Masthead Block
 

The masthead on my boat does not use built in sheaves, but instead uses blocks attached to holes in the masthead (shown in the photo). Have you guys got any suggestions for blocks? I believe that Garhauer makes a toggle head block for the mast base that may work, but if anyone has setup a masthead like this before, I'd like to know which route you took.

http://photobucket.com/albums/d101/r...ailboat005.jpg

Having a crane at the truck is not that odd in wooden masts. A bit less common in aluminum.

I may prove wrong in the assumptions I make below and I am likely to be answering a question you did not ask, as I can't see anything special in the block brand choice itself.

The counter-sinks on one hole forward and one aft cause me to infer that there's counter-sinks for the other two holes on the other side and space in between what's either two tangs or an upside down square U section. I'd then expect the un-counter-sunk sides to the threaded. This way you can use a flathead ss bolt to hold the blocks (inner holes) and head stay and back stay (outer holes). Add a shackle to the blocks only if you need to create some separation between the blocks and the stays.

G'luck

Ian

Ian

Thanks for the reply. The holes are actually all identical, straight through smooth drilled holes, no threading or countersinks (the forward and aftermost holes had copious amounts of dirt around them when the picture was taken, making it appear to be counter sunk). The markings appearing to be counter sinks are actual the marks left behind from the forestay and backstay fork fittings on the original rig.

My intention is to use toggles on the stays and then attach a double toggle head block to each side (main halyard and topping lift aft and jib halyard and spinnaker halyard forward). I am leaning toward the toggle blocks so I have more weight bearing area as compared to using a U shaped shackle that would only bear on the edges of the holes.

For the stays, I'd use plain jaws, no toggles.

For each block, I'd get a bow shackle whose pin fits the holes nicely and whose jaw clearance is close to the crane's thickness. The blocks pulling just a little side to side on a bow shackle will not create a problem. No need for swivels or toggles here that I can see.

G'luck

Ian

Ian

Thanks for the advice! Why would you choose not to use toggles and instead use plain jaws? Is it strictly a cost issue or are there factors that I am not aware of that make jaws preferable? Thanks again!

Ryan

halyard blocks
 

Ryan,

Using shackles instead of toggles allow the block to articulate from side to side. If the block were on a toggle, and the halyard pulled off to one side, it would chafe against the cheeks. Not a problem so much on the main as it is on either a jib or a spinnaker halyard.

Another point to consider is the use of a swivel. I have found that this can cause the line to twist around itself in a most annoying manner. Using a shackle allows the block to align with the strain, and the swivel is not necessary. Any time you can reduce the complexity of the the gear aloft, its worth a bit of effort.

Make sure that the block is adequately sized for the line, and be generous here, your halyards will thank you. On the other hand, I also like to use a block with a becket for at least one halyard. Two reasons for this, it provides just a little additional insurance for when you have to work aloft. Should the axle fail, the becket will trap the halyard, and this might just prevent that ugly sinking sensation.. The becket gives you someplace to tie stuff when working aloft too. Along these same lines, the block chosen should be the best and most reliable available. And mouse the shackle!

John

Toggles
 

Hi there,
I'm a bit late jumping in here, but it seems that toggleless stays are a very bad idea: fatigue. As for the blocks, you can either use two shackles, or get a block with an upset shackle. In the latter case, the block, in this application, might be crowded in too close to the mast and stay; more likely is the two-shackle configuration, with a short pendant between them.
On most contemporary blocks, a swivel does not complicate matters, because most blocks have a swivel mechanism built-in, which can be disabled if one so chooses. We generally, for instance, disable the swivel on mainsheet boom blocks, because they have parallel runs, and so are vulnerable to spiralling. But a jib halyard block always loads with an angle between the parts, so swiveling might not be a problem.
As for the becket, well, if that sheave were to fail, any backup strength from the becket might be essentially decorative, particularly if the rope forced the remaining block apart. And good blocks require a huge load even to deform; we had one in the shop the other day that had most of a pair of (empty) overalls dragged through it with a come-along providing force. It's a long story, but the point is that the sheave deformed downwards under the wedging load, and would no longer turn, but it didn't break. Harken, by the way.
Finally, while it might be nice to have a place to tie things to, I'd rather not limit halyard hoist to accomplish that.
Fair leads,
Brion Toss

John

With respect to toggles, I was questioning the use of jaws on the stays, not the blocks. I can see advantages of the shackled block, but I am unable to convince myself not to use toggles on the forestay and backstay.

Brion

So you would recommend toggles on the stays as well, correct? Can you describe an "upset shackle" ? I am not familiar with that term. Thanks for the advice!

Ryan

Attempting clarification
 

Hi again,
Toggles on the stays, always toggles on at least the stays that get sails put on them, and not a bad idea on the backstay. Shackles on the blocks, always shackles on the blocks, as these need to articulate even more than the stays in many instances, and in any event don't (or shouldn't) take as much strain as the stays, so don't need toggles.
Clearer?
Fair leads,
Brion Toss