Going for design of F-117 64 mm EDF version

[L Edge]

After completing my SR-71 and A-10 Warthog, the last is the F-117 that I am going to try to do not only with a EDF 64, but enlarge it to handle a 70mm system if it has a good flight environment. Looking at a number of RC designs, I have decided to incorporate a mixture and scale it to what I would like to try.

So with that said, being old school, it is a cut and try approach so at present, there are no plans. I hope to incorporate some of the tricks that I used with the SR-71 and the A-10 to produce a stable aircraft.

Try to get:
1) Good hand launch, if not, a sturdy light gear.
2) A low landing speed.
3) A plane that can handle gusty winds.

It doesn't take you long to realize what ever goes inside the framework, once you glue the top on, it will require major surgery if changes are needed. I ran out of blue FFFoam, so now forced to use Readi-board from Dollar Store. Cut out my outline of the F-117 on paper

This is the nose and side inner plates. Much simpler to make.

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So, here is the bottom and cut and taped the elevons.

Next, shaped the nose and then fitted the two side pieces. The white section is where the top piece goes.

Fitted the top piece. Again, no glue yet.

Back to paper, to set inlets for air flow and outer design.

 

[L Edge]

It is taken time to get the correct inlet and outer frame design by just paper, but finally think I have it.

Next:

Ended up finding a plastic cup wrapped with storage tape and a foam cup segment insert glued that will hold the 64mm EDF and tapered down and cut so the exit is 90% of inlet area of EDF. A slot was cut so the leads could be hot glued to prevent air leakage. Motor was installed so it's electrical leads are lined up behind one of the housing vanes.

Concerned about keeping plane light and strong. Explored strengthen glued joints between joined wing and used thin basswood with 5 min epoxy that you can get at a hobby store. It is so thin that you can cut it with a scissors, so I tried some samples(works nicely) and installed it where it joins two halves of a wing.. Light as a feather.

Anyone who has launched a nose heavy delta wing ends up with a crumpled nose. So I decided to cut a triangle piece of basswood, iron on black packaging tape and epoxy it to the nose on the bottom. Well, at least it should give me a second chance to chuck it.

 

[L Edge]

Finished up doing the re-enforcements of the two panels where I took basswood strips and epoxy to strengthen it.

Decided to use landing gear since the weight of the F-117 with all foam parts cut out and the electronics including the 1300mah battery weighs 423 grams. Never used this type of foam, so to take the G loading, increased the area to reduce tear out of the gear. Glued it to the bottom. Broken plastic covering is cosmetics.

Inside F-117, used basswood(darker black) and epoxy to foam and then hot glue was used between foam wall and plastic housing.

Will be interesting final weight after all the landing gear and foam parts are glued together.

 

[hankflies03]

this is awesome! I'm reading skunk works right now so I will be watching this build and wanting to make my own!
I guess the only problem is that the f-117 needed a computer to fly and is aerodynamically unstable.

 

[L Edge]

Ended up doing all the shaping of the paper(no plans), cutting the foam and using hot glue to give the F-117 it's look and then installing the tail feathers.


The nose area has a piece of basswood covered with package tape now on top and bottom so if it noses in, it might prevent a crumpled nose. You can see it is darker then the foam board.

I ended up not applying scotch tape at joints, but used a heating iron to smoothen out the glue for the bends and cuts.

Cut out battery hatch and installed servos. Weight end up 560.3 grams which is 19.8 oz. Going to use a 1300mah 3 cell to keep wing loading down.

Have plenty of power(hovers at mid throttle controlled by hand) but, the gut feeling tells me to use a runway rather than launch by hand.
So until I get to the club field, I am at a standstill. Will video.

 

[L Edge]

Today, went to the back of an industrial park building and decided to try to taxi the F-117. After getting proper nose gear settings for full power and trying to lift off, it was a no go. Since the nose is the same height as main(remember no airfoil), went home and spent time and swapped the nose tire out so now the tail frame is at 3 inches and the nose is now 4 1/3 inches from ground.

So, now did advance throttle run for about 300 ft and no lift offs and was it haulin. Ended up with concrete rashes after bouts with swirly winds. Each time moved the battery back(1/4 inch) with no luck. Finally decided to increase throw of elevator.
Went for it and at 3/4 throttle, it lifted nose high, stalled out and survived. Tried moving battery forward 1/4 inch each time and same results.

So, now questions is, move battery or reduce throw. Or do I add more area to elevons?

Was happy the Readi-board survived with some wrinkles and scars, as well as the landing gear stayed together with my re-enforcments , surviving the stall outs.

Sure glad I didn't hand launch. Now know for sure, if it does fly, landings will need some power on the EDF with a slight nose high till you touch the ground.

