Flight Video is at;

https://www.youtube.com/watch?v=rDfcimUYEP8&feature=youtu.be


Flight Report below at post #47


Christmas is over and the forecast is heavy snow.
Good time to build something !

  My previous posts about building the
Cox Spitfire Replica and the Top-Flite
Form-Flite P-47 show my enthusiasm
for molded 1/16" balsa.  It's light , stiff,
crash resistant and straight forward.
  Check out those posts for the details
about molding.
The Focke Wulf 190D is a perfect subject
for this technique. I've decided to build a
stunter but a scale FW-190 would be even
easier.
 
  The first picture shows the concept
drawing and the plug.
  I have always found conceptualizing
with a pencil let's me think more freely
so since the fuselage is more sculptural
I just nail down the dimensions then
have fun making it pretty.

  Carving the forms to mold the fuselages
is simple.  I just use lots of pencil lines,
carve a little, then more pencil lines,
sand and more pencil lines.
Nothing fancy.

  Notice that the bottom of the plug is flat
and straight at the wing root. This gives
me a datum line so that I can set the
incidences at 0-0-0.
  The other thing I've learned is to
NOT cut out details like the cockpit and
wing/stab mounts from the plug.
It makes molding the wet 1/16" impossible.

  So the big deal here is the wing.
It didn't take much addition to realize that
a 1/2A stunter with 210 sq/inch wings
has to be super light if a Cox .049 is
going to pull it.
   Looking at Other designs (Thanks Larry!),
12oz. has to be the absolute maximum.
I have considered everything. Foam, Foam board,
traditional built up, Millennium, I-beam and even
(very briefly ) Coroplast.
What I have decided on is a molded "D-tube"
like a Nobler but without a traditional leading edge.
The picture says it all.

I used the "Blend" tool in Adobe Illustrator
to generate the NACA 15 wing ribs.
Just draw the root foil and tip foil and...
Push the button Max!

  A technique I have used constantly for many
years is to design everything in CAD and then
print it out and glue the paper to the balsa.
Keep the #11 sharp, cut to size then sand to
the printed outline.
  The parts I hand cut are amazingly accurate.
Everything fits together like magic.
The pictures show how the molded leading
edge fits accurately over the ribs and the
main spar. It is tight and straight!

  The trailing edge will be carbon rod salvaged
from Brad Lapoint's combat casualties.
God bless those Russians!

 

More to come..  - K

You mean to tell us you HAND cut each of those rib-lightening circles?

I'm sitting tight waiting for this one to be finished. If it is anything like the spit and P-47, this HAS.got to be good.

Subscribed!

Hey Mark.
  Molding the wing leading edge was
simpler than molding a fuselage.
  I made a mold out of 3/4" x 3"  pine.

  Cut it to length including the tip and
root angles then marked the center
lines and glue the paper foil outlines
on the ends.
Lots of effort to plane and sand it
STRAIGHT !

  Something interesting in the 1st picture
is how the computer generates the ribs
for a tapered wing. All I need to do is
draw the root and tip foils, specify the
number of ribs and let the computer do
the rest. It's dead accurate.

  Jim.  I do make the holes individually
but with a Forstener bit on the drill press.
I get a clean hole by cutting half way
through them flipping the rib over to
get all the way through.

Thanks for your interest guys!

 

 

Keith,

Thanks for the answer. I have a drill press, but rarely use it. I think it is going to see more use!

What software are you using to render the ribs between root and tip?

Thanks,

  Hey Doc, Thanks for that.
I value your opinion.
Skip's too!

  Part of the reason I'm doing this post
is because of the 1/2A Stunt at Brodak's.
( If it happens)
Maybe knowing the weights of these components
will be useful for other builders.

  The picture shows the "Gift Card" bell crank
I made for the FW190.
   It's 2-7/8" x 0.5" between holes mostly because
that span fits in the wing.
  I didn't scrape the graphics off the card this time
and I just sandwiched it between the two layers.
I did a test with CyA and it bonds the plastic well.
  These cranks are decently stiff and strong but
because this will be buried in the plane I took the
time to add bushings made from some K&S
aluminum tube. Probably wasn't necessary.
  The entire assembly with the axle and spacers
weights 2 gm - 0.1 oz.

