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Old Sep 24, 2012, 09:07 PM
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Build Log
Sig 1/6th clipped wing cub build/ questions

Hi all, this will be my first "build log". I had previously posted this in fuel plane talk but I think if fits better in the builders section as many of my questions will be about the build. I know there are a lot of cub build logs but they are usually vague on some of the details once they are framed up. I am building it semi scale/stand off scale. I have everything basically framed up but am creating this thread as a way to ask many of the questions I will have over the next few months. I have built a decent amount before but the hardest part for me is getting all the final details figured out especially on a kit that gives little advice for these steps. I figure this will be a great way to collaborate all of my struggles in one place. It will be a slowish process because I am also a college student and unfortunately tests take priority. Here are some pics of the progress so far and here is a list of the things I have been contemplating as well. Let me know any input you might have on this topic.

-One piece or two piece wing? - like the idea of a two piece with one servo for each aileron but only done one piece wings with one servo in all of my previous builds.

-Where to get tubing (and what size) to make it a two piece wing- is it too late to go that route with the wings framed up? The two wings halves are not glued together yet.

-Should I do the recommended dihedral or do zero dihedral? What are the pros/cons of either way?

-Engine selection: I have O.S. 48 surpass and a Saito .45 four stroke engines, any thoughts appreciated. I am leaning to toward the O.S. 48 as it is newer and I have ran it successfully multiple times.

-Gas tank size- I have a 10, 8, 6oz and smaller tanks but am leaning toward the larger for longer flights. The 10 will fit but would it make it too heavy??

-Covering-may be getting ahead of myself but it will be done in fabric. The iron on type. Probably 21st century colored fabric covering. Anything better or other suggestions?

-Planning on doing a pull pull system on rudder so I will have questions on that later as well.


I built the landing gear based off of these threads:

http://www.rcgroups.com/forums/showthread.php?t=906156
http://www.rcgroups.com/forums/showt...8#post11394083
and toyjunker had a few threads that were a big help


That's all I can think of right now so again, I appreciate any and all input. Thank you.

-Greg
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Old Sep 24, 2012, 09:32 PM
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Hi Greg- two wing halves version not hard to build. It makes the fuse covering look more realistic, too! Brass tubes in fuse receive wire stubs mounted in wings while functional struts keep wings from coming off in flight. Put scale dihedral in wing. No dihedral looks strange- like the wings are actually drooping. If you are handy with Stay-Brite solder and torch then fabbing a tank to fit in scale location is an option. These airplanes can lift a 10 oz tank. Better yet, put a 40 four stroker in it for even better economy! I love SIG Koverall. There are similar products like Stits's 'Lite' fabric that you can use if you'd like an authentic doped finish. Pull-pull is very easy to do. I know you have seen my Super Cruiser but if you have any questions I can try to answer. Cheers!
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Old Sep 24, 2012, 09:42 PM
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Originally Posted by ARUP View Post
Hi Greg- two wing halves version not hard to build. It makes the fuse covering look more realistic, too! Brass tubes in fuse receive wire stubs mounted in wings while functional struts keep wings from coming off in flight. Put scale dihedral in wing. No dihedral looks strange- like the wings are actually drooping. If you are handy with Stay-Brite solder and torch then fabbing a tank to fit in scale location is an option. These airplanes can lift a 10 oz tank. Better yet, put a 40 four stroker in it for even better economy! I love SIG Koverall. There are similar products like Stits's 'Lite' fabric that you can use if you'd like an authentic doped finish. Pull-pull is very easy to do. I know you have seen my Super Cruiser but if you have any questions I can try to answer. Cheers!
Thanks for the advice. What size brass tubing would be appropriate? Obviously the smaller the tube the lighter weight it will be but I also want it to be strong. I would need some sort of tunnel for each aileron servo wire to run through as well correct? I haven't doped or used non iron on covering yet but maybe i'll have to give it a shot, the results do look great when its done right.

-Greg
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Old Sep 25, 2012, 09:59 AM
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The brass tubes don't have to be big at all. Mine are big enough to receive 1/8" wire stubs. The struts, wing itself and fuselage create a 'system' which is triangular shaped, rigid and very strong. Just think of supporting your Cub by its wingtips. Imagine it inverted vs 'normal'. What do the wings, fuse and struts want to do when you do this? The full scale version has spars that bolt to carry thru spars in fuse. Mine has brass tube with balsa around it that matches the location of wing spars which counters compression. If this was a BIG airplane I'd use spruce. If really BIG I'd make it like full scale. Tension is countered by bolts inside fuse to wing root at c.g. point (approximate). That's why I have a functional door! Also, think about what wings do when airplane is flying straight and level and comes to abrupt stop. Hopefully yours will never do this but it helps to think about it for building the cabin area for wing support. Think about it in reverse, too! Going from a dead standstill to immediate full power what do the wings wanna do? Sorry for long winded post. I'm sure you know these things but it's nice to really think about 'em when doing these kinds of mods to a kit.
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Old Sep 25, 2012, 10:20 AM
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Quote:
Originally Posted by gjap View Post
Hi all, this will be my first "build log".

