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SIG Four-Star 60 Build

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Old 03-02-2019, 12:38 PM
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VincentJ
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Default SIG Four-Star 60 Build





A new, clean sheet of drywall on my build table can only mean one thing...time for a new build project!

Selecting the plane that I wanted to build only required me to open my closet and select from among the many kits that I have stashed away over the years. As you can see by the photo, I selected a kit manufactured by Sig, the Four-Star 60. I actually bought this unopened kit from an auction my club had last summer. I'm almost embarrassed to say what I paid for this new unopened kit. The hammer dropped at 30 or 35 dollars!

Some of you may remember a few of my builds that I completed, such as the Sig Ryan ST-A, or the big Sig Morresey Bravo, Carl Golberg's Tiger 60, Sig Spacewalker, or my last build by Northeast Aerodynamics Sport-Air just to name a few. Each of these were fun and I hope informative for those following along. I hope to make some changes/improvements to this classic and I invite you to come along for the ride!

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Old 03-02-2019, 01:21 PM
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The wing ribs were neatly laser cut making the job of releasing the from their sheets an easy task. All were stacked with the exception of two W-5 ribs. These two ribs will not be needed as I am shortening each wing panel by one bay.


After all of the wing ribs were removed from their sheeting I was careful to draw an arrow on each rib indicating TOP. It is very easy to make an error and install a rib upside down as they are not fully symmetrical! There are five different wing ribs which are marked W1- W5, which is why I have five separated stacks. I made sure each rib was identical in size and shape by stacking them and sanding them as one ensuring uniformity...

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Old 03-04-2019, 10:53 AM
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Great to see another one of your builds on the board, I'll definitely be following along.

I'm already curious to see what those notches in the ribs are at each of the spar locations. The plans appear to call out "Laser cut 3/32" balsa spar web" so it must allow the shear webs to key into the ribs? No answer necessary now, I'm sure all will be made clear...
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Old 03-04-2019, 02:30 PM
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Your work space is inspiring. I would post a pic of mine but people would likely start calling FEMA.

I've built 2 Sig kits over the last year. I loved em so much, I've been buying and stocking up for future fun just in case they ever cease production.
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Old 03-05-2019, 04:47 AM
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Originally Posted by TCampbell View Post
Great to see another one of your builds on the board, I'll definitely be following along.

I'm already curious to see what those notches in the ribs are at each of the spar locations. The plans appear to call out "Laser cut 3/32" balsa spar web" so it must allow the shear webs to key into the ribs? No answer necessary now, I'm sure all will be made clear...
Glad to have you follow along Tim, I was beginning to think no one was interested in this build and was contemplating pulling the plug. The notches that you spotted are for the shear webs which is one long piece instead of them being separate. This type of construction allows the builder to almost fully assemble the wing without glue by interlocking all of the parts together, then later flooding each joint with CA. While this is a neat feature for novice builders, I can't say that I'm fond of this type of construction as I don't use CA to build with. It has been a pain for me to use the glue of my building choice, Titebond II glue in all the joints! I'll follow this up with a pic or two showing this interlocking feature.

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Old 03-05-2019, 04:50 AM
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Originally Posted by BalsaGhost View Post
Your work space is inspiring. I would post a pic of mine but people would likely start calling FEMA.

I've built 2 Sig kits over the last year. I loved em so much, I've been buying and stocking up for future fun just in case they ever cease production.
Thanks BalsaGhost. My work space is rather small so I have to keep things neat and organized!
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Old 03-05-2019, 12:40 PM
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Originally Posted by VincentJ View Post
Thanks BalsaGhost. My work space is rather small so I have to keep things neat and organized!
Absolutely love the fact that as part of your building bench, you included cubby holes to keep sheet balsa and stick flat. I need to consider something like that!
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Old 03-05-2019, 04:08 PM
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Originally Posted by ExtraCGScott View Post
Absolutely love the fact that as part of your building bench, you included cubby holes to keep sheet balsa and stick flat. I need to consider something like that!
Welcome ExtraCGScott. I designed that build table about two years ago and in my design was a Balsa storage bin which I just recently completed. I have been procrastinating to build it because I knew it would be a pain (and it was). It makes my wood storage very efficient and I now know what I have in stock and what I need to order to be more efficient while building.

