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Speed,Combat,Scale,Racing => Scale Models => Topic started by: Paul Smith on July 17, 2011, 06:24:28 AM
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This could be posted under 1/2A or Scale, I put it under scale. It's intended for the contest in Toronto, September 24, 2011.
This model will be a true 1/2A, that is total displacement under .050 cubic inches. It started with a Black Hawk comic book from a used book store and got rolling due to a kit found in box of stuff bought at The Brodak.
The third and decisive stuff was digging out a box of 40-to-50 year old .020's and finding three that still run. Confirming the engines is a step that I strongly recommend before going farther on any project.
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The next step, before cutting wood, was to download some 3-view and blow them up model size. My price check at Office Max and Kinkos told me that it would cost three times as much to have the 8.5 x 11 scanned and blown up all at once, vs making several 11" x 17" sheets and taping them together. I went with the later method, which gave me some extras for cutting and template making.
I got burned (well maybe just singed) by starting to build from kits/plans, then finding they don't match the documentation.
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Quite a project even if it is 1/2A. Keep us posted. H^^
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I went with TeeDee .020's for several reasons:
1. I have three that run, enough for the model and one spare.
2. Weight: The engine with prop weighs 1.0 oz, compared with 2.5 for Golden Bee or Black Widow. That's a saving of 3 ounces in engines alone. Considering the location out in front of the wing, it might have needed one more ounce of tail weight.
3. I'm of the opinion that a couple of healthy TeeDees .020's will be all that's needed.
I hedged my bet by leaving the firewalls big enough to go up to .049's if needed. The engine mounts are beefed up fore & aft with 1/8 x 1/4 and 1/64" plywood vertically.
This is my first pass at a twin. But experience pitting for others makes me believe that the two engines will part company if you don't use enough material to keep 'em together. They're rotated 30 degrees to put the fuel pickups and fillers in a better place.
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I am loving this project. Will be watching closely. H^^
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I went with the tailplane dihedral because it's a contest scale project. This is sort of a key element in the look of the plane, like the gull wing on a Stuka or Corsair. But it's triple trouble. I can see why Black Hawk made their kit the easy way.
1. The stab has a glue joint in the middle. No chance of crosswise reinforcement.
2. Tip rudders help the real twin engine plane in engine-out conditions, but can easily break the tail in a minor hard landing, or ground accident.
3. Figuring out how to drive both flippers.
Anyway, I cut some angle blocks on the bevel saw to get the stab and rudders on square.
The fuselage got a coat of carbon veil to help hold it together. I'm not sure how well this stuff works, so this is a chance to learn.
I like to keep the subassemblies apart as long as possible so I can sand flat and work on one while another dries.
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Let me clear up one point, when I asked Frank Scot to do the design work on this model I told him that we were making the Comic book model NOT a scale XF-5F. The important factors were that it looked like the comic book model, was easy to assemble and would fly very well. Frank accomplished all of this and I am very pleased with this kit. You will note the comic book on the box art and inside on some instructions.
When we make a true scale kit the words "Scale Model Kit" appears in the upper right hand corner of the label along with an icon of a "T" square and a compass. I have seen many modifications made to this model and I am looking forward to seeing this one too. GOOD LUCK WITH IT PAUL. H^^
Larry
Black Hawk Models
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Right ! This is getting built as
THE prototype XF5F-1, not the Black Hawk plane in the comic books. The color scheme is not as flashy. It's all silver except the top of the wing (yellow) and the markings.
Here it is slipped togerher for it's first test fitting. Weight is 6.1 ounces at this point. It still lacks:
- Firewall fairings.
Landing gear.
Flight controls
Assembly glue.
Paint
I think getting it all up under 9 ounces is within range.
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Looks good Paul, love the 3 blade props - I was going to suggest just having the elevator on one of the horiz stabs work, a-la some speed planes but see you got that part figured out. Wish I built as fast as you do. 8)
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Only one flipper working? That's a possible solution.
The whole business of flight control is an open question.
Bellcrank location is still a concern. Top or bottom of wing?
The BOTTOM would certainly help the plane hang out better in upright flight. It would look better. But the control linkagoe would be more of an issue and I would need to drill through the left engine nacelle. If I'm able to go inverted and do lazy eights it might work against me.
The case for putting it ON TOP of the wing is a straight shot to the (inboard) flipper, and no need to weaken the left engine nacelle. The downside is a possible line tension loss in upright flight and a the visibility on the bellcrank on top.
After some thought, I gave up on making the landing gear removable and just built in a basic 1/16" bent wire gear. All of my "removable" schemes triggered more weight and complexity that I could afford in the .020 size.
