Cost of Carbon Vs. Fiberglas

Hello out their. We are wondering if anybody could tell us the cost difference between building a boat out of Carbon versus one of glass? We are estimating 3x the cost is this realistic? And does anybody know of any good books on the subject of building out of composites such as Kevlar?

 

You cannot calculate on such a rough basis (guesses).

Only the hull will cost more, and the hull is just a fraction of the total cost.

 

I guess i should of been more specific, I am talking about the cost to build any component in Carbon as opposed to glass. Their must be a rough rule of thumb as to the cost difference between the two. Before we build we will price all components but wanted to see if it was worth our time or just to much for us to consider.

 

Me too.

What is made from glass? Hull and deck.

And no, there is no rule of thumb as far as I am aware of them.

 

It depends on what you are building. For example, a average solid hull built with carbon fiber would be really expensive. A mast, which is a relatively thin section, doesn't have as much of a difference. You have to do a structural design before you can figure out the price.

 

Ok, let me simplify my question then i suppose i might be being to broad. What is the average cost difference per square meter of fiber vs. cloth of the same weight/strength?

 

Strength is usually not the selection criteria here. The main benefit of using CF is the stiffness. You can get it with an elastic modulus up to 10 times that of glass and it has lower density. It means that if you need a very stiff structure or panel you do not need much of it.

A high modulus CF tube will have about 1/4 of weight of steel for the same stiffness. If you compare a fibreglass panel of the same weight to a CF panel the fibreglass will feel like rubber by comparison. The FG compliance might be beneficial in load absorbing in certain applications.

If you are building a performance machine then the value CF brings will provide the winning margin over glass if you use it in an effective way.

There are practical limits using it though because you can end up with such thin laminations that they become prone to localised damage through normal handling. This can greatly weaken the panel or structure. So in a way it is more delicate than FG.

You find a lot of CF products have see-through finishes to make sure people know you have a CF component or whatever. It is a current selling feature but sometimes without technical merit.

If you shop around you should be able to find cloth that is the order of 5 times the cost for the weight compared with glass cloth. If stiffness is the primary criteria then it would work out roughly the same price but the CF would result in a much lighter element.

One reason it is not used more widely is the inability for fast moulding. I understand BMW have started making car roof panels from it but the production rate is very slow compared with steel pressings.

I posted some photos here comparing panel stiffness:
http://www.boatdesign.net/forums/materials/carbon-fibre-fiber-investment-25081.html#post239629
That compares the deflection of two test panels of the same size and weight under the same load. Each panel has 3mm thick klegecell foam backed with 200gsm glass or CF.

It is incredible material but a waste of money unless you purpose design for its use. There is also the fashion value if you are aiming to market something.

Rick W

 

And please also define "glass". Does this mean spray-up polyester? Of which the cost is approx euro 6 - 8 / kg (including labour, gelcoat and everything)

Or hand rolled fine glass cloth, wet bagged with epoxy?

It is so difficult to compare, if you do not know what to compare?

Indeed lamination of carbon is usually a bit slower then comparable glass cloth. Definately if the carbon product should look nice.
But also a bit of engineering and purchasing can help. (thicker carbon cloth or non-crimp fabrics, reduction of layers)

 

2x2 CF twill 6 ounce is about $30 a yard retail. A regular weave of 6 ounce (90/90) 'glass cloth is about $6 per yard retail.

This isn't much help actually, but does offer a 5:1 price point to work with.

 

dont forget pre preg is very fast to work with for mouldings so major labour savings over hand or infusion work

 

And do´nt forget the extra ten thousands of $$$ you need to setup your workshop for prepreg! Let alone the much higher cost, which will pay back only when you produce on industrial level!

 

Yes, very true Apex1

 

If you look around, some suppliers will have information on how to use their stuff,you might get answers there. With glass, you can use polyester resin, which is cheap but has drawbacks. With Kevlar and carbon fiber, you should use epoxy, which is expensive and has drawbacks. It's not fair to compare the cost pound for pound or size by size, as one set of materials will use more or less materials to accomplish the same "strength". And the different materials will give different types of "strength", flexible, stiff, puncture resistance, etc. so you need to define that, which for the console it would seem to be stiffness. But you also need to be able to machine it when done, cut, drill holes, and that might make some difference in what you use. Cut and drill Kevlar and it's fuzzy, I don't know about carbon fiber. I don't think you can use gelcoat with epoxy, so you would have to paint them as epoxy is not uv resistant. That's not much of a problem until you sand a little Kevlar and it's all fuzzy.

Here's a canoe/kayak forum that might give some info. It seems S-glass and vinylester resin is popular with them.

http://www.paddling.net/message/showThread.html?fid=advice&tid=1215485#1215536

 

Thanks guys, i will withdraw this question and find the answer on my own by creating a layup in glass and having a Kevlar guy help me determine the similar layup for strength.

 

first question -what kind of boat and what size are you going to build ?
second question -what are you trying to achive at the end of the day ?
Third question -what are you going to use the boat for ?