No.. could it be..?
04-27-2015, 11:24 AM
#326
Just had an idea.
The AMA could market little, flat, custom engraved "grave markers" to set in the ground after you really stuff one good. The markers / plaques would be a permanent reminder of our planes that made the ultimate sacrifice for our entertainment.
The AMA could market little, flat, custom engraved "grave markers" to set in the ground after you really stuff one good. The markers / plaques would be a permanent reminder of our planes that made the ultimate sacrifice for our entertainment.
05-07-2015, 05:28 PM
#333
I just finished covering an electric flying wing I built for a friend, so now I'm back on the Demon. I just got the servo rails and top sheeting on. I think I'm ready for the glass cloth and epoxy. Is 2oz. cloth OK? I have a bunch of it. I'll make a hatch to cover the radio compartment between the servos. At least the pipe will keep the mess well aft of the important bits. I filled the T/E sheeting with balsa and reinforced the area ahead of it, then sheathed it with 1/64 ply. This will form a handle for launching. I recall CP suggesting this in another thread and it sounded like a good idea.
05-07-2015, 07:05 PM
#334
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I think for the most part the only place anyone used glass is for the belly pan to reinforce that area for landings. If your going to go to the trouble of a glass hatch for the radio, you may want to incorporate fairing for the servos as well. One guy did all of that with carbon cloth, as well as molded carbon fins to boot. Basically it is a matter of how far do you want to go for real speed, keep in mind this is what DARock calls the "black arts". Looking for sped for minimal power I went as far as having all my linkages for my control surfaces done internally as well as blending everything I could to keep it squeaky clean using Kelly's SR71 as the standard for clean.
05-07-2015, 07:20 PM
#335
This first Demon will be simply a sport airplane since I'm using a .32SX rather than a more serious powerplant. I'm not worried about fairings on this one as my design speed is somewhat lower than the Blackbird's Mach 3.2. Then again, at Mach 3.2, I'd never have to worry about wrinkles in the covering... On my second, Nelson powered Demon, I'll bury the servos and do a general cleanup, though I'm not crazy about the idea of building a cowling. Besides, my Nelson is side-exhaust, so a cowling is of limited usefulness anyway.
05-07-2015, 08:13 PM
#336
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That's cool but keep in mind where the drag is the square of speed any little bit of drag you remove is like adding some more hp to it(as long as you can keep the weight down). 
Side exhaust Nelson no problem...
Sidewinder mount like CP did with his "BOH" will at least reduce the frontal area by the square area of the cylinder, run your exhaust as a top or bottom pipe.
Want to go full out enclose the pipe within the cooling duct that also take the cooling air from the engine and dumps it out the back.
Oh, as far as wrinkles in the covering, that is why mine is sheathed. With the large spaces between the bays if you really get it moving the covering is going to distort the airfoil shape and Mike really went to great pains to get one that would be better suited for high Reynolds #s. I added 3 spars with shear webs just to be sure the shape stayed true, and still managed to keep the AUW sans battery at 39 oz. If I ever get it into the air it should at least be interesting...
Side exhaust Nelson no problem...
Sidewinder mount like CP did with his "BOH" will at least reduce the frontal area by the square area of the cylinder, run your exhaust as a top or bottom pipe.
Want to go full out enclose the pipe within the cooling duct that also take the cooling air from the engine and dumps it out the back.
Oh, as far as wrinkles in the covering, that is why mine is sheathed. With the large spaces between the bays if you really get it moving the covering is going to distort the airfoil shape and Mike really went to great pains to get one that would be better suited for high Reynolds #s. I added 3 spars with shear webs just to be sure the shape stayed true, and still managed to keep the AUW sans battery at 39 oz. If I ever get it into the air it should at least be interesting...
Last edited by iron eagel; 05-07-2015 at 08:16 PM.
05-07-2015, 08:44 PM
#337
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Correction.
39 oz was with a 3 cell battery without it come in at 32.5 oz dry 39 oz wet. With the four cell it should be right about 47 oz that should put it in the 1300 watt range. Like I said it should at least be interesting, the prop pitch speed with the four cell is supposed to be something like 257 mph (I am hopping for something like 70-80% of that if I am lucky) but I'm not sure if the 5.5X6.25 prop will be able to pull that much wing.
39 oz was with a 3 cell battery without it come in at 32.5 oz dry 39 oz wet. With the four cell it should be right about 47 oz that should put it in the 1300 watt range. Like I said it should at least be interesting, the prop pitch speed with the four cell is supposed to be something like 257 mph (I am hopping for something like 70-80% of that if I am lucky) but I'm not sure if the 5.5X6.25 prop will be able to pull that much wing.
