putting a log loader on a barge

[Ad Hoc]

Yes, slewing is correct.
This 'new' arrangement has the hull split into 2, so it becomes a multihull, to overcome the stability issues.

As for the TPC, this is around 0.372, or for every tonne added, a sinkage of just over 1 inch.

[martinf]

How great is this, being able to wake up to the answer for the question that's been nagging at me for many months. Now I can proceed full speed. Ad Hoc, many, many thanks.

Originally Posted by Ad Hoc

Martinf
See attached. using the 1.5m hull separation, and accounting for box beams, approx 1tonne each, and maintaining the same height of crane, not the lower version.

Just wondering, were you calculating with two box beams (of 1 ton each) or more?

[Ad Hoc]

martin

I estimate each box to be 1 tonne (ton) each. One fwd and one aft.

Enjoy the backpacking...it sounds wonderful...I'm very envious. You have some seriously beautiful countryside your way.

[wardd]

can you bolt on removable pontoons/sponsons to the sides and with the crain they would be relatively easy to install and remove

[Village_Idiot]

I still recommend investigating a gantry-type crane. You said you had welding skills, you could weld one up without too much trouble. Basically you would have two or three upside-down V or U ( Λ ∩ ) supports that are attached either side to the split hull, with an I-beam running down the center of the upside-down U supports to carry the winch. Granted, you would have to ditch your log loader crane, but I think this would be better and much more stable in the long haul (albeit a little more work for loading/dragging logs around.

If the leg supports were done right, you could collapse the two hulls together for road transport, then space them out several meters for on-the-water operation. I've attached a crude drawing to illustrate my point.

[daiquiri]

HOLD ON GUYS, PLEASE!
Boy, you have gone pretty far with this job since yesterday afternoon!

Please read the correction to my post #17 and do not consider valid those graphs anymore.

The numbers that have been crunched since my last post (the one with stability curves) seemed way too optimistic to me, so this morning I've checked out if there was something wrong in my Freeship model.
And there was, indeed. What I thought Freeship was treating as a hull separation, in realty is the offset from the centreline! So the hull separation is really TWICE that number!
Please see the attached "Barge - Linesplan" files, either dxf or pdf, for the explanation of this important difference.

With this in mind, the road transportation becomes a problem.

Im sorry, I should have noted this during the construction of that model, but the pace of my job in these days is not allowing me to dedicate enough attention to this (and many other) things. That's why I had included the Freeship model of the barge, hoping that someone else would double-check it all.

My error, and I beg for your pardon. Especially to Ad Hoc, who has gone pretty far with calcs, based on my data.

So, back to the barge, the correct one. Please verify all the calcs independently before proceeding further and making any decision. You will find attached below all that you need to perform the verification.

The boat's displacement has grown quite a bit. We have 30 t (+/- something?) of the original boat, plus 1.5-2.0 t for box beams, plus, say 1 t for the deck between the hulls, plus 1.5 t for the crane.
The calcs have been made with 35.5 t of max displacement.

I'm including all the files that someone might need to cross-check the results.

[daiquiri]

With the last setup and weights, the moments acting on the barge are as indicated in the alleged pic.
The minimum Gz which can equilibrate them is 0.5, according to this model.
It becomes 0.7 if we take into account an overload (3000 kg at the end of the loader arm), as Ad Hoc has pointed out in the post #29.

Now, if you look at the 3 stablity diagrams in my last post, you will see that Gz=0.7 implies:
- about 10° list for 1.5 meters of gap between the hulls;
- about 8° list for a gap of 2 m
- 5° list for a 3 m gap, which is what Ad Hoc has used in his last post, relying on my wrong data.

So, all in all, I believe you shouldn't adopt less than 2 meters of separation (which means "separation", this time ) between hulls. And 8° is already a considerable heel, as Ad Hoc has already pointed out, so increasing it to 3 meters would be better.

[daiquiri]

Now, I would like to raise another question regarding this project.

This is not some stitch-and-glue DIY sailboat we are talking about. It is a workboat which will be operating in a potentialy dangerous environment (cold water and a surface covered with very heavy, moving logs).
All these people trying to help you are doing it for fun, in their free time. The errors and the approximations (mine, in this case) are a consequence of this.

But what could have happened if I hadn't notice my own error and if you went on with the project according to the previous (wrong) data?

I hope you do realize that if something goes wrong and you make a barge which doesn't satisfy your local authorities' safety requirements, it would be an economical damage for you because you might be fined and forbidden to use it.
Or, if at some point this barge capsizes (with you on board) because the calcs (stability, structural etc.) have been done with ease, you might find yourself in a very big danger Martin.
Or, a wrongly done job could put in danger or injure other persons, create damage to public or private property etc. It becomes a matter of legal liability, and you are absolutely legally unprotected if you base this job on the opinions gathered through this forum.

So my point is: you need a serious project, done, blueprinted and signed by a naval architect or by an engineer, which will be your waranty that everything has been done right.
I'm not talking about these two numbers we have put down here, but about a project involving the boat's stability, structure, hydraulics, safety measures for the crane, for the on-board logs etc.

So, I think you understand now what is the right thing to do, if you want to do it right...

[Ad Hoc]

Daiquiri

Ok, didn't see your caveat when i copied your graphs.

I'll double check your figures. Also fully concur with your comments in #38.

[Ad Hoc]

Martinf

Ok, redone the calc's. Typical old adage "only trust the results you make.."

I took the 2m separation between hulls, as 3m, is probably too much and martin says 2m max.

See attached.

First is GZ curve with hulls 2m apart, and 2tonne on the CL, ie slewed across ready for placing on deck.

Second, same condition, but just lifting the wood at max outreach and height, assuming crane on vessel CL.

The angle is just over 5 degrees. Which, as also noted by beackmo is slightly higher than authorities recommend. However, this needs to be checked by martin, as i noted above with the local authorities what the real criteria would be. (5 degrees feels so much more...so best if you can, reduce this for safety reasons).

The area under the GZ curve is much improved too. Should pass any stab criteria, but to be confirmed by Martin.

How does this stack up agianst yours Daiqiuri?

[Ad Hoc]

Final word.

If your local reg's also confirm that more 5 degree is too much and you can't separate the hulls anymore than 2m, then reduce the SWL of the lift from 2 tonne to 1 tonne. This then gives you a safety margin on an overload too.

[daiquiri]

Originally Posted by Ad Hoc

How does this stack up agianst yours Daiqiuri?

With VCG = 1.36 m you have a 6 degrees list, I have something between 6 and 7 - probably depends on lever arms for various masses involved in the calcs. But the rest of the figures are very similar.

[Ad Hoc]

Daiqiri

Thanks for the validation D (2 heads are better than one)

So, there is the solution(s) martin

No feedback, that is sad.

[daiquiri]

Martin had given me a link to his blog, on which he would log the progress of this enterprise:
http://www.seamule.blogspot.com/
The latest entry is dated august 2009, so I presume there was no progress since then...