skaliwag

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It's looking like a cross bread Pacer and Birdie. Could call her a "Pirdie"
I'd really appreciate a dxf file of the ribs if you laser cut the spare set ..

Pond Skipper

Your on a roll with this one hope to see a vid says the peanut gallery.
Any vid of the Profi 1/2A yet?

MJD

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Well there are two Profi 1/2A but I think you mean the Screamin Toucan formerly known as a Boomerang with the Profi Rambler .049 (proto speed version). It went up for four short flights this season only - on the day Crosscheck and his dad were up. I had no end of what I first thought were mixture troubles that day, it never flew worth beans for more than 5 seconds. Odd since I have the compression on the modest side. Replaced bladder, bla bla. Turns out the Nelson plug would not seal 100%.. it was new and I couldn't see any detail on the beveled face that would explain it. But a squirt of fuel on the head revealed the problem after some head scratching and creative profanity. Only had one Nelson plug with me that day.. derp.

I replaced it at home, ran it up - zing zing ran out half a bladder fine. That's on YT.

But no more flight video since the maiden voyage posted a while ago.

The other Profi 1/2A is the piped speed engine. Something is up, I can hardly get it to pre-stage even with crazy small prop load. Alex noted on the cl speed video that he was running about a 4x4, and he had it running rich but fast easily in that vid. I'll get in touch with him to run over the problem.. likely my plumbing.

This winter's priorities are:

1. finish the L-39 turbine
2. build speedracerntrixie's Macchi 202 pylon racer.. it won't keep up with a YS 115WS powered version, but it will still haul the mail for fun on an OPS .80.
3. fix the Virus

Guess I never posted that story did I? Had a 30 second maiden flight with way less fuel flow that I should have, ended with low and slow snap spin into ploughed earth. Not so bad, broken and bloodied nose. I've flown hairy stuff but this took the cake... 13+ lb wet.. nowhere near full power, bungeed up into 3 wobbly high alpha 100' high laps around the field. Ack..

What a stupid problem it turned out to be - when I pulled the gear off the bench and installed it in the model, I totally forgot that I changed from a 1400 mAh LiFe 2S pack, to a 5 cell NiMH.. there was enough voltage drop between the two that the engine went from whiny lean to a nice roar on the ground, but my less than experienced ears did not pick up that the engine was not anywhere as rich as it should be. So off we went.. oops. Live and learn.

MJD

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I did some forensic work on the Birdie airfoil. I laser cut a 1/8” ply NACA2415 template, and it fits the wing saddle like a key in a lock. But, the lower half is another story. It looks like it has had some creative mods – the lower rear section is flat, and the entry has been thinned out. It doesn’t look like any published airfoil, it really looks like a hybrid, drafting board, or maybe sanding block, creation. There would be no logical reason for an engineered airfoil to fit the top curve perfectly unless it was a 2415.. or at least I think not.

So I will have to manually recreate this one.. but I will, and no sweat sharing. My goal is to draft a complete plan/part set so can cut as many as I wanna.

As for this particular model, I decided after figuring out the above, that I may as well copy the wing planform but with a thinner section. So it will get a 12% wing instead, don’t need to go any sillier than that with the box fuse etc. I think I said something earlier about building it as is and get on with it. Guess not!

Think I'll radius the stab tips to match the stock kit and I also believe it would be more kewl and maybe funnier to put a proper shape vertical stab on it instead of this little quickie style thing. Already have it drawn anyways, but I'll still skip the rudder.

MJD

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Decided to keep the retro look and cut a rudderless version of the stock fin, and radius the stab tips more like stock.

I figured out how to draw the airfoil on the plans LOL.. take a 6-3/16" chord NACA 6415 airfoil, and from the front of the bottom spar back, take a ruler from there to a point 1/16" offset below the TE apex. The side view on the plans perfectly matches the fuse itself and the 2415 template top curve. The ribs themselves look like they suffered from not so precise translation into steel rule dies.

In the pic are the 2415 template, 2412 template, and the wing saddle adapter for the 12% wing - check out the fit to the wing saddle of the 2415 top curve.

The 1/2A version would probably perk up with the 12% section and today's light gear.

Pond Skipper

Fun Fly and 1/2A

MJD

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double post - stupid crashing browser..

MJD

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I'll stick with 12% for this monstrosity, figure I need the depth for mechanical loads during frantic turns. On the 1/2A version, I'd like to see how low the weight can go, but the stock airframe is not overly heavy.

I think the formula is:

New weight = 23oz - (the difference between '80's radio gear and today) - (paranoia about structural strength, lighter covering films, CA not epoxy, etc.)

Stock might be 16-18 oz done light mebbe?

The funny mod to the rear of the stock airfoil is a concern, the straightening of the lower surface effectively increases camber in the rear 2/3 of the airfoil - I worry about behaviour at speed, tucking for example.. ?? The old Robbe Rasant, which people treated like a sport speed aircraft but really it was just a boxy sport model with a short wing.. had a problem at speed for similar reasons.

skaliwag

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I think the 2412 is a nice compromise airfoil for 1/2A.

MJD

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That's what I figure too. Still has some thickness and nice manners, but we just don't need the CL or the drag of the thicker section.

