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.