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-   -   Sig XA 41 Sbach 300 observations... (https://www.wattflyer.com/forums/showthread.php?t=73350)

LSP972 03-16-2014 02:44 PM

Sig XA 41 Sbach 300 observations...
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I decided to do this when I was almost finished with the model… so what follows might appear to be disjointed and hap-hazard.

I will be making a series of posts, to accommodate the photographs, so I ask that you hold your questions until I post the last "installment"; otherwise, your query might get lost in the rubble. If you simply cannot wait, please PM me.

First some background. Bear with me, as I feel this is necessary to "explain" a few things that cropped up.

A good friend, who is rather high up the food chain in this industry, told me that Pacific Rim-built ARFs have morphed into a sort of hierarchy. The very best ones come from a certain province in China; and Sig ARFs once were made here.

Farther down the food chain, as it were, are the second-tier Chinese builders, and the Vietnamese factories. Here is where this ARF is produced, at the SeaGull facility. Why? Economics, I suspect. Sig has gone through a LOT of changes over the past few years.

Anyway, I was quite surprised to see the "Made in Vietnam" sticker on the box, and was NOT surprised that this kit is not as… "crisp", I suppose, is the word I'm looking for… as the earlier Sig ARFs, which I had several of.

That said… the overall quality of the kit is excellent, and actually a bit better than I expected at this price point. The fit of the critical parts was SUPERLATIVE; the hardware was adequate (I used everything except the supplied pushrods and the 4-40 motor mount bolts & blind nuts) and the covering job is primo. More on that last in a moment.

I haven't flown it yet; just finished her yesterday, then realized I had a bit more work to do (installing a separate receiver pack; more on that later, as well). So these posts will be confined to actually assembling the model and getting it set up. Once I actually get her in the air, I'll comment on that.

Here she is:

LSP972 03-16-2014 03:01 PM

First off, get out your iron. Snugging the covering on a model that was covered halfway around the world, and subjected to varying temperature/humidity conditions on its journey to you, is a smart thing to do. This model is covered in a combination of UltraCote and some sort of vinyl film; the latter complicates matters.

Be VERY careful with heat around this stuff. It won't take the same levels of heat as the U-Cote, and will simply melt. If you don't have one installed, the first thing I would do is get a "hot sock" for your iron. You'll have to dial up the heat a bit over what you're accustomed do, but it will act as sort of a buffer when working around that vinyl. All the black and white psychedelic checkerboard patterns on the airplane are of this vinyl.

U-Cote shrinks nicely at about 350 degrees on my Coverite iron. That's too much for the vinyl; I had to dial back to 300 degrees and be VERY fleeting with keeping the iron in close proximity to the vinyl.

That's the bad news; the good news is, the initial covering job done in Hanoi or wherever was exemplary; I had very few bubbles or wrinkles to deal with. So you basically iron down the seams with high heat, then go back and make sure the film is evenly shrunk… otherwise, after sitting in the sun for a few hours your model can (and usually will) look like a prune.

The covering job was so good out of the box, I was mightily tempted to skip this step. But I didn't.

Don't forget to open up a ventilation hole in the bottom of the fuselage, behind the wings. This isn't covered in the manual. Speaking of which, it is your typical excellent instruction book from Sig. I guess they just forgot about this step.


LSP972 03-16-2014 03:32 PM

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I "build" from the front rearward. Its an old habit from glow/gasoline power days, where getting the cowl and throttle linkage right was sometimes a flaming PITA, and much easier accomplished with no gear or stabilizers in place, as you wrestled about with the fuselage.

The kit comes with 4-40 engine mounting hardware. I'm sure that's perfectly adequate, but keeping in mind early reports of a recurrent tail-heavy condition, I used 6-32 bolts and blind nuts. That didn't help much, if at all, as it turns out.

However, this model does come out tail heavy… quite tail heavy, in fact. One respondent indicated he needed 50 grams of nose weight on the motor box. I believe he was using a MotroFly motor. I used the recommended E-Flite Power 32, with E-Flite's 60A Pro ESC, and I needed 110 grams (about three ounces) on the motor box to balance the model at 3" back from the LE.

