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Screamin Demon 25 prototype build

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Screamin Demon 25 prototype build

Old 02-10-2010, 04:41 PM
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MJD
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Default Screamin Demon 25 prototype build

Nyuk nyuk, just fishtailed and skidded back from the armpit of Ontario with the first two sets of bits for the 26" span Demon prototypes.

I've been calling it a .25 size, but it is well proportioned for a .15 too, and I will test it on a venerable old FP .15 first to represent the performance someone would see with their favorite old sport .15. Then the OPS Speed .15. Then.. we'll see. There's already a .25 VF-DF version waiting to fly so that's covered. Need a Jett .35 now. Mommy?

26" span, 336 square inches, projected weight 1.5 - 1.8 pounds with a .15 (projected is a synonym for a wild-assed guess, note the wide range), subtle differences in internal structure to open up the tank compartment a bit.

I'll build a second for the motor system out of my Simple 400. It will be a useful comparison with apples-to-apples in the engine bay.

Here's a really exciting picture..

MJD

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Old 02-10-2010, 05:13 PM
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Default RE: Screamin Demon 25 prototype build

Nice laser cut pieces, my scroll saw can't match that.[&o]
Old 02-10-2010, 05:48 PM
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Default RE: Screamin Demon 25 prototype build

Yeah, but yours is already done, so no smart talk from me..
Old 02-10-2010, 08:15 PM
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Default RE: Screamin Demon 25 prototype build

I think a $40 Magnum .15 and one of these planes will be at the top of that "Best Bang For The Buck" category. To take it a little further, the really hot .15s do show up NIB for great prices often enough.
Too bad so few know about the big time performance you can get for so little in the .15 size.
Old 02-10-2010, 08:38 PM
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Default RE: Screamin Demon 25 prototype build

well I have a jett 35 bse rear exhaust and it did 190 on my LR1 at 3.1 lbs and a 8x7 or 8x8 prop. so maybe i should get one of these.
Old 02-10-2010, 08:47 PM
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Default RE: Screamin Demon 25 prototype build

ORIGINAL: combatpigg

I think a $40 Magnum .15 and one of these planes will be at the top of that ''Best Bang For The Buck'' category. To take it a little further, the really hot .15s do show up NIB for great prices often enough.
Too bad so few know about the big time performance you can get for so little in the .15 size.

We'll find out what this can do ona .15. I have several candidates, except for an Irvine F2A speed. Later, later.

Looks like I just bought a RIRE Cyclon PR for 6.5cc speed model hijinx. Whee.. NC speed rally here we come.

MJD
Old 02-10-2010, 08:57 PM
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Default RE: Screamin Demon 25 prototype build

Comon Spring!
Old 02-10-2010, 09:02 PM
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Default RE: Screamin Demon 25 prototype build

I never heard of a Cyclon 6.5, but it must be pretty good! I'd like to see his operation someday.
Last time I contacted him for a .061, he came back with a huge price increase from a year earlier. I told him I thought the price was too high and his reply was....."well, how much do you want to pay?"
I thought that was pretty cool.......
Old 02-10-2010, 09:06 PM
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Default RE: Screamin Demon 25 prototype build

ORIGINAL: MJD

Nyuk nyuk, just fishtailed and skidded back from the armpit of Ontario with the first two sets of bits for the 26'' span Demon prototypes.

I've been calling it a .25 size, but it is well proportioned for a .15 too, and I will test it on a venerable old FP .15 first to represent the performance someone would see with their favorite old sport .15. Then the OPS Speed .15. Then.. we'll see. There's already a .25 VF-DF version waiting to fly so that's covered. Need a Jett .35 now. Mommy?

26'' span, 336 square inches, projected weight 1.5 - 1.8 pounds with a .15 (projected is a synonym for a wild-assed guess, note the wide range), subtle differences in internal structure to open up the tank compartment a bit.

I'll build a second for the motor system out of my Simple 400. It will be a useful comparison with apples-to-apples in the engine bay.

Here's a really exciting picture..

MJD

Let me know when you get them boxed up and ready to ship...

