Boom Crane and aft platform

[Palarran]

I am wondering about two interrelated topics:
Boom Crane -
Several of you have said you like them, several have complained that they are a pain to rig and operate. While having no direct experience with one, but have worked with a lot of leveraged lifting, I can't figure out why they wouldn't be perfect for lifting your rib of the back of the boat. So - why do some work and others not?

Which leads to the second: Seems a boom crane really works if there is a platform between the pontoons. Some cats have them, most don't. What are the advantages and disadvantages? And the direct point on this is that I'm interested in a fp Bahia which from pictures looks like you could custom rig one on the back - any one done something like this?

One step further, anyone ever seen a platform that could hydraulically be lowered into the sea?

[Abaco]

Some Catana 58s have a hydraulic platform for lifting you dingy in a cradle. Very heavy and expensive.

[imagine2frolic]

I can't think of a better place for the dink. A nice platform to lounge on when the dink is in the drink. Mine is grated, so there is no slapping. You can see the simple inexpensive crane still attatched to the halyard.

[Palarran]

I guess I don't see it, sorry. Is it the aluminum pole on the port side? How deep is your platform - 2' 3' ? How wide of a dingy can you put back there?

[delmarrey]

A boom crane it one mounted to a mast, I believe you are asking about a Jib crane (or davit), which are free standing .

Mounting a jib crane has a couple requirements. The deck in which it is being mounted needs to withstand the sideways torque usually requiring a large footprint and large backing plate, space not always available.

Another way, if the space allows, is to install a tube down thru the deck and mounted to the inside of the hull. The longer the more leverage. Also, a flange plate would be needed at the deck passage. This would normally be the stronger of the two.........................._/)

[cchesley]

Our MC 41's have this rig with an extension in the boom and a back platform. The strongest advantage is that the dinghy now sits in chocks rather than hanging and wiggling around while in the davits.

I love this rig and can singlehandedly launch or recover my dinghy in 3 minutes! It helps to have an additional switch aft for the electric halyard winch so that hoisting is a cinch (which MC's have) The aft platform also provides a place to carry fenderboards and jerry jugs snugged up between the dinghy and the cross beam. On a MC, the aft bouyancy is such that it can easily absorb the weight of a dinghy and/fuel jugs without depressing the transoms. The tendency to carry weight aft was well anticipated.

Perhaps the only drawback is that you can't lower the dinghy with the sail up as the boom is req'd. Of course, that's not something you'd do often but in a MOB or rescue situation where you needed super quick access, it wouldn't be like killing way and just dumping your dinghy in the water from davits. Then again, most dinghy stowage solutions don't make this a quick option either.

[imagine2frolic]

Dead center of the dink is a small pole sticking out at 45 degrees. It is still attatched to the halyard. I have never measured the platform, but my guess would be nearly 4 feet. The dink is a 12ft Caribe which is right at 5'6"?

[imagine2frolic]

I just found this pic today of our June trip to the Bahamas. To the right of my guest you can see the crane sticking out . Right underneath the block on the traveler.

[Palarran]

Imagine2frolic - That has to be the easiest system I've seen (or should I say imagined?). Why mess with a extension coming out of the boom. Yours is really just an outrigger.
So that I understand it completely, is there a lifting line to move the pole up and down and another one to actually raise the dingy? So you would raise the dingy up by the platform, raise the outrigger to bring the boat above the chocks, then lower the dingy. And there are stabilizer lines to both sides of the platform - right?

Really nice - I'm laughing at myself for all the stupid ideas I had to construct one. Yours could be done for under a grand easily.

One other question, if constructing one now, would it make sense to have the platform slats removable so if on passage and a storm developed you wouldn't get "pooped" on? Ok, a second question, on passage I would think you would remove your outboard and at least flip the dink over, or do you completely move it inboard of the cockpit?

[sctpc]

You can also use as a swim platform But its still a winch

[Palarran]

sctpc - nice job. Is the platform solid or does it let water flow through? What kind of cat is that? Did the hardtop bimini come standard?

[sctpc]

Fistly its not my idea But this photo shows its up its just so simple and you can build youself.

[imagine2frolic]

There is a 2ft. line that stays on the sheave of the pole. The bottom has a shackle, and the top has a thimble. The shackle clips onto an "O" ring centered on 4 lines in the dink. The main halyard is attatched to the thimble.

If you can see the line just at the man's right knee standing. That is the strbrd line controlling motion from side to side. I once quoted $50.00 for the material, but maybe closer to $100.00 total.

I have never had cause to remove the grates, except for painting. Also there are tiedowns on the rear bulkhead to steady the dink. During hurricanes Jean, and Frances I did tie down the dinks shaft to the grate. The front of the grate slips into a trough. The rear of the grate has a chock both forward, and aft of the rear crossbeam. It is as stable as can be. The rear of the grate has a small bit of lacing to the crossbeam to keep it from raising.

[Zach]

Imagine,

Do I see a stainless shaft running from port to starboard mounted on deck? Is the "boom" only the one tube in the center... or the three vertical ones I see in the picture where she is on a travel lift? Having a hard time visualizing what is moving...

Thanks!

Zach

[imagine2frolic]

When I get to the boat tonight. I will try to remember to take some pics with the crane in mind. I am working in the cockpit tonight anyway. Of course 2 days ago I offered pics of my work benches, and then found a spot in the cockpit that needed immediate attention. I was side tracked..................