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Nov 21, 2021, 04:11 PM
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Quote:
Originally Posted by Trisquire
Maybe pre-shrink the Mt. Fuji?
The Japanese and the English grammarians will be angry if you do.
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Nov 22, 2021, 08:29 PM
Balsa Flies Better!
Thread OP
So I've made some progress on the airplane. Getting the hang of this Mt. Fuji-overall, the job on the fuse is acceptable, but I'm still better with Esaki. Wings are OK, but it compressed some of the ribs in one wing- they're wavy. Hasn't turned into a pretzel though....

I can see I'm going to spray this airplane with Krylon either before I fly it or soon after I get it trimmed- I'm very worried that any further shrinking of the wing tissue will lead to a pretzel and getting the wings off is not trivial. Might be put on the ceremonial bonfire at the Turkey Fly if that happens....

Getting the wings on was a bit of PITA- I'm still a little worried about the incidence, but I think it looks OK- will need a bit more in the top wing.

Working on the fillets- next up is the canopy.

Can I just use the box color scheme from the Dumas kit? I've got the decals, not sure of the tail surface color though- was there a green tailed squadron? Either that or I'm going to not worry about it and just live with the errors of a "fictitious" airplane. I don't plan on flying this one in scale anyhow.

Sam
Nov 23, 2021, 03:21 PM
Registered User
MKellyvich's Avatar
Green was the tail color for the USS Ranger in the late 1930s. VB-4 operated SBC-3s off the Ranger 1939-1940, with codes 4-B-x. The full red cowl identified the aircraft as leader for section 1. The Dumas scheme is pretty much the same as the painting on the back of the Squadron SBC in Action book (see attached), which is identified as being from Naval Air Reserve Base St. Louis in 1939.

Build looks good!

Cheers,

Mike
Nov 23, 2021, 08:27 PM
Balsa Flies Better!
Thread OP
Thanks Mike- for both the references and the compliment. It is coming along- not my favorite airplane though. I think this is one of those builds where if I walk away from it for very long, I'm going to be afraid that I'll never pick it back up. So I want to finish this airplane sooner rather than later.

To anyone who wants to build an SBC Helldiver- based on past experience with Dumas kits, that's a better starting place although you're going to have to do some modifications too. Oh well, it would be nice if more FF kits could actually be built out of the box, but that's very much a rarity these days. Actually, I think it's always been a rarity- maybe that's why FF lost so many beginners.

I did dig out one reference on the airplane which pointed out that the pre Pearl Harbor livery was often kept when the airplane was transferred to a Naval Air Reserve station- but this reference didn't acknowledge the Marine Squadrons that used the airplane operationally as noted earlier in this thread.

Also found a photo of a really easy to do F4F color scheme- all white with small early '42 roundels. I built the Easy Built F4F, but never got it trimmed out. Have the Diels kit, although I'm tempted to do either the Jimmy Thach or Butch O'Hare airplane...Oh well- that's a long ways off in the queue.

Sam
Nov 26, 2021, 05:20 PM
Balsa Flies Better!
Thread OP
Making some more headway. Decided not to aggravate myself no end and opted to just use the Dumas canopy. I probably added an extra 5 grams to the airplane, but I couldn't make the patterns work and the Dumas canopy does look better than anything I would have come up with.

Working on attaching the top wing now. I'm going to set it up with only the bottom of the center section covered, so I have good access to the wires that provide most of the structural strength of the struts. I will cover the outer panels fully- I need to be able to pin this wing down as the Elmer's glue dries, or it's going to warp. (Don't ask me how I know...)

Current weight is 62 grams, so I'm betting that I'll be between 70 and 75 grams sans rubber. Not indoor weight, but not too portly either assuming that I get something useful out of the lower wing. My Herr Bonanza is 65 grams sans rubber but I think this airplane has more area- but a shorter fuse.

Sam
Nov 26, 2021, 05:49 PM
I like thermals
It all looks great, esp. that canopy.
Nov 26, 2021, 07:01 PM
Balsa Flies Better!
Thread OP
Thanks- I think it's worth the weight, unless the airplane turns into a dog....

Dug out a photo of the nose gun- I was beating my head unnecessarily- it's pretty easy - just a short black cylinder. See: https://www.google.com/search?q=sbc-...2w3NdFzqYkkp2M

Sam
Nov 26, 2021, 07:49 PM
Registered User
MKellyvich's Avatar
I think that tube may be a telescope for aiming during dive bombing attacks.

Mike
Nov 26, 2021, 10:50 PM
Balsa Flies Better!
Thread OP
Hi Mike

It is- although on the photo of the airplane I'm using- it's a ring sight which I'm going to leave off. I've gathered that some dive bombers just used markings- sighting was apparently pretty easy if you could stay vertical (or close to it) long enough.

