Who remembers those old printed FIBREGLASS shower curtains that were all the rage in the '70's? Now if we had about 20metres of that in a nice purple,red and orange......

Wouter,

Its not really correct to say that it is just GRP with a different resin.

The properties of a composite aren't just the sum of their parts.

To take the classic, glass fibres in epoxy as an example. Both glass fibres and epoxy are terribly brittle on their own and pretty much useless as an engineering material. It is the way they are combined that makes them a useful composite (or material).

It may not be right to call it a new material (lets say a new composite), but its more than just a new resin, as the impact resistant properties come from the way this composite forms during processing.

As John Alani points out you could make a hull out of anything that absorbs resin, but you may not get the properties you expect.

People have been trying to combine carbon and aluminium for some time with varying degrees of success, it is very difficult to get them to process together but when they do you get a great composite. This is starting to be used in Formula one.

Gareth
www.fourhulls.com

It always seems to be implied that a boat of 10 x stronger (in tension) material is 10x stronger. You boat/mast whatever does not fail in tension. That is, in laymans terms, the skin does not pull apart (on the leeward side of the hull,say) but rather buckle on the compressed side. As such, the method of spacing the layers (foam) is very important.
It is a bit like trying to push things around with ever stronger string!
This is why wood stays a firm favorite with everyone except the quantity manufacturers, and gee wizz crowd.
Honeycomb cores (wood cells?) (and other duplications of nature) are the key to this resistance to buckling.

[quote]Wouter,


"People have been trying to combine carbon and aluminium for some time with varying degrees of success, it is very difficult to get them to process together but when they do you get a great composite. This is starting to be used in Formula one."

Aircraft Industry uses kevlar skins with aluminium honeycomb floor panels, other areas use Nomex core with aluminium skin. I've been using sheet aluminium hand molded to shape, its soft and retains the shape, then covered in carbon. Its like using a one off male mold that you leave in the layup, its light and the aluminium gives you something decent to screw through or attach fittings.
Darryn
Mosquito 1704
South Australia

Darryn:
Can I ask what kind of glue and surface processing you use to make that combination stick together? It would also be good to know how you deal with electrolysis if you use carbon.
I know that you need special glue films and autoclaving, or great amounts of epoxy-filler to make alu-honeycomb stick to glass.

I got a tip some time ago, to sand the alu with 80grit sandpaper and apply the epoxy immediately before oxydation starts. Is this what you are doing?

Darryn,

What I was talking about is slightly different, I think what you are describing is a sandwhich construction, where a composite skin is sandwhiched with an Al skin or honeycomb.

I was talking about a aluminium that has carbon fibres impregnated into it.



In this case you get a composite that is nearly as light as Al but as stiff as steel.

Gareth
www.fourhulls.com

I understand what you saying.

Wouter

Right on !

David

Probably, Have you seen the new machine they use to make carbon tubes. It knits a tube over a mandral. It looks a lot like the machine used to make tube socks.

If you are interested, I have ~1000 yds of 58K carbon. We could make a boom.

All joking aside, that is roughly how I made my new cross beam for the F14. I made a thin tube as a form and then wrapped it with nontwisted carbon yarn at 45 deg, -45 deg, 0, 45, -45. It is very slow. Watching epoxy harden while you do it is entertainment and makes the time go faster

I did not think about it but there was a machine on TV years ago that knited tubes when you turned a crank. It would have to be faster. I will have to check ebay.

Look up aluminum alloy M2 and I think M4. They use boron instead of carbon. It's good stuff.

There has been a steady development of metalic composites over the years. They started with dumping a handfull of something into molten metal. They are getting a lot better at it. The current best looks like fiberglass applied with a chopper gun except they are using ceramic fibers and aluminum instead of epoxy.

Carl and Gareth,

I found your post about impregnated aluminum very interesting this morning, not for the boating community, but for the transportation community. Specifically, using the sandwiched aluminum and even more importantly, the composite aluminum as bridge components. Since I have not been in the bridge community for a few years now, I forwarded on your posts to a US bridge expert in high-performance materials for his consideration. He should know whether we have already tried it, are considering trying it, or should consider trying it. Thank you for sharing the information. You may be revolutionizing bridge design and construction with you posts here on Catsailor.

