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BOB v4 Build for FF East 2019

JTarmstr

Well-known member
#21
Ok so with the destructive element in my mind, I have an idea. Anyone who has worked with army helicopters or is an military aviation nut like me knows that Helicopters such as the AH-64, AH-1, MH-60, MH-53 and a lot of life flight helicopters have wire cutters on the front fuse and tail, that way when flying at low level they can cut wires they run into before it hits the rotor shafts and potentially causes more damage.

MH-60_LI.jpg

So what does this have to do with BOB? Well I propose a sort of 'Plane Cutter" A carbon fibre or fiberglass stick mounted with epoxy to a small baseplate made of aircraft grade plywood at about a 45 degree angle forwards, From what I have seen of the videos of BOB, he gets hit enough to make it a possibility that 1 or 2 of these would possibly destroy someone's prop or wing in combat.

PS: if you want it to look cooler use a bit of dollar tree foam to make it look like a real wire cutter.
 
#22
The reason I use wood on the tail isn't really structural, the fiberglass insulation board is quite rigid already. I use the wood to protect the edges from incoming aircraft, which the wood is suited very well for due to the shape.

Working with arrow shafts at this scale is more challenging than with standard foamboard builds due to the concerns that @Fidget outlined above. I love them for my smaller stuff, but I'm not sure where they fit in on Bob.

Still, nothing is out of the question right now, I'll have to see where the build takes me.
 
#23
Ok so with the destructive element in my mind, I have an idea. Anyone who has worked with army helicopters or is an military aviation nut like me knows that Helicopters such as the AH-64, AH-1, MH-60, MH-53 and a lot of life flight helicopters have wire cutters on the front fuse and tail, that way when flying at low level they can cut wires they run into before it hits the rotor shafts and potentially causes more damage.

View attachment 132319

So what does this have to do with BOB? Well I propose a sort of 'Plane Cutter" A carbon fibre or fiberglass stick mounted with epoxy to a small baseplate made of aircraft grade plywood at about a 45 degree angle forwards, From what I have seen of the videos of BOB, he gets hit enough to make it a possibility that 1 or 2 of these would possibly destroy someone's prop or wing in combat.

PS: if you want it to look cooler use a bit of dollar tree foam to make it look like a real wire cutter.
You know, I was loading into a UH60 in April and I was wondering what those were for.

I have some fun plans for both offensive and defensive combat tools this year, trying to keep it safe though. (Looking at you Delta with a stake on the front)

This definitely sounds like a neat concept, not sure how I'd implement it on BOB though.
 

JTarmstr

Well-known member
#25
I have some fun plans for both offensive and defensive combat tools this year, trying to keep it safe though. (Looking at you Delta with a stake on the front)

This definitely sounds like a neat concept, not sure how I'd implement it on BOB though.
If you want I can draw up the concept and how it would attach to BOB, your call though, if I go to flite fest 2020 though I might try this on a overbuilt FT cruiser.
 
#26
Alright, time to post the product of another late night CAD session.

I wasn't happy with where my work last night was going, so I started from scratch. Here's the result of two hours in the flow on Fusion 360.

Bob Forum Render 3.png
Primary shot. Missing motor pods and ailerons, I knew those were going to be frustrating to work on so I put them off until a later date. Probably tomorrow. 150" Wingspan, 30" chord, 46" horizontal stabilizer, 26" vertical stabilizer, 96" fuselage length, and as always a girthy 18" fuselage width and height.

Bob Forum Render 1.png
A quick view of the ribs, certainly not finalized (still missing ailerons, fuselage mounting, spacing, etc) but pretty indicative of where my head is at right now for the project. Still might stick to tradition and add dihedral, we'll see.

Bob Forum Render 2.png
Nice view of the landing gear plan, aluminum mounting brackets, and thick axles are the key. I like the wheel pods I had for one flight last year, so I'll have something similar this year.

Bob Forum Render 4.png
Shot of the tail, wood everywhere, going to be using metal hinges again.1/4" thick wood on the hinge points to screw the hinges into, making the slots to sink the wood will be a pain but I'll probably just build a jig for the router.

As always, comments and input would be greatly appreciated.
 
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rockyboy

Skill Collector
Mentor
#27
You mentioned earlier that Bob had a lot of dead weight up front to balance out - and the best way to avoid that is build lighter in the tail.

If the wood leading edge strips are for protection instead of stability, perhaps thin carbon, fiberglass, or even corrugated plastic strips from roadside signs can serve the same protection role while saving you several ounces of nose weight to balance.

Also, consider the large scale 3/16" Robart hinge points instead of metal hinges - they drill for installation rather than go into a slot, and there are good reasons why the giant scale builders use them instead of hardware store material. https://robart.com/collections/control-hinges/products/3-16-super-hinge-points-15
 
#28
You mentioned earlier that Bob had a lot of dead weight up front to balance out - and the best way to avoid that is build lighter in the tail.

If the wood leading edge strips are for protection instead of stability, perhaps thin carbon, fiberglass, or even corrugated plastic strips from roadside signs can serve the same protection role while saving you several ounces of nose weight to balance.

Also, consider the large scale 3/16" Robart hinge points instead of metal hinges - they drill for installation rather than go into a slot, and there are good reasons why the giant scale builders use them instead of hardware store material. https://robart.com/collections/control-hinges/products/3-16-super-hinge-points-15
Those hinges look like a nice option. I'll probably use them.

Last year the primary reason I had tail heavy issues was that the batteries were held in the motors pods, not the nose. I figure if I fix that this year it shouldn't be a problem.

Edit:

Cleaned up the tail and incorporated the hinges into the design.

Bob Tail Clean.png Bob Rough v15.png

Another edit:

Just ordered everything from Hobbyking, should have it next week.
 
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#36
Now that I have some time I’ll give a quick write up of what I’m doing.

My first priority is getting the wing together, so I transferred my wing profile from Fusion 360 into the drafting tool, exported as a PDF, and tiled it onto four sheets of paper. I then cut out the rib template, traced the outline onto two sheets of 1/4” plywood, and got them cut out on my “new” scroll saw (manufactured in 1945). After some sanding they were good to go, I drilled two holes for alignment nails, sandwiched 3/4” Lowe’s insulation board in between and got cutting. I’m using a fixed Hotwire and moving the work piece, each rib takes about three minutes start to finish.

Next up will be either wing construction or cutting fuselage and tail pieces, I haven’t decided.
 
#40
Didn’t get a chance to take photos before I left for a beach weekend, but I cut out all the fuselage side panels on the hot wire. Should be able to take photos of a fuselage mock-up and start assembling on Monday. I have a big stack of wing ribs cut, but I’ve been procrastinating wing construction.