The gun is in a trough and there's not much of the gun sticking into the trough which makes it easy. I think my weight budget was a little aggressive- got the airplane mostly covered at this point.

Sam
Nov 28, 2021, 05:17 PM
Balsa Flies Better!
Thread OP
My weight budget was wildly aggressive, as the empty weight is a portly 83 grams. Pretty much done- this is what I did over the Thanksgiving holiday (yes, I saw my dad too). I think the stickers added between 2 and 3 grams- the canopy added another 5-7 grams, wheels, 2 grams- so I'm betting that if I'd built this airplane without the plastic- could have saved 10 grams easy. I'm a little concerned that the fuse stringers in front of the motor peg are unsupported and not the strongest wood going, but overall, I think the airplane is strong enough to handle a fully wound motor without shortening itself dramatically.

I'm guessing on the cg- right now it's a bit aft of the top main spar, which probably puts it close to the LE of the bottom wing. That's generally an OK starting point. Test glides show that the airplane is a little stally, but it's close enough for me to put some rubber in and try it when conditions permit -which will probably be in 2022 at this rate...

Need to add the stab struts, probably some tailwheel segment, and then hit it with Krylon which will be a novelty for me. But if I've got the washout/washin correct on the wings- I don't want to watch them pretzel if they ever get damp.

Sam
Dec 01, 2021, 03:45 PM
B for Bruce
BMatthews's Avatar
It's not a small model by any means. So I'm thinking that 85'ish grams after Krylon and final details isn't too bad a wing loading. Hmmmm?

Lookin' sharp though! ! ! !
Dec 01, 2021, 05:59 PM
Balsa Flies Better!
Thread OP
Thanks Bruce....

Haven't Krylon'd the airplane yet- wanted to get it in trim or at least close. The airplane does need some down elevator- thought I might have been a bit aggressive with the wing incidence, but somehow, I think it still needs downthrust.

Oh yeah- I took the airplane out today and gave it a few tosses with some hand winds. With noseweight (still needs a bit more) and around 10% rubber- the airplane's topping the scales at 95 grams. I've gotten the airplane to do a lap or so- have to think about my power combo. The airplane needs more oomph to stay airborne in cruise mode of the motor, which generally means a thicker cross section. But given that I'm motor limited- I'm beginning to wonder if a smaller prop would help- might just clip the tips of this one- it's a Czech P-30 prop.

In flight- the airplane looks good. I'm a bit surprised that the cg had to go so far forward- I'm balancing the airplane on the main spar of the top wing, but it definitely wanted more noseweight- the stall got worse as the power ran down. It's probably going to need a bit more downthrust, but I don't think I'm too far off and as noted, I had to steam in a little down elevator. What I was happy to see is that the stall is pretty much straight ahead, which generally means I've got the washout right. The airplane is flying in a too tight left hand circle, but that may open up with a bit more noseweight. (ran out- have to get some more clay)

It's a little hard to hold the airplane to launch it- there are no formers in between the wing fillet and the motor peg, so I'm pretty much holding it from the motor peg former with a little finger support running forward.

Overall though, I'm pretty happy with the airplane. I'm now glad I added the weight in some of the doo-dads as the airplane looks like it's doing fine- certainly not a sled. The real trick is to see if I can trim it out to be competitive with the 10% motor. I doubt it'd be a real threat at Geneseo though.

Sam
Dec 01, 2021, 09:28 PM
B for Bruce
BMatthews's Avatar
If it doesn't win at least it's got style...

The forward CG might be the wing incidence thing if you think you put in too much. Watch how it recovers from slight or big stalls as a sign of how stable it might be. You might get away with a bit more down trim and a shift back with the balance if it's strongly stable in the stall recovery.
Dec 01, 2021, 11:39 PM
Balsa Flies Better!
Thread OP
Hi Bruce

Thanks! The raison d'etre of this airplane was really to keep my flying buddies from razzing me for flying a monoplane in WWII ML events, so if it does that, I'm happy. I don't think I'll disgrace myself with it...

My trimming methodology is that I don't really worry about the cg that much- I just want to start with it in the right neighborhood. I know guys like Don Deloach really go after the cg before putting power to the airplane and then they don't move it. I tweak cg as I fly the airplane. I use weight to control what happens at the end of the flight and the airplane is descending. If I start noticing a stall developing as the power winds down, odds are the cg is a little too far back. I generally haven't had to worry too much about a really aft cg with a tuck too often, although I did have that experience with a Dumas Staggerwing. Actually saw that with an Albatros too. Not sure why I have that issue with biplanes- hopefully I won't have that happen with this one.

Sam
Last edited by Megowcoupe; Dec 01, 2021 at 11:46 PM.
Dec 04, 2021, 09:04 PM
Registered User
MKellyvich's Avatar
Sam,

Glad to hear the SBC wants to fly - look forward to results when you can start getting more turns into the motor.

Mike


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