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Old Jul 05, 2013, 06:13 AM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
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Scratch build lockheed Have Blue XST

As a kid growing up I used to go into my local hobby store on a Saturday morning and sometime would come across a testers kit of the F 19 "stealth" that was reportedly flying around in the U.S.
I remember thinking that surely building a "stealth" aircraft was akin to building an invisible plane. Years later the F117 was finally revealed and I realised how badly Testors had got it. The shape of the F 117 intrigued me. I was fascinated by the flat surfaces, the result of low processing computing power from the mid 1970's. Then a couple of years later I finally heard of and saw pictures of an aircraft that preceded it.

The two initial pictures released of the first Have Blue fascinated me even more than the nighthawk, and still to this day I find it's even more extreme shape and design a source of curiosity.

I don't know if part of the fascination is down to the secrecy that still to this day surrounds it.( I believe that only 7-8 pictures publicly exist of them plus a 30 second youtube clip) Or just that it just has a uniqueness to it. I love those inward canted fins. One of the pictures since released shows the underside of the second prototype in flight. It looks like a larger aircraft that what it actually is. The platypus flaps look cool and it reminds me of the underside of one of the imperial star cruisers in the opening scene from the original Star Wars (which had only just come out a year earlier.)

I would soo love to see more pics of this aircraft released to the public. We can only hope. Surely inside the pentagon there's a vault with heaps of photos of these aircraft just gathering dust.

If you want to read the brief history of these two planes then there are sites ,however I'm now going to talk about the build I'm embarking on.

I've always wanted to build a flying have blue. There are heaps of kits available and plenty of info on the F117. Plenty of foam edf kits you can fly in a couple of hours but I've seen nothing on its diminutive predecessor.

I realise that I have chosen one of the most aerodynamically unstable aircraft possible. Clever me, however they say the same thing about the f 117 and yet i see heaps of You Tube clips of foamy nighthawks whizzing around just fine. So why not a Have Blue?

I am making a few concessions as you can see from the last pic there is a break in angle between leading edge angle and nose. Hmm. I also don't know if I will make the underside profile just like the original. I'm also thing of making the platypus flaps into elevators and making the ailerons into elevons.

Edf will be a 55 mm unit. Span is about 700 mm. 9 g servos.

Anyway I will post more as this build progresses.

Dave
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Old Jul 05, 2013, 06:51 AM
EDF Jet Jam 2015 , May 28-31
Kevin Cox's Avatar
St. Louis Intl, Missouri, United States
Joined Jan 1997
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Looks great!
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Old Jul 06, 2013, 03:35 AM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
Have Blue XST scratch build.

Thanks Kevin,

I have found this to be one of the quickest builds I've ever done. I have built the fuselage and wings to this level in about three days. I am on winter holidays at the moment (industrial arts teacher) so I have a bit of time.

As I mentioned earlier on the original aircraft the leading edge sweep continues right to the very nose. This is an extreme angle and results in a small wingspan. It changes the geometry of the wing ,especially around at the platypus flap and rear surfaces. I have reduced the sweep but have tried to keep the angles of the platypus flap and the trailing edge reasonably similar to the original.

Hopefully the aircraft will generate more lift and get off the ground a little quicker.
I have to start thinking about the ductwork. I will have an edf right in the middle and will create the channels from the front two intakes.
Questions should I make them round or can I have them boxy and square at the start and curve them by the time they get to the edf? Comments please.

The battery will go just in front of the ductwork.

Enough for now. Would love ideas, people.

Dave.
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Old Jul 07, 2013, 05:05 PM
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Ed Waldrep's Avatar
Las Vegas, NV
Joined Dec 1996
7,937 Posts
Square or trapezoidal transitioning to round will work fine. There's some losses theoretically in the corners but no big deal. You could have a bulkhead in front of the fan that you attach the ducting to and help form it into the round opening. I'd use heavy cardstock or my favorite donut box material. The inlets on my F-22s were made that way and I have two sizes flying.

The important thing is do you have enough inlet area? And also, can you move the fan back far enough to balance with the battery in the nose? I started an F-117 six years ago and was worried about getting the fan far enough back so that I could slide the battery back far enough to get the Center Of Gravity in the correct spot. I was worried that I might have to split the battery pack in two (two packs wired in parallel) and place them on either side of the fan, not an ideal solution. But I got sidetracked and never finished the build.
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Old Jul 07, 2013, 06:55 PM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
Thank ed,

I have been thinking about the battery set up and I think I'll have a few tricks up my sleeve with that one. The ducting advice is good thank you. I can enlarged the inlets slightly which I'll do. I'm working on the platypus flap at the moment and modifying it to be an elevator/vector thrust kind of set up. I don't know how effective it will be.

Keep the advice coming people's



Dave
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Old Jul 08, 2013, 03:30 AM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
I really thought I'd be getting more comments from people.

Anyway,

Another day of working at the tail end. I have spent time covering the top of the wings. Used fine silk in the centre section. (Reduce weight) and save on balsa) going through .8mm balsa sheets like there's no tomorrow. The fabric has wrinkled abit around the edges. Bugs me a bit. May pull it up and redo. Trimmed around the elevon hinge line and also made the rear surfaces. Photos show both the basic cut outs for the moveable platypus flap/ elevator.

Does anybody out there fly an F 117 with moveable surfaces ( elevators) behind the exhaust vents? If so could you advise me on their effectiveness in pitch control.

Elevons held on by black tape just for looks. Platypus flap will have a single servo pushing and pulling in centre between exhaust ducting.