  I'm very pleased with the wing.
Attaching the molded leading edge was straight
forward and it naturally wants to build straight.
  I was planning on using Carbon fiber rod
for the trailing edge but I did a test and, believe
it or not, the built up balsa box spar T.E. is lighter
and stiffer.
  The complete wing assembly including the controls,
gear mounts, adjustable leads and 0.2 oz of tip
weight is  49 gm - 1.7 oz.
That doesn't include more tip weight, LG legs or
any covering.
  I'll probably cover it with Polyspan.

  I am still amazed at how well molding fuselages
works.
  The pictures show the half shells clinging to the
plug and overlapping before I cut through them
both to get a tight seam.
  I haven't weighed them yet but they are very
light.

The stabilizer picture explains itself.

  As I'm building this I'm thinking that this plane
might be better with a tapered plug like the P-47
so that the fuselage could be finished still on the
mold. It wouldn't be as FW-190 but obviously this
design could be painted to look like anything.

Fun fun fun!  - K.

Nice job on the tank and motor mount. I like the idea of the forms. When I built a couple tanks, I just free-handed the bends and folds, and they looked nowhere near as nice as yours. Thanks for the ideas and tips.

That is what I need is the forms for end caps.   I like the engine mount.

I'm also loving the tanks construction, because there really isn't a great selection of tanks for 1cc and under, especially uniflow, and for a built up fuselage....

Do you think the TD will have enough draw for running on uniflow? I've heard not, and that the Medallions have a lot better draw. I would guess you could swap the TD piston and cylinder to a Medallion case and still have power mid-way between the two??
I plan to circum(uni)vent that problem by running the Big Mig .049/.061's on my 1/2A planes.

Please looks great.

R,
Target

Or You could make several kits, start a sign up sheet with my name on TOP!!

Thanks for posting your work, R.K.

  OK Guys.. Here is a picture post of
how I make tanks.
 The trick is making the wood form first.
It defines all of the dimensions.
  Making the end caps is ridiculously easy
too.

https://stunthanger.com/smf/12-a-building/metal-tank-making/

Hey RK.  Thanks for the compliment.

   I just use hot water from the tap and
let it soak for five minutes.
  How I mold the balsa is explained in detail here...

https://stunthanger.com/smf/12-a-building/top-flight-form-flight-thunderbolt-18'/

and here...

https://stunthanger.com/smf/12-a-building/cox-spitfire-replica-build-flight-video/

  There isn't much to it. Carving the plugs
could get complicated but I just draw lots
of pencil lines and use my little Stanley Plane.

Cheers!  - K.

Hello Larry,

  I mounted up the tank and the TD with
a 6-3 prop and ran it on 10% Richie's Brew.
It turned 15,500 and pulled hard.
  I waved it around and it kept running
for almost eight minutes.
  Of course, it might run different in the air.
I'm sure you've been down this path
more than once before.
I'm listening to you closely.   

   I'm making another metal tank and taking
pictures to explain how I do it.
I'll start another thread since it's a
long topic.


  A few pictures of the Focke Wulf.

To get accurate bulkheads measured off
the plug, I cut approximate holes in
cardboard and use tape to give a tight
measurement.
The picture says it all.

  I wasn't sure how I was going to join
the shells because the plug is a double
taper with no release angles.
It's much better to CyA the sides together
on the plug since it keeps everything straight.
  I put both shells on the plug and cut
through both together for an accurate seam.
then I glued the top seam completely
but only glued the bottom seam half way
from the tail.
  The plug slid out like a hen laying an egg.
Then I installed four bulkheads and the tank
from the front.
It's like building a ship in a bottle. 

More soon. - K

Hey Paul.

  I have several TD venturis. I'm going to try your
technique and narrow the bore and have it ready
if I need it.

