One of the biggest problems is that most jobs turn out bad because the wrong materials are used. We can’t really expect to get a good job done with rough boat repair or a car repair kit.
From the aerospace industry we could take over some very suitable materials.
One could split the materials into, reinforcing materials, fillers, resins and
release agents. I’ll go through one by one. For some of you it might be nothing new.
I’ll just start with the reinforcing materials for now. Glass/ Carbon/ Aramid fibres.
When it comes to woven materials one big difference is the type of weave. We mostly are able to pick up plain weave glass fibre somewhere, problem is this stuff is not nice to work with, it will not drape around corners and fold up badly. Secondly some nasty glass sold in boat shops are very stiff because of a finish applied to hold the fibres in place, this finish breaks down with the styrene of polyester but not with epoxy resins.
Since we need very little reinforcement fibres, we might as well use the right ones.
They don’t have a shelf-life and left-overs can be used years later.
Twill or Koeper woven reinforcement materials are very nice to work with, they drape around corners really well. Atlas woven material is going a bit over the top but is also nice to work with.
Twill compared to plain is: stiffer, stronger, nicer to work with.
From the pictures:
Roving: is like a bundle of hair, can be laminated with resin exactly where strength is needed. Like wood fibres, except one can control the direction. Strength and stiffness is of course only in one direction. Great for laying in corners or repairing for example a cracked wooden stock inlet. (comes on a roll)
Unidirectional tape: is like a couple rovings held together in one direction. Very good to get up down strength and stiffness into an forend. Very little torsion strength. (comes on a roll in different widths)
Strand: really nice to work with, mostly very little cutting needed. The width can be adjusted a bit by pulling or compressing . The angle of weave perfect to give a very torsion stiff laminate. Very good in conjunction with unidirectional.
If one only wants to buy one fibre too stiffen a forend, a roll of this kind of strand would do. (comes on a roll in different widths)
Hose 45 deg: a bit special: I’ve used it before to stiffen the outside of a forend. It’s a tube of fibre which tightens up or tightens around something when pulled at the ends. Good torsion stiffness.
Fabrics: are sold by the square meter, either folded or on a around meter wide roll. Sometimes awkward to cut small pieces, and even more awkward if one wants the fibres to run under 45deg because of the wastage.
160g/m2 Atlas hollow fibre. Something very new, the hollow fibre can only be done with glass. Expensive but good vibration dampening, good strength, insulates a bit.
Except for the hollow fibre all these can be had either in carbon, glass or aramid (Kevlar)
Carbon: is the stiffest by far, strongest in tensile and compression, light weight. Nice to work with, easy to cut as a fibre and easy to sand as a laminate. (expensive)
Aramid: only advantage would be in a crash situation, holds together after broken. Not nice to work with. Not good on compression. Not nice to sand once laminated. (Stay away) (expensive)
Glass: very good all-round. Performance can be very good with high quality glass and good laminating resin. (Relatively cheap)
Weight or thickness. For small repairs and forend stiffening glass at 100 – 300 g/m2 . Carbon max 160g/m2. The thicker or heavier the more difficult to work with.
Rather 2-3 thinner layers than one thick one.
edi