Originally Posted by Bud
Thanks for you thoughtfull reply. I owned and operated a commercial fishing vessel in the Gulf of Maine for 25 years so my knowlege is just based on experience not really technical. I did ask my brother who is a marine engineer and his first question was "what do other boats that are rigged the same way lifting safely"
I am looking to lift 420 lbs of dingy. The mast is supported adequately for compresion. the base is hinged and bolted and there is a bulkhead directly underneath it all the way to the hull. The rigging is all new and is all rated to >1200lbs working load. In addition to the wire stays are a set of aluminum pipe stays on opossing side. I am wondering about the side load the boom puts on the mast.
To paraphrase what was stated in another thread: I charge $400 per hour for my time, but I am not a Mechanical engineer, I am only a lowly lawyer.
Your mast and boom are IMHO totally inadequate to lift a load of 420 lbs safely.
You need to go to a commercial marina where there are boats with masts designed for actual lifting and compare their scantlings to your own. Yours is designed to look nice. Mine was a lot like yours when I used it to lift a Sabot from right beside my boat, onto the boat deck. The base failed on that lift, of somewhat less than 50 lbs. I subsequently redesigned the mast and had it completely rebuilt.
The boom was too short, the mast was too short, the stays were in the way, the amount of mechanical advantage way too little.
My redesigned mast was to lift my Laser, 150 lb empty, but since it had a crushed bow, it was usually half full of water, so maybe 300 lb all in. When lifting that much weight, I found I needed a forward stay, so put a line on the bottom of the Radar platform to the handhold on the fwd flybridge seats opposite the side the lift was occupying.
During a lift of the Laser, empty, so only 150 lbs, the mast would bend, even with a stay fastened, so I would be reluctant to use mine for anything as heavy as you plan.
As long as I have been boating, I have yet to see anyone with a decorative mast and boom like yours, lift anything as heavy as my Laser, let alone a 420 lb dinghy.
Friends who have converted work boats have dinghies weighing 700 to 1000 lbs, for which the rigging includes 1/2" cable for each of boom up/down, load up/down, Port sway and Stb sway. Mast height and diameter are dramatically more than yours, as are boom length and diameter.
So rather than polling us here at TF, I would like to know that before you use your present lifting boom and mast for that weight, you would get a proper engineering opinion of its capacity.
Despite my first line, this is just my free opinion, please take it only for what it is costing you.