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From yet another box of stuff in the shop comes..

Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

From yet another box of stuff in the shop comes..

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Old 03-04-2009, 11:44 PM
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MJD
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Default From yet another box of stuff in the shop comes..

.. a pair of nearly-forgotten sheeted foam wings I hadn't seen for a few years. Thinned SD6060 airfoil IIRC, 35" span, 7" root chord and 4.5" or so at the tip. Needs some beefing up, will have to add some composite reinforcement to hold together with a nasty engine in front.

I bet if 7 of you drew an airplane around the picture here and submitted them, we would have:

- 6 designs looking pretty much like what I have sketched up, basically a skinny quickie style box fuse with the OPS .15 up front (cowled a bit if possible and if ambition permits) and the pipe bracketed to the side out in the breeze, and cool jet like tail feathers. Not exactly aerodynamic perfection, but it is a friggin side exhaust so you may as well hang it out for show and a bit of go.

- 1 design done in ballpoint pen on lined note paper, showing a flying wing creation from the bowels of the earth - a fiberglass bat body slung underneath the wings, holding a bladder tank and a full-on speed .15 with pipe. Two torch-cut sheet metal vertical stabs shaped like mutated demon appendages screwed to the tips, each adorned with a skull and crossbones painted in crimson. All of this built in 2 evenings, and held in front of the camera by a hairy left hand.

Just a wild guess...

I can fit a Jett 4oz bubblefree tank in a 1-5/8" wide fuselage, and that's about what a mount will be (still gotta get one), so I guess that's how wide the fuselage will be.

The aileron stock tacked on the back is 1" wide. I'm thinking of starting the ailerons about 5" out with a span each of 8". Will give decent roll authority on high rate but not be too big for ripping around at top speed, or so I think.

Hopefully the engine is strong enough for an airplane this size.. . I may not yet have an appreciation for how potent a .15 can be. Sounds like a fun way to find out though. Just gotta keep those wings on and the ailerons from buzzin'.

I just finished up a couple of small projects and had to dive at this before anything big. I've been ogling the wings for a few days now, and finally tackled them yesterday not knowing exactly what the outcome would be. A little sweep looked cool, although it serves no useful purpose otherwise. Why not, it's a practice/sport fast 2.5cc airplane is all. And I'm still setting up my foam cutter.

MJD

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Old 03-05-2009, 01:11 AM
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Default RE: From yet another box of stuff in the shop comes..

MJD, I vote for something like a GLH. It'll be fast enough to be fun and a simple build. To simplify the build, make the wing nonremovable. This can also save weight [unibody].
I built something very similar years ago for a ST .15 and had to retrofit an additional spar into the sheeted foam wing.
The original design had no spar, just a little [too little] glass over balsa.
It was just 2 channels and about 27-28 ozs IIRC.
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Old 03-05-2009, 08:11 AM
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Default RE: From yet another box of stuff in the shop comes..


ORIGINAL: combatpigg

MJD, I vote for something like a GLH. It'll be fast enough to be fun and a simple build. To simplify the build, make the wing nonremovable. This can also save weight [unibody].
I built something very similar years ago for a ST .15 and had to retrofit an additional spar into the sheeted foam wing.
The original design had no spar, just a little [too little] glass over balsa.
It was just 2 channels and about 27-28 ozs IIRC.
But a GLH doesn't look like a nocturnal blood-sucking creature.. []

So.. did you fold the wing or did it just flap helplessly at speed? Based on the 160 mph Webra .12 powered thingy from the Speedcup of 20 years ago, a fellow ought to be able to get a hot .15 to 120 without too much trouble..? Maybe not with an open pipe though. Whatever, it is a good way to get the engine in the air quickly. Hopefully down more slowly.

I toyed with routing spar slots top and bottom and dropping in CF capped 1/8"x1/4". It is also not much work just to inlay a full depth spar to about 2/3 span and fair it in. Seal it all off with light glass and a bit more in the center and Bob's your uncle.

Admittedly.. it is also not much more work to cut new cores and make stronger wings from the start. But hey! This is a recession gd-it, and I'm gonna reduce, reuse, and recycle.

