing-bolts, and tricycle landing gear. Lots of dihedral… the original model had 8″ under each wingtip for a total of 16″ dihedral… this new version is down to 6″ under each wingtip: very stable in flight.

Sig Astro Hog kit on eBay.

The Sig Astro Hog instruction booklet... online!

I DOWNLOADED the INSTRUCTION MANUAL before I purchased the model. … and I see die-cut and printed balsa and plywood parts… and of course, balsa sticks and sheets. … In the manual, I see nothing about LASER-cut… so… old-school, all the way!

I am IN FOR IT, now!

Sig Astro Hog kit instructions... Wowzers!

Let the DREAMING commence!

What color-scheme should I use to finish this model?

I COULD go old-school and follow the box-top color scheme… but, what fun is that?

I open-up Photoshop & attempt some color designs.

I could go with a standard simple sport-model scheme… (That’s a blue OS 65LA that I have to include as part of the color ideas,)

Cream and Blue… I like it… but…

The Astro Hog is a child of the ’50’s! … it needs “more!”

How about decorating it as “HIGHWAY PATROL”… using design elements of old patrol cars… could be fun… black-white, blue accents… big gold medallions… Hmmmm… …

Thinking about Sig Astro Hog as Highway Patrol!

or, maybe: Civil Air Patrol!

Sig Astro Hog as Civil Air Patrol??

THAT’d be AWESOME… Red, White & Blue!
… and the “design” is already created in real-life… just need to modify it for a low-wing open-cockpit model!

… but, PLENTY of time to think about colors!

The kit should be here on Monday, June 10th. It will take me awhile to enjoy diggin’ through the box of parts, studying the manual in comparison to those parts… thinking about hardware required before I start… THEN: I will be in New Jersey from Monday 6/17 thru Weds 6/26… so… maybe, THEN I might start gluing sticks together…

Back with more of the “Build a Sig Astro Hog kit” saga once I have the kit in-hand. “See” you then!

— Eric

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Update: June 27th, 2019…

My Astro Hog arrives!

My Sig Astro Hog kit arrives... big box!

Wow… that’s a big box… Longer and heavier than I expected…

The Sig Astro Hog kit NEEDED that big o' box!

Wow... that's a big lumber-yard in a box... my Sig Astro Hog kit.That is one large box! … and the contents pack it all the way full.

Check it out… This kit was manufactured over TEN years ago… I hope it’s not too dried-out!

"delivery date" was over ten years ago!

Let the FUN, commence!

I cut the plans into a few parts... Sig Astro Hog kit.

The first step in the project was to cut the plan-sheets into the bite-sized parts I would require during the build. When I built the Sig Kadet Senior, I had to cut the plans into, like, six pieces. For THIS build, it looks like I only need to have the two wing panels and the horizontal-stab plans go onto the building board.

… more to come soon!


Update: July 30th, 2019…

Starting the Build… the left wing…

I got a start on building my Astro Hog… Got all the tools together… poured a beer… and got busy!

Got the tools together to start building my Sig Astro Hog kit.

… basic structure started… beer consumed!

Building the left wing panel on my Sig Astro Hog kit.

“Like magic”… after several days of “an hour here and an hour there”… that left wing panel is probably 80% complete… still needs to get cap-strips on all of the ribs, top and bottom, and needs to finish-up that wingtip trailing edge but need to deal with the ailerons before I can finalize the shape of the wingtip. CLICK ON THIS PIC to see full size.

Lots got done! ... it's all in the sanding! Sig Astro Hog Kit build...

See the nice semi-symmetrical airfoil shape… both the top and bottom of the wing have their planking in place… and see the landing-gear mounting block…

Got the tools together to start building my Sig Astro Hog kit.

That leading edge was a double layer of flat sticks that I sanded to final shape.

That wingtip has the leading-edge planking moistened and curved into final shape… and sanding is everything!

Sanding-away on that crazy wingtip construction!

… more to come soon!

Update: August 5th, 2019…

The right wing comes together…

Today I got busy and did the basic assembly of the right wing. I have been using the humid, Arizona “Monsoon” weather as an excuse to take time-off from “the build”… “too moist around here… don’t want to build a warped structure!”…  … But today was dry (100 degrees with the AC on)  and I wasn’t busy… so “no excuses”… I got busy….
Here you can see that main spar pinned to the building board with that left wing panel there, in the way… just for inspiration!

Mighty oaks... right wing spar is pinned to the board! Sig Astro Hog build.

In a matter of “a few hours” I had the ribs and spars in place with a strip of wood that will become part of the leading edge glued onto the front of the ribs… and another strip of wood glued to the back of ’em to become the trailing edge… and the top and bottom 3/32″ trailing-edge sheeting glued into place. … You can’t see it, but the laminated wingtip is also in place. … Amazing the sculpture you can create with balsawood and super-glue!

This IS kind of an amazing structure!

Unlike most kits I’ve built, there is no “notched leading and trailing edge stock”… and in fact, the only factory-shaped parts for the wing are the ribs and the die-cut plywood wingtip forms… (OK, there are also lite-ply landing-gear-block-mount doublers to strengthen the weight-bearing ribs near the center of the wing and a couple of other little die-cut doodads for the structure… but not a modern, laser-cut interlocking structure, or ANY structure, really!) The RIBS have notches to fit over the spars; and that’s it. … So I pin the main spar to the board. I super-glue each notched-rib onto the spar (aligning each rib with the printed plan-sheet while using a small triangle to be sure each rib stands straight and is square with the drawing)… Then I add the top-spar into those notched ribs… and then start gluing-on simple strip-stock that will become the leading and trailing edges. It is, rather miraculously, coming out straight and square! The spars are straight… and if I sight-down the spar and the leading- and trailing-edges, they, too, look straight… amazing!

