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A-frame idea

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dmpilc
Master Marine Consultant

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USA
4593 Posts

Initially Posted - 05/25/2011 : 11:27:28

An idea occurred to me while I was trimming the bushes (long overdue) this morning. Has anyone tried lashing or bolting a 2x4 or 1x4 to a wood A-frame say a foot or so from the bottom so that it sticks out several inches on each side and attach eyebolts to it; then attach the forward lowers to the eyebolts? The idea is to extend the forward lowers out to the sides and let them help keep the mast centered.
They would have to be positioned so that they do not take on too much of the load of the mast being raised or become too tight.

DavidP
1975 C-22 SK #5459 "Shadowfax" Fleet 52
PO of 1984 C-25 SK/TR #4142 "Recess"
Percy Priest Yacht Club, Hamilton Creek Marina, Nashville, TN

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DaveR
Master Marine Consultant

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2015 Posts

Response Posted - 05/25/2011 : 11:41:26

Good idea I think David. The only thing making it difficult, tell me if I'm thinking wrong about this, would be that the drop rate would be different from the end of the forestay at the top of the A-frame versus the attachment of the shrouds at the lower end, so they'd start out loose but tighten up towards the end of the drop, kind of negating the help when it's needed most.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 05/25/2011 : 11:53:24

I would be concerned that if your A-frame does not extend the full distance from the deck plate to teh tang on teh bow, that you could wind up lifting the whole weight of teh mast on the lower stays. I would also be concerned with the stays binding and then bending hardware through the rotation of the a-frame. I do think its a good idea though.

I would experiment with strops tied to the eye bolts, or just attached to the a-frame directly and see if you can adjust their length to get the desired effect.

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JohnP
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1520 Posts

Response Posted - 05/25/2011 : 19:48:08

Can you explain the advantage over having only the upper shrouds being used to center the mast when dropping and raising?

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GaryB
Master Marine Consultant

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4303 Posts

Response Posted - 05/25/2011 : 19:59:32

My A-Frame looks just like the one in the Tech Tips under Bear's Abode - Misc. Modifications. The only difference is mine has short aluminum straps that stick up from the attach points at the forward lowers.

I loosen and remove the forward lowers. After installing the A-Frame over the forward lower attach points I attach the forward stays to the aluminum straps. At this point they are very loose and I don't adjust them at all. I then slightly loosen the rear lowers followed by the uppers when I'm ready to drop the mast. The uppers are only loosened enough to allow the mast to ride up over the "hump" as you start to lower it.

In this configuration the uppers and rear lowers help control the side to side movement as the mast is lowered. As it swings back the uppers will continue to loosen as the forward lowers start to tighten slightly. The rear lowers also stay "relatively" tight.

The net result is this keeps the side to side motion of the mast under some form of control. When I lowered and raised the mast the other day the wind was blowing between 15 and 20 directly across the boat. Although I had help in both directions there wasn't any problem keeping the mast under control. It pretty much kept itself under control with slight help guiding it into the mast support.

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glivs
Admiral

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USA
836 Posts

Response Posted - 05/26/2011 : 04:23:07

Based on Gary's design/videos I tied off the forward lowers on to the A-frame last season as a test. Worked well. I do not drop the mast often, but will repeat the process the next time.

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dmpilc
Master Marine Consultant

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4593 Posts

Response Posted - 05/26/2011 : 07:51:39

Another thought: Has anyone tried tying a line to the stanchion bases on each side to form a bridle and securing the forward lowers to the the line so it can slide along the line? Again there may be a tensioning issue. I remember watching a video of the Seaward 26 mast raising system. They had a wire bridle for each side of the boat, attached to the stanchion bases with spring clips, with a stainless ring in the middle positioned so it is in line with the mast pivot pin (like the topping lift bridle for a spinnaker pole). I've thought of having a pair of those made up.
With the 2 rings lined up with the pivot pin, the binding issue should be resolved. Should work as long as the stanchions can handle it.

I just thought of something else. With the double hole chainplates on a C-25, our TR uses the outer holes, which leaves the inner holes available for a 3rd attachment point for the bridles. That would relieve a lot of the tension from the stanchions.

Edited by - dmpilc on 05/26/2011 08:01:16

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 05/26/2011 : 08:43:05

Seriously if you watch Davy J's video there's really not a problem that needs a fix. From what I see and hear (having not done it myself) It's fairly easy and I think Gary B didn't have a sway problem in 20 mph winds.

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Davy J
Master Marine Consultant

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1511 Posts

Response Posted - 05/26/2011 : 08:50:36

I have tangs attached at the base of the a-frame, keeps the mast from swaying:

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GaryB
Master Marine Consultant

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4303 Posts

Response Posted - 05/28/2011 : 17:54:18

Davy,

Seeing your pictures above, I think I made mine based on your layout. These pictures look familiar to me. I thought I had seen it on this site before but couldn't find them when I looked this time. Mine is almost identical except I used a piece of aluminum for the tangs and I bent them slightly so the toggles would line up better.

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Davy J
Master Marine Consultant

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1511 Posts

Response Posted - 05/29/2011 : 04:23:07

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I thought I had seen it on this site before but couldn't find them when I looked this time.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
I posted the photo in a thread a number of years ago, it also comes up in the second video I made. My "tang" is a piece of galvanized strapping, I do not remember where I got it. I think it was just some scrap material I found in the garage.

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