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Screaming Demon big block bash

Old 09-30-2009, 09:56 AM
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Default RE: Screaming Demon big block bash

won't you blast everything behind in your workshop if fire that beast up in there mike
Old 09-30-2009, 10:04 AM
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Default RE: Screaming Demon big block bash

Some would say that might be the best thing for it. Especially if I open the windows first.

If I wait too long I will be running indoors. It was bitter cold and dismal grey yesterday, with fine mist blowing almost parallel to the ground. A bit like where you live 200 days of the year..

MJD

p.s. where "south" in UK are you? My dad's folks were from Dorset, and the name comes from that area too. My folks met in London, she was a WAAF on radar, my dad was in radar at bomber HQ.
Old 09-30-2009, 04:52 PM
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Default RE: Screaming Demon big block bash

Nice to see you underestamated
A bit like where you live 200 days of the year..

Know that area very well, I believe swanage was an experimental radar testing area. Churchill came there i'm told
Old 09-30-2009, 06:22 PM
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Default RE: Screaming Demon big block bash

Speaking of radar and southern England, my siblings and I found out only months ago that my dad, who always waved off what he did as installing and fixing radar somewhere around London, was stationed at RAF bomber HQ for his whole term of service and was a squadron leader with Pathfinders. He also led a delegation that traveled to MIT to debrief the US on radar technology. Might have mentioned all this interesting stuff when he was alive. Radar was his area of expertise. So we have some research to do! Live and learn. With my mixed German and British heritiage, I have these two personalities that constantly hurl insults at each other. But I am very fond of German V weapons, Spitfires, pulsejets, and small quirky diesel engines.

MJD
Old 10-02-2009, 01:41 PM
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Default RE: Screaming Demon big block bash

This is getting ridiculous!

This is the 10% smaller bench running prop made from the other 8.25x10 I had. No way am I making it any smaller.. [:-]

Mixed up a gallon of fuel I have dubbed "OPS brew", meaning this is what I'm using and sticking to until I have reason not to - 12.8% castor, 7.2% syn, 5% nitromethane, 75% methanol. That's what you get when you mix FAI fuel and 10% syn/cas sport fuel 50/50, then add castor to bring total oil to 20%. Seemed a sensible mixture and easy to replicate via a trip to one of two LHS's. And I have one head shim installed for now.

The pipe is set at 12" plug to high point to start, and it will likely end up towards 11" by the time I'm done. I have set the pipe up clamped to a piece of u-channel, actually shelf bracket track, you know the stuff. So it is easily loosened, moved, and re-anchored as I trim the header. I wrapped the part where the clamp is with a few turns of that clingy silicone repair tape.

The plan is to meet up at my buddy's garage around 8pm and set up the stand, and a camera/tripod to record the festivities. We're having an OPS party.. grunt grunt, who let the geeks out. So hopefully something will occur that I am not ashamed to post. I suspect it will run very fast and scare us. [>:] Yes I will warm the head, start it, pin it, and get it staged into a rich 2c right away. One minute runs, cool, repeat..

Whee.

MJD
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Old 10-03-2009, 06:48 AM
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Default RE: Screaming Demon big block bash

Sounds like one serious NERD FEST[sm=49_49.gif], I like the sounds of that, I'm curious how this OPS runs.
Old 10-07-2009, 05:26 PM
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Default RE: Screaming Demon big block bash

Installed servos, radio gear and got a pipe. Next up will be making some sort of cowling/hatch (does anyone have ideas on the best way to do that) and making the wingtips.
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Old 10-07-2009, 07:01 PM
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Default RE: Screaming Demon big block bash

LOOkin very sweet, and appealing, nice job, my Webra .80 RIRE would look nice in one of those.
Old 10-07-2009, 07:55 PM
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Default RE: Screaming Demon big block bash


ORIGINAL: RVman

Installed servos, radio gear and got a pipe. Next up will be making some sort of cowling/hatch (does anyone have ideas on the best way to do that) and making the wingtips.
I started using 1/64" ply more and more since building my first Demon. With that, some internal formers and a layer of glass to finish you can do wonders. It forms around fairly tight simple curves, though not compound curves of course. I did the bottom fairing around the nose ring and back behind the engine opening with one rectangle of 1/64" ply, then glassed it and like the results.

