CNC help required for final year Uni project

[ChristoT]

Afternoon Fazer fans!

As some of you may know, I'm an aerospace engineering student. I am now in final year, and heading towards employment - God help us all.  I need some help with my final year project, and I wonder if anyone here can help.

For my final year project, I am working on a remote controlled aeroplane for an international competition: the BMFA Payload 3 Challenge. In essence, the team of four from my University have to design, build, test and compete a RC plane with a 2m wingspan, and carrying up to 4kg of dead weight payload. All powered by a single tiddly electric motor.

To me, the answer is obvious: make it out of carbon fibre. Thanks to my placement, I can make carbon fibre parts and their moulds. However, we need patterns. I'm going to approach several firms to ask for sponsorship for tooling block, but my team needs a CNC shop who can mill the block for us to our CAD models as the Uni's equiment is simply too small. Just to give an idea, each wing will be just shy of a metre long, and will need 2 moulds (and hence 2 patterns) each. We're going for a radical aerodynamic shape with a blended wing and body design, which means we will need comparatively fewer moulds for the entire aircraft.

What I'm looking for is a firm who can sponsor us with the CNC work. We need 10 patterns (8 if I can design the fins symetrically); or if the quality can be assured, and if each pattern can be made full size in one piece, we could skip the pattern stage and go straight to moulds - something that would save my team a lot of time, meny and effort for the same work done by the CNC firm.

If anyone can help, please let me know!  We're hoping to have the design finalised by mid November, so we'd be looking at around then for the moulds/patterns.

Likewise, if anyone can help with pre-preg carbon fibre, tooling block or fiberglass and high temp polyester resins, I'd love to know!

Thanks in advance!

[NorthWestern]

Can you not just make a hot wire cutter and use polystyrene?  Non pre preg is cheaper and doesn't need to be kept in a freezer   you can pre preg it yourself prior to use or do a wet layup. Why the need for high temp resin?

[ChristoT]

Can you not just make a hot wire cutter and use polystyrene?  Non pre-preg is cheaper and doesn't need to be kept in a freezer   you can pre preg it yourself prior to use or do a wet layup. Why the need for high temp resin?

Weight is going to kill us on this project. Whilst I know non-pre-preg (i.e. sandwich composite) is substantially cheaper, there is no way it can be made lighter. Last year's winner still had the petrol engine, which gave over 2x the power this years' single e-flight 10 gives us. Their plane weighed a scant 960g. That includes the 500g engine + ancillaries! If we have CF ribs with a single CF skin over the top, it will weigh next to nothing, yet still be sturdy enough. We need this thing to be under 1kg in weight, with the full 2m span.

The high temp resin is required because the pre-preg will be autoclave cured. And whilst the moulds will be single use, I don't want to risk warping. Not when the centre of lift and centre of gravity have to line up so critically!

 

[ChristoT]

Got a drawing? Ill price up what your asking for free if u want, let u know what it would cost.

No, we won't have drawings until mid November. The shape we're going for is reminiscent of the Wingco Atlantica BwB, hence the dimensions in thread. We have to design from scratch, but I'm trying to make sure we have as smooth a run as possible at this.

It doesn't help we have a really tight budget for this thing either...

[ChristoT]

Kinda like this, but with a 2m wingspan, larger tail fins, and a 2m wingspan. This is the design inspiring us, basically:

[dazza]

Let me help....Finished product should resemble something like this

[ChristoT]

Your artistic skills amaze me Dazza!






























As in: I'm amazed someone with that shit an idea of a plane can walk freely among us!! 

 

[midden]

Dazza is 'special'  did you not like his self portrait?

[His Dudeness]

You could draw it in sections using solidworks and then rapid prototype each section to give you a mould or draw it and build a basic mould from wood based on the drawing. I guessing you have to do some design, calculating and testing not just build it? If so time is going to be your biggest problem so keep the building side of it as simple as possible and do as much of the work in house as you can.

[ChristoT]

You could draw it in sections using solidworks and then rapid prototype each section to give you a mould or draw it and build a basic mould from wood based on the drawing. I guessing you have to do some design, calculating and testing not just build it? If so time is going to be your biggest problem so keep the building side of it as simple as possible and do as much of the work in house as you can.

That's the plan, Dudeness. Problem is that the CNC machines at Uni have a max bed size of 250mm by 500mm - and I still need to clamp the block to that, so that works out a bit useless for us! As the wings will be huge moulds, we can't monopolise the CNC machines for a week, then spend ages playing jigsaws with the bits. If possible, we'd like to do it in one hit.

[His Dudeness]

Don't use CNC is what I'm saying. You only need one working model right? You're not going to be making thousands of planes so you don't need a full cnc mould you just need something quick that'll work. A basic wooden model would do the job and then you can make your carbon fibre parts off that. That's the way I'd go anyway.

[ChristoT]

The main problem is a) one of material, and b) one of material.

If we can have moulds CNC'ed rather than patterns: great! They can go in the autoclave! For obvious reasons, I am NOT putting wood in an autoclave. That's asking for trouble.

Because it's a blended wing and body, the centre of lift and centre of gravity MUST match up. Because it hasn't got a horizontal stabiliser, trimming is minimal, if not non-existent. If the wing is not bang on our calculations, well, we're in the shit.

[His Dudeness]

Well fair enough you're the aeronautical engineer. If you can get the cnc mould done it's obviously the way to go. It's just that I know from experience that you're going to be stuck for time. The college year is quite short when you take into account all of the other stuff you have to get done so simplest solution is usually the best way to go.

[ChristoT]

Well fair enough you're the aeronautical engineer. If you can get the cnc mould done it's obviously the way to go. It's just that I know from experience that you're going to be stuck for time. The college year is quite short when you take into account all of the other stuff you have to get done so simplest solution is usually the best way to go.

Hey, always open to other suggestions!

Time will be a bugger. However, if we can get the moulds done in a fortnight, and before Christmas, we'll be ahead of schedule. Thinking about it, all we need is the wing moulds. We could probably manage the fins and fuselage patterns on the Uni's rigs. Still in sections though!

[His Dudeness]

So finalise the design, do the drawings, find someone that can cnc them, who can do it straight away, at a reasonable price in a fortnight? It'll be tough!

[ChristoT]

So finalise the design, do the drawings, find someone that can cnc them, who can do it straight away, at a reasonable price in a fortnight? It'll be tough!

Hence why I'm asking now! I want everything set up so when the wing design is frozen, it can go straight out to the CNC shop. Don't want to start looking for stuff when we're ready to make the thing!