scantlings for a fiberglass cored molded 28 cat?

Richard, DBM1708 is a 17oz/yd2 double bias with a 3/4oz/ft2 mat, so about 24oz/yd2 total fabric weight.one of the most common structural fabrics used in the US.

Steve.

 

Steve,
Double bias ? So +45 -45
Or Biaxial 0-90 ?

 

RR, yes, the DB means that the fibers are laid on the bias meaning +45 -45, the M is for the mat that is stitched to one side. Biaxial means 0 - 90 as you say.

Steve.

 

Hmm, ok for a strip planked hull but for foam or balsa core Biaxial running fore and aft would be preferable. Imho of course.

 

The problem with all the anything other than uni imho is that with just one layer you don't get continuity of fiber in one direction so two opposing plies of uni would be preferable to one ply of DB or biax. That said i built a 24ft bulb keel monohull of my own design with just a single ply of 12oz DB each side of a 1/2" H80 klegecell core as the overall laminate with of course additional glass where needed, it has been structurally trouble free for 26 years and will be going back in the water within the next few days boats are in general very lightly loaded structures and can have quite light overall laminates as long as you properly identify and reinforce the areas that are loaded.

Steve.

 

Agree, the weak link in small boats is impact resistance, meet that and the structural loads can be well covered.
The other issue is having enough labor on hand to do a wet on wet layup, not an issue with infusion I guess.
A subject worth its own thread perhaps ?

 

3/8 balsa would be more than strong enough. Most boats that size would be 9mm foam with less than half that thickness of laminate. Sounds literally bullet proof to me.

My floats on my 28ft tri are 4mm ply with a light cloth on the outside only with virtually no structure inside.

 

If you use balsa use the light version which is very close to the weight of h80 foam which is typical in boat construction, I agree,that would be a heavy laminate if its a performance cat.

Steve.