I bought a Graupner 6-5.5 speed prop - not a lekkie but a real prop supposedly - and I dunno but it looks awfully spindly for the block of metal I'm supposed to bolt it to. Plus, the TE extends so far back at the hub-blade transition that it hits the carb. Some would call that a sign to remove the carb and fit a venturi. Gotta order some odd sized from APC anyway, may as well stock up on fast .15 props now.

The aircraft would look pretty cool with a bottom mounted wing and a little canopy thingy like a Pacer. I have Pacer plans downstairs actually, I should look at them again before finalizing the shape of the balsa box that holds all the useful bits together. But yeah, shoulder mounting has a few advantages doesn't it. Still doodling. Sometimes a guy can crack off 2-3 smaller projects in a hurry when the motivation strikes, so I'm trying to ride that wave for a few more days here and beef up my spring test flight schedule. Then it's time to cut parts for the .65 bird.

But the first job this morning will be to finish cleaning the wood stove, put the pipe back on and find some wood. It's kinda cold in here right now.. yikessssss.

MJD

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Old 03-05-2009, 10:12 AM
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Default RE: From yet another box of stuff in the shop comes..

The wing never folded, it was fine for a few flights but developed "inflight dihedral syndrome'.
It was set up with conservative ailerons at first, that I got bored with. I made a new set with more chord at the tips than at the root and it turned into a rollin' ****. The plane came about [like your plane here] because I had some spare sets of 1/2A C/L combat wings laying around just collecting mouse droppings.
I think if you wanted to do a Batwing, you would need more wing area than what you show.
Sinking in a full depth spar.......attach that wing to a sheet of particle board or plywood and tilt the whole works down along side a rip fence until the entire table saw blade is poking through, the run the jig back and forth until the slot is complete. The wing can be held snug to the jig by surrounding it with wood blocks and clamping it over the top with a screwed down scrap of 1x2.
If you make it low wing, consider hand launching
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Old 03-05-2009, 11:32 AM
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Default RE: From yet another box of stuff in the shop comes..


ORIGINAL: combatpigg

I think if you wanted to do a Batwing, you would need more wing area than what you show.
Sinking in a full depth spar.......attach that wing to a sheet of particle board or plywood and tilt the whole works down along side a rip fence until the entire table saw blade is poking through, the run the jig back and forth until the slot is complete. The wing can be held snug to the jig by surrounding it with wood blocks and clamping it over the top with a screwed down scrap of 1x2.
If you make it low wing, consider hand launching
Nah, no flying wings right now - conventional layout.

Going low wing, a couple of degrees dihedral to get the tips off the ground, no plans to use landing gear whatsoever of course. I still have the foam nests from the wing cores, and they'll do a good job as the basis of a holding fixture if I DS-tape them down to some particle board - this is how I figured I'd do it. And my flying buddy has a really nice table saw with sharp blades and all that fancy stuff.

For the fuse I figure 3/32" balsa with a light glass skin, and structural reinforcement internally as deemed necessary.

Hey CP - if the torque rods are about 5" long, they'll be too springy in 2-56 rod right? I was looking at that last night and I think for the extra 5-6 grams it would be prudent to go 4-40 for stiffness. I don't want to fair in separate servos on this little thing.

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Old 03-05-2009, 12:20 PM
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Default RE: From yet another box of stuff in the shop comes..

I would look into making the torque rods out of 1/8" or even 3/16" aluminum welding rod.....with the legs inside the fuselage hammered flat and drilled for your clevis pins.
If you select the right alloy of rod, they can be bent without cracking. I routinely make elevator half joiners the same way.
With a swept trailing edge, you might need a knuckle threaded to the inner legs of the torque rods, in this case 1/8" alum rod can be slightly flattened and threaded 4-40 to accept nylon horn brackets.
One thing I've never tried is 2-56 steel wire encased in FG or CF tubing for a torque rod. If glued really well, it might eliminate twistyness?
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Old 03-05-2009, 12:46 PM
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Default RE: From yet another box of stuff in the shop comes..