Amazing what can be sculpted from bits of balsawood glued together! My Sig Astro Hog build.

Left and right wing panels… doesn’t LOOK like it will fly… at least not yet!

That left wing can hardly wait for that right wing to be done! My Sig Astro Hog build,

 

Update: August 9th, 2019…

Horizontal Stab gets put together….

I have been working on the color scheme plan using Photoshop and an old image from the instruction booklet… I think THIS will be the final look of the model… red, white, and that sky-blue. … with Astro Hog logo decals.

Color scheme for my new Astro Hog... My Astro Hog build.

– – –

Earlier this week I was in the middle of final assembly of the right wing, getting ready to attempt to flex/bend/warp the leading edge sheeting onto the wingtip……

Getting ready to warp the leading-edge sheeting onto the right wingtip... my Sig Astro Hog build.

… when I ran out of Medium Zap-A-Gap!

… I drove to the local hobby shop and… they were out of stock! Had to go to Bullhead City, anyway, and so checked the Hobby Lobby store… no luck. So, I ordered a 1oz bottle on eBay… paid through the nose… and had to wait for delivery.

While waiting, I decided to build the horizontal stabilizer using good old Elmer’s Wood Glue… that yellow aliphatic-resin glue… easy to work with, dries pretty quickly, sands well. (My entire Kadet Senior was assembled using this glue!)

I laid out the parts… read and re-read the instructions until I understood the program… and got started!

Laid out the parts for the horizontal stab... Sig Astro Hog build.

Good old-time methods, here: Cover the plan with waxed-paper, position parts, double check the fit, apply glue and T-pin the parts into place on the plan. Each of those “sticks” had to be trimmed to fit perfectly into place; I used that disc-sander to make minute tweaks to angles and lengths of those sticks… slow and careful work..

T-pins and yellow glue... and a disc sander. My Sig Astro Hog build.

My 18-month-old cat, Sophie, was NOT a big help! She was curious and all over my table… but proved camera-shy when I took her portrait!

My helper didn't help me very much!

Unlike when slamming through assembly with CA glue, I had to actually clamp and wait for that yellow glue to set before I could move from step to step. (Amazing how many little clamps, tools and gadgets we pick up over the years!)

Had to clamp and wait for Elmer's Wood Glue to set...

This model is a real old-timer… Elevators, I had to cut them to shape from rectangular tapered stock… and the elevator is made as two halves joined together with a 1/4″ wood dowel and 6-minute epoxy.

Elevator, I had to cut from rectangular tapered stock, made as two halves joined together with a 1/4" wood dowel and 6-minute epoxy. My Sig Astro Hog build.

Finally, I had all the parts shaped and glued together…

Finally, I had the parts glued together... ready to start sanding! My Sig Astro Hog build.

… and I was ready to start sanding.

I could read what the instructions said about sanding and the final shape of things… and the caution, there, not to sand too much and so weaken the structure… and I tried to visualize what they were calling for… I studied the plan… I knew in my mind’s-eye what I wanted to see as I worked… I could not really imagine HOW the wingtip of the stab was going to take shape… and the rounding of all of the perimeter edges, moving from soft balsa to hard spruce on the leading edge and at the wingtips of the stab… what to do… ?

I decided to just go ahead and start sanding… I was sure “something” would take shape and I would just go with the flow.

… and… … there it is… almost ready to cover!

So, I sanded like a mad man!

I probably sanded “too much” in my attempt at near perfection… but the outline and edges seem to match the plan drawings… anyway: that step is done! … Next I will gouge the hinge-slots into the trailing edge of the stab and the leading edge of the elevator… … soon… and be ready to cover them!

FIREWALL gets started…

The Astro Hog kit’s firewall is supplied as two layers of 1/8″ plywood that I have to laminate together with Epoxy glue. I chose the 30-minute epoxy since I was in no hurry… compared the two parts to be sure they were identical… and then rubbed-in a thin sheen of epoxy to one side of each part, added a little more glue to the center of the parts and carefully layered the two parts together into a single unit… using all of my little clamps to hold things tightly together while the epoxy set-up. I checked and re-checked that the two pieces stayed in “perfect” alignment as I applied the clamps.

The 2-part firewall is assembled with epoxy and clamps! My Sig Astro Hog build.

Success… I got a nice, solid piece. Now comes a critical part… transfer the model’s center-line and the aircraft thrust-lines onto the firewall… map-out the exact location for the motor mounts, spaced so as to be a perfect fit for the motor I plan to use… No problem… !  I used calipers for the engine dimensions, straight edges and a machinists steel ruler/straight edge to get the lines transferred to the firewall.

Mapping-out the center-line and thrust-line onto the Firewall... My Sig Astro Hog build.

That’s IT for today… I am about ready to finish that right wing panel within the next couple of days… and then I can start on the fuselage!

—-

– – –

Update: August 12th, 2019…

Fuselage starts to take shape…

This is a “new kind of build” for me… The printed fuselage sheets are laid flat onto the table and the various longerons, braces and fuselage doublers get cemented to them…

Assemble the fuselage sides while they are in flat, printed sheets, flat on the table. My Sig Astro Hog build.

Then I cut out the fuselage sides to the printed outlines…

… and I then aligned the two fuse sides, back to back so as to check that they were, indeed,identical…

Cut out the two fuselage sides and align them, back to back, and check for two identical sides. Sig Astro Hog build.

Next, I 6-minute epoxied the firewall and bulkhead/formers into place on only one of the fuse sides… and after that epoxy had hardened, I used 30-minute epoxy to add the second side… making sure that all was properly squared-up and that the tail-ends aligned when I pinched things together back there. I used cans and bottled to weight-down the pieces as the epoxy hardened.

Add the firewall and formers to one side and wait for them to dry... then assemble the fuselage. Astro Hog build.

… and there we are… fuselage built… so far!

