General laminate question and Happy New Year to all !

[bulk-head]

Looks like a bunch of guys around this site that know how to work glass. Ive got a question about stitch and glue construction and general laminate schedules. Seems that every plywood core hull calls for a biax tape lamination schedule along the chines and keel BEFORE the structural skin is applied. I understand the need for reinforcement in these areas, but why inside the laminate ? as opposed to on the outside ? The way in which the clew of a sail is built up. Seems to me that when fairing the hull, with the main structural skin ON TOP, outside, of the reinforced area, that there is a real danger of a little aggressive board sanding or a run away DA promptly sanding thru the ridge formed by the underlying layers of fabric, breaking thru the main structural fibres ? With the Biax tape reinforcement on the outside of the main skin, the long fibres would be hidden, protected... touching glass when fairing would simply bevel the reinforcement tape . What gives guys ? Is there an engineering reason for the reinforcements to be on the inside of the laminate.

[fleetwing]

the answer to your question is: the added reinforcement, provides elasticity at the joints for the plywood, and adds strength, at the high pressures of the hull along the chine, and hard areas of the hull, to help in the resistance of pounding that occurs, Look carefully at the structural strength of the lamination schedule, and calculate the strength, from the tensile strength of the material, (fiber glass ) The P.S.I until material failure, which causes hairline cracks, and de-lamination, the optimal load for any boat should be 70 P.S.I overall compound this figure with the lamination.

Most of all the reason for biaxel tape is "for the builder", because the lay up dimes may be different and the tape will fill the gaps, and keep everything in place.
your point about the Sanding and faring is this : have at least 3mm of gelcoat and you wont have to worry about print-thru. there are simple rules to eliminate this yor lamination should start with a gelcoat, then 4 oz woven, 4oz. matt, 6oz woven, 8 oz matt, this is basic, thinner lamination is sacrificial, and cosmetic.

[Roly]

All my laminating I've done with the high stress area reinforcement on top and feathered with staggered width tapes to avoid a hard spot. (Not by sanding thru the main laminate) Then fairing bog.
As you say,Bulkhead, its common sense.
Then, I taught myself, which is pretty common!