Have put underside sheeting beneath Platypus flap. Looks good from underneath. However can't really sheet anymore till I put the servos in. Both for P'flaps and elevons.

Will have to start sheeting the rest of underside soon. Will have fixed gear.

Anyway, must go,

Dave.
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Old Jul 10, 2013, 03:28 AM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
Can someone PLEASE respond to my questions?

Anyway, started work installing the elevon servos this morning. Cut out a section of balsa from the rear root rib and stuck a small servo in. Straight forward really.
Made a horn out of thin aluminium sheet. Then just used two clevices on a small bit of threaded rod.

I've hooked up the two servo' s to a mixer and they work fine. I have then started work on the undercarriage. I'm using fixed undercarriage. Save weight and complication.Simply just a stiff wire with a wheel on it.

Reinforced the attachment area with hardwood and fibreglassed it down. Also given some areas a light coating of polyester resin. Have Blue 2 only had a light grey colour scheme so primer grey should do nicely. Will sand back may give another light coat or would this be too heavy?

Till next instalment, advice would be nice.

Dave.
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Old Jul 10, 2013, 05:49 AM
Learning to mod
Ireland, Dublin, Dublin City
Joined Apr 2013
137 Posts
I just had a look though your/this build log,
I think its Looking great!
Probably its just that people like to watch, not help lol.
This awesome thread need more replies!

Subscribed!
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Old Jul 10, 2013, 01:17 PM
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Janusz Jawien's Avatar
Los Angeles Van Nuys, California, United States
Joined Apr 2002
1,111 Posts
Congrads on your very nice build, Dave!
IMHO the hudge elevons will be more than efficient and the Platypus flap will only add
problems in the first maidens and adjastments. Yes, have this flap ready functional to play with after all other issues are solved. I would make sure to have some washout added or fly with elevons in little up position for maiden. I am not sure how eefective the vertical fins will be.... they look pretty smallish.... I would make them bigger and may be more vertical to start with...you can always modyfy them or just change for more scale later when all other issues are soved.
Just my two pennies....
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Old Jul 10, 2013, 07:27 PM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
Thank you Janusz,

Great feedback. Thank you for the advice on the platypus flaps. I will take that up. The rear fins are small. I'm more concerned that they will loose effectiveness because they are in the wash of the apex of the cockpit canopy. Unfortunately the original aircraft had small verticals. I probably will cant them less.

I never would have thought that I'd need washout on this aircraft. I'm very familiar with washout I build lots of gliders but I did think that on a low aspect ratio wing it would be as needed.

Thanks

dave.
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Old Jul 10, 2013, 08:59 PM
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Janusz Jawien's Avatar
Los Angeles Van Nuys, California, United States
Joined Apr 2002
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Just going through your thread and pictures again....
You have a pretty smallish fan for the size of your project. I would definitely pay attention to Ed's advice regarding the inlet area. I would cover the area on a top of the fuse between the cabin and the fan with a sorta of mesh (nylon or metal) to conceal a cheating hole and get more air to the fan.
It is nothing wrong with having "no scale"... but effective verticals to begin with... you can always replace them with scale looks after the other jings are sorted out and the model is still in one piece...:-)
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Old Jul 11, 2013, 12:59 AM
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Tucson, AZ, USA
Joined Nov 2000
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Many years ago I built a model of the F117N (pictures Flying Models Jan 2001, RC Jet International Apr/May 2001). The model had two fans fed by the rectangular ducts. I used drafting mylar glued into the intake and the round fan opening. My inlet area was FSA and the mylar formed a full straight lines transition. I did find that I needed to glass the outside of the duct to keep the fan suction from pulling the ducts in. The other interesting problem was the exhaust placement inrelationship with the fan. You probably can't place the exhaust duct on the same centerline as the fan vertically. This will give you problems as your thrust line will want to force your nose down on take off. I found that I needed to get it rolling fast, cut power, lift off, and then bring power back . In the air there is enough elevator athourity to over come the down nose thrust. Your platipus surface may come real handy for correcting the thrust angle. I believe that that surface does much of the same thing for the real F117.

I've looked at Have Blue also. It can be done. Just watch the thrust lines and yes, washout would be a good idea.
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Old Jul 11, 2013, 03:09 AM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
Thank you one and all for the fantastic feedback. Hugely appreciated.

Dave
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Old Jul 11, 2013, 06:44 AM
Wasserkuppe wannabe
D Hughes's Avatar
Central coast NSW Australia
Joined Aug 2006
108 Posts
G'day lads,

Thanks Bob for those words of wisdom. It looks like the exhaust duct will angle upwards to the outlets. I haven't even started the ductwork yet. Just got to sheeting the underside today. Still not complete.

Went down to the local fabric store today to get some more "bemsilk" I don't know if its called anything else outside Australia. I have used this fine silk like material to cover the wings of my vintage scale gliders for years. Turns out its really good over balsa joints on stealth aircraft too. Dope it up and a nice taut structure results.

I'm going to look into ways to increase air Intake area. Thanks everyone for the feedback especially on the Platypus flaps and their effectiveness. I will make them operable for initial flights as the more control surfaces the better. They may be superfluous.

Weighted her tonight. With edf unit 200 grams. Wingspan 600mm length 750mm
Some pics of progress.

I'm not after a bullet. I just want a plane that will get off the ground fly around at a good speed and be able to be landed in one piece.

Thanks

Dave
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Old Jul 11, 2013, 05:53 PM
EDF Jet Jam 2015 , May 28-31
Kevin Cox's Avatar
St. Louis Intl, Missouri, United States
Joined Jan 1997
6,899 Posts
Looks great!
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