Building a Scratch Built Cub

stknrddr said:

A photo of the stabilizer leading edge tube in the fixture.

View attachment 31960
Bending the heavy tube required making a bending fixture as shown.
I inserted a coil spring into the tube, and using the cupped fixture, the tube bent nicely without kinking.
Don't forget to remove the internal spring if you elect o do this.

Click to expand...

This is really great. What kind of spring did you use?

I looked up springs for tube bending but only find 24" coiled springs from Wicks. It looks like your curves are a lot longer than that.

The springs I saw have flares at the end, presumably so they didn't slip too far inside. Did you cut them off or find something better to use?

RVBottomly said:

This is really great. What kind of spring did you use?

I looked up springs for tube bending but only find 24" coiled springs from Wicks. It looks like your curves are a lot longer than that.

The springs I saw have flares at the end, presumably so they didn't slip too far inside. Did you cut them off or find something better to use?

Click to expand...

filling it with sand and capping ends will probably work also...

see my video on making breather tubes

RVBottomly said:

This is really great. What kind of spring did you use?

I looked up springs for tube bending but only find 24" coiled springs from Wicks. It looks like your curves are a lot longer than that.

The springs I saw have flares at the end, presumably so they didn't slip too far inside. Did you cut them off or find something better to use?

Click to expand...

The spring is simply an extension spring with the ends cut off. I happened to get lucky in that I had this spring laying around, and it fit just right, and made a sliding fit into the tube, matching the inside diameter of the tube nicely. I have bought springs for other purposes from McMaster-Carr ( Industrial Supply Company), and the choices are many. A person can buy directly from them using their online catalog. In this case, I pushed the spring well into the tube and made the bends, then kind of shook the spring out. In the event the spring might have gotten stuck, I was sure that I could have pushed the spring out using a flexible hose or something.

Made my breather from siphon tube. You know
one of them irrigation things.

​Project Update - Turtle Deck

This is an update of fabricating and placing the turtle deck section on the fuselage.


I temporarily attached the sample wings I made onto
the air frame. This was done to properly locate the 3
turtle deck stringers at the trailing edge of the wings.


I c-clamped the wing fittings as shown, as I do not want to weld the
fittings in place until I have the final wings fabricated to ensure
better alignment of the wings to each other and to the fuselage.

In the above photo, you will also see a formed wing cap strip setting
in place. We fabricated our own piper channel using 0.025" thick steel
sheet, 1" wide. A shear and break were used to bend it into a channel.


I fabricated a fixture to bend an arc in the piper channel to the shape
of the airfoil. I routered a square groove into the edge of a radiused
section of fiber-board, fabricated a steel cap to retain the channel,
and kind of bent the channel around the radius, moving the channel as needed.



I then used the original wing rib fixture to match the airfoil
shape for the steel cap strip.


I fabricated the stringer bulkhead station located in the tail section.
then ran string lines to the trailing edge of the wings. The string lines
represent the final located of the stringers.


The location of the strings and ultimately the stringers is
important to ensure the fabric lays in-line with the
cabin windows.


We needed a way to copy the shape of the future bulk head
stations, so a friend of ours made this plywood bevel square
contraption using a laser cutter. Slotted holes and wing
nuts make it easily adjustable to get the correct shape
around the strings.


Transferring the bulkhead shape to a work bench,
by tracing the interior perimeter, provided a set
of lines to follow when welding up the bulk head
stations.


Here's one of the bulk heads getting fabricated.


Here we have two bulk heads welded in place, with
the bevel square thing setting in place for the next
location.


I cut and fit the parts, and Charlie does the welding.
Here he uses a 0.040" tungsten for the thin parts
instead of his usual 1/16" tungstens.


This is the last bulk head location. The process
we used to locate and align the bulk heads worked
very well for us.

Thank you for looking. John

Very nice.

That plywood bevel square is similar to a plywood gauge I put together for making boat frame patterns. Yours is more elegant, though.

BTW, I'm taking notes and stealing ideas. Thanks for putting these up.

stknrddr said:

​Project Update - Turtle Deck

I fabricated the stringer bulkhead station located in the tail section.
then ran string lines to the trailing edge of the wings. The string lines
represent the final located of the stringers.