-One piece or two piece wing? - like the idea of a two piece with one servo for each aileron but only done one piece wings with one servo in all of my previous builds.

-Should I do the recommended dihedral or do zero dihedral? What are the pros/cons of either way?

-Covering-may be getting ahead of myself but it will be done in fabric. The iron on type. Probably 21st century colored fabric covering. Anything better or other suggestions?

-Planning on doing a pull pull system on rudder so I will have questions on that later as well.

-Greg
Hi Greg
I've had both the Sig 1/5th and 1/6th Cubs - the latter was a clipwing. See above for making a two piece wing, which the 84.5" span 1/5th comes with - and needs! I'd go with the scale dihedral - without that, it looks like any of those goofy ready-made rip-off Cubs made in China.

The snag with a two piece wing is you're going to have to build the fuselage top to do the job, which its not really designed to do right now. Under your college constraints, if you can carry the wing around, building it as per the kit will be a lot quicker and less fuss than a split wing redesign. Fitting one servo per aileron is real good, vice the ancient centre servo, pushrods and bellcranks. Hope you're going to put them inside the wing? Nothing looks worse than servos hanging out in the breeze, even more so on a scale model.

Covering - there's always the British made 'Solartex' heatshrink fabric, though it can be tricky to find. My clipwing 1/6th was in a scale colour scheme of a Florida based clipwing Cub, though the colours were 'Monokote scale'. If you want a Cub that stands out from the 'yellow herd', go looking online, there's a lot of choice.

Pull/pull rudder - good idea. Much easier if you can put the servo in line with where the control cables run on the full sized Cub, makes for easier to get them out at the right spot and to a control horn that looks scale.

Sorry - you're on your own for engines. Mine didn't make noise, didn't need much cleaning post-flight and smelled nice too I'd go with the engine that fits best under the cowling though - inverted perhaps? Not like they need much power - I saw a 'real' J3 do an 'aerobatic' routine once. Took him three or four minutes to get high enough to start every one of his aerobatic maneuvres - an odd shaped loop, a sloppy great barrel roll and a one turn spin!

Mine was, bar the power system, built pretty much out of the box and flew great from flight one.

Good luck

Dereck
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Old Sep 25, 2012, 07:57 PM
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Hi Greg
I've had both the Sig 1/5th and 1/6th Cubs - the latter was a clipwing. See above for making a two piece wing, which the 84.5" span 1/5th comes with - and needs! I'd go with the scale dihedral - without that, it looks like any of those goofy ready-made rip-off Cubs made in China.

The snag with a two piece wing is you're going to have to build the fuselage top to do the job, which its not really designed to do right now. Under your college constraints, if you can carry the wing around, building it as per the kit will be a lot quicker and less fuss than a split wing redesign. Fitting one servo per aileron is real good, vice the ancient centre servo, pushrods and bellcranks. Hope you're going to put them inside the wing? Nothing looks worse than servos hanging out in the breeze, even more so on a scale model.

Covering - there's always the British made 'Solartex' heatshrink fabric, though it can be tricky to find. My clipwing 1/6th was in a scale colour scheme of a Florida based clipwing Cub, though the colours were 'Monokote scale'. If you want a Cub that stands out from the 'yellow herd', go looking online, there's a lot of choice.

Pull/pull rudder - good idea. Much easier if you can put the servo in line with where the control cables run on the full sized Cub, makes for easier to get them out at the right spot and to a control horn that looks scale.

Sorry - you're on your own for engines. Mine didn't make noise, didn't need much cleaning post-flight and smelled nice too I'd go with the engine that fits best under the cowling though - inverted perhaps? Not like they need much power - I saw a 'real' J3 do an 'aerobatic' routine once. Took him three or four minutes to get high enough to start every one of his aerobatic maneuvres - an odd shaped loop, a sloppy great barrel roll and a one turn spin!

Mine was, bar the power system, built pretty much out of the box and flew great from flight one.

Good luck

Dereck
Thank you for the advice. Your clipped wing cub looks so nice!! I will go for the scale dihedral (I think the instructions say prop up wing tips 7/16th of an inch at spar w4 which comes out to 1.2 degrees dihedral which I think is scale. I have time and like building so I think I will go for the split removable wings. When you say servos in the wings do you mean everything including the control horns? I was thinking of having them sideways in the wing with the control horn of the servo only coming out to link with the ailerons. Or do you mean everything done internally? I will look into those coverings as well. Thanks again.

-Greg
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Old Sep 25, 2012, 09:04 PM
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I made hatches for servos. The servos are Airtronics 94501's. Hitec HS-125 MG's will fit nicely. The servo is attached to the hatch as a matter of fact!

