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Sep 26, 2015, 12:45 PM
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Thread OP
Build Log

This winter's build: the Sig Four Star 40

So after last winter's success with a CG Eagle2, I am going to do another one this winter. I probably won't be ready to fly it experience wise by the start of the next season, however. But hopefully once I am comfortable on the Eagle2 the transition to this low wing sport model will be easier.

So I did check around and found 2 or 3 build threads of the "4*40" as I often see it referred to, and have taken some ideas from them. Most seem like easy modifications, but one, running dual servos for ailerons seems pretty advanced so hopefully some of you wiser builders out there can comment to that effect. The other stuff is all bulking up weak points like the wing saddle and the landing gear mount etc, easy enough.

Alas no action in this post, the plans are still flattening out, but hopefully soon I will start framing up the wings!
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Sep 27, 2015, 11:05 PM
Registered User
I built the 4*40 as my first build a few years ago, and like most beginners, I built it heavy (and you knew it when it flew). I finally sold it this year, and after a few flights the new buyer finally crashed it (no loss). My advice is to build it to plans, and not try to make it crash proof. John
Sep 28, 2015, 10:37 AM
ARFs Are Me
TomCrump's Avatar
I usually don't recommend modifications to low time builders. I would suggest the dual aileron servos, though. It's an easy project.
Sep 28, 2015, 10:41 AM
ARFs Are Me
TomCrump's Avatar
Here are a few pics of an installation that would be similar to yours.
Last edited by TomCrump; Sep 28, 2015 at 01:53 PM.
Sep 28, 2015, 12:55 PM
AMA 34191
Vulgar Vulture's Avatar
I built mine one wing panel shorter (on both sides of course) so it didn't float so much on landing. Finished Wingspan is 53". I would use two servos for the ailerons.

Some will say you need to re-enforce the Landing Gear mounts but I didn't and it's more than strong enough. A coating of thinned down 5 minute epoxy on all the fuselage wing and engine mount areas is all you need.

If you're building this for electric then build in a top hatch for radio/battery access instead of using the bottom of the fuselage.

Good luck!
Sep 28, 2015, 01:28 PM
Registered User
I built mine some years ago (also the Mid Star 40) per the kit directions and it was a very enjoyable RC aircraft. Put 5 gallons of fuel through an OS .45 FSR and sold the plane to another RCer who continued to have a good time with it. One aileron servo was plenty and I kept the wing length stock. A great flying model that's well worth the time to build. Have fun with your build!

Soft landings,

Sep 28, 2015, 03:37 PM
Registered User
Thread OP
@ TomCrump: Excellent thanks for the photos, seems straight forward enough.

@ Vulgar Vulture: Currently the plan is to drop in a O.S. 55AX

Thanks everyone for sharing your experiences with this kit!
Sep 28, 2015, 08:00 PM
Registered User
I put flaps, lights, retracts and a 'V'-tail on mine! When the gear extends the landing lights come on. My third one had a 'V'-tail, LE slots in front of ailerons' span, statically balanced barn door ailerons, reinforced LG plate and a Supre Tigre 0.61. My second one had built up tail feathers and a 'two hole' open cockpit arrangement. My first was stock but I did reinforce the LG plate. We had a field full of crawdad holes and my skills were a little lackluster back then!

I have an easy solution for the tail wheel steering using 'V'-tail option and it doesn't require an extra servo!

I guess you can tell I like this airplane! I'm a 'scale' guy, too so you know this must be a great airplane!
Sep 29, 2015, 03:12 PM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
The only recommendations I'd make is shorten each wing by one bay and add a top hatch. I used a E-Flite Power 46 on a 4S5000 with an APC 12x8. The rest of the airplane was built stock.

You'll love it as others have said....

Latest blog entry: RC Throw Gauge
Sep 30, 2015, 02:51 PM
umpf umpf
basser's Avatar
I finished this build about 2 months ago.
I added another firewall further out towards the nose to accept the electric motor. I also added some right thrust to counter the extra torque of bigger props and electric motor. I kept the original down thrust.
I added a battery hatch for lipo access.
I added 2 aileron servos.

The motor is a Suppo power 32 equivalent. The ESC is a Turnigy Plush 60 Amp. Turning a APC 12x8 prop. The lipo is a 4s 3000. I get just over 5 minute flight times.

I'm using a Dubro Super Gear landing gear to get more ground clearance. FYI the landing gear for the Sig Kadet LT-25 kit is almost the exact same dimensions but 1 inch taller. This would be a good replacement for a taller gear. You can get them from SIG directly for around 12 dollars I think. I also used a 60 size dubro tail wheel gear and a bigger wheel for more ground clearance. This also helped offset the taller main gear.

The included pushrods work ok but they slightly change length with temperature. So Im always changing my trims as the day and temp progresses thru the day. Using a different pushrod would probably help this issue.

the plane weighs 3.8 pounds without the lipo. I think ita around 4.2 pounds flight ready. The lipo is placed almost up against the original firewall. So I built my hatch a little too long.
I did add length to the elevator and the rudder. This made the plane a little more tail heavy so I needed to place battery more to the nose. I think the added length to the elevator and rudder was not really needed. Its flying well with conservative flight control surface throws.
I think a power 46 size motor would be overkill and add extra weight. My plane flys with a light feel. It kinda reminds me a foamy plane but with no flexing airframe.

The servos are hitecs hs-225. I mounted the servos in the fuse as far rear ward as I could in the radio gear cavity. I tried to get as much weight to the rear of the plane as a could to off set the weight of the lipo. The aileron servo mounts are built out of hard wood. They are attached to a wing rib. I did not reinforce the wing rib. probably should have. But the forward servo rail is butted up against the wing spar. so there is some reinforcement strength. It all seemed plenty strong after they were built. Its been problem free so far. I drilled holes the ribs for the servo wires before I started the wing build.( see pic below)
Last edited by basser; Sep 30, 2015 at 07:11 PM.
Oct 03, 2015, 09:50 AM
Master Procrastinator
Tango Juliet's Avatar
As suggested, a few simple to do mods make this an even better airplane. Some years ago I had purchased the ARF version - I lacked serious building time, but I had flying time available. I shortened the wingspan by one rib bay on each panel, made new Rudder and Elevators with additional area for more authority, and I don't recall if I replaced the landing gear or if I just painted it white to better match the overall color scheme. It was a great little flyer. I lost it while doing a racetrack circuit with a club member (flying a US40) and I yawed up into him during a turn. Took us both out, but it was fun while it lasted.
Oct 03, 2015, 08:35 PM
Registered User
Way to go guys, now you have wanting to build another 4* 40 this winter. Shame on you. John
Last edited by jbrooks01; Oct 03, 2015 at 08:59 PM.
Oct 20, 2015, 09:44 AM
Registered User
Thread OP
So hey all you guys that have built this kit before, I have a question before I get started. The plans are one sheet, with 1/3rd of one of the wings like below the main part of the wing on the plans. In the instructions it talks about lining up some arrows to make the wing whole, I just cant believe they simply "infer" that you're to cut that portion of the wing out of the plans with scissors or something. I just thought that was odd, but don't want to maim my plan sheet if in fact I am interpreting this incorrectly.
Oct 20, 2015, 10:38 AM
Registered User
That's what you are to do but it is easy enough to build that wing without doing that. Just pencil mark the spars where ribs go.
Last edited by ARUP; Oct 20, 2015 at 11:00 AM.
Oct 24, 2015, 01:42 PM
Registered User
Thread OP
Good idea ARUP thanks!

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