new hull material

We have just taken delivery of a new set of hulls, made from a new material.

We use a thermoformed Polyproylene/glass fibre material. This has the advantages of being as stiff and lightweight as the best of the current composite boats while having very much increased durability and impact resistance, similar to that of the rotomoulded boats.

This is not a new process, it has been used by some white water Kayak manufacturers and the Royal Navy RIB's, it also used on bus bumpers!, but we beleive we are the first sail boat manufacturer to use this technology. The Royal Navy claim they can't break the boat even with a sledge hammer.

Anyway sailors can be a sceptical bunch, so I want to be able to prove that the material is as good as we say therefore we are having some tests performed at the local university. What I need to know is what is a typical layup for a strong modern composite boat, like an F16, F18 etc. so we can compare like with like. Does anyone know?

All the best

Gareth
www.fourhulls.com

Just an idea..

How about letting epoxy treated marine ply be part of the test? This material has well known properties and have been used extensively in small catamarans. Perhaps not the best if you want to convince 'modern' beachcatsailors about stiffness, longitivity etc. tough..
The F-18 Blade (ref: F-16 forum) was buildt in marine ply, and they added a lot of glass to achieve class minimum weight. So testing with marine ply is at least relevant.

Will your new hulls break if you are T-boned at speed? I bet the Royal Navy never performed that test

Since you have glass added to the plastic, will it be possible for amateurs to do repairs (unlike the usual thermoplastic) with epoxy and standard glass?

Thats a good idea, I have heard it said that this is more impact resistant than a normal GRP layup. So what is a normal layup for epoxy treated marine ply.


I would be happy to supply the hulls to be T-boned if someone wants to volenteer a boat to do the T boning

We are told it can be repaired but have not tried it yet.

Gareth
www.fourhulls.com

Any idea what a thermoformed Polyproylene/glass fibre boat would cost relative to other materials?

It is similar in cost to a modern GRP construction.

Normal layup varies from just the plywood (quite normal), to reinforced with glass on both out and inside.
I buildt a Quattro 16 (Richard Woods design) reinforced with 200gram glass on just the outside. The Houlton ply-Tornados was reinforced with 90gram on inside and 250gram glass on the outside (ref: http://www.thebeachcats.com/modules...ile=index&req=viewdownload&cid=6 ) (not sure if it was 90 on the inside, need to check the plans).
I heard the numbers for the F-18 Blade as well, but I dont remember them now. But it was quite overbuildt to make it achieve class minimum weight, this also made it quite a bit stiffer as well. 135gram and 300gram springs to mind, but I am very unsure about these numbers.

I am totally depending on my long-term memory now, but I seem to remember that Marstrøm uses a 250gram layup on the outside of his Tornado hulls. Dont remember the inside, but I'll try to find out where I read this. He mixes several types of foam, nomex honeycomb, pre-pregs, glue-films etc. in his boats, and autoclaves them to achieve his quality criteria. If you want to go that far, you can probably get more information about this from Kevin Cook who frequents this forum.

After re-reading what I just wrote, I realise that I have a terribly bad head for remembering numbers
Hope it's somewhat useful anyway..

If you want to really test the material, you can always take a sledge-axe to them (the axe you have reserved for the really stubborn, knotty and cross-grained firewood). Not very scientific, but probably very satisfying if the hulls survives (Warning: might help you find out if it's repairable as well)

Hope you will post some results after the tests are done on your website!

As a WAG I would suggest:

For "high tech"

3mm marine plywood with ~6 oz fiberglass/epoxy on the outside and 2 layers of epoxy resin on the inside

2mm Carbon epoxy either use prepreg or vacuum bag to the highest delta P you can. If you are testing impact resistance, make up a sample with 1 additional layer of Kevlar 49 near the middle. This will reduce crack propagation.

Extreme High Tech

2mm marine plywood or 3mm cedar strip with 6 oz carbon cloth on the outside and 6 oz kevlar 49 on the inside, Epoxy hand lay-up

For production

2 layers 8 oz fiberglass cloth on the inside and 2 layers 8 oz fiberglass cloth on the outside of 4 mm marine foam core. 2 samples 1) Polyester resin, hand lay-up and 2) epoxy resin vacuum bag @ 10-15 mm Hg

3-4 mm Fiberglass/polyester, hand lay-up

Find broken production catamarans. Cut section from the side of the hull in front of the front crossbeam.

This is a guess, but it is probably not too far off.

grob,
whats the weight of this material?

do you have a grams per cubic sq meter figure?

Because it is a thermoformed plastic it doesn't come in weights that are directly comparable.

i.e. GRP cloth weights are gsm before resin is added, not sure how you turn gsm into a final weight or density as that is what really counts. Also the final weight of various gsm materials depends upon how well it is processed.

Anyway our material has a finished (processed) density of 1.5 grams/cm3 (g/cc). It has a glass content of 60% by mass and 35% by volume.

I think this is a farly long winded way of saying its about the same weight as GRP.

Gareth
www.fourhulls.com

An A-cat hull is about 7 sq. mtr. in surface area and weights about 14 kg.

