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Old Jun 15, 2008, 01:12 PM
115 inches of 'hog
ScaleBrad's Avatar
United States, FL, Orlando
Joined Aug 2004
2,700 Posts
Quote:
Originally Posted by Erik v. Schaik
Use depron instead of lite ply if the former is not stressed and only needed for keeping the glass parts in shape. with this many formers the weight really adds up with lite ply.

grtz, Erik
Thanks Erik,

These formers are what the nacelles attach too, so no depron here

But I have considered using blue/pink foam for some of the bulkheads, however, from what I can tell of the plans there aren't too many bulkheads, and they all seem to be load bearing so far.
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Old Jun 15, 2008, 06:55 PM
115 inches of 'hog
ScaleBrad's Avatar
United States, FL, Orlando
Joined Aug 2004
2,700 Posts
Dog-ears are lightened and installed, fit to fuse.

Now for the hard part- alignment and gluing.
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Old Jun 17, 2008, 07:27 PM
No more Screamer
57_KID's Avatar
USA, MN, Eagle Lake
Joined Jan 2004
677 Posts
Brad
since you are going electric I have only two words for you "Little Screamer"
good luck on the project. This will be one thread to watch. very cool
Steve
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Old Jun 17, 2008, 09:48 PM
hole digger
hole digger's Avatar
USA, CA, Los Angeles
Joined Aug 2002
3,281 Posts
Signing on I have to see this. Boy you have some ***** taking on a project like this. My compliments and best wishes on your build. Just one question how much have you allotted for the truck to transport the plane when finished?

Pete
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Old Jun 17, 2008, 10:37 PM
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lavochkin's Avatar
Mokena,Illinois -United States
Joined Oct 2006
5,826 Posts
Littlescreamers????? Their motors are good but they dont make a motor this big!!! These are 5+ inch fans not 2.5-3" fans. You might be able to get it to roll...maybe!! LOL!! This thing is as big as a car!!!!
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Old Jun 17, 2008, 10:48 PM
115 inches of 'hog
ScaleBrad's Avatar
United States, FL, Orlando
Joined Aug 2004
2,700 Posts
Little Screamers And yes, this thing IS as big as my car

I have a Dodge Dakota (for sale) but the bed is too short to fit this A-10.

I also have a new Dodge Magnum. I haven't tried yet, but I think the fuse will fit inside with the nose of the plane going between the front seats over the center console. The wing (one piece) can be transported on the roof racks, inside a custom built cargo carrier (just an idea) If not.....I'll pick up a cheap minivan (uggh!!)

A trailer is not a good option because it would have to be at least 10 feet long.

So... I'll be figuring the logistics out later

I've been making progress on the nacelles.

Getting them aligned and glued on the fuse was quite a task, there are a lot of angles to deal with, and the fairings themselves are another obstacle. I glued one half in place, let it dry overnight, then glued the other side to match it. Trying to do both at once was not a good idea ( I tried) I ended up using small stainless (they don't break off) self tapping screws in some places to hold the fairing flanges flat against the fuse while the glue dried. Also used a heat gun before assembling the fairings to bend the flanges for a tighter fit. The screw holes will be filled,sanded, and smoothed along with the rest of the plane at a later date.

I cut the nacelles off behind the front curve, which worked out perfect as this area has a double layer of glass- helping keep everything in shape when removed. The Byron fan units will be inserted from the front then the "cowls" will be screwed back on. This will allow easy maintenance if needed. The original design calls for "hatches" to be cut on the top or sides of the nacelles, but that doesn't help me with the Byron fans, and it also weakens the nacelles. Right now everything is super-strong and tight, can't twist or move anything.

I have started on the inlet and outlet ducting. Hope to have that finished tomorrow. Using 1/64th ply for ducting, both in/out. Going to keep the same diameter as the fan housing for maximum thrust.

Lightening holes were drilled with a Unibit
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Last edited by ScaleBrad; Jun 17, 2008 at 11:15 PM.
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Old Jun 18, 2008, 12:06 AM
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gbruce's Avatar
Canada, AB, Airdrie
Joined Oct 2001
2,324 Posts
Nice Stuff Brad.
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Old Jun 18, 2008, 01:10 AM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
22,714 Posts
brad, i understand you want the most thrust you can get, but i think keeping it the tail pipes the same size of the fans is a bad idea..at best, youd want about 95-100% fsa tops...that will still be smaller than the size of the shroud...the bryon guru's can tell you just how big that is, but keeping it the same size will reduce your thrust and e-flux velocity. also, you might want some upthrust in those tail pipes, just like the real one.
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Old Jun 18, 2008, 01:11 AM
A-4 nut!!
skyhawk's Avatar
Vancouver B.C.
Joined Apr 2002
4,664 Posts
Brad,
I would skip the inlet ducting - the Byron doesn't really need it and the exhaust should be tapered some as all byron jets did that, but even if you keep it the same - just use rolled mylar or plastic film. That's what Bryon did and they hold up fine.

