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

Screamin' Demon cowl plug #2 - nearly done!

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Old 10-28-2009, 09:15 PM
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MJD
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Default Screamin' Demon cowl plug #2 - nearly done!

One more coat of surface primer to go, then polish. How's it look to you gearheads? The idea was it would accomodate a RE engine but with part of the header exposed and the pipe hanging out back. It was drawn around a Nelson .40 because it has a fattish head and I thought it well defined an envelope that should hold most anything in the "small block" category. I checked it against an OS muffler and a Jett, and they clear it nicely near as I can see.

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Old 10-28-2009, 09:21 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

Looks nice, this going on you SD?
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Old 10-28-2009, 09:23 PM
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Mike Connor
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

Lookin good. A universal cowl would be a popular item.
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Old 10-28-2009, 09:26 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

It goes on mine first, then if I like it I'll make 'em and put 'em on my website as an accessory.

Then I'll get to the full pipe tunnel model. I will likely make an add-on for this being the lazy bum I am. But it might work out. Have to whittle out a rough one first to figure out if the picture in my head is out of focus, if you know what I mean. I play a mean 2D CAD, but 3D modelling is beyond my dated and meagre skillset.

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Old 10-28-2009, 09:44 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

It looks like a classic!
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Old 10-28-2009, 09:46 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

me like.
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Old 10-28-2009, 10:19 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

There's something prophetic about the fact that it is currently screwed to an Eggo waffle box. I think Eggo waffles would be an excellent paint scheme for my Stits covered Demon to which this cowl will be first fitted. When I'm ready for my oil-saturated and gagging helper to launch I can yell "Leggo my Eggo!". Waffles need syrup, I'll make him hold on to it WFO for 10-15 seconds while I "psych up".. [>:]

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Old 10-29-2009, 05:30 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

great cowle,love the waffles, Hope you can stop that vibration issue cp had with his shaking itself loose.
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Old 10-29-2009, 07:25 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

We'll see when it gets stuck on some high rpm monster first time I guess. The tank compartment is fairly high, but I decided to add plenty of deck height to allow foamk for the clunk users, and also to clear the 10 and 11 ounce tanks I was phutzing with re bladder conversions. I hope it works out okay for exposed-pipe RE installations.

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Old 10-29-2009, 08:19 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

Guess it could be cut for side exhaust engines too
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Old 10-29-2009, 11:15 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

If you make the cowl relatively light it will hold up everywhere else, but the screw hole area needs to have extra layers so that the build up is at least 1/16" Sleeving the holes with little hunks of brass tubing might also keep the screw from crushing and digging into the cowl. Notice that the German planes might have wire hoops to stabilize the cowls.
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Old 10-29-2009, 11:38 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

lookin good, it should be popular.
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Old 10-29-2009, 01:38 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!


ORIGINAL: mk1spitfire

Guess it could be cut for side exhaust engines too
Actually that is what I had in mind for this one, it is really more the side exhaust than the rear exhaust version. It was intended to cowl the engine, let the muffler hang (what else you gonna do?), look a bit cool like a speed CL cowl, and also to streamline the tank area. The rear of the tank area could probably be a bit more intelligently profiled, but no doubt it will clean things up to a fair degree. I'm shaping a pushrod fairing plug today as well.

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Old 10-29-2009, 07:01 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

How much speed loss is there from side exhaust engines,what % dragg is added do you think. RE the way to go for the 200mph club?
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Old 10-29-2009, 07:49 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

I dunno a number, but it is significant and I wouldn't be running SE if I was going for ultimate speed.

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Old 10-29-2009, 09:13 PM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!


ORIGINAL: mk1spitfire

How much speed loss is there from side exhaust engines,what % dragg is added do you think. RE the way to go for the 200mph club?
The side exhaust gives you more frontal area, as well as the sides, if your goal is in the 200 range you are going to need a piped engine (rear exhaust preferably) I would think. The rear tuned pipe would help keep the frontal are down, and the straight out exhaust would be a much better setup.
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Old 10-30-2009, 12:24 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

Yeah but the side exhaust engines turn right quicker because of the side exhaust drag. wink, wink
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Old 10-30-2009, 07:14 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

CP just did over 200 with a side exhaust Nelson on a Screamin' Demon. I think it has a lot more to do with what engine it is than the exhaust orientation.

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Old 10-30-2009, 07:17 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

ORIGINAL: mk1spitfire

How much speed loss is there from side exhaust engines,what % dragg is added do you think. RE the way to go for the 200mph club?
RE engines exist in order to allow those last mph that are hindered by the more convenient but much draggier SE configuration. So if you want to reach the stars you gotta go all the way. I really don't know, if a hotsy SE piped engine was in something as clean as possible. whether it could do it or not. Look at the effort it takes to crack 200 as it is, and remember drag goes up with v^2 - including pipe and header drag. Mebbe with a canted engine, cowled exhaust, and an odd canted cylinder cowl.. who knows?

MkI - it is your mission to find out.. Are you gonna be the first SE exhaust-in-the-breeze guy to do it?

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Old 10-30-2009, 08:41 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

Yer would love too.
I think theres enough power in some side exhaust engines to clock 200mph and overcome it own exhaust drag. It just that I believe the airframe aerofoil is the ticket to keep drag low.,I was curious to know about slippery delta aerofoils and am chuffed the Deamon is delevering.!!

How will your ops vs 40fai prevail?
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Old 10-30-2009, 08:55 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

I wish I had one of those! Only .60's and .65's.. [&o] Well and a marine .45 but it's in use. With luck the boat will break, then.. [>:]

Okay - finished with surface primer, all wet-sanded, and polished with 2000 grit Aquabuff. Looks about as good as it is going to get, so now for the carnauba wax.

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Old 10-30-2009, 09:31 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

I may have spoken a bit too quickly about CP's Screamin' Demon. I am not sure if his Nelson is rear exhaust or not.

I have been a course worker for the pylon races for several years but I never learned very much about the equipment. I know the Q40 Nelsons are RE and they are the fastest class that was flown in Orlando.

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Old 10-30-2009, 10:23 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

It's an FAI engine and they are RE. QM and Quickies are SE.

I think I got that right.

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Old 10-30-2009, 11:29 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

It's an FAI engine and they are RE. QM and Quickies are SE.

I think I got that right.
You got that right.

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Old 10-30-2009, 11:38 AM
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Default RE: Screamin' Demon cowl plug #2 - nearly done!

So Ed, while I got yer attention here.. am I going to cook engines with this cowl, or does it look like it will work okay with the right holes in it? I sized the interior around a Nelson with .1" clearance. I figured with an oval or T inlet and some appropriate exit opening(s) on the rear of the cylinder cuff, it would pull air through there okay..? Maybe with smaller jugs a bit of material added to the sidewalls and around the case..?

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