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Old Feb 20, 2006, 01:58 PM
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New Bern, NC
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F-117 Nighthawk Park Jet

Hi all... this has been under development for about 3 weeks now under very tight security and secrecy. I've hinted to a few people that I was working on something, but didn't want to show it off until it started to come together.
It kinda seemed fitting to keep it secret

It is now ready to show the world and ***might*** be ready for a maiden flight by next weekend.

I decided to go with ailerons and split elevators at the rear as opposed to elevons. Hopefully this will work.
For the elevators, I've got a movement mechanism pretty much thought out in my head that should move both simultaneously at the same rate of travel.

The ailerons will be tricky to actuate the way I cut them. I may end up committing a scale no-no by placing the servos out on the wing. Not that the plane itself is to scale... I'm going flat plate on the wings and not doing any of the faceting on the bottom, and the vertical tails are oversized by about 10% in hopes that they will add more stability.
The wings will have some washout induced by adding thin strips of FFF to the lower LE and upper TE and tapering both inwards. Not sure if that will work either...just an idea I had since I haven't got the tools or experience to build a jig to shape the washout into the wing.
I'm also going to have some down thrust added into the motor mount in hope this will aid stability as well. Some of these tricks I'm pulling from the experience of the EDF builders of F-117's.

Lastly, the fuselage is a one piece affair, and will be held to the wing by neodymium magnets...probably quite a few of them. There isn't much in the way of fuselage formers...I'll probably use some gorilla glue smeared about inside to toughen/harden up the fuse. It seems to hold up well with no formers so far.

I haven't gone as far as figuring out wing area, MAC, CG and all that stuff. I'm a computer hardware guru, not a Boeing engineer (no offense Steve)

I'll figure the CG the old fashioned way by chucking it.

Length is 39 1/4 inches and WS is 29 1/4 inches.

I'm pretty sure just by eyeballing it and knowing what the weight is that it will have more than enough wing surface to be a floater. Current weight with no electronics is +/- 7.5 oz.

Ok, thats about all the info I have at the moment...more to come and we'll see in a week if it actually flies weather and build progress permitting.

Paul

[EDIT] 5-5-06 Cockpit window trim panels pdf file added.
[EDIT] 5-7-06 Decal sheet added.
[EDIT] 5-14-06 Edited "complete" decal sheet added.
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Old Feb 20, 2006, 02:26 PM
Use the Force!
LBMiller5's Avatar
San Marcos, CA
Joined Jan 2005
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Way Cool!

I have always liked the F-117 Stealth, it looks like you have created a nice rendition of the plane here. I will be watching for a flight report.

Lucien
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Old Feb 20, 2006, 02:28 PM
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New Bern, NC
Joined Dec 2003
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I forgot to put the hardware I'll be using in the first post. Lack of funds is forcing me to cannibalize my F-20 electronics, so I'll be using an EFlite Park 400-4100, B Gears, and 9x6 APC ...CC Phx 25, Hitec Electron 6, 2 GWS Naro's for the ailerons, and Hitec HS-55 for the elevators. For the battery, I'll either use Polyquest 3s 2200's or if it doesn't need nose weight I'll use a 3s TP 1320 ProLite. I prefer the TP pack but the motor will be way out in back to get the prop to clear the tails so I may need all the weight I can get up front.

I could cheat the tails to go more vertical but I don't want to deviate too much from scale if I can help it.

Paul
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Old Feb 20, 2006, 02:30 PM
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New Bern, NC
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Thanks Lucien. For myself, I've never been a real big fan of the F-117 but for some reason the bug bit me a few weeks ago and now I can't keep myself from looking at whats on my table and appreciating the beauty of the design. I've had to look at hundreds of pics to get the scale of it reasonably close, and I have a new found appreciation for it's aesthetics.

Paul
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Old Feb 20, 2006, 07:49 PM
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Chapel Hill, TN USA
Joined Apr 2001
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Holy cow Paul! Why didn't you pick something difficult? The F-14 to this is like 3rd grade math to Calculus! Good luck. We'll be watching.

