Accepted thickesses of E glass laminates

Hello all,

I am fiddling around with laminates for chainplates for my little folding cat. I have built more than a few on the looks good enough method and some extra reading but I want to ask about packing.

What are some accepted values for packing marine laminates so that we can use the values in tables. A case in point - According to Greene (Composites design book) E glass laminates have a breaking strain of 292MPa. A MPa is a megapascal. A Pascal is a newton per metre squared. So I want to know how much glass laminate the guys who made the test laminate can fit in to a certain thickness.

A cat designer says with his chainplates that you make them up to a certain thickness with unis. This seems back to front. Should you not work out the amount of glass required to take the load from the allowable stress and then work out how this equates to a normal laminate?

I am guessing, I have had more than few looks, that I can get a 600gm uni laminate down to 1mm. Do the guys who make the test laminates use pulltruded, vacuum bagged etc laminates that can get more fibres into a certain thickness?

I have samples I can use to check my own end but I really want to know if there is an accepted standard for packing test laminates.

cheers all

Phil Thompson

 

Phil, I think that your correct in that the amount of glass should be specified for chainplates etc in regards to load & safety margins, we faced a similar quandry when laying up connective bulkheads that included a specific cross section of uni fibre but no figures for actual fiber content- we just packed in as much as we could but its a lot better as a builder to have say x number of uni tapes at whatever weight so you can simply follow the schedule & know its sweet. As for test panels/samples its reaonably assumed that they exceed the quality of whats acheivable in the workshop/boat, usually being done downhand in small scale & relative comfort with a higher labour content per meter square & care in resin to glass ratio etc, if you can work out & test your own acheivable values & specify the number of plys with some nice fat safety margins that would be good & also stagger & fan your tapes deep into the hull & onto a bulkhead that would be good too & also wrap the tapes over a nice spool to interface the attachment of turnbuckles & if you cant fit your fiber over the spool diameter a simple split & matched mold clamped over might squeeze it up for you but test it. As for an accepted standard thats acheivable by a reasonably proficient laminator the 1:1 resin to glass by weight is alright for stitched/uni & 2.5:1 for chop(not that good for chain plates but you might want to tidy & protect the uni with some internally) of coarse its possible to get better fiber ratios but you gotta be real on effort, these composite chainplates & stanchions that we're seeing have some obvious benifits but installation time isn't one of them over a stainless steel alternative. All the best with it from Jeff.