The way Sig chose to design the firewall on this model is novel; to me, anyway. In fact, the parts (two main side formers, bottom former) of the motor box are, individually, rather flimsy. They all lock together when the firewall is glued in. The kit provides a small piece of triangle stock to reinforce the inside corners of the firewall/motor box area. I used much larger size triangle stock for this.

Doing so does two things; it provides for a stronger joint, and the bottom piece provides a stand-off to keep the battery away from the motor mount blind nuts. Be sure your bolts do NOT protrude past the rear surface of the blind nuts. A crash or other frontal impact could impale the end of your battery on protruding bolts…bad juju.

LSP972 03-16-2014 03:42 PM

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Continuing with the front end…

The cowl covers the front end of the battery compartment rather thoroughly. IOW, unless you have baby fingers or a pair of hemostats, you ain't getting your mitts up in there when the cowl is in place.

I'm specifically referring to strapping down the battery before flight. After some thought, I decided to fabricate a "fixed" front strap, of sorts… one that I didn't need to deal with, yet would prevent any lateral movement of the pack in flight. I used velcro and a standard battery strap at the back of the stick (where I can get my hands into) to actually secure the battery pack.

LSP972 03-16-2014 03:48 PM

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And we finish off the front end with the ESC…

Weeeelll, not quite. I'll add photos of the separate receiver battery pack (which is going on the opposite side of the motor box) when I git'er'dun.

LSP972 03-16-2014 05:16 PM

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Separate receiver battery and switch harness mounted. These ESM harnesses are direct copies of the set-up JR first came out with a dozen or so years ago. The idea of a self-contained switch and charge jack was one of those "Why didn't _I_ think of that???" moments.

These ESM units are the best copies with Futaba plugs I've yet to run across. If you run gas/glow models or otherwise need a separate system to power a receiver, check them out.

This was easy to do and totally without any drama. Should help with lateral balance, too.


LSP972 03-16-2014 05:35 PM

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Moving on… the wings are straightforward; no surprises there. As mentioned earlier, I did elect not to use the supplied aileron pushrods. The half-a-Z-bend-with-a-plastic-keeper method works well enough; I just do not like it. Plus, the supplied wire is typical Pacific Rim stock; bends too easily, yet brittle.

So I made up pushrods from 2-56 all-thread, Sullivan and Great Planes clevises, and heat shrink tubing.

Also, the aileron gap was sufficient to cause me to seal it with clear U-Cote. This is a totally subjective thing, up to the builder/flyer. All I know is, I have never had a control surface flutter that I had done this to. That's good enough for me.


LSP972 03-16-2014 05:41 PM

The canopy/hatch assembly was cause for a bit of concern, at first, due to the mojo magnets installed to retain it. Without the canopy glued in place, the hatch frame is rather flimsy. The magnets didn't want to let go, and I was worried about having to grasp the assembly hard enough to break something.

Gluing on the canopy firms it right up, and the back edge of the canopy provides a bit of stand-off to lessen the gorilla pull of those magnets. Mine seems secure enough; we'll find out when I fly it.


LSP972 03-16-2014 06:01 PM

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The empennage/tail feathers is where a lot of potentially good flying airplanes are condemned to the junk pile of mediocrity. Many times, this is caused by poor fit back there, due to poor design or fabrication, and exacerbated by someone not versed in building techniques and/or fixing alignment problems.

I am happy to say that the fit of the tail feathers on this airplane is, without doubt, the best I have yet to come across in almost 30 years of modeling. The horizontal-stabilizer-to-fuselage joint is simply perfect; I re-checked and re-measured a half-dozen times, because I couldn't believe it. Finally I just glued the sucker. The vertical fin piece doesn't fit quite as well, but its all cosmetic; the alignment is perfect.

Control surfaces are straightforward. The joined elevator halves are true and flat, the supplied CA hinges seem adequate, and everything goes together easily.

I'll cover the tailwheel assembly and tail pushrod set-up separately.


LSP972 03-16-2014 06:12 PM

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The rudder and elevator pushrods are identical to the ailerons; IOW, unsatisfactory for me. I had planned to do them the same way I did the ailerons; i.e., with clevises on both ends of two pieces of 2.2mm wire stock I used to make helicopter pushrods out of. This stuff is quite stiff, yet flexible enough for a more-or-less-straight run like this model has.