Firmers and stringers are added, Sig Astro Hog build. Carefully pinch, align, and glue the tail-end of the fuselage. Sig Astro Hog build  Looking good, yes?!

Had to try out my astronaut in my Astro Hog! … He MAY become the pilot… if so, it will be his first new assignment since he crashed my Decathlon!

Trying out my Astronaut pilot in my Astro Hog. My Astro Hog build.

 

Update: September 5th, 2019…

This build is taking its time! … I haven’t made an update since August 12th… so, now on Sept 5th, I have a TON of images to share with you!

Today, I am thinking that THIS will be the color scheme… Jet White, Sky Blue, and Dark Red MonoKote.

Color scheme for my new Astro Hog... My Astro Hog build.

But… to start with at the top of this update: I discovered an error I had made, earlier. I had thought I was following instructions as I glued these balsa triangular shapes to the fuselage side. … but I found that I should have glued them so as to allow a 1/2″ balsa block to fit flush with the fuselage/bulkhead-former outline. So… I had to razor-blade off those balsa pieces and reattach them in their proper location.

Looking good… My only intentional deviation from the kit, so far, is to build a cockpit “tub” to hold my Boeing astronaut doll pilot rather than the flat piece of plywood that is supposed to serve as the floor for the cockpit. That floor would be just a 1/2″ from the lip of the cockpit. I built a rather large balsa box which will mean that I must move the three basic servos to new places to allow space for that tub.

Boeing souvenir pilot may be priceless collectible!

That astronaut I keep showing you is an official Boeing souvenir, with a Boeing souvenir-shop tag and barcode showing $4.99… I cannot FIND this exact doll on eBay or a Google search… it will probably be a $5000 doll on “Antiques Roadshow” someday… except, obviously, MINE will be Nitro-fuel soaked! … but he looks GREAT in this Astro Hog model!) … So… the Astro Hog will be his SECOND assignment… I hope he accepts the position for the many years ahead.

Boeing souvenir pilot may be priceless collectible!

Back of the Boeing souvenir pilot...

He came to me from the Goodwill Store… probably paid $0.50 for him… and, if you think about it, he is probably too small for this model… a man, inside that bulky spacesuit would be a small fellow… but IN that suit, he fits very well!

This guy originally had a body and legs full of polypropylene pellets for weight and shelf-sitting stability… but I recruited him as a pilot for my ill-fated Decathlon and he was “perfect” except he needed to lose some weight! … so I cut small slits in his feet and drained-out those pellets… which I discarded! … now he is “weightless”; GREAT place to be for an Astronaut!

My Boeing souvenir astronaut has all of his tags...

ANYWAY… back to business!

… I then painted the balsa tub with black Sig fuel-proof dope thinking that I might not be able to reach into the farthest corners of the box, later on.

Now I am attaching the rear fuselage bottom planking…. will trim off the excess after letting it dry “over night”.

I traced paper patterns onto sheet balsa to get the shapes required for the curved planking.

I wetted the balsa after first gluing the base-edge of it into place. Then I wrapped the wet balsa over the formers and aligned the top edge with the center of the top stringer. Pins and rubber bands held things together.

The nose is built-up from balsa blocks that I had first band-sawed into the shapes you see here…

I trimmed the cockpit area to shape as per a template provided by the kit. I also test-fit my Boeing astronaut doll to be sure he fit well.

The planking is now all in place. I had used rubber-bands to hold the wet, curled balsa… which turned-out to be an error! There are only a couple of stringers and not much support back there, and those rubber bands caused “flats” in what should have been the otherwise natural curl of that wet balsa. Those flats from the rubber-bands meant I had to do more sanding and filling… and I did not want to sand so much that I thinned the balsa too much… so, my finished model will show some flats, back there.

Man… look at that nice solid seam on the nose planking!

… but I missed the “perfect fit” on those aft-end panels … leaving a pretty good gap to be filled with putty.

Gotta stop and enjoy the project.. Looking good!

I band-sawed that balsa block, almost too much, so as to avoid sanding-off that much wood.

The inside surface on that block needed to be carved-out so as to allow the motion of the nose-gear steering arm.

I discovered that I’d have to make that nose bock be removable so as to allow engine mounting and removal… and allow for future nose-gear steering adjustment. So, I created and glued-in four hard-wood blocks that will hold wood-screws to attach that block.

Fun to see things come along… I fit the motor, just to see it!

I located and drilled the four screw-holes… I counter-sunk the holes to accept servo-mounting screws to mount that block with the screw-heads well below the finished/sanded surface. I removed the screws and hardened all of the holes with thin CA… then I ran the screws back through the holes a couple of times… Ready to go!

Next came “shaping with a knife” rather than trying to sand-off so much wood! I was successful… between whittling and sanding, the shape was coming together.

… worked on the underside of those blocks, too!

Time for a glamour-shot as part of this long-term love affair!

This shot shows the flats and humps that resulted from me trusting those rubber-bands. That “lit from the side” by natural light really shows the flaws!

I set the fuse aside and went back to the Right Wing…

I painted the sheeting with water… let it soak in for awhile, and then crunched it into shape on that wingtip. It’s a compuond-curve and the wood REALLY did not want to go there. The water and lots of cussing got it done!

The extra wood got shaved/sanded-off and the Leading-Edge strip was applied.

You can see that flat Leading-Edge strip running from tip to root-rib.

Then I started sanding like a madman… trying to contour that flat “strip” into the airfoil shape of the wing by taking my cues from the shape of the ribs… The tips take a lot of careful attention.

The airfoil-shape is looking correct… now just need to trim/sand that root-rib “flat”.

With both root-ribs sanded flat, I tried a test fit… “Perfecto!”

Another test-fit / glamour shot!