05-07-2015, 10:04 PM
#338
The wrinkle comment was a joke. At Mach 3.2 the skin temperature is considerably higher than the melting point of the covering. Get that electric setup up to about 3000+ watts and your speed numbers become a lot more possible. Pitch speed is great, but without adequate disc area, you'll make a lot more noise than speed. 1300 watts in a 1/2A-sized airframe would be truly rapid, but I think a Demon is too large for that setup. 1300 watts isn't even 2hp at the prop. CombatPigg's 200mph Nelson was over 4hp.
05-08-2015, 04:17 AM
#339
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2 oz is fine. When I do tip fins I cut a panel of glass for each side of the fin that wraps around the tip and up to the cap strip. The belly pan is "highly recommended".. for durability and strength. Doesn't hurt to do the LE, about a 1.5" strip folded over the LE toughens things up.
I built one with a 4" wide glassed section at the center of the TE, this makes a good hand hold.
The LE shear webs will become part of the standard build - ever since I did the first one I realized it was silly not to.
If nothing else I like to fair in the bottom of the engine compartment. Post #75 here sort of shows how I've done it with cardboard tube and ply. A layer of light glass over top and tough as nails.
http://www.rcuniverse.com/forum/extr...ml#post9258267
I built one with a 4" wide glassed section at the center of the TE, this makes a good hand hold.
The LE shear webs will become part of the standard build - ever since I did the first one I realized it was silly not to.
If nothing else I like to fair in the bottom of the engine compartment. Post #75 here sort of shows how I've done it with cardboard tube and ply. A layer of light glass over top and tough as nails.
http://www.rcuniverse.com/forum/extr...ml#post9258267
05-08-2015, 04:19 AM
#340
05-08-2015, 10:50 AM
#341
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I realized the wrinkle comment was a joke but it did point out an issue as far as operation of a Demon at any real speed. The large bays between the ribs won't hold covering to shape when it really get moving and will be an issue. Yes the disk size is an issue I know that and it was driven home with my stingray similar setup for power, it has a lot more wing but less frontal area because of the 3/8 thick wing but a 43 inch span just is too much for anything smaller than a 6 inch disc. The best I ever got out of it was 175 on a 6 inch but with a 5.5 it sounded mean as hell like an old Pico engine I had as a matter of fact.
With my Demon it may have limited power but I did as much as I could to clean it up. The wingtips are tapered as thin as I dared to go and the winglets have about half the frontal area of the stock version the center section is fully blended to the wing as well as the center section being an airfoil shape rather than the straight line of the original. Subtract the frontal area of the engine and cylinder and no external linkages it should be fairly quick if not a record breaker. With the pipe and cowl on CP Nelson powered beast and he had to have twice the frontal area of mine, but he had three times the power. I still have to get it into the air and see what happens, hopefully that will be soon. One interesting thing since I built it has happened, Just recently a new motor came onto the market that is a direct substitute for the 28 mm diameter motor I used that is rated for something like 2KW I know with my cooling system I can push it to about 3 KW and it will survive but I will have to change both the motor and ESC to do it and that isn't possible at the moment but if I get any half decent results from the flights I may just save up to do the swap out of the current power system.
Oh by the way the 1300w figure was what should be at the prop with something like 1600w to the motor.
(edit to add) I don't expect long life out of the motor at this input as that's about 175% of it rated power handling.
The Demon is really a great design! It is one of the few Deltas (that has been proven) can actually pass the 200 mph mark. I think it can be made to go even faster if somebody wanted to go for it (Molded skins in billeted molds type of things). Since MJD started this thread about the return of the Demons I though it would be a good place to talk about design enhancements.
One of the days when I figure out how to use cad I got to send him drawings for the electric version like I had promised Mike Conner when I got the kit from him. My electric version should have very minimal "cooling drag", at least that's what Herk thought. There are many ways of making the Demon faster the sidewinder engine mounting, buried control linkage being some of them. A FIRE sidewinder with the pipe in the center section would be cool, but the carbon would have to be moved from the center of the airfoil to the outsides so it bridged the center section.
While a lot of people call it a delta it is really a highly swept flying wing (those wingtips aren't pointy) a hybrid if you will.
