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Old Jan 04, 2014, 07:47 PM
ARFs Are Me
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Traverse City, Michigan
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Nice Cub, Mr. E-Challenged !
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Old Jan 09, 2014, 07:15 PM
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United States, CA, Garden Grove
Joined Oct 2000
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Successful Maiden at Fairview Park

I had planned to do more taxi-testing, but the big Sig Cub wanted to fly, so I gave her more throttle and she lifted off in a scale-like manner. The CG setting is near perfect. The power of the geared Astro 25 on two 3S 2200mah packs in series is more than adequate. The wing incidence is near zero which also seems perfect. This model flys as good as an ARF . I flew a second flight, just as good as the first. Other than being a little difficult to transport with the 6-foot wing, I think this will be my new favorite. The E-Flite bungee and Carl Goldberg tail wheel assembly work well and look great. Couldn't resist adding a post maiden pic.
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Old Mar 21, 2014, 10:17 AM
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Hi! I have recently started building Sig's Clipped Wing Cub kit. I am almost done with the left wing and here my question comes: do you have any close-up pictures on how to assembly W8 together with front top and bottom spars? Any tips on how to do it properly?
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Old Mar 21, 2014, 12:06 PM
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Originally Posted by Marius_Marius View Post
Hi! I have recently started building Sig's Clipped Wing Cub kit. I am almost done with the left wing and here my question comes: do you have any close-up pictures on how to assembly W8 together with front top and bottom spars? Any tips on how to do it properly?
Not sure what you mean but you will probably get a lot of helpful ideas from my overly long build thread:

http://www.rcgroups.com/forums/showthread.php?t=1754853
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Old Mar 21, 2014, 10:32 PM
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USA, Mt, Billings
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Originally Posted by Marius_Marius View Post
Hi! I have recently started building Sig's Clipped Wing Cub kit. I am almost done with the left wing and here my question comes: do you have any close-up pictures on how to assembly W8 together with front top and bottom spars? Any tips on how to do it properly?
It seemed to me, after a LOT of thinkin' and fittin' and stuff that the key to the Sig Cub wing(s) was how high to shim the spars to that holds everything flat and allows the 1/16 sheeting and cap strips on the under side. Everything got assembled with the wing tip flat on the plan to provide location side-to-side, fore-and-aft. Once the ribs were all glued to the spars, trailing edge and aileron created (don't pay attention to spacers around aileron--they're only there for assembly) I then lifted the wing tip up to meet the several points it "picks up". Leading edge of wing tip is held so the edge of the leading edge "points" at the mid depth of the wing tip assembly, The spars match at-height into their "pockets" in the wing tip (these tend to need bits of 1/32 shim to glue tight) and the trailing edge matches up with the flat trailing edge of the wing rib immediately outside the aileron.

Pictured is the left side wing, already completed the right side wing. Found that after I figured out all the shims that the subsequent wings go MUCH more quickly. Good thing, I still have the "clipped" wings to build now since I'm building mine as a "convertible".

Note that where the wing tip meets the leading edge that you have a VERY narrow gluing surface. The leading edge is a square section on edge, so only a "corner" touches the wing tip. I set my stripper to 1/8" and pulled a piece of 1/4" triangle stock through it to make a suitable "wedge" (fillet) to fill that gap. Glued it in and clamped it down in place. Will do the same on the bottom side once I lift the wing off the plan and fit the bottom front spar.

Also note the fitting I made at the end of the top leading edge spar. The instructions had you bending the spar down to meet the wing tip...that looked like a LOT of bother and a questionable practice. I made these out of 1/4" or so hard balsa. Sanded it to shape while still on the end of the stick, then cut it out. The top leading edge spar lays on the inboard edge at the W5 wing rib and presents a LOT of gluing area. Glued to spar, wing rib, and wing tip.
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Old Mar 24, 2014, 03:17 AM
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Originally Posted by NOISY MUSE View Post
Also note the fitting I made at the end of the top leading edge spar. The instructions had you bending the spar down to meet the wing tip...that looked like a LOT of bother and a questionable practice. I made these out of 1/4" or so hard balsa. Sanded it to shape while still on the end of the stick, then cut it out. The top leading edge spar lays on the inboard edge at the W5 wing rib and presents a LOT of gluing area. Glued to spar, wing rib, and wing tip.
Thanks NOISY MUSE! This answers my question. I could not figure it out, how to avoid bending the top and bottom spars and gluing them to the wing tip assembly. If you don't mind I will follow your idea :-)
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Old Mar 24, 2014, 08:44 AM
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Here are a few pics of the fitting. I initially sketched it out, but did so while the wing tip wasn't lifted quite high enough relative to the LE so the fitting turned out to be twice as deep as it needed to be. I also initially made it too long. Good thing with balsa bits like this is they're EASY to modify if too big...if too small they're easy (and cheap) to throw away and make another one.

