oldsaltoz
Well-Known Member
G'day trevera25,
Just to clarify things first, we are looking at a 25 foot motor cruiser built around 1975 and made of fibreglass. Please correct me if I have made any mistake.
You have removed a number of structural stringers as the timber inside had swelled and split the fibreglass, and you now wish to replace them.
You have also removed some or all of the internal trim and want to know if this forms part of the structural reinforcing of hull.
Stringers:
As has been stated the timber was used as a form only to provide a basic shape to lay the glass over to form the stringers. The timber (or other material) in boats of this vintage did not (in 99%) of boats provide any strength, but because a chopper gun was used to lay-up the glass, the thickness may be in some doubt.
You can build new stringers with almost any base material, DRY timber is the cheapest. If you treat the timber with a wood preserver then coat it with epoxy resin it should outlast both of us.
Some "closed Cell" foam is suspect and will take up moisture. Closed Cell balloons and epoxy resin do not absorb water and can be made to almost any profile.
You could even use PVC Conduit cut in half and glued into position with a fillet of micro fibres or micro balloons to avoid sharp changes in direction. Whatever you use remember to make a large radius on all external and internal corners or your glass will not be strong. Think of a Bell shape with a wider top and you will be close. You will need 8 layers of 256 gram cloth designed for use with epoxy, this will be stringer and lighter then normal wax resins, and provide a secondary chemical bonding, normal wax resin does not stick well to old wax resin.
As for removal of items like the galley of bunks you need to take a bit of care, as many bunk sides were made of marine ply and ran along (not across) the hull to provide extra stiffness. Dividers inside the bunks and lockers also helped stiffen and support the hull shape. So you need to look at what was removed and thick it was, if it's just a 3/8th layer of glass or 1/4 inch ply without a glass covering then it should be ok, but anything on the heavy side would have been for support or stiffening.
I hope this helps, keep us advised on your progress it's good to see the older boats still in action.
Avagoodweekend......
Just to clarify things first, we are looking at a 25 foot motor cruiser built around 1975 and made of fibreglass. Please correct me if I have made any mistake.
You have removed a number of structural stringers as the timber inside had swelled and split the fibreglass, and you now wish to replace them.
You have also removed some or all of the internal trim and want to know if this forms part of the structural reinforcing of hull.
Stringers:
As has been stated the timber was used as a form only to provide a basic shape to lay the glass over to form the stringers. The timber (or other material) in boats of this vintage did not (in 99%) of boats provide any strength, but because a chopper gun was used to lay-up the glass, the thickness may be in some doubt.
You can build new stringers with almost any base material, DRY timber is the cheapest. If you treat the timber with a wood preserver then coat it with epoxy resin it should outlast both of us.
Some "closed Cell" foam is suspect and will take up moisture. Closed Cell balloons and epoxy resin do not absorb water and can be made to almost any profile.
You could even use PVC Conduit cut in half and glued into position with a fillet of micro fibres or micro balloons to avoid sharp changes in direction. Whatever you use remember to make a large radius on all external and internal corners or your glass will not be strong. Think of a Bell shape with a wider top and you will be close. You will need 8 layers of 256 gram cloth designed for use with epoxy, this will be stringer and lighter then normal wax resins, and provide a secondary chemical bonding, normal wax resin does not stick well to old wax resin.
As for removal of items like the galley of bunks you need to take a bit of care, as many bunk sides were made of marine ply and ran along (not across) the hull to provide extra stiffness. Dividers inside the bunks and lockers also helped stiffen and support the hull shape. So you need to look at what was removed and thick it was, if it's just a 3/8th layer of glass or 1/4 inch ply without a glass covering then it should be ok, but anything on the heavy side would have been for support or stiffening.
I hope this helps, keep us advised on your progress it's good to see the older boats still in action.
Avagoodweekend......
