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SIG Stratus (#RC4) - the long slow plans build

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SIG Stratus (#RC4) - the long slow plans build

Old 02-19-2015, 10:03 PM
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skylark-flier
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Default SIG Stratus (#RC4) - the long slow plans build

At long last I have them - plans sheets for the 1966-era SIG (RC4) Stratus. I've had a thing for this plane since it first came out 49 years ago, and in all that time I know of only one that's taken to the skies. That one was built by RCU ID heggen and is positively beautiful. Actually, he's also the source of my plans (including separate tracings of every wing rib) and I'd like to thank him right here, right now - this little project wouldn't be possible if not for him.

Just for reference, this is the only pic I've ever seen of any Stratus, and it happens to be his:

The basic measurements for the plane: ws=70", length=48.5", weight (projected)=6 - 7 lbs, engine=.45-.60

These are rather poor pics of my plans (cheapie camera) as laid out for the first time: Rib photos coming soon.

Anyway, I've been building kits since 1956 but this is my very first scratch (plans) build, so it's going to take awhile - and that's not helped much by the fact that the only place in this area to re-copy them is our local county office and their map copier is down for the next 2 weeks. That's OK though. It'll give me time to form a plan of attack. I'm thinking to do wings first, then tail feathers, then fuse. I'm also going to need all the advice I can possibly get - I'm actually feeling quite like a complete newby right now.

First consideration with the wings are the ailerons - they're only .75" deep, probably due to the types of radios available 50 years ago. I'm thinking seriously of increasing them to between 1" & 1.25", more in line with several other planes I've got active today. Also, the plans call for a completely sheeted wing but I'm thinking of "D-tube"-style sheeting and cap strips over the ribs. Any and all opinions would be appreciated here (see? I told you I'd be asking for advice).

So... we begin.
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Old 02-20-2015, 12:45 AM
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That is a nice looking plane Dave. I'm with you on the D-tube wing sheeting. What really strikes me is the thickness of the airfoil section. I'm guessing it's somewhere in the area of 16% of the chord. I suppose, like any other truss, the deeper you can make it the stronger it will be. I'm patiently waiting to see how this comes out.
Old 02-20-2015, 07:46 AM
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That's one beautiful bird there Dave. I'm certainly no expert but I think if you are going to cover with film I would do the wing D-tube with cap strips (like the Mk-II wing). I just happened to have a couple pieces of 3/32" sheet 3" x 21", two sheets should be pretty representative of what you would omit from one side of one wing panel. The two sheets weighed 1.12 oz. x 4 = a 4.48 oz. reduction. Realizing that balsa weights differ, the pieces I weighed are pretty average, neither contest nor dense heavy stuff.
I can't really tell from the photo of the plans if there are any shear webs, if not I would be guilty of adding them to the first 4, 5, or 6 bays.

Have you decided what you are going to power her with?
Old 02-20-2015, 08:32 AM
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Checking in Dave I have subscribed! I don't recall this airplane but if I had I think it would have been one kit I would have bought on first sight. I love the tail feathers! Do you have any data on the Rudder authority with them being out of the airflow of the propeller?

Mike
Old 02-20-2015, 08:35 AM
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I'm in, Dave.

This should be interesting, as the Stratus is something we don't ofter see.
Old 02-20-2015, 09:02 AM
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Hey guys!
Justin, you've got a pretty good eye! I measured each of the ribs and, allowing for my lack of precision, the ribs come out between 20.4% (low) and 22.7% (high). Once I add LE, TE & ailerons it's probably going to be right in the 18% range. Lotta lift, lotta strength, not a lotta speed buildup - which is wonderful as far as I'm concerned.

Don, I'm pretty much locked on the d-tube idea, along with adding a 3/16x1/8" piece to the front edge of the rear sheet, which I'm looking at being 1.5" deep. There's ZERO mention of sheer webs on the plans, just a balsa filler block between top & bottom spar at center. I'm planning to sheerweb everything out to 1 rib-bay beyond the landing gear, which is also where the double-thick spars end. I might go another rib-bay out from there too, just for my quality of sleep at night. Power, as of now, will be my OS.46AX with 11x6 prop - I really don't need a speed demon at my age anymore and Maxey Hester was kind enough to actually put a note on the plans that a .45 would drive her just as well as a .60, just not as fast. Sounds like the perfect combo to me.

