Thread: fibreglassing

For help with general fibreglass with epoxy have a look here.

http://www.storerboatplans.com/Faq/faqindex.html

There are lots of joining methods ... but how heavy is the glass you are using.

MIK

When the epoxy has gotten to the green stage of cure (no longer tacky, but still soft enough to press a finger nail into), lay a straight edge on the end of the fabric and cut off the loose fibers. Peel up these loose fibers, which will come off easily, leaving you a nice razored edge to butt your next fabric against.

Generally i would give the surface of the glass a good sand 50mm from the edge, then lay my next course of glass from the leading edge of the 50mm sanded area, effectively creating a 50mm overlap in the glass, once that has dried just sand it back to flush.

PAR's idea is good also, particually if your going for a clear finish.

That isn't my only method, but it's one that works well for novices.

I usually overlap, "green on green" then razor a clean line through both layers and remove the waste. This creates mirror joints with a common cut line that butts perfectly, though it requires a little practice to do it well and not make a mess of things.

Hej!

Is it better to "overlap and fair" for the structural integrity of the fibreglass

OR

to "butt" or "cut" which I thought would create a potential structural weak point at the join of the fibreglass?

The Black One

The way to do this is work in small arias at a time. Only mix the resin that you fell comfortable using a any one time don't be afraid to mix as many batches of resin as the job takes.The industry standard is to overlap the cloth by 16 mm at lest. Wen joining new to old you must set a scarf of at lest 40 ot 1 i will pm you my phone number if you like and can run you throw what you need to know.

Originally Posted by BlackF

Hej!

Is it better to "overlap and fair" for the structural integrity of the fibreglass

OR

to "butt" or "cut" which I thought would create a potential structural weak point at the join of the fibreglass?

The Black One

The inevitable answer is that it depends.

If the substrate being glassed is strong enough to take all the loads of the structure and the glass is adding abrasion resistance and some extra (non essential) strength then the butt is better. An example of this would be plywood.

But where the glass it providing longitudinal strength to the hull (for vertical joins) or preventing timber from splitting (usually horizontal joins) then both will have to have strength across the join.

The best thing is to ask the designer what is necessary.

Michael

Good catch Michael. I assumed the loads would be carried by the wood in his "timber boat", which seems to be an Australian phrase for wooden boats of all types.

Idle1, it would be helpful to know what boat you're building.

There are two types of attachments a sheathing can have, a chemical or a mechanical bond. A chemical bond is best and fairly easy to achieve. This requires you apply more fabric and goo, before the previous application is fully cured.We call this green on green and a few other things, some publishable.


Often you just can't avoid a mechanical bond. Time restraints are typical causes. With a mechanical bond, grinding back into the previous application is the usually choice.

On most wooden boats, the fabrics being applied are for abrasion protection and don't bear much of the stresses the hull endures. This isn't always the case and why Michael's advise about contacting the design is a wise route to follow. If this isn't possible, let us know the design and it's likely one of us is familiar with it.

You may have seen the progress on my boat under the Tom Cat title. What is the recommendationin this situation?

I've read you posts on the Tom Cat thread. At last I remember you where working on closing up the hull planking. I would have cut the centerboard slot after planking, with a plunge router and a straight bit, but if it worked out fine, then what's the difference.

Your work appears to be quite good. Is there a specific question you had about your project?

It will be a new deal for me to be glassing the strip built hull. The intention is to use biaxial glass for the job and was wondering how and where to commence. Should I lay it at right angles to the planking or at 45 degrees? should I start in the middle or at one end. Little questions but experience always helps with these little things.

For best strength (the reason we use biaxial fabrics) lay it parallel to the planking seams. This places both warp and weave across the grain and the longitudinal fiber orientation adds additional stiffness to the hull. Is there a reason you're using biax? Do the plans call for it? I ask, because it's a lot harder to fair biax then conventional cloth and it can't be finished "bright".

Thanks PAR....sorry for the delay. The strips are T&G Pawlonia which has a density somewhere between WRC and Balsa. The designer mentions biax in is commentary on the boat. I intend to epoxy and fair the boat prior to glassing to reduce the amount of fairing work after the event so hope this works.