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Old 07-20-2015, 09:02 PM   #1
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Boom weight capacity

I have a 13 foot Boston Whaler we are intending to use as our tender/dinghy, I'm going to guess @500lbs, could the boom on a 43 Albin handle that...? Thanks in advance

Jon
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Old 07-20-2015, 09:23 PM   #2
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Does that include a motor? Our 11 foot whaler with a 25 hp 4 stroke weighs upwards of 650 pounds. I doubt the boom will handle 500 pounds. Sounds real risky to me.
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Old 07-20-2015, 09:40 PM   #3
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Old 07-20-2015, 10:14 PM   #4
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Boom weight

Bummer, ok thanks a lot
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Old 07-20-2015, 10:26 PM   #5
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Depends....my Albin 40 could handle 400 easy so I am guessing 500 may not be out of the question.

That is based on an actual lift of nearly 450 pounds without even a decent creak.

When in engineering in the USCG and we needed to rate ancient gear...we would just test to 150% of guestimated load and inspect. If all looked well....it was now stamped and retested annually.

I would do the same but before you do...a little research on all the components and what their common working loads are should shed some light on what it can handle.
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Old 07-21-2015, 07:46 AM   #6
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Doesn't take much to lift 650#, I just lifted a 600# engine from the ground into a boat using a 3" fir pole and a 4" four part tackle, and I'm old and decrepit to boot.
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Old 07-21-2015, 08:18 AM   #7
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The wood is supposedly all in compression and the standing wire rigging generally has a much higher working load than 500 pounds.


So if the wood remains straight and the fittings don't start crushing the wood.....


You are correct..it doesn't take much...just enough (and a little safety margin depending on total range and usage would be nice)...
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Old 07-21-2015, 08:34 AM   #8
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boom

If rigged correctly the pole is in compression along its length so there is no bending moment and the standing part should not be exposed to any leverage factor so there s no multiplication of load . I have no idea what it's capacity would be but a fir 2x4 has a compression limit of 5000#. The capacity of the tackle with Dacron half inch line is 1200#, which is the SWL of the blocks, so for safety sake I put the limit at that. This of course is a single gin pole rig, an angled boom may be less or may be more depending on material. Calculate the weakest component of the entire rig and base your limit on that. There's an excellent little handbook you may find on the internet called "The Rigger's Handbook", very good information if you intend to do any lifting or rigging.
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Old 07-21-2015, 09:59 AM   #9
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Our 2005 130 Sport with 40 horse Merc 2 stroke weighs 1000 lbs soaking wet and loaded with our stuff. It has a console and seat backs that many old Whalers do not. Also has electric start and trim, so the battery may be bigger than a boat without those things. Our stuff includes a couple of anchors and rode (for going to the beach), among sundry lighter weight items. I would advise having it weighed, and having a knowledgeable boat yard assess your particular boom's capacity. Having lifted small RIBS with the booms on various Grand Banks 46 and 49's, I'd be skeptical.
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Old 07-21-2015, 10:06 AM   #10
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Of course the bottom line is....is the mast and boom you have or COULD have the method you would like to use permanently?


If so, then just test it to 150% capacity...if it works...use it...if it fails...build a system that will work.


A little backyard engineering isn't all that big of a deal.


Especially if you aren't lifting live loads or lifting over people or valuable property probably.


As I posted...careful scrutiny during the destructive test often lets you know whether something will work or not.


If worried...see if you can identify a weak link....if not...then put in a commercially made system or find out how to fix what you have.
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Old 07-21-2015, 10:33 AM   #11
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boom

I've lifted over two hundred tons on numerous occasions and I would be a bit hesitant at "destructive testing" when accurate calculations can arrive at a more workable solution. This indeed isn't rocket science, but it is inherently dangerous. Having seen the results of multiple lifting and rigging accidents I can tell you confidently things don't always fall straight down, nor break where expected. If you can afford a commercially available crane, boom or davits that may be the most expedient route, at least you have someone to go back on in the event of failure. I prefer to design and construct my own apparatus simply because I've done it for forty years and enjoy it. Whatever you do, please be careful. As a quick after thought, keep in mind your vessels stability when applying weight alongside.
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Old 07-21-2015, 10:39 AM   #12
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Of course...but 500 pounds a few feet is a bit different than 200 tons.