Then I discovered that I was out of 2-56 solder clevises, and I only had three clevises (needed four) with the proper metric thread that I cut into the ends of the rods with a hand die. Of course, this discovery was made at 2245 hours on a Friday night. So I dug around in my various junk boxes and came up with enough ball links and balls to do the job.

Again, this is one of those "mods" that works like a champ if you do it right… but is easy to goon up if you don't.I'll let the photos say the rest.


LSP972 03-16-2014 06:35 PM

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And, finally, the tail wheel. There are several issues here, so let's tackle them one at a time.

Good design, with so-so execution. For instance, I had to do a lot of squinting and bending/tweaking to get the axle properly aligned to the rudder and fuselage center line. The wire is rather soft, so go easy on those 3F slam landings, or you'll be doing a lot of straightening.

There is no bearing on the axle. That means the tail wheel is free to bind up in the corner formed by the first bend; and it will. I got lazy, and rather than doing a proper job via soldering a washer, I just snagged a large brass servo grommet liner and jammed it into place.

The "tiller arm" (the part that attaches to the rudder) is three times as long as it needs to be. Trim accordingly.

And the bushing that said tiller arm fits into (after you have glued the bushing into the bottom of the rudder) is… well, I cannot figure out exactly what's up with it. Look at the photos carefully; I know they're not the greatest, but I was overcome with sloth- again- and didn't drag out my good lighting set-up.

Notice how the bushing tab is off-set? The slot in the rudder is offset from the center line, as well. And despite my careful fitting, eye-balling, etc., my rudder hinge line was just a tad offset when I hit the hinges with CA. Fortunately, I had not yet glued that bushing in, and was able to finagle the position so I got a clean hook-up without any binding. By that I mean I reversed the bushing. It is apparently designed with that offset so it can be on the center line when installed in the offset hole cutg into the rudder bottom. What I did was flip it; the offset is now decidedly to one side, inside of on the rudder center line. And that matches the alignment error in my rudder hinge line. Like I said… I got lucky. My rudder is quite smooth.

You will, however, need to drill the bushing out with a 7/64" drill bit to allow the tiller arm to slide completely through. Note that the tiller arm MUST be able to slide freely in the bushing, or you will have a stiff rudder.


LSP972 03-16-2014 06:43 PM

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Well, I edited the last post and lost the photos.

Here they are again…


LSP972 03-16-2014 06:44 PM

Sigh. This thing is messin' with me… Thank goodness, only one more entry for now.

LSP972 03-16-2014 07:01 PM

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Forgot to discuss the main gear. Here is another exemplary area, with one glaring exception. The main gear legs and wheel pants are beautifully crafted, and extensively pre-fabbed for a perfect, no-brainer fit together. The 3mm button head bolts used to attach the pants to the legs are top-shelf.

The main gear axles, and the two nuts that are supplied for each one, obviously came out of a scrapped Chinese chow wagon. They are junk. However, lacking any suitable substitute (again, late at night and the LHS is closed… one day I'll learn to do this work during business hours), I used them.

The manual "suggests" that you use thread locker when installing the axles. Thread locker, hell; you better GLUE those puppies in place once the nuts are tightened; otherwise, you'll be constantly messing with them.

Beware of the four 4mm bolts, washer, and lock washer arrangement that secures the main gear legs. The washers don't all line up, and should be dropped into place BEFORE inserting the bolt…otherwise you can trash a bit of fuselage bottom sheeting. Don't ask me how I know that.


LSP972 03-16-2014 07:04 PM

Whew! That's about it, for now. I'll add more as I think of it, and/or fly the little ship. I'm thinking its (this particular one) is going to be a bit too heavy for flip-flopping around, but it ought to fly great in wind due to that. Hopefully it is smooth and has no bad habits.

Any comments/thoughts welcome…


Wildflyer 03-16-2014 07:49 PM

Very nice!!

One thing I would recommend, is to put some simple white bead Styrofoam or the crush foam you get in packages, it is similar to EPP, in front of the battery pack against the back of the firewall.

We have two very active clubs in my area. I am a member of both, Pres of the electric club. I see and hear of many crashes, and the results afterward. I can think of a few planes that could have been repaired, but unfortunately burned because the battery got smashed into the firewall. At the least the battery was mashed and bent. All of these planes used no padding in front of the battery.