MT Bob loaned me a 1/4-20 tap so I can tap the wing-bolt holes. I tried a few test-taps on scrap hardwood. The first one I forced too much. It turns out that only a light pressure is required; as with most tools: let the tool do the work.

The wing is now epoxied together! … Look at all that dihedral!

The new wing’s dihedral is comparable to my old Kadet Senior wing. That’s a lot of dihedral!

I had to open the box in the center of the wing that will hold the aileron servo. I used a knife to slice through the balsa planking and an X-acto saw blade to saw-out and remove the web created by gluing the two root-ribs together… also used a rotary-cutter bit in the mototool to trim-out that web all the way to the floor of that servo box.
(I know… that’s the wrong servo-horn on that servo… “:o).

Glorously, that seam between the root-ribs looks to be a perfect, tight fit… but there is a bit of a wide seam (filled with epoxy) along the bottom-edge of the seam. The finished wing will have a fiberglass tape wrapped around that wing center joint… so, I believe the wing will be solid and strong.

… AND the shape of the fuselage wing-saddle looks really good… it will need only a light sanding to smooth that saddle area a little.

It’s AMAZING what you can create with balsa if you just don’t take “No!” for an answer… keep working your way to “Yes!”

Next… I must apply MonoKote covering to the inside of the trailing edge of both wings and cover the two ailerons so that I can install the ailerons and continue to assemble the wing. Quite a few pieces are still to be added as I finish the shape of the trailing edge around those aileron control rods… and I need to add wing-bolt support plates.

More to come… soon!

– –

Update: September 8th, 2019…

Back to work on this thing… Following the instructions, I covered the Ailerons and the trailing edge of the wing… and installed the hinges and mounted those ailerons with the control levers attached. … Then I epoxied those levers to the trailing edge (keeping cement off of the rotating parts). IF I HAD BEEN THINKING, I would have epoxied those control levers to the trailing edge NOW and then, later, added the ailerons AFTER I had covered the entire wing. As it is, I need to build-up the final trailing edge, sand to fit… all without damaging those ailerons.

Ailerons hinged and mounted to the wing... Sig Astro Hog build.

Epoxied the brass sleeves to the trailing edge.

Then… onto the Horizontal Stabilizer

I “cut” (gouged) the CA-hinge hinge slots into the horizontal stab and the elevator.

Gouge the hinge slots.

I use a large X-acto knife to start the slot… cutting the depth and width I want. Then I put a #11 X-acto blade into the handle BACKWARDS and use that steel shape to widen the knife-cut slots… the result is a slot that snuggly accepts the CA-hinge material.

Tools used to gouge the hinge slots for CA hinges.

Then I drill a 1/16″ hole into the center of the hinge slots as a way to help the thin CA wick-into the CA hinge and the balsawood. That hole gives the thin CA a path to follow.

Drill 1/16" holes in center of hinge slots to give thin CA a place to wick through.

With the slots all cut, I was ready to cover the stabilizer. I covered the bottom of the piece first… fighting my way around those rounded wingtips.

One side of the stab is covered...

MANY times this project boils-down to: Do not accept “NO.” as an answer. Keep struggling until you get to “YES.” … You CAN, indeed, get MonoKote to stretch around complicated compound-curved wingtips… just keep heating, stretching and tugging on those corners! Apply heat, let it cool, enough, to adhere, and then heat/stretch, some more! I did not really leave myself enough film to work those rounded edges… but I went ahead and heated my fingertips and got the job done! … I do it ALL without using the “heat gun” except in the case of emergencies. Here, I only used my regular covering iron to get these tips rounded and finished…. just keep at it!

never give up... don't take no for an answer... you CAN make smoothly rounded wingtips in MonoKote! Sig Astro Hog build.

Finished wingtips are lookin' good!

OKAY… I got it done without TOO much cussin’… looks nice on both sides on both ends.

I see that I work really slowly. The date-stamp on my images show me that, from the time of the first photo with the raw slots already cut into the stabilizer, until I took that final photo, below… TWO HOURS for the progress on the horizontal stabilizer… from hinge slots through covered/finished piece.

Finished horiz stab on my Sig Astro Hog.

I covered the elevator without incident… cleared the hinge slots, one more time… and then attached the elevator to the Stabilizer with those CA hinges. … Success!

Finished stabilizer... ready to install onto the fuselage... my Sig Astro Hog build.

– – –

Update: September 9th, 2019…

Today I filled-in the trailing edge… fiberglassed the wing’s center seam… and painted fuel-proof dope inside the engine compartment… Now I gotta let things “dry overnight”.

To start the process, I added the 1/16″ plywood Wing-bolt plates to the underside of the wing.

The wing-bolt plates get added to the wing. My Astro Hog build!

Then I glued-on scraps of aileron stock to start to build-up the trailing edge. Then added a bit of scrap balsa to fill the little voids, there… and then sanded that area to fit the wing’s contour.

Scrap balsa fills-in the trailing edge... and then is sanded to fit the wing's contour.

The wing-strengthening fiberglass strip gets epoxied into place as three little pieces on the top surface and one longer piece on the wing’s underside. Mix-up a bit more epoxy than you might think; that glass strip can hold a LOT of epoxy!

Install the fiberglass as several pieces using a bit more epoxy than you might think!

Finally, for today, I painted the engine compartment, including what will be the inside of that removable “chin” piece, with Sig fuel-proof dope. I brushed on a coat of clear dope… waited a couple of hours and then touched-up the critical spots with some more clear… waited, like, an hour (not long enough) and brushed-on a coat of gloss black Sig dope.

I was imagining how the final MonoKote covering was going to go on around the engine compartment, there… and painted, accordingly. I will be wrapping the MonoKote at least 1/8″ over the edges all around the engine compartment and really wrapping that chin panel… not its black “top” surface… but covering will go all around the outer edges with the vision of making the entire engine compartment fuel-proof for years to come. (I have been flying my Sig Kadet Senior, several flights a WEEK, these days, for eight years, so far! … and I plan to fly my Astro Hog for at least that long!)