   As the pictures show, I have the fuselage together
and Now I have to consider a way to install the controls.
  My plan is to insert the wing then cut open the cockpit
for access to the flap horns. That means I need a dead
simple way to link everything up.
   I started weighing material for suitable control horns
and all together it was going to be almost an ounce.
That's about 20% of the air frame so far. 
No way!

    I'm taking a small chance with these aluminum horns
and bushings. I did some destructive testing and they
seem to have enough torsional strength  but I'm not sure
about fatigue and bearing wear.  It seems reasonable though.

  A funny thing is that I once met an old German machinist,
Herr Hippe, who told me about making controls for FW190's
in 1945. In better times FW190's had ball races in the control
linkages but by 1945 the life expectancy of the plane was
so short that young Herr Hippe was just machining them out
of bare aluminum.
Life is a funny old thing.

  My plan is to use JB-Weld to allow me to slide the rods
and center the controls. I need to get it right the first
time so wish me luck.
It's like building a ship in a bottle.
 

Cheers! - K.

If I am seeing correctly, you have the aluminum flap horns running in aluminum bushings.Bad potential for galling and seizing. The bushings should be brass or steel!

I would not worry much about fatigue of the aluminum horn. I would worry about the contact stress where it contacts the clevis pin or pushrod. The contact area is small, and aluminum that you likely are using does not have much strength. (If it was real high strength, you wouldn't be bending it like that, or hammering it flat.) Hopefully the wire is pretty hard, but if you fly it much, it may wallow out from excessive contact stresses in bearing. (That's what engineers call that type of applied load.) You probably are using K&S tubing (alloy 3003-H14), which has poor galling resistance. If you use a Sullivan clevis with gold plating, the gold may save you from galling, as it is excellent. But not from deformation from exceeding the yield strength of aluminum from bearing stresses.

If the horn and your aluminum tube (journal bearing) are lined up really well, so that the load is well distributed, I'd gamble that it will work out. Your odds go up if the materials are harder, because galling (metal transfer) occurs earlier with softer (more ductile) materials.

You might consider lubricating this with something like Tetra or Break Free synthetic gun oils. Even a "wipe on, wipe off" treatment using a silicone grease is better than no lubrication. I think a thin film would be helpful.

Nice project--thanks for sharing it with us!

Dave

  It's blowing a hoolie out there today.
Probably 35 knots and gusting with
heavy snow. I should have two anchors
to windward to keep the house from dragging
through the anchorage.
 

  Nice weather for building.

  Assembling the controls was good practice
for a future career in bomb disposal.

   I usually take a full day to get the controls
into a stunter, but this little plane has been
a new experience.
Sixteen hours to set up the controls using
tweezers and swearing. 
  I am happy with the result. Everything is
adjusted and smooth. Hopefully sealing the
hinge lines won't stiffen them up.

  The pictures show the plane complete
except for fuel line and wheel retainers.
With three coats of Butrate it weighs
exactly 8oz.
  The covering is Polyspan.
  I think I should be able to decorate it
and still keep it under 9oz.

Cheers! - K.
 

 

That looks just awesome. If one day I could ever build like that, I would leave it as it sits to show off the great craftsmanship! Thanks for the update.

Dan is a big guy, that plane is HUGE!

    I'm very happy with the final weight and
balance.  Bench trim is just a trifle nose heavy
and I might have a smidgen too much tip weight
but good enough until it has flown.

Final weight as shown but dry is 8.8 oz or 248 gm.

 I'm happy with the weight and I'm sure the
TD.049 will pull it, but it might be just a little
too much for a product engine.
I will experiment with high compression heads
and nitro. It might work.

Looks nice and I bet looks better in color.   I remember when Don Still went over seas to compete in the World Championship he had his Stuka in a white color and no swatiska's.  Some people never forget what the symbol stood for.

Hey Doc ,
 
  Yup.  It's like looking at pictures of
Neil and Buzz on the moon. The Kodachrome
film picked up absolutely no color except
the Flag. 
   I put the plane on the snow for the pictures
because it makes it look extra bleak.

