YF-19 and SV-51 for radio control

[IAD]

So, several steps closer to completion:

Carbon wing spars are now installed, and the new intakes and nose/fuselage are now fully shaped, and looking very good. Tomorrow I should be able to get the wings attached, which give me my datum for the fin alignment. (One of those 'measure twenty times, glue once' steps.)

~Luke

[IAD]

Here's a couple pictures...

Note the carbon-fiber wing spars!

~Luke

[IAD]

Bit behind schedule, but the wings are now thoroughly and permanently attached to the airframe, and perfectly aligned. Moving right along.

~Luke

[IAD]

Ivanov flies again, and lives to fight another day....

http://www.rcgroups.com/forums/showpost.ph...0&postcount=488

Bit of pseudo-technical commentary...

http://www.rcgroups.com/forums/showpost.ph...4&postcount=489

Latest flight video can be seen there...

It does look nice in the air with the tip-tanks!

~Luke

[HWR MKII]

SWEET! Some pilots here thought it was a real aircraft.

[IAD]

The still photos, you mean? That's funny!

Here's a little composite I threw together... Should have posted this before, so you could have convinced them there's a secret squadron of these things...

~Luke

Edited July 21, 2006 by IAD

[chrono]

Ooo... it glides!!!

BAWAHAHAHAHAHAHAHA.....

[IAD]

HAHA!

Yes, that sequence was classic...

--SWAPZzzzzz!--

"Whoa! Fan's gone......."

"Ooh... It glides..."

-Pause-

"Uh-oh."

~Luke

[HWR MKII]

If you didnt nose it up and just light banked it you could have brought it in. when you nosed up it droppd all your airspeed.

[IAD]

The pitch up was uncommanded. Because of the nose-light condition, the canards were trimmed to operating at a negative angle of attack. My theory is the pitch up resulted from the canards stalling out. (Granted, a sort of inverted stall, but...)

This would have reduced/eliminated the downforce generated by the canards, causing the aircraft to pitch up. The resulting vertical decent is testimony to just how nose-light it was.

I probably could have recovered by applying throttle and down thrust-vector, but I was unsure whether or not the thrown fan was going to lock up the motor, so I was reluctant to bring the motors back online. (No need to burn out an ESC.)

~Luke

[IAD]

Well, I've got the nose hollowed out and mounted, the main gear access hatch cut, and the lower fins aligned and installed.

5.2 oz., right now. Target is 6.6 oz. with tissue, and I still have about 0.2 oz. of foam to remove, so basically, I'm right where I ought to be.

~Luke

[HWR MKII]

that sounds great. Please take your time.

[IAD]

I just did another flight on mine... Did my best to find the limits of the airframe.

There are a few things that need changing, I think.

Anyway, things I discovered:

It will loop, but just barely. It won't roll, or at least, I don't dare do more than a roll inverted and pull out. (The roll rate is just too slow to comfortably pull the maneuver off.) It will fly straight and level at about 60% throttle. Launches are easy, with the balance point in the correct position.

It does bleed airspeed rather quickly in a turn. Now as a jet, it's sort of expected not to pull extremely tight turns, but I think the aerodynamics are also playing a major role here. Particularly the massive elevons, which turn into spoilers, when up elevator is applied.

In a motor-out condition, the aircraft is still fairly controllable, though the asymmetric thrust-vector does make the handling somewhat odd.

Motor heating is the worst of the problems I encountered. The motors actually became hot enough after several minutes of flying to loosen the plastic fan units, and throw both fans. I'll be looking into solutions, though the most obvious is to limit full-throttle runs as much as possible. (It is in the 90's here, though, which definitely doesn't help.)

The airframe is extremely durable. I took a radio hit (I need to look into this) and ended up stalled out, and dropped ~75' vertically into a garden, with the nose down by about 10 deg.. The resulting impact caused no damage, and I logged another flight directly afterwards. Landing is simply a matter making a shallow approach, and just before the lower fins touch, applying up elevator and a bit of throttle.

Anyway, modifications I'm looking at have to do with separating the ailerons and flaps, to improve speed retention in turns, and improving roll rate. Fortunately, this won't delay building the second SV...

Video will be forthcoming... Sometime.

~Luke

Edited July 27, 2006 by IAD

[IAD]

Furthermore, recomputated current draw, etc.:

Duration: 4:16 (m:s)

Total mAH removed from pack: 885 mAH

Average current draw: 12.44 A

Predicted max. duration: 6:16 (m:s)

~Luke

[IAD]

http://www.rcgroups.com/forums/showpost.ph...4&postcount=502

A short video, showing an attempted roll, which resulted in my discovering that with the right control inputs, a 'sorta-cobra' may be possible.

Similar (at a less massive scale) to the maneuver Ivanov used after perforating the tanker in the 4th episode.

~Luke

[Razor x]

WOW!! awesome video that looked like a Cobra manuver!!!!( i think thats what its called)

DOH! just noticed you did mention "sorta cobra" HEHE

Edited July 28, 2006 by Razor x

[HWR MKII]

Looks like your getting the hang of flying this beast. I noticed you had trouble with keeping it up when the wing tank/missile pods were on. It did look good with the tanks.

[IAD]

Yes, they threw the CG off a bit [more] and seemed to add a lot of drag. They were skewed off from the centerline, though... (Small mounting mistake.)

I'll probably try a flight with the tanks again, properly mounted, after I get the fan issue ironed out.

~Luke

[IAD]

Well, the usual updates:

First, I finally got all the fins glued on the second airframe. I also installed some balsa rails in the bottom of the nacelles, to protect them from denting. (My ship has had major issues with dents forming along the relatively sharp edges on the bottom of the nacelles.) The balsa should keep everything looking crisp. I also have the balsa intake lips built into the intake boxes, which are key to good thrust. They'll also give me something to mount the intake sawtooth to.