View attachment 34032
The location of the strings and ultimately the stringers is
important to ensure the fabric lays in-line with the
cabin windows.

View attachment 34033

Thank you for looking. John

Click to expand...

John, You are doing excellent work. Are you intentionally relocating the center top fuselage stringer to be different than Piper's? The forward end of the top center stringer passes above the rear spar carry through, not as you have it in line with the wing trailing edge.

Excellent work John, as always!

John, You are doing excellent work. Are you intentionally relocating the center top fuselage stringer to be different than Piper's? The forward end of the top center stringer passes above the rear spar carry through, not as you have it in line with the wing trailing edge.

Click to expand...

Yes, I see what you mean. The center string line is actually above the trailing edge, but a person can't really tell from the photos. I've been on the fence about how tall to make the center peak through this area, as it is flatter than by the plans. If I elect to extend the sky-light farther aft, I do not want to have to put a crease in the lexan (or whatever I use), or at least not a significant crease, and I realize that a crease may help stiffen up the lexan for the better. I noticed on one of the experimental Cubs that I often look at included a little stand off to raise the stringers a little higher than the corners or peaks of the bulk heads, and I thought I could resort to that if I want to raise any of the stringers. My corner stringers are for the most part, headed right toward the trialing edge, however I have left opportunity to flex the stringers upward to fair into the trailing edge as well.
Thanks for your thoughts as I would hate to get too far down the wrong path.

I have a skylight on mine made from plexiglas. I bought a heat tape which is a little over an inch wide to heat where the crease in the center goes. There are also two reverse creases which goes from the forward center diagonally towards the wing trailing edge. This method works very well though there is a learning curve in using the heat tape.

Golly! Didn,t know a kit can be made. You are a true airplane builder.

skywagon8a said:

I have a skylight on mine made from plexiglas. I bought a heat tape which is a little over an inch wide to heat where the crease in the center goes. There are also two reverse creases which goes from the forward center diagonally towards the wing trailing edge. This method works very well though there is a learning curve in using the heat tape.

Click to expand...

Agreed. I did that with my full-door plexi. Just make a form that will allow the plexi to settle by gravity to the desired shape, put the the tape where the bends are, plug it in, and have a cup of coffee while the plexi settles into position.

Gordon Misch said:

Agreed. I did that with my full-door plexi. Just make a form that will allow the plexi to settle by gravity to the desired shape, put the the tape where the bends are, plug it in, and have a cup of coffee while the plexi settles into position.

Click to expand...

You can do it without the heat tape, just lay something on either side to block the heat like 2 yardsticks half an inch apart and heat the gap with a heatgun where you want the bend. Practice on some scrape first

Glenn

Gordon Misch said:

Agreed. I did that with my full-door plexi. Just make a form that will allow the plexi to settle by gravity to the desired shape, put the the tape where the bends are, plug it in, and have a cup of coffee while the plexi settles into position.

Click to expand...

Don't leave the heat tape on too long! Don't sip that coffee. :evil: Too long can make marks in the surface or depending on your form shape it can over bend.

Yep, just long enough to achieve the desired shape. Maybe the coffee should be a small cup - - -:roll:

stknrddr said:

Lunch Time Aviation - Project Update



View attachment 31988
A photo of a piece of scrap plywood in place just to see what it looks like.
I have not decided what to do for the back of the baggage compartment.
Maybe I'll install tabs to attach a similar plywood sheet, or install
a canvas style back; or the lower half of the back may be plywood,
while the upper half is canvas?
Any thoughts and photos of options are appreciated.

Thank you,
John

Click to expand...

john, I'm really enjoying your progress reports, you're a true craftsman.

re rear baggage: i ended up going with .050 alum and added a couple stiffeners, I have an underseat storage tray and Atlee "safari seat". The center underseat storage "hatch" has since been fitted with piano hinge. Had the surface powder coated with a textured finish for non skid effect. Holding up well.

Project Update - Ribs and Spars
I am beginning to think about wing assembly, and I have placed
a set of my scratch built ribs onto a set of spars. But first,
a quick update on my turtle deck and stringers.