   I know it's illegal  in Germany to have
swastikas on anything, even planes in
museums.  I think I can understand that,
but......

 Chauncey,
  It's good to see you building. I have a
Jr. FliteStreak that I'm refurbishing and the
only appropriate engine I have is a Fox .15.
It's equivalent to your Jr Ringmaster.
I'll let you know how it goes.

   What's next? 
I think I have enough 1/2A's for now and
a big part of the reason I built the 190 is
to try some more advanced balsa molding.
  I have been slowly adapting these techniques
for my full size stunters to mold turtle decks,
cowls and fuselage bottoms, but I want to
try fully molded fuselages.
  I use 1/2 oz glass and epoxy over molded 1/16"
balsa and it's very stiff and fuel resistant.
These planes have a Ro-Jett .65 and a .67
up front and the molded parts take all that
power nicely.
   Most of the top guys near me fly Yatsenkos
since they focus on the FAI Worlds.  Anyone who
is remotely serious has to have a serious plane.
My goal is to build my own.

(and learn how to fly it. )

Cheers! - K.

 

Can i ask if you have pics of the wing mounted main gear?
Is the wire attached to a spar, or a platform running between ribs?
If the latter, are the ribs reinforced?
If so, with 1/64th ply?

Thanks in advance.

R,
Target

What advantage is there to using a td on suction vice using a td top end on a Medallion case/crank?
Is the power difference going to be that noticable, if you have to choke down the venturi on the td to get a similar draw, anyway?

R,
Target

Hello Ken,

   Thanks for your thoughts on the TD.
Obviously you know more about them than
I do.
  My TD is dead stock but fresh.  I checked it
with the tank on a test stand and waved it
around. It seemed OK and ran over seven minutes.
With a 6x3 prop it turned 15,500 rpm on 10% nitro.
I am amazed how hard it pulls.

  Larry is suggesting a Medallion crank for
a stunt friendly run. I am keeping that option
open since the cranks are cheap and available.
Will I also need the red plastic Medallion venturi ?


  I have several TD venturis to work with, so I'm
going to use aluminum tube to sleeve one down
as Paul Smith suggests. I have a set of index drills
to measure and adjust the bore.

   I suspect TD's were designed to be high performance
Free Flight engines. I'm going to try running them like
a modern piped engine. Let them spin and be happy
and I'll use flat props to soften the effects.
 

Cheers! - K.

          Chris, Paul like Keith is a very experienced builder and partakes in many events. He mentioned 1/2A scale and for that you probably are not in need of a engine as powerful as the TD. Necking down the venturi calms the engine down and improves fuel draw which is what is desired. More than likely uses them due to what he has on hand. It's always better to have more power than not enough as it's easier to tame a engine down vs extract more power. Seeing that the Medallion is a single ported cylinder, I would expect even a choked down TD is still going to offer more power. Many years back I recall Tom Hampshire using a TD with a Medallion carb body on a Scout. I have to say it was a jaw dropping flight as that plane just impressed all of us standing there. A very worthy flying plane with a terrific engine run made entirely from a bunch of pieces he had laying around. To date, I believe Tom still has this plane and I would love to see him fly it at Brodak's.

         I have seen the discussions on here and another forum in regards to switching and mismatching parts on the TD and Medallion. I have several of both and I would prefer not to do that. More power can be extracted from the Medallion with a high comp head, Sure Start cylinder, etc. The TD though in my opinion can be made to work quite well, Keith's suggestion of letting it wind up or adding more head gaskets, I personally wouldn't address fuel draw prior to seeing if it's a problem and go from there.

Congratulations on yet another awesome project completed.  Wish I could see the model fly. Maybe get some video?

By the way, my Skysport is 190 sq. in, no flaps and 10.5 oz. It flies just fine through a competitive pattern on 38' lines. You have a LOT of margin of performance by comparison. I also have a Baby Nobler at 165 sq.in. and 11.5 ounces. With flaps it turns great. (Sadly it has a simply awful control setup and is a demon to fly)