Composite boat-building materials & techniques

[fastcat435]

Originally Posted by BigCat

"glass fiber/vinyl ester infused hull designed for a light hull weight and very high speeds. Kapadia says that VT considered carbon fiber for the FRB hull. Resin-infused carbon/epoxy and carbon/epoxy prepreg were found to save only 3 percent and 15 percent, respectively, in terms of weight, with a large cost penalty."

Can this be true? It's from Composites World, so it's not the usual clueless reporter writing who doesn't really understand the story-

Hallo Big Cat

I find 3 % or 15 % an fantastic saving . now you have totally convinced me that vinylester is definately not the way to go.
If I take the lowest percentage of 3 % which I doubt very much since our tests show over 20 % savings that would mean for our Fastcat 455 that would gain 360 lbs in weight and would loose 5 % in strenght.
No Way And on top of that Styrene smell for almost the life of the cat
Greetings
Gideon

[BigCat]

Hi, Gideon

I'm not trying to change how you do things, but it would be either stronger or lighter with epoxy, unless you split the difference and made it 1.5% weaker and 1.5% heavier. However, according to the article above, it is epoxy /carbon that is slightly stronger, not epoxy glass. You can get great savings in weight with epoxy / carbon prepreg, though, because you have no resin in channels.

One must discuss actual products rather than types, though, if precision is required, as individual examples vary so widely in specifications. You can get VE resins with elongations of up to 15%, though I haven't heard of anyone using it to make yachts.

You have not acknowledged the point, which I proved with a reference, that class 1 flame spread resistance as found in flame resistant VE is a flame spread rather than an ignition standard. You stated the contrary quite flatly, and you were wrong. This isn't about one-upsmanship, this is a critical safety issue, as your informal test of one of your laminate panels should have made very clear.

[fastcat435]

Hallo Big cat we use glasss only in non structural areas of the cat
|Most fiber is basalt and carbon and on the inner hull we use twaron/kevlar for impacrt resistancy
Our tests have shown weight a decrease of 18 to 20 % in our hull and bulkhead laminate what you should do for yourself is infuse a couple of panels
in the identical layup in your choice of vinylester and in epoxy both thru resin infusion
with their respective vacuum levels and weight the panels , test the panels until destruction with the bullet test.( a one kilo steel ball drop one meter on each of the panels and measure the impact it leaves behind.
Also cut 200 mm wide strips of each panel one meter long and put ballast on them and see how much weight one and the other will take. after these tests make the choice for what resin to use.
We have done all this and many more tests and you know the result
All your wisdom comes from others and there is nothing wrong with that but the proof of the pudding is in the eating ( an American expression I believe ?) We have eaten and have choosen epoxy because it beats every other resin tried in every way maybe with exceptance of the fire resistance but we use something else for that
Again greetings

Gideon

[BigCat]

Hi, Gideon

I didn't know that your boats were mostly exotic fibers-no wonder they are so light. My knowledge of modern methods is from others. I have done traditional hand layup in the 'old fashioned' way with poly / mat / rovings.

I presume, however, that the Swedish Navy and those who specified and made Mirabella V have also got experience of modern methods, and they came to different conclusions than you have. Ron Holland / High Modulus / Vosper Thornycroft, who produced Mirabella V, can scarcely be dismissed as amateurs.

Scott Bader, which supplies your VE, does not supply it to the US, so I didn't pursue the question of its properties with them.

I note that, once again, you duck the question of flammability. Your post about your test of a panel of yours was really quite alarming. The basalt will help with burn through, but I don't see how it could help much with flame spread.

[neelie]

After having vowed never to touch a cored hull, I find myself now looking at 6 - 10 year Cats - all of whom have cored hulls.

I have some questions for the core guru's

What is the expected life span of a cored hull which has been well used and has lived its live in the tropics?

Does the diurnal temperature cycle have an effect on its life?

Is it fair to say that quality control during the build process is critical to the lifespan expectation of a cored hull?

How can one determine 5 years on whether the requisite care was used during lay up?

Does the existence of de-lamination mean it will be a total write-off?

[ssullivan]

Originally Posted by neelie

Does the existence of de-lamination mean it will be a total write-off?

I'm not an expert on coring like these guys... but I wanted to chime in about this.