Brushed on Sig dope to fuel-proof the engine compartment. Sig Astro Hog.

Next time, I will be fitting the wing to the fuselage and must start thinking about covering and final assembly!

 

Update: September 10th, 2019…

BOLT ON THAT WING!

Finally, I am at the point to where the Wing is complete… and the Fuselage is almost complete. TODAY, I located the wing-mounting holes and drilled them into the bulkhead ahead of the wing location in the fuselage. I test fit the wing several times… it looked like it would drop in, just fine.

Then, per the instructions, I sharpened short dowel pins to get a pointed end on ’em. The idea is to install those pins, tightly, with the pointed-end sticking out… then I would align the wing and slide it up, against those pins, and so mark the location for the drill-points on the wing. Then I would drill the holes and epoxy the pins into place in the wing…

Well, it took me most of the day!

All started well… I located and drilled the 1/4″ holes in the bulkhead. I cut the two dowel-pins to size and sharpened their ends. I tucked a bit of string into the holes so that the pins were a tight fit.

Dowel pins installed, pointed-end out using a bit of string so that they fit tightly.

The pointed pins are to make dents in the leading edge to mark the drill positions in the wing.

The pins are to make dents in the leading edge to mark the drill positions in the wing.

Ahhhhhhhh… I muffed it!

I positioned the wing… looking good! … I slid the wing against the pins… tight… removed the wing and… hmmm… looked off center. Tried again, this time with paint on those points so I could see the new “dents”… much better. I carefully drilled the holes into the wing… test fit… and was almost 1/8” OFF from centering the wing. (The neighbors could probably hear me yelling!) It’s only one of the most critical elements in the entire construction, and I had done it poorly. Grrrrr…

I found some balsa and shaped it to fill the bad holes. I, again, painted the dowel and slid the wing against them… and got new marks. I drilled new holes into the leading edge… Grrrrrr…

Not good enough. I elongated the holes in the leading edge until I could see that the pins were going-in straight with the wing centered on the fuselage. I applied 6-minute epoxy into the holes and against the pins where the fit WAS tight, leaving the voids to be filled-in after the epoxy set. One at a time, I glued those pins. … Then, as per my plan, I filled the oversize holes with bits of scrap balsa and epoxy. … The pins are tight… they are straight and solid… the wing fits nicely… but WHAT A FIGHT for such a simple step!

Wing mounting dowel pegs... They are ugly but they are in. My Sig Astro Hog build.

What’s that rattle?

During that fist-fight (above) one of the dowel-pins dropped inside the wing! (I think the neighbors heard me, again!) Behind the leading edge in that area of the wing is a generous balsa filler-block designed to mount that pin. Drilling into the wing, I drilled through that block. While doing a test-fit as I enlarged the hole, a pin simply dropped through the hole and is now trapped inside that completely enclosed bay of the wing, never to be seen, again (I hope). During my final glue-job on that replacement pin, I tried to put plenty of epoxy on the butt-end of that pin so as to catch/adhere that rogue pin inside the wing. I angled the wing, I rattled it about… but, no good that errant pin is on the loose.
“That’s alright… gives me a story to tell!” … I put things down and walked away for an hour.

Attached the Wing-mounting Blocks & Bolts

I sanded the hardwood blocks into the required shape to fit against that rear bulkhead and fuselage sides and also have the proper dihedral angle so as to match the wing saddle… that was easy, actually; the illustration in the instruction booklet was accurate and I was able to set the fence on my disc-sander to match the manual’s illustration… and the resulting, sanded piece dropped right into place. I then epoxied the blocks into place and also trimmed and sanded some balsa blocks to add strength to that hardwood block’s install. My theory was that I was creating a strong, three-dimensional web of hardened epoxy that would firmly grasp those hardwood blocks even though it was only soft balsa in those triangular blocks. I used plenty of epoxy. (There are triangle-stock wedges installed below the hardwood blocks, as well… but the angle of these photos doesn’t show them.)

… I marked a dot onto the blocks for my anticipated drill locations.

I mounted a flap of wax-paper and marked the drill-locations from the blocks… then slid the wing into place and drilled the holes using a 3/16″ drill bit, making an attempt to align the angle of the hole with the flat plane of those wing-mounting panels so that the bolt heads would cinch-down flat against those panels.

I mounted a flap of was-paper and marked the drill-locations on the blocks... then slid the wing into place.

Success on THIS part of the job!

Drilled the holes at the proper locations.

I used the 1/4-20 tap I borrowed from MT Bob and tapped the fourth and fifth holes that I have tapped since machine-shop in 1970. It worked! … Following Bob’s recommendation, I tapped the holes, test-fit the nylon wing bolts… snug and perfecto!… removed the bolts and dripped several drops of thin CA into the threaded holes to harden-up those cut threads… waited about an hour and then carefully followed those threaded holes with the tap, just to clear ’em out.

Tapped the wing mounting blocks 1/4-20.

Then I re-drilled those holes in the wing with a 1/4″ bit and stretched the holes, a bit, so the wing bolts would easily pass through them.

Stretched the holes in the wing with a 1/4" bit.

Mounted the wing… First time EVER!

… Nice alignment, tight fit without stress.

Mounted the wing... First time EVER!

I set the finished horizontal stabilizer into place… and it drops into proper alignment with the main wing… Awesome!

First alignment test with wing mounted. My Sig Astro Hog build.

That’s it! … I’ve HAD IT!

… for TODAY, anyway… Don’t take “No.” for an answer… keep at it until you get to “Yes.” … and then set it aside, for awhile, and enjoy what you’ve created. … I decided to put it in the corner and come back, later. I left the wing attached, tightly assembled, so as to let it stress-out “overnight”. I’ll be back at it, tomorrow… probably.