Pretty clipped wing Cub!
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Old Sep 26, 2012, 10:30 AM
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Greg
You could duplicate the Cub's full scale aileron linkage - it's a closed loop set-up with wires coming out of the wing on top and bottom surfaces. On mine, I cut out a ply copy of the wing rib from mainspar to TE, cut that out to take my aileron servo - Hitec HS81, IIRC - and mounted the servo inside the wing. The pushrod is regular Sullivan 2-56 Goldenrod hardware, clevis and so on to a nylon horn. The 'hatch' is nothing more than 1/16" balsa sheet, cut to shape and clear the pushrod, covered to match and taped into place.

I've done 'scale' for competitions, albeit a while ago, and learned you have to say 'enough' when the aim is mostly to just go fly! I can live with a pushrod and clevis out in the breeze for serviceability on a nice Sunday

The other way of mounting a servo internally is to mount the servo onto a plywood hatch and screw that hatch into hard points in the corners of a rib bay. It works, I usually use the ply rib and none structural hatch, but it's down to your preference.

For real ugliness, just have the servos hanging out in the breeze with the servo arm rotation 90 degrees removed from the control horn rotation...

D
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Old Sep 27, 2012, 08:49 PM
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Originally Posted by Dereck View Post
Greg
You could duplicate the Cub's full scale aileron linkage - it's a closed loop set-up with wires coming out of the wing on top and bottom surfaces. On mine, I cut out a ply copy of the wing rib from mainspar to TE, cut that out to take my aileron servo - Hitec HS81, IIRC - and mounted the servo inside the wing. The pushrod is regular Sullivan 2-56 Goldenrod hardware, clevis and so on to a nylon horn. The 'hatch' is nothing more than 1/16" balsa sheet, cut to shape and clear the pushrod, covered to match and taped into place.

I've done 'scale' for competitions, albeit a while ago, and learned you have to say 'enough' when the aim is mostly to just go fly! I can live with a pushrod and clevis out in the breeze for serviceability on a nice Sunday

The other way of mounting a servo internally is to mount the servo onto a plywood hatch and screw that hatch into hard points in the corners of a rib bay. It works, I usually use the ply rib and none structural hatch, but it's down to your preference.

For real ugliness, just have the servos hanging out in the breeze with the servo arm rotation 90 degrees removed from the control horn rotation...

D
Thanks Dereck, That picture is exactly what I had in mind for the aileron servos. I was planning to screw the hatches in somehow as well.
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Old Sep 27, 2012, 09:53 PM
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The hatches on my Super Cruiser mount to 4 hard points in wing pocket. It's easier to remove a servo from the hatch than wing especially if servo on its side. You can really get 'fancy' and make the servos fit the wing without screws. Removing hatch allows servo to be lifted. If a 'tongue' glued on one end of hatch then only 1 or 2 screws would be needed to hold hatch which holds servo!
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Old Sep 29, 2012, 07:29 PM
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Ok Ill probably start work on that after I finish the two piece wing situation. Ive got one of the rods and tube worked out and will do the second one soon. So far everything looks to be good, I went with the recommended dihedral.
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Old Oct 05, 2012, 04:28 AM
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Progress so far has been installation of the engine mount, and almost finished the two piece wing set up. However I have also been looking at the ailerons and trying to figure out the best way to hinge them. I constructed them as per the plans so there is a beveled edge (see attached picture) which is confusing me on how the hinges will work. With this set up will a centrally installed hinge (like a two piece ca hinge) still work? I have not hinged ailerons with the leading edge beveled like this before. Any input is appreciated, also any suggestions on the best hinges for this application are also welcomed. Thank you.

-Greg
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Old Oct 05, 2012, 04:42 AM
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I think I figured out that the beveling is for some sort of taped hinge. I would prefer to use something more robust on this aileron so I will just bevel the top to make a triangle point at the center, this way I can install a normal type of hinge at the center point. Why the sig booklet suggests beveling the aileron this way but includes one piece molded hinges is beyond me... I would still appreciate any input on the best quality/durability hinges to use here. Thanks again.

-Greg
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Old Oct 05, 2012, 08:21 AM
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I used the supplied hinges, on my Sig Spacewalker. They are the traditional pinned hinge, similar to what Dubro markets.

The ailerons are similar in design to yours.
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Old Oct 05, 2012, 10:59 AM
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Recall making the aileron section a little differently so I could use mylar film type hinges on my Sig 1/6th, though the hingeline was still pretty close to the top surface of the aileron.

Tom's route is good. If you have a small gap between aileron and wing using pinned hinges, it could be easily sealed with a narrow strip of matching film covering - pretty much like the full sized Cub uses. For gap sealing on a painting finish, you could use clear office tape, though sealing the gap from underneath would be neater in that case.

A wing/aileron gap can worsen the tendency to adverse yaw that high wingers tend to suffer from, though I don't recall it being an issue with my Sig Cubs.

Hope that helps

D
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