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To fly this plane in a scale contest you should take a close look at the rudders. Not only are the elevators swept up, the rudders are vertical to level not 90 degrees to the elevator. Oh my such is scale. These are very catching planes and make a good scale build. Eric
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Yeah, they're just pinned on right now. I plan to use the same angle blocks to true 'em up. I expect to wait until the very end to add 'em so I bust the tail trying to sand it.
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There were two Skyrockets at the last 1/2A Multi-engine Profile Scale contest in Tucson last October. Pictures appear in the Central Arizona Control Line Club newlsetter posted on their website:
http://controllinecentaz.com/WEB/Newsletters/2010%20Newsletters/SeptOct%202010%20Newsletter.pdf
This has pictures and some neat narrative by Ted Kraver on this contest.
Ted Kraver has done a good job of showing some neat details on these models including the Skyrockets.
Keith
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Intesting report.
It looks like one was a Blackhawk kit and the other was a much-bigger model with true tail dihedral.
The included scoresheet had John Stevenson's score added up wrong. The numbers total 76.0, but the total says 96.0. Maybe the posted the marks are wrong and the total is OK. It looks like he was low-balled on "color", for no good reason. Maybe that's the missing points.
Anyway, a lot of models for a one-of-a-kind airplane.
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This is the last installment for a few weeks, I'm going on a non-modeling vacation, but I'll think about this and other projects as I drive.
The weight check at shown is 6.9 ounces. It's starting to feel a bit nose heavy, even with the .020's. I might remedy this by making a heavier stab, possibly 1/8" plywood.
I thought the kit engine mounts were weak, so I beefed 'em up. Maybe too much. The entire module (w/engine) weighs 1.75 ounces, compared to 2.5 for a Golden Bee alone. But still, I wasted some mass by allowing to upgrade to .049's I will probably skinny down the mounts some more and give up on the .049 option.
The enignes are rotated 30 degrees to put the pickup & vents in better position. I might try 45 degrees next time. I couldn't rotate the top end of the engine 90 degrees because the fuel nipple goes into the cylinder. Maybe it could rotate 180 degrees, but that would border on inverted starting.
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Too bad we don't have "fictional scale" like they do in the FAC. They have a Free Flight event where you could actually use plane like the Black Hawk Skyrocket. The comic book I bought has an article where the captain steals the prototype from its hanger and it's plain light gray at the point in the story.
Also, I have a Grumman publicty art work that has the Skyrocket in blue & gray camo with more modern roundels. But for the actual contest work, the one-and-only siver & yellow is the only option.
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I'm back in the chop again after a 23-day non-modeling vacation. Mid-May through early July was pretty much pure control line, featuring six major events. Here's a little info from the break.
Southwest Colorado, near Durango, Cascade, and Silverton. I took my first glider flight ever and my first real plane flight in about 25 years. Took off at 6,400 feet, towed to 9,000 feet, released tow & took over the controls. Thermaled to 11,000 feet, went sight seeing in the 14,000-foot mountains, and descended back to the postage stamp-side air strip.
That's Baron von Richtoffen, our new one-year old daschund. To him, a four hour 10,000 foot mountain hike is just a light workout if he can cool down in mountain stream. That big stone thing is the "Chinese Wall", a 1930's CCC project built when they didn't just send out government assistance for nothing.
We went on the D&SNGRR on the very last train before a big rock slide buried the track and marooned two trains (shown) in Silverton until the track was fixed.
So much for the wildwild west, I'm back in my model cave. See you at the F2D TT in Detroit Labour Day weekend.
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I have a little bit of progress to report. The wing/fuselage assembly is complete. The engine nacelles and tailplane are being designed a built separate to be installed later.
It was starting to feel a bit nose heavy, so I made a new tailplane of plywood. It will need the strength with the dihedral and tip fins.
The engine cowls are squished down to ovals in accordance with profile protocol. The were made "full coverage" first, then notched out for the engines.
The silver on the bottom of the wing didn't turn out too well. I needed to dope it more or cover it, but I didn't want to add too much weight. It will get another coat or two when the engine pods sare glued on.
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Looking better. H^^
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Engine nacelle installation.
As was mentioned before, this is my first multi-engine plane. One issue that came to mind was aligning the engines to each other and also to the plane. I solved this by bolting both engine pods to a piece of hardwood and tweeking them to each other before gluing to the airplane.
As shown, it's just a loose slip fit. It went OK. I Hot Stuffed 'em and then followed up epoxy & micro balloons.