The thing that really convinced me of using the .46AX is that my Sr. Falcon is nearly identical in size and she'll do anything I want with a .45LA driving her.

Mike, those tail feathers were what turned me on to this plane nearly 50 years ago. I'm hoping to get Sherwood in on this thread too - he's the guy that owns the plane in that first post and I'm sure he'd be able to fill me/us in on how she flies.

BTW, other than him, I only know of one other guy that has asked for plans - and I'm not sure whether he actually did anything with them.

Hey Tom! Glad to see you here.

Believe me guys, I'm gonna be asking questions. I can use all the help on this one that I can get.

First pics of the ribs:
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Old 02-23-2015, 09:39 AM
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Hi Dave,
The Stratus is a good subject to do as I've never seen one up close (other than a friend's kit). It is similar to what Ed Kazmirski was trying to do with Taurus II by adding tip plates to the stabilizer. This should be an enjoyable build.
Old 02-23-2015, 11:06 AM
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Hi Mike! Yeah, I've never actually seen one "live" either. Been working on sizing the ribs drawings so they match the sizes on the plans - just finished the last one about 10 minutes ago and printed off the whole batch after I saved them as a MS Word document. Now it's time to head to the shop and start cutting balsa. I figure that I've got enough balsa on hand right now to do about half the plane - which means an order will be heading out to SIG in the very near future.

Justin! After re-measuring and adding them, each, into my ol' 'puter, the wings come out at 19.85%, with LE, TE and sheeting included. Was probably originally designed to 20% - that's a thick wing!!!!

Got an answer back from SIG this morning on a definition. Plans say to use the "fenilite" tabs (included in kit) for the imbedded rudder horns - had no idea what fenilite was. SIG says it's closest modern material is standard circuit board. Now all I have to do is hit our local Radio Shack before they close.

Loving it!
Old 02-23-2015, 02:50 PM
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God, what a great looking airplane. Think I've found my next "winter build." I'm subscribed! Bet you're going to get a lot of requests for copies of the plans. Was that "subtle" enough?
Old 02-23-2015, 03:08 PM
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Dave,
I did some research and took measurements off of some old plans to compare airfoil thickness. A Goldberg Falcon 56 comes out to about 13%, Sr Falcon pretty close to that. Topflite contender is roughly 16.5%. Some of the older plans I've got figure out less than 10%! Like you said, 20% is thick and would definitely curb any build up of excess airspeed. It will also bleed off speed real fast, which is a characteristic I like.
Fenolite sounds like a trade name for phenolic sheet. It used to be pretty common in several different grades, but all I can quickly find now is linen based phenolic sheet through aircraft supply stores. Being sold for full sized planes makes it cost 10 times more than it should. I think circuit board material would work fine. Carbon fiber sheet would too, but again, very expensive.
Old 02-23-2015, 05:43 PM
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G-10 from McMaster-Carr will work.
Old 02-23-2015, 08:41 PM
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Yup! Phenolic sheeting - precisely what SIG said. In the "thick" department, the Kaos has always been touted as having a thick wing that precludes speed buildup. Wonder how thick that one is.

G10 - WOW, just took a look-see and you're right. That would fill the bill quite nicely. Wonder if they'd be willing to sell it by the square inch (LOL)? Not kidding guys, the plans call for 2 pieces, each .25" wide by about 1.25" long - that ain't very much. Gonna give 'em a call though.

