Vang attachment problem

[GreenLake]

As I have mentioned here before, I use a hinged mast sleeve to raise my keel-stepped mast. That means that the place where a vang would normally attach, that is the last 6" of the mast above the deck are wrapped in 1/16" aluminum, and any attachment in that area would have to work with that setup.

Here's a picture from above:

And one from behind:


The bottom of the mast slides freely through the sleeve, once the mast is vertical, so it can be dropped to the keel. That prevents any attachment to the mast itself.

I've raised this issue before in comments on various other posts, but finally I'm tired of not being able to rig a vang, so I'm appealing on the collective wisdom for "constructive" (pun intended) suggestions.

The baseplate and hinge are reasonably sturdy. They might take the load of a vang, but they are anchored on deck. The pull from the vang would potentially raise the deck. Is that an issue? Or am I better off with something that allows the loads to be carried by the mast.

My goal is to not rule out vang sheeting. Even if the angle of the vang is rather shallow, the 20:1 vang setup that is mentioned for that purpose sounds a bit scary... If I assume I could pull with 50# on a vang, that would be almost 1,000# total pull (except that some is lost in friction). Assuming that people find that vangs used for vang sheeting require that much force to adjust when fully loaded.

The majority of that force would pull back on the mast (or parallel to the deck) given the angle, but it would still leave 300-400# of vertical pull. I know the deck can hold that much in crew weight during rigging, but would it be OK to apply that much pull on it under way?

I could drill rather wide holes through mast and sleeve to put a pin through, after rigging, to which to attach a U-bail large enough to clear the wooden block part of my hinge. That would have the load applied to the mast. I hesitate because a) I rather not drill, and b) threading a pin would be fiddly, and would require oversized holes to make it at least reasonably quick.


What do you guys advise?

[gunnerasch]

A thought...if the sail groove in the mast runs all the way to the base of the mast...

You could have a local welder TIG you a piece of SS that fits in the sail groove with 2 legs.. TT (but turned sideways) with the two legs made out of something like 1/2" SS and long enough to stick all the way through the wood with a tiny bit sticking out. You will have to file or machine the mast end of the two legs (arms) small enough to go into the sail slide groove..but thats easy to do and if its TIG welded properly..wont be an issue at all for strength.

Drill and tap the outside ends of the "Legs/arms" with something like 1/4-28 threads for strength. When you slide the mast into the fixture..that TT would go into the sail groove and stay there as you raise and then set the mast. When the mast is up...bolt on a plate of steel (to the legs/arms) with a loop welded to it using those 2 threaded holes and a pair of allen bolts (allen wrench) . You could even make up a pair of handles welded to 2 bolts and simply use the handles to screw them into the threaded holes and snug them up. Then use that loop to attach your vang. You would have to drill through the wood and hinge material in 2 places to set the TT.

Hell..if you put 3 legs/arms (and drilled 3 holes in the wood/hinge) on it..you could use a filister head bolt and a washer on the top bolt (keeping the loop low as possible) to attach it permanantly so it would never come out..it might rattle a little bit.. but never touch the cabin roof....not a biggie. When you slide the mast into the receiver..that TTT would slide into the sail groove, then the mast would be raised up, slide down and seated. If you had the end of the gizmo rounded or pointed a bit, it would go right into that groove with no issues. When the hinge is laying down..I dont think it would touch the cabin roof even with no mast in it. All the forces would be on the sail groove, NOT on the raising fixture so when you set the vang it wouldnt hurt the fixture in the slightest. I can draw you a picture or even make one for you to try out. I figure that it only needs to be at most 4" long with the 2 or 3 legs long enough to go from the mast through the wood and just stick out a tiny bit so there is no clamping to the raising fixture or the wood. To do this does mean you will have to have that sail groove go all the way out the end of the mast, but that should be easy if its not already that way.

I could draw a picture if I didnt make it clear.
Gunner

[Baysailer]

Greenlake,

One suggestion is to put a padeye plate on the cuddy top to use as a vang attachment point. you could reenforce underneath or even put a fixed wire from the bottom padeye bolts to the mast (below deck) or keel to reenforce.

Baysailer

[GreenLake]

One suggestion is to put a padeye plate on the cuddy top to use as a vang attachment point. you could reenforce underneath or even put a fixed wire from the bottom padeye bolts to the mast (below deck) or keel to reenforce.

The circular base plate I have is 1/8" aluminum, and held by 4 SS machine screws with plywood backing and drilled through a raised bit of fiberglass surrounding the mast opening, so locally strong. I'm confident that this is strong enough to distribute any loads so that they are taken up by the deck as a whole.

Do people believe that the deck as a whole is strong enough, or would I need to run a tension wire to the keelson? Possible, but an extra bit of installation.

[swiftsail]

My suggestion is to put a low profile eye strap on front of the mast base and loop spectra around twice( for extra strength) and attach the vang to that. It distributes the load well and puts mostly sheer load on the screws/bolts/pop rivits attachments of the eye strap. The vang also slides nicely from jibe to jibe on the spectra.

Steve

[GreenLake]

Gunner, if I understand your suggestion, it is to change the mast hinge design from a sleeve to something like a row of mushroom buttons that slide in the sail slot. Like a triple sail slug, in effect. That would free up the front of the mast for vang attachments.

Reminds me of the old joke:

An engineer and a mathematician are given a pan of cold water, and told to boil the water. They both put it on the stove, and boil it.

The next day they are given a pan full of warm water, and told to boil the water.

The engineer takes the pan, puts it on the stove, and boils it.

The mathematician takes the pan and empties it, and fills it with cold water.

