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Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

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Old 08-10-2010, 01:39 PM
  #76
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Door brace removed.....
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Old 08-11-2010, 11:11 AM
  #77
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Nice job, I can see this is the beginning of a happy Cub. ... neat work congrats.

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Old 08-14-2010, 10:42 AM
  #78
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

One of the more distinct differences between a J-3 Cub and a PA-18 Super Cub is the tail. The rudder and elevators have a different shape. To redesign this into the model I went onto Supercub.org and downloaded some of the plans for the tail of the real Super Cub. I resized them to match the full scale plans for the model and will be making a template out of wood to bend the perimeter framing wood around. I am going to laminate small strips of balsa around the form to create the moving portions of the surfaces. The fin of the rudder will be build stock as will much of the stab minus the counterbalances.

I have never tried building a tail in this method so hopefully it works out. The laminating portion of the firewall went well and produced an extremely strong part.

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Old 08-14-2010, 10:43 AM
  #79
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

On the plans....
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Old 08-15-2010, 08:33 PM
  #80
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Here are my thoughts on the rudder.

Laminating strips of balsa around the form was easy enough. It definitely takes a little more time and effort to laminate a part than building one out of balsa chunks cut to shape but I am finding it somewhat rewarding. Having never done this before, aside from the curved firewall part, I am really happy with the progress. I ended up doing it one layer at a time mostly due to the speed at which the glue dries. In the desert the water in the glue really evaporates quickly. Pre-soaking the strips, bending them around the form, and allowing them to dry before gluing the parts did help. It really made the parts bend easily once the glue was applied and I feel it reduced the likelihood I would snap one of the strips.

The form is some MDF with packing tape applied to the glue edge to prevent sticking / water penetration onto the form. The form was made smaller by 3/8" where the laminated part will be.

I really believe in the phrase, "You can never have enough clamps" now.

I drew the rudder outline on the form to make sure I clamped out far enough to keep the portion I will use straight and fully compressed.

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Old 08-15-2010, 08:36 PM
  #81
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

A second angle....
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Old 08-16-2010, 08:33 AM
  #82
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Got up this morning and pulled the rudder from it's form. The process worked! The tape prevented the glue from sticking the rudder to the form and the lamination slid off after the clamps were removed. The part did not change shape as the clamps were taken off so it looks like I will use this method for the elevators.

Still needs a little sanding but I am really happy with the outcome.

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Old 08-16-2010, 12:16 PM
  #83
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Beautiful work there!
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Old 08-16-2010, 06:05 PM
  #84
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)


Quote:
ORIGINAL: SunDevilPilot

Got up this morning and pulled the rudder from it's form. The process worked! The tape prevented the glue from sticking the rudder to the form and the lamination slid off after the clamps were removed. The part did not change shape as the clamps were taken off so it looks like I will use this method for the elevators.

Still needs a little sanding but I am really happy with the outcome.

SunDevilPilot
Hi Sun ____

You are a nice example of what is so attractive in this bobby. Do what we want the way we want it and succeed beautifully. Congratulations.

You are on your way to a beautiful model.

Zor
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Old 08-17-2010, 01:29 PM
  #85
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)


Quote:
ORIGINAL: Zor


Quote:
ORIGINAL: SunDevilPilot

Got up this morning and pulled the rudder from it's form. The process worked! The tape prevented the glue from sticking the rudder to the form and the lamination slid off after the clamps were removed. The part did not change shape as the clamps were taken off so it looks like I will use this method for the elevators.

Still needs a little sanding but I am really happy with the outcome.

SunDevilPilot
Hi Sun ____

You are a nice example of what is so attractive in this bobby. Do what we want the way we want it and succeed beautifully. Congratulations.

You are on your way to a beautiful model.

Zor


Thanks a lot for the compliment Zor. I really enjoy the building process. If there is a new process out there, and I think I can do it, I will try to incorporate it into my models. With each plane I build I obtain new techniques, some may work some may not. A long as I can keep learning the build process stays fun.

In a world of "Need it now" I choose the slower path. I don't need a lot of planes just a few good ones.




Here is the initial build of the rudder. I built on the plans but used them for more of a guide than anything. Because the rudder's outer perimeter was already set by the lamination process i just had to fill it in with the structure. I will be adding some more structure to the lower portion of the rudder for the control horn hard-point. I will be using a pull pull cable so most likely I will use the Dubro Heavy Duty hardware. I will also be adding some blocks for the hinges, Robart style, which I already pre-drilled the leading edge of the rudder for.

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Old 08-17-2010, 02:10 PM
  #86
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

When you build the wing tips, you will find that they are laminated too on the Sig 1/4 size Cub. In that case, however, the form around which they are constructed becomes a part of the finished wing.

Very easy to do and very strong, as you will find your tailplane pieces to be with the laminated outlines.

Don't forget when you install your pull/pull horn on the rudder for the cables, you need a separate horn which attaches to the bottom of the rudder - not the sides - for the steerable tailwheel. It sticks out and curves down on each side.

Keep up the great work.
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Old 08-17-2010, 02:39 PM
  #87
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)


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ORIGINAL: do335a

When you build the wing tips, you will find that they are laminated too on the Sig 1/4 size Cub. In that case, however, the form around which they are constructed becomes a part of the finished wing.

Very easy to do and very strong, as you will find your tailplane pieces to be with the laminated outlines.

Don't forget when you install your pull/pull horn on the rudder for the cables, you need a separate horn which attaches to the bottom of the rudder - not the sides - for the steerable tailwheel. It sticks out and curves down on each side.

