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Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

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Old 09-06-2011, 09:33 AM
  #26
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Sounds like you enjoy scale-like flight with old bipe designs, as I do. That Saito will probably pull your plane best with a 12x4, or maybe it won't matter much and either prop would do. I always go with the biggest props I can run on those old bipes. It will probably give you enough power without a lot to spare, which is pretty much what the original had. It topped out at 95 mph, climbed at 450 ft/min, and needed over 400 feet to get off the ground...no ball of fire. So at 1/6 scale, if it takes a minute to climb to 75 feet it will be about right!

The Saito 40a is very light, as I'm sure you know, so all the stuff about keeping the tail light and weights forward is really important. Keep it coming...this will be nice!

Jim
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Old 09-06-2011, 07:47 PM
  #27
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Chuck, I took your comments about the cabane attachments, took another look at the interplane strut mounts with their tripled ribs, and beefed up the plywood "hardpoints" a bit. Where the blind nuts will be anchored the 1/16" plywood was doubled with either very hard 3/32" balsa or the dreaded liteply. Then the ribs at those bays were doubled with 3/32" balsa. I recently finished a Sig Astro Hog and there's so much wood left over from that kit! While the tail of this airplane needs lightness added the wings can surely bear a little more lumber.
The first two photos look back at the rear spar and rear hardpoints, the third photo looks forward at the main spar with shear web and doubled ribs and hardpoint.
Also today the leading edge balsa sheet was spliced and the inner leading edge was sanded down flush with the ribs to accept the leading edge sheet. After measuring my Saito and its mount and marking the plan for how far back the firewall will need to be moved I found I'd have 3-7/8" for the fuel tank length. Great Planes offers an 8 oz. tank at 3-5/8" so that should work.
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Old 09-07-2011, 06:22 PM
  #28
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

This shows the top wing leading edge being glued on with Titebond. The monster size clamps are just what I've got. One level is holding the wing down flat while the other is pressing the edge onto the inner leading edge.
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Old 09-08-2011, 05:12 AM
  #29
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

I have clamps just like that! I love 'em! Nice work! You'll be flying that Tommy before you know it!
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Old 09-08-2011, 06:46 AM
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Now that will be a straight wing!
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Old 09-10-2011, 08:08 PM
  #31
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

With the wings and ailerons built I'm turning to the tail surfaces. As per instructions, the elevators come first. I like this overlapped construction, 3/32 x 1/2" leading edge and 3/32 x 3/8" outline. You build around one direction on the first layer then start at the other end and build back again on the top layer. It's a lot of pieces and glue but does seem like it will be strong. I'm sure bent and laminated edges would be lighter and more scale but I find them a pain.
So the first photos show the overlapped construction with pieces running wild to be trimmed to shape later.
The last photos show the hinge slotting method which I haven't seen before either. It's fully described in the instructions. I've made a little sanding block 5/8" wide for the kit's Dubro pinned plastic hinges. I'm using popsicle sticks to limit the sanding depth and sanding slots at the plan locations on the elevator leading edges. After cutting the top leading edge pieces I marked them and sanded the slots in them as well. The resulting slots after laminating the leading edges fit the hinges perfectly and were very easy to make. It would be difficult to slot later because you'd have the CA glue hardening the balsa right where you'd need the slot.
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Old 09-11-2011, 03:39 PM
  #32
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

The stabilizer and elevators hinged and rough sanded. This is some pretty light material, very soft. Once again the choice of material seems good. I probably spent 3 hours on them.
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Old 09-12-2011, 07:46 AM
  #33
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

On the vertical fin and rudder BUSA has changed the construction no doubt to allow them to die-cut the parts in duplicate. You are to simply laminate each segment of the rudder outline and then butt-join them. You are to use 3/16" sticks for the hinged upright pieces. I decided to continue the sanded hinge groove method by laminating 3/32" wood for the uprights. I'm using BUSA's pieces for the first side of the rudder outline which BTW are cut perfectly. I'm then gluing pieces of the die-cut sheet for the second side with staggered joints and the grain running at different angles from the first side pieces. Then I'll Dremel the outline to shape.
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Old 09-12-2011, 09:49 AM
  #34
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

OK, vertical tail surfaces are shaped and hinged. They feel strong and light. The large filler block at the bottom of the fin got cut away along the bottom where it will be buried.
With the flying surfaces built let's start on the fuselage!
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Old 09-12-2011, 06:58 PM
  #35
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

The fuselage side frames are produced in the same manner as the tail surfaces. 3/32 x 1/4" balsa is used to make an outline. You then laminate another layer coming back in the opposite direction so the joints overlap. 3/16" square balsa is used for the uprights and 3/32 x 3/16" for the diagonals. The front end is laminated 3/32" balsa sheet from die-cut parts. The parts fit was once again a delight. The frame feels stiff and reasonably strong.
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Old 09-15-2011, 03:13 PM
  #36
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Yesterday the second fuselage side was built. The two were pinned together and the edges sanded to match. Liteply doublers were laminated to the insides with wood glue. Center lines were drawn on the firewall, tank compartment floor, former F2 at the wing leading edge, and the crutch piece at the top of the compartment. Today the fuse sides, crutch, and floor were marked for the firewall location with its thrust angles of 1 degree right and 2 degrees down thrust. F2 was then glued perpendicular to the right fuselage side. This assembly was glued to the crutch. The left side was then wood-glued to the crutch and clamped and weighted as shown.
So far it's going together parallel, square, and true. I would install blind nuts to the firewall before gluing it in, but am deciding I'd rather have the fuselage built and cowl installed to better see the how the engine should best be located. It's going to be laid on its side to the right and angled downward somewhat to exit the exhaust out the scale opening in the cowl's underside. Those rotaries must have slung a lot of oil, somewhat like our engines!
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Old 09-15-2011, 04:04 PM
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Great progress, and good work keeping that fuselage framework square. Definitely one of the hard parts.

