Scientific P-40 Warhawk (not the Red Tiger) - RC Groups
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Oct 30, 2017, 04:02 PM
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Build Log

Scientific P-40 Warhawk (not the Red Tiger)


Hi all,

I came across a 21" wing span Scientifc P-40 Warhawk kitted shortly after 1960. This one is a profile model, with plastic cowl, and a symmetrical wing.

It is new in the box, only some hardware was missing. All wood, decals, and plans have been scanned in order to scratch-build later if I desire.

For now...the dilemma is to build around a suitable powerplant for intermediate stunt. The firewall/plastic nose cowl iss set up for an 8cc Babe Bee or better reedie (Golden Bee, Black Widow).

I have on hand one Golden Bee and a new AP Wasp with matched black plastic engine mount. The Golden Bee is 1/32" longer, and weight is just about the same. Using the AP will require the use of an external tank, which should mount right on center of gravity (as well as being as large as 1 ounce).

The firewall will probably get mounted tonight. Looks like I'll make an extra firewall to sandwich the landing gear...and pull the firewall back on the fuselage the same thickness as the second firewall in order to keep the overall length the same.

Feel free to make comments concerning engine choice first, anything else next.
Last edited by 944_jim; Nov 12, 2017 at 12:12 AM. Reason: Misquoted Wing Span
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Oct 30, 2017, 10:49 PM
BWA
BWA
Registered User
I have the Shoestring in that series. It has a flat bottomed wing, if I ever build it, it will have a symmetrical wing......

The other thing I don't like about it, is, that they cut the leading and trailing edges with the same width between ribs, as the trailing edge has more angle than the leading edge, as the ribs get farther from the center of the wing, they end up at a more extreme angle. I'll re cut new trailing edges with the correct spacing so the ribs all end up parallel.......

Nice build so far.......
Oct 31, 2017, 10:36 AM
Registered User
Quote:
Originally Posted by BWA
The other thing I don't like about it, is, that they cut the leading and trailing edges with the same width between ribs, as the trailing edge has more angle than the leading edge, as the ribs get farther from the center of the wing, they end up at a more extreme angle. I'll re cut new trailing edges with the correct spacing so the ribs all end up parallel.
Yup! So when I cut my trailing edge free of the leading edge, I flip-flopped left TE for right TE to allow for some adjustments at the root ribs. The inner two ribs at the fuselage were set parallel to the fuse, and each other. The wing section removed from the fuse was glued in between those two ribs making for a slightly wider area. This gives the wing maximum purchase on the fuse when glued in.

I'd love to see the Shoestring kit...did it come with a plastic cowl?
Last edited by 944_jim; Oct 31, 2017 at 10:33 PM.
Nov 02, 2017, 12:11 AM
BWA
BWA
Registered User
Clever idea, I'll see if it will work on the Shoestring....

Yes, two piece plastic cowl.....

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Nov 04, 2017, 09:19 PM
Registered User

Scientific P-40 center of wing/root ribs


For BWA:

When flip-flopping the trailing edges, the wedge that is grafted in between them winds up being a significantly larger wedge. You could actually cut a wedge that runs deeper forward in the wing for more strength.

Then the "leftover" part of the trailing edge (the small section that the original wedge was to be glued into) can be trimmed to better fit the wingtips.

I hope the pix can do a better job explaining what I mean.
Last edited by 944_jim; Nov 05, 2017 at 12:40 AM.
Nov 05, 2017, 09:35 PM
BWA
BWA
Registered User
Yeah, got it. Funny that the same thing bugged both of us enough to want to fix the problem .

Also, funny that of two kits in the same series, one has a symmetrical wing, and, the other has a flat wing.

Since I fly inverted as much as right side up, I really need to make new symmetrical ribs, so, will fix both issues with new parts.......

Will definitely use a Golden Bee/Black Widow style motor, with the cylinder set outboard, my usual half A setup as on my Baby Flight Streak pictured bellow....


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Nov 06, 2017, 07:40 AM
Registered User
Beautiful plane! I see no hinges on the tail. Did you use small pinned hinges, floppie-disk plastic?
What did you do to the fuse?

