mounting a deck crane on fibreglass deck

Hi there

I have a 42ft landing craft (fibreglass) (almost 13ft beam) which I want to add a telescopic 12v crane. The crane (weighs 300kg) will be lifting a maximum weight of 300kg although is rated for 1.5t @ 1m. The deck of the vessel is about 2.5 inch fibreglass with multiple support lattice (6inch X 6inch) supports beneath the entire deck.

I plan to mount the crane on 4inch steel I beams length of 3m running two parallel to each other and another two running across (effectively a large double beamed cross). The beams will be bolted in multiple locations to the deck with steel plates beneath. The beams will run most of the beam of the vessel.

With a vessel weight of appx 12 tonnes, does anyone see any major problems with this ?

thanks
mike

 

Although the texts are in Spanish, the attached figure maybe might help. Do not forget to place pillar/s or strong floor & girder

 

thanks,

don't know if this will work on the boat given its relatively small size. we are planning that the double cross 3m I steel I beams will spread the weight which combined with the beneath deck lattice support will suffice. the crane will not be extending loads more than 1m beyond the I beam supports.

 

My boat was a catamaran of 37 feet in length. 20000 kg/m2 deck cargo.
I believe that the metal beams are not necessary. Horizontal metal plates properly distribute the load on the cover and the torque can be compensated by these plates, and 4 vertical radial metal consoles. The struts, in my opinion, are always good.

 

thanks for this, wow 20tonne/m2!!

 

You need to be very careful with the load paths and then check the final deflections. Tansl's arrangement above may not be applicable for yours, since you have posted no other data to say one way or another.

 

Perhaps you can provide a sketch, super-imposed on a photo, of what you are trying to do.

 

mounting a deck crane

firstly thanks for your input, im adding a few pictures of the boat, the I beam frame that I propose to mount the crane on and a picture of the crane itself (not the actual crane but one from the net)

the crane is actually already mounted to a steel box frame about 2.5 ft in height and that will be bolted to the I beam frame.

The I beam frame covers the entire width of the available deck (3m).

I propose to mount the crane along the centre line of the boat deck slight to the stern of the mid point (if that makes sense!).

Should probably add the boat weights appx 12 tonne and the max load I would be lifting is 300kg (660lbs). the crane itself weighs in about 250kg and has a max boom length of 15 ft although I wouldn't be using the full length just enough to get over the side so in the region of 7ft from the crane base.

Appreciate your thoughts and thanks in advance.
mike

 

In addition to my comments above (only a structure dwg showing the scantlings can tell you if there is sufficient load paths/strength) you need to check the intact stability in all cases of possible loading.

 

Have you considered a gunwale mounting instead of just deck mounted. If the trim isn't effected by 300lb (unlikely with the beam) it's the best solution with composite hulls.
When presented with same issue - retrofit a towed sonar recovery crane on survey environmental response vessel I tested the trim with crane in place then fabricated a s/steel tower with flanges to mount to the deck and the gunwale thereby spreading the load.

 

Thanks Guys, all good advice. I had a marine architect come visit today as we don't have the blue prints of the boat. By chance, he knows the boat well and has advised we locate the main support beams running the length of the boat and attach the ibeams to these and the gunwale. ill post a picture of the work as its being done if anyone is interested. Thanks again, great forum this.

 

Photos of work in progress are always welcome for their educational value.