J
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Old Feb 20, 2006, 08:36 PM
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St. Peters, Mo. USA
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Wow Paul, that's one heck of a secret to keep Looks good!
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Old Feb 20, 2006, 08:49 PM
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Ann Arbor, Michigan, United States
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looks awesome paul! can't wait to see her in the air. and i can't wait see what you pull out of your sleeves next
-beanie
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Old Feb 20, 2006, 09:13 PM
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New Bern, NC
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Quote:
Originally Posted by J Morgan
Holy cow Paul! Why didn't you pick something difficult? The F-14 to this is like 3rd grade math to Calculus! Good luck. We'll be watching.

J
Heh....I actually thought it would be a piece of cake. I figured since it's all flat panels that I could just blow up a good 3-view, sharpen the hobby knife, and go to town.

I took a top view, and cut panels exactly where the lines were. Only one problem...2D didn't translate to 3D worth a darn. So I pretty much ended up cutting every part over again except the base and wing...those matched the top view perfectly

Along the way, I measured and cut measured and recut until I got nearly every piece to join perfectly together. Most pieces had to be beveled to join as well, those were basically eyeballed and cut and recut if needed. For instance, last night I spent 4 hours cutting the last five pieces and joining them to close up the rear of the plane. This morning I decided it didn't do it for me, tore the pieces off and recut them...4 pieces now instead of 5 and alot closer to scale. The rear was the hardest for lack of good pics of it, plus deciding whether to go with elevators or not. Add in figuring out a motor mounting method ...ugh. And I still have to get the butterfly tails on securely and figure a balance between scale and usefulness. Good thing I used UHU Creativ for joining all the pieces or I'd have had to live with my errors...the flexibility of the UHU joined joints has been a bonus along the way.

I just hope I'm not digging the front of it out of the dirt on the first launch

As far as easiness goes....this ones gonna get the scale flat black paint and decals...should be easy enough. I'll cut holes up front for flat plastic canopy windows and use some 1mm foam to add the sawtooth trim.

All that after I fly it though. If for some reason my interpretation of the design doesnt work out, I'll repair it enough for a static display and move on to my next project.

Glad you guys like it...any tips you want to offer are more than welcome!

Paul
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Old Feb 21, 2006, 04:00 AM
GPT
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Sydney,Australia
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You,ve done well Paul.It looks great even at this stage.
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Old Feb 21, 2006, 10:52 PM
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Seattle, WA
Joined Jun 2002
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Awwwww, man, this looks GREAT so far, Paul! Very well done. Building an F-117 park jet has been on my "must do" list for awhile, but it's a looong way away given the new baby. I'm glad to see you tackle it! Looks really scale so far.

I wish I could offer some advice on CG and control throws, but the F-117 is such a complex beast aerodynamically that I think it would be far easier to just go the chuck glider route to figure those out. But enough F-117 models have been built now that you may also be able to dig up good info just from a web search.

I'm eagerly awaiting more progress on this bird!

Steve
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Old Feb 21, 2006, 11:34 PM
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Edmonton, Canada
Joined Apr 2003
606 Posts
Holy math skills Batman! I will follow your build with great interest, Paul! Maybe once you get this one up and flying, you can use it as a Beta version and use the panels to publish a plan. I just admire your ability to fit all those jigsaw panels together to get something in 3D! But if you're like me, by the time you get it finished and flying, you'll have to reread your own posts to remember what you did... In my case it's a sign of age.

Keep up the great work, Paul!

Jack
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Old Feb 22, 2006, 12:59 AM
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Sacramento, Ca.
Joined Jul 2005
323 Posts
Looks Great Paul !!!

I think I read somewhere on the EDF forums on a 117 EDF build that the only problem with the 117 design was its tendency to flat spin when it stalled. This was due to the wings being swept back further than the fuselage causing the center of lift to move foward when High AOA, low power was induced.

I'll see if I can find it again if you want.

Good luck on the maiden. Again great looking ship even in baby blue

Ray
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Old Feb 22, 2006, 03:27 AM
bigglesjets
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Notts UK
Joined Jul 2005
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Hey Paul

That is wicked man, Woooooow! you've captured the F117's lines to a "T" Well impressed. Well done!
I had some plans somewhere for a balsa built F117, I will look them out, maybe it will give you a clue for the CG.