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Old 03-05-2019, 04:19 PM
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I'm having difficulty uploading pictures that I took this evening. I will try later on and see if it works...
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Old 03-05-2019, 04:20 PM
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Originally Posted by VincentJ View Post



Welcome ExtraCGScott. I designed that build table about two years ago and in my design was a Balsa storage bin which I just recently completed. I have been procrastinating to build it because I knew it would be a pain (and it was). It makes my wood storage very efficient and I now know what I have in stock and what I need to order to be more efficient.
Excellent idea - thinking about how to retrofit something similar under my table. I currently have my balsa randomly scattered throughout and never remember what I need or have. Is that an air filter, if so.... what is it for?
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Old 03-05-2019, 04:31 PM
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I started on the left wing panel. I am not installing the diagonal bracing shown on plans. I will be instead sheeting the top and bottom of the leading edge using 1/16" Balsa which will give it plenty of strength. The sheeting will terminate at the spar.



Notice that I am in no hurry to trim off the stock that overhangs the first rib. It will get removed once the entire wing is completed. I substituted the leading edge stock with 3/8" square stock. The additional thickness from the supplied wood is perfect for me to butt the 1/16" sheeting against it and be flush. The trailing edge stock was also replaced with thicker sheeting to accommodate 1/16" rib caps that I am adding which will terminate flush at the trailing edge.



I substituted the paper servo tube as called for in the plans for a much more stout rocket tube that fits perfectly in the rib openings. The rocket tubes will also give additional strength to the wing ribs...the weight penalty is negligible. You may have also noticed that I have added two lightening holes in each of the wing ribs, this along with the elimination of the diagonal bracing will help offset the additional weight of the sheeting that I will be adding.

Note:The first rib is glued into place at a slight angle giving the wing its dihedral when mated to the other wing panel. The stock dihedral for this plane is 2 degrees (per panel) which I have re-adjusted to 1 degree.




Rocket tubes come in a variety of different diameters.

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Old 03-05-2019, 05:03 PM
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That's a Jet air filter that I also mounted under my build table. I have a wireless remote for it that I keep next to me. It does a great job of keeping the dust out of my lungs when I am sanding.
https://www.jettools.com/us/en/p/afs...ontrol/708620B

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Old 03-05-2019, 07:54 PM
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TnT Landing gear also offers the wire tubes in 36" lengths @ 6 for $6.00. I buy a bunch of them at a time when I order. I find them quite handy for other purposes also.

I enjoy your kit build reviews!
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Old 03-06-2019, 01:38 AM
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Thanks Truckracer and welcome back! I'll be checking in with TNT soon, thanks for the tip, sometimes I need tubes that are longer than the rocket tubes...

On another note, I never mentioned what engine I plan on using for this project. After checking the measurements, I will be using a DLE-20RA which should fit nicely and have more than enough power. I'll be picking it up from my not so near hobby store tomorrow. I also purchased a fiberglass cowl and wheel pants from Fiberglass Specialties. Enclosing the engine with a proper cowl will improve the looks to the front of this plane. Both engine and cowl will require the firewall to be relocated and adequately braced. Exciting things to come!!!

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Old 03-06-2019, 08:58 AM
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Dang, that will be a rocket ship with a DLE20! A 20 pulls a Four Star 120 along pretty well with close to unlimited vertical. Are you going to use a custom LG for prop clearance? Sounds like fun. I always thought the Four Star 60 was the best of the series.
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Old 03-06-2019, 10:42 AM
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Originally Posted by Truckracer View Post
Dang, that will be a rocket ship with a DLE20! A 20 pulls a Four Star 120 along pretty well with close to unlimited vertical. Are you going to use a custom LG for prop clearance? Sounds like fun. I always thought the Four Star 60 was the best of the series.
Truckracer, I haven't done anything stupid in a while so why not...lol
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Old 03-07-2019, 03:50 PM
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This DLE-20RA should get the job done...
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Old 03-08-2019, 05:03 PM
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I made six hinge blocks for the 1/8" Robart steel pin hinge points that I am using, these will make sure that each hinge point is locked into the LE. Each block is glued into its proper location.



