Question about "safe working load" of a vang block.

I am re-rigging my main sheet and boom vang and just bought a Garhauer Triple Block. The plan was to use this block as the upper part of the boom vang utilizing the two outside sheaves; the inside sheave would route the main sheet from the traveler forward to the mast.

The block I just purchased is rated at a 2,000 lb. safe working load. This thing is more massive than it appeared online when I ordered it. I chose it based on the size of the large sheave in the lower fiddle block on the vang. I am just wondering if I could have gone with the block with a 1,150 lb. safe working load. The way I am thinking of rigging it the upper vang block will carry some load from the main sheet.

My boat is an #30+.

Here's a picture of the block from Garhauer's website, but I think this is the smaller block since the one I received has a much more robust shackle and swivel.

Can't quite picture how the upper block of the boom vang is going to serve both the mainsheet and the vang.

Can you sketch out your rigging plan?


But for reference, the Harken 75mm double block at the top of my Olson 911SE mainsheet has a SWL of 2426 lbs.

Vang Rigging:

1 – Becket to upper fiddle sheave
2 – Upper fiddle sheave to side triple sheave
3 – Side triple sheave to lower fiddle sheave
4 – Lower fiddle sheave to side triple sheave
5 – Side triple sheave to mast base turning block

This leaves the center triple block sheave free.

Main Rigging:

1 – Fiddle becket to middle single block
2 – Single block to upper fiddle sheave
3 – Upper fiddle sheave to aft single block
4 – Single block to lower fiddle sheave
5 – Lower fiddle sheave to center triple block sheave
6 – Center triple block to gooseneck turning block
7 – Gooseneck turning block to mast base turning block
8 – Mast base turning block to deck organizer to cockpit

Mark,

I'm not sure about your question about the load, though my gut feeling is that you should stick with the very robust triple as you described it and not reduce to a smaller triple.

My Mainsheet is much like yours, though on my bridge deck, not on my coach roof. Therefore, my sheets are fairly accessible to me in the cockpit.

A question I have for you though is about the purchase on your main sheet. I have long pondered increasing my purchase, probably to a 6:1, much like Loren's, described and pictured in other posts. What I will do when I finally spend the $, is use a triple with becket and cam at the bottom and change the forward block on the boom to a double. That should give a 6:1. Any thought of doing that? The only downsides I can are expense and needing a longer Mainsheet.

Currently I have a fiddle block on the traveller and two singles above it on the boom; the aft one with a becket. The single block in the middle currrently functions really as just a turning block to lead the main sheet forward to the gooseneck. That gives me a 3:1 purchase on the main sheet if my math is correct. I believe the new configuration would increase that to 4:1, again if my math is correct. The vang is currently two fiddle blocks giving me 4:1 there; the one on top would be re-purposed in the new setup to the traveller for the main sheet since it has the becket.

Having end-boom sheeting would be ideal as it is a stronger design, but I can't do that. It would also eliminate a lot of the friction I have in turning blocks and deck organizers to lead the lines aft.

This is how it is currently rigged. The main sheet does not connect with the upper fiddle block of the vang, it runs beside it:

Mark,
</SPAN>
Nicely drawn.</SPAN>

Your illustration presents a bit of a challenge for those guys good at figuring purchase, since the fifth leg is both at an angle and part way to the boom’s pivot point.</SPAN>
But that’s for the smart guys to argue over.</SPAN>

The 30-series block is probably a bit over-specced, but the 25-series, with a SWL 1150 lbs, may not be not hefty enough. Plus the 30’s bigger sheaves will result in less friction. So the 30 should work fine.</SPAN>

The real question is why do you want to run your mainsheet down the mast? Did you not like it cleated at the traveller?

Main sheet lead question

House top travelers are in front of the dodger, so the final part of the sheet that leads to a winch or a cleat needs to come back under the dodger to the rear of the cabin top.
Even in sunny climes where boats do not usually have dodgers, it's a long reach to the traveler track area from the cockpit.

(We are just really glad that we have a traveler on a bridge deck, reachable from the helm.)

Loren

Thanks for the clarification Loran,

Missed the bit about the traveller being on the coach roof.

And all that talk about dodgers just confuses me. Thought they a a baseball club.

Loren described my situation exactly; dodger is in the way. In diagram #1 leg 5 probably has little or no bearing on the purchase of the blocks at the traveller but will add some load to the triple block. I just down to the marina so tomorrow I will know if it works or not...

The best laid plans...D'oh!

Well, my big idea didn't work. The angle of the triple block when the vang was under tension was such that the main sheet would rub against the under side of the top of the block. Also when the lower fiddle block of the vang is moved to the toe rail to use the vang as a preventer it causes the triple block to rotate 90 degrees, binding the main sheet. BUT, I have a plan "B"! (Always have a plan "B"...) I will put a new fiddle block with becket on the traveller, a new double block on the middle boom bail and run the main sheet from the double block to the turning block at the mast base as it was done originally. Can't post a drawing now as I am working from my iPhone. Also, I think Garhauer sent me the 40-series triple block instead of the 30-series; the trunnion is larger than the one on my 30-series fiddle blocks and the shackle pin is 3/8" in diameter - ! As Oat Willie would say, "Onward, through the fog!"

Why didn't anyone tell me there was an easier way?

Well, I just found this on Harken's website:



I can accomplish the 4:1 setup on my mainsheet with my existing blocks by just swapping the aft and middle single blocks (that single block next to the fiddle on the boom is no longer there):



I also found this mainsheet load calculator on the Harken site:

http://harken.com/calculators/MainsheetLoading.aspx

With these measurements: E = 13, P = 38.5, V = 20 and D = 5.4 I get a mainsheet load of 1,398 lbs.

Now, I take it that load is assuming a 1:1 purchase. If I have a 4:1 or 5:1 purchase I assume (I know, I know...) the load will be lessened? Take a look at these calculations; they are pretty close to my measurements:

http://www.sailingseadragon.com/Manuals/MainsheetCalculation.pdf

It looks like these calculations are taking into consideration three attachment points and a 4:1 or 6:1 purchase. In my case it seems a block with a 1150 lb SWL would be sufficient. The Schaefer blocks you see on my boom are rated at 1750 SWL.