So Darryn,

If I wanted to build a pair of lightweight beams or whatever, I could use, say, some of that very thin aluminium boiler flue piping from a builder's merchant and coat it with carbon strip bandage @45 degrees for layer 1 then, say, laid lengthways for layer 2 and then @45 degrees the other way for layer 3? Then I'd have a light and very strong beam? (I realise I'd have to vacuum bag it).

Using 2024-O aluminium, roughed up with sandpaper, cleaned with MEK, West System epoxy,600Gsm woven Carbon, keep it warm with a light bulb, the aluminium helps here once again.
I only vacuum bag when I've finished prototyping, my prototypes usually get tested to destruction unless I cant destroy it when I overload it to a degree that I am satisfied with, then it may become the finished product.

I use this process for fairings/brackets, I dont deal with electrolysis apart from sealing the item well and inspecting regularly, so far I haven't had corrosion issues. My plan is to use well bonded conductive foil in the laminate, similar to what is used in aircraft fairings to dissipate static electricity build up if it becomes an issue.
Darryn

You could use that as a former, anything really but if your going to use it for a beam the former might as well have some structural integrity. Aluminium can be quite heavy for its strength when it is formed into a tube and you will loose its benefits when its wrapped in Carbon. I've used balsa but found I had to use so much Carbon it was quite heavy and also expensive due to the amount of carbon I used. Balsa laminated was better. The best so far has been Canadian Spruce, same quality that is used in aircraft spars. Its light, cheaper then the aluminium/balsa I was using and very nice stuff to work with. I've made some Laser Tillers using Spruce wrapped in carbon that have stood up to years of punishment, none have broken. You could build a box section spar from spruce then wrap it in carbon.
I'm sure there are even better products to use as a former out there somewhere, I'm always on the look out.
I wouldn't worry about vacuum bagging until you have built something that might do the job, once you have the processes involved in building sorted out and a prototype that has been tested and looks like it will stand up to the job you can then build the final piece with the object of maximum strength and least weight. Testing it against the prototype will give you confidence when its used in the final application.
I've done alternate layers of carbon wrapped at various angles, seems to work out well, its going to be very messy though.
You need to keep in mind that the info I'm giving you is the result of experimentation in my spare time, I like to tinker, see what I can get away with, I dont get to concerned if something fails as I will just build a better, stronger one.

Work out what you are aiming for by testing what is in place now.

Darryn
Mosquito 1704
South Australia

Thanks for the description of your process Darryn!

What I was discussing is not a sandwich. It looks like al alloy. The fibers are contained in the metal.

Al carbon sandwich is another story. I general it does not work well. They delaminate. I have tried it and I have a Marstrom Al/carbon rudder crossbeam. The results are the same, delamination. M&P handbooks list 2 problems. Unstable surface on Al. The Al oxide surface finish forms over time and the epoxy bond breaks. Also there is a problem with the difference in stiffness and response to load unless the Al is foil thick.

Thank you Darryn,

I'll try some experiments soon. I've been toying with a few ideas for building my own boat for some time, but I want to be sure that I can do it a) as cheaply as possible and b) the way I want it rather than having to incorporate proprietary extrusions etc. that might not be ideal to the way I want it. In particular I wanted to try and develop a 'one piece' style of construction where the beams are blended into the hull once all is bolted together and avoid the current appearance of all catamarans where at best the hull is faired to allow the beams to sit into the trays and give a smooth appearance.

I've just read what I've written and I don't know that I've made myself clear.....

I want the beams to form the fairing at the hull junction not the other way round.

Anyway it's just a sort of idea at the moment.

Thanks again Darryn.

What about the new material GLARE (Glass reinforced laminate) used for airplanes (airbus) and developed at Delft, the Netherlands ? Could this be used in the catscene ?

I think you have this backwards- kevlar on the outside and carbon on the inside. Otherwise the carbon is doing ALL the work as it's the stiffest of the three.
With a Kevlar/Wood/Carbon layup, the kevlar distributes the load to the wood, which in turn distributes the load to the carbon.
With the Carbon/Wood/Kevlar layup, the carbon takes all the load and the wood only absorbs load when the carbon cracks.

What do you think of that Mary? Delft now famous for crocheting up glass fibre?