Sig 1/4 J3 Kit converted to PA-18 Super Cub (Build)
#78
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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.
SunDevilPilot<br type="_moz" />
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.
SunDevilPilot<br type="_moz" />
#80
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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.
SunDevilPilot<br type="_moz" />
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.
SunDevilPilot<br type="_moz" />
#82
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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
Still needs a little sanding but I am really happy with the outcome.
SunDevilPilot
#84
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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
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
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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ORIGINAL: Zor
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
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
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
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.
SunDevilPilot<br type="_moz" />
#86
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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.
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.
#87
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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.
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.
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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#88
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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
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
#89
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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.
SunDevilPilot
SunDevilPilot
#90
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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
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.
#91
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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.<div></div><div>The biggest modification to the elevators is the addition of the counterbalances.</div><div></div><div>SunDevilPilot </div>
#93
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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
I know that the laminations were laid up after soaking in water. What did you use for glue?
Joe
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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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
Joe
I made the call 1/4 scale Cub will not be available until mid-November
Joe
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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.
SunDevilPilot<br type="_moz" />
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.
SunDevilPilot<br type="_moz" />
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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.
SunDevilPilot<br type="_moz" />
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.
SunDevilPilot<br type="_moz" />
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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.<div></div><div>SunDevilPilot</div>
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.<div></div><div>SunDevilPilot</div>