As I posted in #7...look over the equipment carefully, guestimate the working loads and do a test lift...hardly a big deal with #750 pound test load if done with care thoughout the process.


Believe me after lifting thousands of unknown loads and rigging with a helo...aforethought, care, and a little risk management go a long way.


Even experts with computers can make incorrect assumptions, measurements, observations, etc.... so actual destructive testing an unknown apparatus without sophisticated apparatus to asses condition is easy for the small operation. If something doesn't look right or breaks...then the alternative is build one that is capable....if that's where you were headed all along.


I just hope the OP is still looking as the "just say no" motto didn't work with the drug crisis either...
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Old 07-21-2015, 11:09 AM   #13
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I hope no offense was taken, that was certainly not my intention. And I can see useful ways to utilize potentially destructive tests. The vast majority of my work in the subject has been at sea, where resources and safety take on a critically increased significance. If a clear work area ashore were available and of course the necessary safety precautions, it would be interesting to test the limits of some equipment. Incidentally I was able to be involved in helicopter lifting for the first time a few years ago during the Deepwater Horizon spill, interesting diversion from inspecting cranes, and facilities.
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Old 07-21-2015, 11:09 AM   #14
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Years ago I tracked down the architect for the Krogen 42 and was able to get the load limits on the boom and also for stability purposes the maximum load for the top deck. Don't know if you can do the same with the Albin but it would be worth a try.
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Old 08-05-2015, 10:37 PM   #15
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Quote:
Originally Posted by echo5000 View Post
I have a 13 foot Boston Whaler we are intending to use as our tender/dinghy, I'm going to guess @500lbs, could the boom on a 43 Albin handle that...? Thanks in advance

Jon
As has been pointed out, the load on the boom should be almost entirely compression and under compression its capacity would be a lot higher than any bending load. If your boom is solid teak (like mine) its very strong. Its really the mast that's taking the majority of the load. I suspect that your Whaler with motor and fuel/battery weighs closer to 700. That said, I think the mast/boom on a 43 would be up to the task IF both are in good shape. (there are plenty with rot - especially at the base of the mast)

Ken
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Old 08-06-2015, 07:57 AM   #16
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First calculation I would do is, "How much is this going to cost to fix, if I break it?"
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Old 08-06-2015, 08:01 AM   #17
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It there to use to lift...if it is the gear one wants to use...then let it break under careful use....then replace it in kind with the proper gear. No difference than normal use and breaking of things on a boat.


If a more suitable way can be purchased, and the current mast/boom is wanted for aesthetics...then yes I wouldn't even try.
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Old 08-06-2015, 10:34 AM   #18
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I once watched a Broker demonstrating the operation of a mast boom assembly ona used Manatee. The rig was rated at 600 lbs. but the riveted hinge fitting where the boom meets the mast is notoriously weak after decades of wear. It gave way with about 175 lbs. of dinghy and motor in mid travel to the boat deck. The boom found its way through the aft eisenglass window of the pilothouse and made the Broker look kinda dumb trying to get control as the dinghy plunged motor first off the starboard amidships, somehow still managing to land upright. They later simply welded the hinge fitting back on and was good as new. It's beyond me why such a torque laden fitting would be trusted to tiny rivets. There are simply too many mishaps of unexpected leverage with those designs to trust such vulnerable fasteners. The boom operator is typically standing right by where the boomwould separate and launch into whatever was convenient. Once they are welded, no issues.
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Old 08-21-2015, 02:13 PM   #19
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I think a better term, when lifting 150% of expected working load would be "hopefully non-destructive testing".

Ken
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Old 08-21-2015, 03:13 PM   #20
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I think a better term, when lifting 150% of expected working load would be "hopefully non-destructive testing".

Ken
True...but there's really no viable alternative in cases like this....skyscraper cranes...different story...
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