TWIN FEVER !!!  
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TWIN FEVER !!! - 2/19/2008 4:04:09 AM   
combatpigg



Posts: 9255
Joined: 11/22/2003
From: arlington, WA, USA
Status: offline 		It has been awhile since I've had a twin going. The sound is addictive. My first was several years ago, all I did was take a TD .049 powered Q-Tee and strap another TD to it that was mounted on a glider pylon. It worked great and sounded awesome. Since then I built a big biplane that was/is TD .049 x 2 powered......it flies well, but kind of tame. Now I want to try a twin with some pizzazz. I'm not sure which engines to use, the final decision will be based on weight. I have no idea what the wingloading will be, have no target weight, just want to blast through the project without turning it into a Cisteen Chapel job...but at the same time don't want to waste my time building a lead sled.
In comes the blue foam to save the day, it might be light enough and strong enough with a single layer of 3/4 oz cloth to act as a fuselage. The engine nacelles are a different story, the blue foam will be used to form a plug that I will use to laminate a glass part, then throw away the foam. So far the foam fuselage has been worked with a cross cut saw and 60 grit sanding block and it has started to take shape. While working it, I wear a respirator.

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Led Zeppelin is NOT "old fogie" music.
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RE: TWIN FEVER !!! - 2/19/2008 4:15:08 AM   
BMatthews



Posts: 8796
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		I can see this will be another "RUN AND HIDE! ! ! !" screamer from the CP barn....

For strength you're going to want to use 4 oz cloth. 3/4 will snap like a dry twig even if the nose digs in lightly on a close to soft sort of landing. If you use the old "suck up the excess resin with the roll of toilet paper" trick the nose proboscis shouldn't come out too heavy. Just fill the weave from there with a mix of thinned down lightweight wall filler and it'll be good.


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Bruce-
Proudly wasting balsa since 1965.

Free Flighters go that extra mile........

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RE: TWIN FEVER !!! - 2/19/2008 4:47:59 AM   
combatpigg



Posts: 9255
Joined: 11/22/2003
From: arlington, WA, USA
Status: offline 		Thanks for the reality check, Bruce. 3/4 oz would just either snap, crackle or pop. You sure don't want to land this thing nose heavy.
I've got the option to make a fairly tough but light skin, then dig out all the foam.....this blue foam is heavy.
After sizing up how to control this thing, it will get throttle, elevons and rudders. There will be 3 servos in each nacelle. It might be just as easy to do the nacelles with wood, and just use blue foam and glass to blend them into the surrounding area.
The more I look at it, the more it looks like .061s will do the job, but the cut-off weight for .061s is going to be 32 ozs. That doesn't sound like much weight for a plane with 2 engines, 2 tanks, 6 servos, etc. I'm using throttle servos mainly just to have an engine kill, maybe that function can be accomplished with full down elevator instead?
Time to go talk with some old C/L team race guys for shutoff ideas....

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Led Zeppelin is NOT "old fogie" music.

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RE: TWIN FEVER !!! - 2/19/2008 5:04:09 AM   
ptulmer



Posts: 4754
Joined: 4/28/2003
From: Brunswick, GA, USA
Status: offline 		Just don't run while holding it. You'll poke your eye out! It's sure got unique lines.

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RE: TWIN FEVER !!! - 2/19/2008 5:08:32 AM   
combatpigg



Posts: 9255
Joined: 11/22/2003
From: arlington, WA, USA
Status: offline 		If there ever was a plane to help RLF conquer his HLP-aphobia...

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Led Zeppelin is NOT "old fogie" music.

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RE: TWIN FEVER !!! - 2/19/2008 6:14:28 AM   
build light


 

Posts: 1313
Joined: 11/30/2005
From: Crete, NE, USA
Status: offline 		What a sweet ride this one looks to be!

The long nose looks like it will be awkward when starting the second engine but the payoff for having it will be how it looks in the air! Worth the trouble in my book.

Robert


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RE: TWIN FEVER !!! - 2/19/2008 6:24:40 AM   
combatpigg



Posts: 9255
Joined: 11/22/2003
From: arlington, WA, USA
Status: offline 		Thanks, Robert. I hope it ends up worthwhile...or at least worth fixing.
I've never ran AMEs with carbs. I might end up tapping the backplates for pressure anyway and just use the carbs like an on / off switch?

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RE: TWIN FEVER !!! - 2/19/2008 1:09:24 PM   
DICKEYBIRD



Posts: 2658
Joined: 4/8/2002
From: Collierville, TN, USA
Status: offline 		Awesome project Chuck! I love twins.