After all - you are trying to save weight right?
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Old Jun 18, 2008, 08:18 AM
115 inches of 'hog
ScaleBrad's Avatar
United States, FL, Orlando
Joined Aug 2004
2,700 Posts
Thanks for all the advice. I was thinking about all the ducting "math" last night when I went to bed and figured I'd do some searching here for the right setup.

So- as far as INLET ducting, that is mostly a cosmetic thing. So I really want to do that.

I will taper the exhaust per your advice to 98% FSA, which I'll have to figure out... OK time to do some reading

I was looking at the "upthrust" angle of the exhaust on the full scale. I know the plans show the ducted fans exiting straight out, and I'm not sure about how the turbine versions of this plane are set up, they may use stainless exhaust ducts with upthrust if I remember correctly. The good news is by making the exhaust tube smaller at the end is that will allow me to have an almost scale exhaust outlet.

I'll see if I can find some mylar sheets around here locally.

Any more input is appreciated.

Maybe someone else with a Byron jet can chime in here, Bob ?
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Last edited by ScaleBrad; Jun 18, 2008 at 08:26 AM.
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Old Jun 18, 2008, 09:53 AM
Dean
A10FLYR's Avatar
USA, CO, Littleton
Joined Apr 2005
3,898 Posts
The first one had the ductwork straight out the back hitting the horizontal stab. Second one I added the "upthrust" to the ductwork. On the turbine install I put the turbines on the rear former at 0. I honestly did not see any difference that I can recall.

I would use the inlet ducting to the fan.
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Old Jun 18, 2008, 10:05 AM
115 inches of 'hog
ScaleBrad's Avatar
United States, FL, Orlando
Joined Aug 2004
2,700 Posts
I think I'll just leave the exhaust inline to keep the build simple. The horizontal stab on this plane, the full scale as well as this model have negative incidence, possibly to compensate for ???

Anyways, without getting into a physics debate I'll do the exhaust ducts straight, although I will cut the exit tips at an angle to match the nacelles just like the full scale..

Found some interesting (sometimes boring too) reading on Byron fans, including the original patent ..


http://www.rcgroups.com/forums/showthread.php?t=297676

http://www.freepatentsonline.com/4307857.html

http://findarticles.com/p/articles/m..._n8898721/pg_2

And also a good basic guide to ducted fans including exhaust outlet diameters and calculating FSA here:

http://www.jethangar.com/Ducted%20Fans/df.html
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Old Jun 18, 2008, 10:13 AM
No more Screamer
57_KID's Avatar
USA, MN, Eagle Lake
Joined Jan 2004
677 Posts
Brad,lavochkin
what no sence of humor ,, If you dont think Little Screamers would not work just ask Rvinvent, Scott or team scream,,, that will be the end of the screamers references .....
Brad
Will the wing be one piece or 2 plug in panels ?
Also on my Byron F-16 the mylar duct work on the fan made no differenct at all as far thrust ( at least what could be detected while flying it ) I went through 2 or three thrust tubes then gave up and just let it go straight out the fuse,,, while never actually testing the thrust because it was what it was . just my .02

Steve
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Old Jun 18, 2008, 11:02 AM
EDF all the way!
bruff's Avatar
Gilbert, Az
Joined Jun 1999
8,018 Posts
Measured my exhaust diameter on my Byron Mig 15 it is 4.5" dia.
Bob
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Old Jun 18, 2008, 12:08 PM
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Ed Waldrep's Avatar
Las Vegas, NV
Joined Dec 1996
7,934 Posts
Not using exhaust ducting in the byron F-16 is insane. Air would expand behind the fan and slow down and probably become quite turbulent. The air might speed up again as it goes out but it will have lost some of it's energy. I've personally seen a 90mm F-16 shoot it's mylar tailpipe out the back of the jet and after that the thing wouldn't maintain altitude even at full throttle. If not using the tailpipe didn't make any apparent difference in the performance, that's probably because the byron F-16 is huge and with no inlet ducting there is some drag from the air going around bulkheads and landing gear and such and any improvement in exhaust velocity by using an exhaust tube is more than countered by all that drag.

Using inlet ducting in the nacelle of this A-10 will make for a smoother, less turbulent flow with less drag. It'd probably fly fine without it, but be slower than it could be.

Sorry to get off topic.

Brad, Wade Joos's A-10 has a bulkhead in the back of the nacelle with the center hole for the exhaust set off center. It sits against another bulkhead and is held in place with screws. If the screws are removed, the off center hole bulkhead can be rotated and with the hole being off center and supporting the exhaust ducting, the position of the hole about the vertical axis is changed and thus you can add upthrust or downthrust. I don't recall where Ted Goodwin set the exhausts on his Wade Joos A-10 but you might want to ask him to see what angle he used. I know on my scratchbuilt A-10 I set the nacelles at 0 degrees and the high placement made for a downforce on the nose.
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