CS 17 foredeck beam question

[Jim Stumpf]

Is anyone laminating the foredeck beam or is a sawn frame strong enough. I am using structural grade southern yellow for the framing and stringers. (Sure it is a little heavy but it is readily available and strong)

Thanks in advance for any input.

Jim

[bagneaux]

I have some southern yellow pine available and some white oak. SYP is what is mostly available to me and is what I am making the king plank from. My lumber yard lets me pick out the clear boards, grin.

[PAR]

I used SYP for the beam, sawn to shape. I did expect them to be overly heavy, so I cut them deeper, then put lightening holes through them. You will also notice I eliminated the additional hatch framing, having the hatch opening land on the bulkhead and foredeck beams, further saving a bit of weight.

[Joe Anderson]

From a text on the mechanical properities of wood.

Douglas Fir has a specific gravity (weight relative to water) of 0.46-0.50 depending on where it was harvested.

Southern Yellow Pine (SYP) has a specific gravity of 0.43 - 0.59

Some species of SYP are a little weaker than Douglas Fir some are stronger.

As far as I know SYP and Douglas Fir are comparable in other important qualities such as resistance to rot and ability to bond with epoxy.

Most of the dimensional wood on my boat is Douglas Fir but there are several pieces sourced locally including some SYP.

[PAR]

SYP ranges 38 to 45 ( 41.5 lbs average) pounds a cubic foot, while Douglas fir is 31 to 37 (34 lbs. average) pounds, a considerable difference.

Douglas fir

Bending Strength                         12238 psi

Crushing Strength                           872 psi

Density                                     33 lbs/ft3

Hardness                                   616 lbs

Impact Strength                               36 inches

Maximum Crushing Strength              6951 psi

Shearing Strength                     1172 psi

Stiffness                                     1917 (1000) psi

Work to Maximum Load                     9 inch-lbs/in3

Specific Gravity                             0.43 (wet) 0.47 (dry)

SYP

Bending Strength                         14117 psi

Crushing Strength                             941 psi

Density                                         41 lbs/ft3

Hardness                                     942 lbs

Impact Strength                                 31 inches

Maximum Crushing Strength               8274 psi

Shearing Strength                       1633 psi

Stiffness                                       1971 (1000) psi

Work to Maximum Load                         9 inch-lbs/in3

Specific Gravity                               0.51 (wet) 0.55 (dry)

This is a quick reference of a few of the physical attributes between Douglas fir and SYP (longleaf). As you can see SYP is substantially heavier and stronger.