The three stringers are now in place. Pulling 3 string lines,
and fabricating the bulkheads (stations) to the strings worked well.
The stringers shown here are currently clamped to little saddles welded
onto the bulkheads in the above photo. The stringers will later
be pulled riveted to the saddles.


The photo above is a saddle used to cradle the stringer in place
on the bulkheads. The saddle is made from a piece of steel tube.
The saddle gets welded to the bulkhead, and then the stringer gets
riveted to the saddle. I needed to add a little spacer to the bottom
of two of the saddles to ensure the stringers were nice and straight.
All other attachment points for the most part were perfect.
We are using aluminum tubing for the three stringers on the turtle deck.
It's light in weight, has a radius for the fabric to wrap nicely around,
and could be bought locally at our local steel supplier (no shipping charges).
We used 6061-T6 Aluminum Tubing, 1/2" diameter, and 0.049" wall thickness.
The bulkheads are 18" apart on center, and it appears that the tubing will
be stiff enough, pending control when a person shrinks the fabric, not to
distort it.


The photo above shows the saddle welded to the bulkhead,
and the stringer cradled onto the saddle, followed by a couple
of pull rivets later.

Rust Prevention

We use a light oil (air tool oil because it was handy) to prevent rust,
as rust tends to develop first on the welds, and later on the tubes.
We lightly wire brush any areas where rust is forming,
then coat the clusters and lightly coat the tubes as needed.
The entire fuselage will be cleaned prior to paint.




Ribs and Spars

It's pretty cold here in Wisconsin these days and my shop is not heated,
where I am working on my wings, so I can only make small progress
on my wing assembly. I can do enough in my cold shop to at figure out
what I have to either fabricate or purchase to continue.



Here's a photo of my ribs set on my spars. My friend Charlie
who is also building his own scratch build SuperCub with me,
picked up these 24 gallon wing tanks. He found enough for
two sets of wings. We'll need to pressure test them. We
bought the spars from Javron located in Brainard, Minnesota.



I built a one piece rib for quick and easy assembly.

I plan to fabricate the compression members (drag struts),
however I can not fabricate the drag and anti-drag diagonal wires
due to the threads needing to be rolled (not cut). I'm on the look out for two
sets of wires, new or good used sets.

My next step on the fuselage is to fabricate the upper doors (windows),
as the fuselages are located in a warm shop. More to come as these develop.

Thank you for viewing, and Happy New Year on this January 1, 2018.
John

Nice work Oliver.

I agree. Looking very good.

SuperCub Sunday Progress


The following shows progress on my Upper Doors:

I'm going with swing out Upper Doors on both the right and
left sides of the fuselage. To fabricate the Upper Door frames,
we rotated the fuselage onto it's side, and clamped a flat board
flush to the outside of the fuselage. By the way, I'll install those
little flip out window vents on each side, so we won't necessarily
have to require on opening the upper door to get some air,
as a lot of wind will come in when the upper door is opened.


I used plywood spacers to dictate the gap between the Upper Door
frame and the fuselage tubes, and cut and fit the tubes as shown.


Steel blocks were used to hold the tubes in place during the cutting,
fitting and tack welding process.


The Upper Door was removed from the fixture for finish welding.


Here's the Upper Door clamped in place to check the fit.


I want the Upper Door to be flush to the outside surfaces
of the fuselage, so small boards were clamped to the
outside of the fuselage, then the Upper Door Frame was
clamped to the boards. After the door is positioned correctly,
the hinges can be welded onto the door frame.


A piece of piano hinge is cut to length and placed as shown.
The hinge will be permanently welded to the door frame,
then either riveted or screwed to the cross member
(nut plates required) on the fuselage. The hinge gets tack
welded to the door frame in place as shown above.


After tack welding, the door frame is removed,
and Charlie finish welds the hinges.


Here's a photo of the hinge on the other end of the
Upper Door frame. I think I can now start to consider to
weld the "D" shape window frames onto the fuselage, and
figure out how to trim out all the way around the door
opening for a positive stop and for gap sealing.