Baby Demon,,,,,, with screaming brat on the box label.
Old 02-10-2010, 10:15 PM
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Default RE: Screamin Demon 25 prototype build


ORIGINAL: Broken Wings

Let me know when you get them boxed up and ready to ship...

Baby Demon,,,,,, with screaming brat on the box label.
I gotta do labels? I should. Good idea..

Gotta test it first, try to be patient (like I am.. right!), but I am already framing it up this evening. And finding my booboos (minor, no holdups).

MJD
Old 02-11-2010, 01:03 PM
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Default RE: Screamin Demon 25 prototype build

Framing 'er up.

The trick with these as I have learned is not to piddle around but simply set yourself to fixturing them from the start. Two rails for the CF spars, and something to hold the TE level at the right height. I use rubber bands to hold the spars as you can see, by crudely Dremeling a notch in the end of two scraps of scrap corner cove stuff I had shoved in the rafters. A few shims to deal with discerpancies in height too, as in here where after applying the TE sheeting the rear spar is off the rails. No sweat, equal thickness shims on each side and off we go again with everything parallel to the board again. I now take a couple of minutes on each model, and tack in some 1/8" square balsa along the LE to support the sheeting from getting bowed downwards. I draw a for reference as you can see, then quick CA a few scraps in place.

These steps sound like extra work, but the net effect is less work and a straight airframe. She'll be flying within the week I bet. Maybe I'll just drop the OPS in it for now and the FP later..

MJD

p.s. yes, I see the carb is loose.. . And note that the prop says "Speed prop" so it must be fast.
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Old 02-11-2010, 01:43 PM
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Default RE: Screamin Demon 25 prototype build


ORIGINAL: combatpigg

I think a $40 Magnum .15 and one of these planes will be at the top of that ''Best Bang For The Buck'' category. To take it a little further, the really hot .15s do show up NIB for great prices often enough.
Too bad so few know about the big time performance you can get for so little in the .15 size.

Bang on. That XLS deal for $39.99 plus one of these and you'd have a little winner. If it swings a 8-3 at 17k, that is in the ballpark of a stock Conquest's capabilities. Mind you the Conquest really starts to haul on the smaller props, so dunno how this fares up in the low 20's, but undoubtedly someone will report back sometime in the near future.

MJD
Old 02-11-2010, 05:55 PM
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Default RE: Screamin Demon 25 prototype build

So far just over 3 oz with bottom center and LE sheeting in. I like the weight so far, and this is going to be one rigid little airframe.


I hate LE sheeting.
I hate LE sheeting.
I hate LE sheeting.
I hate LE sheeting.

That's four times, for the four pieces it needs. I have to change that, it is such a total PITA! I have a crafty idea that started festering lately regarding the regular Demon. But the stock method is the one sore point with me about building these. And I'm supposed to like everything about them, right?

MJD
Old 02-11-2010, 06:36 PM
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Default RE: Screamin Demon 25 prototype build

ORIGINAL: MJD

...
I hate LE sheeting.
I hate LE sheeting.
I hate LE sheeting.
I hate LE sheeting.

... I have to change that, it is such a total PITA! ...
MJD
I agree. Here is what I am doing on my current wing build of similar construction. Drop the leading edge balsa stick back to 3/16" sq and have the sheeting go over the leading edge to the point. Same amount of wood for strength but easier, faster and stronger...as long as the balsa is light and flexible (or wet).
Old 02-11-2010, 07:17 PM
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Default RE: Screamin Demon 25 prototype build

I have a watchful eye on this one, thinking this could be a match for one of the bargain Hobby City outrunner setups.I have a boxfull of the 3 cell Zippy 2200 packs and love the performance of my two planes with similar power.
http://www.hobbycity.com/hobbycity/s..._1100Kv_/_770W
I feel that with the right props this is a cheap fun option that could be used.
MJD,What is used for the power in your 400 plane?
Anyone?
Danny
Old 02-11-2010, 07:41 PM
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Default RE: Screamin Demon 25 prototype build

If the leading edge spars were rabbetted to receive the sheeting, that would be slick.