He then says: "I've now reduced it to a previously solved problem." and walks out.

A variation of this theme that had occurred to me would be to replace the sleeve with one that, instead of an oval cross section, has one that has a bump on the front. Like an inverted sail slot. That would allow me to attach an eye strap to the front of the mast and slide it through the altered sleeve. (A small section on the bottom front would have to be cut away to allow access to the eye strap).

Might be easier to machine and would leave the configuration closer to what is there.

The hinge setup as it stands is rather sensitive to correct alignment etc. I found that small misalignment will cause the mast to not go down or stick partially down. That's rather awkward to deal with, when it happens. It did happen when I rebuilt the hinge (the wood needed to be renewed after many years) and it took some sanding of the mast partners to get it back to operational. Luckily, the fix is permanent; that is, until I touch the hinge design again.

[GreenLake]

My suggestion is to put a low profile eye strap on front of the mast base and loop spectra around twice( for extra strength) and attach the vang to that. It distributes the load well and puts mostly sheer load on the screws/bolts/pop rivets attachments of the eye strap. The vang also slides nicely from jibe to jibe on the spectra.

Steve, that's what I would normally have done, except, if you look here, even a low profile eye-strap won't fit through the sleeve.



That is, unless I go and reconfigure the either the sleeve or the whole contraption so that an eyestrap can either fit or is not encumbered.

The runner up would seem to be to through bolt a pad eye in front of the mast (still using spectra), but I'd rather not find that that flexes the deck too much, let alone rip something... The deck is not exactly weak, you can stand on it, even more than one person, so I've been wondering whether I'm overly concerned.

Just looked up the shear strength of 3/16" pop aluminum pop rivet: 300 lbs. That would give 600 lbs max load on the strap; what does that translate to in terms of safe working load? The value is interesting, because if I try to use a pad eye on deck I'd like to estimate the loads.

[K.C. Walker]

Green Lake

I think I would vote for option A (the pin and bail). I think that would be a straightforward way to attach to the mast. I think if you marked it well while in place so that everything lined up, it wouldn't be too fiddly with just a slightly loose fit. You certainly would not have to worry about a GENEROUSLY oversized hole on your sleeve.

My vang attachment on the mast is to my hinge plate (tabernacle). Though I don't think it's ideal, it seems to be working fine at least for one season. I have a bail attachment on my boom and I have not broken it yet. I think the bail attachment is pretty common. The 20:1 vang set up makes it easier to fine-tune the adjustment. I doubt that I ever pulled with 50 pounds of force, though I've never thought of measuring that. I certainly would not worry about the forces involved if you went with a bail. There are plenty of examples of people using that set up and not having problems.

[swiftsail]

Put the eye strap on the front, Wrap the spectra once around the sleeve through the eye strap and then once around the sleeve outside the eye strap and attach the vang to that part of the loop.

[GreenLake]

I think I would vote for option A (the pin and bail). I think that would be a straightforward way to attach to the mast. I think if you marked it well while in place so that everything lined up, it wouldn't be too fiddly with just a slightly loose fit. You certainly would not have to worry about a GENEROUSLY oversized hole on your sleeve.

I agree, the sleeve is quite tolerant of large holes. They wouldn't have to be oversized relative to the mast by that much, because the alignment is rather well-defined by the oval profile of the mast and sleeve.

My vang attachment on the mast is to my hinge plate (tabernacle). Though I don't think it's ideal, it seems to be working fine at least for one season. I have a bail attachment on my boom and I have not broken it yet. I think the bail attachment is pretty common. The 20:1 vang set up makes it easier to fine-tune the adjustment. I doubt that I ever pulled with 50 pounds of force, though I've never thought of measuring that. I certainly would not worry about the forces involved if you went with a bail. There are plenty of examples of people using that set up and not having problems.

50# would require quite a "yank" and you'd feel in with smaller line. I just now tried it with a 30# weight and a smooth double braid line (1/4") and I had trouble holding it (tended to slipp).

[K.C. Walker]

Okay, I see what Swiftsail is saying. That seems like a really easy way to go! That is, if the sleeve can handle the load while being backed up by the mast.

[GreenLake]

Okay, I see what Swiftsail is saying. That seems like a really easy way to go! That is, if the sleeve can handle the load while being backed up by the mast.

I've been wondering about that. It's 1/16" of aluminum (with a hole pattern punched into it).

It may be that it doesn't have a way to go when the mast is inserted, making all the loads act "in plane" -- except for the actual attachment point of the eye strap. The way to do that might be to screw/rivet that to a base plate and to epoxy that onto the sleeve (would also avoid any rivet heads intruding into the opening).

What do people think, would 2 square inch be enough for such a base plate?

[K.C. Walker]

50# would require quite a "yank" and you'd feel in with smaller line. I just now tried it with a 30# weight and a smooth double braid line (1/4") and I had trouble holding it (tended to slipp).

Yes, I'm using approximately quarter inch line and it definitely does not feel like I'm tugging on it as compared to the mainsheet.

[K.C. Walker]

Maybe you could sleeve your sleeve and attach it to that.

[GreenLake]

50# would require quite a "yank" and you'd feel in with smaller line. I just now tried it with a 30# weight and a smooth double braid line (1/4") and I had trouble holding it (tended to slipp).

Yes, I'm using approximately quarter inch line and it definitely does not feel like I'm tugging on it as compared to the mainsheet.

Good, so assuming that you don't always adjust it at peak loads, perhaps 20-25lbs, which I estimate as more than what you are pulling, would equal the max load. Which would be 400-500 lbs of total tension and ~200 of vertical.

I think that opens up the design options.