TWIN FEVER !!!
 

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.

RE: TWIN FEVER !!!
 

I can see this will be another "RUN AND HIDE! ! ! !" screamer from the CP barn.... :D

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.

RE: TWIN FEVER !!!
 

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....

RE: TWIN FEVER !!!
 

Just don't run while holding it. You'll poke your eye out! It's sure got unique lines.

RE: TWIN FEVER !!!
 

If there ever was a plane to help RLF conquer his HLP-aphobia...:D

RE: TWIN FEVER !!!
 

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

RE: TWIN FEVER !!!
 

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?

RE: TWIN FEVER !!!
 

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.[X(]

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!:D You are in this hobby for the beer & the girls aren't you?

RE: TWIN FEVER !!!
 

Waaay cool! Looking forward to a flight report.

RE: TWIN FEVER !!!
 

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.[sm=lol.gif]

RE: TWIN FEVER !!!
 

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.

RE: TWIN FEVER !!!
 

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?

RE: TWIN FEVER !!!
 

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!

RE: TWIN FEVER !!!
 

When does the pool start on the size of the hole that leaves in the ground? ;)

RE: TWIN FEVER !!!
 

That is either just plain nasty or it's a comment on how tall the grass grows.... :D

RE: TWIN FEVER !!!
 

Looks like a fun plane to me. Neat to see a picture of one of your planes WITHOUT a hairy arm and hand in the shot. :D

Any thoughts on fuel tank setup? I've always wondered how well twins would run off a single tank - would it reduce the likelihood of one engine stopping well before the other or just cause fuel draw issues? You're a small prop fan so you could put the nacelles relatively close to the fuse to keep the fuel line length to a minimum.

EG

RE: TWIN FEVER !!!
 

Raymond --

I think you got the decimal point in the wrong place -- that should be every 1.137 days

I haven't tried WBPU, but did a few test strips with Elmer's Titebond and white glue. If the foam was not porous, the glue didn't dry out very well. The white glue cured around the edges, but remained wet in the middle -- this was with Readiboard which is extruded and has a skinned surface. The edges just sealed up and the moisture couldn't escape. If the surface area is large, then I use one of the polyurethane adhesives.

RE: TWIN FEVER !!!
 

According to my postman you should have a box of Norvels in your mail box. Let me know if they made the trek to the North West OK.

RE: TWIN FEVER !!!
 

In no particular order . . .

* Aha.

* Underhand.

* Sorry.

* Aw shucks.

* Youse-all are fine people.

RE: TWIN FEVER !!!
 

Hey Chuck,

I remembered one other design trick that may help you with the engine out issue. You probably are already putting in some engine out-thrust which helpsand I'm assuming you're going to have a v/stab on each nacelle ala SR-71. If so, put some "toe-in" in the v/stabs (leading edges closer together than the trailing edges.) This has a positive effect on assymetrical thrust as well.

Oh yeah, what's taking you so long?;)

RE: TWIN FEVER !!!
 

Now I'm wondering,
we see some talk about Blackbird traits CP should use
yet it looks like he's a'studyin the U2 in his book-learnin

RE: TWIN FEVER !!!
 

Right on with the out-thrust. Ed Moorman in RCReports said about 8-degrees, if I remember right, would give "safest" engine-out recovery. Alas, we all know CP would never sacrifice that much lost power just to be safe - Would he? Maybe just for the first test flight even?

RE: TWIN FEVER !!!
 

Wow! Look at all the arm chair quarterbacks we got here! First Larry D comes out of hibernation the other day, now Dickeybird prys himself away from his machinist dungeon long enough to talk about little nitro burning planes again? What has to be done to get Matchless to come to the party, a B-17 with .020s? With AJC, it would have to be a Spruce Goose with .049 four strokers.

First, Steve Eberharts' shipment of Norvel machinery came through unscathed. I opened it all up right in front of my wife. She just got a ticket for doing 80 in a 60, so that is how she spends her fun money, this is how I spend mine. Thanks again, Newtech!

DB, nice to hear from you on your annual visit. Thanks for the out thrust tip. I didn't use it on my bipe with the TDs. Even though it has a huge rudder [like a DH Rapide] it is a little bit of work to fly out what is left in the bladder tank with just one engine running. I figured that its' big, doggy layout was built in safety. This new plane probably won't be flyable with an early flameout if the throttle shut-off doesn't work. Did AJC have engine thrust on his Cessna? I played around with a remote thrust angle control plane last year [45 degrees either way] and you don't see the planes' line of travel affected much at cruising speed. for this plane, some angle would be a good idea until the rudders are proven. Rudders on a plane like this don't usually have much effect, so in thrust we trust

KE, we can't be saying the BB word [or SR71] too loudly, those black helicopters have started sweeping the area ever since I placed the order for 4 rolls of flat black monokote with Tower. I don't even respond to these posts any more without first donning my aluminum foil brain wave shield....I hope you guys will show the same consideration and wear your foil beanies while viewing this thread. [8D]

Andrew, you've been kind of scarce, too. You aren't growing your fingernails real long now [making it hard to type] like some of these other recluses, are you? WBPU works pretty good but it doesn't give a hard shell over foam. It sands and fills nicely, but it doesn't get hard enough to feather out FG seams, they just get fuzzy.

Erok, I'm going to use Hayes 2 oz tanks and figure on shutting the engines down before the plane starts spinning, at least in the beginning. Who knows, this thing might end up being a champion flat spinner that can do perfectly gentle verticle landings? ;)

Lil'D.....on the bright side the engines might never reach the ground?

RLF, let's make this another postal plane project.....but with a twist. The recipient of the already fueled up] plane has a camera crew show up at his house un-announced and they drag the guy down to the closest field to, "fly it or else". The pop corn and beer concession after the release of the video would be enough to retire on, alone. :D Who here should lead off?Who do we know who already has a hard enough time making it through the day on just one pair of shorts? His name is on the tip of my tongue, just a minute...VVVViiiiiccccmmm....

RE: TWIN FEVER !!!
 

Yeah, I'd pay to see that video.

Shorts per day - or did you mean per week? Shhhh, he's probably asleep by now anyway.

RE: TWIN FEVER !!!
 

OK, as you can see the fuselage was split into 2 and a sliver of plywood got Ape glued in between. Now all it needs is a slightly tougher skin to be strong enough. The contours should allow covering with just 2 pieces of cloth.