Homer712 - right on! As soon as my local map copier is back online I'll just have them print another one, and I'll print another copy of my ribs too. Got about half of them cut today and they seem to come out right on the mark. BTW, I'll hand-deliver 'em - you're only an hour+ away from me and there are GOOD restaurants in your area that I know of (unlike here).
Old 02-23-2015, 08:44 PM
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I am happy to see the interest in the Stratus that Dave is building. He mentioned that he has had a thing for this plane for 49 years. I actually saw the Stratus fly for the first time at the Mason City, Iowa airport the summer of 1964. It was piloted by a man by the name of Larry Jensen who I believe was a pattern competitor. I drooled over the airplane but could not afford one at 18 years old. About 10 years later, I saw one available in a hobby shop in Minneapolis and had to have it to build some day. I had built the Sig Simco which is identical to the Stratus except for it has a conventional tail and a foam wing. It was a sweet flying airplane which had an untimely death due to a failed elevator linkage. I nearly cried. The Stratus kit remained in my stash waiting for the right time to build it which finally happened in 2005. The only modification I made to her was the ailerons which I increased in chord to 1 1/4". The airplane was designed around multi channel reed radios and smaller control surfaces were necessary. I power my Stratus with an Enya 60 from the 1970's with a 12-6 prop. Great engine except the muffler keeps coming loose which has caused a lot of down time while I am trying to figure a positive way to secure it. The thick wing doesn't slow it down much. It really scoots but slows down fairly well at low throttle and flairs nicely before touchdown. Rolls are clean and axial and loops are big and round. I have found no concerns regarding the twin rudders. It seems to fly just like any other pattern type ship except it just looks so cool in the air with the twin tail. The one maneuver I have not tried is a spin which perhaps could suffer from the lack of rudder directly in the slipstream. Even if that is the case, I wouldn't care. It flys great and is an attention getter at the field from all of the ARF assemblers and some of the old timers as well.
I couldn't put plastic film on the Stratus but I didn't go with silk and dope either. My finish was glass cloth and epoxy, auto primer and Rustoleum paint. It is a great way to finish as long as you do the base color (white in this case) with an automotive catalyst added to the paint and applied with a spray gun. If you don't, Rustoleum recoated tends to crinkle ruining the base coat. Just be sure to clean your gun right away or you will be cleaning solidified paint out of it. With the catalyst cured base, trim colors can be masked and applied the next day directly with the Rustoleum spray can with no fear of any crinkling.
I am really looking forward to seeing Dave's build effort. Build straight, strong, and light and you will have a great airplane.
Go, Dave!
Sherwood
Old 02-24-2015, 10:45 AM
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Dave, I think Luray, VA to the Frederick, MD area is a bit more than an hour away, but, if you are good enough to copy and hand deliver the plans, lunch at your choice of establishments is on me.
Old 02-26-2015, 12:14 PM
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Well, it's started! Ribs are cut and trimmed, spars & TE are cut and the right wing skeleton sits on the table - unglued as yet but it'll be glued as soon as I get the jigs sized & cut properly (which is turning into a minor project of its own). Plan is to tack-glue and then remove it from the plans for "real assembly". County says their new copier will be online by Thursday (7 more days - sheesh!) - until then I've got to be super careful with those plans.

Only issue so far is my own stupidity - TE is supposed to be 1/4 x 1/4" stick, I bought 1/4 x 3/8" which is the main reason the ribs are just sitting there above it. Planning to snip the tail off the ribs and press on with the deeper TE, which should help a bit with hinges when that time comes. Sherwood did a GREAT job tracing those ribs too - just a minor bit of trimming on a few of the spar slots to fit the spars, top & bottom.

Hey guys, need an opinion here. Center joint on this wing is totally unsupported by "ribbing" on each end (front/back) of the servo box. I'm thinking of fitting ribs in what would be the "0" position, where the wings fit together. Opinions? Is there another way to get strength/support for the sheeting at the join joint? I'd imagine there are lotsa others but this is the first plane I've worked that doesn't have a rib (or a pair of them) at the center joint.

Here's what I've got so far - just the right side:


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Old 02-26-2015, 12:19 PM
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You could easily make some center ribs. I think I would go that route, if I were building one.
Old 02-26-2015, 12:28 PM
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Originally Posted by TomCrump View Post
You could easily make some center ribs. I think I would go that route, if I were building one.
I'm with Tom, and if want some additional support laminate a couple pieces of ply and slot a few of the ribs, say pass the ones you and one or two more so the ply slides down between the main spars and epoxy the heck out of it.
Old 02-26-2015, 12:35 PM
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Yeah Tom, that's kinda what I was thinking too.
Mike, I'm with you on the solid spar idea - was planning to do exactly that from center to just beyond the landing gear ribs anyway, then just webbing to the wingtip.
It might make the wing a bit heavier but it'll be a LOT stronger, especially seeing as 99% of my flying is from rather rough grass.
Old 02-26-2015, 02:49 PM
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The ribs look good Dave. I would want the center ribs as well. Are you going to use dual aileron servos or a single one?
Old 02-26-2015, 03:04 PM
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Originally Posted by skylark-flier View Post
Yeah Tom, that's kinda what I was thinking too.
Mike, I'm with you on the solid spar idea - was planning to do exactly that from center to just beyond the landing gear ribs anyway, then just webbing to the wingtip.
It might make the wing a bit heavier but it'll be a LOT stronger, especially seeing as 99% of my flying is from rather rough grass.
I prefer my spars to be joined in the center. That way the joint can be reinforced with a heavy ply or hardwood joiner.