So rather than recreate a BATA shoe airfoil, I'll use a stock 2412 on my repro drawing. Hmm.. or 1412.. or Eppler 168 symmetrical...?

2412 to start.

MJD

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Stock shaped fin, but modified for this A/E version. The rudder cut is erased and the fuselage extension replaces the lower part of the rudder. The kit clone will have interlocking features to align the tail group.

This one gets a 1/16" ply plate holding the sub-fin, that will fit to the fuse with four servo screws for access to the hidden elevator linkage. Then some sheeting, then another hatch about halfway to the TE, covering the elevator servo and the battery - the infamous $3 700mAh Zippy LiFe pack. 1.4oz, 41g, 4 times as much flight time as I'll ever need, but no worry dawdling in the pits.

Need a bit of filler in the fuse cavity.. durn Dremel can get jumpy.

Glad I went back to stock outlines. The nose will still look like a genetic experiment gone awry, with no canopy and a top pipe. Depending how this works out, with a Conquest it could keep the canopy.

kaczonion

Had one of these in my attic for a few years and built it last year. Used an eflight 450 motor and 3s lipo. Did not like the large prop had an old 9x9 pylon prop and worked ok but still wanted to roll from prop torque.

MJD

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I'd probably throw in an E-flite series 6 motor and 3S 1800, 6-3 or 6-4 prop, would be like a hot .10 at that point. I would like to do a lekkie version, but later..

Pond Skipper

E what??? cough cough gasp cough

Pond Skipper

Check this out Mike have you seen what 3D Lab Print has been up too?

https://www.youtube.com/watch?v=4ybuv2TEYrk Wonder how it holds up to nitro

MJD

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Forgive me for the implication that this is by any means an acceptable or desirable course of action.. I should be more careful with my phrasing. What I really meant is "if I were held at gunpoint and forced to build an electric Baby Birdie, since I already own on of these stupid motors, I'd use that and be done with it..".

MJD

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Okay, that 3D printing is too cool! I'd be content if I could just make mold plugs with such a gizmo.

Pond Skipper

They sell the software for each plane type you go from there with your choice of colors and size etc.

7 planes thus far $20 bucks for each software package.
https://3dlabprint.com/index.php?id_...oller=category

MJD

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Wow.. I know this technology is right there, but in my circles I don't run into it. Need to see some of this in action.

MJD

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I actually made progress since Sunday.. finished drawing wing and ribs in CAD, cut a set, built both panels, now sanding LE to shape, next to add TE/aileron stock. It is easy to find stock TE for stock fat ACE wings, but no 1/4x3/4 to be found which fits perfectly in the airfoil. However, a piece of sharply cut/sanded 1/4x1 with 1/4 trimmed off should serve.

iPad is broken, if I could find my phone I'd post a pic. Bear with me...

Fuselage (no cowl or nose ring yet) + stab and elevators + fin + all hatches and one HS85 glued into the fuse rear + both wing panels minus tips = 6.5 ounces. Liking it so far, I think the bare airframe will end up 8.0-8.5 ounces + finish + tank and engine. 23-34 ounces if within reach if I don't marinate it in epoxy paint.

Anyway, while building this version I have been drafting up a "stock" 1/2A version. Although, I will stick with the 12% airfoil, the wing is plenty beefy while light and the thickness is unnecessary. The LE has a reinforcing strip with square stock top and bottom to sand to shape - easy, since there is a single ply rib at the root and 1/32 ply tip caps which provide a sanding guide for the LE. Works so far.

Pond Skipper

24oz for a .15 would be a great modern mile stone to win with a conventional pattern ship, the plane would be
a crisp ship to pilot. Look forward to more pics and flight vid.

MJD

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To give it a fair shake as a .15 gonzo sport ship, I should really build another one with a more normal engine on it, i.e. a throttle. Heck, I can use that highly mediocre CV-A .15 and run the pipe in tight to the side of the fuse. Or the Conquest. I would think a minor scale up - say 250 sq in, would be better for those heavier engines. Can still keep the structure light though, it is over built in a couple of areas. Let's see how this goes..

MJD

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Pics..



This is the 2412 wing, i.e. 12% thick. Much better. Only problem is to match the cross section, you need 1/4" x 3/4" or 5/16" x 1" TE stock. I'll trim and sand some 1/4x1".

I had no decent 1/4" to cut the stock for the TE of the wing panel, so I cut two from 1/8" and laminated them. That's the stripes down the TE.

By the time this is done I should have the whole thing drawn up and ready to cut in regular form. I have the canopy plug and baseplate done, waxed and Partalled.. ready to lay up the canopy mold. If I had a vacuuformer I'd do it that way.

In pic 2 you can see the ply adapter pieces I made to turn the wing saddle into a 2412 profile.

MJD

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Skaliwag - are you asking about the much more sensible 12% version or the thick fat ugly slow stock version that's only necessary if it's made from solid foam? I have no real preference myself.

I like the wing structure so far, using hard 1/8x1/4" spars. I will add vertical shear webs to the "repro" version and this wing. I will fully sheet this guy though.

I'll take a pic of my last ACE panel - it's a side show freak that ballooned out to about 20% except it is pinched at each tip. Weighs a ton too.. overshot it I guess.

aspeed

Looks pretty wicked with the pipe.