Engine Selection - People ask me all the time "what engine?".
I appreciate all the engine discussions on this site, and I
read them all. With the understanding that I want to keep
this plane light, and without flaps, I hope to find a C-90.

Thanks for looking, and I appreciate the feedback.
John

These can be verified directly with the builders so no smoke and mirrors. Factual information and real numbers will be used to verify everything on this forum page. Many get aggressive when actual real life comparisons are made and would rather post ambiguous information that never lead to a conclusion. Viking believe that comparative, real world data is useful.

• Patrick's Corvair to Viking 130 change = +/- 2lb weight change
• Richard Jones Corvair to Viking 130 change = +/- 2lb weight change
• Roger Grable's Corvair to Viking 130 change = +/- 2lb weight change
• Jon's O-200 to Viking 130 change = +/- 2lb weight change

Conclusion:

• The Viking 130, installed and flying has the same weight as the Corvair and the O-200
• The Viking has 30 more hp than the 100 hp engines it replaced
• The Viking has over 250 lb of additional thrust, above any of the replaced engines.

https://www.ebay.com/itm/232674701340 Just a thought is all, absolutley no more is meant.

tempdoug said:

https://www.ebay.com/itm/232674701340 Just a thought is all, absolutley no more is meant.

Click to expand...

That engine is listed under outboard engines, no reserve. Someone is asleep at the controls as they list the price on their website at $9995

NoCub said:

That engine is listed under outboard engines, no reserve. Someone is asleep at the controls as they list the price on their website at $9995

Click to expand...

Maybe, maybe not. Price in the end will tell the game.

Man congrats on the fine craftsmanship. I just decided to start a scratch build myself. I have the northland plans and am currently going through those . I have a couple of questions for ya . What and where did you get your plans? And what’s your material cost so far , just the fuse and wings ? Thanks I can’t wait to see your finished project.

This will be super helpful to me . Right now I’m trying to go through all the drawings and filter out what I need and what I don’t. I’m going to put a mock up together in solidworks first , because I’m planning a few modifications I think it will be easier than trial and error. I’m 6,7 220 so I want a little more leg room , I want easy access to the baggage. Just some small stuff like that . I also will be doing a Fowler type flap and some leading edge slats on my wings . As a machinist and a journeyman fabricator you guys did top notch work on your builds !

for a 0-200,A tip over cessna 150 about 70 miles from me just sold for $300 complete.

Scratch Building Update - Trim Tab and Baggage Compartment Door Opening Frame



I elected to fabricate a traditional trim tab on the left elevator.
For the lack of a better term, two little spars are needed at the hinge
locations for the trim tab. I used 0.025" thick 4130 sheet to form
the spars. One of the elevator ribs needs to be cut away
(at the center of the trim tab) to slide the spars into place.
Two short ribs are added at each end of the trim tab, and
everything is welded in place.



Two additional ribs are added to the trim tab to
stiffen it up. If a person wants to simply attach a
piano hinge to the upper surfaces of the tab and
the elevator, now is the time to it before the tab
is cut away from the elevator. I will likely attach
the hinges to the inside surfaces of the tab and
elevator spars to hide the hinge better. After
cutting the tab away from the elevator,
final welding can be done, and the horn to actuate
the tab can be welded in place.





A small baggage door will be included on the right
side of the fuselage. Here, I formed up the bottom
edge of the door opening frame using 0.025: thick
4130 sheet steel. I rolled the edge over and bent a
little flange on it to stiffen it up, then cut, fit and
welded it into place in line with the stringer.
An aluminum piano hinge will be riveted to this piece
and attached to the baggage door.



Small pieces of "C" channel were fabricated, then cut and fit
into place as shown. Prior to welding, I primed the
upper longeron and the inside of the upper baggage door
frame member. 90 degree magnets were used to square
up the parts prior to welding.



The final door opening size is 10" high by 16" wide.
This door frame system appears to be plenty stiff
enough to maintain its shape after the fabric shrinks
around it.

I think my next step is attaching the stringers and
fabricating a control lever to operate the trim tab.

Thank you for looking.

John

Know of a O-200 fr sale. Was on a flying eurocope that hanger fell on. Think it ran good.