With my Demon it may have limited power but I did as much as I could to clean it up. The wingtips are tapered as thin as I dared to go and the winglets have about half the frontal area of the stock version the center section is fully blended to the wing as well as the center section being an airfoil shape rather than the straight line of the original. Subtract the frontal area of the engine and cylinder and no external linkages it should be fairly quick if not a record breaker. With the pipe and cowl on CP Nelson powered beast and he had to have twice the frontal area of mine, but he had three times the power. I still have to get it into the air and see what happens, hopefully that will be soon. One interesting thing since I built it has happened, Just recently a new motor came onto the market that is a direct substitute for the 28 mm diameter motor I used that is rated for something like 2KW I know with my cooling system I can push it to about 3 KW and it will survive but I will have to change both the motor and ESC to do it and that isn't possible at the moment but if I get any half decent results from the flights I may just save up to do the swap out of the current power system.
Oh by the way the 1300w figure was what should be at the prop with something like 1600w to the motor.
(edit to add) I don't expect long life out of the motor at this input as that's about 175% of it rated power handling.
The Demon is really a great design! It is one of the few Deltas (that has been proven) can actually pass the 200 mph mark. I think it can be made to go even faster if somebody wanted to go for it (Molded skins in billeted molds type of things). Since MJD started this thread about the return of the Demons I though it would be a good place to talk about design enhancements.
One of the days when I figure out how to use cad I got to send him drawings for the electric version like I had promised Mike Conner when I got the kit from him. My electric version should have very minimal "cooling drag", at least that's what Herk thought. There are many ways of making the Demon faster the sidewinder engine mounting, buried control linkage being some of them. A FIRE sidewinder with the pipe in the center section would be cool, but the carbon would have to be moved from the center of the airfoil to the outsides so it bridged the center section.
While a lot of people call it a delta it is really a highly swept flying wing (those wingtips aren't pointy) a hybrid if you will.
Last edited by iron eagel; 05-08-2015 at 01:34 PM.
05-08-2015, 07:19 PM
#342
I think I'm ready to start covering it. The radio hatch is 1/16 ply. The tip fins are not the shape shown on the plans, just one that looked good to me. Similar, though. I used Robart 1/8" hinges. I've had good luck with them in the past. I'm using HS225 servos for the elevons and an HS81 for the throttle. I'll use a Futaba 7008SB receiver so that I can use the GPS telemetry module. I still need to make a mount for the RPM sensor. I've got some little 700MAH 6.6V LiFe batteries I bought for 1/2A's. That should do fine. I put in a hard-point for a Dave Brown tuned pipe mount. The fairing under the engine is shaped balsa. I'll put a nylon wingtip skid under the fairing and each wingtip in case I put it down on the asphalt instead of the grass over-runs. The pushrods will be 4-40 ends with carbon tube rods. 
This thing should be ready to fly in a few days.
05-11-2015, 11:36 AM
#344
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One of these days...Picco .40 DF engine in it.
I've got a Picco .80 DF that I'd like to put in a scaled-up version of the SD.
MJD, did you ever get your .65 powered Demon in the air?
05-11-2015, 12:55 PM
#345
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I rebuilt the engine with a new .67 piston/liner, which will freshen it up and take advantage of the increased top end from the 7-port .67 setup.
The airplane is not the easiest to fly, and I've flown some cranky airplanes. The landings are a bit shuttle-like. Hand launching is fun too, those props have diddly static thrust, barely 1:1 and it wallows for a bit until it decides I am allowed to control it.
High pucker factor but it moves. There is a crappy iPhone video on YT, you can see a couple of quick passes out there somewhere if you squint:1:12, 2:18
https://www.youtube.com/watch?v=XG4lgIXIOz0
05-11-2015, 02:02 PM
#347
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Big contrasting stripes out towards tips (neon green?). Make fins stand out in contrast to top colors. Wear glasses if you need 'em!
I like dark on the bottom, and especially with a big white or bright arrow pointing forward.
I like dark on the bottom, and especially with a big white or bright arrow pointing forward.
05-12-2015, 11:32 AM
#349
Thanks for the pics, Mike. I'll put some stripes on the upper side. My tip fins are red. I'm getting all the bits installed now. The weather is supposed to clear up late in the week, so a maiden by this weekend is probable. I can't promise any video, but I'll try. I will have stills though. Looks like it will come in at just over 2 1/2 lbs. I'll make the first flight with a 9-6 then go to the 8-8 APC. I have a fistful of them. Due to CG considerations, the first flight may be sans spinner. The 2" alum. one I have may be too heavy. If I had a heavier battery, it probably wouldn't be an issue, but I'm trying to keep the weight down to a minimum to keep it as friendly as possible, especially the launch. I would rather fly than pucker.
05-12-2015, 01:21 PM
#350
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I know the feeling regards launch pucker, I'm less tolerant of it these days. The 9-6 should be a good test flight prop. I have some of those Zippy 700mAh LIFe's too, for the same reason.