coyoteboy
|
| posted on 2/6/11 at 01:53 PM |
|
|
Two part thin composites - how
Seriously considering building something that requires a high aspect ratio wing shape and instead of making it out of something solid/heavy I was
going to make it out of fibreglass. The problem is I can't quite get my head around the best way of making such a wing. I've experience
making f/glass/CF parts already, but only for fun. My problem is the only way I can think of producing this is two halves pulled from a mould and
joined, but the joining/seaming process would be pretty much impossible with a long thin wing (~10mm thick). Instead I was considering a foam core and
vacuum bagging the length of it but I then can't be sure it'll stay flat/straight while being bagged. Assuming this wing would have quite
a notable load it would be good to ensure it's not going to fail but I struggle to find ways of joining two halves that won't fail unless
I can physically get inside the wing.
So I thought I'd throw the thought out to you lot, see if you can think outside the box.
|
|
|
|
|
vinny1275
|
| posted on 2/6/11 at 02:05 PM |
|
|
Could you not form the wing halves with a folded lip, so you've got a larger face to mount to (with some sort of adhesive I'd guess is
easiest), then fill the join line?
|
|
|
twybrow
|
| posted on 2/6/11 at 02:23 PM |
|
|
To keep it super flat, you will need some sort of reference/mould surface (unless your core is very stiff).....
Also consider - envelope bagging, lost core techniques (polystyrene, wax, low melt point alloys etc).
You need to understand composite manufacture to really make a go of this - single piece parts like that can take a fair bit of know how/experience to
get right... (4 years as lead composite development making large carbon aircraft propellers, now in charge of a team making the tools to build
composite blades [wind] up to 80+m long - I know the issues from first hand experience)...
I can happily chat some options through with you if you would like - drop me some more details by U2U and I will try to give you some help!
|
|
|
coyoteboy
|
| posted on 2/6/11 at 02:35 PM |
|
|
Cheers both! Looks like I found the perfect person!
U2U on the way!
|
|
|
Neville Jones
|
| posted on 2/6/11 at 03:19 PM |
|
|
It looks like you need to find out how one piece cfrp dinghy centreplates are made. Search the dinghy sites. Boats called 'Moth' are using
cfrp foils and rudders. Amazing to watch when they lift out of the water on the foils!
However, accepted practice in the motor racing industry is to form the leading edge with a tube, the trailing edge with a flat, and then glue the top
and bottom skins to that. The top and bottom skins are usually formed by two skins apiece, with a 5~8mm core.
To do it in a single piece easily(relatively), you need an autoclave and fairly intricate tooling.
The turbine blades are also made just down the road from me, and there's no great technology involved in any part of those, compared to what
you're asking.
Cheers,
Nev.
[Edited on 2/6/11 by Neville Jones]
|
|
|
designer
|
| posted on 2/6/11 at 03:39 PM |
|
|
Foam core.
Cut foam to section with hot wire and cover.
|
|
|
coyoteboy
|
| posted on 2/6/11 at 04:02 PM |
|
|
Neville - getting something to bond (i.e. tube and flat material) is not fun and requires etiher a heavy tube (metal/wood) or finding somewhere
selling f/g tube? Interesting proposal though. Thinking on it.
designer - foam core is fine but what method is used to cover it, I mean wrapping the leading edge is easy, but the trailing edge would have to be
just laid flat on flat, and then how do you stop the core bending when you vacuum it?
|
|
|
designer
|
| posted on 2/6/11 at 04:07 PM |
|
|
If the core is bagged properly there should be no problem when vacuum is applied as it should push from both sides. Rear edge is then finished by
hand.
Used to use this method years ago for wings, but in those days we fibreglassed it and sanded smooth later.
|
|
|
coyoteboy
|
| posted on 2/6/11 at 04:11 PM |
|
|
In theory it should be flat but I've had problems with kiteboards warping when vac bagged unless vac'd onto a flat surface instead.
I've done my time sanding things smooth, killer work - rather have it finished out of the bag so to speak lol. laminate>mylar>bag should
see it smooth enough if that route is taken but the curvy bits might pose issues I've not dealt with. The boards I've made were either
wrapped edges with large radii or just butted up to ABS rails which seemed to work fine for that application.
|
|
|
belgian2b
|
| posted on 2/6/11 at 04:42 PM |
|
|
Hello,
You have to make a model.
Thenn you make two half mould out of the model.
Be sure to make the moule strong and rigid enough to avoir any disformation when you take the mould out.
Thenn, you make you two half wings in each mould.
Last step : you fill the two half wings with some special glue ( i don't remembre the name) and you assemble the two half moulds.
That's the way i made Somers wings some years ago.
Gerardo
|
|
|
coyoteboy
|
| posted on 2/6/11 at 05:00 PM |
|
|
In your last step - what sort of glue, and when you say "fill" I presume you don't mean literally fill it (unless it's an
expanding foam glue?) or it'd be really heavy! More info on the gluing stage woudl be cool.
|
|
|
twybrow
|
| posted on 3/6/11 at 11:58 AM |
|
|
Depending upon what the shells are made of, I would look at either epoxy structural adhesives, or polyurtethanes...You could use your moulds as a jig,
to help with the accurate bonding - ie build two shells, with small internal return flanges. Run your adhesive along the internal flange, life one one
onto the other (complete with finished shells), then bolt the tools together to jig and hold your pieces toghter.. If you are nifty about it, you can
add alignment pins etc, to ensure an accurate assembly... Either way, I cant see you getting a good job without building a tool first (which as said
above, is best done from a master blade that you build, and then make the mould from).
I will try to send you another U2U this weekend, answering some of the specific points your raised in your U2U!
Some links to keep you busy this weekend:
Wind Power Projects
ColoradoWind
and another....
[Edited on 3/6/11 by twybrow]
|
|
|
Angel Acevedo
|
| posted on 4/6/11 at 11:14 AM |
|
|
How about reverse bagging?
You insert balloon -Long party ones , fiberglass over, then moulds.
Blow balloon, once resin sets, deflate balloon.
But I may be living in wonderland....
Please let us know which way you went...
AA
Beware of what you wish.. for it may come true....
|
|
|