– –

– –

Update: September 13th, 2019…

Let the COVERING Commence!

Just a few more things to do before covering the wing…

I added a weight to one wingtip so as to balance the wing. I don’t know WHY it was out of balance… just “one of those things.”

Added weight to balance the wing.

Then I made sure that the landing gear blocks would accept the formed-wire landing gear wires… and I rounded out the shape of the holes to allow for the arc in the bend of the wires.

Clear-out the wood where the curved-arc of the bent wire will fit.

I covered the bottom of the wing… The curved wingtip area was a bit of a challenge, but not a “problem”.

Almost easy to cover the bottom of the wing...

Bottom of the wing is covered!

The TOP of the wing… and the wingtip IS a challenge!

CLICK this image to see full size... Keep at it! You can DO it!

It took me about 35-minutes to “do” that wingtip and work out all of the potential wrinkles for a smooth finish. A mixture of patience, shouting, and carefully applying heat, stretching, letting it cool before you let-go… keeping after one little set of wrinkles at a time as you work your way around… and… it can be done. If I had had more hands, I might consider using the heat-gun to stretch larger areas at a time… but with just me, there, alone, in the dungeon, I decided to use the standard covering iron for the entire process. It worked.

DID IT... Nice wingtip!

I did it TWICE!

I did a great job on both wingtips!

With the wing covered, I decided to install the Aileron Servo. … It was no big operation: This Astro Hog uses the standard “trainer-style” single servo aileron configuration.

"Trainer-style" aileron servo installation. My Sig Astro Hog build.

I have always read about “aileron differential” (meaning more UP aileron than DOWN aileron) and I wanted to try it on this model. (We’ll see if it’s a good idea when I try to FLY it!) By putting the control-rod holes behind the center of the servo pivot, the action will pull the UP side (giving more UP aileron) further than the DOWN side.

Aileron differential... good idea??

Wing is covered and complete… ready to decorate! It’s shorter than the Kadet Senior wing… seems bunches heavier… and has about the same dihedral.

Wing is covered and complete... ready to decorate!

Covering the Fuselage…

… started with the chin-piece. After all of those wingtips, the gentle compound curves of the chin piece was a piece of cake… almost “fun!”

I painted-on clear fuel-proof dope around all of those blue edges of MonoKote in an attempt to seal the balsa inside its paint and plastic cocoon… an attempt to add longevity to what will be a much fuel-soaked piece of the model!

I brushed clear dope around the edges of the MonoKote.

Let’s go!

I stretched a piece of string around the fuselage and clamped it tight so as to define the blue and white color-break line. I positioned the blue covering against that line allowing about an 1/8″ to go past the string… and that 1/8″ will be covered by the white covering’s 1/8″ overlap… I hope..

String stretched tightly shows the color breaks.

MORE freakin’ COMPOUND CURVES!

… just keep working it… don’t take “No!” for an answer… keep workin’ it!

Wrestling with compound curves at the nose of my Sig Astro Hog..

It’s always tough to get an even “line” on those folded-over bits of covering. That covering is on top of the dope I had painted into the engine compartment. When all of the covering is in place, up there, I will paint on a layer of clear dope to seal the MonoKote edges.

Nice, enough, finished edges.     

NO MORE COMPOUND CURVES, today…

Time to stand back and enjoy the view.
… Hmmm; it must be 5-o’clock Somewhere, right?

(Yikes!… I used FLASH on my camera for this photo. That “water effect” is the glare of light reflecting off of all those white high-gloss wing bays!)

"Water effect" is light reflecting off of wing panels.

– –

– –

Update: September 19th, 2019…

Watch out... here it comes!

Just about finished!
Expect Maiden Flight on Sunday, Sept 22!

The MonoKote covering went on well.
I have added the white over the edge of the blue, all around… looking really good!

Fuselage covered! My Sig Astro Hog build.

Automotive Pinstripe!

I have had this maroon striping tape around for a couple of years… It looks really good in this application!

Automotive detail striping tape applied.

I covered the fin and rudder… and put them together with CA hinges.

Covered the vertical fin / rudder... installed the CA hinges... a no-brainer!

This plane is BIG!

I set it up, like this, to keep the CATS off of it, overnight.

The Sig Astro Hog IS large... !

The “Windex Method” for MonoKote-over-MonoKote… it worked!

I decorated the Fin/Rudder with Monokote-over-Monokote using the “Windex method”. My first few attempts were failures… but, maybe, my Windex was… old?… didn’t want to work. I bought a new spray-bottle of Comet Glass Cleaner “with Ammonia”… but that spray had no effect on the Monokote. I poured some “household ammonia with fresh lemon scent” into that Comet glass cleaner… and saw no improvement in performance with the MonoKote.

I went to the local Flying-J truck-stop and bought THEIR brand of glass cleaner: MAX-PRO “Glass Shine” with ammonia…

SUCCESS!

"MAX PRO GLASS SHINE" with Amonia has the "power" to react with the Monokote covering material. Better than Windex??

That MAX-PRO “Glass Shine” REALLY worked well with my MonoKote! I had done some searching through forums, online, and saw Windex guys leaving their application to dry for 5-hours… or two-weeks! MINE was tacky within about 15-minutes… maybe less… and in only a fat hour I was confident to trim-seal the edges and hot-iron the folds and round the corners. One of the secrets is to DRENCH the piece of MonoKote… and moisten the surface to be covered… and be in no hurry… give the glass cleaner plenty of time to soak-in and soften the MonoKote adhesive. Then I used the edge of a plastic credit card as a squeegee and worked all of the bubbles and wrinkles out of the piece. It does not go on like it has adhesive; you cannot follow a hinge-line or fold-over a corner… but just smooth it out on the flat surfaces and wait for it to harden-up so that you CAN do those things with your iron. A couple of times I saw a bit of dust trapped under the film as I squeegeed it… and, this method is so slow, that I was able to peel-up the film, remove the dust speck, and reapply the film. I MAY HAVE BEEN to anxious to “move on” with the project because, maybe I did not it let it set-up for long enough… a couple of times, I saw that some colored adhesive did squeeze-out from under the film as I sealed the edges with a hot iron. But… yesterday’s work still looks great, today… I think it worked!

