[Rhodes22-list] Crane question

[Michael D. Weisner]

Last two images didn't fit in the original email

-----Original Message-----
From: Michael D. Weisner <mweisner at ebsmed.com> 
Sent: Monday, April 5, 2021 1:26 AM
To: 'The Rhodes 22 Email List' <rhodes22-list at rhodes22.org>
Subject: RE: [Rhodes22-list] Crane question

Allyn,

My 1981 Rhodes never required a crane because I was twenty something and had a standard mast and main. My second Rhodes, a 1991 with IMF was quite a bit heavier, not to mention that I was forty years older. I decided to build my own mast crane and crutch because I was not happy with Stan's design which required a fixture forward of the mast to affix the crane. It was my choice to affix my crane close to the base of the mast, providing simpler mechanics and no permanent deck fixture.

I read about a design that used a wooden gin pole to raise a mast on a Catalina 22 (see mastraising.pdf attached). I was intrigued but I didn’t care to use wood for the gin pole. I purchased a 2"x2"x6' aluminum box tube for my gin pole. I machined the end to snuggly fit the curve of the front of the mast, added a nylon block with two dowel pins and drilled two holes in the mast, about 6" up the mast. This permitted a stable connection of the gin pole to the mast. I added two thin pieces of aluminum to anchor the gin pole to the mast, secured by the tabernacle mast bolt. The holes for these pieces were slotted to the edge so that the plates could be removed from the tabernacle bolt without removing the bolt. See attached image (Base of mast ...). I added a bidirectional winch and a pair of eyebolts to receive the forward baby stays to actually lift the mast. See attached image (Top of gin pole ...). Additional "helper" lines were added to keep the gin pole upright while setting up. Lines were tied to the side stays to permit "steering" the mast by varying the tension on the lines during raising or lowering, especially during windy days. See attached image (Ready to lift ...). Of course, to make the mechanical effort reasonable, a mast crutch was needed to raise the stern end of the mast. It was constructed out of 2" PVC pipe and fittings with a steel inner pipe for rigidity. The crutch simply straddles the stern while the weight of the mast is transferred to the rear cockpit area (rear of lazarette cover). The stern docklines are attached to the top of the crutch to prevent sideways movement. See the attached image (Mast crutch ...).

Before I tried my first lift, I computed the loads applied to all components, especially the winch line. The design and calculations are presented in the attached file mast_calc_PC.pdf. The loads should be similar to those in your design. The worst stresses are when you start lifting the mast or as you are close to the crutch when lowering. Be sure that the winch line is up to the task and is well secured to the bow deck cleat. The cleat must also be able to take the vertical load, not simply screwed into the deck with wood screws.

The design process is not for the faint of heart but the result is that one person can safely raise or lower the mast in a minute or two. A helper is always recommended in case lines snag or a problem occurs.

Mike
s/v Wind Lass ('91)
Nissequogue River, NY


-----Original Message-----
From: Rhodes22-list <rhodes22-list-bounces at rhodes22.org> On Behalf Of Allyn Baskerville
Sent: Saturday, April 3, 2021 9:22 AM
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Crane question

Thanks for the responses and information, and I’ll work through the calculations today. 

I’ve found some pictures and videos, and the one on YouTube where Peter picked up his boat was very insightful. 
 
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