This does not constitute a complete answer I know. But my point is that I should have started using 1/64" ply earlier. CP was also working on me recently to do something with it, he's already seen the light.

As to "how to", what's wrong with the instructions? [&o]

MJD
Old 10-07-2009, 08:27 PM
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Default RE: Screaming Demon big block bash

thanks, I've got a few ideas now and we'll see what comes out of it.
Old 10-07-2009, 08:55 PM
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Default RE: Screaming Demon big block bash

The guys who used to build planes with plywood siding steamed the panels and then they could be forced into compound curves. I bought a 2 foot by 4 foot sheet of 1/64" plywood a few years ago...don't remember the exact price except it was North of $40 [IIRC].
Each ply is 1/194", not counting the glue?
Old 10-07-2009, 09:28 PM
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Default RE: Screaming Demon big block bash

1/192"? I think the outside plies are thinner actually, it gets sanded to final dimensions.

It's cool stuff isn't it? I have a collection of indoor contest grade wood including some .006" and .008" sheet. I like just fondling it and imagining if my fingers were smaller or I was patient. Pennyplanes were pushing it for me, at 7-8 hours build time.

MJD
Old 10-10-2009, 11:05 PM
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Default RE: Screaming Demon big block bash

Finished up a cowling and hatch that seems like it should work alright. Just needs some filler here and there. Do the cooling openings look sufficient?

It was snowing here this morning [X(].
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Old 10-10-2009, 11:26 PM
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Default RE: Screaming Demon big block bash

Looks like the cowls at the SpeedCup! Did you have fun?
Old 10-11-2009, 09:31 AM
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Default RE: Screaming Demon big block bash

Lookin' good Tom, its very motivating to look at your progress, we'll have to get together some time.
Old 10-11-2009, 09:48 AM
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Default RE: Screaming Demon big block bash


ORIGINAL: RVman

Do the cooling openings look sufficient?
The exit size should be 1.4 times the the entrance. Looks like it needs to be tapered down a bit in the rear.
Old 10-11-2009, 12:32 PM
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Default RE: Screaming Demon big block bash

Thanks Mike, also the header & coupler will take up some of that space. I haven't got the header yet but I'll keep the 1:1.5 ratio in mind. It will be easy to add a few blocks of balsa to the inside to make it smaller if needed.
Old 10-11-2009, 01:33 PM
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Default RE: Screaming Demon big block bash

Do the cooling openings look sufficient?
The important thing when cooling is not the size of the opening. It is more important to force the incoming air through the fins and not allow the air to go around the head. There is very little need to have cooling air playing directly on the front of a rear exhaust engine. The transfer port is at the front with cold fuel traveling through it. The cooling air should be ducted to the sides. See the pictures.

The pictures show a cowl from an F3D Pylon Racer. There is a shroud that is a tight fit on the upper engine. This shroud forces the ducted incoming air through the fins and around to the rear outlet. There is about 1/8"learance betwwn the pipe and the inner wall of the cowl. Again this forces the cooling air where it is needed. Without this type of ducting and shroud the incoming air will have little effect. Another advantage of this controlled cooling is that a constant engine temperature can be established.

There is nothing new or revolutionary here. Control Line team racers and Speed flyers have used this for years. The VW bug used it in the thirties. Take look at some pictures of WW1 aircraft engines of ninety years ago.

Ed S
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Old 10-11-2009, 01:41 PM
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Default RE: Screaming Demon big block bash

Tom,
Maybe extend it back and taper it down. The trailing edge shape is important when it comes to drag.
http://www.grc.nasa.gov/WWW/K-12/airplane/shaped.html
It looks like it will be fast no matter what you do.
Old 10-11-2009, 02:01 PM
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Default RE: Screaming Demon big block bash

Ed, the gaps around the cylinder are all about 1/8" so that should be ok. I will try to make up something better for the header. Thank you for the info,

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