glassdave

iTrader: (1)

Thanks Steve, I will have our rep look into those.

Fredrik R

Great Steve,

The thing is that I only have the possibility of choosing the standard fibreglass/divinycell or full carbon option. I am a novice when it comes to different techniques of using carbon but I think that it is pretty advanced what they use. Below you find some pics from previous boats under construction.

http://unomarine.no/b_ter_under_bygging/g_36_nr_11/

The one in the pictures were just test driven (2x Mercs 525 EFi) and made 100+. Wonder what to expect with 2x725 Ilmors?

One of the reasons why tailoring is not an option at the moment is that Goldfish recently received a huge order from NATO and have their hands full.. Those boats will not use Ilmors but 2x Yanmar 380 DMAX diesels instead..

//FR

Steve 1

Sir they do a nice job and it looks to be a great boat,but what I was saying is with carbon there is no margin of safety with that material ,so you have to look at the worst case loading and provide for that, the analogy is easy one guy is using window glass and another is using lexan, The glass appears stronger until the loading deflects it a little,While the lexan absorbed/stored the energy but did not fail. Carbon has a very small elongation (stretch)then failure while "S" Glass has over 3 times the elongation before failure.

Here is some simple impact testing on Core: http://www.youtube.com/watch?v=DRzyw0Jo8Zg

Again we chose the one that gives the greatest margin of safety.

hallj

Have you guys used a polypropylene honeycomb before?

http://www.plascore.com/product-hone...moplasticcores

Do think it would be good for marine use?

Jeff

Fredrik R

Very interesting.. Can tell that you´re one of the authorities in this field for sure. Really grateful for your input! Just to get myself some education - fibreglass is heavier but will flex three times more than lexan (carbon?) which gives the carbon more of a snap-effect once instant maximum load i given.. fibreglass/divinycell is therefore the safer alternative and should be my choice despite heavier? That would also save me over 80 grand.. So why even consider carbon according to you?

With the ilmors, how much do you think close to 600 pounds more (fiberglass/divinycell) will slow her down compared to carbon? Is a little childish but I would badly want her to cross the 100 knots (115 mph) barrier.. But if the standard choice is significantly safer I will go with that option.

//FR

Fredrik R

Sorry - Lexan was from your example, not on the boat. My misstake!

Steve 1

In some areas but not the hull or internal structure,Remember like in the case of a bulkhead or stringer how the loading is imposed from the edge while the foam core has omnidirectional Physicals and not just one direction.

Steve 1

No if the Carbon gets loaded and is stretched 1.6-1.7 % It fails now "S" glass is nearly as stiff but can be stretched 5.3% before failure that is why the Military loves the stuff.

hallj

Makes sense. If one was looking to shed weight in the laminate,
would it make sense to use Kevlar on the inner part of the laminate and S-glass on the outer?

Jeff

Steve 1

I would bag everything and use unidirectional "S" glass for a tight laminate as you can see I use foam core and have built VERY Light with this system.

usually I do not recommend Kevlar for a layup but rather in specific areas where it's tensile strength is needed (around a bulkhead cutout) ,the main problem with the material is very unbalanced and has next to nothing for compressive strength, Like trying to push with a nylon rope so you must add that side with glass or carbon.