I just looked at many cats in S FL last month. I saw a good deal of them in the year range you are mentioning and you know what? Many of them were delaminating. I didn't buy any of the delaminated cats I saw... I ended up buying a solid core, which of course is costing me in hull speed, but I sleep well at night knowing there are no structural problems.

Be very careful of the years you are looking at. I found most 10 yr old cats I looked at to be falling apart - badly.

If you pick up a delaminated one, be sure to factor those costs in when coming up with the total price... time too.

Not trying to get into any debate, just reporting on what was out there for sale in S FL last month.

[BigCat]

This would be a question for a surveyor. Read Kanter's "Cruising Catamaran Communique," and ask his opinion if you don't feel that you have found your answer in his book-he is a surveyor. It seems to me that if all 10 year old boats were badly delaminated, he'd have mentioned it in his book. Maybe the delaminated boats linger much on the market, and so are over represented in the 'population' of boats for sale. One would think it likely-

Just because you can make a cored hull doesn't mean you know how it will stand up 10 years later. Most boats, even most cored boats, are made in molds. There is an intrinsic problem with coring a boat in a mold, and that is that you are trying to get flat little squares to smoosh down hard against a curved surface that you can't see while you work.

This is one of the reasons why I am making my boat's cored panels on a flat table-flat little rectangles lay quite nicely against a flat table, and gravity is your friend instead of your enemy. I would expect a boat made with this method to have an easier time of holding together, because I would expect a 100% join of core to skin. The really curvy bits of my hull are in my bilge, and they are to be solid laminate, so no core bonding problems there.

[ssullivan]

Originally Posted by BigCat

It seems to me that if all 10 year old boats were badly delaminated, he'd have mentioned it in his book. Maybe the delaminated boats linger much on the market, and so are over represented in the 'population' of boats for sale. One would think it likely-

I assumed as much. If your boat was delaminating, you might be more inclined to put in on the market to get rid of the headache. Makes sense.

Of course, not all 10 year old boats are delaminating. I was careful not to say that, too so as not to provoke anything on this thread.

What I really did see that shocked me though, was that several boats that were only 10 years old were falling apart so badly. Now I was looking at cats, not monos, but I'm sure the issue isn't one of boat type.

A lot of it was probably due to wet cores delaminating - owner error. But still. I was having a hard time fathoming how someone only 10 years ago probably paid $300K for the boats I was looking at only to have them reduced to garbage in 10 years. Scary thought to me... the guy looking at buying boats at the time.

[cat man do]

What I believe a lot of DE lamination problems arise from is the Adhesive/resin usesd for balsa core.

There is only one resin to use in my opinion for a timber core and that is epoxy.

Dave

[BigCat]

Calling balsa 'timber' in this context is very misleading. Almost all boats built with solid polyester hulls over the last 45 years have balsa core decks and very few of them have problems. A boat I finished out 35 years ago with a balsa core deck and polyester is still going strong, 50,000 miles later. So your flat statement is flatly wrong. If I were making a cold molded boat, or a cedar core boat, I'd use epoxy, but balsa doesn't need epoxy.

[cat man do]

So............................balsa isnt timber?

Dave

[BigCat]

"So............................balsa isnt (sic)timber?" Well, if all timber has the same properties, then perhaps you should core your boat with lignumvitae..........

[cat man do]

It is only that you are using end grain balsa and it drinks the resin that you can get away with using inferior resins (for Timber)to some extent.

If you were to use long grain balsa with your Poly and Vinyl, it would be as useless as they are on any other timber.

I could use End Grain WRC or Kiri and have results similar to balsa, but I would rather not comprimise the build strength and weight by using resins that arent deigned as a timber adhesive just to save a few dollars.

Longtitudanal timbers IMHO are far stronger and require less laminate thickness than end grain balsa and Poly/vinyl could ever achieve given the same laminate.



Dave

[BigCat]

Catmando, you are not shy with your opinions, but you are very sparing with your facts. Do you have any? You will note that I document a basis for opinions that I express. I note that you don't.

Alas, I must supply the USCG with actual facts and math, and telling them that something must be true because Catmando says so won't get me very far-

[Evan]

BigCat, where are you building your catamaran? Isn't real estate for that size boat in Seattle rather expensive? I noticed the USCG reference; are you building it for commercial charter operations? If so, you have my sympathy when dealing with USCG and cat design!