Sig 1/6 scale cub build questions

[aeroncalover]

It has been my experience that there is nothing quite like a new balsa build to really put you in your place just when you think you're getting to be a skilled builder. Just is the case with my Sig cub.

The basic framing is all pretty simple, but being the biggest plane I have built as of yet there are a few things stumping me. I figured the culture of this forum would be more conducive to problem solving than others *cough* RCG *cough* as I can openly admit my stupid mistakes and not get blasted for them.

so question one- How can I make sure the wing is not warped? On smaller models simply sighting down the wing is enough, but on a model as large as this I would think there would be a more accurate method.

question two- To make the exhaust tubes I have seen others solder brass tubes together, but I seem to have quite a bit of trouble soldering any tubing together. So how can I join the lengths together strongly?

Question three- what would the best material be to make the cylinder eyebrows from? I have found a template on the Cub-den.com trace onto whatever I decide to use.

Four- I am planning on using streamlined aluminum tubing for the struts, but the jury strut attachments are throwing me for a loop. If anybody can offer up advice as to how to fashion them it would be appreciated.

Thanks for any help you can offer. If there is enough interest I could start a build log, as I am still pretty early on in the build!

 

[willsonman]

See my comments in red.

It has been my experience that there is nothing quite like a new balsa build to really put you in your place just when you think you're getting to be a skilled builder. Just is the case with my Sig cub.

I love the smell of balsa in the morning

The basic framing is all pretty simple, but being the biggest plane I have built as of yet there are a few things stumping me. I figured the culture of this forum would be more conducive to problem solving than others *cough* RCG *cough* as I can openly admit my stupid mistakes and not get blasted for them.

WELCOME!

so question one- How can I make sure the wing is not warped? On smaller models simply sighting down the wing is enough, but on a model as large as this I would think there would be a more accurate method.

Build on a flat surface is your best bet. I've used a flat wooden table, bench and even a piece of glass (use weights instead of pins). When you cover your wings with an iron-on film, Cover the curved surface first while the bottom is flat (assuming since it is a cub that it is a flat-bottom airfoil).

question two- To make the exhaust tubes I have seen others solder brass tubes together, but I seem to have quite a bit of trouble soldering any tubing together. So how can I join the lengths together strongly?

Your best bet is to use an instert of a slightly smaller ID of tubing. However, I've used styrene tubing just as effectively. You can heat the tubing with a candle or heat gun and bend the tubing to shape.

Question three- what would the best material be to make the cylinder eyebrows from? I have found a template on the Cub-den.com trace onto whatever I decide to use.

I'm not sure what "eyebrows" are on an engine. Can you please provide a picture or other visual reference?

Four- I am planning on using streamlined aluminum tubing for the struts, but the jury strut attachments are throwing me for a loop. If anybody can offer up advice as to how to fashion them it would be appreciated.

I would use a simple servo clevis. Use a flat piece of metal as a connection point on the fuselage and wing. THen you can just spread the clevis apart and slip them on at the field. Nylon should be sufficient at this size. My cub (L-4 Grasshopper) is a 72" span bird and uses plastic clevises perfectly.

Thanks for any help you can offer. If there is enough interest I could start a build log, as I am still pretty early on in the build!

 

[aeroncalover]

See my comments in red.[/QUOT

Well I can't figure out how to upload pictures, but the eyebrows are scoops that fit over the cylinders on the outside of the cowling to help cool the engine.

https://www.google.com/search?q=pip...UIBygB&biw=1920&bih=969#imgrc=PxXrd7ODOExerM:

maybe this link will work.


About the jury struts, I am more stumped by the jury strut attachment to the lift strut.

 

[willsonman]

I would use sheet styrene. It will take CA or plastic cement just fine. The other option is to make a solid foam block and glass it. Then melt the foam out with acetone and there you have a single solid piece. Another option is 110# card stock. Once you have it glued in place you can soak it with 5-minute epoxy to make it more robust. Just thinly spread on the epoxy with a q-tip.

Many options. More that I've not included but those come to mind.

For the jury strut, I would use simple wire and landing gear straps. Making a "U" shape with the wire for the strut and placing the straps on the wing you can make it easily come together. Again, use the straps on the main strut to tie in the jury strut. This is all so that you can easily remove the strut if you make your wings so that they disassemble.

 

[aeroncalover]

I like the idea of the LG straps for the jury strut. Another idea I had is to use streamlined tubing for the lift and jury struts. this way I can fatten out a section of the jury strut and screw it straight to the lift strut. I'm not that concerned about being able to remove the strut from the wing when I disassemble the plane, so hard mounting the two together is fine by me. I used this method on my Baby Ace, and if I could figure out how to upload pictures I would show how I did it.

 

[willsonman]

below the reply window, click go advanced. Then scroll down and click manage attachments. From there you can upload but keep in mind that there is a size restriction of 2 Mb for each picture so you may have to re-size.

