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Old Dec 21, 2004, 11:53 AM
IAD
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Burt Rutan's Pond Racer, Shockflyer Style

Thought I would share my latest Bluefoam experiment...

A 36" span Shockflyer-style Pond Racer, to be powered by two IPS-A units and a 2-cell 700 mAh E-tec pack. Controls will (naturally enough) be throttle, aileron and elevator.

I managed to get 138"^2 of wing, without stretching anything. With an AUW of hopefully under 8 oz., it should have a decent wing-loading, and remain a fairly tame small-area flyer.

~Luke

P.S. Ignore the chess pieces. CG finding procedure. You know, tape weight, glide, move weight, repeat.
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Old Dec 21, 2004, 12:08 PM
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Looks pretty cool, but that wing seems on the small side... Question - where will the battery go to get the right CG? The center area doesn't have any foam far enough forward...
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Old Dec 21, 2004, 12:55 PM
IAD
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Nah, there's plenty of wing... (Famous last words. ) Seriously, though... This isn't a 3D ship, and 7-8 oz/ft^2 isn't too bad at all. For some reason, the Pond Racer has a bad rep. in re: wing area. It actually has quite a bit, for a given span.


The center pod actually reaches all the way to the LE of the wing. I was planning on putting the battery about there. Still behind the CG, but with a couple 1 oz. motors all the way forwards, the elevator servo up next to one of the motors, and maybe a couple ESCs, for differential thrust, it should balance. And if it doesn't, dead weight to the rescue!

~Luke
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Old Dec 21, 2004, 03:07 PM
IAD
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Just an update: The wing area is fine, I just flew it around on the last of a battery charge, and it was quite flyable, did some nice pylon turns, but unfortunately, the battery was probably down around 6.75 volts or so. Needless to say, it was underpowered in that state. Need to charge that LiPoly!

Bottom line: It flies, and does so like a park/indoor flyer.

~Luke

<<Edit: Just ran it with a 8-cell 650 KAN pack, AUW 9.33 oz. Still no problems with the wing loading.>>
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Old Dec 21, 2004, 03:22 PM
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Quote:
Originally Posted by IAD
Just an update: The wing area is fine, I just flew it around on the last of a battery charge, and it was quite flyable, did some nice pylon turns, but unfortunately, the battery was probably down around 6.75 volts or so. Needless to say, it was underpowered in that state. Need to charge that LiPoly!

Bottom line: It flies, and does so like a park/indoor flyer.

~Luke

<<Edit: Just ran it with a 8-cell 650 KAN pack, AUW 9.33 oz. Still no problems with the wing loading.>>

I NEED ONE!!!!!!! if at all possible could I get plans??? Pm me if this would be ok. Thanks Chris
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Old Dec 21, 2004, 03:48 PM
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Well, the funny part here is... There are no plans. I found a 3-view somewhere (I don't even remember where) and scaled them up this morning to have a 36" span.

I may draw up plans yet, but...
I'm recharging the batteries right now, so I'll probably get in one night-flight, during which I can finish assessing performance.

~Luke
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Old Dec 21, 2004, 08:05 PM
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Really Cool Luke!!


Bill
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Old Dec 21, 2004, 08:46 PM
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Plans for me too Luke! I agree there is eough wing area, after all this is a "racer" so a high take off speed would be understandable. less wing=less drag = more speed.

To turn this into a more well behaved parkflyer all one would have to do is make the wing just a tad bigger all around. Maybe 2" span increase and 1/2" to an inch in the chord. It might look a bit less scale but make some a little happier with its wing loading.

Me? I like it just as it is and because of the "Shock-flyer" treatment the horizontal fuse and boom pieces actually add a little "wing area as it is.

Robert
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Old Dec 21, 2004, 09:53 PM
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Once the Pond racer gets thrashed we wanna see ya make a Rutan Boomerang...
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Old Dec 21, 2004, 10:17 PM
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I don't see any reason to add any wing. The thing already turns on a dime without tipstalling. I can't imagine it being any better behaved.

I flew it in the backyard, which is a place rank with trees, bushes, etc. Granted, the battery was dead, so I didn't really get much testing in, but... There is definitely no reason to 'un-scale' the wing. (By the way, the wing loading is about 7.5 oz/ft^2 with the LiPoly...) The only thing I have to complain about is that the design feels very draggy, which, due to uncontoured LEs on the wing/tail, etc., it is. I'll see if I can't improve this, with a bit of sanding.

~Luke
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Old Dec 22, 2004, 07:26 AM
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Well, the good news, and the bad news:

Good news: Freshly charged LiPoly flight confirmed initial reports, it does fly, and flies quite nicely. Needs a regearing, though. Probably a pair of S2 drives would be better than the A drives. (Required near-full throttle to fly well.) Either that, or a higher-voltage pack. I'm leaning towards the first option.

Bad news: Have you ever seen an aileron-only plane do a knife-edge harrier? If I turn too tight, I go into a [very nice, coincidently] hovering knife-edge! (And since I don't have a rudder, I get stuck in it, too!) I'll adjust the CG.

~Luke
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Old Dec 22, 2004, 11:14 AM
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What props are you using with the IPS A drives? Did you go with differential thrust? What about the elevator? Cool looking design. It's hard to tell the scale from the photos, so I guess the wing area is OK. I tend to like my designs with plenty of area for that "floaty" feel
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Old Dec 22, 2004, 11:23 AM
IAD
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No differential thrust, I realized my twin ESCs were still embedded in another project. The elevator is joined by a bit of ply, which coincidently came apart, and needs fixing... I've got the 9"/7" on the IPS... Pretty good setup, but definitely needs either (a) more thrust, or (b) more prop-speed. It only flies well as long as the battery gives about 8 volts, which if you look at the discharge curves of a LiPoly, isn't very long at all. (Thus my plan to remotor/regear it.)

I wouldn't say it's floaty, but it definitely doesn't fall like a rock. Just sort of putters around. I would say it is similar to a Hobby-Lobby Rare Bear... (Not that I have ever flown one of those... But it looks about the same, maybe a bit slower, and definitely draggier.)


~Luke
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Old Dec 22, 2004, 12:13 PM
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Luke, I was wondering how you have your ailerons linked. Kinda looks like a pull pull set up. could we get some closer pics and a little more info?

Robert
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Old Dec 22, 2004, 01:27 PM
IAD
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I'll try and get some pictures... Here's the basic idea, though...

It is pull-pull, but with a twist. (One that personally, I don't like much, but I was desperate.)

The idea is... Starting at left aileron, working right...

Top cable:
Aileron horn-->plywood bearing-->servo-->plywood bearing-->aileron horn.

Bottom cable:
Aileron horn-->plywood bearing-->plywood bearing (under servo)-->plywood bearing-->aileron horn.

Yes, definitely a picture is in order, to explain this properly....

~Luke
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