Old 02-11-2010, 07:57 PM
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Default RE: Screamin Demon 25 prototype build


ORIGINAL: combatpigg

If the leading edge spars were rabbetted to receive the sheeting, that would be slick.
Wouldn't they hop off the bench?

MJD
Old 02-11-2010, 08:03 PM
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Default RE: Screamin Demon 25 prototype build

ORIGINAL: hotrodblazer
MJD,What is used for the power in your 400 plane?
Anyone?
Danny
It's an E-Flite Series Six 2700kV motor, with 3S 2100 25C pack and one of my controllers that isn't fried at the moment, forget which. With a CAM 5x5 it pulled 33 amps static, but eventually I found that the aircraft performed a hair better with an APC 5.1x4.5 - it is a 15% thick wing after all. It Wav-O-Scoped at 208kph on the APC prop.

Any kit/scratch builders probably know what I am talking about when I say that in my hands, the airframe "feels" perfect for a .15 (and also feels like it will happily take a .25). I also think it will perform very, very well on the lekkie setup I have for it.

I hate LE sheeting.

MJD
Old 02-11-2010, 08:04 PM
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Default RE: Screamin Demon 25 prototype build

[sm=tired.gif]...........[I couldn't find a smiley guy with his eyes rolled back into his head.....]
Old 02-11-2010, 08:08 PM
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Default RE: Screamin Demon 25 prototype build

C'mon CP I couldn't help it.. [sm=tongue_smile.gif]

Yes it is a slick idea.

Other ideas involve a material of which you are quite fond, 1/64" ply, and the other does not involve wood but is cheap and quick.

I've calmed down over dinner, and will now bravely tackle the top LE sheeting. Once that is done I can breath a sigh and get on with it.

MJD
Old 02-11-2010, 08:11 PM
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Default RE: Screamin Demon 25 prototype build

ORIGINAL: Mike Connor
I agree. Here is what I am doing on my current wing build of similar construction. Drop the leading edge balsa stick back to 3/16'' sq and have the sheeting go over the leading edge to the point. Same amount of wood for strength but easier, faster and stronger...as long as the balsa is light and flexible (or wet).
And there's a nice big flat to CA it to to get it started. Then bend and bond. I'll look at it.

MJD
Old 02-11-2010, 08:48 PM
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Default RE: Screamin Demon 25 prototype build


ORIGINAL: MJD

And there's a nice big flat to CA it to to get it started. Then bend and bond. I'll look at it.

MJD
One of my complaints is getting the less then perfectly straight sheeting to mate to the less then perfectly straight leading edge. With the method I use now you can leave a slight overhang that can be sanded off if not straight.
Old 02-11-2010, 09:06 PM
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Default RE: Screamin Demon 25 prototype build

3/16x3/16 spruce.
Old 02-11-2010, 10:27 PM
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Default RE: Screamin Demon 25 prototype build

On my own regular size Demons I used 1/4" spruce for the LE's, and far prefer it to balsa. I think I told you Mike, I did indeed crunch a bit of one indestructible LE finally last fall, something was poking up in the field I never saw. Nothing to repair, peel back the covering, CA it up, recover, done.

I'm this far now, bored of hiding in the cold dungeon with nobody nagging me. Everything but top sheeting, plus unsanded tips and fins = 153 grams / 5.4 ounces. I think that's okay. Not much time in the build so far.

5.4 + maybe 2.5 more? = 8oz, plus covering = 9.2 - 9.4 oz with neon, plus radio = 12, plus 3 ounces for a tank and bit of glass at the tips and everything I forgot = 15, plus engine = [8D]

This thing might be lighter than I thought, .. maybe 25oz? With 366 squares = 9.8 oz/sq ft.

Seems to be working out.

MJD
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Old 02-11-2010, 10:33 PM
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Default RE: Screamin Demon 25 prototype build

And to think, I just ordered a Magnum XLS.15.
With all the talk of Wonders on here lately, I thought I would build another one.
Then Hobby People had to go and tempt me with that $39.99 price on the Magnum engine, I could not resist.
I think now I will wait for the flight report an availability of this one.

Tim

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