It makes my work look so "cottage" or amateur.
Nov 06, 2017, 12:04 PM
BWA
BWA
Registered User
That thing is about 40 years old, with many hundreds of flights on it.

The hinges believe it or not, are standard Dubro Small plastic hinges, slotted into the 1/16" balsa tail surfaces. It's a lot of work.

The fuselage and all balsa parts were about sanded into oblivion, then faired into the wing with light filler (can't remember the brand), then several coats of HobbyPoxy grain filler, and, lots more sanding.

I think the final finish is Black Baron spray epoxy Red paint.

Here's some shots of my Sterling P-51 profile, you can see how much shape I sand (my cheapo little hobby plane does most of the heavy work) into regular profile fuselages. As well as looking good, it makes them lighter, and, lighter flies better.....

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Nov 06, 2017, 02:26 PM
Registered User
I considered rounding the P-40 fuse with an old razor plane...but the wood is so old it chips, rather than cuts.

Your Mustang is beautiful! Looks like you build BIG and small. I can afford space only for small. Long live 1/2A!
Nov 08, 2017, 08:26 PM
Registered User

A little more done


Well, I have the landing gear wire mounted/wire-sewn.
The firewall has been drilled for the engine. Right now, I plan on going with the AP Wasp. The engine cowl hasn't been glued/trimmed to fit. The AP mount HAS been drilled to fit the Golden Bee pattern in case I wuss out on the AP.

The wing needs to be glued in, rear landing gear and elevator installed, and a tank fitted.

Then it's off to the paint booth!

Hopefully this flies Thanksgiving.
Nov 09, 2017, 08:09 PM
BWA
BWA
Registered User
Looking better and better.

Did you get my reply to your PM??
Nov 09, 2017, 10:16 PM
Registered User
Quote:
Originally Posted by BWA
Looking better and better.

Did you get my reply to your PM??
Nope...did it go to the email I provided, or was it a PM through RCG?

I'll be online for a bit...otherwise will check first thing in the AM.

Thx!
Nov 10, 2017, 11:45 AM
BWA
BWA
Registered User
RCG PM, just sent another one..

That Shoestring is 18-1/2"

Also have a Scientific L19 Bird Dog, same wing style (flat bottom built up), but, with a built up fuselage, 18" wing span.

Also have in the built up fuselage range, a Hawker Hurricane, again, same flat bottomed built up wing, with a vac formed Turtle Deck, and, 19" wing span.
Nov 14, 2017, 07:52 PM
Registered User

Wing mounted


Well, the wing is glued on. I thought, and tested, and though some more. I didn't think I could get enough glue where it needed to be IF I slid the wing in most of the way, slathering glue on the wing's joint surface, and sliding the wing into place. This just sounded like an opportunity to squeegee the glue out of place as the wing slid home.

After much thought, I cut the bottom of the fuse off so I could properly get enough glue between the wing and fuse. This should ensure a more durable joint can be made topside, and bottom side when I replace the cutout.

Just visible is the tail skid instead of tail wheel...I plan on building a small stooge so I can fly without help!

Legoes robbed from my 11 yo leveled the back of the plane like jack stands, and a narrow book allowed the fuse to sit flush on the level wing.

As far as the engine goes, I'm closer to making first flights on a Golden Bee. That way I can make the cowl fit the engine more cleanly. If the plane can't loop, fly inverted, do wing-overs, then I'll switch to the AP.
More thinking may see a Nylon backplate product engine forward on a mount designed to bolt where the Bee's tank would go, along with a wedge tank for longer runs. If that happens, then I can flip-flop the product engine for the AP. This will be determined after the first few test hops on the Bee.
Last edited by 944_jim; Nov 14, 2017 at 08:08 PM.
Nov 27, 2017, 09:06 AM
Registered User
Getting closer to flying it. Still have to complete my lead-outs, clear-coat, mount main wheels and engine.
Those 57 year old decals were a bear! Once the glue dissolved enough to slide, it basically had no "stick" left. The mouth parts broke in several spots because they were so brittle. Almost 2.5 hours went into the decals!


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