The six hinge blocks are spaced roughly 5-1/2" apart. This should be more than adequate.

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Old 03-10-2019, 07:46 AM
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You can see in this photo the outer wing bay has been eliminated as well as all the diagonal bracing.



The left wing is ready to be partially sheeted using 1/16" stock.



I chose to plank the first four bays leaving gaps between the planking to help minimize weight.



I could have just cut four ribs larger and swapped them out for what was supplied eliminating the planking...your call.



The trailing edge came out straight and true.. Inboard #1 rib which is set at 1 degree for the wing's dihedral, still needs to be sanded flush. It's also easy to see here how the TE sheet stock (1/8") is thicker than the planking which is 3/32". The difference will allow the final sheeting to be near flush with the TE.


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Old 03-10-2019, 02:58 PM
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Top of the left wing has been sheeted. Cap strips were also glued over each rib.




You may be wondering why I sheeted the one center bay. This is the bay where the aileron servo will be attached. Sheeting the top and bottom of the bay will eliminate any flexing of the ribs by the action of the servo. The bottom will have a 3/32" Birch plywood removable hatch. A custom aluminum servo bracket will hold the servo to the hatch cover...



Close-up of the rib cap strip detail.

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Old 03-12-2019, 02:53 PM
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Even though the bottom of the left wing has yet to be sheeted, I've gone as far as I can on it. Construction of the right wing panel will now begin. Once the right wing panel is at the same stage as its opposite twin, the two panels will be permanently joined together. You may wonder why not fully sheet each wing panel then join them? By having access to the unsheeted bottom center section of the wing panels, I can better control the epoxy joint on the center plywood wing joiner at the wings center. Now you know...

I'll try not to duplicate what I've already shown you on the left wing panel, but instead try and highlight other details not covered...





The process starts by epoxying two 1/4"x 1/2" balsa sticks together. Once cured, it will become one of two wing spars.



The key to getting a nice and straight spar is to make sure that they are clamped to something that is straight and flat. (In this case I used aluminum square stock and the cast iron base of my disc sander.)



Here's a builders tip: Clamp everything dry first, that way you won't have any surprises once you apply the epoxy. Maybe the set-up that you thought would work won't, leaving you to quickly come up with a better solution rushing against the epoxy curing time. Better to find out dry first!

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Old 03-13-2019, 01:19 PM
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My fiberglass cowl and wheel pants arrived today! Great timing...
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Old 03-14-2019, 03:30 PM
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This way of building is conducive to using CA. Since I don't use CA this type of construction is a real PITA...




All the pieces laid out.




With the bottom main spar pinned into position, the one piece shear web is placed on top. (This is the first time I've seen the grain in the shear webbing running in that direction. I always orientate the grain vertically for strength.)




All of the ribs simply interlock together. A very easy way to construct a wing if it's your first build. (I apologize how my hands look, working on cars for a living make them look that way, they really are clean...)




Double bonus building tip for tonight! Tip #1- The 1/4" x 1/4" square stock shown is the bottom rear wing spar (no that's not the tip). Notice how I've pushed the spar tight against the aluminum square tubing. This is a good way to ensure that the spar is pinned straight over the plans. Don't trust the lines on your plans to be straight and true, especially if your plans don't lay flat as is most of the case with folded plans.




Tip #2-You may think that your balsa square stock is dimensionally equal. It probably isn't, so before you pin your stock down find which side fits tighter in the notch of the rib. You will see and feel the difference.

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Old 03-15-2019, 07:57 AM
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Time to install the wing's leading edge. Here's how I do it.




Six hinge blocks which need to be shaped then glued into the TE.



Installing the wing's LE is a snap if you have a length of angle aluminum and some clamps.



The angle aluminum keeps the LE straight and prevents the softer balsa from getting crushed while clamping.



A close-up view.

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Old 03-15-2019, 11:52 AM
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That is one solid spar. I have also installed shear webs with the grain vertical. I wonder how much of a strength difference there really is...
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