Moving the spice outwards doubles the amount of needed splicing, and potential for failure.
Old 02-26-2015, 06:06 PM
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Absolutely Tom! Actually, there's a balsa block on the plans that's the only "planned joiner". Take a look-see here:
I put a red outline around what the plans talk about, and a red/green line where it goes. The yellow is what I actually plan to do as far as a solid center joint - and that's going to be 3/16" ply. Going to take a bit of carving and fitting but I don't want to even THINK that the wing could ever separate at the center.

As far as servos go, I'll definitely go with a pair, side-by-side. Not that I'll ever put a whole lot of stress on the aileron function (I'm not that "violent" a flier), but I've had servos go bad - and it's not fun when the plane's in the air. I tend to do twin servos for elevators & ailerons most of the time. That way, if one DOES go bad the other can at least get me to the ground semi-safely.
Even my Kadet Mk-II is set-up that way.
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Old 02-27-2015, 05:53 AM
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To be effective, the balsa block needs to be planed with some reasonable accuracy to get a good joint. You might try fabricating a couple of plywood joiners, say 1/8" thick and installing them in the servo well but you would still need the blocks shaped to fit the joiners. Or, you could build it like a Kaos wing. Fabricate two 1/8" root ribs, build the wing panels then butt join them together before the wing sheeting is added. Add the center section wing sheeting from the outboard ribs starting from where ever you like to tie the two panels together. When the sheeting was complete and sanded, apply a band of glass cloth and epoxy resin (West Systems) around the center joint. Nice, strong and simple. Rather than use rubber bands, install two dowels in the leading edge and hardwood blocks in the trailing edge to bolt the wing on.

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Old 02-27-2015, 07:04 AM
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Beautiful airplane - Subscribed!
Old 02-27-2015, 11:13 AM
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Originally Posted by Michaelj2k View Post
To be effective, the balsa block needs to be planed with some reasonable accuracy to get a good joint. You might try fabricating a couple of plywood joiners, say 1/8" thick and installing them in the servo well but you would still need the blocks shaped to fit the joiners. Or, you could build it like a Kaos wing. Fabricate two 1/8" root ribs, build the wing panels then butt join them together before the wing sheeting is added. Add the center section wing sheeting from the outboard ribs starting from where ever you like to tie the two panels together. When the sheeting was complete and sanded, apply a band of glass cloth and epoxy resin (West Systems) around the center joint. Nice, strong and simple. Rather than use rubber bands, install two dowels in the leading edge and hardwood blocks in the trailing edge to bolt the wing on.
You're right Michael, that block would need to be near perfect - which really isn't all that much of a problem. Understood about the Kaos wing - I'm just amazed that she holds together without interior blocking. In any event, there WILL definitely be root ribs, which are not included on the original design. Do I have it right - sheeting might go from left rib #4 across to right rib #4 as a single piece? THAT is something I've never seen, but I LIKE IT.

The good news is that I'm learning, and hearing GREAT ideas on how this should be done. Still got time yet. Neither wing will be ready to come together for awhile yet.

Yeah, already decided right at the start that there would be no rubber bands holding this lady together. No plans to even include the dowels for it. I AM planning, however, to use a slightly different front anchor - 3/16" thick ply tongue about 1" wide instead of twin dowels. I first tried it with my Eagle-II back in the late 1970's and many of my planes since have incorporated it.

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Old 02-27-2015, 01:39 PM
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Whenever possible, I sheet center sections without a joint in the middle. I think that it strengthens the structure by doing so.

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