Box-beam or I-beam question

[Shield Arc]

For that kind of weight, at that span you and a buddy could easily carry an S-shape up ladders into place.

 

[BruceWard]

To me this type of wooden truss seems easier to manufacture

Open Web Floor Truss

 

[Aussiebushman]

Thanks guys advice much appreciated. I expected to get a few different views so apologies to those who feel their particular suggestion has been overlooked. You have all been very helpful and have provided ideas that together make up a solution that seems to meet most of the criteria:

• The steel web or pre-made trusses are tempting, but transport over 90 Km to the farm from the fabricators then lifting it on my own pretty well rules these options out

Laminating ply 12 deep X 6 wide with staggered joints is possible but hard to do it in situ and too heavy to lift on my own once assembled. The Micro-Lam option would be easier to build up a piece at a time but more costly than a box-beam.

• A box-beam structure is the easiest of the lot to build and certainly better than an I-beam because it doubles the shear panel
• By making the box structure of timber, then adding an internal web of steel plates to handle tension and compression loads it should be should more than adequate in strength and easier than getting the ply grain vertical
• A steel plate on top is a great idea to prevent wear from the traveller, but also to stop any lateral bending if the lift is slightly out of vertical

If I have got anything badly wrong, please yell. Otherwise, thanks again.

Alan

 

[LD1]

Yes, what you plan on doing will no doubt handle the load just fine. But I still think you are way over-complicating things. We are only talking a 135 pound steel beam to set and give you a saftey factor 3x's. If you cant set it yourself, you dont have even one person that can help you:confused2:

 

[tommu56]

Steel I beam a couple of comealongs and some rigging you should be able to get it up yourself

a pair of jacks and big pile of cribbing would get you their too

If you are like me I got more time than money I would invest in the steel.

tom

 

[o2batsea]

My thoughts:
Lifting; with the right rigging there is no reason why you as one person could not lift a steel beam into place. It may not go fast or be very pretty but a combination of lifting tackle or chain hoist each end, and leverage should be the ticket. You'll need a ladder at each end and a good supply of coffee or Red Bull.
I think you could also do it with two small bottle jacks. A jack post with holes for a cross brace every 6 inches? Keep moving the peg up one hole at a time as the end of the beam comes up....dunno...lotsa ways. Just wouldn't go too fast.

Wood beam; if you choose to build in place do a bit of prep work to the structural components to assure it will be a one time one shot deal. Pre assemble everything on the ground "dry" with no fasteners to be sure you have all the parts. Coat everything with at minimum two coats of thinned epoxy resin mix. This will encapsulate the wood against rot and insects and will give you a firm base for the next step which will utilize a thickened epoxy glue.
Assemble all the parts with epoxy thickened to peanut butter consistency with wood flour or fumed silica. Use removable stainless deck screws to hold the parts together for clamping force. Using stainless will allow you to leave the fasteners in there. With the frame built, install the sides with more thickened epoxy glue. The result will be a structure that is as strong as a solid beam without the weight. The epoxy encapsulation and glue is the trick

 

[Aussiebushman]

Yes "o2batsea" you are talking to the converted. I am also a boatbuilder so I'm working with epoxy all the time - in fact building a 22' strip/timber trimaran right now, which the reason the beam is needed - to lift the main hull off the trailer, then lower it onto old inner tubes where it can be rolled/turned to make the glassing and fairing easier, before lifting it back onto the trailer.

As well as coating the timber and ply with epoxy, the joints will be filleted with thickened epoxy. This is probably all overkill. I'm nearing seventy so the beam will outlast me by a considerable margin, even without the epoxy!

Alan

 

[TGF]

go steel.

 

[crazyal]

Sounds like maybe years ago steel would have been an option but if I was close to 70 I'm not sure if I would want to do some of the things I've done. If you are going wood have you thought about building it in place?

 

[chickenman]

it would help to see a pic or sketch of the installation