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RE: Screamin Demon .65 build thread - 11/6/2009 4:10 PM   
MJD



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Status: offline 		I think you have me confused with you.. but it is coming along nicely! Two cups of tea down, three to go and ready to get at it. Bummer though, I have a gig tonight.. gotta wash myself special, dress purty and take off at 3:30.. now that seriously cuts into my building time.

And outside, a fine sprinkling of snow is threatening the end of the flying season.. the race is on.

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RE: Screamin Demon .65 build thread - 11/6/2009 8:17 PM   
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Status: offline 		An inflight adjustable needle normally has two adjustments, a finger operated needle and the inflight adjustable needle . The finger needles gets set in the middle of almost too lean and almost too rich. Then the inflight needle, which is hooked to a servo will fine tune the mixture in the air. The old glow ducted fans would use one for take off, cruise and fuel burn down. Full lean for take off, then cruise rich, then a little richer sometimes as the fuel was burnt off. I alwyas tried to set mine where full lean on the servo would not over lean the engine.

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RE: Screamin Demon .65 build thread - 11/6/2009 9:57 PM   
MJD



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Status: offline 		As the Perry unit is described, it has a manual adjustment to get the setting in the right range, then it adjusts up and down from there. I understand that if you had a needle on the carb or on the engine, you would set that to the rich side of where it should be and fine tune from there with the MCV. However, by the nature of its function it sounds like it could be used as the sole metering device in the system, and that's what I was wondering.

MJD

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RE: Screamin Demon .65 build thread - 11/6/2009 10:48 PM   
proptop



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Status: offline 		That's the way the BVM unit works...
I'm repairing a ICDF BVM Maverick for a friend...it has a BVM .91 in it, and there is no needle valve assy. on the carb...the mixture control does all the metering.

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RE: Screamin Demon .65 build thread - 11/6/2009 11:03 PM   
MJD



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Status: offline 		Okay, thanks proptop. It makes perfect sense that it does, but in case there was a reason I hadn't thought of..

So now I park the project until tomorrow sometime.. .. I hate it when I get going on something. It's getting real close to finishing time. The elevon assemblies are butt-glued onto the TE, and with the 3.2 ounce Dacron covering I can brush laminating resin through the fabric to any sheeted areas I want to fuse to something else. Not as tough as glass but honestly this stuff is freaking strong and when saturated in epoxy becomes a really tough skin. I need integrity more than I need the rigidity of glass, the airframe is already nearly impossible to twist without damaging the tips. The extra sheeting area really stiffens it up. I could have closed it in, but it is not needed with the Dacron covering, the stuff is good for 200mph on full scale aircraft at ten times the wing loading, and is so tight when shrunk at 350F you can use it as a practice pad if you're a drummer. So the small open bays are irrelevant even at the speed this thing is theoretically capable of.

Tips are laminated and curing - lower section is 3/8" x 2 TE stock tapering upwards and outwards looking from the front or back, center lamination is 1/64" ply, upper lamination is 1/4" A-grain, with grain running spanwise. The TE on the bottom cuts the sanding in half and gives a nice upsweep look to the tips lower surface, even though I set them up by setting a straight edge across the span on the top. I'll take a pic.

MJD

p.s. for a couple of milliseconds, I found myself looking at it and wondering "hmm, clipped wing or stock span?". Then I realized that was a stupid irresponsible idea and was ashamed for even considering it and am back to putting full 2" span tips on it. Using the stock wing is "clipped" enough as it is, if the wee tips make the difference now then the engine simply needs to be buried, not flown.

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RE: Screamin Demon .65 build thread - 11/7/2009 12:59 AM   
Mike Connor



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Status: offline 		The open bays will be pretty small when you get through. Any idea what it will weigh?

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RE: Screamin Demon .65 build thread - 11/7/2009 2:54 AM   
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Status: offline 		AHHH yes, lookin Sweeet!