Decorated the fin and then epoxied into place.

I used 6-minute epoxy to attach the fin to the fuselage… I first stripped-away the covering over the glue areas to insure a nice wood-to-wood attachment… it almost “dropped into place”. I stayed with it to keep it square until the epoxy set-up. … No problema!

I decorated the Fin and Rudder using the "Windex method."

I added the throttle linkage and installed the OS 65LA motor with a 12-7 APC prop. (So glad I hadn’t installed that “chin piece” before mounting the motor, no way could that have been done with the chin glued-in!!)

Watch out... here it comes!

“Windex method” used to decorate the Horiz Stabilizer

I used the "Windex method" to decorate the horiz. stabilizer.

The Tail Fairing saga…

The Sig Astro Hog kit includes some 1/2″ balsa with pieces printed upon it… I used a band-saw to cut them out. The trick is to stay outside the printed lines and then sand your way to the finished shape. The Tail Fairing sands-away to almost nothing left!

The puzzle with the tail fairing is “when to install it?” This model (from the olden days) was designed to be covered with silk-span and dope and so the builder could build the entire fuselage with the tail feathers in place… and then cover and paint the model. In these “modern days”, I am using MonoKote… and it was best to cover the tail-wings and the fin/rudder before installing them onto the fuselage. There was nothing I could do but add the fairings AFTER I had already covered the fuselage and installed the tail feathers… I shaped them and covered them with MonoKote… 6-minute epoxy with the covering cut away for wood-to-wood in the glue joint. So, they go on like kind of an afterthought, though I had been thinking about them for months! … It works OK… no real issue, after all. These fairings help to act as gussets to hold the fin securely.

The "Tail Fairing" gets shaped and sanded-away to almost nothing... and it is the gusset that holds the rudder onto the ship!

The tail fairing looks OK.

Tail Fairing created and epoxied into place.

Control Linkages!

This model is big… and the fuselage is cavernous! Since I had created that large cockpit-tub to hold my Astronaut, I could not install the traditional little servo tray… I had to move things around to make room for that tub… but… no problem… Plenty of room! … and look at that little 12-ounce fuel tank… almost room for TWO of ’em in there!

The fuselage is cavernous! ... My Sig Astro Hog build.

All but done! … !

I still need to decorate the top and bottom of the main wing… detail the cockpit area with headrest, and a rubber coaming around the lip of the cockpit, install the landing gear and wheels… install the elevator and rudder control horns… plenty still to do.

BALANCE will be easy…

… just gotta place the battery behind the wing… that OS 65LA is heavy! … and look how tiny that 5-cell NiMh battery looks… no problema!

Putting the battery right behind the wing for balance!

Maiden Flight scheduled: Sunday Sept 22nd!

Today is Thursday afternoon… and I plan to go for MAIDEN FLIGHT on SUNDAY! Initial indications are for OK weather… I figure all of my coverings, glues, paints, and etc. will be hardened-up and ready for that first flight.

See you out there on Sunday!

– –

IT’s Finished… my Astro-Hog is Finished!

Eric Reinhart poses with his brand-new Sig Astro-Hog!

… and it flies BEAUTIFULLY!

I designed the graphics on the main wing so as to be an abstract version of what’s going on with the tail-feathers… which I had done in a traditional pattern. With those red and blue deltas on the tail simply transferred to the main wing, I was envisioning a regular “circus plane” in my mind’s eye… and so I decided to go crazy and do a modern-art re-hash of those deltas as I decorated the main wing. I was thinking about some of those contest-grade graphics on the old Control-Line pattern planes.

Old control-liners helped to free my mind for these graphics!

I created the design in Photoshop on my computer… printed it out, and transferred my art onto that wing.

My brand new Sig Astro-Hog... lookin' good!

OMG… TWO MONTHS of Building the model…
…Then… On the VERY FIRST FLIGHT…

– – –

– – –

The new Astro-Hog model…

– – –

FLEW GREAT!

I set the model onto the “tarmac”, aligned with the center of the runway, gently pushed on the throttle and the Astro-Hog picked-up speed and lifted-off for a perfect Maiden Flight!… So smooth and so much power… flew well at high-speed and also flew well at minimum throttle… The Specs say the model should weigh between 7 and 7-1/2 pounds. I weighed my model this morning: 7pounds, two ounces… Perfecto!

The flight was gentle and beautiful… the model is right in the middle of my comfort-zone… very solid and predictable… and with that 65LA engine and a 12-7 APC prop, it will climb straight-up, as high as you want it to go! … and then nose down for a beautiful power-dive… safe and strong. Go back up… try a gentle stall, let the nose drop and add elevator and rudder for a tail-spin and then neutral on the sticks to pull out of the spin… get some horizontal speed… try a stall-turn… all too easy! … try an outside loop! Nice! … The landing was a “floater”… throttle to high-idle on the down-wind leg, get it over the runway, go to low idle and let it simply settle-in with a little flare, at the end, to keep the nose up … main gear touch first… then the nose gear… so nice! (The gentle landing got me a lot of applause from our peanut-gallery!) Fun! … and THAT was only the first of my three flights for the day.

Beautifuk first flight... so nice, my new Sig Astro-Hog!

Fuel-streaked wing and tail-feathers after first flight!

Fuel-streaked wing after first flight!

I got three flights on my Astro-hog on its first morning… EACH with a gentle, “main-gear first” landing.

