Building a small work barge with plywood

OK

a question.

We're to the point of laying out the deck. The #5000 crane mounting is in question. We were looking at a center mount 8 feet back from the bow. the max lift point is 3 feet from center for #5000. We had elimated the center lifting hole on the barge for no real reason. maybe need to put it back. I thought an offset set mounting point might work. The optimum would be 4 feet from a bow corrner. Maybe 4 feet from the side and 6 feet back from the box too.


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Maybe a simple set of sheerlegs could work for you- you can set them for use over the bow or rake them aft over a hole at the centoid of waterplane for extra heavy lifts- teamed with a pair of wire storing winches this will give reliability & versatility. Regards from Jeff.

 

Found this info on plywood

 

Question

Is there a way to figuire out how far down the bow of the barge will sink if i am lifting #4000 over the bow given its size and some counter weight at the stern namely the engine and drive? If so how about over the side.

I attached the most recent drawing of the rig. I think

 

Well the plywood is here. 54 sheets of ac. We went with a product called auroco ply. Its a pine product from south america and at first glance it looks nice. Im going to do a boil test just for the heck of it. the sanded side is real nice and c side is the best ive seen. Hopefully the voids are few and far between. Set up the table saw and start rippng sheets in half.

 

Plywood bending question. For the bow chic wants to have a curved bow vs a flat angled bow. The radius of the bend will be 3 feet. How deep and close together should the kerf cuts be in the 3/4 plywood. They will be filled with epoxy and a layer of glass on both sides.

 

Rip a test strip 6" wide and try what looks right. It it doesn't work adjust and test again.

 

The crane mounting needs to be addressed. If this were a steel barge, no brainer. Bur given its wood, the stresses are worrying me. We had initially thought of creating an internal structure of angle of box beam to to be connected to the internal bulkheads to spread the load. But the more i look at the crane we have it looks daunting. Im afraid it could tear it apart if we have the boom out and lifting 4000#

All thoughts or ideas weclome.The pictures show the layour of the frames.

 

crane mounting

For the crane installation, one method suggested is to construct the steel subframe inside the hulla and mount the crane on deck with the plywood deck sanwiched inbetween. I am concerned about what that will do to the plywood after the deck is repeadly compressed around the base area when using the crane.

Another idea is to build the same sub frame inside the barge and then have 4 verticle steel members protrude through the deck and the have the crane base mount to that. The protrusions could be sealed with silicone or sikaflex or something good. Any movement might be taken up with the flexible sealant. The subframe is probably going to be construced out of 3 x 3 x 3/8 angle. That is what it was monted with when it was on the truck.

And a third method was to construct the frame base and mount it on deck with hard points built into the barge framework ot bolt to. We were trying to keep the deck as clear as possible so that method is not as pleasing to us.

Any ideas

 

That one would be my pick. Compressed plywood for that kind of weight doesnt appeal - plus you get something to weld other gear onto if required ( flanges for shackles etc )

 

No matter where you mount the crane you still have to transfer the crane load into the wooden structure. I assume this will be done with bolts. You need sufficient bolt area so there is no movement in the wood. It would be best if these bolts are horizontal into the plywood sheer webs (full height) so that the bolts are loading the ply endgrain and not crushing side grain.

 

Lots of smaller bolts works better than a few large bolts when you are trying to transfer the load to something soft (wood).

C.O.

 

Well......perhaps when you are working with "blind stab" engineering. But I would advocate a slightly more intensive engineering effort were the loads (and their directions) are calculated, a safety factor is added, and fasteners are specified to suit......

Wood is not homogeneous or isotropic (as say steel is), it is hetrogenous and orthotropic. That is, it's composition and mechanical properties are dependent on grain direction. Any fastening has to take the grain direction into account. Thus orienting plywood in double diagonal layers at say +/- 30 degrees to the load will work better than leaving it at 0/90 degrees......

 

Well it has begun. Laying up all the internal components. Already had one casualty. The tip of one of my fingers. Gone. oh well. But the layups are going well.

 

Try a bit of epoxy and sawdust on the raw bone - then you will be bionic man "we have the technology"

But seriously, I hope it wasnt too painfull - was it a circular saw ? They are the worst culprits.