Planes that had padding did not damage the battery. The foam adds almost no weight, but a lot of protection if needed.
I have blasted a couple of planes, trying to learn 3D, but I got my gear back.

LSP972 03-16-2014 08:02 PM


Originally Posted by Wildflyer (Post 942756)
Very nice!!

One thing I would recommend, is to put some simple white bead Styrofoam or the crush foam you get in packages, it is similar to EPP, in front of the battery pack against the back of the firewall.

Excellent idea. I started out doing this, but got out of the habit. Thanks for the reminder.

I spent many pleasant days (lot of wet ones, too!) in your area back in the 70s when I was at Fort Lewis.


LSP972 03-18-2014 05:52 PM

Maiden day!!! We got severe clear and light winds. I finished up at the range early; dashed home and did the final tweaks. The lateral balance is off a bit (due to the extra battery on the side of the motor box); I need 7g in the right wing tip. But I need to cut and patch the covering to properly install that weight, and I'm fresh out of dark Blue UltraCote. It can wait.

as soon as the TP 4S 3900s finish charging, I'm outta here.

Stay tuned…


LSP972 03-18-2014 11:45 PM

Well… it flies.

Of course, by the time I got to the field, the wind had kicked up; and by the time I was set up and ready to launch, it was blowing 15-20 mph, gusting to 25 mph, according to my little anemometer. Not the best conditions for a new airplane, but I was there, so…

1. Ground handling: the supplied tires on this model are "fat", like dragster tires. I.e., lots of surface contact. They are also of a material I've never seen before. Nicely done, but different. Our field hasn't been cut in a few weeks due to all the rain. Its starting dry out, and the cold temps have kept the grass from growing much, but its still an inch or better. The wheels kept grabbing big time; I had to really finesse the rudder and elevator to keep it in a straight line while preventing a nose-over and/or a leap straight up. The last two flights, I took it to the parking area behind the pits (nobody else was there). It is quite smooth there and the grass is beat down from all the vehicular traffic. No issues there taking off at all, although our safety guy would probably have a stroke if he knew.

Taking off on the rougher surface out on the runway was dicey indeed; landing was no problem. Just keep the nose slightly up, stay light on the elevator while she rolls out, then go pick it up. Taxiing was a no-go.

Conclusion… these tires were designed for smooth surfaces. If you fly off grass, I hope your field guys keep it short; VERY short.

2. Flying: This model is VERY responsive and quick. Don't spare the exponential. I started off with negative 40%, it was a handful, and I went up to negative 60% on the second and subsequent flights; much better. My throws are exactly per the book. Their suggested low rates and 40% expo, would, IMO, be a bit much for an inexperienced pilot.

That said… while it was hard to tell with all the gusting wind, the model seemed pretty stable and solid. On the third flight, I had a lull in the wind for about a minute, and the model calmed down quite a bit. I did an absolute greaser of a touch-and-go. I suspect it will be well-behaved on a calmer day.

THAT said… the model flies "heavy", IMO. Mine weighs four pounds 12 ounces RTF, with a TP 4S 3900mAh stick. I felt the need to stay near or at full throttle at all times. Certainly it would do better with a lighter/less-capacity battery, but seven minutes used every bit of the 80% capacity considered max for battery longevity. The Hi-Tec X4 put between 3100 and 3300 mAh back into all three batteries.

Once I got the CG sorted, the model showed no nasty habits. Keep in mind though, it was kind of hard to do a stall/snap test with that much wind blowing.

Conclusion: The jury is still out on this.

3. Center of gravity: I launched the maiden with the CG at 3" back from the LE at the root. I was fighting the squirrelliness (due to not enough expo), but still could tell it was on the nose-heavy side. On each flight, I kept moving the battery back a bit, and the last flight (#4) showed only a slight drop when rolling inverted on the CG test. Best I can tell, my CG is now at 3.25" back from the LE, and I think it could stand to go back a bit more.

Conclusion: The extra weight of my RX battery in front may be gooning things up. But it needed SOME weight up there, as has been the fact with others who built one of these.

I dunno… I want to like it, but something tells me to be very careful with this one. I certainly feel that it needs more motor than the Power 32 at this weight.

As always… YMMV.


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