[TheForge] Wooden Beam strength for Rigging

[terry l. ridder]

hello;

comments intermixed below.

On Mon, 30 Jan 2006, Woolley wrote:

> Walt,
>
> I'm saying beams or roof joists. They support a flat roof that sits
> right on top of them.  The span is 25' with a 6" slope over the 25' span.
>

that slope is going to take a good amount to wind stress.
the slope works out to approximately 1/4:12. i.e. the roof rises
0.24 inches per 12 inches of horizontal run.

are the individual rafters one piece or are they spliced? 
if they are spliced how are they spliced?
do you know how the rafters are attached to the walls?

are there any support columns in the 25ft span?
are the dimensions that you give of 3x11.5 inches close?
the reason i ask is that a 4x12 would actually be 3.5 by 11.25 inches.
i assume the rafters are pine.

>
> Most are in pretty good shape.  A few have some splitting and twisting
> but not much that really concerns me. I'm thinking 6" beam just for ease
> of installation and I really don't need to be able to lift alot of weight.
> Like I said, 1/2 ton max. but I didn't look into whether or not a 6"
> beam would give that to me. 
> I'm just throwing that out there as a starting point. I'd like to place
> them at 1/3 and 2/3 of total span.  Maybe bridging the two now and again
> to support something placed on or over the table which will be in the
> middle of the span. I could easily leave at least 6" of wood under any
> holes I would make for the hangers. What are fletch plates?  Thanks.
>

fletch plates, are normally made from 1/2 inch steel plate and then
sandwiched between two 2x12. they are used provide a strong load
bearing joist.

>
> BTW I poured a footing for a gantry crane elsewhere in the shop.
>

i would still go with a rolling gantry crane instead of using the roof
rafters.

>
> Regards,
> Bill Woolley
>

-- 
terry l. ridder ><>