Phill is right about the +-45, and on top it is a dream to work.
The question is, do you really need an overlap? If not there is a nice way to deal with the problem. You just let the two layers overlap, wet them out and then with a very sharp knife you cut trough the two layers. take of the exess on top and carefully lift the toplayer and remove the exess on the underside.
It takes some practise and a very sharp knife

Interesting idea.

Phill,

great tip about how to make invisible overlaps, thanks! (I think you have mentioned it before, but now I'll remember it).

My source for the carbon comment is Bjørn Thomasson in Sweden (http://www.thomassondesign.com), the kayak/canoe designer/builder. According to him the density of the carbon fibres in the weave is larger than glass fibres. To get a good matrix around the fibres you would need more epoxy, especially if laid up by hand. With vacuum you come closer to the same amount of epoxy as you would use for the same weight of glass. With a lighter carbon cloth I suppose there are some gains, but it looks like there is a crossing point for carbon vs. glass for this application. It would be good to know if he (I) am wrong or even completely wrong.

I know the hull will be stiffer (as in less deflection) with a +-45 layup outside the core. But I was intrigued to hear that the panel integrity also will be better. Thinking about it, it becomes quite attractive to put the cloth on with overlaps due to the points you made.

Rolf,
Also if you lay the glass gunwale to keel and then keel to gunwale and then gunwale to keel you end up with almost no waste and significantly less waste than running it length ways.

I have found similar data suggesting that in order to achieve a significant weight savings with Carbon you would need to go to cloth weight that is the THINNER than the glass weight you originally specced. With these lightweight laminates you need to control resin weight which is partially done by keeping the fiber thickness to a minimum (thicker fibers need a thicker coat of resin to wet out). This would provide a laminate that is slightly stiffer and about the same weight.

Couple of thoughts I have had: have you considered using slightly thicker strips?? 5mm or even 6mm?? Remember stiffness goes up exponentially with the thickness of the panel. One of the reasons a Marstrom T is so stiff is that they use a 10mm core thickness. I would consider: 6mm thick strips with 200 gsm S-glass on the outside layed with the fibers at +45/-45 and then a lighter 100-130 gsm inside laminate of either Kevlar or tightweave glass (4-Harness or 8-Harness). I think you could get close to the minimum weight, gaining maybe 4 lbs. per hull doing this. You could even try to make up for it by making carbon rudder stocks and carbon beams.

keep us posted!!

Rolf,

Check this site. they have done several panel tests relevant to what you are doing. (it is in english units, as a quick reference, 200gsm cloth is about 6oz) Again, good luck!!

http://www.thag-o-mizer.net/index.html

Hi Rolf

So, have you done the working out for strip planking or has Phill made alternate plans for you. I only ask as I wouldn't mind trying it out myself, I have access to ply, but have wanted to do some strip planking for a long time.

Regards

Matt,
I hope Rolf does not mind me answering this question.
I prepared something specific for Rolf.

Regards,
Phill

Not at all Phill, I hoped you would reply.

Hi Matt,

didn't think you had that much of a death wish.

"I wouldn't mind trying it out myself, I have access to ply, but have wanted to do some strip planking for a long time."

Do you ever want to get out of your shed again .

Strip planking sounds nice and soft and fuzzy. But it is the method of the DEVIL . To much trying to deal with soft timber and hard glue lines and the fairing NEVER ENDS .

ARGH! I am having flash backs, got to go sailing to get rid of them .