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RE: Screamin Demon .65 build thread - 11/7/2009 4:36 PM   
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Status: offline 		Really like that hinging method, I suppose a table saw is the only way to do it properly to get even straight cuts.


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RE: Screamin Demon .65 build thread - 11/7/2009 10:33 PM   
MJD



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quote:

ORIGINAL: Mike Connor

The open bays will be pretty small when you get through. Any idea what it will weigh?


I think 4.0-4.2 pounds is where it will end up. With luck there should be enough static thrust for decent launches. I may make a Demon bungee rail launcher, I've been thinking about that for a while. I'm more interested in getting in the air safely than the machismo aspect of hand launching.

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RE: Screamin Demon .65 build thread - 11/7/2009 10:38 PM   
MJD



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ORIGINAL: smoknrv4

Really like that hinging method, I suppose a table saw is the only way to do it properly to get even straight cuts.



Yeah you need saw with a rip fence to make straight stuff, or slice them by hand. Now.. yes I have been making continuous hinges for my models lately using a Dremel router table to slot the TE/LE. But this stuff was commercially made, and I bought it I would guess in the mid '80's. It is conveniently 3/8" thick like the Demon TE. I decided I would finally use it on this, though I had the Dynajet version in mind for it before. The method I used on #2, where I sawed continuous hinge slots in the stock Demon elevon and TE and inserted continuous hinge fabric, worked great too. I can make a set for you, it's easy. I am wondering about a way of incorporating it practically in the Demon MkII..

MJD

< Message edited by MJD -- 11/8/2009 7:08 AM >

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RE: Screamin Demon .65 build thread - 11/9/2009 12:09 AM   
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Status: offline 		There are a few type of hinging methods. Which produces the less drag?

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RE: Screamin Demon .65 build thread - 11/9/2009 3:09 AM   
MJD



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Status: offline 		I imagine the top hinge or bottom hinge with the profiled wiper at the opposite side to keep the gap closed up and the upper and lower surfaces kind of intact, or designs like that, are the best. But I think any sealed hingeline is an improvement over not sealed. And certainly in terms of integrity and flutter resistance these work okay for me.

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RE: Screamin Demon .65 build thread - 11/9/2009 3:46 AM   
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Status: offline 		Kevlar on top for the hinge and a wiper on the bottom seems like it would be worth a try?
Getting a flush fit on the wiper could be done by inbedding a peel ply the same thickness as the wiper in the lay up.


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RE: Screamin Demon .65 build thread - 11/9/2009 7:11 PM   
MJD



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Status: offline 		I had a piece of really nice 1/8" C grain I've been saving for some reason, and decided to use it for these fins. The fins are two pieces with grain parallel to the LE and TE. LE and tip capped with 1/8" sq hardwood, TE is slotted as shown and inset with .007" CF. I was curious how much weight was shed when sanding and airfoiling. Once these are glassed to the airframe they will be strong, light, and rigid.

I did a progress weigh-in. All radio gear, a Bic lighter subbing for the IMC, 2 100g weights to act as covering, and a too big spinner for ballast. 3.9 pounds. So I bet it is 4.0 - 4.25 when done, but with luck a hair lighter. Should work, though I won't be putting around doing harriers.

MJD

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RE: Screamin Demon .65 build thread - 11/9/2009 7:34 PM   
Mike Connor



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quote:

ORIGINAL: MJD

I had a piece of really nice 1/8'' C grain I've been saving for some reason, and decided to use it for these fins. The fins are two pieces with grain parallel to the LE and TE. LE and tip capped with 1/8'' sq hardwood, ...

Normally you would want vertical grain that would become rigid only after gluing to the airframe. Does the C grain give you the best of both worlds? My last fins extended well past the trailing edge and needed to be stiff on all planes. I laminated two medium weight sheets of 1/16" balsa with one vertical and one horizontal grain. The results were excellent and I can carry the plane around by the fin tip.