ORIGINAL: combatpigg


One thing I've never tried is 2-56 steel wire encased in FG or CF tubing for a torque rod. If glued really well, it might eliminate twistyness?
Depends a lot on the fiber orientation of the tubes - if they are pultruded CF, the majority of the fibers are axial, and this is not condusive to torsional stiffness - but they are great for pushrods and tensile loads. You need a significant percentage of helical fibers for torsional strength and stiffness - so that the fibers are subjected to a tensile force when torque is applied, which is where you'll see the stiffness of CF shine. So I would check this out before committing a model to it - you may be fine, mebbe not. They will have some baseline level of stiffness inherent to the resin's properties and even with the poor average fiber orientation, but it may not be enough. I twisted at a 1/8" OD CF tube last night, and I am sure I detected some twist with the modest amount of torque I was able to apply by hand. Another thing to consider is that with the vast majority of fibers axially oriented the tube will split fairly easily under torque loads.

I'd say make up a sample and compare - one of us should be able to get to this today sometime, but I have to go cut some wood first. The missus doesn't handle the chill too well, somehow it affects her temper directly.

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Old 03-05-2009, 12:59 PM
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Default RE: From yet another box of stuff in the shop comes..

The 1/8" aluminum wire is sufficient for .15 and under. We used to use it a lot on .35 and under C/L planes.
....but definately a no-no for .36s.

I just hate to see 14 inches worth of 4-40 steel used here for a pair of flaps.
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Old 03-05-2009, 02:35 PM
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Default RE: From yet another box of stuff in the shop comes..

Ok, here's my drawing, idea is the engine mounted 45 degrees from inverted so the pipe can still run in a bellypan under the wing, 1.5" spinner, 32" long, mid wing, just kinda sleek, belly pan might be able to be made smaller, don't know the dimensions of the pipe, not that I dimensioned anything, just used the TLAR method
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Old 03-05-2009, 03:01 PM
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Default RE: From yet another box of stuff in the shop comes..


ORIGINAL: LGM Graphix

Ok, here's my drawing, idea is the engine mounted 45 degrees from inverted so the pipe can still run in a bellypan under the wing, 1.5" spinner, 32" long, mid wing, just kinda sleek, belly pan might be able to be made smaller, don't know the dimensions of the pipe, not that I dimensioned anything, just used the TLAR method
Someone actually drew one! Cool..

Well, I must say that looks nicer than mine. That Definitely Looks "AR"+. I pondered one version with the engine like that and a shoulder wing. It would look a lot more purposeful than yours (in other words mine would be ugly). I was shying away from any curvy bits, although I know rounded fuselages are slicker.

Hmm... more smoke from the ears, more doodling.

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Old 03-05-2009, 03:34 PM
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Default RE: From yet another box of stuff in the shop comes..

Ok, not quite as pretty, but no curvy bits, inspired by a Hots, and a nice T tail
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Old 03-05-2009, 05:54 PM
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Default RE: From yet another box of stuff in the shop comes..

Those are great looking drawings LGM! I could see them as C/L stunters, too.

Too bad 4 pound timber doesn't exist, or swoopy designs like this could be knocked out in one evening.
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Old 03-05-2009, 08:31 PM
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Default RE: From yet another box of stuff in the shop comes..


ORIGINAL: LGM Graphix

Ok, not quite as pretty, but no curvy bits, inspired by a Hots, and a nice T tail
Good eye candy. I have yet to order the darn pipe, so so far I only have tuning length dimensions to work from. Must remember tomorrow.. must remember..

I have a quandry - this wing is already done but I don't think I would duplicate it exactly next time around. It came from a kit and I'd likely change the airfoil a bit. So.. I'll stick to a wood fuse for now rather than carving a plug just yet. I think knocking out a quickie right now to test out the general size, layout, and all that, plus to get some quality time with the engine is a good plan. If I like it, mebbe time to get cooler with the fuse. Perhaps by then I'll have scrounged an FAI speed .15, or at least a rear exhaust QM engine. One day I have got to see a full-Monty speed .15/pipe/prop combo running on a small RC model.

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