In the last picture the fitting is not yet glued in place, it is just positioned there. As indicated, it required a fair bit o' modification once the wing tip was brought up to position.

DO do your initial shaping on the end of a stick. Marked off is a 1/8" X 1/18" "socket" for the spar to lay on. The spar is then cut off flush with the outboard edge of W5.

Looking at these pics reminds me how much sanding I have in my comparatively near future....

Don't forget your triangle-shaped fillets to better join the LE and wingtip. These could be carefully done with a knife or razor, easier to to with a nice balsa stripper. You need about 8-10 linear inches of stock to do two wingtips top and bottom. Of course since I'm doing two wings I have four tips...
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Old Mar 24, 2014, 10:53 AM
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Ok, but following the instructions manual (building and flying instructions printout, added to the kit) about fitting the wing tip assembly I have the LE glued to the wing tip as shown on your last picture. So it is not in the middle of the wing tip. I am confused now.
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Old Mar 24, 2014, 11:59 PM
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In re-reviewing both the printed instructions and the plan I see no specific mention of how this is to be done. The "natural" point these seem to want to fall is with the top of the wing tip assembly at the rear-facing "point" of the leading edge. This is what is shown in the last picture, but at the point this pic was taken I had not glued the joint.

Consulting with a more experienced builder I decided to apply a little upward pressure and glue with the rear-facing "point" of the leading edge at the mid-line of the wing tip assembly. This required raising the front of the tip right at 1/8" and a look at the completed right wing shows that you CAN see the wing tip assembly bow up ever so slightly between the forward main spar and the leading edge. To accomplish this I glued the wing tip to leading edge joint last, after gluing (and allowing to cure) the wing tip to main spars joints. If you look at the third picture in my first post (#110) you can see how the wing tip assembly and the leading edge line up as I have it glued.

What is "right"? I couldn't tell you. Is it going to have a huge effect on the flying characteristic? I doubt much, though it could be argued I have created a (very) small amount of wash-in. As we are talking about such a VERY small portion of overall wing area, and an area where the wing decidedly tapers from both the top and the bottom, I'm guessing the performance effect of either choice would be negligible.

At least that's what I'm hoping.

By all means, if you can point me to something in the instructions or plan that I've missed please by all means do so. At this point it would not be difficult for me to cut these joints and re-do them.
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Old Mar 26, 2014, 11:07 PM
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United States, KY, Taylorsville
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Here's how I did it. What is nice is that if you drag a wing tip on hard surface the covering won't get cut loose.
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Old Mar 31, 2014, 01:01 PM
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United States, CA, Garden Grove
Joined Oct 2000
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I think you'll find that if the wing is reasonably flat with some symmetrical tip washout it will fly like a Cub. I worried about wing incidence vs stab incidence but built per plan and it was fine. Worried about CG for an elecric powered model vs IC design, Plan CG is between two vertical side window posts, mine hung dead level with heavy Astro flight geared motor and two 2200 3S lipos up against the firewall, no nose ballast needed.
Was worried about total weight and stall characteristics at around 7 lbs, no problem, slows down and does easy 3-pointers. Worried about power, old Astro 25 etc does easy loops with shallow dive. I haven't tried a roll or inverted flight yet but expect rolls will be slow and need a shallow dive. I guess the message is try to relax and enjoy the build, it'll fly in spite of your ankst. Make sure that wing strut attachments are secure at fuse and wing. I decided not to build the "clip-wings" but expect higher stall speeds and need for slightly different landing techniques such as landing on the mains with some power vs flairing. Articles on full scale clip wing Cubs indicate that plane drops like a brick with no power and that owners often wish they hadn't done the clip-wing thing.
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Old Mar 31, 2014, 02:12 PM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
907 Posts
Built a SIG clipped Cub in 1975.........my first R/C airplane. Powered by an Enya .35 glow. Disgusting engine. No idle. Took forever to break in.

Experienced members convinced me to learn R/C on an actual trainer. So built a SIG Kadet - 3 channel, no ailerons. Switched the .35 Enya into the Kadet. That poor airplane had more glue than wood by the time the club gave me my wings.

Then started flying the Cub - wow, ailerons. Nice flyer.

After all these years I still remember the conundrum at the TE of the wing tips. No mating wood surfaces to glue together. Think I glued in a balsa gusset and sanded it to shape.

Back then there was no CA. Had to use so-called balsa glue, SigMent, cellulose acetate. The stuff stunk and had no strength.

Good luck with your Cub.

Bill
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