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Author Topic: Top Flight Form-Flight Thunderbolt 18"  (Read 494 times)

Offline goozgog

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Top Flight Form-Flight Thunderbolt 18"
« on: April 16, 2018, 12:15:51 PM »
   This build is an extension of my molded balsa replica of a
Cox plastic Spitfire, so it might be worth looking at again.

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

   The Top Flite molded balsa 1/2A kits were the "other" planes
we kids flew instead of Muscianos  They were called Form-Flight
by Top Flite. They featured a molded balsa fuselage and wing
that was reasonably easy for kids to assemble. The line
included a Hellcat, a Zero and the Thunderbolt.
Information about these planes is scarce.
Until now.

Here is my previous thread looking for information.

https://stunthanger.com/smf/12-a-building/12a-top-flight-molded-thunderbolt-zero-ect/msg106092/#msg106092

  For some reason, the P-47 I had as a twelve year old has
been in the back of my mind recently. The weather has been horrific
this weekend so in a fit of boredom I was wandering through Ebay
and VOILA! The vendor of this original kit is asking $165.00 for it.
WAY beyond my reasons for having one but they are displaying
very good pictures of the kit parts. More than enough to design
an accurate replica.

   As you can see from the pictures, the big deal here is molding
the fuselage. The technique I used for the Spitfire worked brilliantly
and this  P-47 is a much easier design to consider.

   The first thing to do was to trace the outlines from the Ebay
pictures using Adobe Illustrator.  This was the usual problem of
straightening the photo parallax and averaging the bulkheads.
I know the span is 18" so I used that as a base measurement.
 I'm sure that I'm very close with the other sizes but the printed
outlines on the balsa kit are inside the die cuts by about 1/16".
Lots of fiddling to get the plans to the cuts. Not the ink lines.

   I printed out the "plans" full size on 8-1/2 x 11" paper and
used them to carve a pinewood plug to mold the fuselage.
  Getting the shape to match the kit was easy since Top Flite
simplified the shape. It's simple and symmetrical.
  Obviously they used this same fuselage for the Zero.
So, this was a very slim P-47 or a slightly tubby Zeke!

  Flying season is upon us so progress will be slow, but I
will try to post pictures of each step.
If anyone is excited about this plane, I could mail you
a the outlines.

Cheers! - K.


Keith Morgan


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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #1 on: April 16, 2018, 06:25:53 PM »
Nice little plane you got started there. As never seen or touched anything like this before, you do actually have to carve out a fuselage for a build like this? And by the looks of it, is that a piece of 2 x 4?

Offline goozgog

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #2 on: April 17, 2018, 01:36:39 AM »
Hello Chancey.

    Yup! It is a piece of pine from a 2x4.
What you're seeing is the plug that the wet balsa
is molded over.
   There is no carving involved with these planes.
The heaviest wood is 1/16" balsa.

 The picture might help to explain it better.

  Basically, the idea is to soak the balsa in hot water
for ten minutes then position it on the plug and
wrap it with a tensor bandage. I buy mine at the
dollar store.
   The 1/16" balsa will bend easily over the plug
but wind the bandage as tightly as possible.
Be careful ( ! ) to keep the windings  flat or
the edges of the bandage will bruise the wood.
The picture shows that I wasn't careful enough.
  The thing seems to dry in a day but putting it
on a forced air heat register speeds it up.

  One mistake I made was cutting a notch in
the plug where the horizontal stabilizer attaches.
This makes it difficult to get the bandage winding
even. It makes more sense to leave the plug
symmetrical and cut the flat area after the two
sides are joined.  I will be repairing the notch
on the plug before I mold more sides.

  Top Flite was very cagey with this design.
The entire plane can be made with just two
sheets of 1/16" x 3" x 36" balsa and a 2" x 1.5"
piece of ply.
That was probably important when your customers
are paying with dimes and nickles hoarded over
months. VERY slim profit margins!
« Last Edit: April 17, 2018, 11:42:20 AM by goozgog »
Keith Morgan

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #3 on: April 17, 2018, 11:54:39 AM »
Neat, very neat. Thanks for the detail and explaining how it's done. I guess it is a good way to get a nice light full fuse model. I will be watching this with interest.

Offline goozgog

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #4 on: April 17, 2018, 04:36:12 PM »
   I'm starting to feel like this plane is closer to
origami than model aircraft building.
The wing relies on the curve of the leading edge
to add rigidity, just like a hard fold does in origami.
  Maybe Top Flite used 3/32" for the wing. The only
reason I think it's 1/16" is because as a kid I thought
"Wow. It's only made out of 1/16 !
I might have been wrong.

  Anyway, the picture shows the form I ripped on the
table saw to mold the wing over. It cut nice and
straight and was easy to sand to a decent curve
but the balsa could probably be molded over any
curved object like a banister or a hot water tank.
  You can just see the tip of the wing poking out
from under the wrappings. After it dried It came away
stiffer and straight. I think I will apply the  Silk Span
with the wing still on the form, hoping the dope and
paper make it more rigid.  I pretty sure it will work.