Keep up the great work.
Funny you mention to not forget about the tailwheel horn...Been there! However, I did come up what a little innovation to work around the forgotten tailwheel horn. On my 29% Edge I forgot to add a hardpoint to the rudder for a horn to control the tailwheel. So I came up the a simple solution and have used that solution of several planes. When I run the pull pull cable for the rudder I ran two cables to each side, one for the rudder and one for the tailwheel. Because I am planning this in advance I will be adding two extra guide tubes to the rear specifically for the tailwheel pull pull cables. On my 1/5th Scale Sig Cub I ran the cables through the same tube and was extremely lucky the cables missed the tail supports on the lower side of the elevator. To completely eliminate this possibility I will put the guide tubes for the tailwheel exiting down low, under the tail supports, and a pair for the rudder's cables up high.

Here is a photo of the setup on my 1/5th scale cub. The tail support wires are not installed in the photo below but they attach to the bolt visible between the cables. Works great and can be easily adjusted to get good tracking while taxiing.

SunDevilPilot

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Old 08-17-2010, 02:54 PM
  #88
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Do335a,

I believe this is the arm you were describing. I took the photo of the assembly on an Aeronca Champ at an "Open House" a local airport, Falcon Field.

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Old 08-19-2010, 08:03 PM
  #89
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

I still need to do the final shaping of the nose but at least I have it all boxed in, attached the floor onto the nose section today. The supplied piece of balsa gave no margin of error so I took my time to ensure I got it right. Attached with some epoxy.

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Old 08-19-2010, 08:54 PM
  #90
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)


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ORIGINAL: SunDevilPilot

Do335a,

I believe this is the arm you were describing. I took the photo of the assembly on an Aeronca Champ at an ''Open House'' a local airport, Falcon Field.

SunDevilPilot

That's exactly the idea. The Super Cub uses the same arrangement as the Champ. And when you install floats, the cables to drive the water rudders are connected to that same horn.
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Old 10-19-2010, 12:06 PM
  #91
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

I was really happy with how the rudder came out so I decided to use the same method for the elevators. So far I have soaked the wood for a few hours and clamped them to the form for the "Pre-Bend". After they dry I will taken them off the form, add the glue, and do the final lamination.
The biggest modification to the elevators is the addition of the counterbalances.
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Old 10-26-2010, 06:41 PM
  #92
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

I know that the laminations were laid up after soaking in water. What did you use for glue?

Joe
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Old 10-26-2010, 06:59 PM
  #93
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)


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ORIGINAL: Lowvoltage

I know that the laminations were laid up after soaking in water. What did you use for glue?

Joe
After the wood was "Pre-Bent" by allowing the water to more or less dry off I pulled the parts from the former. About 80 percent of the shape will be lost as the parts come off the form but thy will not crack when re-applied to the form with the glue applied. I applied some standard wood glue to the laminations, about three at a time, and re-clamp them to the former. I allowed the glue to set then added glue to the next few layers and added them to the ones already set on the form. At that point I let the completed lamination cure on the form overnight.

The quick answer to your question is standard wood glue (In this case Gorilla brand wood glue) applied to dry formers.

Hope this clarifies the process,

SunDevilPilot

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Old 10-26-2010, 08:25 PM
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Thank you for explaining the process. I thought if you were using regular wood glue at the onset of the laminating you might lose some bonding strength, but now I understand that is not the case. Nice job! Keep up the good work. I don't know if Sig has any Cubs at the present, but it is very tempting to make a call.
I made the call 1/4 scale Cub will not be available until mid-November

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Old 10-26-2010, 08:28 PM
  #95
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Cub is looking good! Looking forward to the finish product.. Keep up the great work.

Rob
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Old 10-27-2010, 07:18 PM
  #96
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Was able to create both laminations for the elevator halves and get both elevators assembled. Method was the same as the rudder, pin the parts to the plans and use the plans as a rough guide for the cross braces. All parts cut long and fitted using my disc sander. I pre-drilled the holes for the robart hingepoints into the elevators leading edge prior to assembly. Drilling them before installation makes it simple to get perfect holes. I use the Robart drill jig and my drill press.

Next up is the stab for the elevator then I will made the stab for the rudder.

Like the rudder, I will be adding some wood towards the center (Fuselage) of each part for the control horns to go into. This will be done when I figure out where exactly I want the horns to go. Most likely Dubro Heavy Duty hardware into hardpoints in each surface.

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Old 10-29-2010, 01:25 PM
  #97
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Originally I was going to use the stock stabilizer parts from the kit but I decided cutting the parts from the printed balsa sheet, fitting them, and gluing it all together was more work than making a template and laminating the leading edge. So.... Here is the leading edge of the stab drying on the form.

I should be able to build the stab in a few hours after the part is totally dried. Unlike the rudder and elevators I did not need to soak the wood in water to pre-bend it. The stabs curve was gentle enough to just glue it up.

The form is an inch wider than the part on both sides allowing a clamp to be placed right up to the edge of the actual leading edge ensuring a good glue joint throughout the lamination.

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Old 10-29-2010, 04:00 PM
  #98
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)



Woodworking skills are an unfair advantage over your fellow modelers!

Keep up the good work! :P

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Old 10-29-2010, 06:54 PM
  #99
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Thanks Amish Warlord!

Completed the stabilizer today. Built per the plans using my laminated leading edge. Fortunately I was able to use the ink printed center sections for the stab. The only modification I needed to do was trim the part a little longer than stock to allow for the thinner leading edge lamination.
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Old 10-29-2010, 07:34 PM
  #100
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Default RE: Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)

Like a Swiss Watch, the joinery is beautiful. The sad part is that after it gets covered no one will know.

Joe
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