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RE: Screamin Demon .65 build thread - 11/9/2009 8:34 PM   
MJD



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Status: offline 		Nah - I wanted C grain for chordwise stiffness and straightness, and it has better torsional stiffness too. The spanwise strength will come from the composite skin.

Demon #1 is done the same way and I've cartwheeled it once when it snagged something on slide-out and I watched it bounce off a tip fin, and dumped it in from 6 feet on a botched approach. No damage. Yet.. Actually, in my hands, the fact that it has almost no hangar rash alone is a pretty good litmus test. I think they land harder in the back of the truck than they do on the ground after a flight.

Your method sounds fine too.

MJD





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RE: Screamin Demon .65 build thread - 11/9/2009 9:15 PM   
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RE: Screamin Demon .65 build thread - 11/10/2009 2:15 AM   
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Status: offline 		What prop do you plan on using? I have a Rossi .67 that I am about to mount on a Sundowner. I have a 10-9 and 10-10 I want to try. Am I close for speed?

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RE: Screamin Demon .65 build thread - 11/10/2009 3:07 AM   
MJD



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Status: offline 		Those are excellent choices. 9-10 is a good choice if your engine likes spinning in the DF engine range, is it a DF engine?

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RE: Screamin Demon .65 build thread - 11/10/2009 4:16 AM   
vertical grimmace



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Status: offline 		It is a longer stroke .65 I think designed for pattern. I have the quarter wave/ magic muffler they come with. Not sure what an Ultrthrust or full pipe would do for it. It really likes an 11-8. That is when I noticed it come alive. I have had it on a .60 size Kaos. I am sure the 10" props will spin very well. this engine has lots of power. I have just never propped it for speed. I am going to begin my assembly tonight, so after I get my engine mounted I can get some tach numbers.

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RE: Screamin Demon .65 build thread - 11/10/2009 4:44 AM   
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Status: offline 		I'm just curious how an OPS 65 powered SD would fair next to a .46VX DF powered SD, any advantages or disadvantages?

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RE: Screamin Demon .65 build thread - 11/10/2009 6:17 AM   
Mike Connor



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RE: Screamin Demon .65 build thread - 11/10/2009 6:28 AM   
MJD



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ORIGINAL: vertical grimmace

It is a longer stroke .65 I think designed for pattern. I have the quarter wave/ magic muffler they come with. Not sure what an Ultrthrust or full pipe would do for it. It really likes an 11-8. That is when I noticed it come alive. I have had it on a .60 size Kaos. I am sure the 10'' props will spin very well. this engine has lots of power. I have just never propped it for speed. I am going to begin my assembly tonight, so after I get my engine mounted I can get some tach numbers.


Okay then, the 9-10 type of prop is not really suitable. Anything from 10-8 to 10-10 depending on pipe setup could be a riot in the right aircraft. In a clean .40 size pattern airframe on a 10-9 or 10-10 with some grunt behind it, you'd have a nice fast ship indeed. At some point I mean to set up one of my Super .60's (OPS pattern engine) on the test stand and run some of the higher pitch 10" props to see what gioes on there.

MJD





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RE: Screamin Demon .65 build thread - 11/10/2009 7:30 AM   
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Status: offline 		My stock pipe/muffler will not fit well in the Sundowner, so I need to look at the ultrathrust I think.

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RE: Screamin Demon .65 build thread - 11/10/2009 10:02 AM   
MJD



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Status: offline 		Do you know where the hp peak is on that engine?

Here is the sum of progress today:

- fins on, glassed, sanded
- center TE section glassed to TE
- Rx bay
- engine mount bonding complete
- located tank, added bulkhead at rear of tank compartment. 11 ounce Hangar 9 tank centered on CG.

Ony need to finish details around engine compartment in morning, then I trek out to pick up some more Stis covering, but one grade lighter than I used last time - Demon #2 used 3.7 oz certified fabric for ligth planes, I will go down to 3.2 oz ultralight fabric. 1/2 ounce saving on fabric alone plus the adhesive and finish in that extra thickness multiply that savings.

getting there, getting there..

MJD

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