Lockheed U2- Master Series 70mm EDF

[The Hangar]

Started putting the rest of the fuse together tonight. Due to the size of this plane it is impossible for me to either store or transport it in one piece. One of the biggest challenges for this build was designing a removable wing for an EDF fuselage that's pretty much just a molded tube with no internal structure. My original plan was to have either wing slide off like many store bought models, but I decided that torsion (wing twist) would become a huge issue without excess reinforcement, i.e. added weight. This technique works better with hot wire models.

I should've taken better pics of the system I've come up with, I'll post some later. Without pics the system is a bit tough to explain but I'll try. Basically a large section of the bottom half of the fuselage is removable along with the wing, the entire module is held in by rubber bands. The top half of the fuse offers structural support and joins the nose to the tail, tension from the rubber bands prevents this piece from flexing in flight.
The wing runs through the center of the fuse, forming two ducts above and below for air to travel to the EDF. It's not ideal and I think there may be some breathing issues so I've marked out some cheater holes under the wing that I'll cut out if needed.


Here you can kinda see how the wing is separate from the upper fuse as it pulls away a bit in the rear. The lighting makes the top look a bit flattened in this pic, it is round:

View attachment 185262

View attachment 185261

Now just to add the rear fuse and EDF housing and start wiring everything up.

Looking good, I like it.

 

[the rc project]

But joking aside, scaling your plan to fit the size of your 90mm EDF is simple algebra. I've never dealt with EDFs but I believe its just about the outside diameter of the fan housing, to scale the plane enough to fit that unit into the engine nacelle, or into the fuselage.

Comparing the thrust of a larger motor/EDF to the larger size & weight of the plane is another story. It may be that the thrust of the 90mm EDF compared against the smaller EDF scales to your advantage - giving you a large plane with even more power than it needs. I dunno. Like if the larger EDF gives you 50% more thrust, and you're fitting it to a plane only 15% bigger.

That’s exactly what I would expect. 90mm and I’ve tested on 6s and it makes 3.2kg of thrust! I understand Edfs are not efficient, but that’s exactly why I wanna fly some endurance with one! Lol

 

[LitterBug]

You may just inspire me to work on my U2 builds. I have a laser cut Balsa EDF kit, and have been working on a foamboard design of my own...

The U2 is basically a powered glider. unless you are trying to set speed records, I don't think the inefficiency of edfs is such a problem.

 

[Crawford Bros. Aeroplanes]

I didn't get much actual progress done today, I mostly just redid stuff that I did wrong the first time. Some measurements were off for the upper fuse half and it didn't really have the right shape, so it didn't join up with the rear fuse very well. I went ahead and redid the entire piece which took nearly two whole days because it just wasn't cooperating. I finally got it right and it actually works better than I expected. Now with the fuse center finished I can begin work on the tail cone and EDF mount.

My total forward progress for the past two days consists of the 3" ring at the rear of the fuselage:

And as promised a pic explaining how I made the removable wing:

 

[Monte.C]

I didn't get much actual progress done today, I mostly just redid stuff that I did wrong the first time. Some measurements were off for the upper fuse half and it didn't really have the right shape, so it didn't join up with the rear fuse very well. I went ahead and redid the entire piece which took nearly two whole days because it just wasn't cooperating. I finally got it right and it actually works better than I expected. Now with the fuse center finished I can begin work on the tail cone and EDF mount.

My total forward progress for the past two days consists of the 3" ring at the rear of the fuselage:

View attachment 185421

And as promised a pic explaining how I made the removable wing:

View attachment 185420

Killer!
And that's the most awesome 3"-ring-at-the-rear-of-the-fuselage I think I've ever seen. Must've taken you at least two days.

 

[Crawford Bros. Aeroplanes]

Killer!
And that's the most awesome 3"-ring-at-the-rear-of-the-fuselage I think I've ever seen. Must've taken you at least two days.

Haha
Master series builds can be tricky, sometimes the smallest little parts can be the most frustrating.

 

[Crawford Bros. Aeroplanes]

 

[Monte.C]

Haha
Master series builds can be tricky, sometimes the smallest little parts can be the most frustrating.

I'm with you there. I'm still filling, sanding, filling, sanding on my FreezerBurn. Just like I remember on boats. Almost ready for a coat of primer, but really it'll be a relief to go back to just cutting & gluing FB now.

Boy you got a beautiful U-2 there.

 

[Crawford Bros. Aeroplanes]

I'm with you there. I'm still filling, sanding, filling, sanding on my FreezerBurn. Just like I remember on boats. Almost ready for a coat of primer, but really it'll be a relief to go back to just cutting & gluing FB now.

Boy you got a beautiful U-2 there.

Thanks, hopefully it flies as well as it looks

For the boat are you fiberglassing over fb? Or just waterproofing it?

 

[Monte.C]

Thanks, hopefully it flies as well as it looks

For the boat are you fiberglassing over fb? Or just waterproofing it?