The specs you give for the new material ; 1.5 gram / cm3 = 1500 kg / m3 suggest that you can make the A-cat hulls of the your material only 14 / (7.5 * 1500 ) = 1.24 mm thick. That is not going to hold.

FX-one hull weights about 35 kg and has about 8.5 sq.mtr. surface area => max thickness with new material = 2.75 mm

You are not going to make lightweight hulls with this new material.

For example marine ply comes in around 600 kg/m3. You can get 2.5 times the thickness for the same weight by using this time tried material. And thickness counts in boat building.

Sorry

Wouter

You are trying to baffle me with maths again, aren't you

1500/600=2.5 as thick ?


Oh no I've been such a fool, I wish I had talked to you before I invested all that money. That 11kg hull sitting outside must be a figment of my imagination

But seriously don't your numbers tell you something, those boat hulls aren't 1.24mm and 2.75mm of solid GRP are they? They are sandwhich construction. And so are mine.

Gareth
www.fourhulls.com

One of the great advantages of this material is it is basically the same as GRP with much higher imapct resistance, So any construction you can do with GRP you can do with this.

So for example to match an A cat construction for weight and stiffness you would use 0.5mm of new GRP/PP both sides of a 5mm foam layer, and to make the FX one you use a 1mm skin of GRP/PP both sides of a 5mm layer of foam.

Many thanks to Carlbohannon and and Rolf Nilsen for those numbers, I will let everyone know the results when the tests are performed, if anyone has any more data (Wouter?) I would be pleased to hear.

By the way when you describe cloth as being 8oz or 6oz is that 8oz per square yard?

All the best

Gareth
www.fourhulls.com

You didn't tell us that a foam sandwhich construction was used, you said it was a new hull MATERIAL.

You wrote :"Anyway our material has a FINISHED (processed) density of 1.5 grams/cm3 (g/cc). It has a glass content of 60% by mass and 35% by volume"

No mentioning of any foam content here.

Apparently, with the new post, the only new thing about this material is that it uses some other stuff to replace the poly-, vinyl- or expoy resin in otherwise the same setup.

Can we call it a new resin then; instead of a new material ?

Or are you calling Kevlar reinforced laminate a new material as well ?

Wouter

You may also want to try a plain 4 mm marine ply saturated with epoxy, no glass applied (if you warm the ply and resin up before saturating than it gets a nice penentration.

This skin setup has a rather good impact resistance as well; combined with being light weight. Homebuild F16's are build this way.

For the remainder I agree with the others

Wouter

From the most recent issue of Multihulls Magazine, there is a report on the speed sailing contest and a catamaran made of Flax fibre was an entry. FlaxCat as it is called, is from a Dutch sailor, name of Neils Haarbosch . I have not been able to find an English language webpage on most of the details, but here is what I did find: The Dope Boat

Mike.

But it still uses a resin. Although it doesn't say in the article what type of resin.

With modern epoxies surely you could make a hull out of just about anything that absorbs resin????

Sure, but the fibres are what imparts the strength to the composite...the resins just hold the fibres together.
There would be no reason to need carbon fibre if any good resin was sufficient to getting the strength/stiffness you needed.

Mike.

Just a side-note: Zeke Smith in "Understanding aircraft composite construction", refers to a builder (Molt Taylor) who used paper extensively when building airplanes. I dont know the Young modulus for cellulose, but I see that Flax have a breaking strength of about 100k psi. Common E-glass 500k psi and kevlar49 700k psi. I guess the Young modulus fallows approximately the same trend.

So, it's quite possible to build a boat with flax and epoxy as matrix, but it would need to be heaver than the same boat buildt in carbon or glass.

I think it's cool that boats are buildt in different and 'new' materials. Who knows what we might learn.

And if you eventually decide you'd rather have a glass or carbon boat, you can always smoke your Flax boat...in Belgium anyway

Do you think I could crochet a boat with carbon fiber yarn and then waterproof and stiffen it with resins? Put us women to work building boats.

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?

First, a practical matter, It is very hard to sand and fair Kevlar, it fuzzes. So you put it on the inside so you don't have to finish it. You can cover kevlar with glass or microballon epoxy to fair it but that is dead weight

Second, Components of a laminate do not take load individually. It is the strength of the whole. Once you exceed the strength of the whole, it starts delaminating, becomes about as strong as wet cardboard and and the whole thing falls apart.

Third a Carbon/wood/Kevlar can be made lighter and cheaper than a carbon/wood/carbon. Plus Kevlar has great impact resistance and tension strength. In case of a sharp impact, like a collision, there are a lot of cases where the carbon would break but the wood/Kevlar will flex or not break clean so the hull would hold long enough to go home and fix it. That is the theory plus panel testing plus hear say from white water kayaks anyway.

Fourth, for a homebuilder Kevlar is easier to laminate and a lot cheaper. I have bought it for as little as $2/yd on eBay. Carbon is ridiculous on eBay. To make carbon junk for their car, people are paying more than they could buy it from a real dealer like Fiberglass Supply Company.