Then I removed the wing and inspected the hardware and the battery location to be sure that all was still solid… no surprises… ready for NEXT time!

My new Sig Astro-Hog is a delight to fly… like a slow-flyin’ high-performance trainer. I am running an O.S. 65LA with an APC 12-7 prop… seems like the perfect combination… fun to fly!

I got three flights on my Astro-hog on its first morning.

THAT’s it! … My story is complete!… “Thanks for readin’!” and thanks for your comments and support… fun stuff! … I will be flying my Hog (my NEW favorite airplane) at the field… See you out there!

– –

9-27-19: AAhhhhh! Surgery required!
The internal landing gear mounting block broke!

After the ninth flight, I was cleaning-up and saw that the left landing gear strut was leaning back… inspection showed that there was no wood to keep it from rotating fore-and-aft. The large grooved piece of hardwood was firm… no broken ribs… so, when I got home, I decided to open a panel and take a look…

I opened a panel in the wing to see what I could of the landing gear mounting block.

I found that the hardwood block, holding the end of the gear-strut had split… the edges were still glued to the plane, but the piece of wood had split-away from the glue seams. I dabbed 6-minute epoxy all around the broken area and put that broken piece back in there… Not shown: I also added a brace under the block, large enough to hold the block together, better than new. I waited a fat hour for the 6-minute epoxy to harden and then re-drilled the 5/32 hole for the wire strut.

That hard-wood block had split!

I added a lip around the hole to support the panel using scrap balsa.

I added a lip all around the hole.

The panel dropped back into place. I used Gorilla yellow wood glue to attach the panel… and after dry, I gave it a light sanding to smooth the seams.

The panel dropped back into place.

After covering the patch with a patch of MonoKote… “The customer will never notice!”

The customer will never notice!

NOW I see that the decals are NOT Fuel-Proof!

Oh, man… I had been reluctant to USE the decals because I know that nitro-fuel is hard on ’em…. and I no longer have good ol’ Pactra “Fuel Proofer”… an easily brushed-on clear-coat. But… these Sig decals (stickers, actually) came with a slip of paper saying how great these decals are! … Fuel-proof and non-yellowing with age. Well, crap! The “adhesive” may be fuel-proof but the black ink on my decals is softened-up and can be wiped off! … I don’t know what to paint ’em with… Clear Krylon??

The black ink on my "fuel-proof" stickers is breaking-up!
The black ink on my “fuel-proof” stickers is breaking-up!

MORE news, later… maybe I will find SOMETHING! to paint ’em with.

Gerry Peters said “Just put clear tape over those decals.” … … so that’s what I did… I attempted to touch-up the black image with a Sharpie… but didn’t really make much of an improvement.

Tape over the decals:

Clear tape over the decals to "fuel-proof" the decals.

 

Update 10-22-19 Repair after damage…

I find the fuel tank is mounted too high and so, when full, the fuel dribbles into the motor’s crankcase causing hydro-lock when I try to start the engine. Recently the prop torqued-off during one of these events and stabbed a hole in the left wing! … I was ready to fly, so I made a “field repair”: I simply taped-over the hole, reinstalled the propeller and spinner, cleared the engine, fired it up and enjoyed the flight.

When I got home I was able to inspect the damage more closely… and, aside from a small dent/cut in the wood and that gash in the top MonoKote, it was a non-event.

I cut-away the damaged MonoKote and inspected the damage... almost NO damage.

“The customer will never notice…”

I cut a piece of MonoKote to cover the hole... Customer will never notice!

—- —-

I changed the servo-arm on my Ailerons so as to do away with the Aileron Differential… now I am using a straight arm for equal up and down aileron deflection.

A straight servo-arm gives my Astro-Hog equal up and down aileron movement.

 

6 thoughts on “Building my Sig Astro-Hog Kit”

  1. Eric, Thanks for another great, inspiring article. Would be fun to see a few more members give a build a try! Hand built increases anxiety for a maiden flight, but what a great feeling when she proves airworthy. Jon

  2. I had one on an OS FS70 four stroke, nicest flying plane I ever owned. Itried to rol it after take off and totalled it and the FS70. I have since acquired a new FS70 that I was using in a Goldberg Anniversary Cub, before lending it to my son to use in his first plane, A Sig Senior Kadet (great combo!) Anyway, I have a newer FS70, and a new Astrohog kit on the board. I have been limited in my flying by a stroke I suffered two years ago. Now I am only flying an electric glider, I don’t know the make or model, but I enjoy it. Can’t wait to fly the hog again. Great plane.

  3. I like your idea of making the chin piece removable! Great idea.

    Would you convert it to a tail dragger? Pros / cons? I’ll be starting my build here shortly. Not sure if i want tail dragger or not. Was thinking of adding the hardwood landing block to both placements on the wing so it can easily converted. Good or bad idea?

    As for the fuel tank should it be lowered to prevent it from hydro locking the engine when the tank is full?

    1. YOU are exactly right about that fuel tank! … I “followed instructions” instead of my instincts… and with the tank mounted right up, as high as it will go, as per instructions… it’s TOO high. It DOES hydro-lock, like, ALL the time! My model is built so that I break the fuel-line between tank and needle-valve to fill the tank… and I DO NOT connect them until I am ready to start the motor. And when I land, I switch-off the ON-OFF switch and disconnect the fuel line, right away.

      Tail dragger? … It WOULD be more classic, but a model standing on tricycle gear is so effortless on both take-off and landings that I opted for the trike. … I guess you COULD create a couple of more hardwood blocks and mount all four of them in the wing… add a tailwheel… interesting idea. … I have 37 flights on my model, now… and aside from that one little repair issue with the cracked landing gear mounting block (old wood, I think), I have had an easy time with ground handling and maneuverability. I am happy with the trike.

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