Jim
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Old 09-16-2011, 03:58 AM
  #38
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

I am enjoying following your build. Keep up the good work!

Bruce
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Old 09-16-2011, 09:59 AM
  #39
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

The firewall is now laid out for the engine mount bolts and 30-minute epoxied in place. It was installed offset for the thrust angles despite BUSA's instructions to put it in square. I'm placing the engine mount 1/16" to the left so hopefully the prop shaft will be centered on the cowl. The landing gear mounting blocks were sanded a little thinner as an adjustment to how the fuselage is actually built. They were also lengthened 1/16" with some birch ply to fit better. They'll get the epoxy as well. The fuel tank compartment and fuselage front are getting a coat of Miniwax polyurethane as fuel proofing. I'll get blind nuts installed for the engine mount bolts before gluing in the tank compartment floor.

Thanks for your responses! Comments, suggestions, corrections, etc. are encouraged.

I wonder if the tail servos would fit in front of the firewall?... BUSA shows a box built above the engine mount for the radio battery pack.
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Old 09-17-2011, 11:04 AM
  #40
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

The critical tail join! A piece of laminate shelf with its centerline marked is being used as a building board. The fuselage is upside down on the board with its centerlines on the board line. Blocks are hot-glued to secure the front end which is nicely square thanks to BUSA's excellent die-cutting. A ten-pound weight holds the front securely on the board. More blocks are hot-glued at the tail and various shims placed to close the gap between the fuselage sides. A large plastic drafting triangle confirms the tail join is vertical with its centerline on the board line. The sides met with about 1/8" difference in height. They are held even in height and pinned together while a bit a thin CA tacks the sides together. Since my sanded joining angles aren't perfect some shims will be glued in with medium CA.
This setup will hold things in alignment while the 1/4" x 3/16" cross pieces are installed between the side frames. It was a very quick and easy technique.


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Old 09-17-2011, 12:07 PM
  #41
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Looking good!
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Old 09-17-2011, 02:54 PM
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Of course, the cross braces aren't lining up on center and the upper and lower longerons aren't staying aligned plumb. Various diagonal braces are being installed despite none being in the plans. Either the tail end is supposed to magically align itself or it'll look wombly. These are light weight 3/32 stock braces so I hope not to add too much weight back here.
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Old 09-17-2011, 04:16 PM
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

The wing bolt blocks and landing gear blocks wood-glued in.
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Old 09-19-2011, 10:15 AM
  #44
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Following your build closely as this will be my next build. Good work
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Old 09-19-2011, 06:32 PM
  #45
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Well, a bit of a setback today. The fuselage with lower wing attached slipped out of my hand and hit the concrete floor square on the nose. All the cross pieces broke out of the tail section. I thought maybe the Great Planes thin foam safe CA was to blame, but a very thin bit of the balsa longeron broke out at each joint: the wood failed, not the glue. Anyway, drilling the rest of the wing bolt holes will have to wait until the damage is fixed.
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Old 09-20-2011, 08:51 AM
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Bummer. But it does happen to all of us.
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Old 09-20-2011, 12:50 PM
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

With the tail section rebuilt the wing bolts were installed. 1/32" plywood squares were inlaid at each bolt head location on the bottom of the bottom wing. This was my alteration to provide a tougher surface than the soft balsa sheet. 3/16" basswood strips run across the fuselage wing saddle. These are drilled and tapped for the four #10-24 nylon wing bolts. I'm showing pictures of the bottom wing in each side of the saddle to show the perfect fit. Neither the wing nor the wing saddle has been sanded or adjusted, this is how nicely the parts fit.
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Old 09-23-2011, 07:25 AM
  #48
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

BUSA instructs you to solder the landing gear together near the end of construction but I wanted to use the fuselage while it still has a flat top. The gear wire parts were installed in the gear mount blocks with the nylon straps and wood screws. They were bound together with copper electrical wire. Plumbers' silver bearing solder was used. Paper towel was pinned to the gear wires to catch the running flux. To simulate the cross bracing cables, 1.5mm music wire was added. My plan is to simply run it up into holes drilled through the front gear mounting block and allow the wires to run into the space in front of the firewall, sliding in an out as the gear flexes.
Thanks to pioneerflightmuseum.org for the photo of the full-scale landing gear.

The rear fuselage bottom was completed with seven stringers of varying thickness to provide the rounded contour. This was easy and looks great. The tail skid mounting plate and reinforcement was installed. The 1/8" music wire tail skid seems like a boat anchor on that tail, I'm going to try 3/32.

Tommy's really taking shape now!
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Old 09-23-2011, 07:32 AM
  #49
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Yes, really lookin' good so far!
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Old 09-23-2011, 08:59 AM
  #50
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Default RE: Balsa USA 1/6 Scale Thomas-Morse S-4C Scout Build Thread

Glad you got the fuse repaired so fast! All looks good! Sometimes the stick structures are a little 'wimpy' so I tend to add balsa triangles inside each 'former' station. This really solidifies the structure for minimal weight gain and a extra time.
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