This is my airboat I'm building for snow. Kind of the point is that it'll take a bit of abuse, so I'm trying not to overdo it. Just FB, mostly brown FB. On the sharp running edges on the bottom I've let into the foam split pieces of bamboo skewers. Then filling & sanding and I'll rely on the paint for waterproofing.

 

[Crawford Bros. Aeroplanes]

This is my airboat I'm building for snow. Kind of the point is that it'll take a bit of abuse, so I'm trying not to overdo it. Just FB, mostly brown FB. On the sharp running edges on the bottom I've let into the foam split pieces of bamboo skewers. Then filling & sanding and I'll rely on the paint for waterproofing.

Ok cool

I've always kinda wanted to build an ekranoplan but now this thread is way off topic

 

[Monte.C]

Ok cool

I've always kinda wanted to build an ekranoplan but now this thread is way off topic

Yup.
U-2 will fly, no doubt. It's not made of magic. It's got lots of wing for the weight, and everything else is in it's proper place. No sweat! Can't wait for videos.

 

[Crawford Bros. Aeroplanes]

Yup.
U-2 will fly, no doubt. It's not made of magic. It's got lots of wing for the weight, and everything else is in it's proper place. No sweat! Can't wait for videos.

I'm not as worried about it as I sound hehe

 

[PoorManRC]

This Aircraft, as you well know by now, is much harder to design and build than its simple looks appear! You're doing an amazing job!! 👍👍
In its absolute essence, it's a F-104 with slightly different Tail Feathers and a long Wing!! Of course it's much more than that.

She will definitely fly. If anything like the original, LANDING will be a bigger problem. They float for long periods of time.

This is the exact opposite of what the people who try to make Foam Board SR-71s fly! The Blackbird has NONEXISTENT Wing Loading, they were THRUSTED into the Air with pure Force.
My Dad once told me about a twin unstart he experienced once. She dropped like a stone!! Thankfully they got one of the Engines fired, so they could limp home.

The U-2 almost doesn't need an Engine. It did require certain Thrust to maintain 75,000ft - in a VERY SMALL Speed Window between stalling and breaking up!!
But you won't have that problem. 😉

Your Model's Wing flex is 100% prototypical. The full length Wood Spar is definitely the best idea, due to the small Wing Chord. A Foam Spar won't hold.

@Monte.C Your RB-57 fascinates me! The whole B-57 family has. That long Wing, with Engine Nacelles right in the middle of the Wing Spar must have been QUITE a challenge to overcome!! 😳 I'd love to see how you did that.

 

[Monte.C]

This Aircraft, as you well know by now, is much harder to design and build than its simple looks appear! You're doing an amazing job!! 👍👍
In its absolute essence, it's a F-104 with slightly different Tail Feathers and a long Wing!! Of course it's much more than that.

She will definitely fly. If anything like the original, LANDING will be a bigger problem. They float for long periods of time.

This is the exact opposite of what the people who try to make Foam Board SR-71s fly! The Blackbird has NONEXISTENT Wing Loading, they were THRUSTED into the Air with pure Force.
My Dad once told me about a twin unstart he experienced once. She dropped like a stone!! Thankfully they got one of the Engines fired, so they could limp home.

The U-2 almost doesn't need an Engine. It did require certain Thrust to maintain 75,000ft - in a VERY SMALL Speed Window between stalling and breaking up!!
But you won't have that problem. 😉

Your Model's Wing flex is 100% prototypical. The full length Wood Spar is definitely the best idea, due to the small Wing Chord. A Foam Spar won't hold.

@Monte.C Your RB-57 fascinates me! The whole B-57 family has. That long Wing, with Engine Nacelles right in the middle of the Wing Spar must have been QUITE a challenge to overcome!! 😳 I'd love to see how you did that.

@PoorManRC thanks, I'm honored!
(I'm pretty good at trying to derail people's threads.)
Go to
https://forum.flitetest.com/index.php?threads/mini-rb-57d.65170/
and I'll meet you there.

 

[jfaleo1]

This Aircraft, as you well know by now, is much harder to design and build than its simple looks appear! You're doing an amazing job!! 👍👍
In its absolute essence, it's a F-104 with slightly different Tail Feathers and a long Wing!! Of course it's much more than that.

it is more than that but not much more the original U-2 even shared the root and tip airfoils from the F-104. Fun fact....

 

[jfaleo1]

View attachment 185424

Nice! Love it.

 

[Crawford Bros. Aeroplanes]

it is more than that but not much more the original U-2 even shared the root and tip airfoils from the F-104. Fun fact....

Kelly Johnson specially designed the U2's fuse from the F-104 and added wings, it is different but really not by much

 

[jfaleo1]

Kelly Johnson specially designed the U2's fuse from the F-104 and added wings, it is different but really not by much

and a different tail, but I always thought the airfoil thing was wild, Low aspect ratio fast, high aspect ratio jet glider, all with one basic set of airfoils.

Johnson was a GENIUS! P-38, U2 F104, SR71, Constellation. and SO many more.

 

[Mikey-101234]

Can you release plans for this?