One word of advise though...don't forget to figure in all that fuselage area up front when calculating the CG and the vert. stab area. It'll end up with serious aft CG and yaw instability problems if'n you don't. The 1st flight of my little D-Estes rocket powered delta back in the 80's taught me that lesson. I somehow got it down in one piece but it was like riding a pi$$ed off rodeo bull.

As far as simultaneous engine shut-off worries go....don't sweat it, just let one engine die 1st and flat spin it down into that energy absorbing weed field you fly at. That'll REALLY impress the girls! You are in this hobby for the beer & the girls aren't you?

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RE: TWIN FEVER !!! - 2/19/2008 1:28:19 PM   
Tee Bee


 

Posts: 641
Joined: 2/22/2007
From: Angleton, TX, USA
Status: online 		Waaay cool! Looking forward to a flight report.

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RE: TWIN FEVER !!! - 2/19/2008 1:34:55 PM   
ptulmer



Posts: 4754
Joined: 4/28/2003
From: Brunswick, GA, USA
Status: offline 		CP, I think Ray's biggest problem with hand launching is the top of the grass scrubs the bottom of the plane as he runs across the field. It's awful cute to watch, though.

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RE: TWIN FEVER !!! - 2/19/2008 2:18:18 PM   
combatpigg



Posts: 9255
Joined: 11/22/2003
From: arlington, WA, USA
Status: offline 		Hi DB, nice to hear from you. I figured that the fins were going to need some figuring. There is a guy [funkworks] over in the extreme speed forum who just maidened his 95% to scale blackbird. His looks impossible to fly, but he somehow managed. I sure don't want that. If the plane can be built to vauguely resemble the original and still fly without acting like we're at the rodeo, then I'll be happy. I guess a pair of fins to offset this nose will need to be a little bit "statuesque"? As it stands, I have stretched the wing and shortened the nose by a lot to try and make this thing look half way feasible.

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RE: TWIN FEVER !!! - 2/19/2008 3:01:10 PM   
Raymond LeFlyr



Posts: 1794
Joined: 2/10/2002
From: Just a little south of Raleigh, NC, USA
Status: offline 		Hey whats-your-name, I got your "HLP-aphobia" right here (but I am cute while doing it aren't I?)

But I do have constructive advise to offer (unlike some others I might point out). I used to use that blue foam a lot for the glow combat models (harumph, I'm into e-combat now doncha ya know) and because of the mistakes of others I had to learn to toughen up my fuselages. What worked for me is just slicing them down the middle and making a sandwich with 1/32 or sometimes 1/16 ply in the middle. Cutouts for lightness and equipment didn't reduce the effectiveness. That little bit of ply would fix the flex in one direction. Then a wrap of real thin filament tape around the middle (90 degrees from the ply) would stabilize it the other way. FG is just too much fussing for me. A couple of squirts of paint and I'm in business. I hesitate to point out that having heard first hand reports of CP's need for speed coupled with the fact that he completes a new model every 11.37 days, I wouldn't worry too much about long term structural integrity anyway.

Hey, I just had a brain burp (some of my new meds are pretty cool man, woo hoo). Instead of using ply for the central element of the sandwich, I wonder if FG would accomplish the same thing only lighter? I switched to water-based-polyurethane when I do use FG but I wonder how it would cure inside a dense foam sandwich? Any thoughts? Anyone? Buehler?





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RE: TWIN FEVER !!! - 2/19/2008 3:52:56 PM   
MJD


 

Posts: 1509
Joined: 5/27/2003
From: Orangeville, ON, CANADA
Status: offline
quote:

ORIGINAL: Raymond LeFlyr

Hey, I just had a brain burp (some of my new meds are pretty cool man, woo hoo). Instead of using ply for the central element of the sandwich, I wonder if FG would accomplish the same thing only lighter? I switched to water-based-polyurethane when I do use FG but I wonder how it would cure inside a dense foam sandwich? Any thoughts? Anyone? Buehler?



As I read this I started thinking about routing slots top and bottom and the sides, i.e. the quadrants, and inlaying strips of something. But nah. I guess I would be tempted to lay a strip of something fairly axial and stiff along the quadrant lines before the outer skin. But that ply inner sure sounds good - esp. if you cut it to profile and use it as the sanding jig in that axis. Okay then, how about cruciform profile plates from thin ply (1/32"?) and four sqaures of foam bonded between those? Or..

I imagine CP's got it finished by now, what's the point?..

MJD

p.s. maybe I should go finish my Blink. But man, first I'd have to clean the bench, then.. wah!

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       Post #: 13

RE: TWIN FEVER !!! - 2/19/2008 5:42:47 PM   
lildiesel


 

Posts: 444
Joined: 11/18/2005
From: Cincinnati, OH, USA
Status: offline 		When does the pool start on the size of the hole that leaves in the ground?

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