Choice of MAT vs Woven Roving

I receive the price for fiberglass and poly resin from my supplier and I have a question!!!

Price are in Canadian $

Polyester resin is sell at $4.22/Kg

Mat 1.5 is sell at $4,85/Kg. So at 28% fiber, 1 m2 of laminate of 1mm thickness cost $5.89

Roving 24 is sell at $5.00/Kg, So at 38% fiber, 1 m2 at 1mm tickness cost $9.20

I know that Roving is stronger (about 50% more at 0-90 degres, only 10% more at 45 degres (Hankinson p.87)).

If we forget the weight, we can compare 10 mm of roving cost $92.00 / m2
at a 15 mm all Mat laminate. The cost is $88.35. Also the thicker Mat laminate is more stong in fact of is greather tickness. A 13 mm laminate of Mat have probably (means of all direction) the same force that the 10 mm Roving and cost $75.57. About the weight, 13 mm of mat weigh 17.68 Kg and 10 mm of roving weigh 15.85 Kg a difference of 11.5%

What is wrong?

 

It is a not a choice of either or you must use csm between layers of roving. CSM< WR>CSM>WR> CSM ETC>

 

If you continue with your sandwich project, I think you can use only bidirectional roving.
What happend to the cedar strip planking?

 

LLoyds will OK an all matt boat.

It will be heavier than a combo mat & roving boat.

You only need 3/4 oz matt between layers of roving for best streingth and lowest weight.

FAST FRED

 

If I understand, the choice of all mat boat is correct but it is a economical choice. this boat have higher weight and less performance.