Looking forward to see her fly good luck

Cheers

Al
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Old Feb 22, 2006, 08:37 AM
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New Bern, NC
Joined Dec 2003
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Wow...I've got alot of replying to do! I'm glad to see the 'Hawk has been well recieved... it's encouraging me to do what it takes to tame this sucker into a respectable parkflyer.
I had to take a break from it yesterday, but I've got a few hours to work on it today. I think my focus today is going to be spackling in the gaps in the fuse and/or placing the magnets to hold the fuse onto the wing. I'd wait to do the spackling and finish work but once I put those verticals on it will be harder to work around them and I still need to coat the inside lightly with Probond / Gorilla Glue to stiffen everything up. That will be a real PITA with the tails on.

I had a stray thought yesterday while not being able to build....I'd like to take the fuse and make a mold of it so that it could be replicated in PETG... I think it would be cool to find a way to "kit" this one into an ARF if it flies well. For now it's just a stray thought...I don't have any PETG, a vaccuformer, etc etc.
It would be cool though, for ease of build and I'm guessing it would be quite a bit lighter than a built up foam fuse. Anyways...onto the replies.

@ GPT - Thanks! I'm hoping it can only get better from here!

@ Steve - I'm glad you like, and glad to hear all is well with the baby, even if she's taken your design prowess away from us for a bit It's all about priorities, isn't it
I agree on the chuck glider approach for the CG. At some point I'll have to brush up on calculating wing area / wing loading so I can share that info. It's one of those things I have to refresh on the formula every time I want to figure it out

@ AJ - Math skills? Lol...I know how to use a calculator to scale up and down luckily. As far as all the angling and jigsaw puzzle stuff goes... lets just say I'm all out of scrap sheets of FFF now and went through a couple of hobby knife blades. And I'm the type that will use a blade until it just wont cut anymore! I did save tracings of the parts that fit right, and have given some thought to putting together some plans if she flies well enough to justify the effort. If all goes well and there is enough interest out there, consider plans on the way....they should be alot easier for me to do than the F-20 plans I did last year because of all the straight lines.

@ Ray - Thanks! I've seen a couple of EDF F-117's done, and read through the thread done by the guy up in MI (forgot his EZone name) and I've tried to incorprate some of the things he learned along the way. Namely the thrust angle, wing washout, and use of a bungee launcher. I may try it without the bungee since it's pusher and I won't have the spool lag and added weight of EDF's. For the wing washout...I just hope my planned method detailed in post #1 does the trick. I did see alot about the high AOA and flat spins, so I'll be approaching that with alot of caution on the maiden. If it seems rock solid and I come out over 1:1 on thrust I will definitely have to check out how well she climbs though. It would be cool if I could get her to do flat spins that I could power out of though

@ Al - Thanks! I'm trying to keep it as scale as possible, but I'm gonna have to fudge that more than I like at the tail. But as long as she looks the part, the fun factor is more important to me!

Back to building....

Paul
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Old Feb 22, 2006, 11:15 AM
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New Bern, NC
Joined Dec 2003
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Update....

Didn't get much done today...I changed my original plans and did some other things.
Here's what I did:

Reglued the gaps in the 2 piece wing/ fuse base where it is joined...the original butt join had some gaps and was a little flimsy. Probond used both times.

Cut and laminated internal spine foam pieces. These are just (3) 1 1/4 inch strips of FFF laminated together with Probond. They'll be glued to the fuse/ wing base to give it more rigidity front to rear. Probond used for the laminate for the added rigidity. I went with this for safety reasons...I would prefer to embed a CF rod on the centerline from front to rear but God forbid I end up hitting someone / something head on and impaling a CF rod into someone / something. Hopefully the laminated strips will prevent any front to rear flex on high G manuevers.
I originally made an internal spine former from a side view but it ended up not fitting correctly and I don't think it's needed so the idea was discarded.

I also cut open the basepiece of the fuselage section for access to the inside of the fuselage pieces. I may decide to cut some formers and glue them inside depending on how well my idea of coating the fuse internally with Probond works on adding rigidity. It's actually pretty sturdy as it is. No amount of formers will mitigate damage from me crashing it or having it get stepped on or something...I just need it stiff enough to fly and stay put with the magnets.

Lastly, I started getting the ailerons and elevators trimmed to be mounted and cut excess off so they dont rub together in flight.

Thats it for now...took some pics that will be posted this evening after work.

I've got about 30 pics that were taken from the beginning that will be posted along the way...

Paul
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