  As kids, we just assembled the plane with Ambroid,
then mixed our mother's talcum powder with her
clear nail polish and sealed the wood before smearing
on some of that terrible Pactra dope.
   My mother hated me playing with model airplanes.
This new version will have Silk Span on all surfaces.
That should be stronger than the planes of my
delinquent youth.
Keith Morgan

Offline goozgog

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Re: Top Flite Form-Flite Thunderbolt 18"
« Reply #5 on: April 18, 2018, 12:45:52 PM »
The weather is awful, so I'm trying to distract myself
from everything that I should be doing this week.

Knowing that I would be using the forms to accurately
assemble the parts with CyA, I rubbed them with a
candle and heated it into the pine with my hot air gun.
So far the CyA hasn't glued the balsa to the forms.

 The fuselage is going exactly to plan.
  The dry shells naturally cling to the plug, so I just
overlap the edges and cut through both layers to get
a perfect seam. I stitched the edges together with
CyA and the seam between the halves disappeared.
I checked that the plug would slide out and the
candle wax worked perfectly, so I pushed it back in
and doped on a layer of medium silkspan, built up a
few layers of butyrate dope and rubbed it out with
#600 wet & dry.
 Working on the plug makes everything easy since it
holds the delicate shells straight and sanding and polishing
are much quicker. It will also make aligning the wing
and stabilizer completely logical.
  In the picture the fuselage shell is ready for final dope
and weighs 0.3 oz or 9 gms.

  I wish I could say that the wing is going well.
It isn't.
  I waxed the pine form before I positioned and sanded
the wing. Two coats of Nitrate dope, then medium silkspan
that I laid on wet to the top side, brushing more Nitrate
through the paper.
It looked good, at first, but as it dried it lost it's shape and
warped.
What to do?
  I know I want paper on both sides of the wing, so I
soaked the uncovered balsa side and re-wrapped the wing
back on the form with the paper side down. It took the curve
easily but I will know better after it has dried.

  The molded fuselage and thin wing are what makes this
a real Form-Flite plane but maybe the thing to do is cheat
by using a 1/4" thick wing like on Muscianos or build a
"Spread fingers" wing like I used on the Spitfire.

Cheers!

« Last Edit: April 19, 2018, 11:38:53 AM by goozgog »
Keith Morgan

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #6 on: April 18, 2018, 02:10:59 PM »
That's amazing, and very cool. I did not think it would go back on the 'plug' for assembly, and never would have thought that you would be able to get it back out. Just when I thought your coroplast PT-19 I built was cool, you topped it!

Offline goozgog

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Top Flight Form-Flight Thunderbolt Build
« Reply #7 on: April 19, 2018, 11:25:35 AM »
Thanks for the encouragement Chancey!

   As I'm playing on this plane I'm suffering
waves of Work Ethic guilt.  The fact that it is so
much a toy isn't helping.

  Anyway....
 
  The picture shows that the wing turned out
OK after all. Even after several coats of butyrate,
it starts to warp when the next coat is applied.
Holding it down on the form as it dries did result in
a straight and reasonably stiff wing..
   The under cambered "foil"  looks like it belongs
on a 1911 Bleriot, not a P-47.  The leading edge
curves down way farther than my instincts can ignore,
but it is very close to the original so I have to trust that.

  The original Form-Flites had a divot taken out of the
bottom of the fuselage for mounting the wing and controls.
That might have been best for fumble fingered kids ( like I was)
but , as the picture shows, I have extended the wing slot
out past the firewall and will slide everything in from the front.
The test fits show that it works well and I won't need to
cut up my beautiful "Taco Shell" fuselage.

The air frame as shown weighs 1.4 oz (38 gm) with the controls,
and a Baby Bee weighs 2.1 oz (61 gm) with the prop, so 
I think this will be finished at less than five Oz.
Not bad at all.  :-)
Keith Morgan

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #8 on: April 19, 2018, 03:16:03 PM »
Wow, you're just truckin' along on that one. I wish I had the energy to build something that fast. Besides the Man-Win Trainers I built, honestly the quickest thing I built was your Coro PT-19! I wish I was closer so I could see this in person, and maybe build one too. As usual, keep up the good work!

Just a question regarding the wing. As you state you applied your dope then put it back on the mold, is it safe to assume that you put wax paper or something to cover the surfaces to protect them from the wing sticking?

Offline goozgog

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #9 on: April 19, 2018, 05:26:21 PM »
Hey Chancey! 
You might be the only person watching, so thanks!

   With both the fuselage plug and the wing form,
I rubbed them with a candle , then melted the wax
into the pine with my heat gun. I did this about
three times before I used them to glue things
straight. CyA doesn't seem to stick to paraffin...

 Hope you're flying season comes soon. We're
still thawing out here with lots of snow on the
ground.
  The Beavers are planning our first session this
weekend if the weather forecast is true.

Cheers! - K.
Keith Morgan

Offline kenneth cook

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #10 on: April 19, 2018, 05:31:35 PM »
          I'm watching as well and very interested. I have the larger Top Flite P-47 and all of the others with the exception of one in that line of pre formed line. Ken

Offline Jim Matos

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #11 on: April 19, 2018, 08:26:30 PM »
I'm watching too!  I have a fondness for puny models.