Carl

Imagine if we could build our boats like this, 1 piece, the technology is already out there.
"The Premier I composite fuselage consists of 2, filament wound cabin sections (1/8th inch carbon fiber filament that is pre-impregnated with epoxy) that are bonded together."
Check out the pic.

I like the Kevlar on the outside idea. Makes good sense.

Darryn
Mosquito
1704
South Australia

Darryn, now you are getting closer to my crocheting idea, because I was thinking about how to make it as one piece, like a big sock, whether crocheted or knitted or woven, around the hull's internal structure and bulkheads. I'll bet a good basketweaver (or hatweaver) could make a REALLY light boat using palm-frond leaves (or whatever they use) -- and those are available in huge quantities for FREE.

Let me be blunt. Don't put Kevlar on the outside of a core composite. It is likely to fail.

In general, near worst case, for a catamaran the outter layer of a core composite is in compression and the inner layer is in tension. Kevlar is strong in tension and weak in compression. Look at what happened to the Kevlar/foam core Tornados. The Kevlar failed in compression. This also applies to similar materials like Specta/dynema/Vectran/etc

I hate to keep this thread alive BUT I don't want anyone to spend time building something that may fail.

I believe the Taipan 4.9 comes with optional Kevlar hulls, and I had assumed (although in complete ignorance) that it was on the outside. Anyone know?

I believe Boyer uses Kevlar on the inside and glass or Kevlar/glass on the outside. In any case Boyer has done suffient engineering to make sure their hulls hold up.

The real problem is a homebuilder substituting

Carl and Mary
Your crochetting idea is already in production, Forte RTS http://www.forterts.com/per.html uses a computerized braiding machine to make carbon parts. This technology is directly from the weaving industry. The carbon (or whatever fiber) is wound around a mandrel, so you need a mandrell in the shape of your part. As its being wound, it is impregnated with epoxy. It is then put in the autoclave, and cured at elevated heat and atmosphere. The result is strong, light and very reasonable priced parts. I bent 4 aluminum booms (falling on them) before I got a forte boom. I have beams, spin poles, booms and tiller extensions, and tiller connectors. The only thing is that the outside "skin" is an "uncontrolled surface" so its not smooth, it has texture and it needs to be UV coated. Tony will make you spars to your specs for very reasonable prices.

also, ebay carbon is a rip off. Go to carb.com for the best prices that I have found on the internet. 5.7 oz carbon weave 30 inches wide is $14 per linear yard at carb.com. 50in wide is like $20 and I have seen it at over $45 per linear yard other places. Ebay was even higher, its some guy selling his scaps, or selling sheets with epoxy already hardened to people for accent parts in their cars. Carb.com is in Hawaii. They told me prices were going up. Order now.

I also found good prices on nomex from http://www.plascore.com/ they were about 1/2 the price for 1/4,5lb,ox - a 3x8 sheet was $50. The lead time is 6 weeks.
I talked to Wade.

Wouter, Your 14kg figure for an A cat sounds low. 17kg-18kg target is what at least 6 new home built A cats are shooting for - check out the pictures http://intcanoe.us/mygallery/index.asp?offset=0 17-18kg is a total hull weight. I used 5.7oz carbon, 1/4 corcell foam and 2 gallonsmas epoxy with 1 gallon hardener. The hulls are 6 sq meters. I got 4 hull halves to weigh between 6kg, and 6.1kg, no paint, no gel coat, no dagger trunks, no sterns, no bulkheads. My all up hull target is 17kg. The trunks are super light high mod carbon Hall parts. I think they weigh 30 grams each. The biggest unknown is the finish - paint can weigh 3 kg per hull.

Any ideas on lightweight hull finishes? How about wood veneer? How about wood printed paper? How about a hawaiian print fabric? All white is boring.

Bill

The Taipan 4.9 can be ordered to have a glass/kevlar hull skin. If memory serves me right this means that the sandwich construction from outside to inside is :

Gelcoat
Glass
Kevlar
Foam
Glass

You don't want Kevlar on the outside of the outer layer as well as it forms a vary rugged fluffy surface when is touches something abbresive. Glass wears down alot more smoothly.

The kevlar is only in the hulls to give it extra impact resistance. If makes the hulls alot harder to dent. It is not in there to improvement tensile strength or stiffness of the whole hull.

Wouter

14 kg was taken from Marstroms webpage

http://www.sailcenter.se/administration/Boats/acat/aclass.asp

I know that homebuilder used to build A-cats for as little as 45-50 kg's before the 75 kg rule came into effect. However if you pitchpoled one of these than you would break the hulls. I think they used 3 and 2.5 mm marine ply for these hulls.

I'm often amazed of how light you can actually build when using marine grade ply. It is pretty good boat building material and it is very impact resistant.

Wouter

There is a very good description of the layup of the Shadow hulls in the following sail test under "Design and Construction"
http://www.shadowsailing.org.uk/documents/Yachts%20and%20Yachting%20Shadow%20test.pdf

Damn, my boats going to fall apart, its double Kevlar so it probably wont even make it to the water before the outer layer fails in compression and then, because its platform weight is 55kg it will break up when I pitch pole, dont know how it has survived the last 16 years
Darryn
Mosquito 1704
South Australia