I was going to shape and install the control run covers tonight, but after repeated tries at sanding the things to the right shape, I just couldn't get it to look right. (Mad) No matter, I'll try again in the morning. Funny how these small bits can be so much harder to shape correctly.

I've also come up with a way to save perhaps 0.25 oz. on both airframes. I'll test it on mine first. In the end, though, I may have to install another servo for pure ailerons (improving the turning aerodynamics) so actual weight savings will be more like 0.125 oz... Still, every little bit helps.

~Luke

Edited July 31, 2006 by IAD

[IAD]

Ok, got those control run covers finished. Looking very spiffy.

Sean, I'm going to get the tissue to cover the airframe today or tomorrow... Should I see if I can get it in pink, to reduce the amount of paint you'll have to throw at the thing for the base coat? (It won't be a perfectly uniform color, but closer, all the same.)

~Luke

[HWR MKII]

Actually white would be better so i dont have to get the yellow as thick on it. Im putting the yellow down first then masking off the stripes and applying the magenta. The magenta should be dark enough to cover the yellow in a thin spray.

[IAD]

I see, that makes sense. Ok, then, white it shall be.

~Luke

[HWR MKII]

Sounds good to me. Now i just need to find some fine point tech pens for panel lines and rivet dots. Seeing how iit wont fly for at least a year. The weather here has turned crap again and where i go in the states may snow in the winter. Plus after seeing the cobra video i want to get even more trainer time in. But again there is now no flytime. The winds here are high and it is beginning to rain regularly.

[IAD]

Really, it's easy to fly... REALLY!

(Yes, I know, I'm always saying "Yikes!" or "Whoa!" or "Oops!" on the videos, but that's just me. Hey, after all those exclamations, I haven't had any real airframe damage yet. That should say something. )

I would avoid the snow, unless you have a clear-coat which is very light and waterproof. (Weight is a big deal here.) If however, you have something that satisfies the aforementioned requirements, powdery snow is very good at preventing crash-damage.

~Luke

Edited July 31, 2006 by IAD

[HWR MKII]

Well seeing how RARE this airframe is it will be handled with kid gloves at all times. The only time it will be put through its paces is in the air. I have noticed RC aircraft tend to aim toward the hadrest, nastiest and most damaging surface when control is lost. For this reason i will be scouting areas really well before i fly and making sure to stay away from possibly damaging surfaces. The more bad variables that are removed means i can concentrat on the joy that will be flying this.

[IAD]

Yes, I know what you mean there... My hands still shake a bit before launching.

~Luke

[IAD]

I've started the tissue covering... I've got both nacelles done, along with most of the lifting body, forward of the nacelle tops.

I've also found a way to save ~0.1 oz... I remove the 'gunpod' piece, that goes between the legs in fighter mode, and replace it with two pieces of sheet foam. In the end, it all looks the same, but it's hollow, and thus somewhat lighter.

(On mine, I've recessed the top sheet foam piece by about 1/32", to define the gunpod/fuselage interface. Can't tell yet if I like the way it looks. Needs a bit of paint.)

~Luke

[HWR MKII]

Sounds good. I think the hasegawa model even makes that as a seperate piece. The Clip for the ammo is the upper part that goes between the legs.

[IAD]

Gotcha. I'll post photos before I mod yours, so that you can make the call, recessed or not.

I say... What is that thing loading? A 250 round clip, or something? It's huge!

~Luke

[HWR MKII]

Its got to be more than 250 rds. A f-16 or F-15 can hold 500+ rounds in a drum smaller than me. And thats 20 mm. An A-10 can hold even more but the drum is huge on it.

[IAD]

Well, I guess they didn't have enough aircraft techs on the design team, because the compendium says it has a 55mm gunpod, with a 120 rnd. magazine...

According to my quick calculations, 66 of the 55mm rounds would fit in the F-15/16 drum, taking only the the cross-sectional area into account. The magazine on the SV is about 18 ft. long.... So, you're definitely right, it should (could) have had a lot more ammo in there...

Oh well, maybe all that 55mm ammo was too heavy...

~Luke

[HWR MKII]

Well i scared the guy at the RC hobby shop. I told him about the airframe and showed him the flight control videos and the cobra video. He said that he would never try to fly something like this. He thought he couldnt handle it. Funny thing is that he is an experienced RC helo and stunt plane flyer.

[IAD]

Wow.......

That's really funny, because even on a suitable plane, I can't even fly an axial roll to save my life, and my inverted looks inebriated In short, my piloting skills are (overall) somewhat lacking.

It's all psychological, I guess... I always looked at extra control surfaces and what-not as a safe-guard against losing control at low speed*... (Not to mention improving maneuverability.) I guess to most people, they just add intimidation factor...

~Luke

*For instance, right after the cobra-pullout-thing, when the left wing started to drop a bit, I was able to thrust-vector it back to level, even though my airspeed was still very low. That's what I call neat, and a nice feature to have!

[IAD]

Slowly but surely...

So far, I've got the top of the wings and lifting body covered, nacelles in the final stages of sanding, and I've started covering the thrust-vector vanes... Going for completely uniform finishing here.

I've also added the fillet at the very front of the LEX, where it blends into the fuselage/nose. Looking super so far.

~Luke

[HWR MKII]

Sweet. BTW i found out ill be getting stratoned back at HILL AFB again and ill be back there by december. Hill is great, the base even has a dedicated clear area for flying RC acft. There is also a local civi airport that has very little traffic so they are friendly toward RC Fliers.

Anyone here from the salt lake area?