 

[Mr NCT]

Today, went to the back of an industrial park building and decided to try to taxi the F-117. After getting proper nose gear settings for full power and trying to lift off, it was a no go. Since the nose is the same height as main(remember no airfoil), went home and spent time and swapped the nose tire out so now the tail frame is at 3 inches and the nose is now 4 1/3 inches from ground.

So, now did advance throttle run for about 300 ft and no lift offs and was it haulin. Ended up with concrete rashes after bouts with swirly winds. Each time moved the battery back(1/4 inch) with no luck. Finally decided to increase throw of elevator.
Went for it and at 3/4 throttle, it lifted nose high, stalled out and survived. Tried moving battery forward 1/4 inch each time and same results.

So, now questions is, move battery or reduce throw. Or do I add more area to elevons?

Was happy the Readi-board survived with some wrinkles and scars, as well as the landing gear stayed together with my re-enforcments , surviving the stall outs.

Sure glad I didn't hand launch. Now know for sure, if it does fly, landings will need some power on the EDF with a slight nose high till you touch the ground.

Just curious, are you using any stabilization? I think the real thing can't be flown without computer aid.

 

[L Edge]

Just curious, are you using any stabilization? I think the real thing can't be flown without computer aid.

No for stabilization. There are very few models out there that work without stabilization. I added two factors that may or maybe not work, so that is the fun of this project. I got fast speed to lift off, but it doesn't rise unless very high angles of elevator are used. Then it pops nose up (moving the battery or too much elevator? choices) and so far with luck with throttle and controls, it is not destroyed, only scraped and dinged.

So it never has had any forward flight(one adaptation is to help it prevent rolling) to find out if it gyro would help. It is like a Tomcat.
From many years of flying, plane should lift off at lower speed and it doesn't budge. Nose up attitude and doesn't lift, indicates battery needs to be aft. Did that only, then tried extreme movement on elevons, then it pops up and nearly stalls. So, is it somewhere between the two? or is it a unstable design.
Got any other thoughts? Open for suggestions.

 

[dap35]

No for stabilization. There are very few models out there that work without stabilization. I added two factors that may or maybe not work, so that is the fun of this project. I got fast speed to lift off, but it doesn't rise unless very high angles of elevator are used. Then it pops nose up (moving the battery or too much elevator? choices) and so far with luck with throttle and controls, it is not destroyed, only scraped and dinged.

So it never has had any forward flight(one adaptation is to help it prevent rolling) to find out if it gyro would help. It is like a Tomcat.
From many years of flying, plane should lift off at lower speed and it doesn't budge. Nose up attitude and doesn't lift, indicates battery needs to be aft. Did that only, then tried extreme movement on elevons, then it pops up and nearly stalls. So, is it somewhere between the two? or is it a unstable design.
Got any other thoughts? Open for suggestions.

Are your main gear too far aft? That could make it harder to rotate for take off.

 

[L Edge]

Are your main gear too far aft? That could make it harder to rotate for take off.

Want to thank you for the suggestion. I ended up moving it forward about 2 1/2" and was able to try to see what happens. Tried a high speed taxi run and then added up elevator and sure enough it lifted and stalled out going to left . Seem to me that it was slower speed that what I had. Again, was able to recover with only dings to the ship, not crashes.

So next step is to try moving the battery forward(small increments) and see what happens. Other concern is maybe the elevons doesn't have enough area. Deflection is quite high for the elevator when it does lift. Anyway, still have options yet to see if my version will fly.

Happy with the results of the Readi Board for it may wrinkle, but is holding its own each time is stalls out. Bad feature is don't buy the black foam, for I have been flying the 3D one and you can lose it in the air very easy. The wing is holding up nicely with the 3D maneuvers.

Again, thanks dap35 for the suggestion.

 

[L Edge]

Yesterday, got pushed into, let it fly or trash it says my son. So went to field and decided to lift off and then see what happens. Tricky it was and it seem to go nicely after landing.

Today, decided to go for it. Notice the guard rail, ignored it and blasted the power to it. It lifted beautifully and wow was a handful. Not enough aileron and made it to the ground. Wow, does a nice flare with almost no power. Took film, and it didn't work. Arghhh, so I ended up with 4 runs to get trimmed and it balanced out so it will do right and left turns fairly slowly to call it a winner. No major crashes, only dings and wrinkles.

Got my camera squared away and the fifth flight I got the video. Is it tricky to fly? need a FC? no way!!! I added some things to prevent that
and all done with a cheap 5 bladed 64mm EDF with a 3s 1300 lipo. Like all EDF's, need to keep some power on at all times to prevent those roll overs and stalls.

It will take a day or so to get the video up and shown here. My next project is a SR-72.

Only thing I dislike about this aircraft is the black Readiboard which requires 110% concentration in flight.
This flight shows short takeoff, easy left and right turns, sharp left turn and ease with throttle. Never got to push full open due to tight area and landing even shows nice flare to slow down or I would hit the guard rail. High grass doesn't allow nice landing since gear is very short.