Gin pole force calculations?

[Tomfoolery]

I believe Sumner keeps his pole attached like this.



http://purplesagetradingpost.com/sumner ... ing-2.html

I leave mine attached when trailering; it just sits there, fully rigged and ready to work. It's just going to go back on when I get where I'm going anyway, so why take it off?



I store it in the car (road trip) or garage (home port) so it doesn't bang around when sailing and otherwise get in the way. I would keep it on the boat when sailing if there was the possibility of needing to drop the mast to get under a bridge, but that hasn't been an issue (yet). I store it fully rigged with the line coiled and strapped on. It pins on with a long bolt, and the lower block connects with a captive-pin shackle, and I run the line through the main halyard rope clutch for convenience, but the whole thing only takes a few minutes. And it's only done half the time (per the first paragraph), so on average, it takes a relatively small percentage of the mob/demob time.

As to using PVC, I wouldn't do it. The failure mode is brittle fracture, so it would essentially explode should it let go. Like using cast iron for a crane hook - you could make one strong enough for the intended load, of course, but should it fail, it would be catastrophic and without warning.

If you give me the dimensions of all the locations where the lines terminate, where the gin pole connects, and where on the gin pole the connections are, I can easily give you approximate static forces on all the lines and their terminations, plus the pole compressive or tensile forces (yes, it can see tension with the mast all the way up, depending on how the rigging is run, though that's not likely to govern).

[Sumner]

I believe Sumner keeps his pole attached like this.



http://purplesagetradingpost.com/sumner ... ing-2.html

I probably should reword that page as I think I left it there the 1st trip only as I don't see it in pictures of trips after that. I store it below once the mast is up back in the rear berth (use it for storage). My needs are a little different than most as I don't day or weekend launch so the mast only goes up at the beginning of the trip and down at the end.

I need to calculate the loads on the gin pole and associated lines. Any good links to calculating mechanical static forces at different angles?

I am thinking of designing a system that is permanently installed and quick and easy for a single handler. Mount the heavy clutch winch permanently on the prow (can also use it to pull up the anchor?) (also use it to pull onto the trailer?) (12v electric winch with remote control?). Associated gin pole lines easily permanently installed. Use light weight PVC pipe for the actual pole (is it strong enough? - calculate it). Permanently attach the pole to the mast. Any more ideas?

Your signature says you have a "D". If so just replicate the factory system. It is simple, effective and easy for one person to use. Once you have it down you could have the mast up or down in less than 15 minutes. I think anything that is permanently installed will be in the way of other systems sooner or later. That was the reason I right away quit leaving the jin pole attached as I needed that track to attach the wisker pole while running and couldn't do that with the jin pole there.

If you don't have a local source buy an appropriate length of aluminum tubing from onlinemetals.com ...

https://www.onlinemetals.com/

... where I get all my aluminum. It will be light, last forever and you won't have to worry about the strength.

Just my opinion and good luck,

Sumner

1300 miles to the Bahamas and back -- 2015

The MacGregor 26-S

The Endeavour 37

Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[Tomfoolery]

Your signature says you have a "D". If so just replicate the factory system.

And in furtherance of that, the factory gin pole is 6061 aluminium, 1-1/2" OD x 1/8" wall x 6 ft long. The bottom ends (that constitute the 'fork') are available from BWY, and the SS eye straps and hardware are available at WM and any other marine supplier. The winch used on the M system is a Dutton-Lainson 350 lb brake winch (BRAKE winch, not the cheaper ratcheting 'pulling' winches, like what's used on the trailer).

Or the X system, which uses the same blocks as the main sheet and vang system, and the gin pole moves with the mast.

You can also buy the complete M system from BWY.

And use baby stays. Hardware can be bought from BWY, and the whole kit is also available, at least the type used on the X. The M baby stay system is a little different, but I have no experience with it, so can't comment further.

[warren631]

Tom, my dimensions for calculation: The gin pole that came with the boat is 2 inch aluminum pipe 9 ft long thick wall schedule 80 (1.75 lb/ft). The lines to the winch and mast will be attached to the top end of the pole. The line to the mast will attach 8ft up the mast. The winch will be mounted on the top bow rail. The angle between mast and gin pole should be about 60 degrees so the pole will not go all the way down with the mast fully up. Would 45 degrees be better (less stress)? This is a standard 26D. Not sure the weight of the mast. The gin pole, with winch attached, feels like about 40 lb.

[Tomfoolery]

Warren

I need the X and Y dimension of the winch on the bow rail.

Are you sure you want to use that? I don't know how strong it is, but the mooring cleat(s) are usually what's used on the 26 Classic.