Online Chancey Chorney

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #12 on: April 19, 2018, 11:05:23 PM »
Hey Chancey! 

 Hope you're flying season comes soon. We're
still thawing out here with lots of snow on the
ground.
  The Beavers are planning our first session this
weekend if the weather forecast is true.

Cheers! - K.

Hey there. There is now minimal snow here, and the weather has finally smartened up at the end of my holidays! As for flying, the field/park I fly at here at home is soggy and a bit of snow left, but at the cottage where I do most of my flying at last report was still covered (talked to neighbour last week and was told could not get in my driveway yet). Anyways, while doing a big spring cleaning here today, I pulld these out of hibernation. Will be bench running these hopefully this weekend if time permits. Ther may be a couple of things you might recognize in the picture (bad picture, but one of the things is mounted on the 'Platter')..... ;D

Online Chancey Chorney

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #13 on: April 19, 2018, 11:06:32 PM »
Forgot to add I hope the weather co-operates for you this weekend too.

Offline Steve Berry

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #14 on: April 20, 2018, 09:14:54 AM »
I've been following this thread, as well. Excellent craftsmanship. Just one thing - could you show some detail on the landing gear attachment to the wing?

Offline john e. holliday

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #15 on: April 20, 2018, 11:43:57 AM »
The old DOC has been watching this thread and am amazed at the quality of work you are doing.  I vaguely remember those old kits, but like others the price was a little steep for a young kid. D>K
I was always taught to respect my elders, but it keeps getting harder to find one.
Today I broke my personal record for most consecutive days lived.
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530

Offline goozgog

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #16 on: Yesterday at 01:04:05 PM »
Hello Doc, Steve and Chancey!

   Doc.  I'm pretty sure we met at Brodak's a few years
back.
   Of course, everyone meets everyone at Brodak's.   y1
I'm planning on being there for the 2018 edition.
Hope to see you there again sometime.

  Steve, I'm attaching a picture of the underside of
the wing and another of the inside of the fuselage.
  The plane is pulled apart so everything looks bad
and off angle. It gets tidied up during final assembly!

  You can see how the L/G wire is just wedged against
strips of 1/16 glued to the underside of the wing.
The Top Flite kits supplied cotton gauze to attach
the wire to the wing with glue.
I remember that it worked OK.
   If you look at the second picture, you can see the
ends of the wire poking up through the pine block
attached to the wing. Not exactly like the kit but the
landing gear is identical and it works the same way.

  You can also see the bell crank made from two layers
of "credit cards"... Actually Wal-Mart gift cards.
This has worked great for me on other projects.
Cheap, easy and available. Just scrape the card with
a knife to remove the graphics and laminate together
with CyA.

  I've made the Bottle Trick canopy and it looks good!
I still haven't learned a good way to attach canopies
made from pop bottles. I'll probably do something
with epoxy.

Chancey!  It looks to me that the Enya has found
a happy home. Hope it's giving good service!

Cheers! - K.
Keith Morgan

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #17 on: Yesterday at 07:34:01 PM »
Nice little update. I like the credit/gift card for a bellcrank. Never would have thought of it, and, even if I did, I would not have had enough brains to think of laminating it! I am however shocked that CA would bond it that well. I would have thought epoxy, but you do know what you are doing and have done so in the past. Glad I always keep my hotel keys and gift cards.....

Yes, the little Enya has found herself a nice happy place on the 'Platter'. I had a goal of running it today, however I had many problems. I wanted to get my new 'Aircar' out on teh road for a test run today. All my glow starters were dead, flight box 12V batteries dead..... So, I did charge them up a bit to get things going. However, my MDS .40 engine I have on it does not run properly or well. I had tried a long time to get it running right as well as took it to a very knowledgable flieer locally, and on here, to give me a hand. Even then we could not get a good solid running engine. These were known for having carburetor problems. So, until I can find a used carb to fit this engine, I will be throwing it in the corner. Kinda saddening, but that's the way the way the cookie crumbles! So with that said, I am now looking forward to running the Enya tomorrow, and if all goes well, even a couple of Cox engines too!


Offline Jim Matos

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Re: Top Flight Form-Flight Thunderbolt 18"
« Reply #18 on: Yesterday at 08:01:04 PM »
  I've made the Bottle Trick canopy and it looks good!
I still haven't learned a good way to attach canopies
made from pop bottles. I'll probably do something
with epoxy.

I like stuff I find at Michael's called E6000. It feels and smells almost like clear silicone glue. It dries clear, cleans up by rubbing off just before it cures completely, and appears fuel proof.

I've used it several times for canopies. And it has found it's way under the engine cowls of my Dave Cowell Scientific reproductions.
I needed to repair my son's Typhoon engine (Cox Babe Bee) after several flights. It took some force to rip the engine cowl off. Enough effort was expended that the original cowl had to be replaced.

PS: I love the credit card bellcrank idea! What do you use to bush the bellcrank? Or do you let it ride right on the mounting screw?
Thanks in advance!


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