Size 36: The build of an 18' B-36

b-29er

Well-known member
Hey can you post a link to some cad files if you have them I am trying to build a smaller b-36 in foam

Well you won't be the first...I'd talk to @Horseman3381, he actually had a smaller (6') b-36 with all 10 engines. He even bombed the large storch with it on accident! I'll be happy to share cad files, but they are pretty much going to be designed around the 18' size, i'm not sure how well they will scale back down.
 

Horseman3381

Well-known member
Hey can you post a link to some cad files if you have them I am trying to build a smaller b-36 in foam

Here is a link to the thread for my 6' wingspan B-36. The plans for it are on the bottom of the first post.

6' Wingspan B-36 Thread

I also have plans for a profile B-36 of the same size. I ran that one off some smaller Quad motors. I can try to find those and post them if you want something simpler.
 

b-29er

Well-known member
And surprise, here's another update: Airfoil sections have been calculated out, courtesy of Excel
The numbers mason.png
Basically, this spreadsheet takes the coordinates for an airfoil and automatically calculates the size based on the given airfoil section length (cad) and distance from the root of the wing. copy the whole column of 200 coordinates, open Autocad LT, create a polyline, paste, boom. airfoils. Now, you're probably wondering "gee, thats a lot of work, why would you do this?" Because the real article uses a wing that changes airfoils over its shape, like a different variant, different thickness. I'm at least going to match the thickness.

And after all that talk of scale, i'm most likely going to ditch flaps...at least for the moment. The current wing loading if i bring this right to where i want it to be, FAA legal at 55lbs, puts cube loading around 5.6, which is like a light trainer aircraft, except with a t/w ratio of over 1 to 1 at full power. They're also fairly complex on this aircraft, because they are in 6 sections. This would require 12 servos, which is a lot of weight, cost, etc. for a feature thats probably not required when the plane will be built light. This may also free up some weight for engine pods, who knows.

The current task being worked on is attachment. There is a basic design for wing spars and airfoil sections, but now they need to attach to the fuselage (that hasn't been designed yet, lol). The plan is to have the wing break into 2, split on the center over the fuselage. The wing will also take a bit of the upper fuselage with it when removed. The wings will most likely bolt together, and a few reinforcement pieces to give the spar its correct angle will also have bolt holes in them, threaded insert on one side, bolt hole on the other. The wings will then attach to the fuselage using more of these bolt pockets attached to a wooden airfoil section at 6" out that runs parallel with the fuselage. This will be done to prevent some of the torque seen last year from being effectively transferred into the fuselage mounts and damaging it.

Sorry for the lack of pictures guys, about as boring on my end as it is in yours. I'm hoping build starts in around a month, once everything is designed. Not leaving stones unturned this time around.
 

b-29er

Well-known member
Just a quick update here
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Spar design is about 90% done, integration needs to be made for gear and partial for engine mounts. Once done, its onto mass edits on the airfoils and engine mounts, then joiner box, all significantly easier tasks.

On the list of changes thus far:
-Wing spar has at least 80% less home depot ruler, and will be a multi-part CNC'ed wing spar. Front (green) will be .2", top/bottom box will be .2", rear i'm on the fence between .2 and .5", all plywood. Spar will come in around 3-4lbs per wing, depending on rear spar setup
-Probably getting fixed gears for now, just to get the thing flying by FFE
-Engine mounts will be glue in, rather than screw in (part of the green holes on the rear (red) spar), and utilize 1/2" plywood for an engine mount/standoff.

Posting may be scarce (like it wasnt already). The clock is ticking...
 
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b-29er

Well-known member
Man, i thought i said something about the clock ticking...
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Right, so theres an actual update that isn't just a screenshot. Here is the first test article of the new rear wing spar
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I have to give myself a pat on the back for the router work. kidding! this is CNC'ed.
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all together, this represents 1/2 of the span of wing. I'll draw attention to the distinct lack of glue-only joints and Home Depot rulers. Also on the cut
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The test article for the inboard engine mount. Its already coming to my attention that I will probably want to put another piece on a horizontal axis to aid in not gluing the engine mount plate cockeyed, but this is just a Proof of Concept on the most stressed engine mount on the aircraft. Design work will continue over the weekend, but test runs will probably happen late Monday or Tuesday for this engine mount.
 

b-29er

Well-known member
Just a slight update. I'm starting to realize that while there is still a month out, between my current work schedule and holidays, i maybe have 15 4-hour days after work and two weekends before Flite Fest, which is probably not enough to get this build done safely and in a manner i'm satisfied with. So this will not be at FFE, i will instead be working on a couple of alternate projects to fly.
 

b-29er

Well-known member
It'll most likely be ready for a fall maiden, depending on what happens with my housing situation, since i may be moving shop.
 

Horseman3381

Well-known member
It'll most likely be ready for a fall maiden, depending on what happens with my housing situation, since i may be moving shop.

Though I am saddened to not see it this year, I would rather you spent the time to do it right and be happy with it. Whenever it is completed I'm sure it will be amazing.

Look foward to seeing you at FFE!
 

b-29er

Well-known member
pardon the pause, just getting back into the swing of things
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I decided that, unlike previous ventures, I should actually design an elevator that, like, looks coherent, instead of making a sandwich of 1/2" pink foam and 1/2" square dowel rods held together with copious amounts of glue and home depot hinge. This time round the plan is to mimic the original. A 1/2" diameter aluminum tube will be used as the hinge on this elevator, with 3d printed bushings to rotate against. This has a couple of advantages, first, it allows me to get a proper cg on the control to prevent flutter, second, it adds a major structural element to the elevator, third, it looks scale. The rudder will be getting a similar-ish treatment, then i'm figuring how to attach all of this to the rear end of the aircraft in a coherent way. Also thinking standard servos may not be enough here, so i may go big or go home.