 

[aeroncalover]

below the reply window, click go advanced. Then scroll down and click manage attachments. From there you can upload but keep in mind that there is a size restriction of 2 Mb for each picture so you may have to re-size.

I actually managed to figure out how to do it right after I posted that!

Right now I'm inching along on the cub. I've hit the point where you can work all day and not see any progress when you finish.

Probably going to swing by the hobby shop this afternoon, so I might buy the strut material or I might wait and use the pine they supply in the kit, I haven't decided yet.

I'll see if I can throw some pictures up tonight!

 

[AkimboGlueGuns]

I've only got a bit of experience with balsa, but it's not TOO hard to build with. Lot's of old school builders make it seem a bit mire complicated than it really is. Without a jig, you can just use a flat table and a small square. Make sure the square angles are square, and you'll usually get a nice straight wing.

 

[dwight]

I've only got a bit of experience with balsa, but it's not TOO hard to build with. Lot's of old school builders make it seem a bit mire complicated than it really is. Without a jig, you can just use a flat table and a small square. Make sure the square angles are square, and you'll usually get a nice straight wing.

And start with straight, true spars. Trying to build the warp or twist out of your materials is an education in frustration...

Dwight

 

[aeroncalover]

So now I pose the opposite question: how can I accurately warp the wings on purpose? I've been told to add washout to the wings, but I want to be sure I have the Washout accurate and equal between the two wings. Another suggestion I've heard is rather than warp the wings to add washout, deflect the ailerons so it acts like washout. I just can't wrap my head around how this would work, or which direction to offset the ailerons. If it does work this would be a simple adjustment of the control linkage.

 

[willsonman]

Its not really washout with the aileron method but more akin to the FT idea of undercambered tips. By deflecting the ailerons down you have a more constant lift area at the tips due to being more "undercambered" but its kind of a cheat. I honestly would not recommend incorporating washout on a cub. Reason being is that the twist will not behave the same at all flight conditions due to the wing design (constant chord). You will find that it is less effective at slower speeds when you really need it and you will have trim issues at higher speeds.

I think that if you did want to add some down deflection to your ailerons that would be a good place to start but really you should be coordinating your turns with rudder to keep the wings more level. If you are not used to this flying style than you really should invest in a good 4-ch trainer to practice it. Cubs WILL tip-stall if your turns are not coordinated.

 

[aeroncalover]

Here are some pictures of the cub. Ordered the cover, ESC, motor and battery today. Power will be an E-flite power 32 with a 60 amp E-flite esc, and a 3200 4s lipo. Right now the weight is 3 pounds. The power 32 says it works for 3-6 pound scale models. I'm guessing the cover and finishing details will add about a pound or pound and a half.

 

[aeroncalover]

Right now my wings look straight as an arrow, so I think I will leave it alone. I know how to coordinate turns, and I refuse to add any mixes to my models so I wont get spoiled and forget how. I practice stalls every time I fly my Flyzone Super Cub so that I can be more confident in my ability to recover when I get into real trouble. Something about the design of cubs make them spin worse than anything. No matter what model or brand it is, all cubs spin like mad. I don't now if the real ones are like this because I've never spun one, but if all the models do it, I would think the real ones might too.

 

[aeroncalover]

Right now I'm waiting on the motor, ESC, battery, and covering materials to arrive. The firewall back is done and just needs to be sanded before I apply covering.

The nose from the instrument panel forward is not done yet because the firewall has to be installed before the sheeting can, the firewall has to have blind nuts installed before it can be mounted, and I have to have the motor before I can install blind nuts.

Also a few scale details left to be done like and instrument panel and the cylinder eyebrows.

My cub decals were damaged when I got the kit. It looks like the decals were peeled up, got balsa dust all over the adhesive back, and now will not stick. Sig will not replace the decal sheet because I bought the kit through Tower hobbies and according to the lady I spoke with on the phone "Sig is not associated with tower hobbies". I decided not to be rude about it and push her as she sounded like a new employee, but sig is a subsidiary of tower hobbies.... Anyways rather than buy an all new decal sheet from Sig since all I am going to use are the cub decals, I found a person on RCG who will print me a set of cub decals as well as some custom nose art.

With any luck all of the electronics and covering will be here this week!

 

[aeroncalover]

Got everything I need for the cub last night, which are: a power 32, and 60 amp esc, a 4s 3200 mah battery, a receiver, 2 servo extensions, a y connector, 3 yellow rolls of monokote and 1 black roll.

I also picked up 2 rolls of orange monokote, some EC-2 connectors and some epoxy to finish an old Aquila glider build. I haven't covered anything in a while, so my plan is to finish up the Aquila (which involves hooking up the spoilers) and cover its wings to scrape away all the rust my covering skills have collected.

 

[aeroncalover]

I would like to get a scale Sensenich prop for the cub. If anybody could sell me one that would be great. The recommended prop range is 11x7 to 14x10.

 

[willsonman]

With a power 32 on 4S I would go with the smaller prop diameters. For that specific prop you may have to scour some classifieds .